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

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.

How to be an ant on figs

“…In addition, there is a diversity of non-pollinating fig wasps (NPFWs, Hymenoptera, Chalcidoidea) (Compton and Hawkins, 1992;Kerdelhué and Rasplus, 1996;West et al, 1996;Kjellberg et al, 2005;Cruaud et al, 2011;Segar et al, 2012). These wasps include species, like the fig pollinator, that enter the fig during the receptive phase, but most NPFWs oviposit from outside the syconium by inserting their ovipositor through the syconium wall.…”

“…Among mutualistic interactions, the fig (Ficus) e fig pollinator interaction is often considered a model system (Herre and Jandér, 2010;Hossaert-McKey et al, 2010) and recent advances in the taxonomy of figs (Berg and Corner, 2005), their pollinators and nonpollinating fig wasps (NPFWs) (Cruaud et al, 2010(Cruaud et al, , 2011 render easier investigations of the interactions among insect communities supported by figs. The interaction between figs and their pollinators have frequently been the subject of both evolutionary (Weiblen, 2002;Cook and Rasplus, 2003;Kjellberg et al, 2005;Dunn et al, 2008;Cruaud et al, 2010;Herre and Jandér, 2010) and ecological study (Harrison, 2005;Hossaert-McKey et al, 2010).…”

Composition and structure of the fig wasp community in Amazonia

“…The same may be happening with morphospecies of the genus Aepocerus and Heterandrium (gall inducers), which oviposit approximately seven to twelve days prior to pollination (Rasplus and Soldati 2006). The genera Physothorax (Hanson 2006) and Eurytoma, (Burks 1971) are the last to colonise the syconia and are parasites of the larvae of the phytophagous species (West et al 1996;Murussich and Machado 2007;Cruaud et al 2011). Therefore, even though no data have been presented with respect to the feeding habits of the wasps, it is possible to infer that the period of ovipositing (during the reproductive phase of the fig) and the presence of the wasp host in the syconia could be influencing the frequency and/or abundance of the parasitoid wasp species.…”

First record of a non-pollinating fig wasp (Hymenoptera: Sycophaginae) from Dominican amber, with estimation of the size of its host figs

“…species by a combination of characters: 1) the presence of two anelli (rather than one) and 2) its relatively short ovipositor. The I. carme species-group is the most speciose group of Idarnes (Gordh 1975, Cruaud et al 2011b. They are known to occur throughout most of the distribution of Ficus section Americana, from southern Brazil to Florida (Gordh 1975).…”