Floral Integration and Phenotypic Selection on Floral Traits of <i>Ipomoea cavalcantei</i> (Convolvulaceae), a Rare, Endemic, and Endangered Species to the Amazon Ironstone Outcrops

Maintaining evolutionary potential is essential for species persistence, particularly for rare and endemic taxa that are more susceptible to habitat changes. We evaluated floral integration and phenotypic selection on the floral traits of <i>Ipomoea cavalcantei</i>, a species endemic to the ironstone outcrops (<i>cangas</i>) of the Eastern Amazon and primarily pollinated by hummingbirds. Using 90 individuals from a natural population in the Floresta Nacional de Carajás, we conducted six pollination experiments to assess the mating system. We estimated individual fitness through fruit set and characterized floral phenotype by measuring ten traits under a stereomicroscope. We analyzed the mating system using a generalized linear model, assessed floral integration through matrix correlations, and evaluated phenotypic selection via simple and multiple regressions. <i>Ipomoea cavalcantei</i> was found to be self-incompatible, with higher fruit set in pollen-supplemented flowers. The association between matrices (modularity) was significant for both the morphological and developmental criteria, and style length exhibited five significant correlations out of the nine. Contrary to expectations for hummingbird-pollinated flowers, corolla-associated traits were not under significant selection. Only the ovary width showed a significant selection differential and gradient in the linear analyses, likely due to selective pressure from pre-dispersal seed predators. This indicates positive directional selection: individuals with flowers bearing wider ovaries than the population mean tend to have higher relative fitness. Our findings highlight the role of pollinators in shaping floral integration in <i>I. cavalcantei</i> and their importance in ensuring maximum seed production, thereby supporting offspring formation even under seed predation.