Biology subjects

Patterson, C. M.

Publications and source records attributed to Patterson, C. M..

6 recordsLinked to original sources

bioRxiv2025

A field experiment assessing the roles of drought, herbivory, and local climate on cyanogenesis cline formation and local adaptation in Trifolium repens

Projecting how a population will adapt to environmental changes requires a mechanistic understanding of the specific biotic and abiotic factors that impose selection on that population. In white clover (Trifolium repens), clines in an antiherbivore defense mechanism, hydrogen cyanide (HCN), form via variation in selection imposed by the environment. However, the specific environmental factors that select for or against chemical defense phenotypes in white clover remain unresolved. We performed a field experiment in high and low latitude study sites, with a factorial manipulation of precipitation and herbivory at each site. These factors are hypothesized to be important in driving HCN cline formation, so we investigated their effects on fitness of a white clover F3 recombinant population, segregating for the alleles underlying the HCN chemical defense phenotype. Surprisingly, we found precipitation and herbivory either did not drive differential selection on HCN or its metabolic components, or did not impose selection in a manner consistent with the maintenance of observed HCN clines. Instead, we find that the production only one of the metabolic components of HCN, cyanogenic glycosides, resulted in a fitness advantage, even when lacking the ability to produce HCN. This was most prominent at the northern study site, which is again contrary to expectations. These results suggest additional physiological roles that cyanogenic glycosides may play in adaptation and the evolutionary ecology of white clover. This study highlights the importance of experimental manipulations of environmental factors to understand how selection acts on genes underlying important phenotypic traits, often in unexpected ways.

evolutionary biology↗

bioRxiv2024

Adaptation to climate in the native and introduced ranges of a cosmopolitan plant

Climate change and the global spread of non-native species are two of the most significant threats to biodiversity and ecosystem function. Both these phenomena subject populations to novel conditions, either in space (species introductions) or in time (climate change), yet the role of adaptation in how populations respond to these rapid environmental shifts is poorly understood. We conducted a large-scale trans-continental common garden experiment using white clover (Trifolium repens, Fabaceae) to test whether adaptive evolution to spatiotemporal variation in climate could contribute to the ecological success of one of the most widespread plant species in the world. Individuals from 96 populations of Trifolium repens (white clover) from both its native (Europe) and introduced (North America) ranges were planted into four experimental common gardens located in northern (Uppsala, Sweden) and southern (Montpellier, France) Europe, and northern (Mississauga, Canada) and southern (Lafayette, USA) North America. We recorded plant sexual and clonal fitness in each common garden and assessed whether the strength of local adaptation differed between the native and introduced ranges and whether populations are rapidly adapting to climate change. Results show that local adaptation was only evident when populations were transplanted into common gardens located in the same range (native or introduced) from which they originated and was driven by stronger selection (due to climatic factors rather than herbivory) at lower latitudes in both ranges. Our results indicate rapid local adaptation across a large latitudinal gradient in introduced T. repens populations, along with an associated adaptation cost when transplanted back into the native range. We also find evidence of an adaptation lag in the northern common garden in the introduced range, with plants from historically warmer climates exhibiting the greatest fitness. These findings support two major conclusions: 1) white clover can rapidly adapt to spatial variation in climate in its introduced range as well as the native range, and 2) despite rapid adaptation to novel environments, introduced white clover populations are not keeping pace with rapid climate change. Overall, our results provide insight into the role of adaptation in facilitating the ecological success of non-native species in a rapidly changing world. Open Research StatementData are provided for peer review. All data involved in this study is available on the GitHub page for LJA (https://github.com/ljalbano/transcontinental_common_garden).

evolutionary biology↗

bioRxiv2024

Evolution of drought resistance strategies following the introduction of white clover (Trifolium repens L.)

Background and AimsSuccess during colonization likely depends on growing quickly and tolerating novel and stressful environmental conditions. However, rapid growth, stress avoidance, and stress tolerance are generally considered divergent physiological strategies. MethodsWe evaluate how white clover (Trifolium repens) has evolved to a divergent water regime following introduction to North America. We conduct RNAseq within a dry-down experiment utilizing accessions from low and high latitude populations from native and introduced ranges, and assess variation in dehydration avoidance (avoidance of wilting) and dehydration tolerance (ability to survive wilting). Key ResultsIntroduced populations are better at avoiding dehydration, but poorer at tolerating dehydration than native populations. There is a strong negative correlation between avoidance and tolerance traits and expression of most drought-associated genes exhibits similar tradeoffs. Candidate genes with expression strongly associated with dehydration avoidance are linked to stress signaling, closing stomata and producing osmoprotectants. However, genes with expression linked to dehydration tolerance are associated with avoiding excessive ROS production and toxic bioproducts of stress responses. Several candidate genes show differential expression patterns between native and introduced ranges, and could underlie differences in drought resistance syndromes between ranges. ConclusionsThese results suggest there has been strong selection following introduction for dehydration avoidance at the cost of surviving dehydration.

evolutionary biology↗

bioRxiv2024

Structural variants underlie parallel adaptation following global invasion

Rapid adaptation during invasion has historically been considered limited and unpredictable. We leverage whole-genome sequencing of >2600 plants across six continents to investigate the relative roles of colonization history and adaptation during the worldwide invasion of Trifolium repens. Introduced populations contain high levels of genetic variation with independent colonization histories evident on different continents. Five large structural variants on three chromosomes exist as standing genetic variation within the native range, and exhibit strong signatures of parallel climate-associated adaptation across continents. Common gardens in the native and introduced ranges demonstrate that three structural variants exhibit patterns of selection consistent with local adaptation across each range. Our results provide strong evidence that rapid and parallel adaptation during invasion is caused by large-effect structural variants introduced throughout the world. Significance StatementBiological invasions occur over short timescales and introductions are often hypothesized to include limited genetic diversity, making the role of adaptation in invasion success controversial. We demonstrate that the invasion of a human-commensal species, Trifolium repens, likely stems from multiple, diverse introductions with significant evidence of climate-associated adaptation following introduction. The genetic basis of adaptation is most strongly linked to five chromosomal rearrangements that each span hundreds of genes - matching theoretical predictions that large-effect variants are key to the initial stages of adaptation to novel environments. Chromosomal rearrangements have remarkably parallel signatures of adaptation across different introductions despite initial colonization from different areas of Europe. Our study highlights the impact of globalization and rapid adaptation for the invasion success of human commensal species.

evolutionary biology↗

bioRxiv2023

Demographic consequences of an extreme heatwave are mitigated by spatial heterogeneity in an annual monkeyflower

Heatwaves are becoming more frequent and intense with climate change, but the demographic and evolutionary consequences of heatwaves are rarely investigated in herbaceous plant species. We examine the consequences of a short but extreme heatwave in Oregon populations of the common yellow monkeyflower (Mimulus guttatus) by leveraging a common garden experiment planted with range-wide populations and observational studies of eleven local populations. In the common garden, 89% of seedlings died during the heatwave including >96% of seedlings from geographically-local populations. Some populations from hotter and drier environments had higher fitness, however others from comparable environments performed poorly. Observational studies of local natural populations drastically differed in the consequences of the heatwave - one population was completely extirpated and nearly half had a >50% decrease in fitness. However, a few populations had greater fitness during the heatwave year. Differences in mortality corresponded to the impact of the heatwave on soil moisture - retention of soil moisture throughout the heatwave led to greater survivorship. Our results suggest that not all populations experience the same intensity or degree of mortality during extreme events and such heterogeneity could be important for genetic rescue or to facilitate the distribution of adaptive variants throughout the region.

ecology↗

bioRxiv2021

Unilateral Resection of Both Cortical Visual Pathways Alters Action but not Perception

The human cortical visual system consists of two major pathways, a ventral pathway that subserves perception and a dorsal pathway that subserves visuomotor control. These pathways follow dissociable developmental trajectories, and, accordingly, might be differentially susceptible to neurodevelopmental disorders or injuries. Previous studies have found that children with cortical resections of the ventral visual pathway retain largely normal visuoperceptual abilities. Whether visually guided actions, supported by computations carried out by the dorsal pathway, follow a similar pattern remains unknown. To address this question, we examined visuoperceptual and visuomotor behaviors in a pediatric patient, TC, who underwent a cortical resection that included portions of the left ventral and dorsal pathways. We collected data when TC used her right and left hands to perceptually estimate the width blocks that varied in width and length, and, separately, to grasp the same blocks. TCs perceptual estimation performance was comparable to that of controls, independent of the hand used. In contrast, relative to controls, she showed reduced visuomotor sensitivity to object shape and this was more evident when she grasped the objects with her contralesional right hand. These results provide evidence for a striking difference in the reorganization profiles of the two visual pathways. This difference supports the notion that the two pathways exhibit differential susceptibility to neurodevelopmental disorders.

neuroscience↗