Abstract
In nest-building fish species, mature males often exhibit one of two alternative reproductive behaviours. Bourgeois males build nests, court females, and guard their eggs. Parasitic cuckolders attempt to steal fertilizations from bourgeois males and do not invest in parental care. Previous evidence from the bluegill sunfish (Lepomis macrochirus) suggests that adult males are morphologically specialized for these two tactics. Here, we used microsatellite markers to determine genetic parentage in a natural population of the spotted sunfish (L. punctatus) that also displayed both bourgeois and parasitic male morphs. As gauged by relative investments in gonadal vs. somatic tissues, between 5 and 15% of the mature adult males were parasites. Multi-locus genotypes were generated for more than 1400 embryos in 30 nests, their nest-guardian males, and for other adults in the population. Progeny in approximately 57% of the nests were sired exclusively by the guardian male, but the remaining nests contained embryos resulting from cuckoldry as well. Overall, the frequency of offspring resulting from stolen fertilizations was only 1.3%, indicating that the great majority of paternity is by bourgeois nesting males. With regard to maternity, 87% of the nests had at least three dams, and computer simulations estimate that about 7.2 dams spawned per nest.
Highlights
Organisms have evolved varied mating strategies in response to selection pressures promoting reproductive success
Based on morphology and colouration, no male reproductive parasites were observed in the study population and bourgeois males sired over 90% of the embryos surveyed (DeWoody et al 1998). These findings suggest that reproductive parasitism in L. auritus probably stems from bourgeois males themselves
Two more parasitic cuckolders were collected during the course of broader fish collections, and gonadosomatic index (GSI) for these fish are included in Fig. 1 for illustrative purposes
Summary
Organisms have evolved varied mating strategies in response to selection pressures promoting reproductive success. The evolution and maintenance of alternative reproductive strategies within a sex has received considerable attention (see for example, Zimmerer & Kallman 1989; Gross 1991; Lucas & Howard 1995). One such classic example of alternative mating strategies among males involves the bluegill sunfish Lepomis macrochirus (Gross 1979; Dominey 1980). As many as 85% of the reproductively active males display the parasitic lifestyle (Gross 1982)
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