Host‐parasitoid relationships within figs of an invasive fig tree: a fig wasp community structured by gall size

Abstract

Revealing the host specificity of the predators/parasitoids of invasive species is a prerequisite when assessing the suitability of biocontrol agents, while the host ranges of top predators are likely to vary among communities comprising different species. Ficus microcarpa is a native plant in Asia and Australasia and has invaded in sometropical and subtropical areas. Besides its species‐specific pollinator, its figs also support many ovule‐galling and parasitoid non‐pollinating fig wasps. Here, based on a global collection of fig wasps associated with F. microcarpa figs, we used path analysis, supplemented by within‐fig spatial distributions and natal gall sizes to reveal food web structure of its associated fig wasps and the factors forming host ranges of parasitoids. The fig wasp community was species‐rich, and parasitoids were far rarer in the plant's introduced range. Parasitoids exhibited some host specificity, and four specific natural enemies of the plant's pollinator were identified with various intensities of effects on pollinator abundance. Parasitoid host ranges were consistent in both ranges of the plant, and mainly restricted by the size and the locations of host galls. No parasitoids were found associated with a unique seed predator. Our results showed how a large number of fig wasp species partition one host fig tree's figs and identified the species that have potential to control the sexual reproduction of F. microcarpa.

Loss of top-down biotic interactions changes the relative benefits for obligate mutualists

“…Several NPFWs have become established in translocated populations of F. microcarpa [25,39]. Agaonids are the major hosts of NPFWs from the subfamily Sycoryctinae (Pteromalidae), and the host ranges of these parasitoids do not vary between the native and the translocated ranges of F. microcarpa [33].…”

“…Translocated F. microcarpa can set viable seed because of the widespread colonization of its pollinator [25]. Outside the plant's natural range, some NPFWs have also colonized the plant, but parasitoids of pollinator offspring are rare or absent [25,33].…”

Non‐pollinating cheater wasps benefit from seasonally poor performance of the mutualistic pollinating wasps at the northern limit of the range of Ficus microcarpa

“…In Xishuangbanna, Yunnan, year-round observations on Ficus altissima show that seasonal abundance patterns also differ between cheaters and pollinators (Peng et al, 2010). Also, in Yunnan, a third cheater species has been identified in Ficus microcarpa (Martinson et al, 2014;Wang et al, 2015;Compton et al, 2018). It is unknown how this cheater's seasonal occurrence patterns compare with the pollinator and their host fig's phenology.…”

The nature of interspecific interactions and co‐diversification patterns, as illustrated by the fig microcosm

“…We retained these species in the phylogenetic analysis to illustrate their relationships, but we excluded them from the co‐phylogenetic analyses because they are not mutualists and are distantly related to and functionally different from the other parasitic wasp species. All other parasitic wasp species produce flower galls on which their larvae feed (Kerdelhué et al ., ; Compton et al ., ; Y. Q. Peng, unpublished), so we refer to them as galling wasps. Unlike the pollinating wasps, the galling species lay eggs in ovules from outside syconia using elongate ovipositors (Kerdelhué et al ., ).…”