The impact of climate change on alpine plant and insect diversity in the Rocky Mountains

Authors(s): A. Martin

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Publication Date: 0000-00-00

Type: annual report

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Abstract: Objectives The goals of this study are to determine the impact of climate change on the biological diversity of alpine plants and insects in the Rocky Mountains and the degree to which national parks may conserve this diversity. These objectives will be accomplished by inferring the shared phylogeographic history of alpine plants and insects through genetic analysis of the geographic structure and history of populations of plant-insect associations throughout the Rockies. This analysis will not only reveal how historic climate change affected population structure, but also permits the identification of national parks that harbor relatively high levels of diversity. First, it must be determined whether independent taxa share a common history. The null hypothesis is that the phylogeographic history of each species is unique. The null predicts no concordance in the timing of diversification events or topography among area cladograms for the different taxa. The alternative hypothesis is that independent taxa share a common history and predicts that co-distributed species will have similar area cladograms. The shared history of taxa will be used to estimate how extrinsic factors contributed to the distribution and diversity of these co-distributed organisms. The null hypothesis is that there is no geographic structure to the distribution of diversity. This hypothesis predicts that geographic lineages are distributed randomly on a phylogenetic tree. Analysis of the historic shifts in the distributions of alpine habitats suggests an alternative hypothesis that the southern Rockies served as a refuge and harbored species for longer periods of time than northern portions of the modern range. This hypothesis predicts that lineages in northern populations will be more recently derived than southern populations and only a fraction of the diversity present in the south will be represented in the north. The Study Taxa In order to acquire a representative sample of the alpine community and incorporate interspecific interactions into the examination of how climate change affected biological diversity, this study will analyze the phylogenetic histories of three specialized plant-insect interactions. These associations 1) range from the southern Rockies where the effects of habitat fragmentation due to climate change are most severe to northern areas that were completely covered by Pleistocene ice sheets, 2) are predominantly influenced by climate, 3) are abundant and play integral roles in the alpine community, 4) are relatively easy to find and collect, and 5) include taxa for which molecular techniques are well developed. Herbaceous plants and insects have been shown to be excellent bio-indicators of climate and environmental change (Ford 1982; Boggs and Murphy 1997). Two pairs of alpine plant-butterfly associations will be used to estimate the geographic distribution of biological diversity. The study organisms are 1) the yellow stonecrop Sedum lanceolatum (Crassulaceae) and the Rocky Mountain Apollo Parnassius phoebus (Papilionidae) and 2) the alpine clover Trifolium dasyphyllum (Fabaceae) and Mead's sulfur Colias meadii (Pieridae). Though the associations are relatively specific, variation in host use occurs throughout each species' range. Findings and Status Study Sites and Collection Specimens of Sedum lanceolatum, Parnassius phoebus, Trifolium dasyphyllum, and Colias meadii were collected from 22 alpine sites throughout the Rocky Mountains, including Glacier National Park, the Greater Yellowstone Ecosystem, Rocky Mountain National Park, and the southern Rockies of Colorado. In Glacier National Park specimens were collected at 1) Numa Pk., 2) Gunsight Mtn., 3) Triple Divide Pk., and 4) Dawson Pass. In the Greater Yellowstone Ecosystem, the alpine sites in Yellowstone National Park were on 5) Amethyst Pk and 6) Mt. Washburn, while in Grand Teton National Park specimens were collected from 7) Moose Mtn. and 8) Static Pk. Organisms were collected from alpine tundra in Rocky Mountain National Park on 9) Sundance Mtn. and 10) Long's Pk. Specimens were also collected from eastern slope sites in Idaho including 11) Hyndman Pk and 12) Borah Pk and from potential southern refugia sites in Colorado including: 13) the American Basin, 14) San Luis Pk, 15) Humboldt Pk, 16) Iron Nipple, 17) Mt. Democrat, 18) Mt. Elbert, 19) Mt. Shavano, 20) Quandary Pk, 21) Maroon Pass, and 22) Pike's Pk. In order to obtain an accurate estimate of genetic variation and thus population history, it is necessary to sample DNA from many individuals of each population. Twenty to thirty specimens of each species were collected at each site. Sites were accessed on foot. Butterflies were collected with a net and stored in glassine envelopes. To preserve the organisms and their natural environment, only parts of plants were collected. Leaves were sampled by hand from approximately thirty individuals of each species and stored in plastic bags. Specimens were carried out of the field, transported on ice, and stored at -80oC at the University of Colorado, Boulder. Methods for Assessing Evolutionary Histories and Diversity Nuclear as well as mitochondrial (mtDNA, insect) or chloroplast (cpDNA, plant) DNA was sequenced, in order to develop phylogenetic trees. DNA was extracted from the insects and amplified with specific primers for the mitochondrial Cytochrome Oxidase I. DNA was extracted from the plants and amplified with specific primers for the chloroplast intergenic spacers between trnL and trnF and between trnL and trnT. Phylogenetic trees and nested cladeswere generated from DNA sequence polymorphisms to infer hypothetical evolutionary relationships among haplotypes (unique genetic sequences) within each species. Results to Date The strength of the historic signal between the herbivorous insect and its host-plant suggest that biotic factors may be responsible for evolution in these organisms, and that there is a strong potential for co-evolution. Importantly, these findings point to ecological and evolutionary stability of the alpine community. Preliminary analysis revealed significant co-divergence of the host plant (Sedum) and the herbivore (Parnassius) based on topology-based tests (using TreeMap).A preliminary nested clade analysis reveals a geographic distinction between southern Colorado and northern haplotypes; however, too few individuals from each population have been sequenced at this juncture for a rigorous geographic analysis of the clades. This pattern is also evident from the plot of genetic variation with latitude. Though only a few individuals from each population have been analyzed, these data agree with the general trend of rapid northward expansion following deglaciation and contrast the findings of other alpine studies.Together, these preliminary findings support the hypothesis that alpine communities persist in southern refugia and northern were re-colonized following glacial retreat.

Keywords: entomology, animal, insect, population, Grand Teton National Park, Moose Mountain, Static Peak, Yellowstone National Park, Greater Yellowstone Ecosystem, Rocky Mountains, plant, food, butterfly, lepidoptera, Rocky Mountain Apollo, Insecta, Parnassius phoebus, Papilionidae, Colias meadii, Pieridae, Mead's sulfur