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

Insect herbivores and their hostplants constitute much of Earth’s described metazoans, 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, can shape the diversification of phytophagous insect lineages. We generated two phylogenies primarily from momphid species in the nominate genus, Mompha (Hubner). The six-gene phylogeny was constructed with exemplars collected from Onagraceae hosts in western and southwestern USA. The Cytochrome Oxidase I phylogeny utilized both our collected sequences and publicly-available accessions from the Barcode of Life Data System. 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 leaf-mining clade, and 4) a heterogeneous clade associated with multiple hostplant families, plant tissues, and larval feeding modes. Coalescent-based analyses combined with morphological data found potentially 56 undescribed Mompha species-level taxa, many of which are larval hostplant specialists on southwestern USA Onagraceae. Ancestral trait reconstructions identified leaf-mining on Onagraceae as the ancestral state for Momphidae. Cophylogenetic analyses detected loose phylogenetic tracking of host plant 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 host plant families indicated that exploited host tissue (without a change in host) plays an unexpectedly large role in the evolutionary success of this diverse group of microlepidopteran moths.