Lichen Conservation in Eastern North America: Population Genomics, Climate Change, and Translocations

Conservation biology is a scientific discipline that draws on methods from diverse fields to address specific conservation concerns and inform conservation actions. This field is overwhelmingly focused on charismatic animals and vascular plants, often ignoring other diverse and ecologically important groups. This trend is slowly changing in some ways; for example, increasing number of fungal species are being added to the IUCN Red-List. However, a strong taxonomic bias still exists. Here I contribute four research chapters to further the conservation of lichens, one group of frequently overlooked organisms. I address specific conservation concerns in eastern North America using modern methods. The results of these studies provide insight into lichen conservation in each situation, implications for the broader ecosystems within the study regions, and advancement of methods for the study of lichen conservation and biology. The first research chapter (Chapter 2) is a population genomics study based on whole genome shotgun sequencing of Cetradonia linearis, an endangered, lichenized fungus. These data were used to 1) assemble and annotate a reference genome, 2) characterize the mating system, 3) test for isolation by distance (IBD) and isolation by environment (IBE), and 4) investigate the biogeographic history of the species. Approximately 70% of the genome (19.5 Mb) was assembled. Using this assembly, only a single mating type was located, suggesting the species could be unisexual. There was strong evidence for both low rates of recombination and for Isolation by Distance, but no evidence for Isolation by Environment. The hypothesis that C. linearis had a larger range during the last glacial maximum, especially in the southern portion of its current extent, was supported by Hindcast species distribution models and the spatial distribution of genetic diversity. Given the findings here, it is recommended that C. linearis remain protected by the U.S. Endangered Species Act and listed as Vulnerable on the International Union for the Conservation of Nature Red-List. The third chapter is an estimation of the impacts of climate change on high-elevation, endemic lichens in the southern Appalachians, a global diversity hotspot for many groups, including lichens. Extensive field surveys in the high elevations of the region were carried out to accurately document the current distributions of eight narrowly endemic species. These data were compared with herbarium records, and species distribution modeling was used to predict how much climatically suitable area will remain within, and north of, the current range of the target species at multiple time points and climate change scenarios. Fieldwork showed that target species ranged from extremely rare to locally abundant and models predicted average losses of suitable area within the current distribution of species ranging from 93.8 to 99.7%. The results indicate that climate change poses a significant threat to high-elevation lichens, and illustrates the application of current modeling techniques for rare, montane species. In the fourth chapter, a dataset of \u3e13,000 occurrence records for lichens in the Mid-Atlantic Coastal Plain (MACP) of eastern North America was used to model distributions of 193 species. The resulting models were used to quantify the amount of each species’ distribution that is occupied by unsuitable land use types, along with the potential area that will be lost to sea-level rise (SLR). These analyses showed that species have likely already lost an average of 32% of their distributional area to development and agriculture, and are predicted to lose an average of 12.4 and 33.7% of their distributional area with one foot (~0.3 m) and six feet (~1.8 m) of SLR, respectively. Functional and taxonomic groups were compared to identify specific effects of SLR. Species reproducing with symbiotic propagules were found to have significantly larger distributions than species that reproduce sexually with fungal spores alone, and the sexually reproducing species were predicted to lose greater distributional area to SLR. Cladonia species occupy significantly less area in the MACP than Parmotrema species and were predicted to lose more of their distributions to SLR. Patterns of total species diversity showed that the area with the highest diversity is the Dare Peninsula in North Carolina, which was also predicted to lose the most land area to SLR. The workflow established here is flexible and applicable to estimating SLR impacts worldwide and can provide essential insights for local conservation planning. The fifth chapter describes the results of three experiments conducted to test new and established methods for lichen transplantation. First, small fragments of Graphis sterlingiana, Hypotrachyna virginica, and Lepraria lanata were placed on medical gauze attached to each of the species’ most common substrate to test the feasibility of transplanting narrowly endemic species. Second, burlap, cheesecloth, medical gauze, and a plastic air filter were directly compared for their use as artificial transplant substrates with Lepraria finkii as the test lichen. Third, transplants of Usnea angulata were established to test its amenability to transplantation via hanging fragments on monofilament. The first two experiments were established on Roan Mountain, North Carolina and the third experiment at Highlands Biological Station, North Carolina. In the first two experiments medical gauze did not withstand local weather conditions and nearly all pieces fell from the trees within 6 months. The plastic air filter and burlap performed best as artificial substrates for transplants, with a 100% and 80% success rate, respectively. Cheesecloth remained attached to the trees, but only 20% of lichen fragments remained attached to the substrate after one year. In the third experiment U. angulata grew 3.5 ± 1.4 cm in 5 months, exceeding previously reported growth rates for this species. These results advance methods for conservation-focused lichen transplants, and expand established methods to a new region and new species