33 million year old Myotis (Chiroptera, Vespertilionidae) and the rapid global radiation of modern bats

Abstract

The bat genus Myotis is represented by 120+ living species and 40+ extinct species and is found on every continent except Antarctica. The time of divergence of Myotis has been contentious as has the time and place of origin of its encompassing group the Vespertilionidae, the most diverse (450+ species) and widely distributed extant bat family. Fossil Myotis species are common, especially in Europe, beginning in the Miocene but earlier records are poor. Recent study of new specimens from the Belgian early Oligocene locality of Boutersem reveals the presence of a relatively large vespertilionid. Morphological comparison and phylogenetic analysis confirms that the new, large form can be confidently assigned to the genus Myotis, making this record the earliest known for that taxon and extending the temporal range of this extant genus to over 33 million years. This suggests that previously published molecular divergence dates for crown myotines (Myotis) are too young by at least 7 million years. Additionally, examination of first fossil appearance data of 1,011 extant placental mammal genera indicates that only 13 first occurred in the middle to late Paleogene (48 to 33 million years ago) and of these, six represent bats, including Myotis. Paleogene members of both major suborders of Chiroptera (Yangochiroptera and Yinpterochiroptera) include extant genera indicating early establishment of successful and long-term adaptive strategies as bats underwent an explosive radiation near the beginning of the Early Eocene Climatic Optimum in the Old World. A second bat adaptive radiation in the New World began coincident with the Mid-Miocene Climatic Optimum.

Diversification rates have no effect on the convergent evolution of foraging strategies in the most speciose genus of bats,Myotis*

“…Although uncertainty in the potential fossil calibration points makes it impossible to infer the exact timing of diversification in Myotis , this inference is consistent with fossils suggesting that Myotis ‐like lineages were present in Europe during the Rupelian at least since 33 million years ago (Gunnell et al. ). Divergence time estimates based on calibration using Gunnell's interpretation of the fossil record further suggest that diversification of Myotis reached its peak during the Early Miocene and Pliocene (between 23 and 3 million years ago), when continents were completing their drifts to their present locations but differed in important aspects, such as the separation of South and North America.…”

“…Horizontal bars within nodes represent 95% confidence intervals of divergence time estimates inferred by treePL using different calibration points according to Horacek (, blue bars) and Gunnell et al. (, pink bars). The scale at the bottom represents time in millions of years.…”

“…Gunnell et al. () compared their fossil description of M. belgicus with the extant species M. myotis , but did not include a full comparison with some of the Myotis ‐like fossils that once were considered true‐ Myotis . Given potential future scrutiny of M. belgicus due to its considerable older age that sets a huge gap in the fossil record of this group, we implement these two independent calibration approaches for divergence time estimates and discuss results of both scenarios.…”

“…Notably, Gunnell et al. () suggested that a fossil from Belgium ( Myotis belgicus ) and dated from at least 33 million years ago is the earliest true Myotis . If so, the initial divergence of Myotis predates the Early Oligocene and might not have occurred in East Asia.…”

Ecology and evolutionary biology of fishing bats

“…Due to the rapid radiation undergone by this genus (Gunnell et al. ), the phylogenetic relationship between species is not well established, although some preliminary studies exist (Stadelmann et al. , , Ruedi et al.…”