Biologists concerned with the evolutionary consequences of competition seem unaware a large literature on freshwater fishes that bears directly debates over ecological character displacement, release, and concept "empty niches." Only five potential instances displacement in teleosts are cited conceptually oriented literature, whereas data exist for 97 species comprising 52 genera 17 families. We review these studies, focusing lacustrine species, draw following conclusions. First, is...

Species that appear highly specialized on the basis of their phenotype (e.g., morphology, behavior, and physiology) also sometimes act as ecological generalists. This apparent paradox has been used to argue against importance competition a diversifying evolutionary force. We provide an alternative explanation based optimal foraging theory. Some resources are intrinsically easy use widely preferred, while others require phenotypic traits part consumer. asymmetry allows optimally consumers...

The phenotypic diversity exhibited within and among populations of freshwater fishes in postglacial lakes has intrigued biologists for two reasons: (i) their high variation (ii) the apparently recent rapid divergence forms. Genetic ecological studies these taxa are shedding new light on mechanisms species formation. Surprisingly, roles plasticity origins, maintenance, generation this system rarely directly addressed. We synthesize available literature morphological and, using a...

Most empirical studies of specialists and generalists have focused on comparisons among different species. Interspecific recently been criticized because phenotypic trade—offs can evolve after ecological specialization. As a result, it has suggested that intraspecific variation is the appropriate level to demonstrate functional trade—offs. We for two components fitness in pumpkinseed sunfish (Lepomis gibbosus) from single trophically polymorphic population: condition factor growth rate....

A little over one hundred years ago, Baldwin (1896, 1902) proposed that, it is the accommodations which set pace, lay out direction, and prophesy actual course of evolution. The idea that individual phenotypic responses to environment could influence a population's response selection facilitate adaptive evolution was also independently by Morgan (1896) Osborn (1896). logic what became known as effect modifications can potentially allow organisms survive reproduce in new environments, some...

Abstract I assessed habitat-specific foraging efficiency of shallow-water and open-water forms from a morphologically variable population threespine sticklebacks. Individuals sampled or habitats tend to be divergent, although the morphology modal form is intermediate between better-known benthic limnetic pairs stickleback species that coexist in other local lakes. tested two hypotheses about this intraspecific variation. First, heritable genetic variation body exists forms. Morphological...

Abstract Colonization of a novel environment is expected to result in adaptive divergence from the ancestral population when selection favors new phenotypic optimum. Local adaptation occurs through accumulation and integration character states that positively affect fitness. The role played by plastic traits has generally been ignored, except for variable environments. We propose if conditions relatively stable but induce phenotypically responses many traits, genetic variation exists form...

A trade-off is found between growth and the length of time male amphipods (Gammarus lawrencianus) spend in amplexus. Males spending majority amplexus showed 45% less than unamplexed males. The inability males to use their gnathopods feed while appears cause this reduced growth. Growth rates females appear unaffected by amplexus.Since size correlated with reproductive success G. lawrencianus, a decrease increment at next molt would represent similar loss incremental success. Male mating...

Many morphological, behavioral, physiological, and life-history traits covary across the biological scales of individuals, populations, species. However, processes that cause to also change over these scales, challenging our ability use patterns trait covariance infer process. Trait relationships are widely assumed have generic functional with similar evolutionary potentials, even though many different now identified, there is little appreciation may influence covariation evolution in unique...

While the importance of competition in adaptive divergence has recently been demonstrated a number systems, its interaction with other ecological factors neglected. We attempt more pluralistic approach this comparative study pumpkinseed sunfish (Lepomis gibbosus) from Adirondack region New York. In some lakes, forms that use shallow- and open-water environments coexist. tested four predictions relating to an hypothesis character release: (1) Pumpkinseed is favored absence closely related...

Little is known about phenotypic plasticity in guppies and whether it can take on functional roles as appears to other fishes. We tested for morphological Poecilia reticulata reared under different feeding orientations. Newborn from a stock population originating Trinidad were assigned one of five food treatments: (1) surface-floating food, or adhered plates; (2) at the surface facing down; (3) midwater vertically; (4) bottom up; (5) all four orientations alternate days. Male floating regime...

Abstract Morphological plasticity can influence adaptive divergence when it affects fitness components such as foraging performance. We induced morphological variation in pumpkinseed sunfish ( Lepomis gibbosus ) ecomorphs and tested for effects on Young‐of‐year from littoral pelagic lake habitats were reared each a ‘specialist diet’ representing their native habitat‐specific prey, or ‘generalist reflecting combination of non‐native prey. Specialist generalist diets, respectively, divergent...

Predation has important ecological and evolutionary consequences. Evolutionary responses to diversifying selection include genetic differentiation, the evolution of adaptive phenotypic plasticity, differentiation plastic between populations. We tested if pumpkinseed sunfish (Lepomis gibbosus) respond predation cues by changing their external body form in functionally sensible ways. then asked whether influenced divergence coexisting littoral pelagic ecomorphs, testing for divergent...

Classical Darwinian adaptation to a change in environment can ensue when selection favours beneficial genetic variation. How plastic trait responses new conditions affect this process depends on how plasticity reveals the influence of genotype phenotype. Genetic accommodation theory predicts that evolutionary rate may sharply increase induces and selects sufficient variation those produce an immediate response, but natural examples are rare. In Iceland, marine threespine stickleback have...

Variation in spatial complexity and foraging requirements between habitats can impose different cognitive demands on animals that may influence brain size. However, the relationship ecologically related performance size is not well established. We test whether variation relative region associated with habitat use within a population of pumpkinseed sunfish composed ecotypes inhabit either structurally complex shoreline littoral or simpler open-water pelagic habitat. Sunfish using have average...

A key requirement of effective fisheries management is a better understanding the mechanisms driving recruitment variability. Recent research suggests that quantity and quality gametes produced by fish closely linked to availability surplus energy, usually stored as lipid. We sampled mature walleye (Sander vitreus) from seven populations across Canada determine if indices reproductive effort were positively related adult nutrient reserves, primarily body lipid concentration. Populations...

Agonistic behavior between heterospecifics, in which individuals of one species attack another, may cause a subordinate to shift resource or habitat use. Subsequent evolutionary responses selection mimic shifts expected under ecological character displacement, but with no role played by exploitative competition. Alternatively, aggressive can evolve when fitness is improved excluding members coexisting from defendable through interference. We tested whether heterospecific agonistic has...