Browsing by Subject "Population Genetics"

Now showing 1 - 3 of 3
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    A history of both clonality and recombination governs the population structure of Alternaria endophyte communities on prairie Dalea
    (2021-10) DeMers, Mara
    Prairie has become one of the most endangered biomes in North America under changing climates engendered by anthropogenic activity. The patterns of diversity we observe of native prairie species in remnant prairie sites are the outcome of both historical and contemporary processes, and understanding these underlying processes will inform the responses of these populations to future environmental changes. The assembly of fungal endophyte communities within plants depends on the complex interactions of fungal taxa, their host plants, and the abiotic environment. Prairie plant communities provide a unique avenue to explore the interplay of biotic and abiotic factors affecting endophyte communities, since the historical distribution of prairies spans a broad range of temperature and precipitation, while the distances between small fragments of contemporary prairie communities may challenge the dispersal capabilities of these otherwise ubiquitous fungi. We sampled foliar fungal endophytes from two native prairie legumes, purple and white prairie clovers (Dalea purpurea and D. candida), in 17 remnant prairie sites across Minnesota in order to evaluate the relative contributions of abiotic factors, host species, and dispersal limitation to the diversity and structure of these communities. We found that similarity of communities was significantly associated with their location along a temperature and precipitation gradient, and we showed a distance-decay relationship that suggests dispersal limitations only over very large spatial scales. Although the effect of host species was small relative to these other factors, the two Dalea species maintained distinct communities within sites where they co-occur. Our results illustrate the capacity of many of these endophyte taxa to disperse over large distances and across heterogeneous biotic and abiotic environments and suggest that the interplay of biotic and abiotic factors maintains high diversity observed in endophyte communities. Our results showed that community composition of endophytic fungi in Dalea spp. varied along a precipitation and temperature gradient, among hosts, and in apparent response to the abundance of Alternaria spp., but left unexplained patterns of genetic variation among the many isolates assigned to Alternaria alternata. We used genotyping-by-sequencing (GBS) to assess population genetic structure of endophytic Alternaria among sampling sites and between host species, and compare levels of recombination and clonality and assess evidence for sexual or parasexual reproduction in these communities. We found cryptic diversity among sequenced samples, as only a subset aligned well to A. alternata reference genomes. Analysis of sequences closely related to reference A. alternata genomes, treated here as a single species, revealed a high level of clonality, and genotypic diversity shared across populations. However, we also detected evidence of recombination events consistent with sexual or parasexual reproduction, as well as two mating types, MAT1-1 and MAT1-2, which were present in roughly equal frequencies in all but one sampled population. Together, the results suggest recent asexual proliferation after rapid colonization of the sampled sites from an ancestral source population. Recombination likely occurred more frequently in the source population, and is now rare.
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    Phenotypic And Molecular Insight Into Genetic Differentiation, Introgression And Selection In Quercus Rubra At A Fine Spatial Scale
    (2021-07) Gomez Quijano, Maria Jose
    The massive scale and cold temperature of Lake Superior creates unique microclimates in coastal terrestrial environments resulting in cooler summers, an extended fall season, warmer winters, and a reduced risk of spring frost. This gives rise to a steep climate gradient from coastal to inland regions that could lead to genetic differentiation among populations. To test this hypothesis, we studied Northern red oak (Quercus rubra L.) to examine phenotypic and molecular differentiation among populations ranging from 1–160 km from the lake shore. In a common garden experiment, we found 30% of germination and juvenile traits differed significantly from expectation. We also used restriction site associated DNA sequencing (RAD-seq) to examine population structure and genomic signatures of selection in these populations. Our results suggest that, in contrast to quantitative traits, Q. rubra populations are not differentiated at neutral genetic markers according to their distance from Lake Superior. However, unexpectedly, we also found evidence of increasing levels of introgression from the closely related species Quercus ellipsoidalis E.J. Hill into Q. rubra as species overlap and population distance from the lake increased. Our scan for selection and environmental association analysis identified one outlier locus in common, and this locus is associated with the precipitation of the wettest month. Overall, despite the lack of molecular population structure, the common garden experiment revealed that Q. rubra populations differ for key phenotypic traits. This, in combination with the genomic scans for selection, suggests the influence of natural selection driven by climate heterogeneity with increasing distance from the lake. Moreover, this is the first study that has jointly leveraged quantitative and molecular genetics to dissect signatures of selection in Q. rubra across a fine geographical scale.
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    Why do coastal seeds fail? Evidence of local adaptation of northern red oak ( Quercus rubra ) in Minnesota coastal forests - Genomics and Geospatial Data
    (2020-04-30) Gomez Quijano, Maria Jose; Gross, Briana, L.; Etterson, Julie, R.; gomez312@d.umn.edu; Gomez Quijano, Maria Jose; University of Minnesota Duluth Gross Lab; University of Minnesota Duluth Etterson Lab
    Genomic and Geospatial data for 30 northern red oak (Quercus rubra) used in a study to identify population structure and investigate poor performance of coastal seeds. We used restriction site associated DNA sequencing (RADseq) of 358 northern red oak (Quercus rubra) leaf tissue samples from trees across the state of Minnesota and 45 northern pin oak (Quercus ellipsoidalis) leaf tissue samples used as outgroups. We used the Minnesota Department of Natural Resources releve data, to identify populations across the state of Minnesota that had presence of Q. rubra trees.