CONICET | Buscador de Institutos y Recursos Humanos

In plants, narrow geographic distributions are generally associated with low colonization and persistenceabilities, therefore narrowly distributed plants are expected to have lower plant recruitment success thanwidespread species. Determining the association between recruitment success and range size requiresthe comparison of the success in multiple life-history stages among narrowly distributed and widespreadcongeners sharing the same habitat, an integrated approach rarely considered. We compared transitionprobabilities from ovule to reproductive adult between the narrowly distributed annual vine Ipomoearubriflora ODonnell (Convolvulaceae) and the widespread Ipomoea purpurea (L.) Roth at sites in Chacowoodland where they co-occur. I. rubriflora had marginally lower ovule fertilization success, a lowerprobability of seed maturation and lower seedling establishment than I. purpurea. The lowest transitionprobability for both species was seedling emergence. Seedling establishment in I. rubriflorawas similar toseedling emergence. Plant recruitment success in I. rubriflora was an order of magnitude lower than thatof I. purpurea. Indeed, I. rubriflora had lower total seed production per plant and smaller seed mass. Ourresults suggest that understanding processes determining regeneration (i.e., seedling emergence andestablishment) may be of high importance for understanding narrow distributions in annual plants. Theresults also suggest that the narrowly distributed species is not only at a numerical disadvantage forcolonizing new sitesdi.e., lower total seed production per plantdbut it also has a lower per-seedprobability of establishing and thus to persist. However, as lower establishment success in this speciesseemed to be associated with the lower ability to survive adverse conditions of seedlings from smallerseededspecies, a narrower regeneration niche might also explain its narrow distribution.

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