Evolutionary lineages and the diversity of New Zealand true whelks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Evolutionary Biology at Massey University, Manawatū Campus, New Zealand
Biological evolution fundamentally operates according to the basic principles of variation, heritability and selection, but it generates the astounding complexity of nature. One of the greatest challenges for evolutionary study is the interpretation of this diversity, and the ability to identify and communicate the underlying biological changes that are responsible. In this thesis, I consider the identification of evolutionary lineages using molecular and morphological data. I address the problem of confusing terminology regarding the evolutionary process, focussing on the concepts of anagenesis and cladogenesis, and the challenge of genetic introgression for taxonomic classification.
I investigate molecular and morphological variation in New Zealand true whelks. There are many species of true whelks described, however their taxonomy is mostly restricted to the traditional examination of shell traits. Evolutionary relationships of true whelks inferred from DNA sequences indicate that neither New Zealand nor Southern Hemisphere true whelks are monophyletic, contradicting taxonomic hypotheses and expectations of geographic isolation. I focus on the siphon whelk genus Penion Fischer, 1884, a diverse genus with extant species restricted to New Zealand and Australia. All extant species are genetically sampled for phylogenetic and allelic variation analysis. A monophyletic clade is identified for New Zealand Penion. Results suggest the existence of a new species and indicate evolutionary relationships for some taxa not captured by the taxonomy.
Shell shape and size are studied using geometric morphometric analyses, confirming that these traits can distinguish taxa divided by deep evolutionary splits under both informed and naïve analyses. Morphometric variation is hierarchical, with closely related taxa being grouped together within large datasets including samples from multiple evolutionary lineages. Overall, morphometric results show reasonably strong concordance with molecular evidence.
Evolutionary lineages in the fossil record are investigated using morphometric analysis within the context of previous molecular and morphometric findings. Results assist with the identification of fossils from two localities and suggest that multiple extinct species of Penion are misclassified. Variation in morphometric traits through time is fitted to models of evolutionary change, and results indicate that the identification and selection of a lineage has a significant impact upon those results.
anagenesis; benthic; Buccinidae; Buccinulidae; Buccinioidea; Caenogastropoda; cladogenesis; deep sea; dispersal; developmental biology; endemism; evolution; evolutionary biology; evolutionary lineage; evolutionary rate; divergence; diversity; fossil; gastropod; geometric morphometrics; high-throughput sequencing; hybridisation; introgression; lineage split; marine snail; mitochondrial DNA; mollusc; monophyly; morphology; Neogastropoda; next-generation sequencing; nuclear DNA; palaeontology; paraphyly; phylogenetics; RADseq; ribosomal DNA; sexual dimorphism; shell; siphon whelk; snail; speciation; species; systematics; taxonomy; whelk; zoology
Chapters in this thesis have been published as:
Marshall, B.A., Hills, S.F.K., & Vaux, F. (2018). A new species of Penion P. Fischer, 1884 from northern New Zealand (Mollusca: Neogastropoda: Buccinoidea). Molluscan Research, 38(4), 238-242. https://doi-org.ezproxy.massey.ac.nz/10.1080/13235818.2017.1420398
Vaux, F., Hills, S.F.K., Marshall, B.A., Trewick, S.A., & Morgan-Richards, M. (2018). Genome statistics and phylogenetic reconstructions for Southern Hemisphere whelks (Gastropoda: Buccinulidae). Data in Brief, 16, 172-181. https://doi-org.ezproxy.massey.ac.nz/10.1016/j.dib.2017.11.021
Vaux, F., Hills, S.F.K., Marshall, B.A., Trewick, S.A., & Morgan-Richards, M. (2017). A phylogeny of Southern Hemisphere whelks (Gastropoda: Buccinulidae) and concordance with the fossil record. Molecular Phylogenetics and Evolution, 114, 367-381. https://doi-org.ezproxy.massey.ac.nz/10.1016/j.ympev.2017.06.018
Vaux, F., Crampton, J.S., Marshall, B.A., Trewick, S.A., & Morgan-Richards, M. (2017). Geometric morphometric analysis reveals that the shells of male and female siphon whelks Penion chathamensis are the same size and shape. Molluscan Research, 37(3), 194-201. https://doi-org.ezproxy.massey.ac.nz/10.1080/13235818.2017.1279474
Vaux, F., Trewick, S.A., & Morgan-Richards, M. (2017). Speciation through the looking-glass. Biological Journal of the Linnean Society, 120, 480-488.
Vaux, F., Trewick, S.A., & Morgan-Richards, M. (2016). Lineages, splits and divergence challenge whether the terms anagenesis and cladogenesis are necessary. Biological Journal of the Linnean Society, 117, 165–176.