Genome size and plastid trnK-matK markers give new insights into the evolutionary history of the genus <i>Lavandula</i> L.

The genus <i>Lavandula</i> L. consists of 39 species distributed from the North Atlantic Islands, across the Mediterranean Basin to India. We analysed 36 taxa of the genus <i>Lavandula</i> representing two of the three subgenera and six of the eight sections according to the most recent classification (Upson &amp; Andrews 2004). We achieved a phylogenetic reconstruction from partial sequences from plastid trnK and matK genes; the genome size was estimated by flow cytometer measurements. The primary aim was to track phylogenetic patterns through the maternal inherited marker at the sectional level and identify possible genome duplications. The cpDNA tree shows the phylogenetic relationships between subgenus, sections and also elucidates for the first time the relationships between the endemic species of Macaronesia, Morocco and Arabia. The ancestral split between the two subgenera could be explained by dispersal followed by an early vicariance event. The <i>C</i>-value shows genome up-sizing within several phylogenetic clades and geographical areas. An ancestral genome-up sizing is characterized at the node of section <i>Dentatae</i> and <i>Lavandula</i>. The cpDNA tree suggests that the taxa <i>L. angustifolia</i> subsp. <i>pyrenaica</i> (DC.) Guinea and <i>L. stoechas</i> subsp. <i>luiseiri</i> are best treated as a distinct species.