Evolution
Environmental changes have caused episodes of habitat expansions in the evolutionary history of many species. These range changes affect the dynamics of biological evolution in multiple ways. Recent microbial experiments as well as simulations suggest that enhanced genetic drift at the frontier of a two‐dimensional range expansion can cause genetic sectoring patterns with fractal domain boundaries...
Prolonged periods of allopatry might result in loss of the ability to discriminate against other formerly sympatric species, and can lead to heterospecific matings and hybridization upon secondary contact. Loss of premating isolation during prolonged allopatry can operate in the opposite direction of reinforcement, but has until now been little explored. We investigated how premating isolation between...
The concept of Müllerian mimicry suggests convergent evolution to an intermediate pattern and does not predict polymorphism in mimicry rings. We examined the evolution of mimicry patterns and the order of divergence of various factors, including the role of aposematic patterns in speciation, in a clade of net‐winged beetles with a robust phylogeny that suggests that they dispersed from the Australian...
Pollination syndromes suggest that convergent evolution of floral traits and trait combinations reflects similar selection pressures. Accordingly, a pattern of selection on floral traits is expected to be consistent with increasing the attraction and pollen transfer of the important pollinator. We measured individual variation in six floral traits and yearly and lifetime total plant seed and fruit...
Latitudinal variation in patterns of evolution has fascinated biologists for over a century, but our understanding of latitudinal differences in evolutionary processes—such as selection and drift—remains limited. Here, we test for, and find, accelerated evolution of color patterns in bird taxa that breed at higher latitudes compared with those breeding in the tropics, analyzing data from seven diverse...
Several lines of evidence suggest that the X chromosome plays a large role in intrinsic postzygotic isolation. The role of the Z chromosome in speciation is much less understood. To explore the role of the Z chromosome in reproductive isolation, we studied nucleotide variation in two closely related bird species, the Thrush Nightingale (Luscinia luscinia) and the Common Nightingale (L. megarhynchos...
We study the evolution of higher levels of dominance as a response to negative frequency‐dependent selection. In contrast to previous studies, we focus on the effect of assortative mating on the evolution of dominance under frequency‐dependent intraspecific competition. We analyze a two‐locus two‐allele model, in which the primary locus has a major effect on a quantitative trait that is under a mixture...
The spatial genetic composition of hybrid zones exhibits a range of possible patterns, with many characterized by patchy distributions. While several hypothetical explanations exist for the maintenance of these “mosaic” hybrid zones, they remain virtually unexplored theoretically. Using computer simulations we investigate the roles of dispersal and assortative mating in the formation and persistence...
Speciation often has a strong geographical and environmental component, but the ecological factors that potentially underlie allopatric and parapatric speciation remain understudied. Two ecological mechanisms by which speciation may occur on geographic scales are allopatric speciation through niche conservatism and parapatric or allopatric speciation through niche divergence. A previous study on salamanders...
One of the classic examples of faunal turnover in the fossil record is the Miocene transition from faunas dominated by anchitheriine horses with low‐crowned molar teeth to faunas with hipparionine horses characterized by high‐crowned teeth. The spread of hipparionine horses is associated with increased seasonality and the expansion of open habitats. It is generally accepted that anchitheriine horses...
Rivers can act as both islands of mesic refugia for terrestrial organisms during times of aridification and barriers to gene flow, though evidence for long‐term isolation by rivers is mixed. Understanding the extent to which riverine barrier effects can be heightened for populations trapped in mesic refugia can help explain maintenance and generation of diversity in the face of Pleistocene climate...
Cope's Rule refers to the tendency of body size to increase along an evolutionary lineage. This rule is commonly tested by comparing size differences in pairs of taxa, one of which is assumed to be ancestral to the other. It has recently been pointed out that this approach fails to account for the unknown number of speciation events separating each pair. Here, a test that does account for this degree...
Several models have been proposed to suggest how the evolution of sex‐determining mechanisms might contribute to speciation. Here, we describe the inheritance of sex in 19 fish species from the rapidly evolving flock of cichlids in Lake Malawi, Africa. We found that many of these species have a male heterogametic (XY) system on linkage group 7. Some species also segregate for a female heterogametic...
Evolutionary models predict that parasite virulence (parasite‐induced host mortality) can evolve as a consequence of natural selection operating on between‐host parasite transmission. Two major assumptions are that virulence and transmission are genetically related and that the relative virulence and transmission of parasite genotypes remain similar across host genotypes. We conducted a cross‐infection...
Evolutionary game theory is a general mathematical framework that describes the evolution of social traits. This framework forms the basis of many multilevel selection models and is also frequently used to model evolutionary dynamics on networks. Kin selection, which was initially restricted to describe social interactions between relatives, has also led to a broader mathematical approach, inclusive...
Since Darwin published the “Origin,” great progress has been made in our understanding of speciation mechanisms. The early investigations by Mayr and Dobzhansky linked Darwin's view of speciation by adaptive divergence to the evolution of reproductive isolation, and thus provided a framework for studying the origin of species. However, major controversies and questions remain, including: When is speciation...
We explore the evolution of reliance on social and asocial learning using a spatially explicit stochastic model. Our analysis considers the relative merits of four evolved strategies, two pure strategies (asocial and social learning) and two conditional strategies (the “critical social learner,” which learns asocially only when copying fails, and the “conditional social learner,” which copies only...
Changes in expression of genes are thought to contribute significantly to evolutionary divergence. To study the relative role of selection and neutrality in shaping expression changes, we analyzed 24 genes in three different tissues of the house mouse (Mus musculus). Samples from two natural populations of the subspecies M. m. domesticus and M. m. musculus were investigated using quantitative PCR...
Cooperation should be favored under environmental conditions allowing the preferential interaction of cooperators among themselves and limiting interactions with defectors. Bacteria cooperating to kill competitors by secreting a toxin evolved during several hundred generations in two environments: a viscous environment that should promote cooperator assortment, and a nonviscous environment that should...
The disease caused by parasites and pathogens often causes sublethal effects that reduce host fecundity. Theory suggests that if parasites can “target” the detrimental effects of their growth on either host mortality or fecundity, they should always fully sterilize. This is because a reduction in host fecundity does not reduce the infectious period and is therefore neutral to a horizontally transmitted...