2nd ASEAN Symposium and Workshop on 
Sea Turtle Biology and Conservation

SESSION 2: Nesting and Foraging Populations

ABSTRACTS

Inferring past and present population dynamic history of marine turtle populations in the Indo-Pacific using genetic data and implications for management.

Damien Broderick

Department of Zoology and Entomology & The Centre for Conservation Biology University of Queensland, Australia

Marine turtles are highly significant culturally and as a source of nutrition and income in local communities throughout the islands of the Indo-Pacific. Regrettably, breeding populations of these species have declined throughout much of the region, indicating that past levels of resource use were unsustainable. Effective management of these species is complicated by their extensive migrations and will require international cooperation, the framework for which is already in place. Genetic analysis can contribute to better understanding and management of the resource through identifying which sets of breeding aggregations represent discrete breeding populations. Given that unique genetic markers or combinations thereof characterise these populations, it may also be possible to identify which breeding populations are represented in foraging populations and harvests. Such an application requires that all contributing stocks have been identified.

This paper will present results of surveys of variation in mtDNA among breeding and foraging populations of green and hawksbill turtles in the region. Typically, each breeding population, often comprised of multiple rookeries, is genetically unique and thus represents an independent management unit. Analysis of foraging populations typically indicates contributions from multiple breeding populations. Within the immediate SE Asian region we recognise three green and two hawksbill stocks that are demographically independent and therefore should be regarded as separate management units. We also recognise several other stocks in the Indo-Pacific and the implications of these results will be discussed.

Demographic processes such as female philopatry, migration, and dynamics of rookery colonisation and extinction leave signals in the present day distribution of genetic variation. Understanding the effects of these processes can help in the interpretation of the complex phylogeographic patterns we see in Indo-Pacific marine turtles. Using the coalescent approach and simulation I tested the goodness of fit of several evolutionary scenarios against the observed data for marine turtles. In general, non-equilibrium models provided a better fit to the data than classic equilibrium models suggesting periodic disturbance events, such as sea level and temperature change, were important in shaping marine turtle phylogeography. Analysis of this data suggest that marine turtle phylogeographic patterns in the Indo-Pacific are best interpreted in terms of a balance between female philopatry, episodic dispersal and population size change events.