Biology subjects

Eckert, L.

Publications and source records attributed to Eckert, L..

6 recordsLinked to original sources

bioRxiv2025

Random and non-random variation in flower color along an urban-rural gradient in the introduced mustard Hesperis matronalis

PremiseUrbanization can alter the interplay of stochastic genetic drift and natural selection but these effects will depend on the biology and history of a species. To explore the influences of drift and selection we investigated patterns of flower color variation among populations of the introduced ornamental mustard, Hesperis matronalis, along an urban-rural gradient in eastern Ontario Canada. MethodsWe surveyed 136 naturalized stands of H. matronalis over three generations, and for each stand estimated the diversity of the three color morphs (white, pink, purple), the number of reproductive plants, and the degree of urbanization based on night sky brightness. Key ResultsFlower color morph diversity increased with both stand size and urbanization which is consistent with effects of genetic drift during colonization combined with multiple introductions of this horticultural plant in urban areas. However, the frequency and fixation of the purple morph systematically increased towards the rural end of the gradient. Although lifetime seed production did not vary among morphs, pre-dispersal seed predation by a recently adventive weevil was higher in the purple morph, particularly in rural areas. Estimated seed production in the absence of predation suggests a previous fitness advantage for the purple and pink morphs in rural areas and for the white morph in urban areas. ConclusionsRandom variation in flower color diversity may be influenced by stochastic processes and colonization history, while systematic variation in color morph frequencies may reflect past fitness differences among morphs that have been recently erased by seed predation.

evolutionary biology↗

bioRxiv2024

Exploring Meiosis in Brown Algae: Meiotic Axis Proteins in the model brown alga Ectocarpus

Most extant eukaryotic systems share core meiosis-specific genes, suggesting meiosis evolved only once in the last eukaryotic common ancestor (LECA). These genes have been characterized as master regulators of meiotic recombination, ensuring genetically diverse lineages. However, our understanding is limited as eukaryotic organisms beyond the animal, plant, and yeast lineages remain poorly understood. Recently, core meiotic genes have been identified in the genome of the model brown alga Ectocarpus, but currently lack proper characterization. Here, we combine bioinformatic, structural, and biochemical approaches to characterise the axial element orthologs, meiotic Ectocarpus HORMA domain protein (ecHOP1) and its interactor, reductional division protein 1 (ecRED1), in order to elucidate the molecular mechanisms of synaptonemal complex (SC) and double strand break (DSB) formation in brown algae. We highlight novel domain architecture within ecHOP1 and ecRED1 that support HORMA domain conformational switches and quantify the thermodynamic parameters of these interactions. Together, our data suggests that brown algae may employ alternative HORMA domain regulation mechanisms compared with animal, plant and yeast systems, and provide clues for future studies on the evolutionary constraints and adaptation of meiosis across the tree of life.

biochemistry↗

bioRxiv2024

Learning in single cells: biochemically-plausible models of habituation

The ability to learn is typically attributed to animals with brains. However, the apparently simplest form of learning, habituation, in which a steadily decreasing response is exhibited to a repeated stimulus, is found not only in animals but also in single-cell organisms and individual mammalian cells. Habituation has been codified from studies in both invertebrate and vertebrate animals, as having ten characteristic hallmarks, seven of which involve a single stimulus. Here, we show by mathematical modelling that simple molecular networks, based on plausible biochemistry with common motifs of negative feedback and incoherent feedforward, can robustly exhibit all single-stimulus hallmarks. The models reveal how the hallmarks arise from underlying properties of timescale separation and reversal behaviour of memory variables and they reconcile opposing views of frequency and intensity sensitivity expressed within the neuroscience and cognitive science traditions. Our results suggest that individual cells may exhibit habituation behaviour as rich as that in multi-cellular animals with central nervous systems and that the relative simplicity of the biomolecular level may enhance our understanding of the mechanisms of learning.

systems biology↗

bioRxiv2024

Destabilized host-parasite dynamics in newly founded populations

When species disperse into previously unoccupied habitats, new populations encounter unfamiliar species interactions such as altered parasite loads. Theory predicts that newly founded populations should exhibit destabilized eco-evolutionary fluctuations in infection rates and immune traits. However, to understand founder effects biologists typically rely on retrospective studies of range expansions, missing early-generation infection dynamics. To remedy this, we experimentally founded whole-lake populations of threespine stickleback. Infection rates were temporally stable in native source lakes. In contrast, newly founded populations exhibit destabilized host-parasite dynamics: high starting infection rates led to increases in a heritable immune trait (peritoneal fibrosis), suppressing infection rates. The resulting temporal auto-correlation between infection and immunity suggest that newly founded populations can exhibit rapid host-parasite eco-evolutionary dynamics.

evolutionary biology↗

bioRxiv2023

Overall biomass yield of multiple nutrient sources

Microorganisms utilize nutrients primarily to generate biomass and replicate. When a single nutrient source is available, the produced biomass increases linearly with the initial amount of the available nutrient. This linear trend can be predicted to high accuracy by "black box models" that consider growth as a single chemical reaction with nutrients as substrates and biomass as a product. Since natural environments typically feature multiple nutrients, we here quantify the effect of co-utilization of multiple nutrients on bacterial biomass production. First, we demonstrate a mutual effect between the metabolism of different nutrient sources where the ability to utilize one is affected by the other. Second, we show that for some nutrient combinations, the produced biomass is no longer linear to the initial amount of nutrients. These observations cannot be explained by the traditional "black box models", presumably because the metabolism of one nutrient affects another, which is not accounted for by these models. To capture these observations, we extent "black box models" to include catabolism, anabolism, and biosynthesis of biomass precursors and phenomenologically add a mutual effect between the metabolism of the nutrient sources. The expanded model qualitatively recaptures the experimental observations and, unexpectedly, predicts that the produced biomass is not only dependent on the combination of nutrient sources but also on their relative initial amounts. We validate this prediction experimentally by demonstrating how measurement of the produced biomass can be used to determine how each nutrient effects the metabolic processes of another.

microbiology↗

bioRxiv2022

Adaptive plasticity in the healthy reading network investigated through combined neurostimulation and neuroimaging

The reading network in the human brain comprises several regions, including the left inferior frontal cortex (IFC), ventral occipito-temporal cortex (vOTC) and dorsal temporo-parietal cortex (TPC). The left TPC is crucial for phonological decoding, i.e., for learning and retaining sound-letter mappings. Here, we tested the causal contribution of this area for reading with repetitive transcranial magnetic stimulation (rTMS) and explored the response of the reading network using functional magnetic resonance imaging (fMRI). 28 healthy adult readers overtly read simple and complex words and pseudowords during fMRI after effective or sham TMS over the left TPC. Behaviorally, effective stimulation slowed pseudoword reading. A multivariate pattern analysis showed a shift in activity patterns in the left IFC for pseudoword reading after effective relative to sham TMS. Furthermore, active TMS led to increased effective connectivity from the left vOTC to the left TPC, specifically for pseudoword processing. The observed changes in task-related activity and connectivity suggest compensatory reorganization in the reading network following TMS-induced disruption of the left TPC. Our findings provide first evidence for a causal role of the left TPC for overt pseudoword reading and emphasize the relevance of functional interactions in the healthy reading network for successful pseudoword processing.

neuroscience↗