Publications by authors named "Thomas Parchman"

Article Synopsis
  • Understanding the evolution of genomic variation is essential for creating effective conservation strategies for threatened species, focusing on connectivity, demographic changes, and environmental adaptation.
  • The study analyzed genomic variation in Fraxinus latifolia, a riparian tree facing threats from the invasive emerald ash borer, by sequencing over 1000 individuals from 61 populations.
  • Results showed strong population structure and low genetic diversity, suggesting that this patchy distribution could hinder the species' long-term evolutionary potential, underscoring the importance of conserving genomic diversity for future restoration efforts.
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The extent to which evolution is repeatable remains debated. Here, we study changes over time in the frequency of cryptic color-pattern morphs in 10 replicate long-term field studies of a stick insect, each spanning at least a decade (across 30 years of total data). We find predictable "up-and-down" fluctuations in stripe frequency in all populations, representing repeatable evolutionary dynamics based on standing genetic variation.

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Declines in biodiversity generated by anthropogenic stressors at both species and population levels can alter emergent processes instrumental to ecosystem function and resilience. As such, understanding the role of biodiversity in ecosystem function and its response to climate perturbation is increasingly important, especially in tropical systems where responses to changes in biodiversity are less predictable and more challenging to assess experimentally. Using large-scale transplant experiments conducted at five neotropical sites, we documented the impacts of changes in intraspecific and interspecific plant richness in the genus on insect herbivory, insect richness, and ecosystem resilience to perturbations in water availability.

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Widely distributed plants of western North America experience divergent selection across environmental gradients, have complex histories shaped by biogeographic barriers and distributional shifts and often illustrate continuums of reproductive isolation. Rubber rabbitbrush (Ericameria nauseosa) is a foundational shrub species that occurs across diverse environments of western North America. Its remarkable phenotypic diversity is currently ascribed to two subspecies-Ericameria nauseosa nauseosa and Ericameria nauseosa consimilis-and 22 named varieties.

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Genome re-arrangements such as chromosomal inversions are often involved in adaptation. As such, they experience natural selection, which can erode genetic variation. Thus, whether and how inversions can remain polymorphic for extended periods of time remains debated.

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A history of species co-occurrence in plant communities is hypothesized to lead to greater niche differentiation, more efficient resource partitioning, and more productive, resistant communities as a result of evolution in response to biotic interactions. A similar question can be asked of co-occurring populations: do individual species or community responses differ when communities are founded with plants sharing a history of population co-occurrence (sympatric) or originating from different locations (allopatric)? Using shrub, grass, and forb species from six locations in the western Great Basin, North America, we compared establishment, productivity, reproduction, phenology, and resistance to invaders for experimental communities with either sympatric or allopatric population associations. Each community type was planted with six taxa in outdoor mesocosms, measured over three growing seasons, and invaded with the annual grass Bromus tectorum in the final season.

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Article Synopsis
  • Hybridization significantly impacts the evolution of multicellular eukaryotes, but the influence of ecological factors on this process is not well understood.
  • A 3-year study of hybridization between Bryant's woodrat and desert woodrat in Whitewater, CA, revealed that about 40% of individuals have mixed ancestry due to backcrossing.
  • Interestingly, the survival rates of hybrids were similar to the more abundant parental species, while the less common parental species had lower survival rates, suggesting hybridization is limited by the abundance of desert woodrat rather than by negative selection against the hybrids.
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Article Synopsis
  • The microbiome significantly influences an organism's traits and is shaped by ecological and evolutionary factors.
  • In a study of a hybrid mammal species, researchers found that while the host's genetic background primarily determines gut microbiome composition, habitat affects dietary choices, which in turn influences microbial diversity.
  • Increased dietary diversity is linked to greater stability in gut microbiomes, especially in the more adaptable species, suggesting that host ancestry and diet collaboratively impact microbiome characteristics and the overall adaptability of the organism.
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Understanding the contribution of neutral and adaptive evolutionary processes to population differentiation is often necessary for better informed management and conservation of rare species. In this study, we focused on Pinus torreyana Parry (Torrey pine), one of the world's rarest pines, endemic to one island and one mainland population in California. Small population size, low genetic diversity, and susceptibility to abiotic and biotic stresses suggest Torrey pine may benefit from interpopulation genetic rescue to preserve the species' evolutionary potential.

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Identifying the genetic basis of adaptation is a central goal of evolutionary biology. However, identifying genes and mutations affecting fitness remains challenging because a large number of traits and variants can influence fitness. Selected phenotypes can also be difficult to know , complicating top-down genetic approaches for trait mapping that involve crosses or genome-wide association studies.

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The genomic architecture underlying the origins and maintenance of biodiversity is an increasingly accessible feature of species, due in large part to third-generation sequencing and novel analytical toolsets. Applying these techniques to woodrats (Neotoma spp.) provides a unique opportunity to study how herbivores respond to environmental change.

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Trait-environment correlations can arise from local adaptation and can identify genetically and environmentally appropriate seeds for restoration projects. However, anthropogenic changes can disrupt the relationships between traits and fitness. Finding the best seed sources for restoration may rely on describing plant traits adaptive in disturbed and invaded environments, recognizing that while traits may differ among species and functional groups, there may be similarities in the strategies that increase seedling establishment.

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The spatial structure of genomic and phenotypic variation across populations reflects historical and demographic processes as well as evolution via natural selection. Characterizing such variation can provide an important perspective for understanding the evolutionary consequences of changing climate and for guiding ecological restoration. While evidence for local adaptation has been traditionally evaluated using phenotypic data, modern methods for generating and analyzing landscape genomic data can directly quantify local adaptation by associating allelic variation with environmental variation.

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Garter snakes (Thamnophis) are a successful group of natricines endemic to North America. They have become important natural models for ecological and evolutionary research, yet prior efforts to resolve phylogenetic relationships have resulted in conflicting topologies and weak support for certain relationships. Here, we use genomic data generated with a reduced representation double-digest RADseq approach to reassess evolutionary relationships across Thamnophis.

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Population genetic analyses can evaluate how evolutionary processes shape diversity and inform conservation and management of imperiled species. Taimen (Hucho taimen), the world's largest freshwater salmonid, is threatened, endangered, or extirpated across much of its range due to anthropogenic activity including overfishing and habitat degradation. We generated genetic data using high throughput sequencing of reduced representation libraries for taimen from multiple drainages in Mongolia and Russia.

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Foundational hypotheses addressing plant-insect codiversification and plant defense theory typically assume a macroevolutionary pattern whereby closely related plants have similar chemical profiles. However, numerous studies have documented variation in the degree of phytochemical trait lability, raising the possibility that phytochemical evolution is more nuanced than initially assumed. We utilize proton nuclear magnetic resonance (H NMR) data, chemical classification, and double digest restriction-site associated DNA sequencing (ddRADseq) to resolve evolutionary relationships and characterize the evolution of secondary chemistry in the Neotropical plant clade Radula (Piper; Piperaceae).

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Article Synopsis
  • The study investigates how genomes of two distinct species of woodrats, the desert woodrat and Bryant's woodrat, interact at a hybrid zone in Southern California after developing separately (allopatric divergence).
  • Researchers collected genetic data from 353 individuals to analyze patterns of ancestry and introgression (gene flow between species), finding that hybrids were rare and mostly consisted of a few first-generation hybrids and many backcrosses.
  • The findings revealed that while many genomic regions showed introgression, this did not correlate with levels of divergence, suggesting that factors like genetic drift may play a significant role in shaping genetic interactions at the hybrid zone rather than just adaptation to different diets.
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Endophytes are microbes that live, for at least a portion of their life history, within plant tissues. Endophyte assemblages are often composed of a few abundant taxa and many infrequently observed, low-biomass taxa that are, in a word, rare. The ways in which most endophytes affect host phenotype are unknown; however, certain dominant endophytes can influence plants in ecologically meaningful ways-including by affecting growth and immune system functioning.

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Background: Distributional responses by alpine taxa to repeated, glacial-interglacial cycles throughout the last two million years have significantly influenced the spatial genetic structure of populations. These effects have been exacerbated for the American pika (Ochotona princeps), a small alpine lagomorph constrained by thermal sensitivity and a limited dispersal capacity. As a species of conservation concern, long-term lack of gene flow has important consequences for landscape genetic structure and levels of diversity within populations.

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Non-random mating among individuals can lead to spatial clustering of genetically similar individuals and population stratification. This deviation from panmixia is commonly observed in natural populations. Consequently, individuals can have parentage in single populations or involving hybridization between differentiated populations.

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Article Synopsis
  • Classical theory posits that parasites should be better adapted and have higher fitness in host populations that they co-occur with (sympatric) compared to those that live separately (allopatric).
  • The study examined two trematode species, Paralechriorchis syntomentera and Ribeiroia ondatrae, to see how their local adaptation to amphibian hosts varied, with findings indicating that increased geographic and genetic distances negatively affected infection success for the snake-dispersed P. syntomentera, while the avian-dispersed R. ondatrae showed no such relationship.
  • Results suggest that higher dispersal capabilities of parasites may hinder their ability to adapt to specific local host populations, as indicated by noticeable genetic differences in P.
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Premise: Understanding edaphic specialization is crucial for conserving rare plants that may need relocation due to habitat loss. Focusing on Eriogonum crosbyae, a rare soil specialist in the Great Basin of the United States, we asked how site-level variation among volcanic soil outcrops affected plant growth and population distribution.

Methods: We measured emergence, survival, size, and biomass allocation of E.

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Juniper (Juniperus) is an ecologically important conifer genus of the Northern Hemisphere, the members of which are often foundational tree species of arid regions. The serrate leaf margin clade is native to topologically variable regions in North America, where hybridization has likely played a prominent role in their diversification. Here we use a reduced-representation sequencing approach (ddRADseq) to generate a phylogenomic data set for 68 accessions representing all 22 species in the serrate leaf margin clade, as well as a number of close and distant relatives, to improve understanding of diversification in this group.

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Article Synopsis
  • Scientists are studying bird genomes to learn more about their diversity and evolution, analyzing 363 bird genomes from nearly all bird families for a big project called Bird 10,000 Genomes (B10K).
  • By using advanced methods, they can compare DNA more effectively, finding new patterns and understanding how different bird species are related.
  • This research helps improve our understanding of how birds evolve and can also aid in protecting them in the future.
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