Biology subjects

Garner, M.

Publications and source records attributed to Garner, M..

5 recordsLinked to original sources

bioRxiv2024

Genetically based variation in fitness and carbon assimilation among bur oak populations

Ongoing climate change will negatively impact tree populations unless they are able to acclimate to the changes in their local environment. Effective planning for climate adaptation management requires an understanding of the current state of local adaptation and physiological performance to assess whether populations are at risk of local extinction, to determine if seed movement is appropriate, and to select appropriate seed sources if intervention is needed. We established a new reciprocal transplant experiment (ACE, Adaptation to Climate and Environment) across a latitudinal gradient in North America to examine the impacts of warming on three bur oak (Quercus macrocarpa) populations across much of the species range. We established common gardens in Minnesota, Illinois, and Oklahoma with seedlings grown from seeds collected within 50 km of each of those locations from a total of sixty maternal families. We aimed to 1) assess local adaptation in each of the populations using survival and size as fitness metrics, and 2) evaluate physiological responses to different environments along the latitudinal gradient. We found that northern populations are maladapted to hotter climates as evidenced by their low survival, growth, and photosynthetic rates in the warmest common garden. The southernmost population had the highest survival rate, growth rate, and fitness of the three populations in the southernmost garden, providing evidence for local adaptation to the warmest site. However, conditions in the middle garden resulted in the highest fitness and best physiological performance for all populations. Growth and survival were correlated in the middle garden but were decoupled in the northern and southern gardens. This decoupling is likely due to stress associated with more extreme climates at the ends of the gradient that led to greater resource allocation to survival than to growth. Our results suggest that southern seed sources may perform well in warmer conditions in the north brought on by climate change, which has important implications for managers assisting broadly ranged tree species in adapting to climate change.

ecology↗

bioRxiv2020

Effects of population, latitude, and individual tree to leaf variation in oaks: An empirical study and simulation of sampling strategies in bur oak (Quercus macrocarpa, Fagaceae)

PREMISELeaf shape and size figure strongly in trees adaptation to their environments. Oaks are notoriously variable in leaf morphology. Our study examines the degree to which within-tree, among-tree, and among-site variation contribute to latitudinal variation in leaf shape and size of bur oak (Quercus macrocarpa: Fagaceae), one of North Americas most geographically widespread oak species. METHODSSamples were collected from four sites each at northern, central, and southern latitudes of the bur oak range. Ten leaf size traits were measured, and variance in these traits and eight ratios based on these traits was partitioned into tree, population, and latitude components. We then parameterized a series of leaf collection simulations using empirical covariance among leaves on trees and trees at sites. We used the simulations to assess the efficiency of different collecting strategies for estimating among-population differences in leaf shape and size. KEY RESULTSLeaf size measurements were highly responsive to latitude. Site contributed more than tree to total variation in leaf morphology. Simulations suggest that power to detect among-site variance in leaf shape and size can be estimated most efficiently with increases in either leaves per tree (10-11 leaves from each of 5 trees) or trees per site (5 leaves from each of 10+ trees). CONCLUSIONSOur study demonstrates the utility of simulating sampling and controlling for variance in sampling for leaf morphology, whether the questions being addressed are ecological, evolutionary, or taxonomic. Simulation code is provided as an R package (traitsPopSim) to help researchers plan morphological sampling strategies.

plant biology↗

bioRxiv2020

Repeated parallel losses of inflexed stamens in Moraceae: phylogenomics and generic revision of the tribe Moreae and the reinstatement of the tribe Olmedieae (Moraceae)

We present a densely-sampled phylogenomic study of the mulberry tribe (Moreae, Moraceae), an economically important clade with a global distribution, revealing multiple losses of inflexed stamens, a character traditionally used to circumscribe Moreae. Inflexed stamens facilitate ballistic pollen release and are associated with wind pollination, and the results presented here suggest that losses of this character state may have evolved repeatedly in Moraceae. Neither Moreae nor several of its major genera (Morus, Streblus, Trophis) were found to be monophyletic. A revised system for a monophyletic Moreae is presented, including the reinstatement of the genera Ampalis, Maillardia, Taxotrophis, and Paratrophis, and the recognition of the new genus Afromorus, based on Morus subgenus Afromorus. Pseudostreblus is reinstated and transferred to the Parartocarpeae, and Sloetiopsis is reinstated and transferred to the Dorstenieae. The tribe Olmediae is reinstated, replacing the Castilleae, owing to the reinstatement of the type genus Olmedia, and its exclusion from Moreae. Streblus s.s. is excluded from Moreae and transferred to the Olmediae, which is characterized primarily by involucrate inflorescences without regard to stamen position. Eight new combinations are made.

plant biology↗

bioRxiv2019

Brain functional connectivity correlates of response in the 7.5% CO2 inhalational model of generalized anxiety disorder: a pilot study

The 7.5% CO2 inhalational model ( CO2 challenge) can be used to explore potential treatments for generalized anxiety disorder. However, it remains unknown how inter-individual variability in the functional architecture of negative affective valence systems might relate to the anxiogenic response to CO2 challenge. In this pilot study, we explored how connectivity in systems associated with processing potential threat (\"anxiety\") correlated with behavioural measures of anxiety following prolonged CO2 inhalation.\n\nThe negative affective valence system was identified using a passive emotional face perception task. Spherical regions of interest were created from peak voxels of significant brain activation when 100 young adult participants viewed emotional faces compared with black and white concentric circles during a functional MRI scan. Using these regions of interest, generalized psychophysiological interaction (gPPI) analysis was undertaken to explore task-evoked functional connectivity in a separate group of 13 healthy volunteers. Within 7 days of the scan, these participants underwent CO2 challenge and results from the gPPI analysis were correlated with CO2 outcome measures.\n\nExposure to CO2 challenge significantly increased subjective anxiety, negative affect, systolic blood pressure and heart rate. Functional connectivity between the ventromedial prefrontal cortex and right amygdala was positively correlated with heart rate. Increased connectivity between the vmPFC and the right amygdala, and decreased connectivity between the midcingulate cortex (MCC) and the left amygdala, correlated with subjective anxiety during CO2 challenge.\n\nResponse to CO2 challenge was related to task-evoked functional connectivity between regions known to be important in processing potential threat. Further studies are required to assess whether this translates into clinical populations. Measures of functional connectivity within emotional processing networks could be potential biomarkers to enable stratification of healthy volunteers, and to examine correlates of response, in trials using experimental medicine models.

neuroscience↗

bioRxiv2019

Conserved DNA polymorphisms distinguish species in the eastern North American white oak syngameon: Insights from an 80-SNP oak DNA genotyping toolkit

The eastern North American white oaks, a complex of approximately 16 potentially interbreeding species, have become a classic model for studying the genetic nature of species in a syngameon. Genetic work over the past two decades has demonstrated the reality of oak species, but gene flow between sympatric oaks raises the question of whether there are conserved regions of the genome that define oak species. Does gene flow homogenize the entire genome? Do the regions of the genome that distinguish a species in one part of its range differ from the regions that distinguish it in other parts of its range, where it grows in sympatry with different species? Or are there regions of the genome that are relatively conserved across species ranges? In this study, we revisit seven species of the eastern North American white oak syngameon using a set of 80 SNPs selected in a previous study because they show differences among, and consistency within, the species. We test the hypothesis that there exist segments of the genome that do not become homogenized by repeated introgression, but retain distinct alleles characteristic of each species. We undertake a rangewide sampling to investigate whether SNPs that appeared to be fixed based on a relatively small sample in our previous work are fixed or nearly fixed across the range of the species. Each of the seven species remains genetically distinct across its range, given our diagnostic set of markers, with relatively few individuals exhibiting admixture of multiple species. SNPs map back to all 12 Quercus linkage groups (chromosomes) and are separated from each other by an average of 7.47 million base pairs ({+/-} 8.74 million bp, s.d.), but are significantly clustered relative to a random null distribution, suggesting that our SNP toolkit reflects genome-wide patterns of divergence while potentially being concentrated in regions of the genome that reflect a higher-than-average history of among-species divergence. This application of a DNA toolkit designed for the simple problem of identifying species in the field has an important implication: the eastern North American white oak syngameon is composed of entities that most taxonomists would consider \"good species,\" and species in the syngameon retain their genetic cohesion because characteristic portions of the genome do not become homogenized despite a history of introgression.

evolutionary biology↗