Investigating the link between niche breadth, dispersal ability and vulnerability to river damming in Australian freshwater turtles.

Erica V. Todd, School of Marine and Tropical Biology, James Cook University

Erica with turtles ready for release
Photo © Erica Todd

Human-induced changes to river systems, such as river damming, diversion and water extraction for irrigation, severely impact sensitive freshwater organisms through processes such as habitat loss and fragmentation. My PhD research focuses on a neglected but important group: freshwater turtles. Australia supports a distinctive and ecologically diverse turtle fauna. However, these key components of freshwater ecosystems are very poorly researched. In particular, we know very little about the dispersal patterns and population genetics of most Australian turtle species.

Dispersal among small local populations is important for species survival. It connects populations across the landscape, preventing inbreeding and allowing recovery from local extinctions. River impoundments are likely to create dispersal barriers for highly aquatic turtles, although the extent of this is currently unknown. Without baseline data on natural levels of population connectivity and genetic structure, likely long-term impacts of human-reduced dispersal on the persistence of turtle populations cannot be accurately assessed. Some river turtles may also be more vulnerable than others due to their specific habitat requirements and assumed reduced dispersal capacity.

Elseya albagula
Photo © Erica Todd

My research aims to establish the important link between habitat specialisation, dispersal ability and population connectivity, in order to assess likely long-term impacts of river regulation on ecologically different river turtles. To do this, I am using genetic techniques to compare patterns of genetic diversity and population connectivity (gene flow) between two very different species of turtle. Krefft’s turtle (Emydura macquarii krefftii) has broad habitat requirements and is common and widespread in Queensland. By contrast, the white-throated snapping turtle (Elseya albagula) is a threatened ecological specialist unique to the Fitzroy, Burnett and Mary River drainages of central and south east Queensland. As the project progresses, I also hope to include other turtle species, such as the little-known Irwin’s turtle (Elseya irwini) identified from only a few sites within the Burdekin River system of North Queensland.

One of the field sites
Photo © Erica Todd

The most enjoyable part of my research is field work. I have already travelled to many interesting sites throughout Queensland to catch turtles, by boat or snorkel or using nets and traps. Turtles are measured and tagged, and a small sample of skin is taken from each animal to provide DNA for genetic analyses. To date, I have collected genetic samples from over 150 turtles from 5 separate species. Other Australian turtle researchers have kindly supplied many more samples for my project.

This research will be the first detailed comparative genetic study of ecologically important river turtles in Queensland, and the first of its kind to assess long-term genetic implications of dams and weirs for this group. It will have important conservation outcomes, providing invaluable information for species management programs and for prioritising conservation actions. By addressing a prominent research gap in Australian freshwater turtle biology, I hope that a better understanding of the vulnerability of different freshwater turtle species to habitat fragmentation will assist conservation planners to design more effective management strategies.