Visual Background Choice and Light Environment Affect Male Guppy Visual Contrast.

Male guppies () have multiple colored spots and perform courtship displays near the edges of streams in Trinidad in shallow water flowing through rainforest. Depending upon the orientation of the pair, the female sees the male displays against gravel or other stream bed substrates or against the spacelight-the roughly uniform light coming from the water column away from the bank. We observed courting pairs in two adjacent natural streams and noted the directions of each male display.

Polyphenisms and polymorphisms: Genetic variation in plasticity and color variation within and among bluefin killifish populations.

The presence of stable color polymorphisms within populations begs the question of how genetic variation is maintained. Consistent variation among populations in coloration, especially when correlated with environmental variation, raises questions about whether environmental conditions affect either the fulcrum of those balanced polymorphisms, the plastic expression of coloration, or both. Color patterns in male bluefin killifish provoke both types of questions.

Revisiting old truths: The evolution of male coloration in guppies as a function of predation.

The Trinidadian guppy, Poecilia reticulata, is a long-studied model for the evolution of trade-offs in male nuptial coloration as a function of female mating preferences vs. predation risk. Previous work suggests that female mating preferences favour the evolution of increased conspicuous male coloration in low predation populations.

The visual ecology of selective predation: Are unhealthy hosts less stealthy hosts?

Predators can strongly influence disease transmission and evolution, particularly when they prey selectively on infected hosts. Although selective predation has been observed in numerous systems, why predators select infected prey remains poorly understood. Here, we use a mathematical model of predator vision to test a long-standing hypothesis about the mechanistic basis of selective predation in a -microparasite system, which serves as a model for the ecology and evolution of infectious diseases.

Asymmetric reinforcement in killifish: assessing reproductive isolation when both sexes choose.

Reinforcement can occur when maladaptive hybridization in sympatry favors the evolution of conspecific preferences and target traits that promote behavioral isolation (BI). In many systems, enhanced BI is due to increased female preference for conspecifics. In others, BI is driven by male preference, and in other systems both sexes exert preferences.

Sequence Analysis and Ontogenetic Expression Patterns of Cone Opsin Genes in the Bluefin Killifish (Lucania goodei).

Sensory systems allow for the transfer of environmental stimuli into internal cues that can alter physiology and behavior. Many studies of visual systems focus on opsins to compare spectral sensitivity among individuals, populations, and species living in different lighting environments. This requires an understanding of the cone opsins, which can be numerous.

A potential role for overdominance in the maintenance of colour variation in the Neotropical tortoise beetle, Chelymorpha alternans.

The presence of persistent polymorphisms within natural populations elicits the question of how such polymorphisms are maintained. All else equal, genetic drift and natural selection should remove genetic variants from populations. Disassortative mating and overdominance are potential mechanisms for maintaining variation within populations.

Genomic landscape of reproductive isolation in Lucania killifish: The role of sex loci and salinity.

Adaptation to different environments can directly and indirectly generate reproductive isolation between species. Bluefin killifish (Lucania goodei) and rainwater killifish (L. parva) are sister species that have diverged across a salinity gradient and are reproductively isolated by habitat, behavioural, extrinsic and intrinsic post-zygotic isolation.

Genomic Resources for Darters (Percidae: Etheostominae) Provide Insight into Postzygotic Barriers Implicated in Speciation.

Comparative genomic approaches are increasingly being used to study the evolution of reproductive barriers in nonmodel species. Although numerous studies have examined prezygotic isolation in darters (Percidae), investigations into postzygotic barriers have remained rare due to long generation times and a lack of genomic resources. Orangethroat and rainbow darters naturally hybridize and provide a remarkable example of male-driven speciation via character displacement.

Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers.

Once recombination is halted between the X and Y chromosomes, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about the variation in sex chromosome differentiation within clades. Here, we combined whole-genome and transcriptome sequencing data to characterize the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies.

Seeing red: color vision in the largemouth bass.

How animals visually perceive the environment is key to understanding important ecological behaviors, such as predation, foraging, and mating. This study focuses on the visual system properties and visual perception of color in the largemouth bass . This study (1) documents the number and spectral sensitivity of photoreceptors, (2) uses these parameters to model visual perception, and (3) tests the model of color perception using a behavioral assay.

Testing the potential mechanisms for the maintenance of a genetic color polymorphism in bluefin killifish populations.

The maintenance of genetic variation in the face of natural selection is a long-standing question in evolutionary biology. In the bluefin killifish , male coloration is polymorphic. Males can produce either red or yellow coloration in their anal fins, and both color morphs are present in all springs.

Hybridization and postzygotic isolation promote reinforcement of male mating preferences in a diverse group of fishes with traditional sex roles.

Behavioral isolation is thought to arise early in speciation due to differential sexual and/or natural selection favoring different preferences and traits in different lineages. Instead, behavioral isolation can arise due to reinforcement favoring traits and preferences that prevent maladaptive hybridization. In darters, female preference for male coloration has been hypothesized to drive speciation, because behavioral isolation evolves before F1 inviability.

The vertical distributions and spawning site choices of red and yellow bluefin killifish Lucania goodei colour morphs.

A genetic colour polymorphism is present in bluefin killifish Lucania goodei, where red and yellow anal-fin morphs coexist in clear springs, but the source of balancing selection is unknown. In a field study, vertical distributions did not differ between the morphs and there was little evidence that light environments differed qualitatively over the 200 cm at which fish were collected. A greenhouse study showed that both morphs preferred to spawn at shallow depths and hence vertical distribution and spawning site choice are unlikely to explain the maintenance of the colour polymorphism.

Variation in individual temperature preferences, not behavioural fever, affects susceptibility to chytridiomycosis in amphibians.

The ability of wildlife populations to mount rapid responses to novel pathogens will be critical for mitigating the impacts of disease outbreaks in a changing climate. Field studies have documented that amphibians preferring warmer temperatures are less likely to be infected with the fungal pathogen (). However, it is unclear whether this phenomenon is driven by behavioural fever or natural variation in thermal preference.

The pervasive effects of lighting environments on sensory drive in bluefin killifish: an investigation into male/male competition, female choice, and predation.

Sensory drive predicts that the conditions under which signaling takes place have large effects on signals, sensory systems, and behavior. The coupling of an ecological genetics approach with sensory drive has been fruitful. An ecological genetics approach compares populations that experience different environments and asks whether population differences are adaptive and are the result of genetic and/or environmental variation.

Agonistic character displacement of genetically based male colour patterns across darters.

Agonistic character displacement (ACD) occurs when selection to avoid maladaptive interspecific aggression leads to the evolution of agonistic signals and/or associated behavioural biases in sympatry. Here, we test for a pattern consistent with ACD in male colour pattern in darters (Percidae: ). Male colour pattern has been shown to function in male-male competition rather than female mating preferences in several darter species.

Male-driven reproductive and agonistic character displacement in darters and its implications for speciation in allopatry.

Selection against hybridization can cause mating traits to diverge between species in sympatry via reproductive character displacement (RCD). Additionally, selection against interspecific fighting can cause aggressive traits to diverge between sympatric species via agonistic character displacement (ACD). By directly affecting conspecific recognition traits, RCD and ACD between species can also incidentally cause divergence in mating and fighting traits among populations within a species [termed cascade RCD (CRCD) and cascade ACD].

Using Human Vision to Detect Variation in Avian Coloration: How Bad Is It?

Assessing variation in animal coloration is difficult, as animals differ in their visual system properties. This has led some to propose that human vision can never be used to evaluate coloration, yet many studies have a long history of relying on human vision. To reconcile these views, we compared the reflectance spectra of preserved avian plumage elements with two measures that are human biased: RGB values from digital photographs and the corresponding reflectance spectra from a field guide.

Male and female contributions to behavioral isolation in darters as a function of genetic distance and color distance.

Determining which reproductive isolating barriers arise first between geographically isolated lineages is critical to understanding allopatric speciation. We examined behavioral isolation among four recently diverged allopatric species in the orangethroat darter clade (Etheostoma: Ceasia). We also examined behavioral isolation between each Ceasia species and the sympatric rainbow darter Etheostoma caeruleum.

Exploring visual plasticity: dietary carotenoids can change color vision in guppies (Poecilia reticulata).

Differences in color vision can play a key role in an organism's ability to perceive and interact with the environment across a broad range of taxa. Recently, species have been shown to vary in color vision across populations as a result of differences in regulatory sequence and/or plasticity of opsin gene expression. For decades, biologists have been intrigued by among-population variation in color-based mate preferences of female Trinidadian guppies.