Landscape configuration affects probability of apex predator presence and community structure in experimental metacommunities

Abstract Biodiversity is declining at an unprecedented rate, highlighting the urgent requirement for well-designed protected areas. Design tactics previously proposed to promote biodiversity include enhancing the number, connectivity, and heterogeneity of reserve patches. However, how the importance of these features changes depending on what the conservation objective is remains poorly understood. Here we use experimental landscapes containing ciliate protozoa to investigate how the number and heterogeneity in size of habitat patches, rates of dispersal between neighbouring patches, and mortality risk of dispersal across the nonhabitat ‘matrix’ interact to affect a number of diversity measures. We show that increasing the number of patches significantly increases γ diversity and reduces the overall number of extinctions, whilst landscapes with heterogeneous patch sizes have significantly higher γ diversity than those with homogeneous patch sizes. Furthermore, the responses of predators depended on their feeding specialism, with generalist predator presence being highest in a single large patch, whilst specialist predator presence was highest in several-small patches with matrix dispersal. Our evidence emphasises the importance of considering how top-down effects can drive community responses to patch configuration.

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Reintroduced wolves and hunting limit the abundance of a subordinate apex predator in a multi-use landscape

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2202 ◽

2020 ◽

Vol 287 (1938) ◽

pp. 20202202

Author(s):

L. Mark Elbroch ◽

Jake M. Ferguson ◽

Howard Quigley ◽

Derek Craighead ◽

Daniel J. Thompson ◽

...

Keyword(s):

Population Model ◽

Human Impacts ◽

Adult Survival ◽

Apex Predator ◽

Vital Rates ◽

Grey Wolf ◽

Apex Predators ◽

Negative Effects ◽

Top Down ◽

Species Abundances

Top-down effects of apex predators are modulated by human impacts on community composition and species abundances. Consequently, research supporting top-down effects of apex predators occurs almost entirely within protected areas rather than the multi-use landscapes dominating modern ecosystems. Here, we developed an integrated population model to disentangle the concurrent contributions of a reintroduced apex predator, the grey wolf, human hunting and prey abundances on vital rates and abundance of a subordinate apex predator, the puma. Increasing wolf numbers had strong negative effects on puma fecundity, and subadult and adult survival. Puma survival was also influenced by density dependence. Overall, puma dynamics in our multi-use landscape were more strongly influenced by top-down forces exhibited by a reintroduced apex predator, than by human hunting or bottom-up forces (prey abundance) subsidized by humans. Quantitatively, the average annual impact of human hunting on equilibrium puma abundance was equivalent to the effects of 20 wolves. Historically, wolves may have limited pumas across North America and dictated puma scarcity in systems lacking sufficient refugia to mitigate the effects of competition.

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Bottom-up regulates top-down: the effects of hybridization of grass endophytes on an aphid herbivore and its generalist predator

Oikos ◽

10.1111/j.1600-0706.2013.00690.x ◽

2014 ◽

Vol 123 (5) ◽

pp. 545-552 ◽

Cited By ~ 10

Author(s):

Susanna Saari ◽

Scott Richter ◽

Melissa Robbins ◽

Stanley H. Faeth

Keyword(s):

Generalist Predator ◽

Top Down ◽

Bottom Up

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Effect of landscape configuration and habitat quality on the community structure of waterbirds using a man-made habitat

European Journal of Wildlife Research ◽

10.1007/s10344-014-0854-8 ◽

2014 ◽

Vol 60 (6) ◽

pp. 875-883 ◽

Cited By ~ 17

Author(s):

Juan Manuel Pérez-García ◽

Esther Sebastián-González ◽

Karen Luisa Alexander ◽

José Antonio Sánchez-Zapata ◽

Francisco Botella

Keyword(s):

Community Structure ◽

Habitat Quality ◽

Landscape Configuration

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The effects of top–down versus bottom–up control on benthic coral reef community structure

Oecologia ◽

10.1007/s00442-009-1546-z ◽

2010 ◽

Vol 163 (2) ◽

pp. 497-507 ◽

Cited By ~ 131

Author(s):

Jennifer E. Smith ◽

Cynthia L. Hunter ◽

Celia M. Smith

Keyword(s):

Community Structure ◽

Coral Reef ◽

Top Down ◽

Bottom Up ◽

Coral Reef Community ◽

Reef Community

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Historic Changes in Lake Michigan Zooplankton Community Structure: The 1960s Revisited with Implications for Top-Down Control

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-192 ◽

1992 ◽

Vol 49 (8) ◽

pp. 1734-1749 ◽

Cited By ~ 19

Author(s):

Marlene S. Evans

Keyword(s):

Community Structure ◽

Lake Michigan ◽

Species Abundance ◽

Zooplankton Community ◽

Water Clarity ◽

Phosphorus Loading ◽

Top Down ◽

Zooplankton Community Structure ◽

The 1960S

Recent changes in the Lake Michigan ecosystem provide a benchmark against which to reevaluate historic data. During the 1960s, the alewife (Alosa pseudoharengus) population exploded and then crashed. Offshore zoo-plankton data for the summers of 1954, 1966, and 1968 provided evidence that variations in alewife abundance had a major effect on zooplankton community structure. Based on these observations, other researchers have hypothesized that increased and decreased phytoplankton abundances during the 1960s as recorded at the Chicago water filtration plant were due to top-down effects rather than to phosphorus loading. This argument is reevaluated using two approaches. First, from the relationship between interannual variability in alewife and zooplankton species abundance during the summers of 1954, 1966, 1968, 1977, 1982, and 1984–87, I conclude that the effects of alewife predation on zooplankton community structure during the 1960s are less clear then originally proposed. Second, from estimates of Daphnia spp. grazing rates, considerations of the source of the long-term phytoplankton data used to support the top-down argument, regional differences in phytoplankton, zooplankton and alewife abundance trends, and historic water clarity observations, I conclude that existing data are insufficient to support the top-down argument that long-term trends in phytoplankton abundance were primarily affected by fluctuations in alewife abundance.

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A review of bottom-up vs. top-down control of sponges on Caribbean fore-reefs: what’s old, what’s new, and future directions

PeerJ ◽

10.7717/peerj.4343 ◽

2018 ◽

Vol 6 ◽

pp. e4343 ◽

Cited By ~ 21

Author(s):

Joseph R. Pawlik ◽

Tse-Lynn Loh ◽

Steven E. McMurray

Keyword(s):

Community Structure ◽

Past Research ◽

Fish Predation ◽

Sponge Species ◽

Top Down ◽

Bottom Up ◽

Fore Reef ◽

The Past ◽

The Impact ◽

Hawksbill Turtles

Interest in the ecology of sponges on coral reefs has grown in recent years with mounting evidence that sponges are becoming dominant members of reef communities, particularly in the Caribbean. New estimates of water column processing by sponge pumping activities combined with discoveries related to carbon and nutrient cycling have led to novel hypotheses about the role of sponges in reef ecosystem function. Among these developments, a debate has emerged about the relative effects of bottom-up (food availability) and top-down (predation) control on the community of sponges on Caribbean fore-reefs. In this review, we evaluate the impact of the latest findings on the debate, as well as provide new insights based on older citations. Recent studies that employed different research methods have demonstrated that dissolved organic carbon (DOC) and detritus are the principal sources of food for a growing list of sponge species, challenging the idea that the relative availability of living picoplankton is the sole proxy for sponge growth or abundance. New reports have confirmed earlier findings that reef macroalgae release labile DOC available for sponge nutrition. Evidence for top-down control of sponge community structure by fish predation is further supported by gut content studies and historical population estimates of hawksbill turtles, which likely had a much greater impact on relative sponge abundances on Caribbean reefs of the past. Implicit to investigations designed to address the bottom-up vs. top-down debate are appropriate studies of Caribbean fore-reef environments, where benthic communities are relatively homogeneous and terrestrial influences and abiotic effects are minimized. One recent study designed to test both aspects of the debate did so using experiments conducted entirely in shallow lagoonal habitats dominated by mangroves and seagrass beds. The top-down results from this study are reinterpreted as supporting past research demonstrating predator preferences for sponge species that are abundant in these lagoonal habitats, but grazed away in fore-reef habitats. We conclude that sponge communities on Caribbean fore-reefs of the past and present are largely structured by predation, and offer new directions for research, such as determining the environmental conditions under which sponges may be food-limited (e.g., deep sea, lagoonal habitats) and monitoring changes in sponge community structure as populations of hawksbill turtles rebound.

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Top–down and bottom–up regulation of macroalgal community structure on a Kenyan reef

Estuarine Coastal and Shelf Science ◽

10.1016/j.ecss.2009.03.033 ◽

2009 ◽

Vol 84 (3) ◽

pp. 331-336 ◽

Cited By ~ 12

Author(s):

Erik Mörk ◽

Gustaf Lilliesköld Sjöö ◽

Nils Kautsky ◽

Tim R. McClanahan

Keyword(s):

Community Structure ◽

Top Down ◽

Bottom Up ◽

Macroalgal Community

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Viewing soil systems from the top-down can make microbial ecology predictive for ecosystem functions

10.5194/egusphere-egu2020-3414 ◽

2020 ◽

Author(s):

Johannes Rousk ◽

Lettice Hicks

Keyword(s):

Community Structure ◽

Microbial Community ◽

Microbial Communities ◽

Functional Response ◽

Community Composition ◽

Ecosystem Function ◽

Response Curve ◽

Ecosystem Processes ◽

Ecosystem Functions ◽

Top Down

<p>Understanding the role of ecological communities in maintaining multiple ecosystem processes is a central challenge in ecology. Soil microbial communities perform vital ecosystem functions, such as the decomposition of organic matter to provide plant nutrition. However, despite the functional importance of soil microorganisms, attribution of ecosystem function to particular constituents of the microbial community has been impeded by a lack of information linking microbial processes to community structure.</p><p>Here, we propose a new conceptual framework to determine how microbial communities influence ecosystem processes, by applying a &#8220;top-down&#8221; approach. Looking from the &#8220;top&#8221;, we first view the microbial community associated with a specific function as a whole, and describe the dependence of microbial community processes on environmental factors (e.g. the intrinsic temperature dependence of bacterial growth rates), allowing us to define the aggregate functional response curve of the community. We then demonstrate that the whole community contribution to ecosystem function can be predicted, by parameterising the functional response curve with current environmental conditions. In a final step, we show how this functional information can be linked to the taxonomic community composition (amplicon assessments of microbial community composition) in order to identify &#8220;biomarker&#8221; taxa that capture microbial communities&#8217; regulation of ecosystem processes and the susceptibility of microbial community structure and function to environmental change. Ultimately, these biomarkers may be used as a diagnostic tool, enabling predictions of ecosystem function from community composition information combined with environmental metadata.</p>

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