Phylogeny

Bats have been around for 52.5 million years and are the only mammals capable of flight.  They belong to the order Chiroptera, which is traditionally split into Megachiroptera (also known as Old World fruit bats), larger fruit eating bats, and Microchiroptera, smaller, echolocating bats.  Although bats are split into these two suborders, not much has been established about their evolution, and there is some speculation that Microchiroptera and Megachiroptera do not share a common ancestor (8).


 

 

Onychonycteris finneyi, the oldest bat fossil dating back to 52.5 million years ago, was discovered in Wyoming’s Green River Formation (13).

 

 

 

 

 

 

 

 

 

 

Folivory is observed in 17 out of about 200 species of Megachiroptera, which mostly consume fruits, flowers, and flower products such as nectar (1).  Compared to the teeth of non-fruit eating bats like those in the Microchiroptera suborder, Megachiroptera bats have developed large and flat grinding teeth that enable them to ingest fruit. It has also been discovered that these "robust dentitions" make it easier for fruit bats to consume leaves (2). These differences can be observed in the below image. The mandible of the fruit bat is elongated and its molars are larger.

Microchiroptera on left, Megachiroptera on right (14).

The digestive tract of Megachiroptera is suited for a liquid diet and rapid food passage. Since fruit bats only swallow the liquid fraction that they separate from the leaf fibers, they are still be able to eat leaves (2). Megachiroptera also have longer intestine and stomachs than the Microchiroptera, which better serve for digesting fruit, whereas the Microchiroptera mainly eats insects and don’t require much digestion (2).

Microchiroptera largely obtain their food through echolocation.  Thus, they have smaller eyes since echolocation is their primary sense for finding food (8). On the other hand, the large eyes and keen nose of the Megachiroptera serve as its major locational senses, making it better suited for finding larger objects such as fruit rather than smaller insects and such.  This probably also makes it easier for the Megachiroptera to identify edible leaves.

There are only 5 species out of about 900 species in the Microchiroptera suborder that display folivory, but this is thought to have evolved independently. Folivory has been found to evolve independently in several other animal taxa so it is likely that folivory also evolved independently in Megachiroptera (6, 8). Overall, the anatomical structure of fruit bats, which is suitable for a diet of fruit, is also suitable for eating leaves. This factor probably contributed to the possibility that folivory would evolve in fruit bats.