Phylogeographic structure in the coastal species Senecio rodriguezii (Asteraceae), a narrow endemic Mediterranean plant.

Abstract

[eng] The study focused on the endemic plant Senecio rodriguezii, found on the Eastern Balearic Islands (Majorca and Minorca). The goals were to analyze chloroplast DNA variation, identify any phylogeographical structure, and interpret the findings in the context of the islands' palaeogeography. Researchers sampled 134 individuals from 28 populations, sequencing the T–trnL spacer of the chloroplast genome. Genetic diversity and geographical structuring were assessed using statistical methods, including AMOVA, SAMOVA, and a Mantel test for isolation by distance. The results revealed seven haplotypes, with most being geographically restricted. Two were shared between islands, while the rest were unique to either Majorca or Minorca. High genetic diversity and significant geographical structuring were observed, with 84.6% of variation attributed to differences among populations and noticeable differentiation between the islands. The findings highlight the Balearic Islands as a genetic diversity reservoir for both widespread and endemic species. The genetic structure of <em>S. rodriguezii reflects a history of expansion and contraction influenced by habitat changes and sea-level fluctuations during the Quaternary, leading to a highly structured genetic makeup with limited haplotype sharing between islands.