Abstract Background Calcareous outcrops, rocky areas composed of calcium carbonate (CaCO 3 ), often host a diverse, specialized, and threatened biomineralizing fauna. Despite the repeated evolution of physiological and morphological adaptations to colonize these mineral rich substrates, there is a lack of genomic resources for calcareous rock endemic species. This has hampered our ability to understand the genomic mechanisms underlying calcareous rock specialization and manage these threatened species. Results Here, we present a new draft genome assembly of the threatened limestone endemic land snail Oreohelix idahoensis and genome skim data for two other Oreohelix species. The O. idahoensis genome assembly (scaffold N50: 404.19 kb; 86.6% BUSCO genes) is the largest (~ 5.4 Gb) and most repetitive mollusc genome assembled to date (85.74% assembly size). The repetitive landscape was unusually dominated by an expansion of long terminal repeat (LTR) transposable elements (57.73% assembly size) which have shaped the evolution genome size, gene composition through retrotransposition of host genes, and ectopic recombination. Genome skims revealed repeat content is more than 2–3 fold higher in limestone endemic O. idahoensis compared to non-calcareous Oreohelix species. Gene family size analysis revealed stress and biomineralization genes have expanded significantly in the O. idahoensis genome . Conclusions Hundreds of threatened land snail species are endemic to calcareous rock regions but there are very few genomic resources available to guide their conservation or determine the genomic architecture underlying CaCO 3 resource specialization. Our study provides one of the first high quality draft genomes of a calcareous rock endemic land snail which will serve as a foundation for the conservation genomics of this threatened species and for other groups. The high proportion and activity of LTRs in the O. idahoensis genome is unprecedented in molluscan genomics and sheds new light how transposable element content can vary across molluscs. The genomic resources reported here will enable further studies of the genomic mechanisms underlying calcareous rock specialization and the evolution of transposable element content across molluscs.
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Geology constrains biomineralization expression and functional trait distribution in the Mountainsnails
Geographic variation in metabolic resources necessary for functional trait expression can set limits on species distributions. For species that need to produce and maintain biomineralized traits for survival, spatial variation in mineral macronutrients may constrain species distributions by limiting the expression of biomineralized traits. Here, we examine whether
Western United States.
We used random forest classification models at multiple spatial resolutions to evaluate the contribution of topographic, vegetation, climate, and geologic variables in predicting the presence of heavily biomineralized shell ornaments across the range of
Distance to CaCO3rock was the most important variable in all models and closer proximity to CaCO3rock was associated with greater probability of local ornamentation classification. Pairwise comparisons of14C/12C ratios in closely occurring ornamented vs. smooth population pairs revealed ornamented forms incorporate greater CaCO3rock carbon than smooth forms. Ornamented types measured in this study were generally heavier and required greater peak force for fracture than smooth forms, except when comparing ornamented forms to smooth forms sampled from CaCO3rock.
Biomineralization expression, species distribution, and trait function appear to be constrained by mineral supply in a highly diverse group of land snails. This trait‐environment relationship provides a basis for future investigations of CaCO3macronutrient constraints on shell form and species distribution in other terrestrial molluscs and has a direct impact on the management of
- Award ID(s):
- 1751157
- PAR ID:
- 10472711
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 50
- Issue:
- 12
- ISSN:
- 0305-0270
- Format(s):
- Medium: X Size: p. 2122-2134
- Size(s):
- p. 2122-2134
- Sponsoring Org:
- National Science Foundation
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