Female choice for good genes and sex-biased broods in guppies

In a population of guppies Poecilia reticulata females were found to prefer large mates and the offspring of these males had a higher survival rate th an those sired by smaller mates, suggesting that females were selecting the ir mates on the basis of their good genes. The possibility that females dif ferentially invested in mate or female offspring depending on the size or a ttractiveness of their mate was also investigated, but no relationship was found between a male's attractiveness or body size and the sex ratio of the offspring he sired, However, a strong female-biased sex ratio was detected in the broods and the proportion of males produced decreased with the amou nt of time that a female was confined with a male. The possible reasons for this are discussed. (C) 2001 The Fisheries Society of th British Isles.