Plant β‐diversity in fragmented rain forests: testing floristic homogenization and differentiation hypotheses

Abstract

Summary1. Land-use change is the main driver of global biodiversity loss, but its relative impact on species turnover (b-diversity) across multiple spatial scales remains unclear. Plant communities in fragmented rain forests can undergo declines (floristic homogenization) or increases (floristic differentiation) in b-diversity. 2. We tested these alternative hypotheses analysing a large vegetation data base from a hierarchically nested sampling design (450 plots in 45 forest patches in 3 landscapes with different deforestation levels) at Los Tuxtlas rain forest, Mexico. Differences in b-diversity across spatial scales (i.e. among plots, among patches, and among landscapes) were analysed using multiplicative diversity decompositions of Hill numbers. 3. Plant b-diversity among plots within forest patches decreased in landscapes with higher deforestation levels, leading to floristic homogenization within patches. This homogenization process can be explained by the loss of rare and shade-tolerant plant species, and the recruitment and dominance of disturbance-adapted species, and can limit the accumulation of species (c-diversity) in landscapes with higher deforestation. 4. Nevertheless, the landscape with the highest deforestation level showed the highest floristic differentiation among patches. This landscape showed the greatest isolation distances between patches; a landscape spatial pattern that can limit the interchange of seeds (and species) between patches. Because the study patches are undergoing secondary succession following disturbances (e.g. logging, edge effects), different disturbance regimes and increased distance among patches could lead to higher b-diversity. 5. Synthesis. These findings indicate that patterns of floristic homogenization and differentiation depend on the landscape configuration and on the spatial scale of analysis. At the landscape scale, our results suggest that, in accordance with non-equilibrium dynamics and the landscape-divergence hypothesis, patches located in landscapes with different forest cover and different connectivity can experience contrasting successional pathways due to increasing levels of compositional differentiation between patches. These novel findings add further uncertainties to the maintenance of biodiversity in severely deforested tropical landscapes and have key ecological implications for biodiversity conservation planning.

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).…”

Diversity and indicator species in the cerrado biome, Brazil

“…Studies evaluating beta diversity for the Cerrado region are few and punctual (Felfili et al, 2004;Ferreira, 2006;Haidar et al, 2013). In tropical regions, similar studies focus on rainforests (Condit et al, 2002;Tuomisto et al, 2003;Davidar et al, 2007;Arroyo-Rodríguez et al, 2013).…”

Spatially Heterogeneous Perturbations Homogenize the Regulation of Insect Herbivores

“…This can directly affect the spatial turnover of herbivore species by dispersal constraints but can also affect it indirectly by limiting their resources and predators. Habitat loss, for example, can maximize either stochastic influences on plant community assembly (i.e., different plant communities on different islands due to random dispersal) or deterministic ones by favoring the same subsets of species with traits for long-distance colonization (Arroyo-Rodríguez et al 2013;Harvey and MacDougall 2014). Habitat loss can also modify predation pressure by concentrating predators in smaller remnant areas, creating predation-free patches via dispersal limitation (Kruess and Tscharntke 1994;Hein and Gillooly 2011), or reducing predator diversity on smaller patches because of food limitation (Holt 1997;Gravel et al 2011).…”