Setting the Stage: Climate, Geology, and Biota

Theodore H. Fleming

I review changes in the climate, geology, and biota of the New World tropics and subtropics over the past 30 million years to understand the physical and biological opportunities and constraints phyllostomid bats faced during their adaptive radiation. This radiation occurred during a period of  decreasing atmospheric CO2 levels, decreasing global air and sea temperatures, and increasing climatic seasonality that have led to the evolution of a great diversity of vegetation types, including tropical dry forests, montane forests, savannas, and deserts. Reinforcing the effects of temperature changes was the uplift of the major mountains in western North America, Central America, and western South America. Most of the extant diversity of New World noctilionoids is found on the Neotropical mainland in lowland forested habitats, which have existed in one form or another throughout the Americas since the late Cretaceous. A minority of species has evolved in more recent dry or arid habitats, in the mountains, or in the West Indies. Early phyllostomids were gleaning insectivores whose diets differed from those of other families of insectivorous bats. This foraging mode was a key adaptation that led to the radiation of later lineages into several novel (for the New World) dietary niches, including blood-feeding, vertebrate carnivory, nectarivory, and frugivory. Dietary overlap is low between plant-visiting phyllostomids and their avian and mammalian ecological counterparts, reflecting the outcome of coevolution between these bats and their food plants over the past 20 million years.