Title

The reproductive ecology of two wrasses: A focus on reproductive variation in females

Date of Completion

January 2005

Keywords

Biology, Ecology|Biology, Zoology|Agriculture, Fisheries and Aquaculture

Degree

Ph.D.

Abstract

Variation in female reproductive performance is observed within and among individuals and populations, as well as across space and time. Female investment in reproduction is often higher than that of males so it is not surprising that females alter reproductive performance in response to their environment in an effort to maximize fitness. Studying variation among females can be informative to such fields as conservation biology and behavioral ecology. ^ I investigated variation in female reproductive performance of two wrasse species: tautog (Tautoga onitis) and pink-belly wrasse ( Halichoeres margaritaceus). Wrasses are a diverse family of fish with complex reproductive behaviors and life histories. I examined the influence of female size and time of season on batch fecundity, spawning frequency, and season duration in tautog. Batch sizes and spawning frequency peaked mid-season in all female size-classes, and both were higher in large than small females; as a result, large females produced 50 times more eggs over a season than small females, indicating that the former make a disproportionate contribution to the pool of offspring and merit focused conservation measures. I also found that tautog in Connecticut produced more eggs than reported for tautog in Virginia, suggesting potential latitudinal or genetic effects. ^ Variation in female mating roles was investigated in the pink-belly wrasse. In most mating systems, females play the role of 'chooser' and not expected to have conspicuous mating displays; nonetheless female nuptial signals (FNSs) are observed in many taxa. I investigated whether red belly coloration and bob behavior were FNSs in pink-belly wrasses, and changed according to environmental or social conditions. Red belly coloration and bob behavior functioned as a complex FNS advertising spawning readiness, and variation in local conditions (e.g. predation pressure) may explain observed geographical differences. Although local social conditions (density of subordinate males) can affect female reproductive behavior of some wrasses, this was not observed in pink-belly wrasses. Characteristics of the FNSs (bob rate and belly color intensity) were conserved despite changes in local abundance of subordinate males, suggesting that females advertise spawning readiness indiscriminately. ^