Plastid phylogeography of Delphinium fissum subsp. sordidum and the series Fissa (Ranunculaceae) in the Iberian Peninsula: implications for conservation

We study the phylogeography of the series Fissa species in the Iberian Peninsula. This group constitutes a complex formed by three Iberian endemic and threatened taxa with restricted distribution ranges and relatively small population sizes. We amplify and sequence two plastid regions, trnS-trnG and psbA-trnH from 15 sampling locations (n = 45). A total of 15 haplotypes are detected. The median-joining phylogenetic network shows two main haplotype lineages: one western corresponding to the western taxon, D. fissum subsp. sordidum, and the other eastern corresponding to eastern taxa D. bolosii and D. mansanetianum. AMOVA analysis with 94.32% of the total variation and SAMOVA analysis with a Fct value of 0.943 support the presence of these well-defined lineages. We report high values of total gene diversity (h_T = 0.959). Haplotype diversity within populations is low (h_S = 0.311). On the contrary, differentiation among populations (G_ST = 0.675) and Fixation Index (F_ST = 0.989) are high. These values mean that gene flow among populations is limited. Estimation of divergence times shows that the split between D. fissum subsp. sordidum and the two other taxa (D. bolosii and D. mansanetianum) took place during the transition between Pliocene and Pleistocene (approximately 2.67 Ma). Negative Tajima’s D-values test (Tajima’s D = -0.108, P ≥ 0.1) and unimodal mismatch distribution suggest expansion range for D. fissum subsp. sordidum. We advocate to draw up recovery plans for series Fissa species in the Iberian Peninsula, especially for D. fissum subsp. sordidum.