Ecological filtering or random extinction? Beta‐diversity patterns and the importance of niche‐based and neutral processes following habitat loss

Abstract

Although both niche‐based and neutral processes are involved in community assembly, most models on the effects of habitat loss are stochastic, assuming neutral communities mainly affected by ecological drift and random extinction. Given that habitat loss is considered the most important driver of the current biodiversity crisis, unraveling the processes underlying the effects of habitat loss is critical from both a theoretical and an applied perspective. Here we unveil the importance of niche‐based and neutral processes to species extinction and community assembly across a gradient of habitat loss, challenging the predictions of neutral models. We draw on a large dataset containing the distribution of 3653 individuals of 42 species, representing 35% of the small mammal species of the Atlantic Forest hotspot, obtained in 68 sites across three continuously‐forested landscapes and three adjacent 10 000‐ha fragmented landscapes differing in the amount of remaining forest (50%, 30% and 10%). By applying a null‐model approach, we investigated β‐diversity patterns by detecting deviations of observed community similarity from the similarity between randomly assembled communities. Species extinction following habitat loss was decidedly non‐random, in contrast to the notion that fragmented communities are mainly driven by ecological drift. Instead, habitat loss led to a strong biotic homogenization. Moreover, species composition changed abruptly at the same level of landscape‐scale habitat loss that has already been associated with a drastic decline in species richness. Habitat loss, as other anthropogenic disturbances, can thus be seen as a strong ecological filter that increases (rather than decreases) the importance of deterministic processes in community assembly. As such, critical advances for the development of conservation science lie on the incorporation of the relevant niche traits associated with extinction proneness into models of habitat loss. The results also underscore the fundamental importance of pro‐active measures to prevent human‐modified landscapes surpassing critical ecological thresholds.

Landscape, Environmental and Social Predictors of Hantavirus Risk in São Paulo, Brazil

“…While O . nigripes is known to survive in small and isolated forest remnants [23; 79], and prefers early successional stages inside the forest [78; 79; 80], becoming more abundant in these landscapes, N . lasiurus seems to prefer less dense and open areas [43; 81], occurring in disturbed and open habitats [78].…”

“…This effect occurs because these species are generally habitat generalists [19; 20] that can tolerate and adapt to ecological changes [21], being favored in disturbed environments [6; 17] and becoming abundant in altered landscapes [19; 6; 22; 23]. In addition, greater population densities of these reservoir species increase intraspecific encounters and consequent Hantavirus transmission [20; 16].…”

Land-use effects on local biodiversity in tropical forests vary between continents

“…By favouring the establishment of ecologically-flexible or disturbance-tolerant species, at the expense of disturbance-intolerant endemics, they can cause biotic homogenization (McKinney and Lockwood 1999;Arroyo-Rodríguez et al 2013;Püttker et al 2015;de Solar et al 2015), i.e., an increase in similarity between communities in different places. We assess biotic homogenisation in two ways: first, by analysing compositional turnover (beta diversity) between pairs of sites (McKinney 2006;Devictor et al 2008;Karp et al 2012); and second, by using the distribution of species' range sizes at a site, with more disturbed sites predicted to be more dominated by wide-ranging species than more natural sites (Mandle and Ticktin 2013).…”

How Should Beta-Diversity Inform Biodiversity Conservation?

“…Habitat fragmentation can increase beta diversity via dispersal limitation and neutral processes [87]. Such patterns may indicate a need to increase betweenpatch connectivity via corridor creation [88].…”