Molecular systematics of the greater fritillary butterflies (Nymphalidae: Speyeria): reduced representation sequencing, phylogeny, and incipient speciation

• Author / Creator

  Campbell, Erin

• Species delimitation and phylogenetic reconstruction are essential for understanding and categorizing lineage divergences, and ultimately species. Yet, because of the complexities underlying speciation, inferring these patterns and characterizing their sources has been a consistent challenge for systematists. Recent advances in genomics have increased our understanding of how speciation may be influenced by ecology, biology, geography, and demography. However, the expansion of methods for producing genomic data warrants continued assessment to ensure they produce robust systematic inferences. Here, I conceptually and empirically assess the technical compatibility of some of the most commonly-used reduced representation sequencing (RRS) approaches for producing genomic single nucleotide polymorphism (SNP) data for systematic and population genomic inference in non-model taxa. I then apply these RRS approaches to re-assess the molecular systematic relationships of species in the butterfly genus Speyeria Scudder, 1872. These butterflies have a long history of taxonomic instability that is largely due to morphological variability and insufficient taxon sampling in previous systematic studies, which has impeded the assessment of species limits despite growing conservation concern for several taxa.
  In a literature review of studies that describe new RRS techniques, I found that several published methods are only subtly different from one another, and often have convergent technical features despite being published with distinct names. I then empirically assessed the compatibility of two commonly used RRS techniques using several Speyeria species. Despite large intial differences between methods in sequencing depth and coverage, the genotyping consistency between methods was high and improved the recovery of monophyletic clades of Speyeria. In an expanded taxonomic and geographic phylogenetic study of Speyeria, I recovered extensive mito-nuclear discordance between the SNP-based species phylogeny and the mitochondrial COI gene phylogeny, and recovered genomic divergences in two species that likely warrant taxonomic revision. Finally, I re-assessed the species limits in the S. atlantis-hesperis species complex, which has become infamous for its morphological variability. My results uphold S. atlantis (Edwards, 1862) as a species distinct from S. hesperis (Edwards, 1864), and additionally indicate that S. hesperis should be taxonomically recognized as two species.
  This work presents the most geographically comprehensive taxonomic sampling of Speyeria to date, and the first use of genomic SNPs for elucidating the systematics of these enigmatic butterflies. These studies build conceptually on methodological advances to investigate their impact on species detection, and adds to a growing body of research that has demonstrated the utility of genomic SNPs for clarifying long-standing evolutionary problems.

• Subjects / Keywords

  • Entomology
  • Molecular Systematics
  • Population Genomics
  • Speyeria
  • Speciation
  • Lepidoptera
  • ddRAD

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-7039-qj74

• License

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