Quantifying factors for understanding why several small patches host more species than a single large patch

Deane, David C.; Nozohourmehrabad, Pembegul; Boyce, Scott; He, Fangliang

doi:10.1016/j.biocon.2020.108711

Cited by 22 publications

(34 citation statements)

References 52 publications

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“…While our method does not consider any long‐term implications of biotic relaxation on diversity, it is conceivable these initial patterns could become stronger over time, because post‐fragmentation processes would drive species to be more aggregated, a weaker form of biotic relaxation (He & Hubbell, 2013). This would likely further increase the relative number of species in groups of smaller patches, consistent with much empirical evidence (e.g., Deane et al., 2020; Fahrig, 2017, 2020; Quinn & Harrison, 1988; Simberloff & Gotelli, 1984). Similarly, our null models predict only total species number, not species composition, nor abundance.…”

Section: Discussionsupporting

confidence: 78%

“…This would likely further increase the relative number of species in groups of smaller patches, consistent with much empirical evidence (e.g., Deane et al, 2020;Fahrig, 2017Fahrig, , 2020Quinn & Harrison, 1988;Simberloff & Gotelli, 1984). Similarly, our null models predict only total species number, not species composition, nor abundance.…”

Section: Effects Of Subdivision On Diversity Patternssupporting

confidence: 86%

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A null model for quantifying the geometric effect of habitat subdivision on species diversity

Deane

Xing

Hui

et al. 2021

Global Ecol Biogeogr

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Aim To derive null models for the expected number of species shared among multiple samples or habitat patches, allowing exploration of the geometric effects of subdivision on species diversity. Location Global. Major taxa studied Predominantly sessile organisms. Methods The occurrence probability of a species in a subdivided area depends on its abundance and spatial pattern over a known habitat extent. The joint probability that two subareas share a species is the product of the probability of species occurrence in each subarea provided that the latter probability is independent. The sum of this probability over all species is the number of species the two subareas share, or zeta diversity of order 2. Generalizing from 2 to m subareas yields a null model for zeta diversity of order m. From zeta diversity, many metrics (e.g., beta and gamma diversity) for the m habitat patches can be calculated, revealing the effects of increasing habitat fragmentation. Results The null models show the geometric effects of subdivision depend on patterns of spatial distribution of species within a landscape and evenness of species abundance distribution. For aggregated assemblages, increasing subdivision decreases shared species, increases beta diversity and results in higher total species richness in subdivided habitat than an equal contiguous area. Main conclusions To correctly interpret diversity patterns in fragmented habitat the geometric effects of subdivision must be considered. Our models explain why fragmented habitat could have higher diversity than continuous habitat of equal area but predict a threshold patch‐size above which this will not occur (here c. 100 ha). Apparently positive diversity effects of subdivision, including more species in groups of small patches, are probable outcomes of spatial aggregation of assemblages. The shared species null models offer an analytical tool for exploring the geometric effects of subdivision on diversity while controlling for total habitat area.

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Section: Discussionsupporting

confidence: 78%

Section: Effects Of Subdivision On Diversity Patternssupporting

confidence: 86%

A null model for quantifying the geometric effect of habitat subdivision on species diversity

Deane

Xing

Hui

et al. 2021

Global Ecol Biogeogr

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“…predator-prey dynamics) and the surrounding environment (e.g. matrix habitat and connectivity Deane et al, 2020;Drakare et al, 2006;Ewers & Didham, 2006). The sites in our study represent benign habitat matrices (sensu Fahrig, 2020), in which the aquatic medium allows organisms to cross habitat boundaries from reef to sand patches and vice versa, as opposed to a hostile matrix (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Instead, accounting for reef configuration resulted in no residual patterns (Figure 5d), confirming that SLOSS was the main driver of the distinct communities. and presence-absence data in evaluating SLOSS dynamics (Deane et al, 2020).…”

Section: Community Compositionmentioning

confidence: 99%

Restoring marine ecosystems: Spatial reef configuration triggers taxon‐specific responses among early colonizers

Wilms

Nordfoss

Baktoft

et al. 2021

Journal of Applied Ecology

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1. The longstanding debate in conservation biology on the importance of single large or several small (SLOSS) habitats for preserving biodiversity remains highly relevant, given the ongoing degradation and loss of natural habitats world-wide.Restoration efforts are often constrained by limited resources, and insights from SLOSS studies therefore have important implications if restoration efforts can be optimized by manipulating the spatial configuration of restored habitats. Yet, the relevance of SLOSS for habitat restoration remains largely unexplored.2. Here, we report the effects of spatial reef configuration on early colonization of marine organisms after restoring boulder reef habitats. Reefs were restored in single large (SL) and several small (SS) designs in the western Baltic Sea, where century-long boulder extraction has severely degraded large reef areas and likely exacerbated regional declines in commercially important gadoids (Gadidae spp.).We sampled the field sites using remote underwater video systems in a beforeafter control-impact (BACI) design and obtained probabilistic inferences on restoration and SLOSS effects from Bayesian hierarchical models.3. Probabilities of a positive restoration effect were high (>95%) for gadoids, labrids and demersal gobies, moderate (60%-75%) for species richness and sand gobies, and low (<5%) for flatfish abundance. Notably, gadoid abundance increased 60-fold and 129-fold on average at SL and SS respectively. The species composition at restored reefs deviated from control sites, mainly driven by large-bodied piscivores.4. Spatial reef configuration had the strongest effect on small-bodied mesopredators, including gobies, which were more abundant at SS and driving distinct species assemblages between the reef designs. In addition to providing suitable conditions for reef species, results suggest that SS can also benefit soft-bottom taxa, possibly through a dispersed predator-mediated effect relative to SL. Synthesis and applications.This study demonstrates that boulder reef restoration can strongly promote the abundance of exploited gadoids (e.g. Atlantic cod) and is therefore a promising management tool to support top-down controls by | 2937

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“…decoupled habitat fragmentation from habitat loss; sensu Fahrig 2003, 2013, 2017, Hadley and Betts 2016). In the majority of studies successfully decoupling habitat fragmentation from habitat loss, single large habitat fragments are generally found to contain an equivalent or lesser number of species than sets of several small habitat fragments summing to an equivalent total area (Quinn and Harrison 1988, Fahrig 2003, 2013, 2017, 2020, Yaacobi et al 2007, MacDonald et al 2018a, b2018b, Deane et al 2020). Such comparisons contribute to the ongoing single‐large‐or‐several‐small (‘SLOSS') debate, addressing how finite conservation efforts should prioritize the area and configuration of fragmented habitat and nature reserves (Diamond 1975, Abele and Connor 1979, Ovaskainen 2002, Tjørve 2010).…”

Section: Introductionmentioning

confidence: 99%

Distinguishing effects of area per se and isolation from the sample‐area effect for true islands and habitat fragments

MacDonald

Deane

et al. 2021

Ecography

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The island species area relationship (ISAR) is an important tool for measuring variation in species diversity in variety of insular systems, from true‐island archipelagoes to fragmented terrestrial landscapes. However, it suffers from several limitations. For example, due to the sample‐area effect, positive relationships between species and area cannot be directly interpreted as evidence for deterministic effects of area per se. Additionally, richness‐based analyses may obscure species‐level responses to area and isolation that may better inform conservation practice. Here, we use random placement models to control for variation in abundance, occupancy and richness associated with the sample‐area effect, allowing deterministic effects of area and isolation, and how they vary with species' functional traits, to be resolved using linear mixed effects models. We demonstrate the utility of this approach using a butterfly assemblage persisting on a naturally fragmented landscape of lake islands. The ISAR did not significantly deviate from random placement in relation to island area, isolation or habitat diversity, supporting stochastic assembly consistent with the sample‐area effect. Such inferences support the habitat amount hypothesis, which prioritizes preserving the maximum amount of habitat irrespective of its degree of fragmentation. However, species‐level analyses demonstrated that species' abundances were significantly lower on both smaller and more isolated islands than what is predicted by the sample‐area effect. Moreover, effects of area per se were significantly greater for smaller, less mobile and rare species. Species' occurrences also significantly deviated from predictions of the sample‐area effect in relation to island isolation. Thus, our approach illustrates that richness‐based analyses not only result in incorrect inferences on mechanisms underlying ISARs, but also obscure important effects of area per se and isolation on individual species that vary with functional traits. We therefore suggest that these effects should not be solely inferred from richness‐based analyses, but rather evaluated on a species‐by‐species basis.

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Quantifying factors for understanding why several small patches host more species than a single large patch

Cited by 22 publications

References 52 publications

A null model for quantifying the geometric effect of habitat subdivision on species diversity

A null model for quantifying the geometric effect of habitat subdivision on species diversity

Restoring marine ecosystems: Spatial reef configuration triggers taxon‐specific responses among early colonizers

Distinguishing effects of area per se and isolation from the sample‐area effect for true islands and habitat fragments

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