Phylogeny and evolution of life-history strategies in the Sycophaginae non-pollinating fig wasps (Hymenoptera, Chalcidoidea).

Astrid Cruaud,Yang Da-Rong,Fernando Ha Farache,Finn Kjellberg,Roula Jabbour-Zahab,Otilene Santos-Mattos,Simon Van Noort,Carole Kerdelhué,Peng Yan-Qiong,Noppol Kobmoo,Paul E Hanson,Jean-Yves Rasplus,Rosichon Ubaidillah,Gwenaëlle Genson,Rodrigo As Pereira

doi:10.1186/1471-2148-11-178

Abstract

BackgroundNon-pollinating Sycophaginae (Hymenoptera, Chalcidoidea) form small communities within Urostigma and Sycomorus fig trees. The species show differences in galling habits and exhibit apterous, winged or dimorphic males. The large gall inducers oviposit early in syconium development and lay few eggs; the small gall inducers lay more eggs soon after pollination; the ostiolar gall-inducers enter the syconium to oviposit and the cleptoparasites oviposit in galls induced by other fig wasps. The systematics of the group remains unclear and only one phylogeny based on limited sampling has been published to date. Here we present an expanded phylogeny for sycophagine fig wasps including about 1.5 times the number of described species. We sequenced mitochondrial and nuclear markers (4.2 kb) on 73 species and 145 individuals and conducted maximum likelihood and Bayesian phylogenetic analyses. We then used this phylogeny to reconstruct the evolution of Sycophaginae life-history strategies and test if the presence of winged males and small brood size may be correlated.ResultsThe resulting trees are well resolved and strongly supported. With the exception of Apocrytophagus, which is paraphyletic with respect to Sycophaga, all genera are monophyletic. The Sycophaginae are divided into three clades: (i) Eukoebelea; (ii) Pseudidarnes, Anidarnes and Conidarnes and (iii) Apocryptophagus, Sycophaga and Idarnes. The ancestral states for galling habits and male morphology remain ambiguous and our reconstructions show that the two traits are evolutionary labile.ConclusionsThe three main clades could be considered as tribes and we list some morphological characters that define them. The same biologies re-evolved several times independently, which make Sycophaginae an interesting model to test predictions on what factors will canalize the evolution of a particular biology. The ostiolar gall-inducers are the only monophyletic group. In 15 Myr, they evolved several morphological adaptations to enter the syconia that make them strongly divergent from their sister taxa. Sycophaginae appears to be another example where sexual selection on male mating opportunities favored winged males in species with small broods and wingless males in species with large broods. However, some species are exceptional in that they lay few eggs but exhibit apterous males, which we hypothesize could be due to other selective pressures selecting against the re-appearance of winged morphs.

Highlights

Non-pollinating Sycophaginae (Hymenoptera, Chalcidoidea) form small communities within Urostigma and Sycomorus fig trees
Our analyses indicate positive evolutionary correlations between large gall types/small brood sizes and winged males (Anidarnes + Pseudidarnes + Conidarnes clade and Idarnes incerta group all belonging to group 1 (Figure 6), a result that was previously reported for other non-pollinating fig wasps (NPFW) [61] and supports Hamilton’s hypothesis [72]
We show that life history strategies of Sycophaginae are evolutionary labile, such that distantly related taxa share similar galling habits and vice-versa

Summary

Introduction

Non-pollinating Sycophaginae (Hymenoptera, Chalcidoidea) form small communities within Urostigma and Sycomorus fig trees. We sequenced mitochondrial and nuclear markers (4.2 kb) on 73 species and 145 individuals and conducted maximum likelihood and Bayesian phylogenetic analyses We used this phylogeny to reconstruct the evolution of Sycophaginae life-history strategies and test if the presence of winged males and small brood size may be correlated. Male dimorphism or polymorphism is common in species in which sexual selection is strong [2,3] and takes place in a variety of taxonomic groups such as insects (e.g. bees and wasps [4,5], damselflies [6], earwigs [7], dung-beetles [8]); other invertebrates (e.g. spiders [9], opiliones [10], mites [11], amphipods [12] and nematodes [13]) and vertebrates [14,15]. Wingless males engage in lethal combat for access to females [16,29,30], and exhibit considerable morphological diversity [20,25], whereas winged males disperse to mate with females outside the syconium

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