Sympostein V Evolution and Sex: The emergence of the sexes, sexual conflict and sexual selection

Coordinator:

Suhel Quader,
NCBS-TIFR,
Bangalore

Sexual Reproduction is a costly affair. There is the cost of having half  the population not reproduce, of the constraints on a genome that has to  support two different developmental programmes to build two very different phenotypes, of having to identify and attract a mate. These costs would have to be offset by a substantial gain in order for sexual reproduction to be selected for and exist to this day. We intend to explore the question - Why sex? Why does this costly strategy not only persist, but remain adopted by an overwhelmingly large proportion of complex, multi-cellular species today?

Given that there are two sexes; one is forced to also notice that the sexes are /different/. Most sexually reproducing species today, show anisogamy - literally, gametes produced by members of different sexes, are different. Producing many, inexpensive gametes v/s fewer, expensive gametes are strategies that call for different physiologies and behavioural strategies. Males and females can be very different, often  with competing (evolutionary) interests. We will touch upon sexual dimorphism at various levels, from genetics and molecular mechanisms of development, to behavioural differences. We will also try to draw general lessons about the conflict of interests between the sexes.

Another essential part of sexual reproduction is finding and attracting mates. The evolutionary success of an individual depends on how effectively it can gain access to gametes from the opposite sex. This  may involve impressing a female or seeking out her eggs or making  gametes that do so more effectively; or even a combination of all the above. The competition to attract mates gives rise to a special type of natural selection called sexual selection. Here, fitness is determined not just by the ability to survive, but the ability to compete in the search for mates (their gametes). Sexual selection sometimes leads to the emergence of otherwise mal-adaptive traits, such as the cumbersome and seemingly wasteful tail of the peacock. As part of our discussion on sexual selection, we will examine some other such, strange examples and some of the theories that attempt to explain them.

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