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Flying squirrels are the only group of gliding mammals with a remarkable diversity and wide geographical range. However, their evolutionary story is not well known. Thus far, identification of extinct flying squirrels has been exclusively based on dental features, which, contrary to certain postcranial characters, are not unique to them. Therefore, fossils attributed to this clade may indeed belong to other squirrel groups. Here we report the oldest fossil skeleton of a flying squirrel (11.6 Ma) that displays the gliding-related diagnostic features shared by extant forms and allows for a recalibration of the divergence time between tree and flying squirrels. Our phylogenetic analyses combining morphological and molecular data generally support older dates than previous molecular estimates (~23 Ma), being congruent with the inclusion of some of the earliest fossils (~36 Ma) into this clade. They also show that flying squirrels experienced little morphological change for almost 12 million years.

The genetic structure of small semiaquatic animals may be influenced by dispersal across both rivers and land. The relative importance of these two modes of dispersal may vary across different species and with ecological conditions and evolutionary periods. The Pyrenean desman (Galemys pyrenaicus) is an endemic mammal of the Iberian Peninsula with a strong phylogeographic structure and semiaquatic habits, thus making it an ideal model to study the effects of river and overland dispersal on its genetic structure. Thanks to different types of noninvasive samples, we obtained an extensive sampling of the Pyrenean desman from the northwestern region of the Iberian Peninsula and sequenced two mitochondrial DNA fragments. We then analyzed, using an isolation-by-distance approach, the correlation between phylogenetic distances and geographical distances measured along both river networks and land to infer the relative importance of river and overland dispersal. We found that the correlations in the whole area and in a large basin were consistent with an effect of overland dispersal, which may be due to the postglacial colonization of new territories using terrestrial corridors and, possibly, a more extensive fluvial network that may have been present during the Holocene. However, in a small basin, likely to be less influenced by the impact of ancient postglacial dispersal, the correlations suggested significant overall effects of both overland and river dispersal, as expected for a semiaquatic mammal.Therefore, different scales and geographical regions reflect different aspects of the evolutionary history and ecology of this semiaquatic species using this isolation-bydistance method. The results we obtained may have crucial implications for the conservation of the Pyrenean desman because they reinforce the importance of interbasin dispersal for this species in the studied area and the need to protect the whole riverine ecosystem, including rivers, upland streams and terrestrial corridors between basins. K E Y W O R D Sdispersal, Galemys pyrenaicus, genetic diversity, Iberian Peninsula, isolation-by-distance, mitochondrial DNA

The Cabrera's water shrew (Neomys anomalus) is a small semi‐aquatic mammal whose taxonomic status was recently elevated from subspecies to species; as a consequence of this change, this species is now endemic to the Iberian Peninsula. In this study, we looked at its evolutionary history by combining phylogeography, the spatial distribution of genetic diversity, and species distribution modeling. To perform these analyses, we used noninvasive samples collected across the species distribution range and sequenced partial mitochondrial cytochrome b and D‐loop genes. Maximum‐likelihood and Bayesian phylogenetic trees derived from these sequences indicated that N. anomalus is divided into two main phylogroups that correlate strongly with geography, with two contact zones between the groups that showed limited spatial mixing between them. River basins were responsible for only a small percentage of the structure of the genetic diversity of this species despite its riparian habitat. The nucleotide diversity variation map showed the highest genetic diversity to be in the north of the Iberian Peninsula. Finally, species distribution modeling allowed the inference of an optimal area during the Last Interglacial in the north of the Iberian Peninsula, and multiple glacial refugia during the Last Glacial Maximum. The phylogeographic pattern of N. anomalus is strikingly similar to that of another semi‐aquatic Iberian mammal, the Pyrenean desman (Galemys pyrenaicus), revealing how Pleistocene glaciations could have had equivalent effects on species of similar ecology and distribution. This phylogeographic structure is consistent with N. anomalus having been isolated for long periods in multiple glacial refugia within the Iberian Peninsula, in agreement with the “refugia‐within‐refugia” hypothesis, and further supporting its status as a distinct species.

Evolutionary innovations and ecological competition are factors often cited as drivers of adaptive diversification. Yet many innovations result in stabilizing rather than diversifying selection on morphology, and morphological disparity among coexisting species can reflect competitive exclusion (species sorting) rather than sympatric adaptive divergence (character displacement). We studied the innovation of gliding in dragons (Agamidae) and squirrels (Sciuridae) and its effect on subsequent body size diversification. We found that gliding either had no impact (squirrels) or resulted in strong stabilizing selection on body size (dragons). Despite this constraining effect in dragons, sympatric gliders exhibit greater size disparity compared with allopatric gliders, a pattern consistent with, although not exclusively explained by, ecological competition changing the adaptive landscape of body size evolution to induce character displacement. These results show that innovations do not necessarily instigate further differentiation among species, as is so often assumed, and suggest that competition can be a powerful force generating morphological divergence among coexisting species, even in the face of strong stabilizing selection.

Introduced species alter established trophic interactions and molecular analysis can resolve changes in community structure and associated foraging links. Joro spiders (Trichonephila clavata) were recently introduced to the United States and their range is rapidly expanding across the east coast. Here, we used DNA metabarcoding of fecal samples, prey remains from webs, and dissected guts to compare diet composition of female Joro spiders in the southeastern United States. We amplified DNA from three material types using arthropod-targeted COI primers and sequenced with IIlumina MiSeq. Prey remains from webs had the highest diversity, richness, as well as the highest proportion of prey reads relative to Joro spider reads. Recovery of prey reads from fecal samples and dissected gut content was low and both were overwhelmed by Joro spider DNA. Although fecal samples and gut content had high proportions of Joro spider reads, fecal samples had higher prey diversity and richness. Moreover, we detected prey DNA from fecal samples several days after capture from the field, which reveals initial gut retention time estimates for fecal samples collected from web-building spiders. Combined, our results offer a first glimpse at the complexity of trophic associations for an introduced web-building spider and identify a viable material, prey remains from webs, as a source of prey DNA for estimates of biodiversity associated with web-building spiders.

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