Evolution of Shell Kinesis in Turtles Developmental Origins of a Convergent Phenotype During and After Embryogenesis

Meeting Abstract

120.3  Tuesday, Jan. 7 11:00  Evolution of Shell Kinesis in Turtles: Developmental Origins of a Convergent Phenotype During and After Embryogenesis CORDERO, G.A.; Iowa State University gcordero@iastate.edu

Turtles have undergone several adaptive radiations during their 220 million-year history. They have successfully invaded freshwater, marine, and terrestrial ecosystems worldwide. Even so, the turtle body plan consisting of dorsal (carapace) and ventral (plastron) shell components has undergone few changes, suggesting that it is developmentally constrained. Not surprisingly, the most complex modification of the basic turtle body plan, shell kinesis, has evolved multiple times in several unrelated lineages. Shell kinesis enables the absolute concealment of all body parts in some species. By enhancing anti-predator defense, this complex trait likely promoted invasion of terrestrial environments. Is the convergent of evolution of shell kinesis due to change in the same developmental processes in unrelated species in similar environments? I conducted a series of embryological, histological, phylogenetic, and morphometric analyses to answer this question. My results implicate extensive bone remodelling of the plastron during post-natal ontogeny as the shared developmental process in species with shell kinesis. However, changes in the embryonic development of anatomical components associated with this trait likely vary according to phylogenetic distance. My findings suggest that the turtle’s unusual body plan is not an “evolutionary straitjacket”. Lastly, the development of complex and convergent phenotypes is not limited to embryonic life stages.

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