Floral Traits and Breeding Systems in Sincoraea (Bromeliaceae), an Endemic Genus of Brazilian Rupestrian Grasslands

Brazilian campos rupestres are a global center of plant endemism, but they are increasingly threatened by climate change and human activities. In this context, Sincoraea, an endemic genus of the Espinhaço Mountain Range, provides an important model for understanding how reproductive traits influence species persistence. This study investigated the floral biology, reproductive systems, nectar dynamics, and floral visitors' interactions of several Sincoraea species through fieldwork conducted from 2023 to 2025. Floral biology and pollination were analyzed in four species, while pollen and stigma traits were examined in eight species using light and scanning electron microscopy. The flowers had white tubular corollas, diurnal anthesis, and high pollen viability during anthesis. Nectar production peaked in the morning. All recorded pollinators were hummingbirds and all species were self-incompatible, except S. burle-marxii, which was partially self-compatible. The reproductive effectiveness index was 1.00 for all species, suggesting that natural pollination provided effective conspecific pollen transfer without evidence of pollen limitation. These findings highlight the strong dependence of Sincoraea on floral visitors and emphasize the importance of conserving plant-floral visitor networks in campos rupestres. These interactions are essential for maintaining genetic diversity and the long-term stability of ecosystems.