Biogeography of western Mediterranean butterflies: combining turnover and nestedness components of faunal dissimilarity

Abstract

Aim Unpartitioned dissimilarity indices such as the Sørensen index (βsor) tend to categorize areas according to species number. The use of turnover indices, such as the Simpson index (βsimp), may lead to the loss of important information represented by the nestedness component (βnest). Recent studies have suggested the importance of integrating nestedness and turnover information. We evaluated this proposition by comparing biogeographical patterns obtained by unpartitioned (βsor) and partitioned indices (βsimp and βnest) on presence data of western Mediterranean butterflies. Location Western Mediterranean. Methods We assessed the regionalization of 81 mainland and island faunas according to partitioned and unpartitioned dissimilarity by using cluster analyses with the unweighted pair‐group method using arithmetic averages (UPGMA) combined with non‐metric multidimensional scaling (NMDS). We also carried out dissimilarity interpolation for βsor, βsimp, βnest and the βnest/βsor ratio, to identify geographical patterns of variation in faunal dissimilarity. Results When the unpartitioned βsor index was used, the clustering of sites allowed a clear distinction between insular and mainland species assemblages. Most islands were grouped together, irrespective of their mainland source, because of the dominant effect of their shared low richness. βsimp was the most effective index for clustering islands with their respective mainland source. βsimp clustered mainland sites into broader regions than clusters obtained using βsor. A comparison of regionalization and interpolation provided complementary information and revealed that, in different regions, the patterns highlighted by βsor could largely be determined either by nestedness or turnover. Main conclusions Partitioned and unpartitioned indices convey complementary information, and are able to reveal the influence of historical and ecological processes in structuring species assemblages. When the effect of nestedness is strong, the exclusive use of turnover indices can generate geographically coherent groupings, but can also result in the loss of important information. Indeed, various factors, such as colonization–extinction events, climatic parameters and the peninsular effect, may determine dissimilarity patterns expressed by the nestedness component.

Integrating three comprehensive data sets shows that mitochondrial DNA variation is linked to species traits and paleogeographic events in European butterflies

“…A similar regionalization was obtained by comparing butterfly communities in the same area (Dapporto, Fattorini, Vodă, Dincă, & Vila, ). The main difference between the assessment at community and intraspecific differentiation level refers to Sardinia, Corsica and the Balearic islands.…”

“…In the analysis at the community level, the considerable number of endemic species from Sardinia and Corsica determined a high contrast and resulted in a highly distinct group; the Balearics without any endemic butterfly species, appeared very similar to Iberia (Dapporto et al, ). In the assessment of genetic diversity, the Sardo‐Corsican endemics can only generate contrasts between Sardinia and Corsica (and Tuscan Islands) when they show distinct populations between these areas, as is often the case (Dapporto et al, ). Most of the pattern obtained with intraspecific genetic variation is instead encompassed by widespread species responsible for determining similarity/dissimilarity patterns among islands and mainland.…”

Dispersal modality determines the relative partitioning of beta diversity in spider assemblages on subtropical land‐bridge islands

“…With the methodological advantages of these partitioning frameworks, our understanding of the cryptic processes of diversity patterns in some taxa has improved at a broad range of spatial scales (e.g. Baselga et al ., ; Carvalho & Cardoso, ; Dapporto et al ., ; Wen et al ., ). However, most previous studies have been conducted at broad continental scales, and the mechanisms behind variation in species composition might be masked or confounded by, for example, strong local or regional effects (Ricklefs, ).…”

“…However, most previous studies have been conducted at broad continental scales, and the mechanisms behind variation in species composition might be masked or confounded by, for example, strong local or regional effects (Ricklefs, ). To date, few studies on the partitioning of beta diversity have been conducted in island systems (but see Dapporto et al ., ; Heiser et al ., ; Hirao et al ., ; Si et al ., ; Vodă et al ., ).…”

Multiscale partitioning of small mammal β‐diversity provides novel insights into the Quaternary faunal history of Qinghai–Tibetan Plateau and Hengduan Mountains

“…As a consequence of this decomposition approach, the historical scenarios of how beta diversity patterns formed in some taxa (e.g. global patterns of freshwater fishes and amphibians: Leprieur et al ., and Baselga et al ., ; European mammals: Svenning et al ., ; New World vertebrates: Dobrovolski et al ., ; and western Mediterranean butterflies: Dapporto et al ., ) were finely detailed. To date, only a small number of studies have focused on East Asia (e.g.…”