A tale of long tails: Evolution of host specialization in non-pollinating fig wasps

Abstract

The evolution of host specialization and feeding habits in non-pollinating fig wasps remains poorly understood. This study investigates these dynamics within the wasp genus Idarnes, which exhibits diverse life strategies and degrees of host specificity. We reconstructed the phylogeny of 57 Idarnes species using four genetic markers—two mitochondrial, one nuclear and one ribosomal—and performed ancestral state reconstructions to elucidate the evolution of host specialization. Our analyses reveal that host monophagy is ancestral in Idarnes, with oligophagy evolving independently in several lineages. Oligophagous species are more prevalent in kleptoparasitic compared to gall-inducing lineages. Early gallers—which are wasps that colonize figs during the pre-receptive stage of development—are predominantly monophagous, while some oligophagous species occur in the galler lineage that uses flower ovaries at the fig receptive phase. The relative ovipositor length correlates with the number of host species visited by kleptoparasite species, suggesting morphological adaptations play a role in host specialization. In the gall-inducing lineages, the use of multiple host species seems not primarily constrained by the ovipositor size but possibly by the capacity of the wasp to induce galls in a non-typical host species. This study provides valuable insights into the mechanisms driving host specialization in fig wasps, enhancing our understanding of this intricate insect-plant system.