Sex recognition by pupfish: who are female mimics fooling?
Species, sex and mate-quality recognition are vital to maximizing individual reproductive success. In male Comanche Springs pupfish (Cyprinodon elegans), small males have morphological and behavioral characteristics similar to females. Female mimicry may allow them to avoid aggression by larger territorial males and garner matings in a large males territory. However, selection is predicted to favor large males ability to discriminate against female mimics as they may usurp fertilizations in a males territory and potentially eat eggs fertilized by the territory owner. Results of a field study conducted at Balmorhea State Park, Balmorhea, TX show that territorial males behaviorally discriminate based on size and sex. They are more aggressive to large males than to female mimics. Additionally, territorial males discriminate against female mimics, directing more aggressive behaviors to female mimics than similarly sized females. These results suggest that female mimicry may not be an effective tactic for small males. However, as female mimics garner little aggression when a large male intruder is also present, they will potentially gain opportunities to spawn if large males commonly intrude into males territories. These results imply that complex interactions among males expressing alternative mating tactics may have important evolutionary consequences in fitness for both territorial males and female mimics.
Neighbor interactions among male Cyprinodon elegans: Does size influence the development of “dear enemy” recognition?
Territorial males of many pupfish species exhibit dear enemy recognition, displaying less aggression to neighbors than to unfamiliar intruders. Familiarity may play a role in the development of dear enemy recognition if established neighbors save time and energy through decreased aggression. This hypothesis predicts that a territory owner decreases the intensity of aggressive responses to neighbors over time. I tested this prediction in male Cyprinodon elegans. Males have conditional alternative reproductive tactics with larger males defending territories around spawning sites, intermediate males as non-territorial satellites and smaller males as sneakers with female-like morphologies. The largest males in a population are territorial, but in absolute size; they may be intermediate or small. Therefore, aggressive behaviors and neighbor interactions were assessed across the time period of territory establishment for large, intermediate and small males. Selection for dear enemy recognition may be stronger on large males compared to intermediate and small males that do not typically hold territories in natural populations.
Causes and consequences of population decline in an endangered pupfish, Cyprinodon bovinus
When intrasexual interactions influence reproductive success, declines in population size may alter individual reproductive success as well as the breeding system of the species. The endangered Leon Springs pupfish, Cyprinodon bovinus, has a breeding system where large males defend territories around female oviposition sites, while smaller males show satellite or sneaker tactics to gain matings. In related species, absence of territorial males results in satellites taking over territorial vacancies. However, despite a decline in number of territorial males, we observed an altered breeding system with satellites not becoming territorial. Territorial males with neighbors have few heterospecific intruders and we hypothesize territoriality is no longer beneficial to satellites due to the lack of interaction with territorial neighbors. We examine the costs of both strategies in number of intruders present at spawning and benefits in number of spawnings. In addition, large numbers of a pupfish egg predator, the endangered Gambusia nobilis, may be contributing to the decline of C. bovinus. We discuss management implications when one endangered species threatens another.