Empirical evaluation of the strength of interspecific competition in shaping small mammal communities in fragmented landscapes

Sozio, Giulia; Mortelliti, Alessio

doi:10.1007/s10980-015-0286-1

Cited by 37 publications

(31 citation statements)

References 75 publications

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“…Competitive pressures among taxa may explain the varying responses across mesopredators in our study (Heske et al 1994), as chipmunks are a mediumsized rodent whose resource requirements likely overlap both deer mice and ground squirrels. Mesopredators in our system may therefore have somewhat complementary local distributions (Sozio and Mortelliti 2016), with deer mice and ground squirrels displacing chipmunks in more fragmented areas. Generalist species such as deer mice tend to thrive near human disturbance, often at the expense of more sensitive or specialist species which are unable to adapt as quickly to novel environments (Crooks 2002, Ceradini andChalfoun 2017).…”

Section: Discussionmentioning

confidence: 99%

Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

Sanders

Chalfoun

2019

Ecosphere

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Anthropogenic activities are changing landscapes and the context in which predator–prey dynamics evolved, thereby altering key ecological processes and community structure. Yet, the specific mechanisms underlying such changes are rarely understood. We tested whether a mesopredator release explained increased rodent density and concomitant predation of songbird nests near natural gas development. From 2015 to 2016, we surveyed apex predators (coyotes, badgers, raptors, and corvids) and measured apparent survival and perceived predation risk of deer mice (Peromyscus maniculatus; a primary nest predator), at 12 plots spanning a gradient of surface disturbance caused by energy development in Wyoming, USA. Additionally, we measured densities of three nest predators: deer mice, least chipmunks (Tamias minimus), and thirteen‐lined ground squirrels (Ictidomys tridecemlineatus). Contrary to the mesopredator release hypothesis, counts of apex predators and perceived predation risk of deer mice increased with surface disturbance from energy development, whereas apparent survival of mice decreased. Densities of mice and ground squirrels, however, increased with surface disturbance, despite increased predation pressure. We therefore rejected the mesopredator release hypothesis as a potential mechanism underlying altered trophic dynamics near energy development. Our results suggest that apex predator control measures would not benefit declining songbirds on natural gas fields. Rather, apex predator abundance may be regulated from the bottom‐up by rodents in this system. Our results corroborate a pattern showing weakened effects of mesopredator release in habitats modified by humans. Understanding how predator–prey dynamics may be altered in novel environments requires an understanding of how predators and prey alike respond to habitat change under different contexts.

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Section: Discussionmentioning

confidence: 99%

Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

Sanders

Chalfoun

2019

Ecosphere

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“…Although a fundamental component in niche theory (Chase and Leibold 2003), interspecific competition is rarely considered in habitat studies, with the focus remaining on behavior-based resource selection (Garshelis 2000, Morris 2003). Further, most empirical studies that have considered effects of competition have used species distribution models that provide little insight into demographic consequences of competition (Belant et al 2006, Sozio andMortelliti 2016).…”

Section: Discussionmentioning

confidence: 99%

Using spatially‐explicit capture–recapture models to explain variation in seasonal density patterns of sympatric ursids

2018

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Understanding how environmental factors interact to determine the abundance and distribution of animals is a primary goal of ecology, and fundamental to the conservation of wildlife populations. Studies of these relationships, however, often assume static environmental conditions, and rarely consider effects of competition with ecologically similar species. In many parts of their shared ranges, grizzly bears Ursus arctos and American black bears U. americanus have nearly complete dietary overlap and share similar life history traits. We therefore tested the hypothesis that density patterns of both bear species would reflect seasonal variation in available resources, with areas of higher primary productivity supporting higher densities of both species. We also hypothesized that interspecific competition would influence seasonal density patterns. Specifically, we predicted that grizzly bear density would be locally reduced due to the ability of black bears to more efficiently exploit patchy food resources such as seasonally abundant fruits. To test our hypotheses, we used detections of 309 grizzly and 597 black bears from two independent genetic sampling methods in spatially‐explicit capture–recapture (SECR) models. Our results suggest grizzly bear density was lower in areas of high black bear density during spring and summer, although intraspecific densities were also important, particularly during the breeding season. Black bears had lower densities in areas of high grizzly bear density in spring; however, density of black bears in early and late summer was best explained by primary productivity. Our results are consistent with the hypothesis that smaller‐bodied, more abundant black bears may influence the density patterns of behaviorally‐dominant grizzly bears through exploitative competition. We also suggest that seasonal variation in resource availability be considered in efforts to relate environmental conditions to animal density.

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“…Anthropogenic actions that separated still wide expanses of habitat, resulting in subdivisions, which would be considered large continuous habitat even for populations of wide-ranging large-bodied species, were not considered by us. Thus, habitat fragmentation may change or disrupt antagonistic and mutualistic interactions such as predation or parasitism (Kareiva 1987, Kruess and Tscharntke 2000, Bordes et al 2015, interspecific competition (Sozio and Mortelliti 2016), and pollination (Goverde et al 2002, Kolb 2008. Anthropogenic habitat fragmentation results also in reductions of population sizes, and an increase in the degree of isolation of the remaining populations (Saunders et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta‐analysis

et al. 2018

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Habitat loss and fragmentation are among the biggest threats to biodiversity. Anthropogenic habitat fragmentation leads to small and isolated remnant plant and animal populations. The combination of increased random genetic drift, inbreeding, and reduced gene flow may substantially reduce genetic variation of remnant populations. However, the magnitude of these responses may depend on several poorly understood factors including organism group, habitat type of both the fragment and the surrounding matrix, life-history traits, and time since fragmentation. We compiled data for 83 plant and 52 animal species and conducted a meta-analysis following best practices to evaluate how these factors mediate the effects of anthropogenic habitat fragmentation. We calculated 206 effect sizes as correlations between one of four measures of population-level genetic diversity and fragment area. All analyses were repeated using models of increasing complexity (traditional random-effects models, multilevel models accounting for non-independent data, and multilevel models additionally correcting for phylogenetic relatedness). We confirmed that anthropogenic habitat fragmentation has overall negative effects on genetic diversity of organisms. Our meta-analysis shows, however, that plant species responded in general stronger to fragmentation than animal species and that the largest negative impacts of fragmentation occurred in tropical and temperate forest fragments, surrounded by a non-forest matrix. In contrast, we found only weak responses in non-forest fragments. Genetic diversity measured as mean number of alleles (A) showed the strongest response to fragmentation. Expected heterozygosity (He) and percentage of polymorphic loci (PLP) showed similar but weaker responses. In contrast, our meta-analysis indicated that inbreeding (Fis) was not measurably affected by anthropogenic habitat fragmentation. Additionally, our models revealed that effects on genetic diversity became stronger with age of fragments: We found significant negative responses for fragments older than 50 yr but not for those more recently isolated. Our meta-analyses also showed that currently animals are underrepresented in the literature on genetic effects of anthropogenic fragmentation, as are certain geographical regions and habitat types. We expect that future field studies using state-of-the-art approaches will provide further evidence of negative genetic effects, which may reinforce the here reported patterns, even for groups not yet studied.

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Empirical evaluation of the strength of interspecific competition in shaping small mammal communities in fragmented landscapes

Cited by 37 publications

References 75 publications

Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

Using spatially‐explicit capture–recapture models to explain variation in seasonal density patterns of sympatric ursids

Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta‐analysis

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