Intraspecific Variation in Phenology and Reproductive Success of Microlicia laniflora: A Narrow-Endemic Species, Naturally Isolated on Rocky Outcrops

Premise of research. Intraspecific differences in plant reproductive traits affect ecological interactions at the population level, leading to evolutionary shifts. Abiotic and biotic factors exert strong selective pressures on functional traits, such as phenology, affecting reproductive success and thereby plant fitness. Here we evaluated the occurrence of intraspecific variation in the reproductive ecology and reproductive success among three naturally isolated populations of Microlicia laniflora, a narrow-endemic shrub from Brazilian campo rupestre. We asked (i) do isolated populations of M. laniflora differ in their reproductive phenology, floral biology, pollination, and reproductive success and (ii) which abiotic and biotic factors are related to interpopulation differences in reproductive success? Methodology. We sampled three sites varying in altitude and local environment in a tropical mountain vegetation system, the campos rupestres of Serra do Cipó, and tested for interpopulation differences in reproductive phenology, floral biology, pollination interactions, and reproductive success. Pivotal results. Microlicia laniflora populations differed in their reproductive phenology, pollination (frequency of visits and pollinators), and reproductive success, mainly between the lowest-altitude site and the two higher-altitude sites. Flowering and fruiting phenology were strongly seasonal, driven primarily by temperature variation during the reproductive season, with earlier flowering at the higher-altitude sites. There, lower temperatures, larger floral displays, and a higher frequency of pollinator visits positively influenced reproductive success. Conclusions. Our results support the assumption that abiotic and biotic factors jointly act as selective pressures driving phenology and shaping plant reproductive ecology. Our findings evidence the central role played by interpopulation variability in flowering phenology and in pollinator attraction in the evolution of floral and reproductive traits of plant species that are spatially isolated in stressful and megadiverse environments.