Preference of an insular flying fox for seed figs enhances seed dispersal of a dioecious species

Abstract

Interactions among multiple species form complex networks of interdependences and are considered primary factors in the generation and maintenance of biodiversity. Pteropodid bats are keystone species that provide important ecosystem services of pollination and seed dispersal in the tropics and subtropics. In this study, we investigated the utilization and preference of food resources by the insular frugivorous flying fox Pteropus dasymallus. We found that fig species constituted the major portion of the diet of the flying fox (94.6%). When foraging, the flying fox preferred seed figs from female trees over gall figs from male trees in functionally dioecious fig species. Germination experiments showed a significantly higher percentage of germination for fig seeds in feces than those from pellets and ripe figs (feces: 80.2%, pellets: 23.4%, ripe figs: 32.9%). Considering the active selection of seed figs and avoidance of gall figs by foraging flying foxes, we suggest that the abundance of seed figs accurately represents food availability for dioecy. This preference for seed figs or viable seeds can effectively promote the survival of pollinating wasps and might reinforce the evolution of dioecism in figs. In addition, the effects of gut passage on seed germination, in combination with the capacity of flying foxes to travel long distances, may substantially contribute to the efficiency of flying foxes as seed dispersers.

Differentiation during fig ontogeny suggests opposing selection by mutualists

“…Our results also demonstrate, as predicted, that seed dispersers are attracted far more frequently to monoecious and seed figs than to gall figs. Although previous studies suggest a preference of frugivores for seed figs over gall figs (Chen et al, ; Dumont et al, ; Lambert, ), we know of no other study that systematically quantified diurnal and nocturnal visitation to gall and seed fig trees, and that included monoecious figs. With almost 770 hr of observations from a total of 50 trees, we feel confident in concluding that monoecious and seed figs are visited by frugivores far more often than gall figs.…”

“…Third, Lambert () counted 1,154 gall syconia of one F. parietalis tree and recovered most of them (1,128) as they fell to the ground uneaten. Chen et al () recorded most bat activity, as measured by pellets and feces with viable seeds, left mostly under female trees of Ficus septica ; conspecific trees with gall syconia rarely showed the same signs of visitation by bats. We conclude that differentiation of gall and seed syconia at the fruit stage almost certainly enhances the male component of fig fitness, as it greatly reduces the risk of consumption of pollinators in seed figs by seed dispersers.…”

“…Volatiles, however, may not tell the complete story. Although frugivores seem to prefer seed over gall figs (Chen et al, ; Lambert, ), the evidence is mostly anecdotal and at least some frugivorous bats do find and consume figs that lack the traits typical of mammal‐dispersed species, including fruit odor (Lomascolo et al, ).…”

Peer Review #1 of "Development and characterization of a multiplex panel of microsatellite markers for the Reunion free-tailed bat Mormopterus francoismoutoui (v0.1)"

“…About a quarter of over 1,300 currently known bat species are endemic to islands (Conenna et al, 2017), in which they sometimes represent the only indigenous mammals. These islandrestricted bats play important roles in insular ecosystems through seed dispersal, pollination, and pest control (Aziz et al, 2017;Chen et al, 2017;Kemp et al, 2019). They are also significantly more threatened than continental bat species because of a limited resilience to the combined effects of natural disturbances, typical of island ecosystems, and anthropogenic threats such as urbanization or the development of intensive agriculture (Jones et al, 2009).…”

Development and characterization of a multiplex panel of microsatellite markers for the Reunion free-tailed bat Mormopterus francoismoutoui

“…About a quarter of over 1,300 currently known bat species are endemic to islands (Conenna et al, 2017), in which they sometimes represent the only indigenous mammals. These island-restricted bats play important roles in insular ecosystems through seed dispersal, pollination, and pest control (Aziz et al, 2017; Chen et al, 2017; Kemp et al, 2019). They are also significantly more threatened than continental bat species because of a limited resilience to the combined effects of natural disturbances, typical of island ecosystems, and anthropogenic threats such as urbanization or the development of intensive agriculture (Jones et al, 2009).…”