We studied detour responses of male mosquitofish faced with a vertical-bar barrier through which a group of females was visible. Mosquitofish showed a consistent population bias to detour the barrier preferentially leftwise when a straight barrier was used, whilst the asymmetry disappeared if a U-shaped barrier was used. The leftward bias was apparent even when using a simulated-predator as a t...

Genetic analyses contribute to studies of biological invasions by mapping the origin and dispersal patterns of invasive species occupying new territories. Using microsatellite loci, we assessed the genetic diversity and spatial population structure of mosquitofish (Gambusia holbrooki) that had invaded Spanish watersheds, along with the American locations close to the suspected potential source ...

Understanding the invasion success of alien species includes developing knowledge on how biological traits their populations respond to spatial differences in environmental conditions. For invasive fishes, while influence latitudinal and climatic gradients over large scales is well established, there less certainty these vary smaller scales. Here, we tested a geographic gradient reproductive bo...

Females of many species mate with multiple males during the course of a single round of reproduction (Davies, 1991; Birkhead & Mùller, 1992). However, secure estimates of the frequency of concurrent multiple paternity in most cases awaited the application of molecular markers (Avise, 1994) that permit documentation of when copulations result in fertilizations such that individual broods are mul...

Previous laboratory studies have demonstrated that estrogenic and antiandrogenic chemicals can alter several sexual characteristics in male poeciliid fishes. Whether similar disturbances occur under field conditions remains to be confirmed. Lake Apopka, Florida, is contaminated with numerous chemicals, some of which possess endocrine-disrupting activity. Male mosquitofish (Gambusia holbrooki) w...

The preference for melanistic males was studied in two populations of eastern mosquitofish (Gambusia holbrooki, Pisces: Poeciliidae), one from Florida and one from northern Italy. Melanism in the eastern mosquitofish is a Y--linked character, expressed in males only. Melanistic males have black spots varying in size and number. In the Florida population, melanistic males are common, whereas in ...

The present study investigated whether fluctuating asymmetry can serve as a useful biomarker of environmental stress in the eastern mosquitofish (Gambusia holbrooki). Fluctuating asymmetry was measured in sexually mature females sampled from two Florida, USA, coastal streams: The Fenholloway River, which is dominated by effluent from a paper mill, and Spring Creek, a tributary to the Fenhollowa...