Ontogeny, variation and evolution of inflorescence in tribe Fabeae (Fabaceae) with special reference to genera Lathyrus, Pisum and Vavilovia

• A pendulum inflorescence symmetry is typical for the genera Lathyrus, Pisum, and Vavilovia.
• More than half of flowers in many-flowered inflorescences abort after initiation.
• A single-flowered axillary raceme accompanies annual life form in studied group.
• Many-flowered axillary racemes are derived from single-flowered ones.

The present study reports the inflorescence ontogeny and morphology in tribe Fabeae (Fabaceae) addressing the evolutionary trends of selected inflorescence features in clade Lathyrus–Pisum–Vavilovia. In all three mentioned genera, the whole inflorescence in annual taxa comprises an open shoot bearing frondose leaves subtended by simple racemes. This shoot exhibits a pendulum symmetry which results from skewed position of leaves initiating at shoot apex. During floral initiation in a model species, i.e., Vicia cracca, numerous flowers are produced on these racemes but later most of them degrade and only a small portion (<4%) of previously initiated flowers result in production of mature fruits. This many-flowered state is derived from a single- or few-flowered one typical for the most basal representatives of this clade. The single-flowered state strongly correlates with annual life form and arises repeatedly during evolution of tribe Fabeae. The adaptive values of different inflorescence types are discussed.