I've noticed a similar (if much less involved) phenomenon when females have no males of their own species in their tank.  They're more likely to hybridize with closely related species than they would be if males of their own species were in the same aquarium.  They could be in the same tank with closely related species for years without hybridizing if males of their own species are present.  It's not a reliable method of preventing hybridization of course, but it's interesting nonetheless.

An Indirect Cue of Predation Risk Counteracts Female Preference for Conspecifics in a Naturally Hybridizing Fish Xiphophorus birchmanni

Pamela M. Willis, Gil G. Rosenthal, Michael J. Ryan

Abstract

Mate choice is context dependent, but the importance of current context to interspecific mating and hybridization is largely unexplored. An important influence on mate choice is predation risk. We investigated how variation in an indirect cue of predation risk, distance to shelter, influences mate choice in the swordtail Xiphophorus birchmanni, a species which sometimes hybridizes with X. malinche in the wild. We conducted mate choice experiments to determine whether females attend to the distance to shelter and whether this cue of predation risk can counteract female preference for conspecifics. Females were sensitive to shelter distance independent of male presence. When conspecific and heterospecific X. malinche males were in equally risky habitats (i.e., equally distant from shelter), females associated primarily with conspecifics, suggesting an innate preference for conspecifics. However, when heterospecific males were in less risky habitat (i.e., closer to shelter) than conspecific males, females no longer exhibited a preference, suggesting that females calibrate their mate choices in response to predation risk. Our findings illustrate the potential for hybridization to arise, not necessarily through reproductive ‘‘mistakes’’, but as one of many potential outcomes of a context-dependent mate choice strategy.