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Why organisms diversify into discrete species instead of showing a continuum of genotypic and phenotypic forms is an important yet rarely studied question in speciation biology. Does species discreteness come from adaptation to fill discrete niches or from interspecific gaps generated by reproductive isolation? We investigate the importance of reproductive isolation by comparing genetic discreteness,...
Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations...
The magnitude and extent of global change during the Cenozoic is remarkable, yet the impacts of these global changes on the biodiversity and evolutionary dynamics of species diversification remain poorly understood. To investigate this question, we combine paleontological and neontological data for the angiosperm order Fagales, an ecologically important clade of about 1370 species of trees with an...
Many classic examples of adaptive radiations take place within fragmented systems such as islands or mountains, but the roles of mosaic landscapes and variable gene flow in facilitating species diversification is poorly understood. Here we combine phylogenetic and landscape genetic approaches to understand diversification in Darwin's finches, a model adaptive radiation. We combined sequence data from...
We use forward and coalescent models of population genetics to study chromosome fusions that reduce the recombination between two locally adapted loci. Under a continent–island model, a fusion spreads and reaches a polymorphic equilibrium when it causes recombination between locally adapted alleles to be less than their selective advantage. In contrast, fusions in a two‐deme model always spread; whether...
Understanding how parasites adapt to changes in host resistance is crucial to evolutionary epidemiology. Experimental studies have demonstrated that parasites are more capable of adapting to gradual, rather than sudden changes in host phenotype, as the latter may require multiple mutations that are unlikely to arise simultaneously. A key, but as yet unexplored factor is precisely how interactions...
Populations evolve in response to the external environment, whether abiotic (e.g., climate) or biotic (e.g., other conspecifics). We investigated how adaptation to biotic, heritable environments differs from adaptation to abiotic, nonheritable environments. We found that, for the same selection coefficients, the coadaptive process between genes and heritable environments is much faster than genetic...
Natural selection is expected to cause convergence of life histories among taxa as well as correlated evolution of different life‐history traits. Here, we quantify the extent of convergence of five key life‐history traits (adult fire survival, seed storage, degree of sexual dimorphism, pollination mode, and seed‐dispersal mode) and test hypotheses about their correlated evolution in the genus Leucadendron...
Extra‐pair copulation (EPC) is widespread in socially monogamous species, but its evolutionary benefits remain controversial. Indirect genetic benefit hypotheses postulate that females engage in EPC to produce higher quality extra‐pair offspring (EPO) than within‐pair offspring (WPO). In contrast, the sexual conflict hypothesis posits that EPC is beneficial to males but not to females. Thus, under...
Sexual dimorphism describes substantial differences between male and female phenotypes. In spiders, sexual dimorphism research almost exclusively focuses on size, and recent studies have recovered steady evolutionary size increases in females, and independent evolutionary size changes in males. Their discordance is due to negative allometric size patterns caused by different selection pressures on...
Natural selection can act against maladaptive hybridization between co‐occurring divergent populations leading to evolution of reproductive isolation among them. A critical unanswered question about this process that provides a basis for the theory of speciation by reinforcement, is whether natural selection can cause hybridization rates to evolve to zero. Here, we investigated this issue in two sibling...
The Black Queen Hypothesis (BQH) was originally proposed to explain the dependence of some marine bacteria on helper organisms for protection from hydrogen peroxide (HOOH). The BQH predicts that selection for the evolutionary loss of leaky functions from individuals can produce commensal or mutualistic interactions. We demonstrated the leakiness of HOOH detoxification by complementing a HOOH‐sensitive...
By selecting codistributed, closely related montane sedges from the Rocky Mountains that are similar in virtually all respects but one—their microhabitat affinities—we test predictions about how patterns of genetic variation are expected to differ between Carex nova, an inhabitant of wetlands, and Carex chalciolepis, an inhabitant of drier meadows, slopes, and ridges. Although contemporary populations...
A major goal of speciation research is to understand the processes involved in the earliest stages of the evolution of reproductive isolation (RI). One important challenge has been to identify systems where lineages have very recently diverged and opportunities for hybridization are present. We conducted a comprehensive examination of the components of RI across the life cycle of two subspecies of...
Island evolution may be expected to involve fast initial morphological divergence followed by stasis. We tested this model using the dental phenotype of modern and ancient common voles (Microtus arvalis), introduced onto the Orkney archipelago (Scotland) from continental Europe some 5000 years ago. First, we investigated phenotypic divergence of Orkney and continental European populations and assessed...
Male ejaculates include large amounts of seminal fluid proteins (Sfps) that influence male sperm competitive success. In spite of their diverse proximate functions, Sfps involved in sperm competition increase male fitness in one of three ways: (1) “avoidance” proteins help males avoid sperm competition, (2) “defense” proteins help males defend their sperm from displacement by the female's subsequent...
Warning signals within species, such as the bright colors of chemically defended animals, are usually considered mutualistic, monomorphic traits. Such a view is however increasingly at odds with the growing empirical literature, showing nontrivial levels of signal variation within prey populations. Key to understanding this variation, we argue, could be a recognition that toxicity levels frequently...
The geographic ranges of closely related species can vary dramatically, yet we do not fully grasp the mechanisms underlying such variation. The niche breadth hypothesis posits that species that have evolved broad environmental tolerances can achieve larger geographic ranges than species with narrow environmental tolerances. In turn, plasticity and genetic variation in ecologically important traits...
Phylogenetic niche conservatism (PNC) and convergence are contrasting evolutionary patterns that describe phenotypic similarity across independent lineages. Assessing whether and how adaptive processes give origin to these patterns represent a fundamental step toward understanding phenotypic evolution. Phylogenetic model‐based approaches offer the opportunity not only to distinguish between PNC and...
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