Traits and pollination systems of brush-type flowers in the Capparaceae: A comprehensive review addressing the Eltonian shortfall

Abstract The flowers of members of the Capparaceae are characterized by an open morphology with numerous stamens, suggesting generalist pollination systems. Despite the conservative nature of this floral form within the family, there is evidence of significant variation in other traits, as indicated by sporadic records of different pollination systems. The research on the pollination biology of the Capparaceae seems to be sparse and fragmented, revealing an Eltonian shortfall in relation to plant–animal interactions in this family. Our objectives were: (1) to compile information from the literature on floral traits and pollination systems in the Capparaceae; (2) to summarize current knowledge about reproductive systems in the Capparaceae; (3) to test the existence of a latitudinal gradient in functional and ecological specialization within the family; and (4) to identify priority areas and species for further studies on pollination. We found considerable variation in floral traits, including colour, size and the number of stamens. Our results show a high degree of functional specialization, with the largest species being pollinated mainly by bees. We observed differences along a latitudinal gradient: Whereas the richness of pollinators reaches the peak near the equator, specialized groups, such as bats and moths, are restricted to tropical zones, making extratropical species more dependent on widespread pollination by bees. Variations in reproductive systems, including changes between self-incompatibility and self-compatibility, suggest a high degree of reproductive plasticity in response to environmental pressures and the scarcity of pollinators. We emphasize the need for further research on pollination ecology in Africa and South America, where many species of the Capparaceae are at risk of extinction.