Evolution of convergent adaptations in cryptine ichneumonid wasps: a morphospace approach

With 241 genera and over 2,400 species worldwide, cryptine wasps are a dominant but poorly known group of insects that parasitize immature stages of moths, beetles and other insects. These hosts are usually concealed to various degrees, from leaf rolls and twigs to hard clay nests or wood. Therefore, several taxa developed morphological adaptations to find and assess deeply concealed hosts. Such features include a specialized antennal tip to tap hard substrates, producing pulses of sound; swollen mechanoreceptor organs to detect vibrations; a stout, hardened ovipositor; and enlarged oviposition muscles. All these traits make cryptines ideal for studying the evolution of parasitism life strategies.

This work presents the first comprehensive phylogenetic analysis of Cryptini, often considered “taxonomically difficult” and “challenging” by researchers for their overwhelming diversity and intense morphological homoplasy. The ingroup includes 300 species belonging to 190 genera from all biogeographic regions. The dataset comprises molecular data from two mitochondrial and five nuclear loci, plus 162 phenotypic characters.

The resulting phylogeny shows little correspondence to the current supra-generic classification, highlighting the need for systematic revision in the tribe. It also demonstrates that host location adaptations evolved several times in the cryptine tree of life. The data are then used to investigate the hypothesis that host location characters are part of a complex morpho-functional system, and that the convergence of life strategies imposes constraints in the morphospace occupied by cryptine wasps. Statistical methods are used to (1) reconstruct ancestral states for the characters under investigation; (2) test hypotheses of correlation among life history traits and multiple phenotypic characters; and (3) assess the overlap in the morphospace occupied by convergent lineages.