Understanding both the role of selection in driving phenotypic change and its underlying genetic basis remain major challenges in evolutionary biology. Here, we use modern tools to revisit a classic ...system of local adaptation in the North American deer mouse, Peromyscus maniculatus, which occupies two main habitat types: prairie and forest. Using historical collections, we find that forest-dwelling mice have longer tails than those from nonforested habitat, even when we account for individual and population relatedness. Using genome-wide SNP data, we show that mice from forested habitats in the eastern and western parts of their range form separate clades, suggesting that increased tail length evolved independently. We find that forest mice in the east and west have both more and longer caudal vertebrae, but not trunk vertebrae, than nearby prairie forms. By intercrossing prairie and forest mice, we show that the number and length of caudal vertebrae are not correlated in this recombinant population, indicating that variation in these traits is controlled by separate genetic loci. Together, these results demonstrate convergent evolution of the long-tailed forest phenotype through two distinct genetic mechanisms, affecting number and length of vertebrae, and suggest that these morphological changes—either independently or together—are adaptive.
Although climate change models predict relatively modest increases in temperature in the tropics by the end of the century, recent analyses identify tropical ectotherms as the organisms most at risk ...from climate warming. Because metabolic rate in ectotherms increases exponentially with temperature, even a small rise in temperature poses a physiological threat to tropical ectotherms inhabiting an already hot environment. If correct, the metabolic theory of climate warming has profound implications for global biodiversity, since tropical insects and arachnids constitute the vast majority of animal species. Predicting how climate change will translate into fitness consequences for tropical arthropods requires an understanding of the effects of temperature increase on the entire life history of the species. Here, in a comprehensive case study of the fitness consequences of the projected temperature increase for the tropics, we conducted a split‐brood experiment on the neotropical pseudoscorpion, Cordylochernes scorpioides, in which 792 offspring from 33 females were randomly assigned at birth to control‐ and high‐temperature treatments for rearing through the adult stage. The diurnally varying, control treatment temperature was determined from long‐term, average daily temperature minima and maxima in the pseudoscorpion's native habitat. In the high temperature treatment, increasing temperature by the 3.5 °C predicted for the tropics significantly reduced survival and accelerated development at the cost of reduced adult size and a dramatic decrease in level of sexual dimorphism. The most striking effects, however, involved reproductive traits. Reared at high temperature, males produced 45% as many sperm as control males, and females failed to reproduce. Sequencing of the mitochondrial ND2 gene revealed two highly divergent haplogroups that differed substantially in developmental rate and survivorship but not in reproductive response to high temperature. Our findings suggest that reproduction may be the Achilles’ heel of tropical ectotherms, as climate warming subjects them to an increasingly adverse thermal environment.
We investigated a major geographic break in mitochondrial DNA (mtDNA) haplotypes in deer mice, Peromyscus maniculatus, by analysing spatial variation in a 491-bp fragment of the mtDNA control region ...from 455 samples distributed across a north-south transect of 2000 km in Western North America. To determine whether the mtDNA break was reflected in the nuclear genome, we then compared spatial variation in 13 nuclear microsatellites of 95 individuals surrounding the mtDNA break. Using a canonical correlation analysis we found that nuclear genomic variation was not correlated with mtDNA differentiation. The contrasting patterns of variation in mtDNA and nuclear DNA are consistent with a hypothesis of historic genetic drift that occurred in isolated refugia combined with recent gene flow between the formerly isolated refugial populations. A Mantel test of genetic vs. geographic distance revealed that recent gene flow between deer mouse populations has been high. We conclude that past vicariant events associated with Pleistocene climate changes together with recent gene flow have created the observed intra-specific cytonuclear discordance in Western North America.
Accurately predicting the response of species to climate change is crucial for the preservation of contemporary species diversity. In the current study, we analyze the response of two congeneric ...small mammal species (Peromyscus maniculatus and Peromyscus truei) to recent climate change in the region of Yosemite National Park (California, USA). The generalist P. maniculatus did not change its distribution in response to climate change while the specialist P. truei substantially changed its geographic and elevational distribution in the region, expanding into Yosemite. Using molecular genetic techniques we found that a cryptic geographic shift in genetic variation may have occurred within the geographically stable P. maniculatus distribution. Using a combination of morphometric and molecular genetic techniques we confirmed that a P. truei subspecies previously identified as a habitat specialist expanded into new habitat types, suggesting that this subspecies is not in fact a habitat specialist. Instead, we propose that the range of this subspecies is instead limited by climatic variables currently varying in response to contemporary climate change. These results underscore the importance of verifying the natural-history-based assumptions used to develop predictive models of species' response to climate change.
Parents may feed nestlings based on positional cues resulting from sibling competition for favored positions at the front of a nest cavity, or they may assess begging intensity regardless of location ...within the nest. We independently manipulated proximity to the nest entrance and hunger level to determine whether western bluebird (Sialia mexicana) parents favor hungrier nestlings or instead feed nestlings closest to the nest entrance. We used a balanced design to vary hungry and fed nestlings between the back and front of the nest box. We deprived half of the nestlings in each brood of food for an hour, and then, each nestling was constrained using Plexiglas dividers to a quadrant in the nest box. We videotaped inside the box to assess begging intensity and food delivery to individual nestlings. Hungry nestlings begged more intensely and received more food than fed nestlings, regardless of their proximity to the nest entrance. However, when delivering the first feed to nestlings, parents favored front nestlings over hungry nestlings, possibly due to a bias resulting from the manipulation, which involved replacing and rearranging nestlings after a 1-h period. Overall, parents did not favor nestlings in the front of the nest over those in the back. Parents therefore are able to distinguish hungrier nestlings and preferentially feed them under favorable environmental conditions, when brood reduction is uncommon.
Objective:To investigate the protective effect of glucagon-like peptid-1(GLP-l) against cardiac microvascular endothelial cell(GTFCs) injured by high glucose.Methods:CMECs were isolated and ...cultured.Superoxide assay kit and dihydroethidine(DHE) staining were used to assess oxidative stress.TENEL staining and caspase 3 expression were used to assess the apoptosis of CMECs.H89 was used to inhibit eAMP/PKA pathway:fasudil was used to inhibit Rho/ROCK pathway.The protein expressions of Rho.ROCK uere examined by Western blol analysis.lesults:High glucose increased the production of ROS.the activity of NADPH.the apoptosis rate and the expression level of Rho/ROCK in CMECs.while GLP- 1 decreased high glucose-induced ROS production.the NADPH activity and the apoptosis rate and the expression level of Rho/ROCK in CMECs,the difference were statistically significant(P<0.05).Conclusions:GLP-1 could protect the cardiac microvessels against oxidative stress and apoptosis.The protective effects of GLP-1 are dependent on downstream inhibition of Rho through a cAMP/PKA-dependent manner,resulting in a subsequent decrease in the expression of NADPH oxidase.
My dissertation research studied the evolutionary processes that created contemporary genetic and population diversity in Peromyscus mice from the Pacific Northwest. I used a variety of genetic, ...morphometric, and statistical tools to delimit species and populations of these mice. I applied evolutionary theory and biogeographic history to each study system to create hypotheses about how these populations and species have evolved. The first chapter studies a pattern of genealogical discordance between mitochondrial and nuclear DNA in Western North American Peromyscus maniculatus. I concluded that this pattern resulted from Pleistocene climate shifts resulting in genetic drift of populations. The second chapter studies morphological and genetic diversity in Oregon Peromyscus maniculatus. I found that this morphological and genetic diversity exists in spite of high rates of homogenizing gene flow, suggesting that natural selection is maintaining this diversity in the case of morphology. The final chapter studies the species relationship of Peromyscus maniculatus and Peromyscus keeni. I found that Peromyscus maniculatus and Peromyscus keeni are divergent at mitochondrial genes but highly similar at nuclear genes. Previous research on these species reveals chromosomal differences associated with mitochondrial differences between these species, and from this I hypothesize that these species are in fact recent reproductively isolated, and that nuclear diversity has not yet coalesced due to this recent time frame. This body of work revealed to me the role of microevolutionary forces and biogeography in shaping modern day diversity in wild species.
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