The timing and development of infections in a fish-cestode host-parasite system.

The cestode is a common parasite in freshwater threespine stickleback populations, imposing strong fitness costs on their hosts. Given this, it is surprising how little is known about the timing and development of infections in natural stickleback populations. Previous work showed that young-of-year stickleback can get infected shortly after hatching.

Effects of predation risk on egg steroid profiles across multiple populations of threespine stickleback.

Predation often has consistent effects on prey behavior and morphology, but whether the physiological mechanisms underlying these effects show similarly consistent patterns across different populations remains an open question. In vertebrates, predation risk activates the hypothalamic-pituitary-adrenal (HPA) axis, and there is growing evidence that activation of the maternal HPA axis can have intergenerational consequences via, for example, maternally-derived steroids in eggs. Here, we investigated how predation risk affects a suite of maternally-derived steroids in threespine stickleback eggs across nine Alaskan lakes that vary in whether predatory trout are absent, native, or have been stocked within the last 25 years.

Replicated evolutionary inhibition of a complex ancestral behaviour in an adaptive radiation.

Adaptive radiations often exhibit high levels of phenotypic replication, a phenomenon that can be explained by selection on standing variation in repeatedly divergent environments or by the influence of ancestral plasticity on selection in divergent environments. Here, we offer the first evidence that plastic loss of expression of a complex display in a novel environment, followed by selection against expression, could lead to replicated evolutionary inhibition of the phenotype. In both ancestral (oceanic) and benthic (freshwater) populations of the threespine stickleback fish, cannibalism is common and males defending nests respond to approaching groups with a complex diversionary display.

Evolution of steroid hormones in reproductive females of the threespine stickleback fish.

Hormones play a prominent role in animal development, mediating the expression of traits and coordinating phenotypic responses to the environment. Their role as physiological integrators has implications for how populations respond to natural selection and can impact the speed and direction of evolutionary change. However, many emerging and established fish models with the potential to be ecologically or evolutionarily informative are small-bodied, making hormone sampling through traditional methods (whole-body or plasma) lethal or highly disruptive.

The evolution of antipredator behaviour following relaxed and reversed selection in Alaskan threespine stickleback fish.

Changing environments, whether through natural or anthropogenic causes, can lead to the loss of some selective pressures ('relaxed selection') and possibly even the reinstatement of selective agents not encountered for many generations ('reversed selection'). We examined the outcome of relaxed and reversed selection in the adaptive radiation of the threespine stickleback fish, L., in which isolated populations encounter a variety of predation regimes.

Evolutionary Influences of Plastic Behavioral Responses Upon Environmental Challenges in an Adaptive Radiation.

At the end of the 19th century, the suggestion was made by several scientists, including J. M. Baldwin, that behavioral responses to environmental change could both rescue populations from extinction (Baldwin Effect) and influence the course of subsequent evolution.

Relaxed selection in the wild.

Natural populations often experience the weakening or removal of a source of selection that had been important in the maintenance of one or more traits. Here we refer to these situations as 'relaxed selection,' and review recent studies that explore the effects of such changes on traits in their ecological contexts. In a few systems, such as the loss of armor in stickleback, the genetic, developmental and ecological bases of trait evolution are being discovered.

A test of the "flexible stem" model of evolution: ancestral plasticity, genetic accommodation, and morphological divergence in the threespine stickleback radiation.

If an ancestral stem group repeatedly colonizes similar environments, developmental plasticity specific to that group should consistently give rise to similar phenotypes. Parallel selection on those similar phenotypes could lead to the repeated evolution of characteristic ecotypes, a property common to many adaptive radiations. A key prediction of this "flexible stem" model of adaptive radiation is that patterns of phenotypic divergence in derived groups should mirror patterns of developmental plasticity in their common ancestor.

Parallel evolution of dwarf ecotypes in the forest tree Eucalyptus globulus.

Three small populations of a dwarf ecotype of the forest tree Eucalyptus globulus are found on exposed granite headlands in south-eastern Australia. These populations are separated by at least 100 km. Here, we used 12 nuclear microsatellites and a chloroplast DNA marker to investigate the genetic affinities of the dwarf populations to one another and to their nearest populations of tall E.

Evolution in parallel: new insights from a classic system.

Neo-darwinists have long argued that parallel evolution, the repeated evolution of similar phenotypes in closely related lineages, is caused by the action of similar environments on alleles at many loci of small effect. A more controversial possibility is that the genetic architecture of traits initiates parallelism, sometimes through fixation of alleles of large effect. Recent research (by Cole et al.

Size-dependent territory defense by a damselfish : A determinant of resource use by group-foraging surgeonfishes.

Three adult size classes of the territorial Caribbean dusky damselfish,Stegastes dorsopunicans, are differently distributed with respect to habitat, and with respect to the biomass of filamentous algal turfs in the areas they defend. The density of large individuals is positively correlated with the decalcified dry biomass of these turfs, whereas the densities of medium and small individuals are inversely related to algal biomass. Density of the urchin,Diadema, is also inversely correlated with algal biomass.