Abstract
Many claims that uplift of the Qinghai‐Tibetan plateau (QTP) drove the divergences of extant high‐elevation biota have recently been challenged. For Mendacibombus bumblebees, high‐elevation specialists with distributions centred on the QTP, we examine broader explanations. We extend integrative biogeography to cover multiple contributing factors by using a framework of sequential filters: 1) molecular evidence from four genes is used to estimate phylogenetic relationships, with time calibration from a published estimate; 2) spatial evidence from current distributions is combined with the phylogeny and constrained by a model of short‐distance dispersal along mountain corridors to estimate ancestral distributions by both S‐DIVA and S‐DEC analysis; 3) geological evidence from the literature is used to constrain when high mountain ranges were uplifted to become potential corridors; and 4) climatological evidence from Mendacibombus niche‐evolution reconstructions and from palaeoclimate simulations is used to constrain when habitat was suitable in key gaps within corridors. Explanations for Mendacibombus distributions can be identified that require only short‐distance dispersal along mountain corridors, commensurate with the limited dispersal ability observed for bumblebees. These explanations depend on the timing of uplift of mountain ranges, regional climate change, and climate‐niche evolution. The uplift of the QTP may have contributed to the initial Oligocene divergence of the common ancestor of Mendacibombus from other bumblebees, but for the first two thirds of the history of Mendacibombus, only a single lineage has present‐day descendants. Divergence of multiple extant Mendacibombus lineages coincided with the Late Miocene–Pliocene uplift of externally connecting mountains, combined with regional climate cooling. These changes provided greater connectivity of suitable habitat, allowing these bumblebees to disperse out of the western QTP via new high bridges, escaping along the mountain corridors of the Tian Shan and Hindu Kush ranges, reaching eventually far to the west (Iberian Peninsula) and to the north‐east (Kamchatka).
Highlights
Over the last decade there have been claims that divergence patterns in many groups of animals and plants have been driven by the high uplift of the Qinghai-Tibetan plateau (QTP), citing similar dates for both within the last 15 Ma (Favre et al 2015, Renner 2016)
Bumblebees are well suited to studies of distribution (Williams 1985, 1998) because: 1) they include a manageable number of species; 2) their distributions are well recorded because they are large, colourful and conspicuous, and active under similar conditions to field biologists; 3) the different species have similar behaviour and ecology as relative floral generalists, with many species co-occurring in the same habitats; and 4) they may be especially poor at long-distance dispersal and establishment, so that their indigenous distributions are not near equilibrium with the global distribution of potentially suitable habitat
Different nucleotidesubstitution models were used for different genes: the best model for our COI-barcode and 16S data according to the Bayesian information criterion (BIC) obtained from MEGA
Summary
Over the last decade there have been claims that divergence patterns in many groups of animals and plants have been driven by the high uplift of the Qinghai-Tibetan plateau (QTP), citing similar dates for both within the last 15 Ma (Favre et al 2015, Renner 2016). Growing geological evidence supports high uplift of the QTP as having occurred much earlier, before 45 Ma (Favre et al 2015, Renner 2016). We explore patterns of distribution and divergence in one group of specialist high-mountain bumblebees and its coincidence with mountain uplift and climate change in and around the QTP. For these cool-adapted insects, mountain chains, rather than representing barriers to dispersal as they do for some organisms, might act as corridors facilitating dispersal.
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