Sciurini

Abstract: 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 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 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

Abstract: A new genus, Douglassia, is erected for the problematic Chadronian sciurid Sciurus jeffersoni Douglass, 1901. Previously undescribed material adds new morphologic information for the taxon. Douglassia differs from other sciurids in the retention of primitive dental and masseteric morphology. Based on postcranial anatomy, the genus is referred to the Tribe Sciurini (tree squirrels), which is regarded as the sister taxon to all other Sciurinae. The known fossil material of Tertiary flying squirrels is inadequate to determine whether they constitute a distinct family.

Abstract: Pecnerova, P. & Martinkova, N. (2012). Evolutionary history of tree squirrels (Rodentia, Sciurini) based on multilocus phylogeny reconstruction. —Zoologica Scripta, 41, 211–219. Tree squirrels of the tribe Sciurini represent a group with unresolved phylogenetic relationships in gene trees. We used partial sequences of mitochondrial genes for 12S rRNA, 16S rRNA, cytochrome b and d-loop, and nuclear irbp, c-myc exon 2 and 3 and rag1 genes to reconstruct phylogenetic relationships within the tribe, maximizing the number of analysed species. Bayesian inference analysis of the concatenated sequences revealed common trends that were similar to those retrieved with supertree reconstruction. We confirmed congruence between phylogeny and zoogeography. The first group that diverged from a common ancestor was genus Tamiasciurus, followed by Palaearctic Sciurus and Indomalayan Rheithrosciurus macrotis. Nearctic and Neotropical Sciurus species formed a monophyletic group that included Microsciurus and Syntheosciurus. Neotropical Sciurini were monophyletic with a putative exception of Syntheosciurus brochus that was included in a polychotomy with Nearctic Sciurus in supertree analyses. Our data indicate that Sciurini tree squirrels originated in the northern hemisphere and ancestors of contemporary taxa attained their current distribution through overland colonization from the nearest continent rather than through trans-Pacific dispersal.