Risk of predation as a promoting factor of species divergence in threespine sticklebacks (Gasterosteus aculeatus L.) (original) (raw)
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Ecology and Evolution, 2013
Eco-evolutionary responses of natural populations to spatial environmental variation strongly depend on the relative strength of environmental differences/ natural selection and dispersal/gene flow. In absence of geographic barriers, as often is the case in lake ecosystems, gene flow is expected to constrain adaptive divergence between environmentsfavoring phenotypic plasticity or high trait variability. However, if divergent natural selection is sufficiently strong, adaptive divergence can occur in face of gene flow. The extent of divergence is most often studied between two contrasting environments, whereas potential for multimodal divergence is little explored. We investigated phenotypic (body size, defensive structures, and feeding morphology) and genetic (microsatellites) structure in threespine stickleback (Gasterosteus aculeatus) across five habitat types and two basins (North and South) within the geologically young and highly heterogeneous Lake M yvatn, North East Iceland. We found that (1) North basin stickleback were, on average, larger and had relatively longer spines than South basin stickleback, whereas (2) feeding morphology (gill raker number and gill raker gap width) differed among three of five habitat types, and (3) there was only subtle genetic differentiation across the lake. Overall, our results indicate predator and prey mediated phenotypic divergence across multiple habitats in the lake, in face of gene flow.
Ecology and Evolution, 2013
Eco-evolutionary responses of natural populations to spatial environmental variation strongly depend on the relative strength of environmental differences/ natural selection and dispersal/gene flow. In absence of geographic barriers, as often is the case in lake ecosystems, gene flow is expected to constrain adaptive divergence between environmentsfavoring phenotypic plasticity or high trait variability. However, if divergent natural selection is sufficiently strong, adaptive divergence can occur in face of gene flow. The extent of divergence is most often studied between two contrasting environments, whereas potential for multimodal divergence is little explored. We investigated phenotypic (body size, defensive structures, and feeding morphology) and genetic (microsatellites) structure in threespine stickleback (Gasterosteus aculeatus) across five habitat types and two basins (North and South) within the geologically young and highly heterogeneous Lake M yvatn, North East Iceland. We found that (1) North basin stickleback were, on average, larger and had relatively longer spines than South basin stickleback, whereas (2) feeding morphology (gill raker number and gill raker gap width) differed among three of five habitat types, and there was only subtle genetic differentiation across the lake. Overall, our results indicate predator and prey mediated phenotypic divergence across multiple habitats in the lake, in face of gene flow.
Animal behaviour, 2015
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, Gasterostues aculeatus L., in which isolated populations encounter a variety of predation regimes. Oceanic stickleback, which represent the ancestral founders of the freshwater radiation, encounter many piscivorous fish. Derived, freshwater populations, on the other hand, vary with respect to the presence of predators. Some populations encounter native salmonids, whereas others have not experienced predation by large fish in thousands of generations (relax-selected populations). Some relax-selected populations have had sport fish, including rainbow trout, Oncorhynchus mykiss, introduced within ...
Biological Journal of the Linnean Society, 2015
Morphometric differentiation among freshwater fish populations is a commonplace occurrence, although the underlying causes for this divergence often remain elusive. We analysed the degree and patterns of morphological differentiation among nine freshwater three-spined stickleback (Gasterosteus aculeatus) populations inhabiting isolated karst rivers of the Adriatic Sea basin, to characterise the phenotypic diversity and differentiation in these populations. The analyses revealed marked and significant morphometric differentiation -especially in traits related to predator defence amongst most populations -even among those located within close geographic proximity in the same catchment system. Accordingly, the degree of morphometric and neutral genetic differentiation, as assessed from variability in 15 microsatellite loci from a parallel study, were uncorrelated across the populations. However, PST/FST comparisons revealed that the degree of phenotypic differentiation (PST) among populations exceeded that to be expected from genetic drift alone, suggesting a possible adaptive basis for the observed differentiation. In fact, avian predation pressure and several physiochemical environmental variables were identified as the main putative drivers of the observed differentiation, particularly in the dorsal spines, ascending process and lateral plates. Hence, the high degree of morphometric differentiation among Adriatic three-spined stickleback populations appears to reflect adaptation to local ecological conditions.
Morphological segregation of Icelandic threespine stickleback (Gasterosteus aculeatus L
Biological Journal of The Linnean Society, 2002
Icelandic threespine sticklebacks show parallel sympatric morphological differences related to different substrate habitats in four Icelandic lakes. The level of morphological diversification varies among the lakes, ranging from a population with a wide morphological distribution to a population with clear resource morphs, where morphological diversification was reflected in diet differences. These differences in morphological divergence are closely related to the differences in the ecological surroundings of each population. This appears to be resource polymorphism, which may lead to population differentiation and speciation. Trophically related sexual dimorphism was also common in these sticklebacks, which is possibly the result of sexual selection or habitat segregation by the sexes. 0
Intraguild Predation Drives Evolutionary Niche Shift in Threespine Stickleback
Evolution, 2012
Intraguild predation-competition and predation by the same antagonist-is widespread, but its evolutionary consequences are unknown. Intraguild prey may evolve antipredator defenses, superior competitive ability on shared resources, or the ability to use an alternative resource, any of which may alter the structure of the food web. We tested for evolutionary responses by threespine stickleback to a benthic intraguild predator, prickly sculpin. We used a comparative morphometric analysis to show that stickleback sympatric with sculpin are more armored and have more limnetic-like body shapes than allopatric stickleback. To test the ecological implications of this shift, we conducted a mesocosm experiment that varied sculpin presence and stickleback population of origin (from one sympatric and one allopatric lake). Predation by sculpin greatly increased the mortality of allopatric stickleback. In contrast, sculpin presence did not affect the mortality of sympatric stickleback, although they did have lower growth rates suggesting increased nonpredatory effects of sculpin. Consistent with their morphology, sympatric stickleback included more pelagic prey in their diets, leading to depletion of zooplankton in the mesocosms. These findings suggest that intraguild prey evolution has altered food web structure by reducing both predation by the intraguild predator and diet overlap between species.
Environmental Biology of Fishes, 2014
Human-induced processes like eutrophication are increasing water turbidity and altering vegetated habitats in the Baltic Sea. Unfortunately, the influence of these environmental changes on predator-prey interactions remains poorly studied in mobile taxa of this region. We used three-spined stickleback (Gasterosteus aculeatus) as a model species to study the combined effects of turbidity and shoot density on habitat choice (shelter vs. open) in the presence and absence of piscivorous perch (Perca fluviatilis). Habitat choice of sticklebacks was video-monitored and compared between two paired observation periods: "control" (no predator) and "risk" (predator present). Though sticklebacks exhibited a general preference for sheltered habitat across treatments, repeated measures ANOVA found that sticklebacks responded to predator presence by significantly increasing use of the sheltered habitat. However, shoot density of the shelter interacted with observation period, where risk-induced shifts of sticklebacks into sheltered habitat were most apparent and sustained at higher shoot densities. Stickleback activity level was generally reduced with predator presence at higher turbidity and shoot density levels, suggesting a possible adaptation to reduce predator encounter rates in visually deteriorated conditions. Overall, our study demonstrates that relatively minute increases (1's -10's of NTU) in algal turbidity intensify three-spined stickleback sheltered habitat use, but vegetation density may still play a larger role in avoiding predators at these turbidity levels. When compared with a similar study on 0+ perch, our work suggests that eutrophication (i.e., increased turbidity, loss of habitat complexity) may have variable, taxon-and/or habitat-specific effects on predator-prey interactions of the Baltic Sea.
Evolutionary Ecology Research, 2017
Background: Prey often make behavioural and morphological adaptations to avoid predation, and these alternative defence mechanisms may either compensate for, or reinforce, one another. Objective: We examined correlations between anti-predator behaviour and morphology in threespine stickleback fish (Gasterosteus aculeatus) in four environments distinguished by their predation histories: marine/anadromous populations co-existing with native predatory fish (representative of the ancestral environment), and three freshwater environments with native, introduced, and no predatory fish, respectively. To determine whether morphological and behavioural defences reinforce one another (trait co-specialization) or whether they represent alternative strategies for defence (trait compensation), we related morphology of laboratoryreared stickleback to the intensity of their responses to a simulated predator attack, which had previously been assessed (Wund et al., 2015). Methods: Eight aspects of s...
Evolutionary Ecology Research, 2002
In 1987, a fjord in the Snaefellsnes peninsula, northwest Iceland, was dammed and a freshwater lagoon formed. There is a large population of threespine stickleback in this lagoon. We compared morphological features of stickleback in the lagoon population to those of their marine ancestor, and morphological polymorphism within the lagoon in relation to mud and lava substrates. The freshwater stickleback have shorter spines and fewer armour plates than marine stickleback. There is also some morphological divergence between stickleback from the two substrates within the lagoon. Our results suggest that the threespine stickleback may adapt to a novel environment more rapidly than would be predicted from conventional models of biological differentiation.