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Differential speciation rates, colonization time, and niche conservatism affect community assembly across adjacent biogeographical regions

Citation

Benício, Ronildo et al. (2021), Differential speciation rates, colonization time, and niche conservatism affect community assembly across adjacent biogeographical regions, Dryad, Dataset, https://doi.org/10.5061/dryad.sf7m0cg65

Abstract

Aim: To test the importance of evolutionary and biogeographic processes in shaping the assembly of local frog communities in two adjacent regions (hereafter, coastal and inland regions) with different historical signatures. We asked two main questions: i) why does the coastal region harbor more frog species than the inland region? and ii) how do these processes affect the relationship between the spatial variation of taxonomic, phylogenetic, and functional diversities within and across these regions? 

Location: southeastern Brazil Taxon: Anurans

Methods: We generated time-calibrated phylogenies to estimate the relative timing of colonization, rates of speciation, extinction, and dispersal between regions. We tested the phylogenetic signal in reproductive modes. These traits were also used to examine variation in functional composition across sites. We calculated metrics of phylogenetic community structure that capture the relationships near the root and tips of the tree. Finally, we tested the relationships between the spatial variation of multiple diversity dimensions and topographic complexity, Pleistocene and contemporary climate gradients for three spatial extents: (i) only coastal sites; (ii) only inland sites; and (iii) the two regions combined.

Results: The structure of communities was related to the region in which they are located, with regional pool size being two times greater for the coastal than inland region. This pattern seems to reflect both a higher speciation rate and earlier colonization time in the coastal than in the inland region. Reproductive modes within frog genera were less variable than among families, indicating phylogenetic signal. This pattern influenced local community assembly within the inland region due to the absence of species with direct development, tadpoles in bromeliads, or eggs and tadpoles in streams in this region.

Main Conclusions: Macroevolutionary dynamics, such as colonization time, differences in speciation rates, and niche conservatism generate the disparity in species richness and assembly patterns of local communities between regions, but not within regions, in which local communities were more similar to each other.

Methods

We collected frog species presence-absence data in 14 protected areas, spanning 4° of latitude and 6° of longitude and encompassing a spatial extent of 98,000 km2 in southeastern Brazil. Seven of these protected areas are within the inland region encompassing a spatial extent of ~19,400 km2, with an average linear geographic distance of 152.5 ± 86.5 km between areas. Data on reproductive modes of frogs were obtained from Haddad, Toledo, Prado, Loebmann, & Gasparini (2013). We downloaded climatic variables from WorldClim v. 2.0 (Fick & Hijmans, 2017; http://www.worldclim.org).

Funding

Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: #2015/11821-0, #2013/50714-0, #2013/50741-7, and #2017/26162-8

Conselho Nacional de Desenvolvimento Científico e Tecnológico, Award: #142120/2015-4

Academy of Finland, Award: #331957