Search

Myotis is the most speciose genus of mammals in the world and recent taxonomic revisions have revealed an impressive diversity of species in South America. Even so, the phenotypic conservatism of some taxa makes taxonomic delimitation difficult. We perform a taxonomic review of Myotis from Argentina based on qualitative and quantitative morphological characters. Our results confirm the occurrence of 12 species (M. albescens, M. chiloensis, M. dinellii, M. izecksohni, M. keaysi, M. lavali, M. levis, M. nigricans, M. oxyotus, M. riparius, M. ruber, and M. cf. simus) and revealed an additional new species for the Yungas Forest. The new species is small to medium (forearm length ~ 35 mm) and can be distinguished from its congeners by a set of characters that includes forearm length, cranial measurements, discrete craniodental characters, and fur color. This review does not exhaust the need for new systematic studies with Argentinean Myotis, considering the possibility of occurrence of new species and the great morphological variation found for some complex taxa.

Myotis comprises a diverse group of vespertilionid bats with worldwide distribution. Neotropical Myotis have an accentuated phenotypic conservatism, which makes species delimitation and identification difficult, hindering our understanding of the diversity, distribution, and phylogenetic relationships of taxa. To encourage new systematic reviews of the genus, a catalogue of the primary types and names is presented, current and in synonymy, for Neotropical Myotis. Currently 33 valid species (and three subspecies) are recognized, and their primary types are deposited in 12 scientific collections in the USA (30 types), Brazil (two types), England (two types), and France (one type). The names of 29 Neotropical Myotis species currently in synonymy were found. However, it is possible that some synonyms represent independent evolutionary lineages, considering recent results provided by taxonomic revisions.

Abstract The genus Myotis comprises a diverse group of vesper bats with worldwide distribution. Twenty-eight neotropical species are currently recognized. Based on a morphological approach, we describe a new species of Myotis from the Uruguayan Pampas grasslands, an ecoregion under high anthropogenic pressure with a largely unknown bat fauna. Qualitative and quantitative morphological analyses support the recognition of the new species and we present a set of external and cranial diagnostic characters by comparing them with other neotropical Myotis species. The new species reassembles Myotis riparius, but can be distinguished by a set of qualitative and quantitative morphological traits, including its clearly bicolored dorsal fur, tricolored ventral fur, a pelage on the dorsal surface of uropatagium, sagittal crest lower, braincase lower in lateral view and overall smaller size.

Myotis nesopolus currently comprises two subspecies. The nominate subspecies (M. n. nesopolus) occurs on the Caribbean islands of Curaçao and Bonaire, Netherlands Antilles, whereas M. n. larensis is known from mainland South America in northeastern Colombia and northwestern Venezuela. Our Maximum Likelihood phylogenetic analyses of cytochrome-b gene sequences recovered M. nesopolus as a paraphyletic group, with M. n. nesopolus and M. n. larensis as non-sister lineages. The haplotype network indicates that these two subspecies do not share any haplotypes and are in different evolutionary trajectories. Additionally, these two subspecies can be distinguished on the basis of qualitative and quantitative morphological traits. This pattern supports the recognition of M. nesopolus and M. larensis as full species. Our results also reveal that the assemblage of Caribbean Myotis do not form a monophyletic group. Caribbean species are phylogenetically close to mainland species from northern South America and Central America, suggesting that colonization of Caribbean islands happened multiple times.

Abstract Background Tree squirrels (Sciuridae, Sciurini), in particular the highly diverse Neotropical lineages, are amongst the most rapidly diversifying branches of the mammal tree of life but also some of the least known. Negligence of this group by systematists is likely a product of the difficulties in assessing morphological informative traits and of the scarcity or unavailability of fresh tissue samples for DNA sequencing. The highly discrepant taxonomic arrangements are a consequence of the lack of phylogenies and the exclusive phenotypic-based classifications, which can be misleading in a group with conservative morphology. Here we used high-throughput sequencing and an unprecedented sampling of museum specimens to provide the first comprehensive phylogeny of tree squirrels, with a special emphasis on Neotropical taxa. Results We obtained complete or partial mitochondrial genomes from 232 historical and modern samples, representing 40 of the 43 currently recognized species of Sciurini. Our phylogenetic analyses—performed with datasets differing on levels of missing data and taxa under distinct analytical methods—strongly support the monophyly of Sciurini and consistently recovered 12 major clades within the tribe. We found evidence that the diversity of Neotropical tree squirrels is underestimated, with at least six lineages that represent taxa to be named or revalidated. Ancestral state reconstructions of number of upper premolars and number of mammae indicated that alternative conditions of both characters must have evolved multiple times throughout the evolutionary history of tree squirrels. Conclusions Complete mitogenomes were obtained from museum specimens as old as 120 years, reinforcing the potential of historical samples for phylogenetic inferences of elusive lineages of the tree of life. None of the taxonomic arrangements ever proposed for tree squirrels fully corresponded to our phylogenetic reconstruction, with only a few of the currently recognized genera recovered as monophyletic. By investigating the evolution of two morphological traits widely employed in the taxonomy of the group, we revealed that their homoplastic nature can help explain the incongruence between phylogenetic results and the classification schemes presented so far. Based on our phylogenetic results we suggest a tentative supraspecific taxonomic arrangement for Sciurini, employing 13 generic names used in previous taxonomic classifications.

Tree squirrels (Sciurinae, Sciurini) represent a diverse radiation that successfully colonized Europe, Asia and the Americas during the Miocene-Pliocene, but information on their evolutionary history remains unclear. In the Neotropics, they have been shown to exhibit the highest rate of diversification amongst all arboreal squirrels, with strikingly high species accumulation rates in the past 3 Mya. In this study, we investigated the tempo and mode of diversification of tree squirrels using a mitogenome dataset that includes 43 Sciurini species. Our results corroborate the date of origin of the tribe Sciurini around 14 Mya (13.4–15.5) but suggest that their ancestral area was most likely in North America. This is in contrast to previous findings that suggested that the ancestors of this tribe occupied Eurasia. We estimated that cladogenetic events leading to the Eurasian lineages occurred twice at 10.5 and 9.7 Mya. Current North American genera originated in a temporal window from 6.2–2.3 Mya, and the origin of the Neotropical radiation was estimated to have occurred around 6 Mya in northwestern South America, in the Pacific dominion. Remarkably, our results indicate that tree squirrels entered South America at an earlier date than previously estimated. This could have happened either through a land corridor connecting the Caribbean islands or through the Panamanian land bridge. Most cladogenetic events in Eurasia and North America appear to have occurred either late in the Miocene or in the Pleistocene, while the majority of Neotropical cladogenetic events occurred along the Pliocene—right after the South American invasion. We found a fairly constant speciation rate for tree squirrels (averaging 0.29), which contrasts with the peak of lineage accumulation observed in the Pliocene. The absence of fluctuations in the diversification rate may be the result of several extinction events that were responsible for equalizing the number of lineages maintained over time. Finally, we conclude that the South American invasion was not as recent as previously inferred, but the diversification there was indeed very fast.