1
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Shreenidhi PM, Brock DA, McCabe RI, Strassmann JE, Queller DC. Costs of being a diet generalist for the protist predator Dictyostelium discoideum. Proc Natl Acad Sci U S A 2024; 121:e2313203121. [PMID: 38530891 PMCID: PMC10998602 DOI: 10.1073/pnas.2313203121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 02/29/2024] [Indexed: 03/28/2024] Open
Abstract
Consumers range from specialists that feed on few resources to generalists that feed on many. Generalism has the clear advantage of having more resources to exploit, but the costs that limit generalism are less clear. We explore two understudied costs of generalism in a generalist amoeba predator, Dictyostelium discoideum, feeding on naturally co-occurring bacterial prey. Both involve costs of combining prey that are suitable on their own. First, amoebas exhibit a reduction in growth rate when they switched to one species of prey bacteria from another compared to controls that experience only the second prey. The effect was consistent across all six tested species of bacteria. These switching costs typically disappear within a day, indicating adjustment to new prey bacteria. This suggests that these costs are physiological. Second, amoebas usually grow more slowly on mixtures of prey bacteria compared to the expectation based on their growth on single prey. There were clear mixing costs in three of the six tested prey mixtures, and none showed significant mixing benefits. These results support the idea that, although amoebas can consume a variety of prey, they must use partially different methods and thus must pay costs to handle multiple prey, either sequentially or simultaneously.
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Affiliation(s)
- P. M. Shreenidhi
- Department of Biology, Washington University in St. Louis, St. Louis, MO63130
| | - Debra A. Brock
- Department of Biology, Washington University in St. Louis, St. Louis, MO63130
| | - Rachel I. McCabe
- Department of Biology, Washington University in St. Louis, St. Louis, MO63130
| | - Joan E. Strassmann
- Department of Biology, Washington University in St. Louis, St. Louis, MO63130
| | - David C. Queller
- Department of Biology, Washington University in St. Louis, St. Louis, MO63130
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2
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Moncalvillo B, Matthies D. Performance of a parasitic plant and its effects on hosts depends on the interactions between parasite seed family and host species. AOB PLANTS 2023; 15:plac063. [PMID: 36751364 PMCID: PMC9893871 DOI: 10.1093/aobpla/plac063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 12/12/2022] [Indexed: 06/18/2023]
Abstract
Root hemiparasitic plants act as keystone species influencing plant community composition through their differential suppression of host species. Their own performance also strongly depends on interactions with host species. However, little is known about the roles of parasite genetic variation vs. plasticity in these interactions. We grew plants from eight maternal families of the root hemiparasite Rhinanthus alectorolophus with six potential host species (two grasses, two legumes and two forbs) and without a host and measured fitness-related and morphological traits of the parasite, host biomass and overall productivity. Parasite biomass and other traits showed strong plastic variation in response to different host species, but were also affected by parasite maternal family. Parasite seed families responded differently to the hosts, indicating genetic variation that could serve as the basis for adaptation to different host plants. However, there were no negative correlations in the performance of families across different hosts, indicating that R. alectorolophus has plastic generalist genotypes and is not constrained in its use of different host species by trade-offs in performance. Parasite effects on host biomass (which may indicate virulence) and total productivity (host + parasite biomass) depended on the specific combination of parasite family and host species. Mean biomass of hosts with a parasite family and mean biomass of that family tended to be negatively correlated, suggesting selection for maximum resource extraction from the hosts. Specialization of generalist root hemiparasites may be restricted by a lack of trade-offs in performance across hosts, together with strong spatial and temporal variation in host species availability. The genetic variation in the effects on different hosts highlights the importance of genetic diversity of hemiparasites for their effects on plant community structure and productivity and for the success of using them to restore grassland diversity.
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Affiliation(s)
| | - Diethart Matthies
- Plant Ecology, Department of Biology, Philipps-Universität Marburg, Marburg 35043, Germany
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3
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Skoracka A, Laska A, Radwan J, Konczal M, Lewandowski M, Puchalska E, Karpicka‐Ignatowska K, Przychodzka A, Raubic J, Kuczyński L. Effective specialist or jack of all trades? Experimental evolution of a crop pest in fluctuating and stable environments. Evol Appl 2022; 15:1639-1652. [PMID: 36330306 PMCID: PMC9624081 DOI: 10.1111/eva.13360] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 01/30/2022] [Accepted: 02/06/2022] [Indexed: 11/30/2022] Open
Abstract
Understanding pest evolution in agricultural systems is crucial for developing effective and innovative pest control strategies. Types of cultivation, such as crop monocultures versus polycultures or crop rotation, may act as a selective pressure on pests' capability to exploit the host's resources. In this study, we examined the herbivorous mite Aceria tosichella (commonly known as wheat curl mite), a widespread wheat pest, to understand how fluctuating versus stable environments influence its niche breadth and ability to utilize different host plant species. We subjected a wheat-bred mite population to replicated experimental evolution in a single-host environment (either wheat or barley), or in an alternation between these two plant species every three mite generations. Next, we tested the fitness of these evolving populations on wheat, barley, and on two other plant species not encountered during experimental evolution, namely rye and smooth brome. Our results revealed that the niche breadth of A. tosichella evolved in response to the level of environmental variability. The fluctuating environment expanded the niche breadth by increasing the mite's ability to utilize different plant species, including novel ones. Such an environment may thus promote flexible host-use generalist phenotypes. However, the niche expansion resulted in some costs expressed as reduced performances on both wheat and barley as compared to specialists. Stable host environments led to specialized phenotypes. The population that evolved in a constant environment consisting of barley increased its fitness on barley without the cost of utilizing wheat. However, the population evolving on wheat did not significantly increase its fitness on wheat, but decreased its performance on barley. Altogether, our results indicated that, depending on the degree of environmental heterogeneity, agricultural systems create different conditions that influence pests' niche breadth evolution, which may in turn affect the ability of pests to persist in such systems.
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Affiliation(s)
- Anna Skoracka
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
- Center for Advanced TechnologyAdam Mickiewicz UniversityPoznańPoland
| | - Alicja Laska
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Jacek Radwan
- Evolutionary Biology GroupFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Mateusz Konczal
- Evolutionary Biology GroupFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Mariusz Lewandowski
- Section of Applied EntomologyDepartment of Plant ProtectionInstitute of Horticultural SciencesWarsaw University of Life Sciences – SGGWWarsawPoland
| | - Ewa Puchalska
- Section of Applied EntomologyDepartment of Plant ProtectionInstitute of Horticultural SciencesWarsaw University of Life Sciences – SGGWWarsawPoland
| | - Kamila Karpicka‐Ignatowska
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Anna Przychodzka
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Jarosław Raubic
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
| | - Lechosław Kuczyński
- Population Ecology LabFaculty of BiologyInstitute of Environmental BiologyAdam Mickiewicz UniversityPoznańPoland
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4
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Khokhlova IS, van der Mescht L, Warburton EM, Stavtseva NA, Krasnov BR. Adaptation to a novel host and performance trade-off in host-generalist and host-specific insect ectoparasites. INSECT SCIENCE 2022; 29:567-580. [PMID: 34048132 DOI: 10.1111/1744-7917.12929] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 04/01/2021] [Accepted: 04/01/2021] [Indexed: 06/12/2023]
Abstract
We investigated the performance trade-offs of fleas (Siphonaptera) while adapting to a novel host using two host generalists (Xenopsylla conformis and Xenopsylla ramesis) and one host specialist (Parapulex chephrenis) maintained on their principal hosts (Meriones crassus for Xenopsylla and Acomys cahirinus for P. chephrenis). We asked whether, over generations, (i) a host generalist may become a specialist by evolving the ability to exploit a novel host and losing the ability to exploit an original host and (ii) a host specialist can become a generalist by evolving the ability to exploit a novel host without losing the ability to exploit an original host. We established an experimental line of each species on a novel host (Acomys russatus for Xenopsylla and M. crassus for P. chephrenis) and maintained this line on this host during 23 generations. We compared reproductive performance of progenitors of each line and their descendants when they exploited either original or novel host in terms of egg number and size, hatching success, offspring production, and offspring size. We found changes in performance over generations in female offspring size only. Xenopsylla conformis demonstrated a tendency to become a host specialist (increased performance on the novel host with a concomitant decreased performance on the original host), whereas P. chephrenis demonstrated a tendency to become a host generalist (increased performance on the novel host without a concomitant decreased performance on the original host). We conclude that the probability of generalist to specialist transition, and vice versa, is context-dependent and varies between species.
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Affiliation(s)
- Irina S Khokhlova
- Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
| | - Luther van der Mescht
- Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
- Present affiliation and address of Luther van der Mescht: Clinvet International, Uitzich Road, Bainsvlei, 9338 Bloemfontein, Free State, South Africa
| | - Elizabeth M Warburton
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
- Present affiliation and address of Elizabeth M. Warburton: Center for the Ecology of Infectious Diseases, Odum School of Ecology, University of Georgia, 203 D.W. Brooks Dr., Athens, GA, 30602, USA
| | - Nadezhda A Stavtseva
- Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
| | - Boris R Krasnov
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
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5
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Lancaster LT. On the macroecological significance of eco-evolutionary dynamics: the range shift-niche breadth hypothesis. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210013. [PMID: 35067095 PMCID: PMC8784922 DOI: 10.1098/rstb.2021.0013] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Global correlations of range size and niche breadth, and their relationship to latitude, have long intrigued ecologists and biogeographers. Study of these patterns has given rise to a number of hypothesized ecological and evolutionary processes purported to shape biogeographic outcomes, including the climate variability hypothesis, oscillation hypothesis, ecological opportunity, competitive release and taxon cycles. Here, I introduce the alternative range shift-niche breadth hypothesis, which posits that broader niches and larger range sizes are jointly determined under eco-evolutionary processes unique to expanding ranges, which may or may not be adaptive, but which co-shape observed latitudinal gradients in niche breadth and range size during periods of widespread range expansion. I formulate this hypothesis in comparison against previous hypotheses, exploring how each relies on equilibrium versus non-equilibrium evolutionary processes, faces differing issues of definition and scale, and results in alternative predictions for comparative risk and resilience of global ecosystems. Such differences highlight that accurate understanding of process is critical when applying macroecological insight to biodiversity forecasting. Furthermore, past conceptual emphasis on a central role of local adaptation under equilibrium conditions may have obscured a ubiquitous role of non-equilibrium evolutionary processes for generating many important, regional and global macroecological patterns. This article is part of the theme issue 'Species' ranges in the face of changing environments (part I)'.
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Affiliation(s)
- Lesley T Lancaster
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
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6
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Sudta C, Salcido DM, Forister ML, Walla TR, Villamarín-Cortez S, Dyer LA. Jack-of-all-trades paradigm meets long-term data: Generalist herbivores are more widespread and locally less abundant. Ecol Lett 2022; 25:948-957. [PMID: 35106892 DOI: 10.1111/ele.13972] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 12/11/2021] [Accepted: 01/03/2022] [Indexed: 11/28/2022]
Abstract
Insect herbivores are relatively specialized. Why this is so is not clear. We examine assumptions about associations between local abundance and dietary specialization using an 18-year data set of caterpillar-plant interactions in Ecuador. Our data consist of caterpillar-plant associations and include standardized plot-based samples and general collections of caterpillars, allowing for diet breadth and abundance estimates across spatial scales for 1917 morphospecies. We find that more specialized caterpillars are locally more abundant than generalists, consistent with a key component of the 'jack of all trades, master of none' hypothesis. As the diet breadth of species increased, generalists were not as abundant in any one location, but they had broader occupancy across the landscape, which is a pattern that could reflect high plant beta diversity and is consistent with an alternative neutral hypothesis. Our finding that more specialized species can be both rare and common highlights the ecological complexity of specialization.
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Affiliation(s)
- Chanchanok Sudta
- Department of Biology, Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Nevada, USA
| | - Danielle M Salcido
- Department of Biology, Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Nevada, USA
| | - Matthew L Forister
- Department of Biology, Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Nevada, USA
| | - Thomas R Walla
- Department of Biological Science, Colorado Mesa University, Grand Junction, Colorado, USA
| | - Santiago Villamarín-Cortez
- Department of Biology, Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Nevada, USA.,Instituto Nacional de Biodiversidad - INABIO, Quito, Ecuador
| | - Lee A Dyer
- Department of Biology, Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Nevada, USA.,Instituto Nacional de Biodiversidad - INABIO, Quito, Ecuador
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7
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Jermy T, Szentesi Á. Why are there not more herbivorous insect species? ACTA ZOOL ACAD SCI H 2021. [DOI: 10.17109/azh.67.2.119.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Insect species richness is estimated to exceed three million species, of which roughly half is herbivorous. Despite the vast number of species and varied life histories, the proportion of herbivorous species among plant-consuming organisms is lower than it could be due to constraints that impose limits to their diversification. These include ecological factors, such as vague interspecific competition; anatomical and physiological limits, such as neural limits and inability of handling a wide range of plant allelochemicals; phylogenetic constraints, like niche conservatism; and most importantly, a low level of concerted genetic variation necessary to a phyletic conversion. It is suggested that diversification ultimately depends on what we call the intrinsic trend of diversification of the insect genome. In support of the above, we survey the major types of host-specificity, the mechanisms and constraints of host specialization, possible pathways of speciation, and hypotheses concerning insect diversification.
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8
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Peterson DA, Hardy NB, Morse GE, Itioka T, Wei J, Normark BB. Nonadaptive host-use specificity in tropical armored scale insects. Ecol Evol 2020; 10:12910-12919. [PMID: 33304503 PMCID: PMC7713922 DOI: 10.1002/ece3.6867] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 08/14/2020] [Accepted: 09/08/2020] [Indexed: 01/05/2023] Open
Abstract
Most herbivorous insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored scale insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored scale insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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Affiliation(s)
- Daniel A. Peterson
- Department of Biology and Graduate Program in Organismic and Evolutionary BiologyUniversity of MassachusettsAmherstMAUSA
| | - Nate B. Hardy
- Department of Entomology and Plant PathologyAuburn UniversityAuburnALUSA
| | | | - Takao Itioka
- Graduate School of Human and Environmental StudiesKyoto UniversityKyotoJapan
| | - Jiufeng Wei
- College of AgricultureShanxi Agricultural UniversityTaiguChina
| | - Benjamin B. Normark
- Department of Biology and Graduate Program in Organismic and Evolutionary BiologyUniversity of MassachusettsAmherstMAUSA
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9
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Hardy NB, Kaczvinsky C, Bird G, Normark BB. What We Don't Know About Diet-Breadth Evolution in Herbivorous Insects. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2020. [DOI: 10.1146/annurev-ecolsys-011720-023322] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Half a million species of herbivorous insects have been described. Most of them are diet specialists, using only a few plant species as hosts. Biologists suspect that their specificity is key to their diversity. But why do herbivorous insects tend to be diet specialists? In this review, we catalog a broad range of explanations. We review the evidence for each and suggest lines of research to obtain the evidence we lack. We then draw attention to a second major question, namely how changes in diet breadth affect the rest of a species’ biology. In particular, we know little about how changes in diet breadth feed back on genetic architecture, the population genetic environment, and other aspects of a species’ ecology. Knowing more about how generalists and specialists differ should go a long way toward sorting out potential explanations of specificity, and yield a deeper understanding of herbivorous insect diversity.
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Affiliation(s)
- Nate B. Hardy
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama 36849, USA
| | - Chloe Kaczvinsky
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama 36849, USA
| | - Gwendolyn Bird
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama 36849, USA
| | - Benjamin B. Normark
- Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
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10
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Coexistence of nestedness and modularity in host-pathogen infection networks. Nat Ecol Evol 2020; 4:568-577. [PMID: 32152533 DOI: 10.1038/s41559-020-1130-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 01/28/2020] [Indexed: 01/08/2023]
Abstract
The long-term coevolution of hosts and pathogens in their environment forms a complex web of multi-scale interactions. Understanding how environmental heterogeneity affects the structure of host-pathogen networks is a prerequisite for predicting disease dynamics and emergence. Although nestedness is common in ecological networks, and theory suggests that nested ecosystems are less prone to dynamic instability, why nestedness varies in time and space is not fully understood. Many studies have been limited by a focus on single habitats and the absence of a link between spatial variation and structural heterogeneity such as nestedness and modularity. Here we propose a neutral model for the evolution of host-pathogen networks in multiple habitats. In contrast to previous studies, our study proposes that local modularity can coexist with global nestedness, and shows that real ecosystems are found in a continuum between nested-modular and nested networks driven by intraspecific competition. Nestedness depends on neutral mechanisms of community assembly, whereas modularity is contingent on local adaptation and competition. The structural pattern may change spatially and temporally but remains stable over evolutionary timescales. We validate our theoretical predictions with a longitudinal study of plant-virus interactions in a heterogeneous agricultural landscape.
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11
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Freedman MG, Jason C, Ramírez SR, Strauss SY. Host plant adaptation during contemporary range expansion in the monarch butterfly. Evolution 2020; 74:377-391. [DOI: 10.1111/evo.13914] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/11/2019] [Accepted: 12/08/2019] [Indexed: 01/02/2023]
Affiliation(s)
- Micah G. Freedman
- Center for Population Biology University of California, Davis Davis California 95616
- Department of Evolution and Ecology University of California, Davis Davis California
| | - Christopher Jason
- Department of Evolution and Ecology University of California, Davis Davis California
- School of Biological Sciences Washington State University Vancouver Washington 98686
| | - Santiago R. Ramírez
- Center for Population Biology University of California, Davis Davis California 95616
- Department of Evolution and Ecology University of California, Davis Davis California
| | - Sharon Y. Strauss
- Center for Population Biology University of California, Davis Davis California 95616
- Department of Evolution and Ecology University of California, Davis Davis California
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12
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Gene Expression and Diet Breadth in Plant-Feeding Insects: Summarizing Trends. Trends Ecol Evol 2019; 35:259-277. [PMID: 31791830 DOI: 10.1016/j.tree.2019.10.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 10/18/2019] [Accepted: 10/29/2019] [Indexed: 11/20/2022]
Abstract
Transcriptomic studies lend insights into the role of transcriptional plasticity in adaptation and specialization. Recently, there has been growing interest in understanding the relationship between variation in herbivorous insect gene expression and the evolution of diet breadth. We review the studies that have emerged on insect gene expression and host plant use, and outline the questions and approaches in the field. Many candidate genes underlying herbivory and specialization have been identified, and a few key studies demonstrate increased transcriptional plasticity associated with generalist compared with specialist species. Addressing the roles that transcriptional variation plays in insect diet breadth will have important implications for our understanding of the evolution of specialization and the genetic and environmental factors that govern insect-plant interactions.
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13
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Mayrand P, Filotas É, Wittische J, James PMA. The role of dispersal, selection, and timing of sampling on the false discovery rate of loci under selection during geographic range expansion. Genome 2019; 62:715-727. [PMID: 31344331 DOI: 10.1139/gen-2019-0004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Identifying adaptive loci is important to understand the evolutionary potential of species undergoing range expansion. However, in expanding populations, spatial demographic processes such as allele surfing can create spatial patterns of neutral genetic variation that appear similar to those generated through adaptive processes. As a result, the false discovery rate of adaptive loci may be inflated in landscape genomic analyses. Here, we take a simulation modelling approach to investigate how range expansion affects our ability to correctly distinguish between neutral and adaptive genetic variation, using the mountain pine beetle outbreak system as a motivating example. We simulated the demographic and population genetic dynamics of populations undergoing range expansion using an individual-based genetic model CDMetaPOP. We investigated how the false discovery rate of adaptive loci is affected by (i) dispersal capacity, (ii) timing of sampling, and (iii) the strength of selection on an adaptive reference locus. We found that a combination of weak dispersal, weak selection, and early sampling presents the greatest risk of misidentifying loci under selection. Expanding populations present unique challenges to the reliable identification of adaptive loci. We demonstrate that there is a need for further methodological development to account for directional demographic processes in landscape genomics.
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Affiliation(s)
- Paul Mayrand
- Université de Montréal, Département de sciences biologiques, CP 6128 Succursale Centre-Ville Montréal, QC H3C 3J7, Canada
| | - Élise Filotas
- TÉLUQ (Université du Québec), Département Science et Technologie, 5800 rue Saint-Denis, Montréal, QC H2S 3L5, Canada
| | - Julian Wittische
- Université de Montréal, Département de sciences biologiques, CP 6128 Succursale Centre-Ville Montréal, QC H3C 3J7, Canada
| | - Patrick M A James
- Université de Montréal, Département de sciences biologiques, CP 6128 Succursale Centre-Ville Montréal, QC H3C 3J7, Canada
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14
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Gamberale-Stille G, Schäpers A, Janz N, Nylin S. Selective attention by priming in host search behavior of 2 generalist butterflies. Behav Ecol 2018. [DOI: 10.1093/beheco/ary146] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Affiliation(s)
| | | | - Niklas Janz
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | - Sören Nylin
- Department of Zoology, Stockholm University, Stockholm, Sweden
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15
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Vidal MC, Murphy SM. Quantitative measure of fitness in tri-trophic interactions and its influence on diet breadth of insect herbivores. Ecology 2018; 99:2681-2691. [PMID: 30289561 DOI: 10.1002/ecy.2527] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 09/03/2018] [Accepted: 09/18/2018] [Indexed: 11/12/2022]
Abstract
Herbivore-plant interactions should be studied using a tri-trophic approach, but we lack a quantitative measure of the combined effect of top-down and bottom-up forces on herbivore fitness. We propose the combination of the bi-trophic fitness slopes as a tri-trophic fitness measure. We use the relationship between fitness associated with top-down and bottom-up forces and the frequency of host plant use to calculate the top-down and bottom-up fitness slopes, which we then combine to obtain three possible directions of tri-trophic slopes. A positive tri-trophic slope indicates that herbivores have overall greater tri-trophic fitness on the more frequently used hosts. A null tri-trophic fitness slope indicates that herbivores have similar fitness on all host plants. A negative tri-trophic slope indicates that herbivores have generally lower fitness on the more frequently used hosts. We tested the explanation power of our method using data from the literature that tested herbivore host shifts and experimentally using a generalist herbivore with variable diet breadth across populations. We found that in host shifts, herbivores have higher tri-trophic fitness on the novel host, while in generalist populations, herbivores use most frequently the best host available. We present applications in other research areas and consider the limitations of our approach. Our approach is a first step towards a comprehensive model of multiple selective forces acting on the evolution of interactions.
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Affiliation(s)
- Mayra C Vidal
- Department of Biological Sciences, University of Denver, Boettcher West 302, 2050 E. Iliff Avenue Denver, Colorado, 80208, USA
| | - Shannon M Murphy
- Department of Biological Sciences, University of Denver, Boettcher West 302, 2050 E. Iliff Avenue Denver, Colorado, 80208, USA
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Laukkanen L, Kalske A, Muola A, Leimu R, Mutikainen P. Genetic drift precluded adaptation of an insect seed predator to a novel host plant in a long-term selection experiment. PLoS One 2018; 13:e0198869. [PMID: 29894503 PMCID: PMC5997315 DOI: 10.1371/journal.pone.0198869] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 05/25/2018] [Indexed: 11/18/2022] Open
Abstract
Host specialization is considered a primary driver of the enormous diversity of herbivorous insects. Trade-offs in host use are hypothesized to promote this specialization, but they have mostly been studied in generalist herbivores. We conducted a multi-generation selection experiment to examine the adaptation of the specialist seed-feeding bug, Lygaeus equestris, to three novel host plants (Helianthus annuus, Verbascum thapsus and Centaurea phrygia) and to test whether trade-offs promote specialization. During the selection experiment, body size of L. equestris increased more on the novel host plant H. annuus compared to the primary host plant, Vincetoxicum hirundinaria, but this effect was not observed in other fitness related traits. In addition to selection, genetic drift caused variation among the experimental herbivore populations in their ability to exploit the host plants. Microsatellite data indicated that the level of within-population genetic variation decreased and population differentiation increased more in the selection line feeding on H. annuus compared to V. hirundinaria. We found a negative correlation between genetic differentiation and heterozygosity at the end of the experiment, suggesting that differentiation was significantly affected by genetic drift. We did not find fitness trade-offs between L. equestris feeding on the four hosts. Thus, trade-offs do not seem to promote specialization in L. equestris. Our results suggest that this insect herbivore is not likely to adapt to a novel host species in a time-scale of 20 generations despite sufficient genetic variation and that genetic drift disrupted the response to selection.
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Affiliation(s)
- Liisa Laukkanen
- Section of Ecology, Department of Biology, University of Turku, Turku, Finland
| | - Aino Kalske
- Section of Ecology, Department of Biology, University of Turku, Turku, Finland
- * E-mail:
| | - Anne Muola
- Section of Ecology, Department of Biology, University of Turku, Turku, Finland
- Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Roosa Leimu
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Pia Mutikainen
- Institute of Integrative Biology, ETH-Zürich, ETH-Zentrum, Zürich, Switzerland
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17
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Chen KW, Chen Y. Slow-growth high-mortality: A meta-analysis for insects. INSECT SCIENCE 2018; 25:337-351. [PMID: 27604698 DOI: 10.1111/1744-7917.12399] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 08/09/2016] [Accepted: 08/31/2016] [Indexed: 06/06/2023]
Abstract
The slow growth-high mortality hypothesis (SG-HG) predicts that slower growing herbivores suffer greater mortality due to a prolonged window of vulnerability. Given diverse plant-herbivore-natural enemy systems resulting from different feeding ecologies of herbivores and natural enemies, this hypothesis might not always be applicable to all systems. This is evidenced by mixed support from empirical data. In this study, a meta-analysis of the SG-HM hypothesis for insects was conducted, aiming to find conditions that favor or reject SG-HM. The analysis revealed significant within- and between-group heterogeneity for almost all explanatory variables and overall did not support SG-HM. In this analysis, SG-HM was supported when any of the following 5 conditions was met: (1) host food consisted of artificial diet; (2) herbivore growth was measured as larval mass; (3) herbivores were generalists; (4) no or multiple species of natural enemies were involved in the study; and (5) parasitoids (i.e., parasitic insects) involved in the study were gregarious. SG-HM was rejected when any of the following 5 conditions was met: (1) herbivores were from the order Hymentoptera; (2) parasitoids from more than 1 order caused herbivore mortality; (2) parasitoids were specialists; (3) parasitoids were solitary; (4) parasitoids were idiobionts or koinobionts; and (5) single species of natural enemy caused mortality of specialist herbivores. All known studies investigated herbivore mortality for a short period of their life cycle. Researchers are encouraged to monitor herbivore mortality during the entire window of susceptibility or life cycle using life tables. Studies involving multiple mortality factors (i.e., both biotic and abiotic) or multiple natural enemy species are also encouraged since herbivores in nature face a multitude of risks during the entire life cycle. More comprehensive studies may increase our understanding of factors influencing the relationships between herbivore growth and mortality.
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Affiliation(s)
- Ke-Wei Chen
- College of Agriculture, South China Agricultural University, Guangzhou, China
| | - Yigen Chen
- Department of Entomology and Nematology, University of California, One Shields Avenue, Davis, California, USA
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18
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Nylin S, Agosta S, Bensch S, Boeger WA, Braga MP, Brooks DR, Forister ML, Hambäck PA, Hoberg EP, Nyman T, Schäpers A, Stigall AL, Wheat CW, Österling M, Janz N. Embracing Colonizations: A New Paradigm for Species Association Dynamics. Trends Ecol Evol 2018; 33:4-14. [DOI: 10.1016/j.tree.2017.10.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 01/30/2023]
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Vidal MC, Murphy SM. Bottom‐up vs. top‐down effects on terrestrial insect herbivores: a meta‐analysis. Ecol Lett 2017; 21:138-150. [DOI: 10.1111/ele.12874] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/03/2017] [Accepted: 10/04/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Mayra C. Vidal
- Department of Biological Sciences University of Denver Denver CO USA
| | - Shannon M. Murphy
- Department of Biological Sciences University of Denver Denver CO USA
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20
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Abstract
Variation in diet breadth among organisms is a pervasive feature of the natural world that has resisted general explanation. In particular, trade-offs in the ability to use one resource at the expense of another have been expected but rarely detected. We explore a spatial model for the evolution of specialization, motivated by studies of plant-feeding insects. The model is neutral with respect to the causes and consequences of diet breadth: the number of hosts utilized is not constrained by trade-offs, and specialization or generalization does not confer a direct advantage with respect to the persistence of populations or the probability of diversification. We find that diet breadth evolves in ways that resemble reports from natural communities. Simulated communities are dominated by specialized species, with a predictable but less species-rich component of generalized taxa. These results raise the possibility that specialization might be a consequence of stochastic diversification dynamics acting on spatially segregated consumer-resource associations rather than a trait either favored or constrained directly by natural selection. Finally, our model generates hypotheses for global patterns of herbivore diet breadth, including a positive effect of host richness and a negative effect of evenness in host plant abundance on the number of specialized taxa.
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21
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Guzman-Valencia S, Santillán-Galicia MT, Guzmán-Franco AW, Vega-Muñoz R. Differential Host Plant-Associated Genetic Variation Between Sympatric Mite Species of the Genus Oligonychus (Acari: Tetranychidae). ENVIRONMENTAL ENTOMOLOGY 2017; 46:274-283. [PMID: 28087579 DOI: 10.1093/ee/nvw166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Indexed: 06/06/2023]
Abstract
Adaptation to different host plants can lead to host-associated differentiation (HAD). The mites Oligonychus perseae and Oligonychus punicae have a broad range of host plants, but, to date, records of them coexisting sympatrically had only been reported on avocado. However, our field observations showed both species coexisting on host plants other than avocado. The lack of previous records of these mites on the host plants studied here suggests only recent divergence to new host plant species. Previous studies showed that O. punicae had a limited migration capacity compared with O. perseae, suggesting that O. punicae is more likely to develop a close host plant relationship leading to HAD. Adults of both species were collected from trees hosting both mite species. Three genera of host plants considered were Persea, Salix, and Alnus; two species within one genus were Alnus jorullensis and Alnus acuminata; and three varieties within one species were Persea americana var. Fuerte, var. Hass, and var. Criollo, a noncommercial variety. Using sequence data from a segment of the mitochondrial cytochrome oxidase subunit I, the phylogenetic relationships and genetic population structure of both mite species in relation to the host plant were determined. Oligonychus perseae populations showed a significant population structure in relation to host plant at the species and genus level, but there was no effect of variety. In contrast, host plant explained none of the genetic variation among O. punicae populations. The potential role of coexistence mechanisms in the contrasting genetic population structure of both mite species is discussed.
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Affiliation(s)
- Stephanie Guzman-Valencia
- Posgrado en Fitosanidad-Entomología y Acarología, Colegio de Postgraduados, Km 36.5 Carretera México-Texcoco, Montecillo, Texcoco, Edo. de México 56230, México (; ; )
| | - Ma Teresa Santillán-Galicia
- Posgrado en Fitosanidad-Entomología y Acarología, Colegio de Postgraduados, Km 36.5 Carretera México-Texcoco, Montecillo, Texcoco, Edo. de México 56230, México (; ; )
| | - Ariel W Guzmán-Franco
- Posgrado en Fitosanidad-Entomología y Acarología, Colegio de Postgraduados, Km 36.5 Carretera México-Texcoco, Montecillo, Texcoco, Edo. de México 56230, México (; ; )
| | - Ricardo Vega-Muñoz
- Posgrado en Botánica, Colegio de Postgraduados, Km 36.5 Carretera México-Texcoco, Montecillo, Texcoco, Edo. de México 56230, México
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22
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Agosta SJ, Hulshof CM, Staats EG. Organismal responses to habitat change: herbivore performance, climate and leaf traits in regenerating tropical dry forests. J Anim Ecol 2017; 86:590-604. [PMID: 28146325 DOI: 10.1111/1365-2656.12647] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Accepted: 01/13/2017] [Indexed: 11/28/2022]
Affiliation(s)
- Salvatore J. Agosta
- Center for Environmental Studies Virginia Commonwealth University Richmond VA 23284‐9067 USA
- Department of Biology Virginia Commonwealth University Richmond VA 23284‐9067 USA
| | | | - Ethan G. Staats
- Department of Biology Virginia Commonwealth University Richmond VA 23284‐9067 USA
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23
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Vertacnik KL, Linnen CR. Evolutionary genetics of host shifts in herbivorous insects: insights from the age of genomics. Ann N Y Acad Sci 2017; 1389:186-212. [DOI: 10.1111/nyas.13311] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 12/16/2016] [Accepted: 12/22/2016] [Indexed: 12/25/2022]
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24
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Landscape structure and agricultural intensification are weak predictors of host range and parasitism rate of cereal aphids. Ecol Res 2016. [DOI: 10.1007/s11284-016-1419-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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25
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Líznarová E, Pekár S. Metabolic specialisation on preferred prey and constraints in the utilisation of alternative prey in an ant-eating spider. ZOOLOGY 2016; 119:464-470. [DOI: 10.1016/j.zool.2016.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/11/2016] [Accepted: 04/25/2016] [Indexed: 11/28/2022]
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26
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Clarke AR. Why so many polyphagous fruit flies (Diptera: Tephritidae)? A further contribution to the ‘generalism’ debate. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12880] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anthony R Clarke
- School of Earth, Environment and Biological Sciences; Queensland University of Technology (QUT); Brisbane Qld 4001 Australia
- Plant Biosecurity Cooperative Research Centre; LPO Box 5012 Bruce ACT 2617 Australia
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27
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Hardy NB, Peterson DA, Normark BB. Nonadaptive radiation: Pervasive diet specialization by drift in scale insects? Evolution 2016; 70:2421-2428. [DOI: 10.1111/evo.13036] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 07/29/2016] [Accepted: 07/30/2016] [Indexed: 02/06/2023]
Affiliation(s)
- Nate B. Hardy
- Department of Entomology and Plant Pathology, 301 Funchess Hall Auburn University Auburn Alabama 36849
| | - Daniel A. Peterson
- Graduate Program in Organismic & Evolutionary Biology, Department of Biology University of Massachusetts Amherst Massachusetts 01003
| | - Benjamin B. Normark
- Graduate Program in Organismic & Evolutionary Biology, Department of Biology University of Massachusetts Amherst Massachusetts 01003
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28
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Hardy NB, Peterson DA, Normark BB. Scale insect host ranges are broader in the tropics. Biol Lett 2015; 11:20150924. [PMID: 26701757 PMCID: PMC4707704 DOI: 10.1098/rsbl.2015.0924] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 11/29/2015] [Indexed: 12/13/2022] Open
Abstract
The specificity of the interactions between plants and their consumers varies considerably. The evolutionary and ecological factors underlying this variation are unclear. Several potential explanatory factors vary with latitude, for example plant species richness and the intensity of herbivory. Here, we use comparative phylogenetic methods to test the effect of latitude on host range in scale insects. We find that, on average, scale insects that occur in lower latitudes are more polyphagous. This result is at odds with the general pattern of greater host-plant specificity of insects in the tropics. We propose that this disparity reflects a high cost for host specificity in scale insects, stemming from unusual aspects of scale insect life history, for example, passive wind-driven dispersal. More broadly, the strong evidence for pervasive effects of geography on host range across insect groups stands in stark contrast to the weak evidence for constraints on host range due to genetic trade-offs.
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Affiliation(s)
- Nate B Hardy
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, USA
| | - Daniel A Peterson
- Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Benjamin B Normark
- Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
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29
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Hardy NB, Otto SP. Specialization and generalization in the diversification of phytophagous insects: tests of the musical chairs and oscillation hypotheses. Proc Biol Sci 2015; 281:rspb.2013.2960. [PMID: 25274368 DOI: 10.1098/rspb.2013.2960] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Evolutionary biologists have often assumed that ecological generalism comes at the expense of less intense exploitation of specific resources and that this trade-off will promote the evolution of ecologically specialized daughter species. Using a phylogenetic comparative approach with butterflies as a model system, we test hypotheses that incorporate changes in niche breadth and location into explanations of the taxonomic diversification of insect herbivores. Specifically, we compare the oscillation hypothesis, where speciation is driven by host-plant generalists giving rise to specialist daughter species, to the musical chairs hypothesis, where speciation is driven by host-plant switching, without changes in niche breadth. Contrary to the predictions of the oscillation hypothesis, we recover a negative relationship between host-plant breadth and diversification rate and find that changes in host breadth are seldom coupled to speciation events. By contrast, we present evidence for a positive relationship between rates of host switching and butterfly diversification, consonant with the musical chairs hypothesis. These results suggest that the costs of trophic generalism in plant-feeding insects may have been overvalued and that transitions from generalists to ecological specialists may not be an important driver of speciation in general.
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Affiliation(s)
- Nate B Hardy
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, USA
| | - Sarah P Otto
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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30
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Malcicka M, Agosta SJ, Harvey JA. Multi level ecological fitting: indirect life cycles are not a barrier to host switching and invasion. GLOBAL CHANGE BIOLOGY 2015; 21:3210-8. [PMID: 25778909 DOI: 10.1111/gcb.12928] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 02/23/2015] [Accepted: 03/11/2015] [Indexed: 05/03/2023]
Abstract
Many invasive species are able to escape from coevolved enemies and thus enjoy a competitive advantage over native species. However, during the invasion phase, non-native species must overcome many ecological and/or physiological hurdles before they become established and spread in their new habitats. This may explain why most introduced species either fail to establish or remain as rare interstitials in their new ranges. Studies focusing on invasive species have been based on plants or animals where establishment requires the possession of preadapted traits from their native ranges that enables them to establish and spread in their new habitats. The possession of preadapted traits that facilitate the exploitation of novel resources or to colonize novel habitats is known as 'ecological fitting'. Some species have evolved traits and life histories that reflect highly intimate associations with very specific types of habitats or niches. For these species, their phenological windows are narrow, and thus the ability to colonize non-native habitats requires that a number of conditions need to be met in accordance with their more specialized life histories. Some of the strongest examples of more complex ecological fitting involve invasive parasites that require different animal hosts to complete their life cycles. For instance, the giant liver fluke, Fascioloides magna, is a major parasite of several species of ungulates in North America. The species exhibits a life cycle whereby newly hatched larvae must find suitable intermediate hosts (freshwater snails) and mature larvae, definitive hosts (ungulates). Intermediate and definitive host ranges of F. magna in its native range are low in number, yet this parasite has been successfully introduced into Europe where it has become a parasite of native European snails and deer. We discuss how the ability of these parasites to overcome multiple ecophysiological barriers represents an excellent example of 'multiple-level ecological fitting'.
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Affiliation(s)
- Miriama Malcicka
- Section Animal Ecology, Department of Ecological Sciences, VU University Amsterdam, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands
| | - Salvatore J Agosta
- Center for Environmental Studies and Department of Biology, Virginia Commonwealth University, 23284, Richmond, VA, USA
| | - Jeffrey A Harvey
- Section Animal Ecology, Department of Ecological Sciences, VU University Amsterdam, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands
- Department of Terrestrial Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6700 EH, Wageningen, The Netherlands
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31
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Messina FJ, Durham SL. Loss of adaptation following reversion suggests trade-offs in host use by a seed beetle. J Evol Biol 2015. [DOI: 10.1111/jeb.12704] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- F. J. Messina
- Department of Biology; Utah State University; Logan UT USA
| | - S. L. Durham
- Ecology Center; Utah State University; Logan UT USA
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32
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Gompert Z, Jahner JP, Scholl CF, Wilson JS, Lucas LK, Soria-Carrasco V, Fordyce JA, Nice CC, Buerkle CA, Forister ML. The evolution of novel host use is unlikely to be constrained by trade-offs or a lack of genetic variation. Mol Ecol 2015; 24:2777-93. [DOI: 10.1111/mec.13199] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 04/07/2015] [Accepted: 04/09/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Zachariah Gompert
- Department of Biology; Utah State University; 5305 Old Main Hill Logan UT 84322-5305 USA
| | | | | | - Joseph S. Wilson
- Department of Biology; University of Nevada; Reno NV 89557 USA
- Department of Biology; Utah State University; Tooele UT 84074 USA
| | - Lauren K. Lucas
- Department of Biology; Utah State University; 5305 Old Main Hill Logan UT 84322-5305 USA
- Department of Biology; Texas State University; San Marcos TX 78666 USA
| | - Victor Soria-Carrasco
- Department of Animal and Plant Sciences; University of Sheffield; Sheffield S10 2TN UK
| | - James A. Fordyce
- Department of Ecology & Evolutionary Biology; University of Tennessee; Knoxville TN 37996 USA
| | - Chris C. Nice
- Department of Biology; Texas State University; San Marcos TX 78666 USA
| | - C. Alex Buerkle
- Department of Botany and Program in Ecology; University of Wyoming; Laramie WY 82071 USA
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33
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Hoberg EP, Brooks DR. Evolution in action: climate change, biodiversity dynamics and emerging infectious disease. Philos Trans R Soc Lond B Biol Sci 2015; 370:20130553. [PMID: 25688014 PMCID: PMC4342959 DOI: 10.1098/rstb.2013.0553] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Climatological variation and ecological perturbation have been pervasive drivers of faunal assembly, structure and diversification for parasites and pathogens through recurrent events of geographical and host colonization at varying spatial and temporal scales of Earth history. Episodic shifts in climate and environmental settings, in conjunction with ecological mechanisms and host switching, are often critical determinants of parasite diversification, a view counter to more than a century of coevolutionary thinking about the nature of complex host-parasite assemblages. Parasites are resource specialists with restricted host ranges, yet shifts onto relatively unrelated hosts are common during phylogenetic diversification of parasite lineages and directly observable in real time. The emerging Stockholm Paradigm resolves this paradox: Ecological Fitting (EF)--phenotypic flexibility and phylogenetic conservatism in traits related to resource use, most notably host preference--provides many opportunities for rapid host switching in changing environments, without the evolution of novel host-utilization capabilities. Host shifts via EF fuel the expansion phase of the Oscillation Hypothesis of host range and speciation and, more generally, the generation of novel combinations of interacting species within the Geographic Mosaic Theory of Coevolution. In synergy, an environmental dynamic of Taxon Pulses establishes an episodic context for host and geographical colonization.
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Affiliation(s)
- Eric P Hoberg
- US National Parasite Collection, Agricultural Research Service, USDA, Beltsville Area Research Center, BARC East 1180 Beltsville, MD 20705, USA
| | - Daniel R Brooks
- H.W. Manter Laboratory of Parasitology, University of Nebraska State Museum of Natural History, University of Nebraska-Lincoln, Lincoln, NE 68588-0514, USA
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34
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Brooks DR, Hoberg EP, Boeger WA. In the Eye of the Cyclops: The Classic Case of Cospeciation and Why Paradigms are Important. COMP PARASITOL 2015. [DOI: 10.1654/4724c.1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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35
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Rossinelli S, Bacher S. Higher establishment success in specialized parasitoids: support for the existence of trade‐offs in the evolution of specialization. Funct Ecol 2014. [DOI: 10.1111/1365-2435.12323] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Silvia Rossinelli
- Department of Biology Unit Ecology & Evolution University of Fribourg Chemin du Musée 10 1700 Fribourg Switzerland
| | - Sven Bacher
- Department of Biology Unit Ecology & Evolution University of Fribourg Chemin du Musée 10 1700 Fribourg Switzerland
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36
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Brooks DR, Hoberg EP, Boeger WA, Gardner SL, Galbreath KE, Herczeg D, Mejía-Madrid HH, Rácz SE, Dursahinhan AT. Finding Them Before They Find Us: Informatics, Parasites, and Environments in Accelerating Climate Change. COMP PARASITOL 2014. [DOI: 10.1654/4724b.1] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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37
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Nagelkerke CJ, Menken SBJ. Coexistence of habitat specialists and generalists in metapopulation models of multiple-habitat landscapes. Acta Biotheor 2013; 61:467-80. [PMID: 23943092 DOI: 10.1007/s10441-013-9186-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 07/10/2013] [Indexed: 11/29/2022]
Abstract
In coarse-grained environments specialists are generally predicted to dominate. Empirically, however, coexistence with generalists is often observed. We present a simple, but previously unrecognized, mechanism for coexistence of a habitat generalist and a number of habitat specialist species. In our model all species have a metapopulation structure in a landscape consisting of patches of different habitat types, governed by local extinction and colonization. Each specialist is limited to its specific type of habitat. The generalist can use more types of habitat, has a lower local competitive ability but can exploit patches left open by the specialists. Our modeling shows that coexistence is easily possible. The mechanism amounts to a colonization/competition trade-off at the landscape level, where the colonization advantage of the inferior competitor does not arise from a higher colonization rate but from its ability to use more types of habitat. Habitat availability has to be intermediate: when there are few patches of each habitat, only the generalist is able to maintain itself and when there are many patches, high propagule pressure of the specialists excludes the generalist. Habitat selection or temporal variations in relative habitat quality are not necessary for coexistence. Increased niche-width, colonization rate or local competitive ability of the generalist enhances its performance compared to the specialists. Various types of habitat degradation favour generalism. When able to use a broad range of habitats, generalists can generate so much propagule pressure that only a low level of local competitive ability is needed to globally exclude the specialists. Hence, in a reversal of the original problem, the question is why there are so many specialist metapopulations?
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Affiliation(s)
- Cornelis J Nagelkerke
- Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, POB 94248, 1090 GE, Amsterdam, The Netherlands,
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McLeish MJ, Miller JT, Mound LA. Delayed colonisation of Acacia by thrips and the timing of host-conservatism and behavioural specialisation. BMC Evol Biol 2013; 13:188. [PMID: 24010723 PMCID: PMC3846595 DOI: 10.1186/1471-2148-13-188] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 09/03/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Repeated colonisation of novel host-plants is believed to be an essential component of the evolutionary success of phytophagous insects. The relative timing between the origin of an insect lineage and the plant clade they eat or reproduce on is important for understanding how host-range expansion can lead to resource specialisation and speciation. Path and stepping-stone sampling are used in a Bayesian approach to test divergence timing between the origin of Acacia and colonisation by thrips. The evolution of host-plant conservatism and ecological specialisation is discussed. RESULTS Results indicated very strong support for a model describing the origin of the common ancestor of Acacia thrips subsequent to that of Acacia. A current estimate puts the origin of Acacia at approximately 6 million years before the common ancestor of Acacia thrips, and 15 million years before the origin of a gall-inducing clade. The evolution of host conservatism and resource specialisation resulted in a phylogenetically under-dispersed pattern of host-use by several thrips lineages. CONCLUSIONS Thrips colonised a diversity of Acacia species over a protracted period as Australia experienced aridification. Host conservatism evolved on phenotypically and environmentally suitable host lineages. Ecological specialisation resulted from habitat selection and selection on thrips behavior that promoted primary and secondary host associations. These findings suggest that delayed and repeated colonisation is characterised by cycles of oligo- or poly-phagy. This results in a cumulation of lineages that each evolve host conservatism on different and potentially transient host-related traits, and facilitates both ecological and resource specialisation.
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Affiliation(s)
- Michael J McLeish
- Plant Geography Laboratory, Xishuangbanna Tropical Botanical Gardens, Chinese Academy and Sciences, Menglun, Mengla, Yunnan Province 666303, China
| | - Joseph T Miller
- Centre for Australian National Biodiversity Research, CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
| | - Laurence A Mound
- CSIRO Ecosystems Sciences, GPO Box 1700, Canberra, ACT 2601, Australia
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Peers MJL, Thornton DH, Murray DL. Reconsidering the specialist-generalist paradigm in niche breadth dynamics: resource gradient selection by Canada lynx and bobcat. PLoS One 2012; 7:e51488. [PMID: 23236508 PMCID: PMC3517500 DOI: 10.1371/journal.pone.0051488] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 11/05/2012] [Indexed: 11/18/2022] Open
Abstract
The long-standing view in ecology is that disparity in overall resource selection is the basis for identifying niche breadth patterns, with species having narrow selection being classified "specialists" and those with broader selection being "generalists". The standard model of niche breadth characterizes generalists and specialists as having comparable levels of overall total resource exploitation, with specialists exploiting resources at a higher level of performance over a narrower range of conditions. This view has gone largely unchallenged. An alternate model predicts total resource use being lower for the specialized species with both peaking at a comparable level of performance over a particular resource gradient. To reconcile the niche breadth paradigm we contrasted both models by developing range-wide species distribution models for Canada lynx, Lynx canadensis, and bobcat, Lynx rufus. Using a suite of environmental factors to define each species' niche, we determined that Canada lynx demonstrated higher total performance over a restricted set of variables, specifically those related to snow and altitude, while bobcat had higher total performance across most variables. Unlike predictions generated by the standard model, bobcat level of exploitation was not compromised by the trade-off with peak performance, and Canada lynx were not restricted to exploiting a narrower range of conditions. Instead, the emergent pattern was that specialist species have a higher total resource utilization and peak performance value within a smaller number of resources or environmental axes than generalists. Our results also indicate that relative differences in niche breadth are strongly dependent on the variable under consideration, implying that the appropriate model describing niche breadth dynamics between specialists and generalists may be more complex than either the traditional heuristic or our modified version. Our results demonstrate a need to re-evaluate traditional, but largely untested, assumptions regarding resource utilization in species with broad and narrow niches.
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Affiliation(s)
- Michael J L Peers
- Department of Biology, Trent University, Peterborough, Ontario, Canada.
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Laukkanen L, Leimu R, Muola A, Lilley M, Mutikainen P. Genetic factors affecting food-plant specialization of an oligophagous seed predator. J Evol Biol 2012. [DOI: 10.1111/jeb.12037] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- L. Laukkanen
- Department of Biology; Section of Ecology; University of Turku; Turku Finland
| | - R. Leimu
- Department of Plant Sciences; University of Oxford; Oxford UK
| | - A. Muola
- Department of Biology; Section of Ecology; University of Turku; Turku Finland
| | - M. Lilley
- Department of Biology; Section of Ecology; University of Turku; Turku Finland
| | - P. Mutikainen
- Institute of Integrative Biology; ETH-Zürich; ETH-Zentrum; Zürich Switzerland
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García-Robledo C, Horvitz CC. Parent-offspring conflicts, "optimal bad motherhood" and the "mother knows best" principles in insect herbivores colonizing novel host plants. Ecol Evol 2012; 2:1446-57. [PMID: 22957153 PMCID: PMC3434947 DOI: 10.1002/ece3.267] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Accepted: 03/26/2012] [Indexed: 12/03/2022] Open
Abstract
Specialization of insect herbivores to one or a few host plants stimulated the development of two hypotheses on how natural selection should shape oviposition preferences: The “mother knows best” principle suggests that females prefer to oviposit on hosts that increase offspring survival. The “optimal bad motherhood” principle predicts that females prefer to oviposit on hosts that increase their own longevity. In insects colonizing novel host plants, current theory predicts that initial preferences of insect herbivores should be maladaptive, leading to ecological traps. Ecological trap theory does not take into account the fact that insect lineages frequently switch hosts at both ecological and evolutionary time scales. Therefore, the behavior of insect herbivores facing novel hosts is also shaped by natural selection. Using a study system in which four Cephaloleia beetles are currently expanding their diets from native to exotic plants in the order Zingiberales, we determined if initial oviposition preferences are conservative, maladaptive, or follow the patterns predicted by the “mother knows best” or the “optimal bad motherhood” principles. Interactions with novel hosts generated parent–offspring conflicts. Larval survival was higher on native hosts. However, adult generally lived longer on novel hosts. In Cephaloleia beetles, oviposition preferences are usually associated with hosts that increase larval survival, female fecundity, and population growth. In most cases, Cephaloleia oviposition preferences follow the expectations of the “mothers knows best” principle.
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Affiliation(s)
- Carlos García-Robledo
- Department of Biology, University of Miami P.O. Box 249118, Coral Gables, Florida 33124-0421
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Harvey JA, Ximénez de Embún MG, Bukovinszky T, Gols R. The roles of ecological fitting, phylogeny and physiological equivalence in understanding realized and fundamental host ranges in endoparasitoid wasps. J Evol Biol 2012; 25:2139-2148. [DOI: 10.1111/j.1420-9101.2012.02596.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/26/2012] [Accepted: 07/15/2012] [Indexed: 10/28/2022]
Affiliation(s)
- J. A. Harvey
- Netherlands Institute of Ecology Department of Terrestrial Ecology Wageningen The Netherlands
| | | | - T. Bukovinszky
- Netherlands Institute of Ecology Department of Terrestrial Ecology Wageningen The Netherlands
- Netherlands Institute of Ecology Department of Aquatic Ecology Wageningen The Netherlands
| | - R. Gols
- Laboratory of Entomology Wageningen University Wageningen The Netherlands
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Barrett LG, Heil M. Unifying concepts and mechanisms in the specificity of plant-enemy interactions. TRENDS IN PLANT SCIENCE 2012; 17:282-92. [PMID: 22465042 DOI: 10.1016/j.tplants.2012.02.009] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 02/13/2012] [Accepted: 02/28/2012] [Indexed: 05/08/2023]
Abstract
Host ranges are commonly quantified to classify herbivores and plant pathogens as either generalists or specialists. Here, we summarize patterns and mechanisms in the interactions of plants with these enemies along different axes of specificity. We highlight the many dimensions within which plant enemies can specify and consider the underlying ecological, evolutionary and molecular mechanisms. Host resistance traits and enemy effectors emerge as central players determining host utilization and thus host range. Finally, we review approaches to studying the causes and consequences of variation in the specificity of plant-enemy interactions. Knowledge of the molecular mechanisms that determine host range is required to understand host shifts, and evolutionary transitions among specialist and generalist strategies, and to predict potential host ranges of pathogens and herbivores.
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Affiliation(s)
- Luke G Barrett
- CSIRO Plant Industry, GPO Box 1600, Canberra ACT, 2601, Australia
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Forister ML, Dyer LA, Singer MS, Stireman III JO, Lill JT. Revisiting the evolution of ecological specialization, with emphasis on insect–plant interactions. Ecology 2012; 93:981-91. [DOI: 10.1890/11-0650.1] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Forister ML, Scholl CF. Use of an exotic host plant affects mate choice in an insect herbivore. Am Nat 2012; 179:805-10. [PMID: 22617267 DOI: 10.1086/665647] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The colonization of exotic plants by herbivorous insects has provided opportunities for investigating causes and consequences of the evolution of niche breadth. The butterfly Lycaeides melissa utilizes exotic alfalfa, Medicago sativa, which is a relatively poor larval resource, and previous studies have found that caterpillars that consume M. sativa develop into smaller and less fecund adults. Here we investigate the effect of smaller female body size on male mate preference, a previously unexplored consequence of novel host use. Smaller females, which developed on the exotic host, were less likely to be visited by males. This result was confirmed with a second set of choice tests involving females reared on a single plant species, thus ruling out host-specific confounding factors. We suggest that an effect on mate choice be considered part of the complex suite of factors determining persistence of herbivorous insects following colonization of new habitats or resources.
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Affiliation(s)
- Matthew L Forister
- Program in Ecology, Evolution, and Conservation Biology, Department of Biology, University of Nevada, Reno, Nevada 89557, USA.
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García-Robledo C, Horvitz CC. Jack of all trades masters novel host plants: positive genetic correlations in specialist and generalist insect herbivores expanding their diets to novel hosts. J Evol Biol 2011; 25:38-53. [PMID: 22022877 DOI: 10.1111/j.1420-9101.2011.02401.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One explanation for the widespread host specialization of insect herbivores is the 'Jack of all trades-master of none' principle, which states that genotypes with high performance on one host will perform poorly on other hosts. This principle predicts that cross-host correlation in performance of genotypes will be negative. In this study, we experimentally explored cross-host correlations and performance among families in four species (two generalist and two specialist) of leaf beetles (Cephaloleia spp.) that are currently expanding their diets from native to exotic plants. All four species displayed similar responses in body size, developmental rates and mortality rates to experimentally controlled diets. When raised on novel hosts, body size of larvae, pupae and adults were reduced. Development times were longer, and larval mortality was higher on novel hosts. Genotype × host-plant interactions were not detected for most traits. All significant cross-host correlations were positive. These results indicate very different ecological and evolutionary dynamics than those predicted by the 'Jack of all trades-master of none' principle.
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47
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Normark BB, Johnson NA. Niche explosion. Genetica 2010; 139:551-64. [DOI: 10.1007/s10709-010-9513-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 10/25/2010] [Indexed: 11/30/2022]
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To speciate, or not to speciate? Resource heterogeneity, the subjectivity of similarity, and the macroevolutionary consequences of niche-width shifts in plant-feeding insects. Biol Rev Camb Philos Soc 2009; 85:393-411. [PMID: 20002390 DOI: 10.1111/j.1469-185x.2009.00109.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Coevolutionary studies on plants and plant-feeding insects have significantly improved our understanding of the role of niche shifts in the generation of new species. Evolving plant lineages essentially constitute moving islands and archipelagoes in resource space, and host shifts by insects are usually preceded by colonizations of novel resources. Critical to hypotheses concerning ecological speciation is what happens immediately before and after colonization attempts: if an available plant is too similar to the current host(s), it simply will be incorporated into the existing diet, but if it is too different, it will not be colonized in the first place. It thus seems that the probability of speciation is maximized when alternative hosts are at an 'intermediate' distance in resource space. In this review, I wish to highlight the possibility that resource similarity and, thus, the definition of 'intermediate', are subjective concepts that depend on the herbivore lineage's tolerance to dietary variation. This subjectivity of similarity means that changes in tolerance can either decrease or increase speciation probabilities depending on the distribution of plants in resource space: insect lineages with narrow tolerances are likely to speciate by 'island-hopping' on young, species-rich plant groups, whereas more generalized lineages could speciate by shifting among resource archipelagoes formed by higher plant taxa. Repeated and convergent origins of traits known to broaden or to restrict host-plant use in multiple different insect groups provide opportunities for studying how tolerance and resource heterogeneity may interact to determine speciation rates.
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