Publication Date

2020

First Advisor

Jesse Bellemare

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Biological Sciences

Keywords

Jeffersonia, Climate change, Population genetics, Post-glacial migration, Range shift, Last Glacial Maximum, Conservation, Seed dispersal, Genetic diversity, Conservation genetics, Glacial refugia, Phylogeography, Forest herb

Abstract

The Wisconsinin glaciation culminating in the Last Glacial Maximum was a particularly consequential climate event in the biogeographical and genetic history of plant species around the North Temperate Zone. While paleoecological evidence provides a general picture of species range shifts during and after the LGM, detailed reconstruction of the migration and demographic history of individual species requires the use of phylogenetic data and phylogeographical approaches. In this study, the phylogeography of an eastern North American forest herb species, Jeffersonia diphylla (Berberidaceae), was investigated using chloroplast DNA markers to investigate its history of range fragmentation and migration in response to past glaciation and subsequent climate warming in the Holocene. Chloroplast DNA (cpDNA) sequence data from the trnL-trnF region was sequenced to identify polymorphisms and explore relationships among populations across the species’ range in the eastern United States. Four cpDNA haplotypes and 16 single nucleotide polymorphism were identified in individuals from 20 populations sampled across the native range of the species from Alabama to Minnesota to New York. While the southern margin of the species’ range in Georgia and Alabama was found to harbors 3 endemic haplotypes, all populations north of this southern range edge were monomorphic at the cpDNA locus sequenced. These data suggest that populations at the species’ southernmost range edge represent distinct relictual or refugial populations that have not contributed to the species’ northward migration and recolonization of the eastern United States, while populations north of this distinct region are genetically-related and might be descended from a single refugial population(s) that persisted during the Pleistocene somewhere in the species’ current range in Tennessee and/or Kentucky. Genetic data of this nature will be valuable for planning conservation of the species in the future, as genetically-distinct southern range edge populations might include components of genetic diversity not represented in central and northern populations, and could merit special conservation efforts if they show signs of decline due to climate change.

Rights

2020 Xufen Liu. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

Comments

24 pages : color maps. Includes bibliographical references (pages 19-24)

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