Biology subjects

Fuller, R. C.

Publications and source records attributed to Fuller, R. C..

4 recordsLinked to original sources

bioRxiv2018

Agonistic character displacement of genetically based male color patterns across darters

A growing number of studies are demonstrating that interspecific male-male competitive interactions can promote trait evolution and contribute to speciation. Agonistic character displacement (ACD) occurs when selection to avoid maladaptive interspecific aggression leads to the evolution of agonistic signals and/or associated behavioral biases in sympatry. Here we test for a pattern consistent with ACD in male color pattern in darters (Percidae: Etheostoma). Despite the presence of traditional sex roles and sexual dimorphism, male color pattern has been shown to function in male-male competition in several darter species, rather than female mating preferences. A pattern consistent with divergent ACD in male behavioral biases has also been documented in darters. Males bias their aggression towards conspecific over heterospecific males in sympatry but not in allopatry. Here we use a common garden approach to show that differences in male color pattern among four closely related darter species are genetically based. We also demonstrate that male color pattern exhibits enhanced differences in sympatric compared to allopatric populations of two darter species. This study provides evidence that interspecific male-male aggressive interactions alone can promote elaborate male signal evolution both between and within species. We discuss the implications this has for male-driven ACD and cascade ACD.

evolutionary biology↗

bioRxiv2018

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. Alternatively, 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. However, as with many long-lived organisms, the fitness of second generation hybrids has not been assessed because raising animals to adulthood in the lab is challenging. Recently, reinforcement of male preferences has been implicated in darters because male preference for conspecific females is high in sympatry but absent in allopatry in multiple species pairs. The hypothesis that reinforcement accounts for behavioral isolation in sympatry assumes that hybridization and postzygotic isolation are present. Here, we used genomic and morphological data to demonstrate that hybridization is ongoing between orangethroat and rainbow darters and used hybrids collected from nature to measure postzygotic barriers across two hybrid generations. We observed sex ratio distortion in adult F1s and a dramatic reduction in backcross survival. Our findings indicate that selection to avoid hybridization promotes the evolution of male-driven behavioral isolation via reinforcement in this system.

evolutionary biology↗

bioRxiv2017

Egg viability decreases rapidly with time since ovulation in the rainbow darter: implications for the costs of choosiness

Egg viability in the rainbow darter Etheostoma caeruleum, a fish apparently lacking female mate choice, was found to decline rapidly after ovulation. We observed that the majority of a females clutch may fail to hatch if she is prevented from mating for as little as six hours. These data suggest that exercising female mate preferences may be selectively disfavoured in E. caeruleum due to the high cost of delaying mating.

animal behavior and cognition↗

bioRxiv2017

Male-driven reinforcement and cascade reinforcement in darters

Reinforcement can act in response to maladaptive hybridization by selecting for increased discrimination against heterospecifics mates in sympatry compared to allopatry (i.e., reproductive character displacement - RCD). Additionally, reinforcement can select for increased discrimination against heterospecifics in a fighting context in sympatry compared to allopatry (i.e., agonistic character displacement - ACD). Because it directly affects conspecific recognition traits (signals and/or preferences), reinforcement between two species in sympatry can incidentally cause behavioral isolation among populations within a species, termed cascade reinforcement. Here we demonstrate that a pattern consistent with male-driven RCD and ACD is present between two groups of darters (orangethroat darter clade Ceasia and rainbow darter Etheostoma caeruleum). Increased male discrimination against heterospecific females as mates and increased male discrimination against heterospecific males as competitors is present in sympatry. Furthermore, there is a pattern consistent with male-driven cascade RCD and cascade ACD within Ceasia. We found low levels of discrimination between two species of Ceasia that occur in allopatry from one another and in allopatry with E. caeruleum. This result contrasts that of a recent study which observed high levels of behavioral isolation between Ceasia species that occurred in sympatry with E. caeruleum. We suggest reinforcement between Ceasia and E. caeruleum in sympatry has led to the evolution of behavioral isolation between lineages within Ceasia that occur in sympatry with E. caeruleum but in allopatry with respect to one another (i.e., cascade reinforcement). This study demonstrates the ability of male behavior to simultaneously drive sympatric and allopatric speciation via reinforcement.

evolutionary biology↗