Plant geographic phenotypic variation drives diversification in its associated community of a phytophagous insect and its parasitoids

Abstract

BackgroundWhile the communities constituted by phytophageous insects and their parasites may represent half of all terrestrial animal species, understanding their diversification remains a major challenge. A neglected idea is that geographic phenotypic variation in a host plant may lead to heterogeneous evolutionary responses of the different members of the associated communities. This could result in diversification on a host plant by ecological speciation in some species, leading to geographic variation in community composition. In this study we investigated geographic variation of inflorescence receptacle size in a plant, Ficus hirta, and how the hymenopteran community feeding in the inflorescences has responded. Our predictions were:Inflorescence size variation affects wasp species differently depending on how they access oviposition sites.In some affected lineages of wasps, we may observe vicariant, parapatric species adapted to different inflorescence sizes.ResultsWe show that fig (the enclosed inflorescence of Ficus) wall thickness varies geographically. The fig-entering pollinating wasp was not affected, while the parasites ovipositing through the fig wall were. Two parapatric species of Philotrypesis, exhibiting strikingly different ovipositor lengths, were recorded. One species of Sycoscapter was also present, and it was restricted, like the shorter-ovipositor Philotrypesis, to the geographic zone where fig walls were thinner.ConclusionsPrevious work on fig wasps suggested that parapatric geographic ranges among congenerics were due to adaptation to variation in abiotic factors, complemented by interspecific competition. Our results show that parapatric ranges may also result from adaptation to variation in biotic factors. Within an insect community, differences among species in their response to geographic phenotypic variation of their host plant may result in geographically heterogeneous community structure. Such heterogeneity leads to heterogeneous interaction networks among sites. Our results support the hypothesis that plant geographic phenotypic variation can be a driver of diversification in associated insect communities, and can complement other diversification processes.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1239-5) contains supplementary material, which is available to authorized users.

Low host specificity and broad geographical ranges in a community of parasitic non‐pollinating fig wasps (Sycoryctinae; Chalcidoidea)

“…Three non-pollinating chalcid fig-wasp species have been reported from F. hirta (Yu et al, 2018). Philotrypesis josephi and Sycoscapter hirticola in northeast India (Nair et al, 1981) and Sycoryctes simplex in Java (Mayr, 1885) itates the initial establishment of rare colonisers (Yu et al, 2019).…”

Plants Are the Drivers of Geographic Variation of Floral Scents in a Highly Specialized Pollination Mutualism: a Study of Ficus Hirta in China

“…We used the head-space technique following methods initially developed for Silene [57] and that have been successfully used in several Ficus species [34,51,58,59]. As the size of receptive gs varied geographically [60], in order to collect su cient quantities of odour for the analysis, the number of gs used in each bag was adjusted according to g diameter: for south-eastern locations 13 ± 4, for southern locations 17 ± 4, and for the south-western location 19 ± 10. Odour collection was performed under natural light between 10:00 am and 5:00 pm, corresponding to the insects' period of maximum activity during our eld season.…”

The Extent of Pollinator Sharing Among Fig Trees in Southern China

“…The clades with high gene sequence differences (larger than 0.02), were blasted to Genbank with the rst 1-3 sequences sorted by percent identity. Two species of non-pollinating g wasps reared from F. hirta, Sycoscapter hirticola (MG548706) and Philotrypesis josephi (MG548673 and MG548674, both Pteromalidae) were included as outgroups (Yu et al 2018).…”