MEPS 450:207-218 (2012)  -  DOI: https://doi.org/10.3354/meps09548

ABSTRACT: Libya is one of the most important loggerhead turtle Caretta caretta nesting grounds in the Mediterranean Sea, but data on its genetic diversity and demographic connection to adjacent Mediterranean nesting sites are scarce. Here we investigated mitochondrial diversity in adult females from 2 nesting locations along the Libyan coasts, Misurata and Sirte, by analysing both the commonly used 380 bp mtDNA fragment and a longer 800 bp fragment that completely encompass the shorter region. No genetic differentiation was detected between the Libyan sites using the shorter sequences (Φ_st = −0.005, p = 0.54, Exact p = 0.67). However, significant population structuring was found among sites in Libya and other Mediterranean nesting areas (Φ_st = 0.242, p < 0.01). The analysis of the longer sequence revealed more haplotypes than the shorter fragment and uncovered genetic differentiation between Misurata and Sirte (Φ_st = 0.13, p = 0.02, Exact p = 0.01), suggesting fine-scale homing behaviour of loggerhead nesting females along the Libyan coast. Because only a few Atlantic and Mediterranean loggerhead turtle rookeries have been genetically surveyed using the longer sequence, we used information from the short mtDNA fragment to investigate dispersal patterns of Libyan loggerhead turtles. Mixed stock analysis estimates suggested that during the oceanic developmental phase, Libyan juveniles remain preferentially in the eastern Mediterranean while after the transition to the neritic phase, they favour the south Tunisian coastal areas while avoiding the north-central Adriatic Sea. This study highlights the unique nature of the Libyan nesting population, making it an important management unit. The protection of this nesting stock is fundamental to managing the Mediterranean loggerhead turtle assemblage.

KEY WORDS: Loggerhead turtle · mtDNA · Population structure · Conservation · Dispersal pattern · Homing