Plant life on serpentine soils has been a topic of research for decades, but the evolutionary dynamics behind the origin of specialized lineages endemic to such a stressful habitat are still incompletely understood. This issue was addressed using the genus Onosma (Boraginaceae) as model system and a molecular phylogenetic approach. Nuclear DNA ITS sequences were generated for a broad sample of taxa including seven obligate endemics allopatrically distributed on the ophiolitic "islands" in the Balkans, along with accessions of serpentine-tolerant and non-tolerant species. Bayesian inference of phylogeny showed that Europaean obligate endemics belong to at least five clades without direct relationships to each other. Lack of a common ancestor and of correlation between geographic and genetic distances suggested polyphyletic evolution of endemic species group. Preference for non-serpentine habitats is suggested as the ancestral condition but key preadaptive traits such as drought tolerance and ability to cope with high Mg soil concentrations may have fostered multiple events of colonization of ultramafics. Based on a dated tree calibrated with the known age of the Macaronesian clade of the sister genus Echium, such events can be placed towards the limit between the Pliocene and Pleistocene (ca. 2.5 mya).
Origins and relationships of serpentine endemics in Mediterranean Lithospermeae (Boraginaceae): insights from Onosma and other Balkan taxa / Selvi F.; Cecchi L.. - STAMPA. - Biodiversity Hotspots in the Mediterraneran Area: species, communities and landscape level:(2009), pp. 99-99. (Intervento presentato al convegno Biodiversity Hotspots in the Mediterraneran Area: species, communities and landscape level tenutosi a Cagliari nel 22-24 Giugno 2009).
Origins and relationships of serpentine endemics in Mediterranean Lithospermeae (Boraginaceae): insights from Onosma and other Balkan taxa
SELVI, FEDERICO
;CECCHI, LORENZO
2009
Abstract
Plant life on serpentine soils has been a topic of research for decades, but the evolutionary dynamics behind the origin of specialized lineages endemic to such a stressful habitat are still incompletely understood. This issue was addressed using the genus Onosma (Boraginaceae) as model system and a molecular phylogenetic approach. Nuclear DNA ITS sequences were generated for a broad sample of taxa including seven obligate endemics allopatrically distributed on the ophiolitic "islands" in the Balkans, along with accessions of serpentine-tolerant and non-tolerant species. Bayesian inference of phylogeny showed that Europaean obligate endemics belong to at least five clades without direct relationships to each other. Lack of a common ancestor and of correlation between geographic and genetic distances suggested polyphyletic evolution of endemic species group. Preference for non-serpentine habitats is suggested as the ancestral condition but key preadaptive traits such as drought tolerance and ability to cope with high Mg soil concentrations may have fostered multiple events of colonization of ultramafics. Based on a dated tree calibrated with the known age of the Macaronesian clade of the sister genus Echium, such events can be placed towards the limit between the Pliocene and Pleistocene (ca. 2.5 mya).I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.