Many islands are biodiversity hotspots that host numerous endemic species. Unfortunately, insular faunas suffer from high rates of extinction and endangerment, and numerous conservation plans have been developed for their protection. These conservation plans are often assessed on the basis of occurrence and proportion of endemic taxa. However, delimitations of species and subspecies are still confusing and controversial. From a practical point of view, these disagreements make it difficult for government agencies and non‐governmental organizations to initiate conservation measures. The present study develops a pragmatic integrative taxonomic approach on the basis of molecular and eco‐chemical criteria. This method is applied to the insular bumblebee fauna of Corsica. For each taxon, the differentiation of Corsican taxa from the nearest related allopatric parents is characterized using genetic markers and the chemical composition of cephalic labial gland secretions. Phylogenetic analyses, Bayesian implementation of the general mixed Yule‐coalescent approach, and comparative chemical studies show that two Corsican taxa can be considered as endemic species while five others can be considered as subspecies. Regardless of the taxonomic assessment the method facilitates diagnosis of evolutionarily significant units and rank taxa according to their distinctiveness. International Union for Conservation of Nature red lists are reconsidered according to the new taxonomic hypothesis for Corsican bumblebees. Modifications in species assessments are proposed. The present approach provides useful data sets for policy‐makers and conservation organizations.

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Abstract. Cold-adapted species are expected to have reached their largest distribution range during a part of the Ice Ages whereas postglacial warming has led to their range contracting toward high-latitude and high-altitude areas. This has resulted in an extant allopatric distribution of populations and possibly to trait differentiations (selected or not) or even speciation. Assessing inter-refugium differentiation or speciation remains challenging for such organisms because of sampling difficulties (several allopatric populations) and disagreements on species concept. In the present study, we assessed postglacial inter-refugia differentiation and potential speciation among populations of one of the most common arcto-alpine bumblebee species in European mountains, Bombus monticola Smith, 1849. Based on mitochondrial DNA/nuclear DNA markers and eco-chemical traits, we performed integrative taxonomic analysis to evaluate alternative species delimitation hypotheses and to assess geographical differentiation between interglacial refugia and speciation in arcto-alpine species. Our results show that trait differentiations occurred between most Southern European mountains (i.e. Alps, Balkan, Pyrenees, and Apennines) and Arctic regions. We suggest that the monticola complex actually includes three species: B. konradini stat.n. status distributed in Italy (Central Apennine mountains), B. monticola with five subspecies, including B. monticola mathildis ssp.n. distributed in the North Apennine mountains ; and B. lapponicus. Our results support the hypothesis that post-Ice Age periods can lead to speciation in cold-adapted species through distribution range contraction. We underline the importance of an integrative taxonomic approach for rigorous species delimitation, and for evolutionary study and conservation of taxonomically challenging taxa.

Bumblebees have been the focus of much research, but the taxonomy of many species groups is still unclear, especially for circumpolar species. Delimiting species based on multisource datasets provides a solution to overcome current systematic issues of closely related populations. Here, we use an integrative taxonomic approach based on new genetic and eco-chemical datasets to resolve the taxonomic status of Bombus lapponicus and Bombus sylvicola. Our results support the conspecific status of B. lapponicus and B. sylvicola and that the low gradual divergence around the Arctic Circle between Fennoscandia and Alaska does not imply speciation in this species complex. Therefore, based on our molecular and morphological analyses, we propose to assign them subspecific status: Bombus lapponicus lapponicus from Fennoscandia and West Siberia and Bombus lapponicus sylvicola comb. nov. from Alaska and Yukon. In addition, our analyses reveal a cryptic species in the B. lapponicus complex from Alaska, which we describe here as new: Bombus (Pyrobombus) interacti sp. nov.