Heterogenization of remaining biodiversity in fragmented tropical forests across agricultural landscapes

Abstract

21The increasing worldwide interest on the conservation of tropical forests 22 reflects the conversion of over 50% of their area into agricultural lands and other uses. 23Understanding the distribution of remaining biodiversity across agricultural landscapes 24 is an essential task to guide future conservation strategies. To understand the long-25 term effects of fragmentation on biodiversity, we investigated whether forest fragments 26 in southeastern Brazil are under a taxonomic homogenization or heterogenization 27 process. We estimated pre-deforestation species richness and composition based on 28 a Species Distribution Modelling approach, and compared them to the observed 29 patterns of α-and β-diversity. In particular, we asked (i) if changes in β-diversity reveal 30 convergence or divergence on species composition; (ii) if these changes are similar 31 between forest fragments in Strictly Protected Areas (SPAs) (n=20) and within private 32 lands (n=367) and in different regions of the state (West, Center, and Southeast). We 33 detected steep reductions in observed local species richness in relation to our modeled 34 predictions, and this was particularly true among forest fragments in non-protected 35 private lands. The higher observed β diversity indicated an overall biotic 36 heterogenization process, consistent with the idea that the originally diverse 37vegetation is now reduced to small and isolated patches, with unique disturbance 38 histories and impoverished communities derived from a large regional species pool. 39Since conservation of biodiversity extends beyond the boundaries of strictly Protected 40 Areas, we advocate forest fragments are valuable for conservation in agricultural 41 landscapes, with particular relevance for private lands, which represent the most 42 exposed and neglected share of what is left. 43 44

Forest cover and connectivity have pervasive effects on the maintenance of evolutionary distinct interactions in seed dispersal networks

“…As demonstrated by others researchers, the forest reduction induce the downsizing of frugivores and seeds causing functional redundancy and loss of taxonomic, functional and phylogenetic biodiversity (Morante-Filho et al 2015, Pérez-Méndez et al 2015, McConkey and O'Farrill 2016, Emer et al 2018. The recently shown decrease in the representativeness of large-seeded plants in the remaining Atlantic Forest fragments (Lima et al 2020), and the high beta-diversity of the plant communities thriving in such forests (Vidal et al 2019) may be partially explained by such constraints and lend support to our findings. Areas with greater phylogenetic diversity of both plants and birds, as well as areas with more evolutionary distinct interactions, presented interaction networks with greater robustness.…”

Biotic homogenization and differentiation of plant communities in tropical and subtropical forests

“…Although some studies show a dominance of the homogenization process (Li et al, 2020;Lima et al, 2020;Lôbo et al, 2011;Tabarelli et al, 2012;Xu et al, 2019;Zwiener et al, 2018), others exhibit and sustain a process of differentiation or heterogenization (Collins et al, 2017;Sfair et al, 2016;Vidal et al, 2019). Our results support taxonomic homogenization as the most frequent process, and empirical evidence FIGURE 7 Anthropogenic disturbances reported as determinants of change and their percent contribution to homogenization and differentiation processes of plant communities in tropical and subtropical forests.…”

“…In our data set, homogenization was more frequently observed at large spatial scales, but the pattern was not clear, and we even observed idiosyncrasies of changes in community composition in tropical and subtropical forests (Hurtado‐M et al., 2020; Norden et al., 2015; Vidal et al., 2019). Although some studies reported homogenization at more local scales and differentiation at regional scales (Arroyo‐Rodríguez et al., 2013; Laurance et al., 2007; Sfair et al., 2016; Solar et al., 2015), others reported the opposite pattern (local differentiation and regional homogenization) (Andrade et al., 2015; Danneyrolles et al., 2020).…”

“…BD is a process that results in divergence in community composition (decreased community similarity) and an increase in beta diversity over time and space (Olden & Poff, 2003; Olden & Rooney, 2006). The process of BD is associated with anthropogenic factors such as land‐use changes, differences in disturbances regime (e.g., disturbance history and intensity), and natural factors such as dispersal limitation and environmental heterogeneity (Collins et al., 2017; Laurance et al., 2007; Sfair et al., 2016; Vidal et al., 2019).…”

Dynamic virtual ecosystems as a tool for detecting large-scale responses of biodiversity to environmental and land-use change

“…There is already some evidence in the literature of increased biotic homogenization as a result of climate change, for example, a study of plants in the Atlantic Forest (Zwiener et al, 2018), and of the converse biotic heterogenization in areas of habitat loss, e.g. deforestation in Brazilian tropical rainforests (Vidal et al, 2019). However, as climate and land-use changes will happen in tandem in some parts of the world, it remains to be seen how effective beta diversity measures would be at detecting changes in species composition given two conflicting drivers such as these.…”