Megastigmidae (Hymenoptera: Chalcidoidea) - phylogeny, evolution, and reclassification of the family
Abstract
Megastigmidae, comprising about 250 species in 18 genera and 3 subfamilies (Keiraninae,
Chromeurytominae and Megastigminae), is primarily found in the Australian region, although a few genera are present in other biogeographic regions. Megastigmidae exhibits diverse life- history strategies. Some genera feed on seeds of angiosperms or gymnosperms, while others are parasitoids, and one genus is suggested to be gall-maker. Our study is the first to: 1) produce a robust phylogeny for Megastigmidae; 2) use it to determine its biogeographic area of origin and identify its ancestral feeding strategy; 3) reclassify the family. We sequenced ca. 900 UCEs for >100 specimens from all known genera and species groups of Megastigminae, chosen to represent all feeding strategies and the world distribution of the subfamily,
Chromeurytoma (Chromeurytominae) and Keirana (Keiraninae). For all taxa ca. 140 external morphological characters were scored and used to define genera of Megastigmidae. The family originated in the Australian region and colonized the world in several waves. Our analyses suggest that parasitoidism is the most likely ancestral feeding strategy of the family, with subsequent shifts, at least three times, to phytophagy. Keiraninae and
Chromeurytominae, sister clade to Megastigminae, are considered parasitoids. Megastigminae is subdivided into three subclades. The first clade comprises species that are primarily phytophagous, including gall-makers. The second clade likely consists exclusively of parasitoid species. Within the third clade, phytophagy has independently evolved at least twice. Using both morphological and molecular data, we almost doubled the number of genera of Megastigmidae and hence propose a new classification of the family.