CONSERVATION GENETICS OF A RARE ENDEMIC ALPINE FLOWER, POTENTILLA ROBBINSIANA, IN THE WHITE MOUNTAINS OF NEW HAMPSHIRE
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Authors
VOLLMER, HANNAH
Date
2024-05
Type
Thesis
Language
Keywords
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Abstract
ABSTRACT
Alpine zones in the White Mountains of New Hampshire are small, isolated ecosystems
that are considered relicts of the widespread tundra following the last ice age. The
diminutive flowering plant Potentilla robbinsiana (dwarf cinquefoil) is endemic to a
hectare of alpine habitat in New Hampshire’s White Mountains and is hundreds of
kilometers from its closest kin, the common circumpolar P. hyparctica. After a century
of unchecked botanical collection and recreational impacts, P. robbinsiana approached
extinction, but habitat closure, transplanting, and hiker education helped make this plant
an Endangered Species Act success story. Odd-number polyploidy, cytological and
pollination studies, and isozymes support the assumption that P. robbinsiana is apomictic
and genetically uniform. We set out to determine how much genetic diversity, if any, is
present among P. robbinsiana plants (both extant and preserved as herbarium specimens)
and to determine whether this species is genetically distinct from P. hyparctica. We
conducted ddRADseq (double digest restriction site-associated DNA sequencing) on 144
freshly collected P. robbinsiana samples, along with historic herbarium samples of P.
robbinsiana (n=32), P. hyparctica (n=32), and two Potentilla outgroup species, mapping
2.1% of our reads to Fragaria vesca nuclear, chloroplast, and mitochondrial genomes.
We found evidence of diversity in P. robbinsiana with 306 allelic sites across 57 loci.
Observed heterozygosity in the nuclear genome was low suggesting subpopulations have
deviated from Hardy-Weinberg Equilibrium. Nuclear and organellar diversity estimates
show that the largest population and one of the two transplant populations have highest
diversity. This transplant population is most representative of the species’ diversity as a
whole as shown by F-statistics. Some alleles found in historic herbarium plants were not
present in extant plants, but the number of unique alleles found in a transplant population
far exceeded these. Our current data do not support P. robbinsiana and P. hyparctica as
distinct, monophyletic species, but our study species is more genetically diverse than
previously thought and we recommend that future conservation plans should reflect this.
Further phylogenetic work should attempt to refine relationships between P. robbinsiana
and P. hyparctica. Transplantation attempts should use seed sourced from multiple
locations so as to better represent the species’ genetic variation.