Allozyme diversity of two endemic Petrocoptis species: P. montsicciana and its close relative P. pardoi (Caryophyllaceae)

Starch gel electrophoresis was used to evaluate the allozyme diversity, population structure, and taxonomic relationships of two closely related taxa endemic to the Iberian Peninsula: Petrocoptis montsicciana O. Bolòs & Rivas Martínez, restricted to the pre-Pyrenean belt of Catalonia and Aragon, and Petrocoptis pardoi Pau, endemic to the Bergantes River basin (Autonomous Community of Valencia). Seven populations of the two species were sampled, and 16 interpretable loci were found. Considerable polymorphism, more than expected in endemic species, was detected in both taxa. The percentage of polymorphic loci (P) when the most common allele had a frequency of <0.95, the mean number of alleles per locus (A), and the expected panmictic heterozygosity (He) were slightly higher in P. montsicciana (P = 70.3, A = 2.2 and He = 0.239) than in P. pardoi (P = 56.3, A = 1.9 and He = 0.192). Strong divergence between populations was found in both species (GST = 0.376 in P. montsicciana and GST = 0.354 in P. pardoi) because of the geographic isolation of populations and limited seed and pollen dispersal. Most loci showed deviations from the Hardy–Weinberg equilibrium, probably as a consequence of genetic substructuring of populations. Low germination and renewal rates, and some anthropogenic activities such as road work, climbing, and massive collection are the main threats to these species.