Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest
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| Language: | English |
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The Ohio State University / OhioLINK
2020
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1586171520981707 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu1586171520981707 |
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NDLTD |
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English |
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Zoology Biology Genetics Phylogeography Species Delimitation Invertebrates Gastropods Machine Learning Pacific Northwest delimitR Prophysaon |
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Zoology Biology Genetics Phylogeography Species Delimitation Invertebrates Gastropods Machine Learning Pacific Northwest delimitR Prophysaon Smith, Megan L. Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| author |
Smith, Megan L. |
| author_facet |
Smith, Megan L. |
| author_sort |
Smith, Megan L. |
| title |
Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| title_short |
Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| title_full |
Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| title_fullStr |
Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| title_full_unstemmed |
Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest |
| title_sort |
investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the pacific northwest |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2020 |
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http://rave.ohiolink.edu/etdc/view?acc_num=osu1586171520981707 |
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AT smithmeganl investigatingdriversofdiversificationinacodistributedcommunityofterrestrialgastropodsfromthepacificnorthwest |
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1719456987073216512 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu15861715209817072021-08-03T07:14:07Z Investigating drivers of diversification in a co-distributed community of terrestrial gastropods from the Pacific Northwest Smith, Megan L. Zoology Biology Genetics Phylogeography Species Delimitation Invertebrates Gastropods Machine Learning Pacific Northwest delimitR Prophysaon My dissertation aims to understand the history of divergence and speciation in terrestrial gastropods from the Pacific Northwest of North America (PNW). Speciation is the driving force behind the diversity on earth, but most of what we know about speciation has been learned from a small number of model systems. In my dissertation, I extend knowledge about how species form in an understudied system, pulmonate gastropods, using genomic and ecological data. Temperate rainforests in the PNW are disjunct and are separated by the arid Columbia Basin (CB). In many rainforest endemics, genetic data suggest that the formation of the CB led to speciation. I set out to test whether this barrier drove speciation in terrestrial gastropods. In Chapter 2, I collected subgenomic data from the robust lancetooth snail (<i>Haplotrema vancouverense</i>) using a restriction-associated-digest (RADseq) technique. While phylogeography has moved away from descriptive work towards model-based approaches in recent years, many approaches perform poorly on large datasets with thousands of loci, or, at least, require that much of the information content of the data is sacrificed. I developed a novel approach that uses Machine Learning to compare hypothesis-driven models using genome-scale data. I applied this framework to <i>H. vancouverense</i> and found evidence of recent dispersal between coastal and inland populations; speciation across the CB was not supported (Smith et al., 2017). In Chapter 3, I expanded this work to several species of taildropper slugs (Genus <i>Prophysaon</i>) with this disjunct distribution. I leveraged an approach described by Espindola et al. (2016) to predict phylogeographic patterns based on taxonomy and environmental data, and predicted that these species would lack deep divergence across the CB. Molecular data and model-based approaches did not support speciation across the CB, and suggested a different distribution of cryptic diversity (Smith et al., 2018). In Chapter 4, I expanded taxonomic sampling by using leaf-litter sampling to collect micro-invertebrates, which were identified via DNA barcoding. This work expanded our knowledge of the region to these small invertebrates, and suggested environmental DNA as a promising step forward to understanding speciation in more taxonomic groups (Smith et al., In Review). Based on the results of Chapter 3, I hypothesized that speciation within taildropper slugs was driven by a complex interplay of neutral and selective forces. To test this idea, in Chapter 5, I collected subgenomic data from <i>Prophysaon andersoni</i>, and found evidence of multiple, undescribed species. However, integrative approaches to taxonomy largely failed, due to disagreements between phenotypic, ecological, and genomic data. This discordance could be attributed, in part, to a lack of fit between the methods used for species delimitation and the processes that led to speciation in our focal taxa. Existing methods for species delimitation were not able to incorporate these population-level processes, so I developed an R-package delimitR that uses Machine Learning to delimit species while considering these processes. I tested this approach on previously published and simulated datasets, and found low error rates (Smith and Carstens 2020). Results from <i>P. andersoni</i> suggested that isolation in separate refugia followed by secondary contact between refugial populations had occurred. This, in turn, led me to hypothesize that reinforcement, or the process by which gene flow leads to selection against inter-population mating and, eventually, speciation, could be important in <i>P. andersoni</i>. I tested predictions of reinforcement using ecological data, and found preliminary support for it as a driving mechanism (Smith and Carstens 2020). Chapter 6 takes a broader look at refugial dynamics in the South Cascades. I used environmental data and Species Distribution Models and found support for decreased habitat suitability and increased habitat fragmentation during the Last Glacial Maximum. I then used subgenomic-scale data from seven taxa and a model-based approach to evaluate scenarios of secondary contact. My results support that in five of the seven taxa for which models were tested, secondary contact is an important process. Parameter estimates place divergence times in the Pleistocene. Overall, results suggest that refugial dynamics contributed to speciation in various ways. In some species, isolation in separate refugia was sufficient to prevent gene flow upon secondary contact, while in others secondary gene flow may lead either to population fusion or to reinforcement and speciation. 2020-10-01 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1586171520981707 http://rave.ohiolink.edu/etdc/view?acc_num=osu1586171520981707 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |