Variation in Telomere Dynamics with Life History Strategy in Polymorphic Reptiles, Ctenophorus pictus and Thamnophis sirtalis parietalis

Abstract

Telomeres, short tandem repeats of TTAGGG at the ends of chromosomes, are dynamic structures which may be affected by the life history strategy of an organism. Telomeres shorten during cellular replication and may also be damaged by reactive oxygen species (ROS). Conversely, they can be lengthened by telomerase activity and ROS may be countered by antioxidant production. Telomere length may affect the repair capacity of tissues and is implicated in the ageing process. Thus telomere dynamics are highly important, vary among species and may vary within species, depending upon life history strategy. Research comparing life histories and telomere dynamics has mostly focussed on inter-species comparisons which may be confounded by genetic variation. By studying the telomeres of polymorphic species with unusual life history strategies we minimise genetic variation and may be able to identify trends that would otherwise be obscured. I investigated the telomere dynamics of two reptile species with unusual life history strategies, painted dragons, Ctenophorus pictus, where males are colour polymorphic, and red-sided garter snakes, Thamnophis sirtalis parietalis, which have strong sexual dimorphism. Painted dragons live for approximately one year in the wild and males vary in their head colour and presence or absence of a yellow gular bib. The morphs vary in life history strategy and behaviours. Red-sided garter snakes hibernate for eight months of the year in communal dens and mate upon emergence in large aggregations of potentially thousands of snakes. The aggregations are heavily male biased, and males highly prioritise reproduction, attempting to court females for up to three weeks while aphagic. By contrast, females invest minimally in mating and prioritise foraging and cellular maintenance. The contrasting behaviours and life history strategies of the individuals within these two species makes them ideal models for intra-species comparisons of telomere dynamics.