Meeting Abstract

40.4  Wednesday, Jan. 5  Microevolution of seasonal dimorphism in morphology and performance of a lizard IRSCHICK, Duncan J*; LANGERHANS, Brian; University of Massachusetts Amherst; North Carolina State University irschick@bio.umass.edu

Dimorphisms are common in the animal kingdom, especially between males and females of the same species, but these also exist among males or females of the same species. In general, such male “morphs” have arisen as a consequence of sexual selection favoring different alternative strategies for mating, and the differences are either plastic or fixed. A far less documented or understood phenomenon is what we term forced polymorphism, or seasonal dimorphism, in which different ages within a sex have different phenotypes that are generated through a process of strong within-generation selection. We provide evidence for this rare phenomenon in the green anole lizard (Anolis carolinensis, a common semi-arboreal lizard native to the Southeastern USA. We performed mark-recapture analyses from an initial cohort of green anole lizards across an entire year and found evidence that phenotypic and performance differences among age classes were likely driven by intense selection within a generation, resulting in a seasonal dimorphism that was clearly visible in the winter, but less so in the spring. Our data suggest that such polymorphisms may be far more prevalent than typically thought.