Format: ORAL

Benjamin M. Torke1,Lusa M. de P. A. Bezerra2, Domingos Cardoso3, Kuo-fang Chung4, Ana-Paula Fortuna Perez5, Mohammad Vatanparast6

1 New York Botanical Garden, Institute of Systematic Botany, Bronx, NY, USA 2 Universidade Estadual Paulista, Botucatu, São Paulo, Brazil 3 Coordenação Flora e Funga do Brasil, Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil 4 Museum Biodiversity Research Center, Academia Sinica, Taipei, Taiwan 5 Universidade Estadual Paulista, Botucatu, São Paulo, Brazil 6 Jodrell Laboratory, Royal Botanic Gardens, Kew, UK

Seeds that deceptively mimic nutritious fruits or arillate seeds but provide no nutritive rewards to dispersers have evolved repeatedly in Fabaceae and are one of the most striking examples of phenotypic convergence in the family, yet their evolutionary origins have been little studied. These seeds are associated with a suite of traits, including bright coloration, extreme hardness and impermeability, strong physical dormancy, suppressed abscission, and accumulation of toxic secondary metabolites, that define a parasitic dispersal syndrome targeting naive frugivorous birds. To attract sufficient numbers of dispersers, this strategy requires that seeds remain attached to dehisced pods in the plant canopy for long periods of time, increasing risk of deterioration and exposure to predators. We review the biology of mimetic seeds in the context of the increasingly well resolved phylogeny of legumes and present preliminary data relevant to hypotheses about their origins. We conclude that mimetic seeds have arisen convergently at least 16 times in the family, but only in subfamilies Caesalpinioideae and Faboideae. In most cases the evolutionary transition to parasitism is associated with an abrupt shift to bird dispersal from some other dispersal mode involving one or more non-avian dispersal agents; apparent transitions from mutualistic to parasitic bird dispersal are few. Evolutionary origins of several of the characteristic traits of mimetic seeds—hardness, location in persistent fruits, and toxic secondary metabolites—predate transitions to bird dispersal and mimicry; these traits were likely exapted for their current functions in mimetic seeds. Two other traits—bright coloration and suppressed abscission—are much more closely associated with transitions to mimicry and bird dispersal, and thus likely constitute original adaptations for these purposes. Planned comparative studies on the genetic control of this latter class of traits may be illuminating with respect to the apparent propensity for lineages of Fabaceae to evolve mimetic seeds.