Population viability at extreme sex-ratio skews produced by temperature-dependent sex determination.
For species with temperature-dependent sex determination (TSD) there is the fear that rising temperatures may lead to single-sex populations and population extinction. We show that for sea turtles, a major group exhibiting TSD, these concerns are currently unfounded but may become important under extreme climate warming scenarios. We show how highly female-biased sex ratios in developing eggs translate into much more balanced operational sex ratios so that adult male numbers in populations around the world are unlikely to be limiting. Rather than reducing population viability, female-biased offspring sex ratios may, to some extent, help population growth by increasing the number of breeding females and hence egg production. For rookeries across the world (n= 75 sites for seven species), we show that extreme female-biased hatchling sex ratios do not compromise population size and are the norm, with a tendency for populations to maximize the number of female hatchlings. Only at extremely high incubation temperature does high mortality within developing clutches threaten sea turtles. Our work shows how TSD itself is a robust strategy up to a point, but eventually high mortality and female-only hatchling production will cause extinction if incubation conditions warm considerably in the future.
Deakin University, Geelong, Australia, School of Life and Environmental Sciences, Centre for Integrative Ecology, Warrnambool, VIC 3280, Australia g.hays@deakin.edu.au.
Graeme C
0000-0002-3314-8189
GC
Hays
Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
Antonios D
AD
Mazaris
Deakin University, Geelong, Australia, School of Life and Environmental Sciences, Centre for Integrative Ecology, Warrnambool, VIC 3280, Australia.
Gail
G
Schofield
Department of Biosciences, Swansea University, Swansea SA2 8PP, UK.
Jacques-Olivier
JO
Laloë
D000818:Animals; D001947:Breeding; D005260:Female; D008297:Male; D012732:Sex Determination Analysis; D012744:Sex Ratio; D013696:Temperature; D014426:Turtles / Q000502:physiology*
endangered species; environmental sex determination; extinction risk; male limitation; sex-ratio bias