Variation in predation pressure as a mechanism underlying differences in numerical abundance between populations of the poeciliid fish Heterandria formosa

2015

Self Cite

Studies of the adaptive significance of variation among conspecific populations often focus on a single ecological factor. However, habitats rarely differ in only a single ecological factor, creating a challenge for identifying the relative importance of the various ecological factors that might be maintaining local adaptation. Here we investigate the ecological factors associated with male body shape variation among nine populations of the poeciliid fish, Heterandria formosa, from three distinct habitats and combine those results with a laboratory study of three of those populations to assess the contributions of genetic and environmental influences to shape variation. Field‐collected animals varied principally in three ways: the orientation of the gonopodium, the intromittent organ; the degree of body depth and streamlining; and the shape of the tail musculature. Fish collected in the spring season were larger and had a more anteriorly positioned gonopodium than fish collected in autumn. Fish collected from lotic springs were larger and more streamlined than those collected from lentic ponds or tidal marshes. Some of the variation in male shape among populations within habitats was associated with population‐level variation in species richness, adult density, vegetative cover, predation risk, and female standard length. Population‐level differences among males in body size, position of the gonopodium, and shape of the tail musculature were maintained among males reared in a common environment. In contrast, population variation in the degree of streamlining was eliminated when males were reared in a common environment. These results illustrate the complicated construction of multivariate phenotypic variation and suggest that different agents of selection have acted on different components of shape.

“…2006; MacRae and Travis 2014). On average marshes have slightly higher levels of species richness than the other habitats because of their higher diversity of fishes.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…2006; Schrader and Travis 2012; MacRae and Travis 2014). The timing of the biannual census marks the beginning (late spring) and end (early autumn) of the H. formosa breeding season.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…2000, 2009; Soucy and Travis 2003; Richardson et al. 2006; Schrader and Travis 2009; Schrader et al. 2011; MacRae and Travis 2014; Hale and Travis 2015).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Shape variation in the least killifish: ecological associations of phenotypic variation and the effects of a common garden

Landy

2015

Self Cite

Plastic maternal effects of social density on reproduction and fitness in the least killifish, Heterandria formosa

Levell

Bedgood

2023

Self Cite

Environmental parental effects, also known as transgenerational plasticity, are widespread in plants and animals. Less well known is whether those effects contribute to maternal fitness in the same manner in different populations. We carried out a multigenerational laboratory experiment with females drawn from two populations of the least killifish, Heterandria formosa, to assess transgenerational plasticity in reproductive traits in response to differences in social density and its effects on maternal fitness. In the first and second generations, increased density decreased reproductive rate and increased offspring size in females from both populations. There were complicated patterns of transgenerational plasticity on maternal fitness that differed between females from different populations. Females from a population with historically low densities whose mothers experienced lower density had higher fitness than females whose mothers experienced higher density, regardless of their own density. The opposite pattern emerged in females from the population with historically high densities: Females whose mothers experienced higher density had higher fitness than females whose mothers experienced lower density. This transgenerational plasticity is not anticipatory but might be considered adaptive in both populations if providing those “silver spoons” enhances offspring fitness in all environments.

Assessing the roles of population density and predation risk in the evolution of offspring size in populations of a placental fish

Schrader

2012

Self Cite

Population density is an ecological variable that is hypothesized to be a major agent of selection on offspring size. In high-density populations, high levels of intraspecific competition are expected to favor the production of larger offspring. In contrast, lower levels of intraspecific competition and selection for large offspring should be weaker and more easily overridden by direct selection for increased fecundity in low-density populations. Some studies have found associations between population density and offspring size consistent with this hypothesis. However, their interpretations are often clouded by a number of issues. Here, we use data from a 10-year study of nine populations of the least killifish, Heterandria formosa, to describe the associations of offspring size with habitat type, population density, and predation risk. We found that females from spring populations generally produced larger offspring than females from ponds; however, the magnitude of this difference varied among years. Across all populations, larger offspring were associated with higher densities and lower risks of predation. Interestingly, the associations between the two ecological variables (density and predation risk) and offspring size were largely independent of one another. Our results suggest that previously described genetic differences in offspring size are due to density-dependent natural selection.