Systematics, biogeography, and character evolution of the legume tribe Fabeae with special focus on the middle-Atlantic island lineages

• Main Authors: Schaefer Hanno, Hechenleitner Paulina, Santos-Guerra Arnoldo, de Sequeira Miguel Menezes, Pennington R Toby, Kenicer Gregory, Carine Mark A
• Format: Article
• Language: English
• Published: BMC 2012-12-01
• Series: BMC Evolutionary Biology
• Subjects: <it>Lathyrus</it>; Legumes; Lentil; Long-distance dispersal; Macaronesia; Pea; <it>Pisum</it>; <it>Vicia</it>
• Online Access: http://www.biomedcentral.com/1471-2148/12/250

<p>Abstract</p> <p>Background</p> <p>Tribe Fabeae comprises about 380 legume species, including some of the most ancient and important crops like lentil, pea, and broad bean. Breeding efforts in legume crops rely on a detailed knowledge of closest wild relatives and geographic origin. Relationships within the tribe, however, are incompletely known and previous molecular results conflicted with the traditional morphology-based classification. Here we analyse the systematics, biogeography, and character evolution in the tribe based on plastid and nuclear DNA sequences.</p> <p>Results</p> <p>Phylogenetic analyses including c. 70% of the species in the tribe show that the genera <it>Vicia</it> and <it>Lathyrus</it> in their current circumscription are not monophyletic: <it>Pisum</it> and <it>Vavilovia</it> are nested in <it>Lathyrus</it>, the genus <it>Lens</it> is nested in <it>Vicia</it>. A small, well-supported clade including <it>Vicia hirsuta</it>, <it>V. sylvatica</it>, and some Mediterranean endemics, is the sister group to all remaining species in the tribe. Fabeae originated in the East Mediterranean region in the Miocene (23–16 million years ago (Ma)) and spread at least 39 times into Eurasia, seven times to the Americas, twice to tropical Africa and four times to Macaronesia. Broad bean (<it>V. faba</it>) and its sister <it>V. paucijuga</it> originated in Asia and might be sister to <it>V. oroboides</it>. Lentil (<it>Lens culinaris</it> ssp. <it>culinaris</it>) is of Mediterranean origin and together with eight very close relatives forms a clade that is nested in the core <it>Vicia</it>, where it evolved c. 14 Ma. The <it>Pisum</it> clade is nested in <it>Lathyrus</it> in a grade with the Mediterranean <it>L. gloeosperma</it>, <it>L. neurolobus</it>, and <it>L. nissolia</it>. The extinct Azorean endemic <it>V. dennesiana</it> belongs in section Cracca and is nested among Mediterranean species. According to our ancestral character state reconstruction results, ancestors of Fabeae had a basic chromosome number of 2n=14, an annual life form, and evenly hairy, dorsiventrally compressed styles.</p> <p>Conclusions</p> <p>Fabeae evolved in the Eastern Mediterranean in the middle Miocene and spread from there across Eurasia, into Tropical Africa, and at least seven times to the Americas. The middle-Atlantic islands were colonized four times but apparently did not serve as stepping-stones for Atlantic crossings. Long-distance dispersal events are relatively common in Fabeae (seven per ten million years). Current generic and infrageneric circumscriptions in Fabeae do not reflect monophyletic groups and should be revised. Suggestions for generic level delimitation are offered.</p>