Adaptation of Fig Wasps (Agaodinae) to Their Host Revealed by Large-Scale Transcriptomic Data.

Lianfu Chen,Simon T Segar,Xiaoyong Chen,Bhanumas Chantarasuwan,Da-Mien Wong,Rong Wang,Hui Yu

doi:10.3390/insects12090815

Abstract

Simple SummaryResearch on fig wasps has made a considerable contribution to the understanding of insect–plant interactions. However, the molecular mechanisms underlying fig wasp host specificity are poorly understood. This study reports on a relatively large-scale transcriptomic dataset of 25 fig wasp species. We outline potential genetic mechanisms underlying the specific host adaptation by investigating changes in a gene family, in evolutionary rates, and in genes under positive selection. The transcriptome datasets reported here (1) provide new insights into the evolutionary diversification and host specificity of fig wasps and (2) contribute to a growing dataset on fig wasp genomics.Figs and fig wasps are highly species-specific and comprise a model system for studying co-evolution and co-speciation. The evolutionary relationships and molecular adaptations of fig wasps to their fig hosts are poorly understood, and this is in part due to limited sequence data. Here, we present large-scale transcriptomic datasets of 25 fig wasp species with the aim of uncovering the genetic basis for host specificity. Our phylogenetic results support the monophyly of all genera associated with dioecious figs, and two genera associated with monoecious figs, Eupristina and Platyscapa, were revealed to be close relatives. We identified gene loss and gain, potentially rapidly evolving genes, and genes under positive selection. Potentially functional changes were documented and we hypothesize as to how these may determine host specificity. Overall, our study provides new insights into the evolutionary diversification of fig wasps and contributes to our understanding of adaptation in this group.

Highlights

Intimate inter-specific interactions are pervasive in nature
Using the Trinity program, next-generation short-read sequences of the other 24 fig wasp species were assembled into 36,024–82,380 transcripts, of which 22,468–44,976 were coded after filtering by TPM expression and ORF search (Supplementary Materials, Table S1)
These results indicate that the transcripts assembled for this species were relatively fragmented; for example, a complete sequence obtained in other species would be two fragments in this species

Summary

Introduction

Intimate inter-specific interactions are pervasive in nature. Species embedded within these complex networks have consumed each other, provided provisions for each, and competed over ecological and evolutionary time [1].Evidence for co-evolution in the strict sense is rare [2], but insects and plants clearly form part of each other’s selective landscapes. Intimate inter-specific interactions are pervasive in nature. Species embedded within these complex networks have consumed each other, provided provisions for each, and competed over ecological and evolutionary time [1]. Evidence for co-evolution in the strict sense is rare [2], but insects and plants clearly form part of each other’s selective landscapes. Reciprocal selection appears to trigger increased rates of diversification [3]. It is likely that “diffuse” co-evolution acting among groups of individuals is more widespread [4]. A mechanistic understanding of how selection shapes genomic architecture is hard to achieve in a multispecies setting. Simpler systems that offer a degree of phenotypic matching represent attractive opportunities

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Discussion

Conclusion