Recent molecular studies in gerbils found multiple instances of discordance between molecular and morphological phylogenies. In this study, we analyse the largest molecular data set to date of gerbils and their sister group the deomyines to estimate their phylogenetic relationships. Maximum-likelihood and Bayesian analyses were largely concordant, and both generally had high levels of node support. For gerbils, the results were generally concordant with previous molecular phylogenies based on allozymes, chromosomes, DNA/DNA hybridization and DNA sequences, and discordant with morphological phylogenies. None of the traditional gerbil tribes and subtribes were monophyletic. In addition, paraphyly was found in the genera Gerbillus, Gerbilliscus and Meriones as well as in five subgenera within Dipodillus, Gerbillurus and Meriones. Short branches separating taxa in small clusters within Dipodillus and Meriones suggest synonymy. Within deomyines, all genera and subgenera were monophyletic; however, two species groups within Acomys appear to contain synonymous taxa. We also find support for the discordance between molecular and morphological phylogenies in gerbils being partly due to convergent adaptations to arid environments, primarily in the suite of traits associated with inflation of the tympanic bullae. Relative bullar size does appear to be a desert adaptation and is correlated with aridity independent of phylogeny. Further, it varies more strongly along bioclimatic clines than between binary habitat classifications (desert versus mesic).

openAccessArticle: Falsecover date: 2015-12-15pii: S1616-5047(15)00125-1Harvest Date: 2016-01-06 13:08:15issueName:Page Range: -href scidir: http://www.sciencedirect.com/science/article/pii/S1616504715001251pubType

The emergence of exceptionally diverse clades is often attributed to ecological opportunity. For example, the exceptional diversity in the most diverse superfamily of mammals, muroid rodents, has been explained in terms of multiple independent adaptive radiations. If multiple ecological opportunity events are responsible for generating muroid diversity, we expect to find evidence of these lineages ecologically diversifying following dispersal into new biogeographical areas. In the present study, we tested the trait-based predictions of ecological opportunity using data on body size, appendages, and elevation in combination with previously published data on biogeographical transitions and a time-calibrated molecular phylogeny. We identified weak to no support of early ecological diversification following the initial colonizations of all continental regions, based on multiple tests, including node height tests, disparity through time plots, evolutionary model comparison, and Bayesian analysis of macroevolutionary mixtures. Clades identified with increased diversification rates, not associated with geographical transitions, also did not show patterns of phenotypic divergence predicted by ecological opportunity, which suggests that phylogenetic diversity and phenotypic disparity may be decoupled in muroids. These results indicate that shifts in diversification rates and biogeographically-mediated ecological opportunity are poor predictors of phenotypic diversity patterns in muroids.

Aim: We test whether geographical variation in the length of appendages in rodent species follows predictions of Allen's rule (a positive relationship between appendage length and temperature) at a broad taxonomic scale (order Rodentia). We also test whether the applicability of this rule varies based on the unit of analysis (species or assemblage), the appendage examined (tail, hind foot, ear), body size, occupied habitat, geographical range size, life mode and saltatorial ability. Location: Worldwide. Time period: Current. Major taxa studied: Rodents (order Rodentia). Methods: We assembled data on the morphology, ecology and phylogeny for ≤ 2,212 rodent species, representing c. 86% of all the described rodent species and c. 95% of the described genera. We tested the predicted Allen's rule associations among sizecorrected appendage lengths and both latitudinal and climatic variables (temperature and precipitation). We applied a cross-species approach based on phylogenetic regressions and a cross-assemblage approach based on spatial regressions in equalarea 1.5° grid cells. Results: Support for Allen's rule was greatest for the tail and was stronger across assemblages than across species. We detected a negative relationship between tail length and (absolute) latitude, which was accounted for by a positive association between tail length and temperature of the coldest month. This association was greatest in desert species. In addition, we observed a negative relationship between ear length and precipitation. Main conclusions: In rodents, Allen's rule is confirmed only for tails, and this association seems to be driven by adaptation to the cold, rather than warm temperatures. Habitat type seems to influence conformity to this rule. Conformity to Allen's rule is likely to be the result of complex evolutionary trade-offs between temperature regulation and other essential species traits.

Aim The International Union for Conservation of Nature (IUCN) expert range maps and the Global Biodiversity Information Facility (GBIF) species occurrence data are commonly used to estimate species’ geographic range. Macroecological studies often cross‐reference geographic range data with a climate dataset, to extract the mean environmental conditions encountered by a species within its geographic range. We aimed to assess the consistency of the environmental data estimates derived from IUCN versus GBIF geographic range data, and to test whether such differences may affect estimates of ecogeographical relationships, such as Bergmann's rule. Location Worldwide. Time period Around 2000. Taxa Rodents (Rodentia). Methods We first assessed the correlation between environmental data estimates (19 bioclimatic variables and elevation) derived from IUCN versus GBIF geographic range data of 1,315 rodent species, comparing how range size, conservation status, habitat, zoogeographic realm or elevation changed these correlations. Then, we compared the association between body mass and climate (mean temperature and precipitation) when the latter are derived from IUCN or GBIF data. Results There was high correlation between environmental data estimates derived from IUCN versus GBIF data, especially when excluding GBIF occurrences outside of IUCN polygons. Species’ characteristics, or using the mean or median, did not change the consistency between estimates. Overall, GBIF occurrence data and IUCN range maps produced similar patterns of body mass—climate correlations. Main conclusions At the large spatial and taxonomic scale employed in this study, there does not seem to be any considerable differences in the average environmental data estimates derived from IUCN versus GBIF geographic range data. This result indicates that both sources of geographic range data could be used independently or in concert for macroecological inferences that involve summarizing species’ niches by a single estimate of the average of their used environments.

The “resource availability hypothesis” predicts occurrence of larger rodents in more productive habitats. This prediction was tested in a dataset of 1,301 rodent species. We used adult body mass as a measure of body size and normalized difference vegetation index (NDVI) as a measure of habitat productivity. We utilized a cross-species approach to investigate the association between these variables. This was done at both the order level (Rodentia) and at narrower taxonomic scales. We applied phylogenetic generalized least squares (PGLS) to correct for phylogenetic relationships. The relationship between body mas and NDVI was also investigated across rodent assemblages. We controlled for spatial autocorrelation using generalized least squares (GLS) analysis. The cross-species approach found extremely low support for the resource availability hypothesis. This was reflected by a weak positive association between body mass and NDVI at the order level. We find a positive association in only a minority of rodent subtaxa. The best fit GLS model detected no significant association between body mass and NDVI across assemblages. Thus, our results do not support the view that resource availability plays a major role in explaining geographic variation in rodent body size.

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