CIE Seminar Series 2016 – Sex in dragons: a tale of unfolding complexity, bringing in the genetic work to inform the ecological side of the story

Arthur GeorgesSPEAKER: Professor Arthur Georges, Institute for Applied Ecology, University of Canberra, ACT

DATE: Friday, 29th July 2016
LOCATION: Geelong Campus at Waurn Ponds, Room KA4.207
TIME: 1:30pm
Seminar will also be video linked to the following campuses: Melbourne Campus at Burwood, Burwood Corporate Centre (BCC) and Warrnambool Campus, Room J2.22

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ABSTRACT: Although phenotype is governed by underlying genotype, the translation of the genetic blueprint to traits possessed by the individual is under varying degrees of environmental influence, leading to phenotypic variation in traits with a common genetic underpinning.

Sex of an individual, at least in vertebrates, was once thought to be strictly determined by the complement of chromosomes passed to the offspring from the parents. The prevailing view of a 1:1 correspondence between genotype and sexual phenotype (genetic sex determination or GSD) that is so prevalent in mammals and birds, fell away with the discovery of astonishing diversity in the mechanisms of sex determination of many lineages of reptile and fish.

Environmental sex determination is now well established in these groups, and temperature early in development is the primary factor involved (hence, temperature-dependent sex determination, or TSD). Indeed, sex determination in reptiles is seen as one of the most profound examples of developmental plasticity among vertebrates.

Furthermore, it falls in a special class of phenotypic plasticity, along with castes in bees and winged/winglessness in aphids – a polyphenism with two states, whereby intermediate forms are either not viable or with severely compromised fitness.

In this presentation, the focus will be on a special case of sex determination where genotype and environment interact to determine sex, and discuss the mechanisms by which temperature may bring influence.

The dragon lizard, Pogona vitticeps, has well defined sex chromosomes – a ZZ/ZW system as in birds – yet temperature can over-ride the genetic signal to reverse the ZZ male trajectory to a female phenotype, both in the laboratory and in the wild.

This is one example where developmental plasticity can drive rapid evolutionary responses to changing climate, responses that challenge our understanding of the evolution of temperature-dependent sex determination.

BIO: Professor Arthur Georges is an ecologist and herpetologist whose research interests lie in the evolution, ecology and systematics of Australian reptiles. A fundamental interest in these fascinating animals takes him into the field and the laboratory to learn more of their biology and to apply what he has learned in solving contemporary challenges for their conservation.

Arthur recently led the consortium to generate an annotated genome sequence for the Australian dragon lizard, Pogona vitticeps, which he and his team are using to probe the intricacies of sex determination in reptiles.

Appointments with guest speaker may be made via Beata Ujvari.