Bat pollination in the Caatinga: A review of studies and peculiarities of the system in the new world's largest and most diverse seasonally dry tropical forest

Abstract

Bat pollination is one of the most recent pollination systems to have been discovered. While recent studies have provided novel insight into bat-flower interactions, there are gaps in knowledge regarding their geographic distribution, the role of floral traits in ensuring attractiveness and mechanical fit to bats, and details of the structure of interaction networks between plants and bats. Here, we review bat pollination in the Caatinga, the largest and most diverse Seasonally Dry Tropical Forest in the Neotropics, and a global hotspot for this pollination system. The first records of bat pollination date back less than 20 years and were mostly confined to a small area in the eastern part of the Caatinga. Over the last two decades, bat pollination has been confirmed for 22 genera of flowering plants from 12 families, through both direct observations and pollen records. Recent investigations of the floral biology of bat-pollinated plant species have revealed the role of floral traits such as styliflory, fragrant nectar, as well as white and greenish flowers without reflection in the ultraviolet range. Bat-pollinated plants in the Caatinga interact with at least 11 bat species (6 species of opportunistic and 5 species of specialized nectarivores). We list here another 126 Caatinga plant species that potentially might be bat-pollinated and should be targeted in future investigations. The high potential incidence of bat pollination (4.8% of the estimated flora) seems to be a peculiar feature of the Caatinga. We emphasize the urgency to perform nocturnal forays that will help to understand how bat pollination systems evolved in dry forests. This is particularly important because, similar to many other dry forests, the Caatinga is particularly sensitive to anthropogenic disturbance and there is currently a considerable risk that many plant species will be lost before their pollination biology is fully understood.