3.5. Population structure
Given the results from genetic and morphological species delimitations (see above), it is highly likely that the two groups that were identified in nuclear, mitochondrial and morphological characters correspond to two reproductively isolated species inside nominalCnemidocarpa verrucosa sensu lato, which in the following will be called C. verrucosa sp. A and C. verrucosa sp. B. Hence, the following analyses were carried out separately for each delimited species of C. verrucosa sensu stricto.
The overall fixation index for C. verrucosa sp. A (COI: FST =0.072; p < 0.05; 18S: FST= 0.154; p < 0.001) computed by AMOVA, pointed toward a high diversity and a strong structure among all Antarctic Peninsula sites (results from pairwise FST genetic distance analysis for COI and 18S are shown in Table 2, Supplemental information).
On the other side, C. verrucosa sp. B showed no genetic structure among populations in COI-sequences pairwise FST genetic distance analysis (Supplemental information, Table 3), and sequences from 18S nuclear gene presented all the same haplotype. AMOVA overall Fixation index for COI (COI: FST = 0.003; p > 0.05) also showed no genetic structure.