Looks are important to experienced male guppies

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Having experience with the ladies makes male guppies (Poecilia reticulata) pickier, according to a study to be published in a forthcoming issue of the journal Evolution.

Lyndon Jordan and Robert Brooks came to this conclusion after conducting a series of experiments to examine the effects of different social environments on subsequent mating behaviour and mate preferences in male guppies.

The authors manipulated variation in female quality in their experiments by housing males with either three medium-sized females (no variation), or with one small, medium and large female (high variation).

They also manipulated encounter rate by either presenting a male with all three females throughout the six-day conditioning period (simultaneous encounters), or by presenting only one female at a time (sequential encounters).

The male guppies were divided into groups of 12, and members of each group were subject to one of four treatment combinations for conditioning: sequential/variation (each male was housed with a single female that was replaced with a female of a different size every simulated day); sequential/no variation (as before, but the females used were always of medium size); simultaneous/variation (each male was housed with three females of different sizes at the same time, and the females replaced by another set of three females of varying sizes every simulated day) and simultaneous/no variation (as before, but the females used were always of medium size).

After six days of conditioning, the authors recorded the mating behaviour and preferences of the males by introducing them to a tank containing three females of different sizes (one each of small, medium and large) and observing the fish for 10 minutes.

The authors found that male guppies that had been sequentially housed with a single female fish (by extension, those that encountered females less frequently) courted females more aggressively than those that had been housed with multiple females. They also found that male fish exposed to females of differing sizes were more likely to court large (i.e. more attractive) females than those exposed to females of only one size.

According to senior author Lyndon Jordan: "Our findings suggest that males make sophisticated assessments of their social environment to determine their best reproductive strategy."

"It seems these male guppies are able to assess their social environment and tailor their courtship strategies to best suit their conditions.  When males expect, for example, that future mating opportunities will be rare – because in their recent past they have been – they seize every opportunity that presents itself."

"Males also seem to change their minds about what represents a good potential mate. If they have recently seen many attractive females, they concentrate on courting attractive females, whereas males who have not seen attractive females do not pass up an opportunity with a less attractive mate."

For more information, see the paper: Jordan, LA and RC Brooks (2011) Recent social history alters male courtship preferences. Evolution doi:10.1111/j.1558-5646.2011.01421.x

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