Dynamics Fridays Talk: Theories for the Evolution of the Sexes
Speaker: Priya Iyer
Venue: Simons Centre Ground Floor, NCBS
I will talk about theories for the evolution of differences between the sexes at various levels-- gamete sizes, dioecy and secondary sexual traits:
Anisogamy-- the difference in sperm and egg sizes-- is the first step to define the differentiation between the sexes. Anisogamy can evolve from isogamy to maximize both the probability of fertilization and zygote viability.
By mapping hermaphrodism and dioecy (species with sperm and egg production by same versus different individuals respectively) and fertilization modes over animal phylogenetic tree, we find both hermaphrodism and external fertilization to be primitive and dieocy and internal fertilization to be derived. This motivates a model of males evolving for “home delivery” of sperm, leading to the evolution of dioecy from hermaphrodism. We propose a model for secondary sexual traits or ornaments that avoids the paradox of lek by not alluding to genetic benefits. Instead we propose that these traits could evolve as admission tickets into resource controlling cliques, hence we are able to predict the occurrence and cost of ornaments based on resource distribution. A common thread that runs through all these models is the emphasis on cooperation rather than conflict between the sexes as the necessity for successful offspring production.