Plant Adaptations to Bats

As bats have evolved certain morphological and behavioral adaptations to favor flower visiting, so have plants developed similar specializations. The most common adaptation shared by all plants pollinated by bats is nocturnal flower blooming. By blooming at night, flowers become available only to nocturnal visitors and thus cause a very directional pollen transmission dynamic (Tschapka and Dressler 2002). Plants have also evolved a number of morphological adaptations to promote attraction and visitation by bats, as well as to maximize efficiency of conspecific pollen transfer. Since bats are long-distance pollinators, plant scent is a very important characteristic for bat flowers. Bat flowers are typically described as emitting scents considered to be unpleasant by humans, including scents resembling sour milk, chlorine, urine, and even cadavers or rotting meat (Tschapka et al. 2000). These scents likely attract bats due to their high potency, which can thus travel longer distances through the air and be detected more easily by swiftly flying bats (Tschapka and Dressler 2002). Many bat flowers have also evolved specialized structures that aid in reflecting bat echolocation signals so bats can easily identify them as a food source. An example of this is the highly specialized legume Mucuna holtonii, which will be discussed in further detail in the next blog post (Tschapka and Dressler 2002). 

Once bat flowers have attracted bats, they need to be able to withstand the large body size of bats in order to transfer pollen effectively. For this reason, many bat plants have developed large, robust platform-like structures for bats to land on while visiting the flower (Fig 1). This allows increased surface contact between the bat and plant, increasing the probability of successful pollen transfer (Tschapka and Dressler 2002). In addition, many bat plants have very conspicuous inflorescences that are highly accessible to hovering nectarivorous bats, and also increases the probability that bats will pick up and/or deposit pollen onto the flower stamen (Tschapka and Dressler 2002). In addition to morphology, most bat flowers have certain chemical adaptations to accommodate bat visitors. For example, bat plants often produce a very dilute nectar compared to that of other plants, which increases the frequency that bats visit other flowers of the same species and consequently increases the chance of conspecific fertilization (Tschapka and Dressler 2002).

Fig 1. Tschapka and Dressler, 2002. Large platform-like inflorescence of Macgravia nervosa to accommodate the large size of frequent nectarivorous visitor Hylonycteris underwoodii. Photo accessed 17/5/2015; Available: onlinelibrary.wiley.com. 

References

TSCHAPKA, M. and DRESSLER, S., 2002. Chiropterophily: On Bat–Flowers and Flower Bats. Curtis's Botanical Magazine, 19(2), pp. 114.