Project

Functional Consequences of Sea Turtle Hybridization

Sea turtles are keystone species, supporting the ecosystem services of their habitat, and as such they have been the subject of many conservation efforts. Sea turtles keep their ecosystems connected with their migration patterns and in balance with their foraging behaviour. They increase habitat productivity leading to, for instance, sediment stabilization, increased fish biodiversity and this way they indirectly facilitate fisheries. In the last 130 years, interspecific hybridization in sea turtles has been observed, but recently it has been reported more frequently, raising questions about its effects. 

In this project, we study the hybridization within the North-Atlantic sea turtle population and how this hybridization might affect their functional roles. This project will contain fieldwork in the Caribbean focusing on three sea turtle species, green turtle (Chelonia mydas), hawksbill turtle (Eretmochelys imbricata) and loggerhead turtle (Caretta caretta) and (data) analyses of the collected samples.  

Hybridization is the process where mating occurs between individuals from different species resulting in ‘hybrid’ offspring. When fertile, these hybrid offspring may be the first of several hybrid generations. Historically, hybridization likely played an important role in species evolution. From a conservation standpoint, it can genetically rescue small populations, increase diversity and result in useful adaptations. However, the traditional concern is that it may reduce diversity by, for instance, the parental species being replaced by the hybrid or dysfunctional hybrids reducing the population growth rate even more. As number of species in danger of extinction on the IUCN Red List increases more and more, it is of great importance that we understand the consequences of hybridization on these endangered species.   

One such threatened species group is the sea turtle. Consideration of the potential conservation value of hybridization will have important consequences for its conservation management. Declining populations, combined with spatial and temporal overlap of the nesting activities are suggested to be key drivers of these hybridizations. When hybrids are viable, fertile and can reproduce with other hybrids or one of their parental species, phenotypic differentiation between the hybrids and the parental species might result in novel evolutionary potential, allowing the species to adapt to new and changing environments and conditions. However, hybridization may also drive a change in the functional roles sea turtle species fulfil in their environment.  

Green turtle 4.JPG
Hatchling water.JPG
Netting survey measurements 1.JPG

This project will determine whether a further increase in the percentage of sea turtle hybrids is to be expected and how hybridization may alter the keystone roles of sea turtles. We will use a complementary combination of nest monitoring, genetic analysis, stable isotope analysis and behavioural assays. This multi-disciplinary approach will allow us to conduct large-scale genetic screening to identify hybrids and determine the hybridization rate in the North-Atlantic population. We will evaluate the effects of hybridization on the diet and mobility of the sea turtles and explore evidence for past hybridization events and potential genetic incompatibilities. Consequently, we will make predictions about the viability of sea turtle hybrids, considering the selection occurring on hybrid alleles.  

Our project aims to generate important insights into the role of hybridization in the ecology and conservation of endangered species, contribute to evidence-based decision-making concerning the management of sea turtles, and provide essential tools and knowledge for future research and management. 

This project is a collaboration between the Behavioural Ecology Group (Liesa Celie MSc., Dr Lysanne Snijders and Prof Dr Marc Naguib), Animal Breeding and Genomics (Dr Mirte Bosse) and Aquatic Ecology and Water Quality Management (Dr Marjolijn Christianen). Dr Sibelle Torres Vilaça of the Instituto Tecnologico Vale in Belem, Brazil, is an external advisor. In addition, we work together with Sea Turtle Conservation Bonaire, Sea Turtle Conservation Curaçao and Prof Kate Mansfield of the Marine Turtle Research Group (University of Central Florida).

Pictures credits: Celie, Liesa