Artificial selection in guppies: male and female phenotypes produced by inter- and intrasexual selection

Inter- and intrasexual selection are often assumed to push phenotypes in similar directions, but this must not always be the case. The current study used two artificial selection treatments in an attempt to disentangle the effects of inter- and intrasexual selection in the guppy (Poecilia reticulata). The first artificial treatment (inter) was maintained by selecting males that were most appealing to prospective females; in the second treatment (intra), only the most dominant males were allowed to reproduce. Male morphology, aggression, and reproductive behaviour, as well as female choice and reproductive behaviour were compared between intra- and inter-treatment. After three generations of artificial selection, inter-males varied more in their orange colouration pattern than did intra-males. This may indicate that male orange colouration is subject to negative frequency dependent selection by means of female choice in the inter-treatment. Females preferred inter-males, regardless of their own selection history. These results question the seldom tested assumption that intra- and intersexual selection reinforce the same characters. The lack of direct benefits for choosing a dominant male are hypothesized to be at the basis of this discrepancy, since male guppies do not defend territories and do not provide resources to mates.