Abstract
Insect herbivores and their hostplants constitute much of Earth’s described biological diversity, but how these often-specialized associations diversify is 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 taxon, contribute to the diversification of a phytophagous insect lineage. We inferred two phylogenetic hypotheses emphasizing relationships among species in the nominate genus, Mompha Hübner. A six-gene phylogeny was constructed with reared exemplars and collections from hostplants in the family Onagraceae from western and southwestern USA, and a cytochrome c oxidase subunit 1 (COI) phylogeny was inferred from collections and publicly available accessions in the Barcode of Life Data System. Species delimitation analyses combined with morphological data revealed ca. 56 undescribed species-level taxa, many of which are hostplant specialists on Onagraceae in the southwestern USA. Our phylogenetic reconstructions divided Momphidae into six major clades: 1) an Onagraceae flower- and fruit-boring clade, 2) a Melastomataceae-galling clade, 3) a leafmining clade A, 4) a leafmining clade B, 5) a Zapyrastra Meyrick clade, and 6) a monobasic lineage represented by Mompha eloisella (Clemens). Ancestral trait reconstructions using the COI phylogeny identified leafmining on Onagraceae as the ancestral state for Momphidae. Our study finds that shifts along three hostplant resource axes (plant taxon, plant tissue type, and larval feeding mode) have contributed to the evolutionary success and diversification of momphids.
Highlights
Phytophagous insects constitute nearly a quarter of described metazoan diversity [1,2], and phytophagy represents the predominant feeding habit in many of the largest insect orders
We address the following questions: (1) What are the phylogenetic relationships among momphids? (2) What is the ancestral hostplant taxon, tissue resource, and feeding mode of momphids? (3) Are shifts to new hostplant tissues and changes in larval feeding modes as prevalent as shifts to new hostplant family? We examined these questions with two data sets by (1) reconstructing a six-gene phylogeny primarily consisting of a subset of momphids from Onagraceae-feeding Mompha from the southwestern
For each hostplant resource axis within each hostplant population, we found near-identical c oxidase subunit 1 (COI) sequences, which suggests that momphid species typically occupy a unique hostplant niche, validating our sampling scheme
Summary
Phytophagous insects constitute nearly a quarter of described metazoan diversity [1,2], and phytophagy represents the predominant feeding habit in many of the largest insect orders (especially Coleoptera, Hemiptera, and Lepidoptera). Dietary specialization is a major factor in the diversification of phytophagous insect groups [5,6,7,8,9]. The colonization of a new hostplant niche sometimes triggers the process of specialization, whereby processes such as local adaptation, assortative mating, and divergent selection lead to isolation and speciation [13,14,15,16,17]. Geographic factors play a strong role in insect speciation [20,21,22,23], as populations become isolated by geographic barriers [24] or as a consequence of limited dispersal [25]
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