Floral morphometric analysis of Prosopis affinis Spreng. (Fabaceae) suggests flexibility of the reproductive system in isolated populations within the Brazilian Pampa

Morphological characteristics of inflorescences and flowers of Prosopis affinis growing in the Pampa biome were measured aiming to indirectly infer the species reproductive system. The pollen/ovule ratio and the outcrossing index suggest flexibility of the reproductive system, with values intermediary between facultative autogamy and xenogamy. No clear reproductive specialization related to flower position in the inflorescence was observed, although basal flowers in the inflorescence presented reduction of the androecium. Further analyzes comparing isolated and larger continuous populations, as well as estimations of the real outcrossing rate of P. affinis through genetic studies and controlled experiments to evaluate auto-compatibility are recommended in order to generate more information about this issue.