Supply determines demand: influence of partner quality and quantity on the interactions between bats and pitcher plants

Abstract

Interspecific relationships such as mutualism and parasitism are major drivers of biodiversity. Because such interactions often comprise more than two species, ecological studies increasingly focus on complex multispecies systems. However, the spatial heterogeneity of multi-species interactions is often poorly understood. Here, we investigate the unusual interaction of a bat (Kerivoula hardwickii hardwickii) and two pitcher plant species (Nepenthes hemsleyana and N. bicalcarata) whose pitchers serve as roost for bats. Nepenthes hemsleyana offers roosts of higher quality, indicated by a more stable microclimate compared to N. bicalcarata but occurs at lower abundance and is less common than the latter. Whereas N. hemsleyana benefits from the roosting bats by gaining nitrogen from their feces, the bats' interaction with N. bicalcarata seems to be commensal or even parasitic. Bats stayed longer in roosts of higher quality provided by N. hemsleyana and preferred them to pitchers of N. bicalcarata in a disturbance experiment. Moreover, bats roosting only in pitchers of N. hemsleyana had a higher body condition and were less infested with parasites compared to bats roosting in pitchers of N. bicalcarata. Our study shows how the local supply of roosts with different qualities affects the behavior and status of their inhabitants and-as a consequence-how the demand of the inhabitants can influence evolutionary adaptations of the roost providing species.

Bats Are Acoustically Attracted to Mutualistic Carnivorous Plants

“…The bat droppings enhance the nitrogen intake of N. hemsleyana by 34% on average [10]. In turn, the pitcher plants provide the bats with roosts that are free of parasites, have a stable microclimate, and offer enough roosting space for one or two bats while at the same time preventing the bats from falling into the digestive fluid due to their unique morphological shape and low fluid level [11]. Finding and identifying N. hemsleyana pitchers that grow in the dense Bornean peat swamp forests, however, is a challenging task for echolocating bats: they have to distinguish echoes of the pitchers from those of the cluttered surroundings [13,14].…”

“…Finding and identifying N. hemsleyana pitchers that grow in the dense Bornean peat swamp forests, however, is a challenging task for echolocating bats: they have to distinguish echoes of the pitchers from those of the cluttered surroundings [13,14]. The situation is further complicated by the fact that the bats need to distinguish the rare [11,15] N. hemsleyana pitchers from the more common and similarly shaped pitchers of sympatric Nepenthes species, which are unsuitable for roosting [10].…”

“…Bats were caught in harp traps or in Nepenthes pitchers [11]. Call recordings and experiments were filmed in a flight arena (3.5 m 3 3.5 m, height 2.5 m).…”

Reinstatement of Nepenthes hemsleyana (Nepenthaceae), an endemic pitcher plant from Borneo, with a discussion of associated Nepenthes taxa

“…As highlighted by , a number of authors have observed or experimentally demonstrated stable ecological, physiological and morphological differences between two subgroups within the taxon N. rafflesiana sensu Danser, comprising different UV reflectance patterns, scent production and capture rate (Moran 1996), the different ontogeny of pitcher morphology (Gaume & Di Giusto 2009), alternative insect trapping strategies (Bauer et al 2011), and a mutualistic interaction with bats exclusive for one subgroup , Schöner et al 2013. Although the two subgroups were clearly understood by all of the specialists, the nomenclature used has been informal and inconsistent, until Independent from all of the work above, N. rafflesiana var.…”

Sensory Biology: Acoustic Reflectors Attract Bats to Roost in Pitcher Plants

“…All 17 radio-tracked bats followed in Borneo roosted exclusively in pitchers of Nepenthes hemsleyana [4]. The roosting bats in turn increase the nitrogen intake of the plant by a third [8]. Hence, Michael and Caroline Schö ner joined forces with Ralph Simon who had previously measured echo reflectivity in bat-pollinated plants to ask whether pitcher plants have ultrasonic reflectors that might enhance their conspicuousness to echolocating bats.…”