Diversification in the microlepidopteran genus Mompha (Lepidoptera: Gelechioidea: Momphidae) is explained more by tissue specificity than host plant family.

Abstract

Insect herbivores and their hostplants constitute much of Earths described diversity, but how these often-specialized associations evolve and generate biodiversity is still not fully understood. We combined detailed hostplant data and comparative phylogenetic analyses of the lepidopteran family Momphidae to explore how shifts in the use of hostplant resources, not just hostplant taxonomy, contribute to the diversification of phytophagous insect lineages. We generated two phylogenies primarily from momphid species in the nominate genus, Mompha Hubner. A six-gene phylogeny was constructed with exemplars from Onagraceae hosts in western and southwestern USA and a cytochrome c oxidase subunit 1 (COI) phylogeny utilized both our collected sequences and publicly available accessions from the Barcode of Life Data System. Coalescent-based analyses combined with morphological data revealed ca. 56 undescribed Mompha species-level taxa, many of which are hostplant specialists on southwestern USA Onagraceae. Our phylogenetic reconstructions identified four major momphid clades: 1) an Onagraceae flower- and fruit-feeding clade, 2) a Melastomataceae galling clade, 3) an Onagraceae and Rubiaceae leafmining clade, and 4) a heterogeneous clade associated with multiple hostplant families, plant tissues, and larval feeding modes. Ancestral trait reconstructions on the COI tree identified leafmining on Onagraceae as the ancestral state for Momphidae. Cophylogenetic analyses detected loose phylogenetic tracking of hostplant taxa. Our study finds that shifts along three hostplant resource axes (hostplant taxon, plant tissue type, and larval feeding mode) contributed to the evolutionary success and diversification of Mompha. More transitions between exploited host tissue types than between hostplant families indicated that exploited host tissue (without a change in host) played an unexpectedly large role in the diversification of these moths.