Academics

Friends and Parasites

Hughes KA, Du L, Rodd HF, and Reznick DN. 1999. Familiarity Leads to Female Mate Preference for Novel Males in the Guppy, Poecilia reticulata. The Association for the Study of Animal Behavior 58: 907-916

Kelley JL, Graves JA, and Magurran AE. 1999. Familiarity Breeds Contempt in Guppies. Nature 401: 661-662

Lopez S. 1998. Acquired Resistance Affects Male Sexual Display and Female Choice in Guppies. Proceedings of the Royal Society of London 265: 717-723

Lopez S. 1999. Parasitized Female Guppies Do Not Prefer Showy Males. Animal Behavior 57: 1129-1134

Friends

In guppies, it has been observed that there are differences within populations in respect to male color patterns. These differences are related to mating success, female mate preference and predation risk. Guppies are able to maintain genetic variation by favoring rare phenotypes over common ones. The next two articles deal with the issue of preference for unfamiliar mates.
The article by Kelley, Graves and Magurran entitled "Familiarity breeds contempt in guppies," discusses the preference of male guppies for familiar versus unfamiliar female guppies. They used two populations of guppies, one where they are confined to isolated pools and therefore encounter the same females and the other, where they inhabit open rivers and so continually search for new mates. They set up their experiment so that half of the males in each population encountered females from their own school, while the other half encountered a new school. The results showed that the confined males directed more courtship towards unfamiliar females whereas the guppies from the open rivers did not have a significant preference for unfamiliar females. These findings are significant because it shows how males maximize their mating success, whether in the wild or in a confined pool. Also, this kind of behavior probably increases gene flow.

The article by Hugheset al. entitled, "Familiarity leads to female mate preference for novel males in the guppy, Poecilia reticulata," discusses a similar issue, but focuses on female, rather than male preference. They explore the idea that mate choice is one factor helping to maintain extreme within population genetic variation regarding male color. This study tested the preference of females for males with a novel or rare color pattern. They used a technique to avoid the rare male effect by using a "familiarization" period. During a trial, they showed females a common male color pattern and later showed then alternative male patterns in equal numbers. Their results supported that females were significantly more likely to mate with males that possessing novel color patterns than with males which had unfamiliar color patterns. This indicates that females alter their choice of mates according to what they have been exposed to. These results are significant because they can be related to theories of sexual selection in that this frequency dependent selection could help maintain genetic variation in male color patterns.

In conclusion, the results of both studies are related to each other. The implication of these studies is that neither male nor female guppies want to mate with their siblings or familiar mates. They want to maximize their mating opportunities by moving around and looking for mates possessing rare phenotypes. They want diversity in their population. They want to increase the gene flow by mating with different partners.

Parasites

The next two articles focus on parasites. The difference between the two articles is that the first one deals with parasitized female preference, whereas the second one deals with female preference for resistant males. Parasites affect female choice by either altering her decision making process or by imposing an energetic constrain on her.

The next article by Lopez entitled " Parasitized Female Guppies do not Prefer Showy Males," discusses how parasites affect female hosts, specifically their mate choice. Virgin females were exposed to the parasite Gyrodactylus turnbulli and allowed to choose between an attractive and unattractive male simultaneously. The results showed that the infected females did not have a preference for the showy male or the less showy male. This contrasted with the control (uninfected) females, which did show a significant preference for the showy male. The infected females showed a reduced activity level, implying the energy constraint due to the presence of parasites. The significance of these results is that sexual selection pressure decreases with regard to male showiness.

The article also by Lopez entitled "Acquired Resistance Affects Male Sexual Display and Female Choice in Guppies," discusses the idea that males which have extravagant displays are signaling their resistance to parasites to females. The study examined male orange color, sigmoid display, and female preference for males, before and after a primary challenge infection of males. It was found that resistant males display more than non-resistant ones with regard to sigmoid displays, glides, and male attractiveness. These results are significant because they suggest that once an immunity to parasites is acquired by a male, he is then able to put more effort into sexual activities and reproductive success should increase.

In conclusion, both of these studies are related to each other. They both imply that when either female guppies or male guppies are infected, they are preferred less by their partners. The first study implies that infected females are less discriminatory in choosing their mate compared to healthy ones. This means that male guppies do not want to mate with female that would bring infected children. They want to mate with healthy ones so they can have healthy family. The second study implies that males resistant to the parasite have more energy to display than males that are non-resistant. The males with genetic ability to establish immunity can afford higher costs for sexual characteristics than males that lack ability to build up resistance.