Phenotypic Plasticity and Integration in the Mangrove Rivulus (Kryptolebias marmoratus): A Prospectus

Abstract

The mangrove rivulus (Kryptolebias marmoratus) is a small fish native to mangrove ecosystems in Florida, the Caribbean, Central America, and South America. This species is one of only two self-fertilizing, hermaphroditic vertebrates capable of producing offspring that are genetically identical to both the parent and all siblings. Long bouts of selfing result in individuals with completely homozygous genotypes, effectively allowing for the production of "clones." Rivulus is also extremely sensitive to environmental change, both during development and adulthood. Life-history traits, behavior, physiology, morphology, and even sexual phenotype are shaped to a large extent by the interaction of genes with the environment, and many of these traits appear to co-vary. True reaction norms can be generated for this species in much the same way as has been done for clonally reproducing invertebrates and plants that have contributed immensely to our understanding of the evolution of phenotypic plasticity. That is, rivulus provides the opportunity to place individuals with identical genotypes in many different environments at any point during ontogeny or adulthood. In addition, rivulus populations are characterized by high genotypic diversity, a luxury not afforded by many clonal vertebrates, which allows us to evaluate variation among genotypes in the shape of reaction norms and in patterns of covariance among traits. We provide background information on phenotypic plasticity and phenotypic integration, coupled with a description of characteristics that we feel qualify rivulus as a potentially powerful model in which to study the evolution of reaction norms and covariance among traits.

First record of a male of Kryptolebias hermaphroditus Costa, 2011 (Cyprinodontiformes: Cynolebiidae)

“…Primary males of Kryptolebias marmoratus can be readily produced in laboratories by inducing eggs to temperatures lower than those usually found in mangrove areas (<20°C), while secondary males can be induced by maintaining individuals at higher temperatures (>30°C), which are similar to those found on populations with higher rate of males (Turner et al, 2006;Earley et al, 2012). Their induction in the lab at naturally occurring temperatures suggests that, in the wild, secondary males may be the most ecologically relevant type of male (Turner et al, 2006).…”

“…The occurrence of self-fertilization in Kryptolebias marmoratus has made that species a popular model for population genetics, development, evolutionary biology, behavior, among others (for reviews see Earley et al, 2012;Taylor, 2012;Avise & Tatarenkov, 2015;Turko & Wright, 2015). Nonetheless, there have been relatively few studies on the South American lineage of K. hermaphroditus, possibly due to its misidentification as K. marmoratus (Seegers, 1984).…”

Better with your parasites? Lessons for behavioural ecology from evolved dependence and conditionally helpful parasites

“…We know that genetic variancesecovariances and, to a lesser extent, phenotypic correlation structure (integration) can drive or constrain evolutionary change (Dochtermann & Roff, 2010;Lande & Arnold, 1983) and influence the degree to which organisms are flexible/plastic in response to environmental change (Earley, Hanninen, Fuller, Garcia, & Lee, 2012;Ketterson et al, 2009;Schlichting, 1989). We also know that concentrations of some of the integrator molecules that are manipulated or otherwise affected by parasites exhibit heritable variation and, because these integrators often have pleiotropic effects, selection on integrator concentrations can drive wholesale changes to the phenotype and thus the variance upon which selection can act (Cox, McGlothlin, & Bonier, 2016).…”

Fish embryos on land: terrestrial embryo deposition lowers oxygen uptake without altering growth or survival in the amphibious fishKryptolebias marmoratus

“…Furthermore, mangrove rivulus possess a unique reproductive system, internal self-fertilization, which allows homozygous adult hermaphrodites to produce isogenic offspring (Harrington, 1961). The unique reproductive system of adults makes them an excellent model for studying how the environment affects development, as genetic differences can be eliminated (Turko et al, 2011;Earley et al, 2012).…”