Weber JN, Hoekstra HE.
The evolution of burrowing behavior in deer mice. Animal Behavior 2009;77:603-09.
AbstractThe evolutionary history of most behaviours remains unknown. Here, we assay burrowing behaviour of seven species of deer mice in standardized environments to determine how burrowing evolved in this genus (Peromyscus). We found that several, but not all, species burrow even after many generations of captive breeding. Specifically, there were significant and repeatable differences in both the frequency of burrowing and burrow shape between species. Moreover, these observed species-specific behaviours resemble those reported in wild mice. These results suggest that there is probably a strong genetic component to burrowing in deer mice. We also generated a phylogeny for these seven species using characters from four mtDNA and two autosomal loci. Mapping burrowing behaviour onto this phylogeny suggests a sequence for how complex burrowing evolves: from small, simple burrows to long, multitunnel burrows with defined entrance and escape tunnels. In particular, the most ‘complex’ burrows of P. polionotus appear to be derived. These behavioural data, when examined in a phylogenetic context, show that even closely related species differ in their burrowing behaviours and that the most complex burrows probably evolved by the gradual accumulation of genetic change over time. 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
PDF Berry AJ, Hoekstra HE.
(Re)Reading The Origin. Current Biology 2009;19(3):R9.
PDF Mullen LM, Vignieri SN, Gore JA, Hoekstra HE.
Adaptive basis of geographic variation: Genetic, phenotypic and environmental differences among beach mouse populations. Proceedings of the Royal Society B: Biological Sciences 2009;276:3809-18.
AbstractA major goal in evolutionary biology is to understand how and why populations differentiate, both genetically and phenotypically, as they invade a novel habitat. A classical example of adaptation is the pale colour of beach mice, relative to their dark mainland ancestors, which colonized the isolated sandy dunes and barrier islands on Florida's Gulf Coast. However, much less is known about differentiation among the Gulf Coast beach mice, which comprise five subspecies linearly arrayed on Florida's shoreline. Here, we test the role of selection in maintaining variation among these beach mouse subspecies at multiple levels-phenotype, genotype and the environments they inhabit. While all beach subspecies have light pelage, they differ significantly in colour pattern. These subspecies are also genetically distinct: pair-wise F(st)-values range from 0.23 to 0.63 and levels of gene flow are low. However, we did not find a correlation between phenotypic and genetic distance. Instead, we find a significant association between the average 'lightness' of each subspecies and the brightness of the substrate it inhabits: the two most genetically divergent subspecies occupy the most similar habitats and have converged on phenotype, whereas the most genetically similar subspecies occupy the most different environments and have divergent phenotypes. Moreover, allelic variation at the pigmentation gene, Mc1r, is statistically correlated with these colour differences but not with variation at other genetic loci. Together, these results suggest that natural selection for camouflage-via changes in Mc1r allele frequency-contributes to pigment differentiation among beach mouse subspecies.
PDF Aminetzach YT, Srouji JR, Kong CY, Hoekstra HE.
Convergent evolution of novel protein function in shrew and lizard venom. Current Biology 2009;19:1925-31.
AbstractHow do proteins evolve novel functions? To address this question, we are studying the evolution of a mammalian toxin, the serine protease BLTX [1], from the salivary glands of the North American shrew Blarina brevicauda. Here, we examine the molecular changes responsible for promoting BLTX toxicity. First, we show that regulatory loops surrounding the BLTX active site have evolved adaptively via acquisition of small insertions and subsequent accelerated sequence evolution. Second, these mutations introduce a novel chemical environment into the catalytic cleft of BLTX. Third, molecular-dynamic simulations show that the observed changes create a novel chemical and physical topology consistent with increased enzyme catalysis. Finally, we show that a toxic serine protease from the Mexican beaded lizard (GTX) [2] has evolved convergently through almost identical functional changes. Together, these results suggest that the evolution of toxicity might be predictable-arising via adaptive structural modification of analogous labile regulatory loops of an ancestral serine protease-and thus might aid in the identification of other toxic proteins.
PDF Steiner CC, Rompler H, Boettger LM, Schoneberg T, Hoekstra HE.
The genetic basis of phenotypic convergence in beach mice: Similar pigment patterns but different genes. Molecular Biology and Evolution 2009;26:35-45.
AbstractConvergent evolution is a widespread phenomenon seen in diverse organisms inhabiting similar selective environments. However, it is unclear if similar phenotypes are produced by the same or different genes and mutations. Here we analyze the molecular mechanisms underlying convergent pigment pattern among subspecies of the beach mouse (Peromyscus polionotus) inhabiting the Gulf and Atlantic coasts of Florida. In these two geographic regions, separated by more than 300 km, "beach mice" have lighter colored coats than do their mainland counterparts, produced by natural selection for camouflage against the pale coastal sand dunes. We measured color pattern in eight beach mouse subspecies and showed that three of the Gulf Coast subspecies are more phenotypically similar to an Atlantic coast subspecies than to their Gulf Coast neighbors. However, light-colored beach mice do not form a monophyletic group. Previous results implicated a single derived amino acid change in the melanocortin-1 receptor (Mc1r) as a major contributor to pigment pattern in the Gulf Coast beach mice; despite phenotypic similarities, the derived Mc1r allele was not found in the Atlantic coast beach mouse populations. Here we show that Atlantic coast beach mice have high levels of Mc1r polymorphism but they lack unique alleles. Functional assays revealed that single amino acid mutations segregating in Atlantic coast beach mice do not cause any change in Mc1r activity compared with the activity of Mc1r from dark-colored mice. These joint results show that convergent pigment patterns in recently diverged beach mouse subspecies--whose developmental constraints are presumably similar--have evolved through a diversity of genetic mechanisms.
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