Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
1,405
result(s) for
"Sciuridae"
Sort by:
Squirrels of the world / Richard W. Thorington, Jr. and others
The authors reveal every detail of the family Sciuridae, which includes ground squirrels, tree squirrels, flying squirrels, prairie dogs, and chipmunks. Each species - from the familiar gray squirrel of American backyards to the exotic and endangered woolly flying squirrel of Pakistan - is described in a detailed account that includes distinguishing characteristics, ecology, natural history, conservation status, and current threats to its existence.
eBook
Rare ecomorphological convergence on a complex adaptive landscape
Convergence is widely regarded as compelling evidence for adaptation, often being portrayed as evidence that phenotypic outcomes are predictable from ecology, overriding contingencies of history. However, repeated outcomes may be very rare unless adaptive landscapes are simple, structured by strong ecological and functional constraints. One such constraint may be a limitation on body size because performance often scales with size, allowing species to adapt to challenging functions by modifying only size. When size is constrained, species might adapt by changing shape; convergent shapes may therefore be common when size is limiting and functions are challenging. We examine the roles of size and diet as determinants of jaw shape in Sciuridae. As expected, size and diet have significant interdependent effects on jaw shape and ecomorphological convergence is rare, typically involving demanding diets and limiting sizes. More surprising is morphological without ecological convergence, which is equally common between and within dietary classes. Those cases, like rare ecomorphological convergence, may be consequences of evolving on an adaptive landscape shaped by many-to-many relationships between ecology and function, many-to-one relationships between form and performance, and one-to-many relationships between functionally versatile morphologies and ecology. On complex adaptive landscapes, ecological selection can yield different outcomes.
Journal Article
Glucocorticoids coordinate changes in gut microbiome composition in wild North American red squirrels
The gut microbiome impacts host health and fitness, in part through the diversification of gut metabolic function and pathogen protection. Elevations in glucocorticoids (GCs) appear to reduce gut microbiome diversity in experimental studies, suggesting that a loss of microbial diversity may be a negative consequence of increased GCs. However, given that ecological factors like food availability and population density may independently influence both GCs and microbial diversity, understanding how these factors structure the GC-microbiome relationship is crucial to interpreting its significance in wild populations. Here, we used an ecological framework to investigate the relationship between GCs and gut microbiome diversity in wild North American red squirrels (
Tamiasciurus hudsonicus
). As expected, higher GCs predicted lower gut microbiome diversity and an increase in metabolic taxa. Surprisingly, but in line with prior empirical studies on wild animals, gastrointestinal pathogens decreased as GCs increased. Both dietary heterogeneity and an upcoming food pulse exhibited direct effects on gut microbiome diversity, whereas conspecific density and reproductive activity impacted diversity indirectly via changes in host GCs. Our results provide evidence of a gut–brain axis in wild red squirrels and highlight the importance of situating the GC-gut microbiome relationship within an ecological framework.
Journal Article
Body-size Scaling is Related to Gut Microbial Diversity, Metabolism and Dietary Niche of Arboreal Folivorous Flying Squirrels
Thermal homeostasis of mammals is constrained by body-size scaling. Consequently, small mammals require considerable energy to maintain a high mass-specific metabolic rate (MSMR) and sustain target body temperature. In association with gut microbiota, mammalian hosts acquire absorbable molecules and fulfill their metabolic requirements. Our objective was to characterize gut microbes in wild mammals and relate those findings to host body-size scaling. Two large (
Petaurista philippensis grandis
and
P. alborufus lena
), one medium (
Trogopterus xanthipes
) and one small (
Pteromys volans orii
) species of flying squirrels (FS) were studied. Using 16S rRNA genes, 1,104 OTUs were detected from four FS, with 1.99% of OTUs shared among all FS. Although all FS gut microbiota were dominated by
Firmicutes
, they were constituted by different bacterial families. Moreover,
Bacteroidetes
accounted for up to 19% of gut microbiota in small FS, but was absent in large FS. Finally, based on metagenome predictions, carbohydrate and amino acid metabolism genes were enriched in small body-size FS. In conclusion, gut microbiota compositions and predictive metabolic functions were characteristic of body-size in FS, consistent with their adaptations to folivorous dietary niches.
Journal Article
Impacts of Inference Method and Data set Filtering on Phylogenomic Resolution in a Rapid Radiation of Ground Squirrels (Xerinae: Marmotini)
Phylogenomic data sets are illuminating many areas of the Tree of Life. However, the large size of these data sets alone may be insufficient to resolve problematic nodes in the most rapid evolutionary radiations, because inferences in zones of extraordinarily low phylogenetic signal can be sensitive to the model and method of inference, as well as the information content of loci employed. We used a data set of >3950 ultraconserved element (UCE) loci from a classic mammalian radiation, ground-dwelling squirrels of the tribe Marmotini (Sciuridae: Xerinae), to assess sensitivity of phylogenetic estimates to varying per-locus information content across four different inference methods (RAxML, ASTRAL, NJst, and SVDquartets). Persistent discordance was found in topology and bootstrap support between concatenation- and coalescent-based inferences; among methods within the coalescent framework; and within all methods in response to different filtering scenarios. Contrary to some recent empirical UCE-based studies, filtering by information content did not promote complete among-method concordance. Nevertheless, filtering did improve concordance relative to randomly selected locus sets, largely via improved consistency of two-step summary methods (particularly NJst) under conditions of higher average per-locus variation (and thus increasing gene tree precision). The benefits of phylogenomic data set filtering are variable among classes of inference methods and across different evolutionary scenarios, reiterating the complexities of resolving rapid radiations, even with robust taxon and character sampling.
Journal Article
Inhibition of Borna disease virus replication by an endogenous bornavirus-like element in the ground squirrel genome
Significance Sequences derived from ancient viruses have been shown to make up a substantial part of animal genomes. Bornaviruses, a genus of nonsegmented, negative-sense RNA virus, also have left their DNA copies in the genomes of a number of vertebrate lineages. Recent studies have demonstrated that some endogenous bornavirus-like elements (EBLs) may have acquired functions in their hosts as a result of exaptation. In this study, we show that protein encoded by an EBL in the genome of the thirteen-lined ground squirrel efficiently blocks infection and replication of extant bornavirus. To our knowledge, this is the first report showing that endogenous nonretroviral RNA virus elements may function in antiviral defense, providing a potential role for RNA virus endogenization in host evolution.
Journal Article
Oldest skeleton of a fossil flying squirrel casts new light on the phylogeny of the group
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.
Journal Article
Stasis of functionally versatile specialists
A classic hypothesis posits that lineages exhibiting long-term stasis are broadly adapted generalists that remain well-adapted despite environmental change. However, lacking constraints that steepen adaptive peaks and stabilize the optimum, generalists’ phenotypes might drift around a broad adaptive plateau. We propose that stasis would be likely for morphological specialists that behave as ecological generalists much of the time because specialists’functional constraints stabilize the optimum, but those with a broad niche, such as generalists, can persist despite environmental change. Tree squirrels (Callosciurinae and Sciurini) exemplify ecologically versatile specialists, being extreme in adaptations for forceful biting that expand rather than limit niche breadth. Here, we examine the structure of disparity and the evolutionary dynamics of their trophic morphology (mandible size and shape) to determine if they exhibit stasis. In both lineages, a few dietary specialists disproportionately account for disparity; excluding them, we find compelling evidence for stasis of jaw shape but not size. The primary optima of these lineages diverge little, if at all over approximately 30 million years. Once their trophic apparatus was assembled, their morphological specialization steepened the slopes of their adaptive peak and constrained the position of the optima without limiting niche breadth.
Journal Article
OXIDATIVE DAMAGE INCREASES WITH REPRODUCTIVE ENERGY EXPENDITURE AND IS REDUCED BY FOOD-SUPPLEMENTATION
A central principle in life-history theory is that reproductive effort negatively affects survival. Costs of reproduction are thought to be physiologically based, but the underlying mechanisms remain poorly understood. Using female North American red squirrels (Tamiasciurus hudsonicus), we test the hypothesis that energetic investment in reproduction overwhelms investment in antioxidant protection, leading to oxidative damage. In support of this hypothesis we found that the highest levels of plasma protein oxidative damage in squirrels occurred during the energetically demanding period of lactation. Moreover, plasma protein oxidative damage was also elevated in squirrels that expended the most energy and had the lowest antioxidant protection. Finally, we found that squirrels that were food-supplemented during lactation and winter had increased antioxidant protection and reduced plasma protein oxidative damage providing the first experimental evidence in the wild that access to abundant resources can reduce this physiological cost.
Journal Article