Incorporating an ontogenetic perspective into evolutionary theory of sexual size dimorphism

Chun-Chia Chou1 , Yoh Iwasa2 , Takefumi Nakazawa1
(1Natl. Cheng Kung Univ.,2Kyushu Univ.)

2015/3/24, 14:50- at The 1st meeting room of the Biology Department

      Sexual size dimorphism (SSD) describes divergent body size of adult males and females in a species. Several hypotheses (e.g., niche variation hypothesis, fecundity selection, and sexual selection) have been proposed to explain evolution of SSD. Besides, it is already known that SSD occurs because individuals undergo sex-specific ontogenetic growth trajectories. However, how growth trajectories evolve and result in SSD under sex-specific selection and life history trade-offs remains unsolved. To elucidate this, I extend a quantitative genetic model through redefining fitness of individuals with accelerated growth rate or delayed maturation, two primary traits generating adult body size. Benefits of larger males and females are higher mating success and fecundity respectively. Costs corresponding to accelerated growth rate and delayed maturation are lower survivorship and shorter reproduction period. Results suggest that SSD evolves because male and female body size respond differently to changes of life history traits and costs of two growth strategies. Present theoretical framework provides an insight for explaining evolution of SSD by integrating ontogenetic growth. We also emphasize the necessity of ontogenetic perspective in SSD studies.

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