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Subramanian A, Germain RM. Landscape use by large grazers in a grassland is restructured by wildfire. PLoS One 2024; 19:e0297290. [PMID: 38349917 PMCID: PMC10863880 DOI: 10.1371/journal.pone.0297290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 01/02/2024] [Indexed: 02/15/2024] Open
Abstract
Animals navigate landscapes based on perceived risks vs. rewards, as inferred from features of the landscape. In the wild, knowing how strongly animal movement is directed by landscape features is difficult to ascertain but widespread disturbances such as wildfires can serve as natural experiments. We tested the hypothesis that wildfires homogenize the risk/reward landscape, causing movement to become less directed, given that fires reduce landscape complexity as habitat structures (e.g., tree cover, dense brush) are burned. We used satellite imagery of a research reserve in Northern California to count and categorize paths made primarily by mule deer (Odocoileus hemionus) in grasslands. Specifically, we compared pre-wildfire (August 2014) and post-wildfire (September 2018) image history layers among locations that were or were not impacted by wildfire (i.e., a Before/After Control/Impact design). Wildfire significantly altered spatial patterns of deer movement: more new paths were gained and more old paths were lost in areas of the reserve that were impacted by wildfire; movement patterns became less directed in response to fire, suggesting that the risk/reward landscape became more homogenous, as hypothesized. We found evidence to suggest that wildfire affects deer populations at spatial scales beyond their scale of direct impact and raises the interesting possibility that deer perceive risks and rewards at different spatial scales. In conclusion, our study provides an example of how animals integrate spatial information from the environment to make movement decisions, setting the stage for future work on the broader ecological implications for populations, communities, and ecosystems, an emerging interest in ecology.
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Affiliation(s)
- Aishwarya Subramanian
- Department of Biology, Irving K. Barber Faculty of Science, University of British Columbia Okanagan, Kelowna, BC, Canada
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Rachel M. Germain
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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2
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Sullivan LL, Shaw AK. Take me for a ride: Herbivores can facilitate plant reinvasions. Ecology 2023; 104:e4132. [PMID: 37376749 DOI: 10.1002/ecy.4132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 04/24/2023] [Accepted: 05/11/2023] [Indexed: 06/29/2023]
Abstract
Herbivores shape plant invasions through impacts on demography and dispersal, yet only demographic mechanisms are well understood. Although herbivores negatively impact demography by definition, they can affect dispersal either negatively (e.g., seed consumption), or positively (e.g., caching). Exploring the nuances of how herbivores influence spatial spread will improve the forecasting of plant movement on the landscape. Here, we aim to understand how herbivores impact how fast plant populations spread through varying impacts on plant demography and dispersal. We strive to determine whether, and under what conditions, we see net positive effects of herbivores, in order to find scenarios where herbivores can help to promote spread. We draw on classic invasion theory to develop a stage-structured integrodifference equation model that incorporates herbivore impacts on plant demography and dispersal. We simulate seven herbivore "syndromes" (combinations of demographic and/or dispersal effects) drawn from the literature to understand how increasing herbivore pressure alters plant spreading speed. We find that herbivores with solely negative effects on plant demography or dispersal always slow plant spreading speed, and that the speed slows monotonically as herbivore pressure increases. However, we also find that plant spreading speed can be hump shaped with respect to herbivore pressure: plants spread faster in the presence of herbivores (for low herbivore pressure) and then slower (for high herbivore pressure). This result is robust, occurring across all syndromes in which herbivores have a positive effect on plant dispersal, and is a sign that the positive effects of herbivores on dispersal can outweigh their negative effects on demography. For all syndromes we find that sufficiently high herbivore pressure results in population collapse. Thus, our findings show that herbivores can speed up or slow down plant spread. These insights allow for a greater understanding of how to slow invasions, facilitate native species recolonization, and shape range shifts with global change.
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Affiliation(s)
- Lauren L Sullivan
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA
- W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA
- Ecology, Evolution and Behavior Program, Michigan State University, East Lansing, Michigan, USA
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA
- Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota, USA
| | - Allison K Shaw
- Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota, USA
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Allbee SA, Rogers HS, Sullivan LL. The effects of dispersal, herbivory, and competition on plant community assembly. Ecology 2023; 104:e3859. [PMID: 36054771 PMCID: PMC10078099 DOI: 10.1002/ecy.3859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 06/14/2022] [Accepted: 06/30/2022] [Indexed: 02/01/2023]
Abstract
Dispersal is a key process in community assembly but is often considered separately from downstream assembly processes (e.g., competition, herbivory). However, dispersal varies by species and can interact with other assembly processes through establishment as species enter communities. Here, we sought to distinguish the role of dispersal in community assembly and its interaction with two biotic assembly processes: competition and herbivory. We used a tallgrass prairie restoration experiment that manipulated the competitive and herbivore environments while allowing for natural dispersal and establishment from a diverse regional species pool into areas of low diversity. Dispersal, competition, and herbivory all influenced local communities. By tracking the spread of four target species across the plots, we found interspecific and intraspecific differences in establishment patterns, with herbivores influencing the number of individuals present and the distances species moved. At the community level, only dispersal and competition significantly influenced alpha diversity, but all three processes additively influenced community composition. There was also evidence of herbivore-competition and herbivore-colonization trade-offs in our experiment. Some species that could tolerate herbivory were less likely to establish in competitive environments, while others that could tolerate herbivory were more likely to disperse greater distances. More work is needed to understand the contexts under which dispersal variation affects community assembly and its synergy with other processes.
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Affiliation(s)
- Samantha A Allbee
- Department of Ecology, Evolution, and Organismal Biology (EEOB), Iowa State University, Ames, Iowa, USA
| | - Haldre S Rogers
- Department of Ecology, Evolution, and Organismal Biology (EEOB), Iowa State University, Ames, Iowa, USA
| | - Lauren L Sullivan
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA.,Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA
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Guo G, Zhang Z, Zhang H, Bearup D, Liao J. Contrasting effects of dispersal network heterogeneity on ecosystem stability in rock-paper-scissors games. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.1068830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Intransitive competition, typically represented by the classic rock-paper-scissors game, provides an endogenous mechanism promoting species coexistence. As well known, species dispersal and interaction in nature might occur on complex patch networks, with species interacting in diverse ways. However, the effects of different interaction modes, combined with spatial heterogeneity in patch connectivities, have not been well integrated into our general understanding of how stable coexistence emerges in cyclic competition. We thus incorporate network heterogeneity into the classic rock-paper-scissors game, in order to compare ecosystem stability under two typical modes of interaction: species compete to fill empty sites, and species seize each other’s colony sites. On lattice-structured regular networks, the two interaction modes produce similar stability patterns through forming conspecific clusters to reduce interspecific competition. However, for heterogeneous networks, the interaction modes have contrasting effects on ecosystem stability. Specifically, if species compete for colony sites, increasing network heterogeneity stabilizes competitive dynamics. When species compete to fill empty sites, an increase in network heterogeneity leads to larger population fluctuations and therefore a higher risk of stochastic extinctions, in stark contrast to current knowledge. Our findings strongly suggest that particular attention should be devoted to testing which mode of interaction is more appropriate for modeling a given system.
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Zhang H, Bearup D, Nijs I, Wang S, Barabás G, Tao Y, Liao J. Dispersal network heterogeneity promotes species coexistence in hierarchical competitive communities. Ecol Lett 2020; 24:50-59. [PMID: 33029856 DOI: 10.1111/ele.13619] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/31/2020] [Accepted: 09/15/2020] [Indexed: 11/29/2022]
Abstract
Understanding the mechanisms of biodiversity maintenance is a fundamental issue in ecology. The possibility that species disperse within the landscape along differing paths presents a relatively unexplored mechanism by which diversity could emerge. By embedding a classical metapopulation model within a network framework, we explore how access to different dispersal networks can promote species coexistence. While it is clear that species with the same demography cannot coexist stably on shared dispersal networks, we find that coexistence is possible on unshared networks, as species can surprisingly form self-organised clusters of occupied patches with the most connected patches at the core. Furthermore, a unimodal biodiversity response to an increase in species colonisation rates or average patch connectivity emerges in unshared networks. Increasing network size also increases species richness monotonically, producing characteristic species-area curves. This suggests that, in contrast to previous predictions, many more species can co-occur than the number of limiting resources.
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Affiliation(s)
- Helin Zhang
- Ministry of Education's Key Laboratory of Poyang Lake Wetland and Watershed Research, School of Geography and Environment, Jiangxi Normal University, Nanchang, China
| | - Daniel Bearup
- School of Mathematics, Statistics and Actuarial Sciences, University of Kent, Canterbury, UK
| | - Ivan Nijs
- Research Group Plants and Ecosystems, Department of Biology, University of Antwerp, Wilrijk, Belgium
| | - Shaopeng Wang
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing, China
| | - György Barabás
- Division of Theoretical Biology, Department IFM, Linköping University, Linköping, Sweden.,MTA-ELTE Theoretical Biology and Evolutionary Ecology Research Group, Budapest, Hungary
| | - Yi Tao
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Jinbao Liao
- Ministry of Education's Key Laboratory of Poyang Lake Wetland and Watershed Research, School of Geography and Environment, Jiangxi Normal University, Nanchang, China
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Yan H, Feng L, Zhao Y, Feng L, Zhu C, Qu Y, Wang H. Predicting the potential distribution of an invasive species, Erigeron canadensis L., in China with a maximum entropy model. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2019.e00822] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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Morris MM, Frixione NJ, Burkert AC, Dinsdale EA, Vannette RL. Microbial abundance, composition, and function in nectar are shaped by flower visitor identity. FEMS Microbiol Ecol 2020; 96:5700281. [DOI: 10.1093/femsec/fiaa003] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 01/08/2020] [Indexed: 11/12/2022] Open
Abstract
ABSTRACT
Microbial dispersal is essential for establishment in new habitats, but the role of vector identity is poorly understood in community assembly and function. Here, we compared microbial assembly and function in floral nectar visited by legitimate pollinators (hummingbirds) and nectar robbers (carpenter bees). We assessed effects of visitation on the abundance and composition of culturable bacteria and fungi and their taxonomy and function using shotgun metagenomics and nectar chemistry. We also compared metagenome-assembled genomes (MAGs) of Acinetobacter, a common and highly abundant nectar bacterium, among visitor treatments. Visitation increased microbial abundance, but robbing resulted in 10× higher microbial abundance than pollination. Microbial communities differed among visitor treatments: robbed flowers were characterized by predominant nectar specialists within Acetobacteraceae and Metschnikowiaceae, with a concurrent loss of rare taxa, and these resulting communities harbored genes relating to osmotic stress, saccharide metabolism and specialized transporters. Gene differences were mirrored in function: robbed nectar contained a higher percentage of monosaccharides. Draft genomes of Acinetobacter revealed distinct amino acid and saccharide utilization pathways in strains isolated from robbed versus pollinated flowers. Our results suggest an unrecognized cost of nectar robbing for pollination and distinct effects of visitor type on interactions between plants and pollinators. Overall, these results suggest vector identity is an underappreciated factor structuring microbial community assembly and function.
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Affiliation(s)
- Megan M Morris
- Department of Biology, San Diego State University, San Diego, CA 92182, USA
- Department of Entomology and Nematology, University of California, Davis, Davis, CA 95616, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Natalie J Frixione
- Department of Biology, San Diego State University, San Diego, CA 92182, USA
| | - Alexander C Burkert
- Department of Entomology and Nematology, University of California, Davis, Davis, CA 95616, USA
| | | | - Rachel L Vannette
- Department of Entomology and Nematology, University of California, Davis, Davis, CA 95616, USA
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