Biology subjects

Parker, J. D.

Publications and source records attributed to Parker, J. D..

4 recordsLinked to original sources

bioRxiv2025

Microbial partners drive legume trait plasticity and tripartite interaction outcomes under combined stress environments

Plants often form partnerships with symbiotic microbes that improve plant performance. Increasing environmental stress is changing interaction dynamics between plants and their below-ground symbiotic partners, which can have cascading effects on above-ground trophic interactions. However, little work has examined how microbes protect plants against multiple stressors acting in concert, or the extent to which microbial genetic variation shapes context-dependent outcomes of tripartite interactions between microbes, plants, and herbivores. We experimentally manipulated the genetics of symbiotic microbial partners by individually inoculating a single legume species (Glycine max) with twenty-four genetically distinct strains of rhizobial bacteria. We quantified insect herbivore feeding and growth rates, as well as plant ecophysiological and performance traits under different combinations of drought and herbivore exposure. Rhizobial strains differentially influenced the effect of drought on legume ecophysiological traits. Certain strains increased photosynthesis and enhanced photoprotection under drought. Moreover, legumes under drought and herbivore exposure also exhibited increased photoprotection. Some strains were observed to limit herbivore growth rates under drought more effectively than others. A multivariate trait analysis revealed that strains differentially influenced legume trait syndromes and plasticity in response to stress in certain environments. Rhizobial strain variation was a key driver of tripartite interactions through changes in plant trait expression and plasticity under simultaneous abiotic and biotic stress, which had cascading effects on insect herbivore growth. A community approach incorporating multiple beneficial microbial strains may be effective for managing legume-rhizobia symbioses and introducing functional trait diversity and resistance traits into ecosystems.

ecology↗

bioRxiv2025

Bird occurrence and trophic interactions vary across gradients of tree diversity and microclimate in a planted forest

Deforestation reshuffles communities across landscapes with myriad consequences for ecosystem function. Following deforestation, rapid exposure to novel microclimates can act as a strong environmental filter, favoring warm-adapted species and decoupling trophic interactions. Forest restoration may partly reverse this process through increased habitat structure, food resources, and buffering of microclimates - each potentially modified by tree diversity. Despite growing evidence that tree diversity and cool microclimates help maintain animal diversity in natural forests, less is known about how these factors shape species assemblages or multitrophic dynamics in restoration areas. Here, using surveys and two field experiments within a long-term tree planting experiment, we assessed the relative effects of tree diversity, forest structure, and associated microclimate on fine-scale space use by birds and their top-down impacts on insects. Surveys showed that fine-scale occurrences of birds increased in cooler plots, which were associated with higher tree diversity and structural complexity. The strength of microclimate effects on bird occurrences was strongest for species that are forest specialists. To assess risk to insect herbivores from avian predation, we used a sentinel prey experiment and found that predation risk increased in warmer plots, counter to our expectations based on bird surveys. Last, we examined top-town effects of bird exclusion on leaf herbivory, finding that skeletonizing patterns of herbivory increased in exclosures and in cooler plots. Taken together, these results suggest that microclimate resulting from variation in forest structure shapes space use of birds at fine scales with complex outcomes for bird-herbivore-tree interactions in planted forests. Active restoration methods that enhance below-canopy cooling may improve biodiversity outcomes and help maintain species interactions that underlie many ecosystem functions.

ecology↗

bioRxiv2021

EVL and MIM/MTSS1 regulate actin cytoskeletal remodeling to promote dendritic filopodia in developing neurons

Dendritic spines are the postsynaptic compartment of a functional neuronal synapse, and are critical for synaptic connectivity and plasticity. The developmental precursor to dendritic spines, dendritic filopodia, are highly motile protrusions that facilitate synapse formation by sampling the environment for suitable axon partners during development and learning. Despite the significance of the actin cytoskeleton in driving these protrusions, the actin remodeling factors involved in this process are not fully characterized. In this work, we identify a critical function for the Ena/VASP protein EVL in the regulation of dendritic filopodia. Amongst the Ena/VASP proteins, EVL is uniquely required for the characteristic morphology and dynamics of dendritic filopodia. Using a combination of genetic and optogenetic manipulations, we demonstrate that EVL promotes protrusive motility through membrane-direct actin polymerization at dendritic filopodia tips. EVL forms a complex at nascent protrusions and dendritic filopodia tips with MIM/MTSS1, an I-BAR protein recently discovered to be important for initiation of dendritic filopodia. We propose a model in which EVL cooperates with MIM to elongate and coalesce branched actin filaments, establishing the dynamic lamellipodia-like architecture of dendritic filopodia in developing neurons.

cell biology↗

bioRxiv2018

Comparative metabolomics of forest communities: Species differences in foliar chemistry are greater in the tropics.

Interspecific variation in the secondary metabolites of plants constrains host specificity of insect herbivores and microbial pathogens. The intensity and specificity of these plant-pest interactions is widely believed to increase towards the Equator, leading to the prediction that secondary metabolites should differ more among co-occurring plant species in tropical communities than in temperate communities. To evaluate this prediction, we quantified metabolomic similarity for 203 tree species that represent >89% of all individuals in large forest plots in Maryland and Panama. We constructed molecular networks based on mass spectrometry of all 203 species, quantified metabolomic similarity for all pairwise combinations of species, and evaluated how pairwise metabolomic similarity varies phylogenetically. Leaf metabolomes exhibited clear phylogenetic signal for the temperate plot, with high similarity among congeneric species. In contrast, leaf metabolomes lacked phylogenetic signal for the tropical plot, with low similarity among congeners. Our results suggest that species differences in secondary chemistry comprise important axes of niche differentiation among tropical trees, especially within species-rich genera, and that the contribution of species differences in secondary chemistry to niche differences increases towards the equator in forest tree communities.

ecology↗