Ecology and Evolution Seminar Series - Anna Carter

Date: 2 June 2016 Time: 12.00 pm

**Dr Anna Carter presents Modelling the incubation environment informs predictions of habitat suitability for tuatara**

Species distribution models are used increasingly to examine habitat suitability and predict range shifts within the context of modern climate change. However, climate envelopes and other commonly used correlative methods are of limited use if the primary conservation concern is not sufficient availability of habitat. In species with temperature-dependent sex determination (TSD), environmental variation with minimal detectable effect on the distribution or fitness of adults may dramatically skew offspring sex ratios and decrease population viability. An accurate definition of habitat suitability for these species must include the thermal suitability of sites both for successful completion of embryonic development and maintenance of balanced sex ratios. I used a spatially explicit, mechanistic microclimate model coupled with a biophysical model of embryonic development to locate thermally suitable nesting sites and predict offspring sex ratios for tuatara in two distinct island habitats under current and projected future climate scenarios. If climate change observed over the next 100 years more closely matches the maximum, rather than the minimum, projected magnitude of warming, hatchling sex ratios on both islands are likely to become heavily male-biased. Changes in either nesting phenology or nest depth are unlikely to compensate for the effects of climate change on sex ratios. In addition, the now-tight relationship between egg-laying dates and sex ratios may become de-coupled under maximum warming, creating an ecological trap. Spatially explicit data that quantify the thermal suitability of sites for incubation and sex determination should be considered critical to conservation of tuatara and other species with TSD.

For more information, please contact Dr Heiko Wittmer on heiko.wittmer@vuw.ac.nz