Contributions of biogeographical functions to species accumulation may change over time in refugial regions

Abstract

Aim Elevated biodiversity is the result of the cradle, museum or sink functions. The contributions of these three functions to species accumulation and their changes through time remain unknown for glacial refugia. Additionally, our understanding of the role these functions played during pre‐glacial periods is limited. We test for changes in contributions of functions through time leading to the current diversity patterns using a model refugium and taxon. Location Anatolia, Western Palaearctic. Taxon Freshwater neritid snails (genus Theodoxus). Methods Assessments were made to define molecular operational taxonomic units (MOTUs) for Theodoxus and reaffirm the genus as a suitable model taxon with elevated interspecific diversity in noted glacial refugia. Thereafter, we constructed a time‐calibrated multilocus Bayesian phylogeny of mtDNA and nDNA by using both fossil data and published substitution rates. Ancestral area estimation was performed on the phylogeny to define the contribution of the functions through time. Results Accumulation of Theodoxus diversity in Anatolia over the Miocene–Pliocene transition is attributed to the museum function, but its contribution was small as only few divergence events occurred. The cradle function dominated during the Pliocene and Early Pleistocene, when most interspecific diversity built up and extant lineages in Anatolia were established. The sink function acted from the Middle Pleistocene to present‐day, but with only a small contribution to the total extant Anatolian interspecific diversity. Main conclusion Our results do not entirely mitigate the role glacial cycles played in species accumulation, but highlight Ice Ages may have been less effective in forcing temperate aquatic interspecific diversity into more opportune areas. The elevated diversity in refugia may rather be the result of earlier in situ diversification. Elevated interspecific diversity attributed to the legacy of glacially forced retreats may need to be re‐evaluated in cases where refugia have long and complex geological histories such as Anatolia. These results highlight the importance of considering species accumulation through a temporal perspective to adequately explain present‐day biodiversity patterns.

A Late Miocene – Early Pliocene Paratethyan Type Ostracod Fauna From the Denizli Basin (Sw Anatolia) and Its Palaeogeographic Implications

“…The hypothesis that faunistic elements, which originated in Lake Pannon and spread through temporary connection during the Miocene and/or Pliocene, is also worth considering when studying the fossil remains inside the sedimentary lake deposits of the Denizli Basin. Previous taxonomic studies on the biota revealed the presence of Paratethyan faunas (molluscs and ostracods), indicating a close biogeographic affinity between SW Anatolia and the Paratethys, mainly Lake Pannon (Freels, 1980;Wesselingh et al, 2008;Şafak, 2010;Sands et al, 2019). The role of Anatolian basins as a source/sink-area of Paratethyan-like ostracod taxa, however remains to be established still.…”

A revision of the extant species of Theodoxus (Gastropoda, Neritidae) in Asia, with the description of three new species

“…Previously published phylogenetic relationships among species of Theodoxus are spread between a number of different studies (e.g. Bunje and Lindberg 2007;Sands et al 2019aSands et al , 2019b. These phylogenies still lack some commonly recognised morphospecies.…”

“…Presently, the phylogenetic species concept through molecular approaches has proved to be a reliable tool in substantiating species diversity in Theodoxus. Three studies have presented broad-scale phylogenetic outlooks on the interspecific diversity within Theodoxus (Bunje and Lindberg 2007;Sands et al 2019aSands et al , 2019b. These phylogenetic studies have greatly improved our understanding of the relationships among species and have supported the outcomes of some more recent and detailed morphological reviews (Alba et al 2016;Anistratenko et al 2017;Glöer 2018;Wesselingh et al 2019).…”

“…The majority of interspecific diversity in Theodoxus occurs within western Asia (Sands et al 2019a). The effects of tectonic history and past climatic changes have driven both ecological and geographical speciation, as well as immigration to this region (Sands et al 2019a). Previous studies have recognised many species of Theodoxus here (e.g.…”

“…These phylogenetic studies have greatly improved our understanding of the relationships among species and have supported the outcomes of some more recent and detailed morphological reviews (Alba et al 2016;Anistratenko et al 2017;Glöer 2018;Wesselingh et al 2019). While they have highlighted the need for revision and have indicated new species (see Sands et al 2019a), a taxonomic revision of Theodoxus is still pending.…”