Biogeographic deconstruction of phylogenetic and functional diversity provides insights into the formation of regional assemblages

Abstract

Evolutionary history and environmental filtering shape the phylogenetic and functional structure of regional assemblages. However, detecting the footprint of such eco-evolutionary drivers is challenging because these may often counter each other's signature. Here, we examined whether a biogeographic deconstruction approach of phylogenetic (PD) and functional diversity (FD) patterns may help in identifying ecoevolutionary signals in extant regional assemblages. As model system, we used forest understorey angiosperms found in three regions of Italy (Alpine, Mediterranean, Continental). We quantified PD and FD of all species inhabiting the three regions (regional assemblages). Then, we computed PD and FD for the subsets of species restricted to each region (biogeographic elements), also examining diversity patterns of species found across the three regions (widespread element). We used aboveground and belowground traits capturing major plant functions to calculate FD. Additionally, we assessed FD patterns decoupled from phylogeny. We found that species restricted to climatically harsh regions (Alpine and Mediterranean elements) were phylogenetically and functionally clustered, whereas widespread species were characterised by overdispersion. Species confined to the climatically intermediate (Continental) region were randomly sorted. By including all species occurring within a region, the patterns found for the region-restricted species blurred. Phylogenetically decoupled FD patterns were qualitatively similar to non-decoupled ones with the exception of the Alpine element, where we detected a clear signature of functional differentiation between closely related species. This suggests that recent speciation events contributed to shaping the Alpine flora. Compared to the belowground compartment, aboveground traits showed a more coherent pattern with that of all-trait FD -likely because most biomass is allocated aboveground in forest understoreys. This biogeographic deconstruction study illustrates which type of eco-evolutionary insights can be gained by implementing multifaceted and integrated approaches at the macroecological scale.

Are Mediterranean Island Mountains Hotspots of Taxonomic and Phylogenetic Biodiversity? The Case of the Endemic Flora of the Balearic Islands

“…We found that the phylogenetic diversity (PD) was highly correlated, and showed a similar geographical pattern to that of the RE (r = 0.72; Figures S3 and S4 ). The correlation between the PD and RE is a common pattern [ 14 , 24 , 26 , 33 , 88 , 89 , 90 ] but, as other studies pointed out [ 19 , 26 , 91 ], the PE and sesPD were not highly correlated with the RE (r = 0.50 and 0.23, respectively; Figure S3 ), and the sesPD was not correlated with the PD (r = 0.38; Figure S3 ), but was more correlated with the PE (r = 0.69; Figure S3 ), because the PE accounts for the spatial distribution of the species, and the sesPD is standardised according to species diversity. Hence, areas of high species richness are not always areas with a high phylogenetic diversity or phylogenetic endemism [ 26 ].…”

Functional and phylogenetic β diversities and their link with clustering/overdispersion and uniqueness/redundancy

“…Usually clustering/overdispersion patterns are not identified over a whole studied region but within each local area in reference to a large delimited region (e.g., Molina-Venegas et al, 2022; Ramm et al, 2018; Rocha et al, 2019; Yang et al, 2014). Their identification has so far required the use of null models and randomization of species occurrences or FP characteristics (e.g., Hardy & Senterre, 2007; Webb et al, 2002).…”

Diversity of endemic cold‐water amphipods threatened by climate warming in northwestern China

“…The randomization procedure was repeated 9999 times to compare if a significant difference existed between observed and random PD (Borko et al., 2022). Values of sesPD >1.96 indicate a significantly higher PD than expected (random PD) at a given level of species richness, and values below −1.96 indicate a significantly lower PD (Molina‐Venegas et al., 2022). Faith's PD and sesPD were implemented in the ‘picante’ R package (Kembel et al., 2010).…”