Fitness maps to a large-effect locus in introduced stickleback populations.

Mutations of small effect underlie most adaptation to new environments, but beneficial variants with large fitness effects are expected to contribute under certain conditions. Genes and genomic regions having large effects on phenotypic differences between populations are known from numerous taxa, but fitness effect sizes have rarely been estimated. We mapped fitness over a generation in an F2 intercross between a marine and a lake stickleback population introduced to a freshwater pond.

Dysglycemia in Pregnancy and Maternal/Fetal Outcomes.

Maternal dysglycemia-including diabetes, impaired glucose tolerance, and impaired fasting glucose-affects one in six pregnancies worldwide and represents a significant health risk to the mother and the fetus. Maternal dysglycemia is an independent risk factor for perinatal mortality, major congenital anomalies, and miscarriages. Furthermore, it increases the longer-term risk of type 2 diabetes mellitus, metabolic syndrome, cardiovascular morbidity, malignancies, and ophthalmic, psychiatric, and renal diseases in the mother.

Sex as a Biological Variable: A 5-Year Progress Report and Call to Action.

A little over 5 years ago, the U.S. National Institutes of Health (NIH) announced the intention to develop policies to require applicants to report plans to balance male and female cells and animals in preclinical investigations.

Taking cardiology clinical trials to the next level: A call to action.

Physicians previously perceived heart disease to be a man's disease; yet, since 1984, more women have died of ischemic heart disease. Because women who develop obstructive coronary heart disease and heart failure tend to do so 10 years later than men, cardiology clinical trials that use arbitrary age cutoffs or exclusion criteria based on comorbidities and polypharmacy often limit the pool of potential participants to a greater extent for women. Issues related to trial design and insufficient accounting for female-predominant disease patterns have contributed to low rates of enrollment of women in certain domains of cardiology research.

Genetic Coupling of Female Mate Choice with Polygenic Ecological Divergence Facilitates Stickleback Speciation.

Ecological speciation with gene flow is widespread in nature [1], but it presents a conundrum: how are associations between traits under divergent natural selection and traits that contribute to assortative mating maintained? Theoretical models suggest that genetic mechanisms inhibiting free recombination between loci underlying these two types of traits (hereafter, "genetic coupling") can facilitate speciation [2-4]. Here, we perform a direct test for genetic coupling by mapping both divergent traits and female mate choice in a classic model of ecological speciation: sympatric benthic and limnetic threespine stickleback (Gasterosteus aculeatus). By measuring mate choice in F2 hybrid females, we allowed for recombination between loci underlying assortative mating and those under divergent ecological selection.

Trophic evolution in African citharinoid fishes (Teleostei: Characiformes) and the origin of intraordinal pterygophagy.

The African freshwater suborder Citharinoidei (Characiformes) includes 110 species that exhibit a diversity of feeding modes comparable to those characteristic of more speciose groups such its sister, the Characoidei (2000+ species) or the distantly related Cichlidae (1600+ species). Feeding habits of the Citharinoidei range from generalist omnivores to highly specialized feeding modes including ectoparasitic fin-eating, i.e.

Extent of QTL Reuse During Repeated Phenotypic Divergence of Sympatric Threespine Stickleback.

How predictable is the genetic basis of phenotypic adaptation? Answering this question begins by estimating the repeatability of adaptation at the genetic level. Here, we provide a comprehensive estimate of the repeatability of the genetic basis of adaptive phenotypic evolution in a natural system. We used quantitative trait locus (QTL) mapping to discover genomic regions controlling a large number of morphological traits that have diverged in parallel between pairs of threespine stickleback (Gasterosteus aculeatus species complex) in Paxton and Priest lakes, British Columbia.

Genetics of ecological divergence during speciation.

Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Although this process is a major generator of biodiversity, its genetic basis is still poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions.

Maintenance of a genetic polymorphism with disruptive natural selection in stickleback.

The role of natural selection in the maintenance of genetic variation in wild populations remains a major problem in evolution. The influence of disruptive natural selection on genetic variation is especially interesting because it might lead to the evolution of assortative mating or dominance [1, 2]. In theory, variation can persist at a gene under disruptive natural selection, but the process is little studied and there are few examples [3, 4].

The probability of genetic parallelism and convergence in natural populations.

Genomic and genetic methods allow investigation of how frequently the same genes are used by different populations during adaptive evolution, yielding insights into the predictability of evolution at the genetic level. We estimated the probability of gene reuse in parallel and convergent phenotypic evolution in nature using data from published studies. The estimates are surprisingly high, with mean probabilities of 0.

Comparable ages for the independent origins of electrogenesis in African and South American weakly electric fishes.

One of the most remarkable examples of convergent evolution among vertebrates is illustrated by the independent origins of an active electric sense in South American and African weakly electric fishes, the Gymnotiformes and Mormyroidea, respectively. These groups independently evolved similar complex systems for object localization and communication via the generation and reception of weak electric fields. While good estimates of divergence times are critical to understanding the temporal context for the evolution and diversification of these two groups, their respective ages have been difficult to estimate due to the absence of an informative fossil record, use of strict molecular clock models in previous studies, and/or incomplete taxonomic sampling.

Neural innovations and the diversification of African weakly electric fishes.

In African mormyrid fishes, evolutionary change in a sensory region of the brain established an ability to detect subtle variation in electric communication signals. In one lineage, this newfound perceptual ability triggered a dramatic increase in the rates of signal evolution and species diversification. This particular neural innovation is just one in a series of nested evolutionary novelties that characterize the sensory and motor systems of mormyrids, the most speciose group of extant osteoglossomorph fishes.

Brain evolution triggers increased diversification of electric fishes.

Communication can contribute to the evolution of biodiversity by promoting speciation and reinforcing reproductive isolation between existing species. The evolution of species-specific signals depends on the ability of individuals to detect signal variation, which in turn relies on the capability of the brain to process signal information. Here, we show that evolutionary change in a region of the brain devoted to the analysis of communication signals in mormyrid electric fishes improved detection of subtle signal variation and resulted in enhanced rates of signal evolution and species diversification.

Signal variation and its morphological correlates in Paramormyrops kingsleyae provide insight into the evolution of electrogenic signal diversity in mormyrid electric fish.

We describe patterns of geographic variation in electric signal waveforms among populations of the mormyrid electric fish species Paramormyrops kingsleyae. This analysis includes study of electric organs and electric organ discharge (EOD) signals from 553 specimens collected from 12 localities in Gabon, West-Central Africa from 1998 to 2009. We measured time, slope, and voltage values from nine defined EOD "landmarks" and determined peak spectral frequencies from each waveform; these data were subjected to principal components analysis.

Old gene duplication facilitates origin and diversification of an innovative communication system--twice.

The genetic basis of parallel innovation remains poorly understood due to the rarity of independent origins of the same complex trait among model organisms. We focus on two groups of teleost fishes that independently gained myogenic electric organs underlying electrical communication. Earlier work suggested that a voltage-gated sodium channel gene (Scn4aa), which arose by whole-genome duplication, was neofunctionalized for expression in electric organ and subsequently experienced strong positive selection.

Remarkable morphological stasis in an extant vertebrate despite tens of millions of years of divergence.

The relationship between genotypic and phenotypic divergence over evolutionary time varies widely, and cases of rapid phenotypic differentiation despite genetic similarity have attracted much attention. Here, we report an extreme case of the reverse pattern--morphological stasis in a tropical fish despite massive genetic divergence. We studied the enigmatic African freshwater butterfly fish (Pantodon buchholzi), whose distinctive morphology earns it recognition as a monotypic family.

Sexual signal evolution outpaces ecological divergence during electric fish species radiation.

Natural selection arising from resource competition and environmental heterogeneity can drive adaptive radiation. Ecological opportunity facilitates this process, resulting in rapid divergence of ecological traits in many celebrated radiations. In other cases, sexual selection is thought to fuel divergence in mating signals ahead of ecological divergence.

Ongoing ecological divergence in an emerging genomic model.

Much of Earth's biodiversity has arisen through adaptive radiation. Important avenues of phenotypic divergence during this process include the evolution of body size and life history (Schluter 2000). Extensive adaptive radiations of cichlid fishes have occurred in the Great Lakes of Africa, giving rise to behaviours that are remarkably sophisticated and diverse across species.

Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa.

Electric signals of mormyrid fishes have recently been described from several regions of Africa. Members of the Mormyridae produce weak electric organ discharges (EODs) as part of a specialized electrosensory communication and orientation system. Sympatric species often express distinctive EODs, which may contribute to species recognition during mate choice in some lineages.

Size-dependent use of territorial space by a rock-dwelling cichlid fish.

Territoriality fundamentally influences animal mating systems and patterns of population structure. Although territory ownership is already known to contribute importantly to male reproductive success and the ecological coexistence of African rock-dwelling cichlids, the significance of variation in territory features has received little attention in these fishes. In Lake Malawi, males of Pseudotropheus tropheops "orange chest" defend territories on either of two substrate classes at Harbour Island: flat rock slabs lacking crevices and caves, or structurally complex boulder fields containing cave shelters.

Time-domain signal divergence and discrimination without receptor modification in sympatric morphs of electric fishes.

Polymorphism in an animal communication channel provides a framework for studying proximate rules of signal design as well as ultimate mechanisms of signal diversification. Reproductively isolated mormyrid fishes from Gabon's Brienomyrus species flock emit distinctive electric organ discharges (EODs) thought to function in species and sex recognition. Species boundaries and EODs appear congruent in these fishes, with the notable exception of three morphs designated types I, II and III.

Electric organ discharge patterns during group hunting by a mormyrid fish.

Weakly electric fish emit and receive low-voltage electric organ discharges (EODs) for electrolocation and communication. Since the discovery of the electric sense, their behaviours in the wild have remained elusive owing to their nocturnal habits and the inaccessible environments in which they live. The transparency of Lake Malawi provided the first opportunity to simultaneously observe freely behaving mormyrid fish and record their EODs.

Multiple cases of striking genetic similarity between alternate electric fish signal morphs in sympatry.

Striking trait polymorphisms are worthy of study in natural populations because they can often shed light on processes of phenotypic divergence and specialization, adaptive evolution, and (in some cases) the early stages of speciation. We examined patterns of genetic variation within and between populations of mormyrid fishes that are morphologically cryptic in sympatry but produce alternate types of electric organ discharge (EOD). Other species in a large group containing a clade of these morphologically cryptic EOD types produce stereotyped, species-typical EOD waveforms thought to function in mate recognition.