Heritability and evolvability of meristic characters in a natural population of Gasterosteus aculeatus

Phenotypic and genetic variabilities of nine meristic traits (in threespine stickleback, Gasterosteus aculeatus) were calculated for 33 full-sib families raised under controlled laboratory conditions and for 33 pairs caught in nature. Heritabilities were measured using three methods: regression (across environments, laboratory-nature), full sib (laboratory), and minimum estimate (nature). Evolvabilities, as an alternative measure of genetic variability, were computed from the genetic coefficient of variation across environments, in the laboratory, and in nature. In general terms, phenotypic variability was smaller in laboratory-reared fish than in wild fish. Results applying both parameters (heritability and evolvability) suggest that in the natural environment, there is a relevant presence of additive genetic variability for lateral-plate number and, to a lesser extent, for lower gill rakers, as well as maternal effects on caudal and abdominal vertebrae and paternal effects on dorsal fin rays. Some of the meristic traits examined are bilateral. Heritabilities across environments and in the laboratory for fluctuating asymmetry values were calculated according to conventional methods and also employing method 2 of Falconer. Qualitatively, the results were almost the same using the two methods: most heritability values were around zero, even taking into account overall measures of fluctuating asymmetry.