Using Museomics to Investigate Extinction and Decline in British Butterflies

Globally, plant and animal species are declining due to land use changes, habitat destruction, and climate change. Conservation of endangered species is essential for their persistence, and to effectively conserve species we have to understand their genetic diversity. Conservation of insect species is often difficult as not only do we not have accurate conservation assessment data for many species, studies on metrics of genomic erosion in insects are scarce. In the Natural History Museum in London and the Oxford University Museum of Natural History, there are over 69.5 million specimens across their botanical, zoological and entomological collections. Museum specimens have the potential to be used as a conservation tool for many species - to provide a baseline for population genetic diversity, to investigate signatures of decline in different species, and to determine changes in the effective population size of species through time. This information can be used not only to understand the extinction process but also aid with species reintroductions, relocations and monitoring of insect populations. This thesis investigates genetic erosion (genome-wide heterozygosity, runs-of-homozygosity, and genetic load) in three species of butterfly with contrasting demographic histories: the Black-veined White (Aporia crataegi), a locally extinct species; the Wood White (Leptidea sinapis), a declining butterfly species; and the Common Blue (Polyommatus icarus), a species with stable demographic trends. This was achieved using whole genome shotgun sequencing of both historical museum samples and modern samples, and using these sequences for population genomic analysis. As A. crataegi drew closer to extinction in Great Britain, it showed marked increases in inbreeding compared to continental European specimens, with signs of both ancestral and ‘recent’ (i.e. before extirpation) inbreeding. Genetic load analysis indicated an accumulation of putatively mildly and weakly deleterious variants. Both results are consistent with long-term gradual declines in population. In contrast, British P. icarus shows no significant increase in inbreeding or genetic load compared to European specimens. Current British populations of L. sinapis showed increases in inbreeding compared to both historical British and continental specimens. Genetic load analyses showed an accumulation of mildly deleterious variants compared to historical British specimens, and increased strongly and potentially deleterious variants compared to continental specimens. Although the species has seen increases in distribution and range in recent years due to increased conservation effort, genomic erosion in modern British populations is still severe. Results of this thesis support that measures of inbreeding and accumulation of deleterious mutations can be informative indicators of invertebrate species in decline, and adds to the literature regarding conservation utility of museum specimens.

Grantor dc:publisher

Oxford Brookes University

Author dc:creator

• Whitla, Rebecca

Contributors dc:contributor

• Arif, Saad
• Breuker, Casper

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/s2w3-3853

OAI identifier oai:identifier

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