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ABSTRACT Limnephilidae is a species‐rich and ecologically diverse family within the tube case making clade of caddisflies (Trichoptera). Species occur across a wide range of habitats, from cold headwater streams to stagnant pools to terrestrial environments. Here, we sequenced, assembled, and annotated whole genomes from two species that are associated with terrestrial environments:Enoicyla pusilla(Burmeister, 1839), distributed in the West Palearctic, andPhilocasca rivularis(Wiggins, 1968), distributed in the Nearctic. Comprising three species,Enoicylais the only genus of Trichoptera in Europe that exhibits a completely terrestrial life‐cycle. As one of four species ofPhilocasca, larvae ofP. rivularisalso exhibit terrestrial behavior during wet months, dispersing across the forest floor up to several meters away from the stream channel. In both species, we investigated genomic features, for example, genome size and dynamics of transposable elements across Limnephilidae. We also explored potential molecular adaptations of silk to terrestrial versus aquatic environments. Characterization of the major silk gene,h‐fibroin, of both species, as well as elemental analysis of silk ofPhilocasca rivularis, did not reveal molecular differences compared with silk of aquatic caddisfly species, potentially owing to the humid environments that both species inhabit. The new genomes form key resources for future genomic research on insect evolution, particularly related to habitat diversification and aquatic‐terrestrial transitions.
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De Novo Whole Genome Assemblies of Unusual Case‐Making Caddisflies (Trichoptera) Highlight Genomic Convergence in the Composition of the Major Silk Gene ( h‐fibroin )
ABSTRACT Trichoptera (caddisflies) is one of the most species‐rich orders of aquatic insects. Species of caddisflies cover a broad ecological diversity as exemplified by various uses of underwater silk secretions. Diversity of silk use generally aligns with the evolution of major caddisfly lineages, specifically at the subordinal level: Annulipalpia (retreat makers) and Integripalpia (cocoon and tube‐case makers). However, silk use within suborders differs for a few exceptional species in these clades. In this study, we provide the first whole genome assemblies and annotations for two unusual Integripalpia species:Limnocentropus insolitus, whose hard tube‐case is anchored to boulders by a rigid, elongated silken stalk, andPhryganopsyche brunneawhich builds a “floppy” cylindrical case that lacks the typical robustness of tube‐cases. Its texture rather resembles that of the flexible retreats built by Annulipalpia. Using the two high‐quality genome assemblies, we identified and annotated the major silk gene,h‐fibroin, and compared its amino acid composition across various groups, including retreat, cocoon, and tube‐case makers. Our phylogenetic analysis confirmed the phylogenetic position of the two species in the tube‐case‐making clade. The major silk gene ofL. insolitusshows a similar amino acid composition to other tube‐case‐making species. In contrast, the amino acid composition ofP. brunnearesembles that of retreat‐making species, in particular with regard to the high content of proline. This is consistent with the hypothesis that proline could be linked to enhanced extensibility of silk fibers. Taken together, our results underscore the role of silk genes in shaping the evolutionary ecology of retreat‐ and tube‐case‐making in caddisflies.
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- Award ID(s):
- 2217155
- PAR ID:
- 10616045
- Publisher / Repository:
- Journal of Experimental Zoology B: Molecular and Developmental Evolution
- Date Published:
- Journal Name:
- Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
- ISSN:
- 1552-5007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/jez.b.23301
