The threespine stickleback, Gasterosteus aculeatus , has undergone dramatic increases in abundance in parts of its historical native range, and it is also undergoing a major range expansion. We review available information and discuss the vectors and sources of the species' range expansions, the genetic characteristics of recently founded populations and the ecological consequences of both stickleback introductions and increases in abundance. Dramatic range expansions occurred in the Caspian Sea drainage, large rivers in the Black Sea drainage, reservoirs of the Rhine basin, isolated lakes in North America and Japan and remote islands in the Arctic. Likely reasons for these range expansions include canal construction, accidental inclusion with stocking of commercially valuable fish, intentional release by aquarists and fishermen and climate change. In some cases, range expansions of stickleback were likely facilitated by genetic admixture of previously separated lineages, as well as by high‐standing genetic variation that promotes rapid adaptation to new habitats. Accordingly, range expansions are often accompanied by striking increases in abundance, although these are two distinct processes. Notably, population growth within the species' native range, particularly in the White and Baltic Seas, has been observed alongside expansions into new areas. Where stickleback colonise new habitats or increase in abundance, extensive ecological impacts on ecosystems typically occur. Given these massive and widespread changes, the species has the potential to provide considerable insight into the evolutionary and ecological effects of human impacts on aquatic ecosystems.

This study addresses the problem of concordance in fluctuating asymmetry (FA) across traits by analyzing the relationship between FAs and the mean values of character measurements in a set of morphological traits. Regression slopes vary in natural populations, thus, revealing discordance in FA across traits among these populations. Hence, commonly accepted techniques for measuring developmental instability with FA result in uncertainties. Here, I relate FA to mean as a two-dimensional complex to demonstrate the uniformly negative slopes of standardized FA vs. mean value regressions for sets of morphological traits from eighteen distinct natural marine and aquatic populations. Comprehensive analysis of the FA–mean complex cannot be recommended for wide use in assessing stress and fitness, but it offers promise to improve FA measuring methodologies and to better understand the nature of developmental instability.

Studies of dietary preferences of migratory species are of great importance as these species connect trophic webs of habitats across the route of migration and thus represent trophic relationships between the spatially disjointed communities. Here we describe dietary preferences of the White Sea threespine stickleback Gasterosteus aculeatus during the spawning season using stable isotope and stomach content analyses. Both analyses indicated that during the spawning season, when sticklebacks spend most of the time in the nearshore, their diet significantly consist of benthic species in contrast to the start of the spawning season when fishes migrating from the offshore are feeding on zooplankton. Also, we show that stickleback eggs contribute greatly to the diet of both male and female fishes. Using Bayes mixing modelling we show that dietary preferences in females were broader than in males, and more variable during the spawning season. Males fed on eggs almost completely while guarding their nests. Both stomach contents and isotope signatures demonstrate that by the end of the spawning season sticklebacks again increase consumption of plankton, and isotope analysis proved to be more reliable tool to trace this change than stomach content analysis. Our results show that stable isotope and stomach content analyses well supplement each other in understanding of seasonal changes in dietary composition of stickleback.

Empirical studies of phenotypic variation show that genetic and environmental heterogeneity account for only part of it. Usually, the magnitude of the residual variation is comparable with that of the genetic component, while notably exceeding the magnitude of the environmental component. This can be interpreted in two ways. A deterministic interpretation associates it with artifacts such as measurement error and genetic and environmental heterogeneity that is unaccounted for. An indeterministic interpretation argues that it is random or stochastic phenotypic variation (SPV) resulting from developmental instability - a developing organism's inability to produce a consistent phenotype in a given environment. Classical example of debates between determinists and indeterminists took place about a century ago in quantum physics. In discussing Heidelberg's Uncertainty Principle, Einstein metaphorically expressed his deterministic position: 'God does not play dice with universe'. The indeterministic Uncertainty Principle, however, was eventually widely accepted. Currently, most biologists implicitly or explicitly support deterministic interpretations of phenotypic variation patterns. Here, a wide range of data on morphological traits (studied with analysis of fluctuating asymmetry) and non-morphological traits are analyzed to provide evidence that SPV is not an artifact, but a valid phenomenon. This evidence supports conclusions that observed associations between SPV and stress can be analyzed in the framework of dynamic energy budget theory, and are inextricably linked through energy homeostasis.