Unraveling the drivers of plant taxonomic and phylogenetic β-diversity in a human-modified tropical dry forest

Abstract

Biodiversity maintenance in human-modified landscapes largely depends on spatial variations in species composition (β-diversity), but the impact of human disturbance on β-diversity remains poorly understood. We examined how taxonomic and phylogenetic β-diversity of woody plant communities in the Brazilian Caatinga dry forest respond to two emerging threats-chronic anthropogenic disturbance and water scarcity. We separately assessed diversity metrics that give a disproportionate weight to rare species, and metrics weighted by dominant species. We recorded a total of 5118 individuals from 104 species across 19 0.1-ha plots into a 21,430-ha human-modified landscape exposed to chronic disturbances and a high variation in climatic water deficit. At the landscape scale, β-diversity was higher when considering rare species than when focusing on dominant species, especially for the phylogenetic dimension of β-diversity. Water deficit was the primary driver of plant taxonomic and phylogenetic β-diversity, followed by the number of cattle and inter-site isolation; however, rare species seem to depend more strongly on these factors than the dominant ones. Therefore, preserving as much forest as possible, including areas exposed to different disturbance level and climate variables, is critical to prevent the loss of rare species and maintain the compositional differentiation of biotic assemblages. Such forest cover should be maintained in a large number of forest patches scattered through the landscape to preserve biologically and functionally distinct components of this ecosystem, avoid landscape-scale biotic homogenization, and thus favor its ecological resilience.

Precipitation preferences alter the relative importance of herbaceous plant diversity for multifunctionality in the drylands of China

“…As such, it enables us to link local processes, such as biological interactions and environmental filtering, to more regional processes, including trait evolution, dispersal and species formation (Qian et al, 2021). Although species and functional beta diversity can effectively capture the amount of overlap in species composition or trait characteristics between sites (habitats, geographic regions), neither provides information on the depth of separation of these phylogenetic through evolutionary time (Rito et al, 2021). Therefore, it is necessary to consider the impact of phylogenetic beta diversity on ecosystem functioning.…”

Cross‐scale drivers of woody plant species commonness and rarity in the Brazilian drylands

“…desiccated) local conditions (Muller‐Landau, 2010; see Costa et al, 2020 and Trindade et al, 2020 for Caatinga examples). On the other hand, abiotic dispersal favours species occupancy across Caatinga dry forests particularly at larger spatial scales, where dispersal limitation is expected to be a more prominent driver of species distribution and community assembly (Asefa et al, 2020; Rito et al, 2021). The negative deviation for animal‐dispersed species from AORs at larger scales may reflect a dispersal failure due to severe level of defaunation and widespread extirpations of large‐bodied frugivore populations throughout the Caatinga (Bogoni et al, 2020).…”

Drivers of beta diversity along a precipitation gradient in tropical forests of the Cauca River Canyon in Colombia

“…We measured the effect of fragmentation as a distance corrected by the presence of forest cover that facilitated population connectivity (e.g., seed dispersal). However, this approach only includes the restriction for moving as a consequence of fragmentation; other processes related to forest degradation such as selective logging, microclimatic variation that influence seed establishment and the increase in ecological drift from fragmentation (Catano et al, 2017; Rito et al, 2021) were not measured in our analysis. All of these local factors may increase the variation among plots with similar climatic conditions.…”

“…Thus, distance measurements tracking suitable habitat (i.e., landscape resistance) could be more informative to explain compositional differences than geographic distance alone (e.g., Euclidean distance). Additionally, this effect could be stronger for taxonomic than phylogenetic turnover because particular species could be restricted to some patches but higher taxonomic levels (e.g., genera) could be retained across patches (Rito et al, 2021). Hence, the comparison of phylogenetic and taxonomic beta diversity with different distance metrics among communities will allow us to evaluate natural and anthropogenic factors that influence dispersal as a driver of community composition variation across space.…”