Increasing chronic anthropogenic disturbances and aridity differentially impact pollen traits and female reproductive success of Tacinga palmadora (Cactaceae) in a Caatinga dry forest

Ecological interactions in tropical ecosystems are being modified by chronic anthropogenic disturbances (CAD) and climate change. Pollination is a key mutualistic interaction that can be affected by disturbance and climate change due to alterations in the composition, diversity, and distribution of plants, floral resources, and pollinators. We tested if increasing CAD and aridity induces changes in pollen traits and female reproductive success of Tacinga palmadora , a self-compatible cactus that performs as an important food source for nectar-feeding and fruit-eating animals, in the Caatinga dry forest. The study was carried out in eight plots at the Catimbau National Park, northeastern Brazil. Each plot had a different level of disturbance and aridity, used as predictor variables against pollen traits (total pollen production, pollen viability, and pollen-ovule ratio) and female reproductive success (fruit- and seed-set by both open and spontaneous self-pollination) in generalized linear models. All pollen traits were negatively associated with increasing CAD and aridity intensity, while the seed- and fruit-set by open pollination were positively associated with increasing CAD and aridity, respectively. Spontaneous self-pollination was not influenced by increasing CAD and aridity. Our results revealed that even though pollen traits decrease with higher CAD and aridity, pollination of T. palmadora is maintained or even increased in the most arid and disturbed areas of the park. We conclude that, in terms of pollination effectiveness, T. palmadora might be thriving under disturbances and aridity in the Caatinga dry forest.