1
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An increasing human-elephant conflict? Impact of African elephant on cultivated cashew trees. EUR J WILDLIFE RES 2023. [DOI: 10.1007/s10344-022-01629-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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2
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Coetsee C, Botha J, Case MF, Manganyi A, Siebert F. The hard lives of trees in African savanna—Even without elephants. AUSTRAL ECOL 2023. [DOI: 10.1111/aec.13283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Corli Coetsee
- Scientific Services South African National Parks, Savanna Node, Kruger National Park Skukuza South Africa
- School of Natural Resource Management Nelson Mandela University George South Africa
| | - Judith Botha
- Scientific Services South African National Parks, Savanna Node, Kruger National Park Skukuza South Africa
| | - Madelon F. Case
- University of Oregon Eugene Oregon USA
- U.S. Geological Survey Forest and Rangeland Ecosystem Science Center Corvallis Oregon USA
| | - Adolf Manganyi
- Scientific Services South African National Parks, Savanna Node, Kruger National Park Skukuza South Africa
| | - Frances Siebert
- Unit for Environmental Sciences and Management North‐West University Potchefstroom South Africa
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3
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Young TP, Kimuyu DN, LaMalfa EM, Werner CM, Jones C, Masudi P, Ang'ila R, Sensenig RL. Effects of large mammalian herbivory, previous fire, and year of burn on fire behavior in an African savanna. Ecosphere 2022. [DOI: 10.1002/ecs2.3980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Truman. P. Young
- Department of Plant Sciences University of California Davis California USA
- Mpala Research Centre Nanyuki Kenya
| | - Duncan N. Kimuyu
- Mpala Research Centre Nanyuki Kenya
- Department of Natural Resources Karatina University Karatina Kenya
| | - Eric M. LaMalfa
- Department of Wildland Resources and Ecology Center Utah State University Logan Utah USA
| | - Chhaya M. Werner
- Department of Botany and Wyoming EPSCoR University of Wyoming Laramie Wyoming USA
| | | | - Phyllis Masudi
- Department of Animal Production University of Nairobi Kangemi Kenya
| | - Robert Ang'ila
- Department of Environmental Studies Karatina University Karatina Kenya
| | - Ryan L. Sensenig
- Department of Biological Sciences Goshen College Goshen Indiana USA
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4
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Hays BR, Riginos C, Palmer TM, Doak DF, Gituku BC, Maiyo NJ, Mutisya S, Musila S, Goheen JR. Demographic consequences of mutualism disruption: Browsing and big-headed ant invasion drive acacia population declines. Ecology 2022; 103:e3655. [PMID: 35132627 DOI: 10.1002/ecy.3655] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 10/14/2021] [Accepted: 10/26/2021] [Indexed: 11/09/2022]
Abstract
Across the globe, biological invasions have disrupted mutualisms, producing reverberating consequences for ecosystems. Although invasive species frequently trigger mutualism disruptions, few studies have quantified the demographic mechanisms by which mutualism breakdown may generate population effects. In a Kenyan savanna, the invasive big-headed ant (Pheidole megacephala) has disrupted a foundational mutualism between the monodominant whistling-thorn tree (Acacia drepanolobium) and native ants (Crematogaster spp.) that deter browsing by large mammalian herbivores. We conducted experiments to quantify the demographic consequences of this mutualism disruption in the presence and absence of large mammalian herbivores. Invasion by P. megacephala exacerbated population declines of A. drepanolobium, primarily through decreased survival and reproduction of adult trees. However, these fitness reductions were small compared to those resulting from the presence of large mammalian herbivores, which negatively impacted growth and survival. Contrary to expectation, the expulsion of metabolically costly Crematogaster mutualists by P. megacephala did not result in higher population growth rates for trees protected from large mammalian herbivores. Our results suggest that invasive P. megacephala may impose a direct metabolic cost to trees exceeding that of native mutualists while providing no protection from browsing by large mammalian herbivores. Across landscapes, we expect that invasion by P. megacephala will reduce A. drepanolobium populations, but that the magnitude and demographic pathways of this effect will hinge on the presence and abundance of browsers.
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Affiliation(s)
- Brandon R Hays
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Corinna Riginos
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA.,The Nature Conservancy, 258 Main Street, Lander, Wyoming, USA
| | - Todd M Palmer
- Department of Biology, University of Florida, Florida, USA
| | - Daniel F Doak
- Environmental Studies Program, University of Colorado, Boulder, Colorado, USA
| | - Benard C Gituku
- Department of Land Resource Management & Agricultural Technology, University of Nairobi, Nairobi, Kenya.,Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Nelly J Maiyo
- Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Samuel Mutisya
- Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Simon Musila
- Mammalogy Section, National Museums of Kenya, Nairobi, Kenya
| | - Jacob R Goheen
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
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5
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Hensel MJS, Silliman BR, Hensel E, Byrnes JEK. Feral hogs control brackish marsh plant communities over time. Ecology 2022; 103:e03572. [PMID: 34706065 DOI: 10.1002/ecy.3572] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 07/16/2021] [Accepted: 07/26/2021] [Indexed: 11/07/2022]
Abstract
Feral hogs modify ecosystems by consuming native species and altering habitat structure. These invasions can generate fundamentally different post-invasion habitats when disturbance changes community structure, ecosystem function, or recovery dynamics. Here, we use multiple three-year exclusion experiments to describe how feral hogs affect hyper-productive brackish marshes over time. We find that infrequent yet consistent hog foraging and trampling suppresses dominant plants by generating a perpetually disturbed habitat that favors competitively inferior species and disallows full vegetative recovery over time. Along borders between plant monocultures, trampling destroys dominant graminoids responsible for most aboveground marsh biomass while competitively inferior plants increase fivefold. Hog activities shift the brackish marsh disturbance regime from pulse to press, which changes the plant community: competitively inferior plants increase coverage, species diversity is doubled, and live cover is lowered by 30% as large plants are unable to take hold in hog-disturbed areas. Release from disturbance does not result in complete recovery (i.e., dominant plant monocultures) because hog consumer control is a combination of both top-down control and broader engineering effects. These results highlight how habitats are susceptible to invasive effects outside of structural destruction alone, especially if large consumers are pervasive over time and change the dynamics that sustain recovery.
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Affiliation(s)
- Marc J S Hensel
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, 02125, USA
- Nicholas School for the Environment, Duke University, Beaufort, North Carolina, 28516, USA
- Department of Biological Sciences, Virginia Institute of Marine Sciences, College of William and Mary, Gloucester Point, Virginia, 23062, USA
| | - Brian R Silliman
- Nicholas School for the Environment, Duke University, Beaufort, North Carolina, 28516, USA
| | - Enie Hensel
- Department of Biological Sciences, Virginia Institute of Marine Sciences, College of William and Mary, Gloucester Point, Virginia, 23062, USA
| | - Jarrett E K Byrnes
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, 02125, USA
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6
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Titcomb GC, Amooni G, Mantas JN, Young HS. The effects of herbivore aggregations at water sources on savanna plants differ across soil and climate gradients. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02422. [PMID: 34288228 DOI: 10.1002/eap.2422] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/29/2021] [Accepted: 03/22/2021] [Indexed: 06/13/2023]
Abstract
Water sources in arid and semiarid ecosystems support humans, wildlife, and domestic animals, forming nodes of activity that sculpt surrounding plant communities and impact critical grazing and soil systems. However, global aridification and changing surface water supply threaten to disrupt these water resources, with strong implications for conservation and management of these ecosystems. To understand how effects of herbivore aggregation at water impact plant communities across contexts, we measured herbivore activity, plant height, cover (trees, grasses, forbs, and bare ground), diversity, and composition at 17 paired water sources and matrix sites across a range of abiotic factors in a semiarid savanna in Kenya. The effects of proximity to surface water and herbivore aggregation on plant communities varied substantially depending on soil and rainfall. In arid areas with nutrient-poor sandy soils, forb and tree cover were 50% lower at water sources compared to neighboring matrix sites, bare ground was 20% higher, species richness was 15% lower, and a single globally important grazing grass (Cynodon dactylon) dominated 60% of transects. However, in mesic areas with nutrient-rich finely textured soils, species richness was 25% higher, despite a 40% increase in bare ground, concurrent with the decline of a dominant tall grass (Themeda triandra) and increase in C. dactylon and other grass species near water sources. Recent rainfall was important for grasses; cover was higher relative to matrix sites only during wet periods, a potential indication of compensatory grazing. These findings suggest that effects of herbivore aggregation on vegetation diversity and composition will vary in magnitude, and in some cases direction, depending on other factors at the site. Where moisture and nutrient resources are high and promote the dominance of few plant species, herbivore aggregations may maintain diversity by promoting grazing lawns and increasing nondominant species cover. However, in arid conditions and sites with low nutrient availability, diversity can be substantially reduced by these aggregations. Our results highlight the importance of considering abiotic conditions when managing for effects of herbivore aggregations near water. This will be particularly important for future managers in light of growing global aridification and surface water changes.
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Affiliation(s)
- Georgia C Titcomb
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, 93106, USA
- Mpala Research Centre, Box 555, Nanyuki, 10400, Kenya
| | | | | | - Hillary S Young
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, 93106, USA
- Mpala Research Centre, Box 555, Nanyuki, 10400, Kenya
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Djogbenou A, Azihou AF, Dassou AG, Assogbadjo AE, Kassa B, Gaoue OG. Limited ant co-occurrence and defensive mutualism in Acacia plants in a West African savanna. AOB PLANTS 2021; 13:plab036. [PMID: 34234937 PMCID: PMC8255073 DOI: 10.1093/aobpla/plab036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 06/02/2021] [Indexed: 06/13/2023]
Abstract
Our understanding of the role of fire and effect of ant species composition, beyond their diversity and abundance, on the effectiveness of mutualism defence is limited. Most of our knowledge of ant-plant defence in tropical Africa is biased towards East African savannas which have richer soil, higher primary productivity and a more diverse arthropods and mammal community than West African savannas. We assessed the diversity of ant species associated with Acacia species in the Pendjari Biosphere Reserve in the Dahomey Gap, and their impacts on elephant damage. Elephant damage, ant diversity and abundance were measured in stands of five Acacia species. Eleven ant species were identified in the Acacia stands. The composition of these ant communities varied across Acacia species. Pair of ant species co-occurred in only 2 % of sampled trees, suggesting a strong competitive exclusion. Within this annually burnt environment, ants were rare on small trees. The intensity of elephant-caused branch breaking did not vary between trees with ants and trees without ants, suggesting limited Acacia-ant mutualism. Such limited biotic defence may mask strong physical and chemical defence mechanisms of Acacia trees against elephant damage. Ant assemblages in West Africa, unlike those in the more productive East Africa, are particularly species-poor. However, there is a convergence between these two regions in low rate of ant co-occurrence which might indicate strong competitive exclusion. Our study suggests that such low ant species richness while limiting the efficacy of mutualism in controlling mega-herbivore damage may mask a strong defence syndrome.
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Affiliation(s)
- Anyse Djogbenou
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Akomian F Azihou
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Anicet G Dassou
- Laboratory of Biotechnology, Genetic Resources, Plant and Animal Breeding, Faculty of Sciences and Technology of Dassa, National University of Sciences, Technology, Engineering and Mathematics, 01 BP 14, Dassa-Zoumè, Benin
| | - Achille E Assogbadjo
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Barthelemy Kassa
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Orou G Gaoue
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA
- Faculty of Agronomy, University of Parakou, BP 123, Parakou, Benin
- Department of Geography, Environmental Management and Energy Sciences, University of Johannesburg, APK Campus, Johannesburg, South Africa
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8
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Parker JM, Webb CT, Daballen D, Goldenberg SZ, Lepirei J, Letitiya D, Lolchuragi D, Leadismo C, Douglas-Hamilton I, Wittemyer G. Poaching of African elephants indirectly decreases population growth through lowered orphan survival. Curr Biol 2021; 31:4156-4162.e5. [PMID: 34343478 DOI: 10.1016/j.cub.2021.06.091] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 06/18/2021] [Accepted: 06/29/2021] [Indexed: 10/20/2022]
Abstract
Prolonged maternal care is vital to the well-being of many long-lived mammals.1 The premature loss of maternal care, i.e., orphaning, can reduce offspring survival even after weaning is complete.2-5 However, ecologists have not explicitly assessed how orphaning impacts population growth. We examined the impact of orphaning on population growth in a free-ranging African elephant population, using 19 years of individual-based demographic monitoring data. We compared orphan and nonorphan survival, performed a sensitivity analysis to understand how population growth responds to the probability of being orphaned and orphan survival, and investigated how sensitivity to these orphan parameters changed with level of poaching. Orphans were found to have lower survival compared to nonorphaned age mates, and population growth rate was negatively correlated with orphaning probability and positively correlated with orphan survival. This demonstrates that, in addition to its direct effects, adult elephant death indirectly decreases population growth through orphaning. Population growth rate's sensitivity to orphan survival increased for the analysis parameterized using only data from years of more poaching, indicating orphan survival is more important for population growth as orphaning increases. We conclude that orphaning substantively decreases population growth for elephants and should not be overlooked when quantifying the impacts of poaching. Moreover, we conclude that population models characterizing systems with extensive parental care benefit from explicitly incorporating orphan stages and encourage research into quantifying effects of orphaning in other social mammals of conservation concern.
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Affiliation(s)
- Jenna M Parker
- Graduate Degree Program in Ecology and Department of Fish, Wildlife and Conservation Biology, Colorado State University, 1474 Campus Delivery, Fort Collins, CO 80523, USA; Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya.
| | - Colleen T Webb
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, 1878 Campus Delivery, Fort Collins, CO 80523, USA
| | - David Daballen
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
| | - Shifra Z Goldenberg
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya; Conservation Ecology Center, Smithsonian Conservation Biology Institute, 1500 Remount Road, Front Royal, VA 22630, USA; Institute for Conservation Research, San Diego Zoo Wildlife Alliance, 15600 San Pasqual Valley Road, Escondido, CA 92027, USA
| | - Jerenimo Lepirei
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
| | - David Letitiya
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
| | - David Lolchuragi
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
| | - Chris Leadismo
- Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
| | | | - George Wittemyer
- Graduate Degree Program in Ecology and Department of Fish, Wildlife and Conservation Biology, Colorado State University, 1474 Campus Delivery, Fort Collins, CO 80523, USA; Save the Elephants, Marula Manor, Marula Lane, Karen, Nairobi 00200, Kenya
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9
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Young TP, Kimuyu DM, Odadi WO, Wells HBM, Wolf AA. Naïve plant communities and individuals may initially suffer in the face of reintroduced megafauna: An experimental exploration of rewilding from an African savanna rangeland. PLoS One 2021; 16:e0248855. [PMID: 33822786 PMCID: PMC8023473 DOI: 10.1371/journal.pone.0248855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/06/2021] [Indexed: 12/04/2022] Open
Abstract
Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individual plants, adjust to the absence of herbivores in ways that can ill-prepare them for the return of these herbivores. Three lines of evidence suggest that these "naïve" individuals, populations, and communities are likely to initially suffer from herbivore rewilding. First, plots protected from wild herbivores for the past 25 years have developed rich diversity of woody plants that are absent from unfenced plots, and presumably would disappear upon rewilding. Second, individuals of the dominant tree in this system, Acacia drepanolobium, greatly reduce their defences in the absence of browsers, and the sudden arrival of these herbivores (in this case, through a temporary fence break), resulted in far greater elephant damage than for their conspecifics in adjacent plots that had been continually exposed to herbivory. Third, the removal of herbivores favoured the most palatable grass species, and a large number of rarer species, which presumably would be at risk from herbivore re-introduction. In summary, the native communities that we observe in defaunated landscapes may be very different from their pre-defaunation states, and we are likely to see some large changes to these plant communities upon rewilding with large herbivores, including potential reductions in plant diversity. Lastly, our experimental manipulation of cattle represents an additional test of the role of livestock in rewilding. Cattle are in many ways ecologically dissimilar to wildlife (in particular their greater densities), but in other ways they may serve as ecological surrogates for wildlife, which could buffer ecosystems from some of the ecological costs of rewilding. More fundamentally, African savannah ecosystems represent a challenge to traditional Western definitions of "wilderness" as ecosystems free of human impacts. We support the suggestion that as we "rewild" our biodiversity landscapes, we redefine "wildness" in the 21st Century to be inclusive of (low impact, and sometimes traditional) human practices that are compatible with the sustainability of native (and re-introduced) biodiversity.
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Affiliation(s)
- Truman P. Young
- Department of Plant Sciences and Ecology Graduate Group, University of California, Davis, Davis, CA, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Duncan M. Kimuyu
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Wilfred O. Odadi
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Egerton University, Egerton, Kenya
| | - Harry B. M. Wells
- Sustainability Research Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
- Lolldaiga Hills Research Programme, Nanyuki, Kenya
| | - Amelia A. Wolf
- Department of Integrative Biology, University of Texas, Austin, TX, United States of America
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10
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Werner CM, Kimuyu D, Veblen KE, Sensenig RL, LaMalfa E, Young TP. Synergistic effects of long-term herbivory and previous fire on fine-scale heterogeneity of prescribed grassland burns. Ecology 2021; 102:e03270. [PMID: 33340104 DOI: 10.1002/ecy.3270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/17/2020] [Accepted: 10/26/2020] [Indexed: 11/11/2022]
Abstract
Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and resultant fire heterogeneity. We carried out 36 controlled burns within replicated experimental plots that had allowed differential access by wild and domestic large herbivores since 1995 in a savanna ecosystem in Kenya. Half of these were reburns of plots burned 5 yr previously. We show here that the fine-scale spatial heterogeneity of fire was greater in plots (1) previously burned, (2) accessible to large herbivores, and especially (3) these two in combination. An additional embedded experiment demonstrated that even small experimental burn-free patches can have strong positive effects on tree saplings, which experienced less damage during controlled burns and quicker postfire recovery. This work highlights the importance of simultaneously examining the interactions between fire and herbivory on fuel heterogeneity, which can have important impacts on the growth of woody saplings in savanna grasslands.
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Affiliation(s)
- Chhaya M Werner
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Department of Physiological Diversity, Helmholtz Center for Environmental Research (UFZ), Leipzig, D-04318, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, D-04103, Germany.,Department of Ecology, University of Oulu, Oulu, FI-90014, Finland
| | - Duncan Kimuyu
- Mpala Research Centre, Nanyuki, Kenya.,Department of Natural Resources, Karatina University, Karatina, 10101, Kenya
| | - Kari E Veblen
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Ryan L Sensenig
- Mpala Research Centre, Nanyuki, Kenya.,Department of Biological Sciences, Goshen College, Goshen, Indiana, 46526, USA
| | - Eric LaMalfa
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Truman P Young
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Mpala Research Centre, Nanyuki, Kenya
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Buisson E, Fidelis A, Overbeck GE, Schmidt IB, Durigan G, Young TP, Alvarado ST, Arruda AJ, Boisson S, Bond W, Coutinho A, Kirkman K, Oliveira RS, Schmitt MH, Siebert F, Siebert SJ, Thompson DI, Silveira FAO. A research agenda for the restoration of tropical and subtropical grasslands and savannas. Restor Ecol 2020. [DOI: 10.1111/rec.13292] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Elise Buisson
- Avignon Université, Institut Méditerranéen de Biodiversité et d'Ecologie ‐ IMBE, CNRS, IRD Aix Marseille Université, IUT d'Avignon, AGROPARC BP61207 Avignon cedex 9 84911 France
- Department of Plant Sciences University of California Davis CA 95616 U.S.A
| | - Alessandra Fidelis
- Lab of Vegetation Ecology, Instituto de Biociências Universidade Estadual Paulista (UNESP) Av. 24A, 1515 Rio Claro SP 13506‐900 Brazil
| | - Gerhard E. Overbeck
- Departamento de Botânica Universidade Federal do Rio Grande do Sul Av. Bento Gonçalves 9500, CEP Porto Alegre RS 91501‐970 Brazil
| | - Isabel B. Schmidt
- Department of Ecology University of Brasília, Campus Universitário Darcy Ribeiro Brasilia Brazil
| | - Giselda Durigan
- Floresta Estadual de Assis Instituto Florestal do Estado de São Paulo P.O. Box 104 Assis SP 19802‐970 Brazil
| | - Truman P. Young
- Department of Plant Sciences University of California Davis CA 95616 U.S.A
| | | | - André J. Arruda
- Avignon Université, Institut Méditerranéen de Biodiversité et d'Ecologie ‐ IMBE, CNRS, IRD Aix Marseille Université, IUT d'Avignon, AGROPARC BP61207 Avignon cedex 9 84911 France
- Departamento de Genética, Ecologia e Evolução, Instituto de Ciências Biológicas Universidade Federal de Minas Gerais Av. Antônio Carlos 6627, CEP Belo Horizonte MG 31270‐901 Brazil
| | - Sylvain Boisson
- Université de Liège Gembloux Agro‐Bio Tech Biodiversity and Landscape, TERRA Gembloux Belgium
| | - William Bond
- Department of Biological Sciences University of Cape Town Rondebosch South Africa
| | - André Coutinho
- Ecology Graduate Program University of Brasília Campus Universitário Darcy Ribeiro Brasília DF 70.910‐900 Brazil
| | - Kevin Kirkman
- School of Life Science University of KwaZulu‐Natal Pietermaritzburg KwaZulu‐Natal South Africa
| | - Rafael S. Oliveira
- Department of Plant Biology, Institute of Biology University of Campinas – UNICAMP Campinas SP Brazil
| | - Melissa H. Schmitt
- South African Environmental Observation Network, Ndlovu Node, Scientific Services Kruger National Park Private Bag X1021 Phalaborwa 1390 South Africa
- Department of Ecology, Evolution, and Marine Biology University of California Santa Barbara Santa Barbara CA U.S.A
| | - Frances Siebert
- Unit for Environmental Sciences and Management North‐West University 11 Hoffman Street Potchefstroom North‐West 2531 South Africa
| | - Stefan J. Siebert
- Unit for Environmental Sciences and Management North‐West University 11 Hoffman Street Potchefstroom North‐West 2531 South Africa
| | - Dave I. Thompson
- South African Environmental Observation Network, Ndlovu Node, Scientific Services Kruger National Park Private Bag X1021 Phalaborwa 1390 South Africa
- School of Geography, Archaeology, and Environmental Studies University of the Witwatersrand Private Bag 3 WITS 2050 South Africa
| | - Fernando A. O. Silveira
- Departamento de Genética, Ecologia e Evolução, Instituto de Ciências Biológicas Universidade Federal de Minas Gerais Av. Antônio Carlos 6627, CEP Belo Horizonte MG 31270‐901 Brazil
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Abstract
Abstract
Global change has been accompanied by recent increases in the frequency and intensity of various ecological disturbances (e.g., fires, floods, cyclones), both natural and anthropogenic in origin. Because these disturbances often interact, their cumulative and synergistic effects can result in unforeseen consequences, such as insect outbreaks, crop failure, and progressive ecosystem degradation. We consider the roles of biological legacies, thresholds, and lag effects responsible for the distinctive impacts of interacting disturbances. We propose a hierarchical classification that distinguishes the patterns and implications associated with random co-occurrences, individual links, and multiple links among disturbances that cascade in chains or networks. Disturbance-promoting interactions apparently prevail over disturbance-inhibiting ones. Complex and exogenous disturbance cascades are less predictable than simple and endogenous links because of their dependency on adjacent or synchronous events. These distinctions help define regional disturbance regimes and can have implications for natural selection, risk assessment, and options for management intervention.
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Affiliation(s)
- Philip J Burton
- Ecosystem Science and Management, University of Northern British Columbia, Terrace, British Columbia, Canada
| | - Anke Jentsch
- Bayreuth Center of Ecology and Environmental Research, Department of Disturbance Ecology, Bayreuth University, Bayreuth, Germany
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13
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Tekin E, Diamant ES, Cruz‐Loya M, Enriquez V, Singh N, Savage VM, Yeh PJ. Using a newly introduced framework to measure ecological stressor interactions. Ecol Lett 2020; 23:1391-1403. [DOI: 10.1111/ele.13533] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 02/13/2020] [Accepted: 04/16/2020] [Indexed: 12/30/2022]
Affiliation(s)
- Elif Tekin
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
- Department of Computational Medicine the David Geffen School of Medicine University of California Los Angeles CA USA
| | - Eleanor S. Diamant
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
| | - Mauricio Cruz‐Loya
- Department of Computational Medicine the David Geffen School of Medicine University of California Los Angeles CA USA
| | - Vivien Enriquez
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
| | - Nina Singh
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
| | - Van M. Savage
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
- Department of Computational Medicine the David Geffen School of Medicine University of California Los Angeles CA USA
- Santa Fe Institute Santa Fe NM87501USA
| | - Pamela J. Yeh
- Department of Ecology and Evolutionary Biology University of California Los Angeles CA90095USA
- Santa Fe Institute Santa Fe NM87501USA
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14
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Abstract
Reconstructing prehistoric animal communities is important for understanding the emergence of modern ecosystems and the environmental context of human evolution. A new study of African fossils spanning seven million years shows that ancient large-herbivore assemblages were functionally distinct from those that exist today.
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Affiliation(s)
- Robert M Pringle
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
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15
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Wigley BJ, Coetsee C, Kruger LM, Ratnam J, Sankaran M. Ants, fire, and bark traits affect how African savanna trees recover following damage. Biotropica 2019. [DOI: 10.1111/btp.12683] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Benjamin J. Wigley
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Natural Resource Management Nelson Mandela University George South Africa
| | - Corli Coetsee
- School of Natural Resource Management Nelson Mandela University George South Africa
- Scientific Services Kruger National Park Skukuza South Africa
| | - Laurence M. Kruger
- Organisation for Tropical Studies Skukuza South Africa
- Biology Department University of Cape Town Rondebosch South Africa
| | - Jayashree Ratnam
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
| | - Mahesh Sankaran
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
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16
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Forbes ES, Cushman JH, Burkepile DE, Young TP, Klope M, Young HS. Synthesizing the effects of large, wild herbivore exclusion on ecosystem function. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13376] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elizabeth S. Forbes
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - J. Hall Cushman
- Department of Natural Resources and Environmental Science University of Nevada – Reno Reno Nevada
| | - Deron E. Burkepile
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences University of California, Davis Davis California
| | - Maggie Klope
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
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17
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Pringle RM, Kartzinel TR, Palmer TM, Thurman TJ, Fox-Dobbs K, Xu CCY, Hutchinson MC, Coverdale TC, Daskin JH, Evangelista DA, Gotanda KM, A Man In 't Veld N, Wegener JE, Kolbe JJ, Schoener TW, Spiller DA, Losos JB, Barrett RDH. Predator-induced collapse of niche structure and species coexistence. Nature 2019; 570:58-64. [PMID: 31168105 DOI: 10.1038/s41586-019-1264-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 05/01/2019] [Indexed: 12/31/2022]
Abstract
Biological invasions are both a pressing environmental challenge and an opportunity to investigate fundamental ecological processes, such as the role of top predators in regulating biodiversity and food-web structure. In whole-ecosystem manipulations of small Caribbean islands on which brown anole lizards (Anolis sagrei) were the native top predator, we experimentally staged invasions by competitors (green anoles, Anolis smaragdinus) and/or new top predators (curly-tailed lizards, Leiocephalus carinatus). We show that curly-tailed lizards destabilized the coexistence of competing prey species, contrary to the classic idea of keystone predation. Fear-driven avoidance of predators collapsed the spatial and dietary niche structure that otherwise stabilized coexistence, which intensified interspecific competition within predator-free refuges and contributed to the extinction of green-anole populations on two islands. Moreover, whereas adding either green anoles or curly-tailed lizards lengthened food chains on the islands, adding both species reversed this effect-in part because the apex predators were trophic omnivores. Our results underscore the importance of top-down control in ecological communities, but show that its outcomes depend on prey behaviour, spatial structure, and omnivory. Diversity-enhancing effects of top predators cannot be assumed, and non-consumptive effects of predation risk may be a widespread constraint on species coexistence.
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Affiliation(s)
- Robert M Pringle
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA.
| | - Tyler R Kartzinel
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA.,Department of Ecology & Evolutionary Biology, Brown University, Providence, RI, USA
| | - Todd M Palmer
- Department of Biology, University of Florida, Gainesville, FL, USA
| | - Timothy J Thurman
- Department of Biology, McGill University, Montreal, Quebec, Canada.,Smithsonian Tropical Research Institute, Panama City, Panama.,Redpath Museum, McGill University, Montreal, Quebec, Canada
| | - Kena Fox-Dobbs
- Department of Geology, University of Puget Sound, Tacoma, WA, USA
| | - Charles C Y Xu
- Department of Biology, McGill University, Montreal, Quebec, Canada.,Redpath Museum, McGill University, Montreal, Quebec, Canada
| | - Matthew C Hutchinson
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Tyler C Coverdale
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA.,Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - Joshua H Daskin
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA.,Department of Ecology & Evolutionary Biology, Yale University, New Haven, CT, USA
| | - Dominic A Evangelista
- Department of Biological Sciences, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Kiyoko M Gotanda
- Department of Biology, McGill University, Montreal, Quebec, Canada.,Redpath Museum, McGill University, Montreal, Quebec, Canada.,Department of Zoology, University of Cambridge, Cambridge, UK
| | | | - Johanna E Wegener
- Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA
| | - Jason J Kolbe
- Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA
| | - Thomas W Schoener
- Department of Evolution and Ecology, University of California, Davis, CA, USA
| | - David A Spiller
- Department of Evolution and Ecology, University of California, Davis, CA, USA
| | - Jonathan B Losos
- Department of Biology, Washington University, Saint Louis, MO, USA
| | - Rowan D H Barrett
- Department of Biology, McGill University, Montreal, Quebec, Canada.,Redpath Museum, McGill University, Montreal, Quebec, Canada
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18
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Branco PS, Merkle JA, Pringle RM, Pansu J, Potter AB, Reynolds A, Stalmans M, Long RA. Determinants of elephant foraging behaviour in a coupled human‐natural system: Is brown the new green? J Anim Ecol 2019; 88:780-792. [DOI: 10.1111/1365-2656.12971] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 01/26/2019] [Indexed: 11/29/2022]
Affiliation(s)
- Paola S. Branco
- Department of Fish and Wildlife Sciences University of Idaho Moscow Idaho
| | - Jerod A. Merkle
- Department of Zoology and Physiology University of Wyoming Laramie Wyoming
| | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey
| | - Johan Pansu
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey
| | - Arjun B. Potter
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey
| | - Alana Reynolds
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey
| | - Marc Stalmans
- Department of Scientific Services Gorongosa National Park Sofala Mozambique
| | - Ryan A. Long
- Department of Fish and Wildlife Sciences University of Idaho Moscow Idaho
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19
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Giery ST, Layman CA. Ecological Consequences Of Sexually Selected Traits: An Eco-Evolutionary Perspective. QUARTERLY REVIEW OF BIOLOGY 2019. [DOI: 10.1086/702341] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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20
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Sensenig RL, Kimuyu DK, Ruiz Guajardo JC, Veblen KE, Riginos C, Young TP. Fire disturbance disrupts an acacia ant-plant mutualism in favor of a subordinate ant species. Ecology 2018; 98:1455-1464. [PMID: 28273343 DOI: 10.1002/ecy.1797] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 02/07/2017] [Accepted: 02/24/2017] [Indexed: 11/08/2022]
Abstract
Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mortality and/or decreasing colony size, which potentially could alter dominance hierarchies if subordinate species are more fire resilient. We used a large-scale, replicated fire experiment to examine long-term effects of fire on acacia-ant community composition. To determine if fire shifted ant occupancy from a competitive dominant to a subordinate ant species, we surveyed the acacia-ant community in 6-7 yr old burn sites and examined how the spatial scale of these burns influenced ant community responses. We then used two short-term fire experiments to explore possible mechanisms for the shifts in community patterns observed. Because survival of ant colonies is largely dependent on their ability to detect and escape an approaching fire, we first tested the evacuation response of all four ant species when exposed to smoke (fire signal). Then to better understand how fire and its interaction with large mammal herbivory affect the density of ants per tree, we quantified ant worker density in small prescribed burns within herbivore exclusion plots. We found clear evidence suggesting that fire disturbance favored the subordinate ant Crematogaster nigriceps more than the dominant and strong mutualist ant C. mimosae, whereby C. nigriceps (1) was the only species to occupy a greater proportion of trees in 6-7 yr old burn sites compared to unburned sites, (2) had higher burn/unburn tree ratios with increasing burn size, and (3) evacuated significantly faster than C. mimosae in the presence of smoke. Fire and herbivory had opposite effects on ant density per meter of branch for both C. nigriceps and C. mimosae, with fire decreasing ant densities per meter of branch and the presence of large herbivores increasing ant density. Taken together, these experiments suggest that major ecosystem disturbances like fire can disrupt mutualistic associations and maintain diversity in partner quality and identity despite a clear dominance hierarchy.
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Affiliation(s)
- Ryan L Sensenig
- Department of Biological Sciences, Goshen College, Goshen, Indiana, 46526, USA.,Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
| | - Duncan K Kimuyu
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,School of Natural Resource Management and Environmental Studies, Karatina University, Karatina, Kenya
| | - Juan C Ruiz Guajardo
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Evolution and Ecology and Center for Population Biology, University of California, Davis, California, 95616, USA
| | - Kari E Veblen
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Northern Rockies Conservation Cooperative, Jackson, Wyoming, 83001, USA.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Truman P Young
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Plant Sciences, University of California, Davis, California, 95616, USA
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21
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Coverdale TC, Goheen JR, Palmer TM, Pringle RM. Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants. Ecology 2018; 99:1724-1736. [DOI: 10.1002/ecy.2397] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 05/11/2018] [Accepted: 05/21/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Tyler C. Coverdale
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA
| | - Jacob R. Goheen
- Department of Zoology & Physiology University of Wyoming Laramie Wyoming 82071 USA
| | - Todd M. Palmer
- Department of Biology University of Florida Gainesville Florida 32611 USA
| | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA
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22
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Goheen JR, Augustine DJ, Veblen KE, Kimuyu DM, Palmer TM, Porensky LM, Pringle RM, Ratnam J, Riginos C, Sankaran M, Ford AT, Hassan AA, Jakopak R, Kartzinel TR, Kurukura S, Louthan AM, Odadi WO, Otieno TO, Wambua AM, Young HS, Young TP. Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments. Ann N Y Acad Sci 2018; 1429:31-49. [DOI: 10.1111/nyas.13848] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/03/2018] [Accepted: 04/06/2018] [Indexed: 11/26/2022]
Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
- Mpala Research Centre; Nanyuki Kenya
| | | | - Kari E. Veblen
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
| | - Duncan M. Kimuyu
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Todd M. Palmer
- Department of Biology; University of Florida; Gainesville Florida
- Mpala Research Centre; Nanyuki Kenya
| | | | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey
- Mpala Research Centre; Nanyuki Kenya
| | | | | | - Mahesh Sankaran
- National Centre for Biological Sciences, TIFR; Bangalore India
- School of Biology, University of Leeds; Leeds United Kingdom
| | - Adam T. Ford
- Department of Biology; University of British Columbia; Kelowna British Columbia Canada
| | | | - Rhiannon Jakopak
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
| | - Tyler R. Kartzinel
- Department of Ecology and Evolutionary Biology; Brown University; Providence Rhode Island
| | | | | | - Wilfred O. Odadi
- Department of Natural Resources; Egerton University; Egerton Kenya
- Mpala Research Centre; Nanyuki Kenya
| | | | - Alois M. Wambua
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Hillary S. Young
- Department of Ecology, Evolution and Marine Biology; University of California; Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences; University of California; Davis California
- Mpala Research Centre; Nanyuki Kenya
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23
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Coggan NV, Hayward MW, Gibb H. A global database and "state of the field" review of research into ecosystem engineering by land animals. J Anim Ecol 2018; 87:974-994. [PMID: 29488217 DOI: 10.1111/1365-2656.12819] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 01/17/2018] [Indexed: 01/17/2023]
Abstract
Ecosystem engineers have been widely studied for terrestrial systems, but global trends in research encompassing the range of taxa and functions have not previously been synthesised. We reviewed contemporary understanding of engineer fauna in terrestrial habitats and assessed the methods used to document patterns and processes, asking: (a) which species act as ecosystem engineers and with whom do they interact? (b) What are the impacts of ecosystem engineers in terrestrial habitats and how are they distributed? (c) What are the primary methods used to examine engineer effects and how have these developed over time? We considered the strengths, weaknesses and gaps in knowledge related to each of these questions and suggested a conceptual framework to delineate "significant impacts" of engineering interactions for all terrestrial animals. We collected peer-reviewed publications examining ecosystem engineer impacts and created a database of engineer species to assess experimental approaches and any additional covariates that influenced the magnitude of engineer impacts. One hundred and twenty-two species from 28 orders were identified as ecosystem engineers, performing five ecological functions. Burrowing mammals were the most researched group (27%). Half of all studies occurred in dry/arid habitats. Mensurative studies comparing sites with and without engineers (80%) were more common than manipulative studies (20%). These provided a broad framework for predicting engineer impacts upon abundance and species diversity. However, the roles of confounding factors, processes driving these patterns and the consequences of experimentally adjusting variables, such as engineer density, have been neglected. True spatial and temporal replication has also been limited, particularly for emerging studies of engineer reintroductions. Climate change and habitat modification will challenge the roles that engineers play in regulating ecosystems, and these will become important avenues for future research. We recommend future studies include simulation of engineer effects and experimental manipulation of engineer densities to determine the potential for ecological cascades through trophic and engineering pathways due to functional decline. We also recommend improving knowledge of long-term engineering effects and replication of engineer reintroductions across landscapes to better understand how large-scale ecological gradients alter the magnitude of engineering impacts.
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Affiliation(s)
- Nicole V Coggan
- Department of Zoology, School of Life Sciences, La Trobe University, Melbourne, VIC., Australia
| | - Matthew W Hayward
- Australian Wildlife Conservancy, Subiaco East, W.A., Australia.,School of the Environment, Bangor University, Wales, UK
| | - Heloise Gibb
- Department of Zoology, School of Life Sciences, La Trobe University, Melbourne, VIC., Australia
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24
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Titcomb G, Allan BF, Ainsworth T, Henson L, Hedlund T, Pringle RM, Palmer TM, Njoroge L, Campana MG, Fleischer RC, Mantas JN, Young HS. Interacting effects of wildlife loss and climate on ticks and tick-borne disease. Proc Biol Sci 2018; 284:rspb.2017.0475. [PMID: 28878055 DOI: 10.1098/rspb.2017.0475] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/24/2017] [Indexed: 01/18/2023] Open
Abstract
Both large-wildlife loss and climatic changes can independently influence the prevalence and distribution of zoonotic disease. Given growing evidence that wildlife loss often has stronger community-level effects in low-productivity areas, we hypothesized that these perturbations would have interactive effects on disease risk. We experimentally tested this hypothesis by measuring tick abundance and the prevalence of tick-borne pathogens (Coxiella burnetii and Rickettsia spp.) within long-term, size-selective, large-herbivore exclosures replicated across a precipitation gradient in East Africa. Total wildlife exclusion increased total tick abundance by 130% (mesic sites) to 225% (dry, low-productivity sites), demonstrating a significant interaction of defaunation and aridity on tick abundance. When differing degrees of exclusion were tested for a subset of months, total tick abundance increased from 170% (only mega-herbivores excluded) to 360% (all large wildlife excluded). Wildlife exclusion differentially affected the abundance of the three dominant tick species, and this effect varied strongly over time, likely due to differences among species in their host associations, seasonality, and other ecological characteristics. Pathogen prevalence did not differ across wildlife exclusion treatments, rainfall levels, or tick species, suggesting that exposure risk will respond to defaunation and climate change in proportion to total tick abundance. These findings demonstrate interacting effects of defaunation and aridity that increase disease risk, and they highlight the need to incorporate ecological context when predicting effects of wildlife loss on zoonotic disease dynamics.
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Affiliation(s)
- Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA .,Mpala Research Centre, Box 555, Nanyuki, Kenya
| | - Brian F Allan
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Tyler Ainsworth
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Lauren Henson
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Tyler Hedlund
- Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Robert M Pringle
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Todd M Palmer
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Laban Njoroge
- Invertebrate Zoology Section, National Museums of Kenya, Nairobi, Kenya
| | - Michael G Campana
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Robert C Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | | | - Hillary S Young
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA.,Mpala Research Centre, Box 555, Nanyuki, Kenya
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25
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Palmer TM, Riginos C, Damiani RE, Morgan N, Lemboi JS, Lengingiro J, Ruiz-Guajardo JC, Pringle RM. Influence of neighboring plants on the dynamics of an ant-acacia protection mutualism. Ecology 2017; 98:3034-3043. [DOI: 10.1002/ecy.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 07/10/2017] [Accepted: 08/18/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Todd M. Palmer
- Department of Biology; University of Florida; Gainesville Florida USA
- Mpala Research Centre; Nanyuki Kenya
| | - Corinna Riginos
- Mpala Research Centre; Nanyuki Kenya
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming USA
| | - Rachel E. Damiani
- Department of Biology; University of Florida; Gainesville Florida USA
- Mpala Research Centre; Nanyuki Kenya
| | - Natalya Morgan
- Department of Biology; University of Florida; Gainesville Florida USA
- Mpala Research Centre; Nanyuki Kenya
| | | | | | - Juan C. Ruiz-Guajardo
- Mpala Research Centre; Nanyuki Kenya
- Department of Evolution and Ecology; University of California at Davis; Davis California USA
| | - Robert M. Pringle
- Mpala Research Centre; Nanyuki Kenya
- Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey USA
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26
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Beppler C, Tekin E, Mao Z, White C, McDiarmid C, Vargas E, Miller JH, Savage VM, Yeh PJ. Uncovering emergent interactions in three-way combinations of stressors. J R Soc Interface 2017; 13:rsif.2016.0800. [PMID: 27974577 DOI: 10.1098/rsif.2016.0800] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 11/23/2016] [Indexed: 11/12/2022] Open
Abstract
Understanding how multiple stressors interact is needed to predict the dynamical outcomes of diverse biological systems, ranging from drug-resistant pathogens that are combated and treated with combination drug therapies to ecosystems impacted by environmental toxicants or disturbances. Nevertheless, extensive studies of higher-order (more than two component) interactions have been lacking. Here, we conduct experiments using 20 three-drug combinations and their effects on the bacterial growth of Escherichia coli We report our measurements of growth rates in single, pairwise and triple-drug combinations. To uncover emergent interactions, we derive a simple framework to calculate expectations for three-way interactions based on the measured impact of each individual stressor and of each pairwise interaction. Using our framework, we find that (i) emergent antagonisms are more common than emergent synergies and (ii) emergent antagonisms are more common and emergent synergies are more rare than would be inferred from measures of net effects that do not disentangle pairwise interactions from three-way interactions.
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Affiliation(s)
- Casey Beppler
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.,Department of Microbiology, Immunology, and Molecular Genetics, The Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Elif Tekin
- Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhiyuan Mao
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.,Department of Microbiology, Immunology, and Molecular Genetics, The Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Cynthia White
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
| | - Cassandra McDiarmid
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
| | - Emily Vargas
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
| | - Jeffrey H Miller
- Department of Microbiology, Immunology, and Molecular Genetics, The Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Van M Savage
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.,Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.,Santa Fe Institute, Santa Fe, NM 87501, USA
| | - Pamela J Yeh
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
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27
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Coverdale TC, Kartzinel TR, Grabowski KL, Shriver RK, Hassan AA, Goheen JR, Palmer TM, Pringle RM. Elephants in the understory: opposing direct and indirect effects of consumption and ecosystem engineering by megaherbivores. Ecology 2017; 97:3219-3230. [PMID: 27870025 DOI: 10.1002/ecy.1557] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/20/2016] [Accepted: 06/13/2016] [Indexed: 11/10/2022]
Abstract
Positive indirect effects of consumers on their resources can stabilize food webs by preventing overexploitation, but the coupling of trophic and non-trophic interactions remains poorly integrated into our understanding of community dynamics. Elephants engineer African savanna ecosystems by toppling trees and breaking branches, and although their negative effects on trees are well documented, their effects on small-statured plants remain poorly understood. Using data on 117 understory plant taxa collected over 7 yr within 36 1-ha experimental plots in a semi-arid Kenyan savanna, we measured the strength and direction of elephant impacts on understory vegetation. We found that elephants had neutral effects on most (83-89%) species, with a similar frequency of positive and negative responses among the remainder. Overall, estimated understory biomass was 5-14% greater in the presence of elephants across a range of rainfall levels. Whereas direct consumption likely accounts for the negative effects, positive effects are presumably indirect. We hypothesized that elephants create associational refuges for understory plants by damaging tree canopies in ways that physically inhibit feeding by other large herbivores. As predicted, understory biomass and species richness beneath elephant-damaged trees were 55% and 21% greater, respectively, than under undamaged trees. Experimentally simulated elephant damage increased understory biomass by 37% and species richness by 49% after 1 yr. Conversely, experimentally removing elephant damaged branches decreased understory biomass by 39% and richness by 30% relative to sham-manipulated trees. Camera-trap surveys revealed that elephant damage reduced the frequency of herbivory by 71%, whereas we detected no significant effect of damage on temperature, light, or soil moisture. We conclude that elephants locally facilitate understory plants by creating refuges from herbivory, which countervails the direct negative effects of consumption and enhances larger-scale biomass and diversity by promoting the persistence of rare and palatable species. Our results offer a counterpoint to concerns about the deleterious impacts of elephant "overpopulation" that should be considered in debates over wildlife management in African protected areas: understory species comprise the bulk of savanna plant biodiversity, and their responses to elephants are buffered by the interplay of opposing consumptive and non-consumptive interactions.
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Affiliation(s)
- Tyler C Coverdale
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544, USA
| | - Tyler R Kartzinel
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544, USA
| | - Kathryn L Grabowski
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544, USA
| | - Robert K Shriver
- University Program in Ecology, Duke University, Durham, North Carolina, 27708, USA
| | | | - Jacob R Goheen
- Department of Zoology & Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Todd M Palmer
- Department of Biology, University of Florida, Gainesville, Florida, 32611, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544, USA
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Long RA, Wambua A, Goheen JR, Palmer TM, Pringle RM. Climatic variation modulates the indirect effects of large herbivores on small-mammal habitat use. J Anim Ecol 2017; 86:739-748. [PMID: 28342277 DOI: 10.1111/1365-2656.12669] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 03/07/2017] [Indexed: 11/29/2022]
Abstract
Large mammalian herbivores (LMH) strongly shape the composition and architecture of plant communities. A growing literature shows that negative direct effects of LMH on vegetation frequently propagate to suppress the abundance of smaller consumers. Indirect effects of LMH on the behaviour of these consumers, however, have received comparatively little attention despite their potential ecological significance. We sought to understand (i) how LMH indirectly shape small-mammal habitat use by altering the density and distribution of understorey plants; (ii) how these effects vary with climatic context (here, seasonality in rainfall); and (iii) the extent to which behavioural responses of small mammals are contingent upon small-mammal density. We tested the effects of a diverse LMH community on small-mammal habitat use using 4 years of spatially explicit small-mammal trapping and vegetation data from the UHURU Experiment, a replicated set of LMH exclosures in semi-arid Kenyan savanna. Small-mammal habitat use was positively associated with tree density and negatively associated with bare (unvegetated) patches in all plots and seasons. In the presence of LMH, and especially during the dry season, small mammals consistently selected tree cover and avoided bare patches. In contrast, when LMH were excluded, small mammals were weakly associated with tree cover and did not avoid bare patches as strongly. These behavioural responses of small mammals were largely unaffected by changes in small-mammal density associated with LMH exclusion. Our results show that LMH indirectly affect small-mammal behaviour, and that these effects are influenced by climate and can arise via density-independent mechanisms. This raises the possibility that anthropogenic LMH declines might interact with changing patterns of rainfall to alter small-mammal distribution and behaviour, independent of numerical responses by small mammals to these perturbations. For example, increased rainfall in East Africa (as predicted in many recent climate-model simulations) may relax constraints on small-mammal distribution where LMH are rare or absent, whereas increased aridity and/or drought frequency may tighten them.
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Affiliation(s)
- Ryan A Long
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Alois Wambua
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya
| | - Jacob R Goheen
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, WY, 82071, USA
| | - Todd M Palmer
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA.,Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya
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Pringle RM, Prior KM, Palmer TM, Young TP, Goheen JR. Large herbivores promote habitat specialization and beta diversity of African savanna trees. Ecology 2016; 97:2640-2657. [DOI: 10.1002/ecy.1522] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 06/16/2016] [Accepted: 06/22/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Robert M. Pringle
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
| | - Kirsten M. Prior
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Biology University of Florida Gainesville Florida 32611 USA
- Department of Biological Sciences Binghamton University State University of New York Binghamton, New York 13920 USA
| | - Todd M. Palmer
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Biology University of Florida Gainesville Florida 32611 USA
| | - Truman P. Young
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Plant Sciences University of California Davis California 95616 USA
| | - Jacob R. Goheen
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Zoology and Physiology University of Wyoming Laramie Wyoming 82070 USA
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Daskin JH, Pringle RM. Does primary productivity modulate the indirect effects of large herbivores? A global meta-analysis. J Anim Ecol 2016; 85:857-68. [PMID: 27007672 DOI: 10.1111/1365-2656.12522] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 03/11/2016] [Indexed: 12/13/2022]
Abstract
Indirect effects of large mammalian herbivores (LMH), while much less studied than those of apex predators, are increasingly recognized to exert powerful influences on communities and ecosystems. The strength of these effects is spatiotemporally variable, and several sets of authors have suggested that they are governed in part by primary productivity. However, prior theoretical and field studies have generated conflicting results and predictions, underscoring the need for a synthetic global analysis. We conducted a meta-analysis of the direction and magnitude of large mammalian herbivore-initiated indirect interactions using 67 published studies comprising 456 individual responses. We georeferenced 41 of these studies (comprising 253 responses from 33 locations on five continents) to a satellite-derived map of primary productivity. Because predator assemblages might also influence the impact of large herbivores, we conducted a similar analysis using a global map of large carnivore species richness. In general, LMH reduced the abundance of other consumer species and also tended to reduce consumer richness, although the latter effect was only marginally significant. There was a pronounced reduction in the strength of negative (i.e. suppressive, due e.g., to competition) indirect effects of LMH on consumer abundance in more productive ecosystems. In contrast, positive (facilitative) indirect effects were not significantly correlated with productivity, likely because these comprised a more heterogeneous array of mechanisms. We found no effect of carnivore species richness on herbivore-initiated indirect effect strength. Our findings help to resolve the fundamental problem of ecological contingency as it pertains to the strength of an understudied class of multitrophic interactions. Moreover, these results will aid in predicting the indirect effects of anthropogenic wildlife declines and irruptions, and how these effects might be mediated by climatically driven shifts in resource availability. To the extent that intact ungulate guilds help to suppress populations of small animals that act as agricultural pests and disease reservoirs, the negative impacts of large mammal declines on human well-being may be relatively stronger in low-productivity areas.
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Affiliation(s)
- Joshua H Daskin
- Department of Ecology and Evolutionary Biology, 106A Guyot Hall, Princeton University, Princeton, NJ, 08540, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, 106A Guyot Hall, Princeton University, Princeton, NJ, 08540, USA
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