Amorous introduced guppies harassing native Skiffia for sex

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Non-native guppies (Poecilia reticulata) are endangering the long-term survival of the native Mexican livebearer Skiffia bilineata by sexually harassing them, according to a study published in the most recent issue of the journal Biology Letters.

The study by Alejandra Valero, Constantino Garcia and Anne Magurran observed the interactions of male and female guppies with female Skiffia placed in an observation tank.

The authors varied the ratios of the three species and counted the number of times the male guppies displayed at, or attempted to copulate with, female Skiffia each time.

They found the male guppies to persistently court female Skiffia, even when there were more female guppies were in the tank than female Skiffia.

Because the two species cannot hybridize and produce viable offspring, the authors surmise that the attractiveness of the female Skiffia to the male guppy is caused by the more slender caudal peduncle in Skiffia, which makes the females look deeper-bodied (and hence gravid).

Since male guppies are attracted to large (and gravid) females, this feature of the female Skiffia makes them hyper-attractive to male guppies (even to the exclusion of female guppies present at the same time).

The amorous attentions of the male guppies are detrimental to the well-being of the female Skiffia, writes the authors. oodeid females vibrate vigorously when approached by courting males or aggressive females, which increases oxygen consumption at such timesInterspecific courtship may also attract predators and reduce feeding rate.

Additionally, the guppy s hooked gonopodium can cause injury to conspecific females during mating. It is probable that goodeid females, lacking defences against hooked gonopodia, will suffer cloacal damage during mating attempts.

The authors conclude uppies have invaded multiple sites in Mexico, including the last few remaining localities of some endangered goodeids. Of the approximately 36 species of Mexican goodeids, three are already extinct (or extinct in the wild) with many others threatened.

Skiffia bilineata has suffered local extinctions in more than 50% of sites where it was previously present. Small populations, already at risk through stochastic processes, may be most susceptible to the adverse effects of heterospecific courtship.

For more information, see the paper: Valero, A, CM Garcia and AE Magrurran (2008) Heterospecific harassment of native endangered fishes by invasive guppies in Mexico. Biology Letters 4, pp. 149"152.