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

Abstract

1. Species interactions in tightly bound ecological mutualisms often feature highly specialised species' roles in which competitive exclusion may preclude multi‐species coexistence. Among the 800 fig (Ficus) species, it was originally considered that each was pollinated by their own wasp (Agaonidae). However, recent investigations show that this ‘one‐to‐one’ rule often breaks down, as fig species regularly host multiple agaonids but in ways suggesting that competitive processes still mediate biodiversity outcomes. 2. A phenological survey was conducted of the fig–fig wasp pair, Ficus microcarpa and its associated pollinating wasp, alongside its sister species, the cheating wasp, in Xishuangbanna, China. 3. Reproductive output underwent extreme seasonal variation. Seed and pollinator production fell markedly during cooler, drier months, although high levels of fig production continued. However, this resource was predominantly utilised by the cheater species, which offers no pollination services. Pollinators and cheaters rarely co‐occur, suggesting that temporal coexistence is constrained by competition for access to figs. 4. The overall findings indicate periodic rearrangements of mutualism dynamics, probably resulting from a strongly seasonal environment. Sympatric co‐occurrence may result from a window of opportunity for a functionally divergent agaonid, potentially due to constraints on the main pollinator in adapting to variable year‐round conditions that prevent competitive exclusion.

The evolution of parasitism from mutualism in wasps pollinating the fig, Ficus microcarpa , in Yunnan Province, China

“…Taken together, these studies are consistent with the concept of a geographical mosaic (57,59). Pending further detailed studies, we suggest that different populations of F. microcarpa will exhibit predictably different sanction strengths against cheating wasps at local and regional scales (55,(57)(58)(59).…”

“…S2 and Table S2). We note that the single foundress situation is common in nature, as it represents roughly 65% of all figs in F. microcarpa at this locale (55). Direct competition with P+ pollinators and cheaters sharing a fig.…”

“…5) Given that cheaters exhibit equal or greater fitness than the pollinator, how do they coexist? Although deserving further study, we suggest that regular seasonal fluctuations in the relative abundances of the two wasp species facilitate their coexistence at this site (54,55). Seasonal changes in the prevalence of westerly winds cause regional spatial heterogeneity in source pools of pollinators and cheaters that immigrate to the local host, F. microcarpa.…”

“…Here, we exploit the opportunity provided by a third case (54,55), in which a mutualistic active pollinator and a congeneric cheater species co-occur on the same monoecious host fig. Specifically, we conducted a combination of behavioral, morphological, phylogenetic, and experimental studies to compare these wasps and the outcomes of their interactions with their shared host fig, Ficus microcarpa (subgenus Urostigma: section Urostigma: subsection Conosycea), in and near the Xishuangbanna Tropical Botanical Garden (XTBG), China.…”

“…Eupristina verticillata is the described active pollinator of F. microcarpa at this location, while an undescribed coexisting wasp species (Eupristina sp.) lacks the necessary adaptation for active pollination and appears to be a cheater (54,55).…”