PCR amplifications were carried out in a T-Personal Thermal Cycler (Biometra), using the annealing temperature previously reported (Poteaux 1995; Hansen & Loeschcke 1996; Miller & Kapuscinski 1996, 1997; Presa & Guyomard 1996) and the amplification program: 94 ° C for 3 min; 30 cycles (94 ° C for − 30 s; T m for 40 s; 72 ° C for − 30 s) with a final extension at 72 ° C for 10 min. RFLP analysis was carried out on two mitochondrial DNA (mtDNA) fragments corresponding to coding regions ND-1 (NADH dehydrogenase 1) and ND-5/6 (NADH dehydrogenase 5 and 6) (Hansen & Loeschcke 1996); amplicons were digested without further purification with proper digestion enzymes (ND-1 with Ava II, Hin fI, Alu I, Hae III and Hpa II; ND-5/6 with Ava II, Hinf I, Hae III, Taq I and Hpa II). Micro