Taxonomic divergence and functional convergence in Iberian spider forest communities: Insights from beta diversity partitioning

Abstract

Aim:The main aims were to determine: (a) the relative contribution of species replacement and richness difference from components to overall taxonomic (TDβ) and functional (FDβ) beta diversity of spider communities; (b) the degree to which TDβ and FDβ components can be explained by the environmental or geographic predictors; (c) whether FDβ components were lower than expected given the underlying TDβ variation. Location:This study was carried out in 22 oak forest sites across the Iberian Peninsula. The area comprises two biogeographic regions, Eurosiberian (North) andMediterranean (Centre and South).Methods: Spiders were sampled using a standardized protocol. A species x traits matrix was constructed. Total taxonomic (TDβ total ) and total functional (FDβ total ) beta diversity were calculated, by pairwise comparisons, and partitioned into their replacement (β repl ) and richness difference (β rich ) components. Mantel tests were used to relate taxonomic and functional dissimilarity with environmental and geographic distances. A spatial eigenfunction model was constructed and the variation in TDβ and FDβ explained by environment and geographic predictors was quantified. Null models were used to test if FDβ was higher or lower than expected given TDβ.Results: β repl was the dominant component contributing to 84.2% and 72.8% for TDβ total and FDβ total , respectively. TDβ total and FDβ total (and their replacement components) were higher between-than within-biogeographic regions. TDβ total and TDβ repl were positively correlated with environmental and geographic distances, even when controlling for a biogeographic effect, but their functional counterparts were only correlated with environmental distance. Variation partitioning showed that pure environmental and spatially structured environmental effects had a small contribution to beta diversity, except for TDβ rich . The observed slopes of the regressions of FDβ total and FDβ repl in relation to environmental distance were slower than the null model expectations.Main Conclusions: Spider assemblage variation was mainly determined by the replacement, and not the net loss, of species and traits. TDβ was influenced by niche | 289 CARVALHO et AL.

Identifying the Drivers of Spatial Taxonomic and Functional Beta-Diversity of British Breeding Birds

“…Note the varying y-axis for each measure. Carvalho et al, 2020). However, we also found that the differences in species loss/gain between sites (as measured by nestedness resultant dissimilarity) were explained mostly by differences in climate, and to a lesser extent, land use.…”

“…For example, bird communities play an important role in providing services such as pollination, pest control, and carrion removal (Whelan et al, 2008;Wenny et al, 2011), which are critical services for humans and other taxa. Using a beta-diversity measure that incorporates species traits, and hence functionality, is therefore essential to gain a better understanding of biodiversity change and its consequences (Devictor et al, 2010;Jarzyna and Jetz, 2018;Tobias and Pigot, 2019;Carvalho et al, 2020).…”

Determinants of different facets of beta diversity in Mediterranean marine amphipods

“…Since taxon diversity intrinsically influences functional and phylogenetic diversity (Arnan et al 2017), we used null models to address whether FDβ and PDβ were significantly higher or lower with respect to a given TDβ. We therefore generated a null distribution of FDβ and PDβ by randomizing 1,000 times the species name along the functional and phylogenetic dendrograms (Swenson et al 2011, Carvalho et al 2019). This allowed keeping actual branch lengths and their distribution, while preserving the spatial structure of species in the system.…”

“…their functional diversity, FD) constitute a not negligible and complementary part of diversity (Webb et al 2002, Petchey and Gaston 2006, Graham and Fine 2008). For instance, distinct communities may be characterized by a high taxonomic divergence although showing high levels of functional convergence, signalling the replacement of species performing similar functions across sites (Carvalho et al 2019). Similarly, communities composed of phylogenetically related species may show high levels of traits divergence, as a signal of the influence of regional and historical processes on local community assembly (Ramm et al 2018).…”

“…Likewise, it is reasonable to expect that functional and phylogenetic beta diversity components will be correlated with their taxonomic counterparts along gradients. Given the dependence between the different facets of beta diversity, the degree to which functional and phylogenetic beta diversity are significantly higher (or lower) than expected with respect to a given taxonomic composition, can be interpreted as signal of their divergence (or convergence), while random values as signal of dispersal limitation (Swenson et al 2011, Carvalho et al 2019).…”