Geographic Variation in Sex Determination Patterns in the River Turtle Podocnemis lewyana: Implications for Global Warming

• Published in: Journal of herpetology 2016-06, Vol.50 (2), p.256-262
• Main Authors: Gallego-García, Natalia, Páez, Vivian P
• Format: Article
• Language: English
• Subjects: Animal nesting; Climate change; CONSERVATION; Gender bias; Genetic variation; Heritability; Population dynamics; Population genetics; Regular; Sex determination; Sex ratio; Turtles
• ISSN: 0022-1511; 1937-2418
• DOI: 10.1670/14-139

Species with temperature-dependent sex determination (TSD) are more vulnerable to climate change than species with genetically based sex determination because an increase in average environmental temperature could lead to biased offspring sex ratios. In TSD species, the relationship between sex ratio and constant incubation temperature is characterized by two parameters: the pivotal temperature (Tpiv) and the transitional range of temperature (TRT) that produces both sexes. Species with variation in either of these parameters should have more potential to adapt to new climatic conditions, therefore putting them at lower risk to global warming. In this study, we incubated eggs of the turtle Podocnemis lewyana (Testudines: Podocnemididae) from two geographically isolated populations (Magdalena and Sinú rivers) under controlled microclimatic conditions to corroborate the TSD pattern previously reported for this species and to estimate the degree of inter- and intrapopulation variation in Tpiv and TRT. We used these estimates, together with information found in the literature on other life history traits of P. lewyana, to evaluate its adaptive potential or vulnerability to climate change. We found interpopulation variation in TRT and intrapopulation variation in Tpiv. This latter parameter exhibited a high broad-sense heritability, demonstrating this species' potential to adapt to climate change; however, when considering the narrow TRT found in this study, the species' equatorial distribution and related adaptations to relatively more stable climates, its fragmented populations and low vagility that prevent gene flow, and its low genetic variability, we concluded that the ability of P. lewyana to adapt to climate change is limited. Las especies con determinación sexual dependiente de la temperatura (DST) son más vulnerables al cambio climático que aquellas con determinación sexual genética, ya que un aumento en la temperatura ambiental puede llevar a sesgos en las proporciones sexuales de la progenie. En especies con DST la relación entre las proporciones sexuales y la temperatura constante de incubación, está caracterizada por dos parámetros: la temperatura pivotal (Tpiv) y el rango de transición de temperaturas (RTT) en el que se producen ambos sexos. Las especies con más variación en alguno de estos parámetros tienen más potencial para adaptarse a nuevas condiciones climáticas, y en consecuencia ser menos vulnerables al calentamiento global. En este estudi