Conservation implications of complex population structure: lessons from the loggerhead turtle (Caretta caretta)

Area of Science:

• Marine Biology
• Conservation Genetics
• Population Dynamics

Background:

• Complex population structures in migratory species arise from sex-biased gene flow and overlapping populations.
• Loggerhead sea turtles (Caretta caretta) display traits relevant to understanding population structure and informing wildlife management.

Purpose of the Study:

• To investigate the population structure of loggerhead sea turtles across different life history stages.
• To differentiate between maternally inherited mitochondrial DNA (mtDNA) and biparentally inherited microsatellite DNA patterns.
• To inform effective wildlife management strategies for loggerhead turtles.

Main Methods:

• Analysis of maternally inherited mtDNA in pelagic post-hatchlings, subadults, and nesting females.
• Survey of biparentally inherited microsatellite DNA in nesting colonies.
• Statistical analysis of population structure using phi(ST), R(ST), and F(ST) metrics.

Main Results:

• Mitochondrial DNA reveals increasing population structure with life stage: no structure in hatchlings, low structure in subadults, and strong structure in nesting colonies.
• Microsatellite DNA shows no significant population structure among nesting colonies, indicating male-mediated gene flow.
• mtDNA haplotype diversity varies significantly, while microsatellite diversity is uniform across populations.

Conclusions:

• Loggerhead females exhibit natal homing, while males contribute to gene flow between nesting colonies.
• The contrasting genetic patterns necessitate distinct management approaches for different life stages of loggerhead turtles.
• Comprehensive surveys across multiple life stages are crucial for defining management units in migratory marine species.