Biology subjects

Deslippe, J. R.

Publications and source records attributed to Deslippe, J. R..

6 recordsLinked to original sources

bioRxiv2026

Community and leaf-level controls of carbon fluxes in an invaded New Zealand alpine tussock grassland

Climate warming and plant invasion are reshaping alpine communities, yet their combined effects on ecosystem carbon (C) balance remain poorly understood. We studied how warming and invasion interact to influence community level C fluxes, and the mechanisms underpinning these responses. Using field experiments manipulating warming and invader removal in two New Zealand alpine grasslands dominated by functionally distinct invaders (a shrub, Calluna vulgaris, and a forb, hawkweeds), we quantified net ecosystem exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (ER), alongside community, trait and abiotic factors. Warming did not enhance C uptake at either site, and we found no evidence of synergistic warming x invasion effects. Instead, responses were invader-dependent. At the shrub-invaded site, warming increased net C loss through elevated respiration without corresponding gains in GPP. In contrast, fluxes at the forb-invaded site were largely insensitive to treatments. Variation in C fluxes were driven by abiotic conditions and trait dominance at the shrub site, whereas species diversity (richness and evenness) exerted stronger control at the forb site. Our findings demonstrate that the impacts of invasion on ecosystem C balance depend on invader functional identity, with contrasting roles for trait dominance and biodiversity in regulating ecosystem function under warming.

ecology↗

bioRxiv2025

Climate-Driven Forest Reassembly Follows Divergent Functional Pathways in Cold- and Warm-Adapted Communities

AimClimate change leads to the widespread rearrangement of forests predominantly towards warm-adapted lower-elevation species. However, understanding the context-specific community assembly mechanisms that underlie these changes requires a mechanistic understanding of plant responses. Here, we use functional traits and diversity indices to identify distinct responses of warm- and cold-adapted forest communities. MethodsOur analysis used seven traits, including leaf morphology, size, nutrient content, and foliar isotopes across 3,625 sites over 49 years. We derived functional strategies from community-weighted mean trait values, assessed assembly mechanisms using five multi-trait functional diversity indices, and estimated structural change and turnover rates using abundance-based dissimilarity metrics. ResultsForest composition shifted significantly towards warm-adapted, lowland species with increasing temperature (+0.12 {degrees}C/decade) and decreasing precipitation (0.87%/decade). Communities concurrently increased in functional and species richness, but became functionally more similar, indicating niche packing. Disturbance recruitment shifted warm-adapted forests towards acquisitive traits, and increases in anisohydric strategies, reflecting possible effects of CO2 fertilisation under drought stress. Cold-adapted forests, in contrast, shifted to conservative strategies and were subject to stronger abiotic filtering. Moreover, changes in nitrogen isotope ratios point towards the importance of ectomycorrhizal associations to persist under climate change. Ecotonal mixed forests showed both responses and experienced the highest turnover. Main conclusionsNew Zealand forests follow biome-specific trajectories, characterised by distinct assembly mechanisms and context-dependent ecological responses. While uniform trends obscure these responses, they can be disentangled using a functional diversity framework that incorporates isotopic traits, offering a practical means to detect and interpret community reassembly under climate change.

ecology↗

bioRxiv2024

Variable responses of alpine-plant communities to warming and loss of dominant species

Responses of ecological communities to perturbations are inherently variable because responses of their constituent populations also vary. Species within a single community may show combinations of no response, positive responses, and negative responses to any given perturbation often canceling each other out resulting in small or no signal that the community level. Here we explore the impacts of warming and loss of the dominant species on alpine ecosystems in a global study. We investigate warming and species-loss treatments on population- and community-level dynamics across alpine-plant communities at two elevations in five globally-distributed mountain locations. Communities showed varied responses to treatments; no community showed strong responses to a single treatment. Rather, most sites were influenced by both perturbations. Populations within these communities responded idiosyncratically, suggesting that constituent species are not all equally robust to perturbations even when community-level effects appear weak. Our results highlight the challenge of making general predictions about population- and community-level responses of alpine ecosystems in the face of present and future perturbations.

ecology↗

bioRxiv2024

Plant interaction traits determine the biomass of arbuscular mycorrhizal fungi and bacteria in soil

Plant-arbuscular mycorrhizal fungal (AMF) mutualisms play key roles in the biodiversity and productivity of ecosystems. Yet we have limited understanding of the functional roles of plants as AMF generalists or specialists, and the consequences of these plant interaction traits for soil ecosystems are virtually unknown. We grew eight pasture plant species under two experimental conditions and determined their root AMF communities by sequencing. We determined plant species interaction traits with AMF using a set of numeric and phylogenetic -, {beta}- and {gamma}-diversities and characterized plant species relative interaction generalism for AMF. We used lipid analysis of rhizosphere soils and Bayesian modelling to explore how host interaction traits affected carbon allocation to AMF and bacteria. Plant interaction traits for AMF appear to be stable despite large variation in edaphic conditions and AMF pools. We show that host interaction generalism was associated with opposite patterns of bacterial and AMF biomass; the phylogenetic diversity of host interactions was positively associated with AMF biomass whereas the richness of host interactions was negatively associated with bacterial biomass in rhizosphere soils. Explicit consideration of plant interaction niches may enhance understanding of how changes in biodiversity affect ecosystem carbon cycling. Open research statementThis publication does not use novel code, and the bioinformatic and statistic pipelines for this manuscript will be made available at https://github.com/NLewe/Bayes-interaction-niche. Raw data will be made available at NCBI as BioProject: PRJNA997080

ecology↗

bioRxiv2021

A fluorescence-based viability assay for Phytophthora agathidicida oospores

Phytophthora are eukaryotic microbes that cause disease in a wide range of agriculturally and ecologically important plants. During the Phytophthora disease cycle, thick-walled oospores can be produced via sexual reproduction. These resting spores can survive in the soil for several years in the absence of a host plant, thus providing a long-term inoculum for disease. The ability to quantitatively evaluate oospore viability is an important part of many phytopathology studies. Here, we tested six fluorescent viability dyes for their ability to differentially stain Phytophthora agathidicida oospores: SYTO 9, FUN-1, fluorescein diacetate (FDA), 5-carboxyfluorescein diacetate (CFDA), propidium iodide, and TOTO-3 iodide. Each dye was first tested individually with untreated or heat-treated oospores as proxies for viable and non-viable oospores, respectively. SYTO9, FUN-1, CFDA and propidium iodide stained untreated and heat-treated oospores indiscriminately. In contrast, FDA (a green-fluorescent viable cell stain) and TOTO-3 (a red-fluorescent non-viable cell stain) differentially stained untreated or heat-treated oospores with no cross-fluorescence. We then tested the efficacy of dual viability staining and in conjunction with a pipeline for automated image analysis. To validate the method, untreated and heat-treated oospores were mixed at specific ratios, dual-stained, and analyzed using the pipeline. Linear regression of the resulting data showed a clear correlation between the expected and measured oospore ratios (dy/dx=0.95, R2=0.88). Overall, the combination of dual-fluorescence staining and automated image analysis provides a high-throughput method for quantitatively assessing oospore viability and therefore can facilitate further studies on this key part of the Phytophthora disease cycle.

microbiology↗

bioRxiv2021

The Fatty Acid Methyl Ester (FAME) profile of Phytophthora agathidicida and its potential use as diagnostic tool.

Phytophthora diseases cause devastation to crops and native ecosystems worldwide. In New Zealand, Phytophthora agathidicida is threatening the survival of kauri, an endemic, culturally and ecologically important tree species. The current method for detecting P. agathidicida is a soil bating assay that is time-consuming and requires high levels of expertise to assess, thus limiting the analytical sample throughput. Here, we characterized the fatty acid methyl ester (FAME) profile of P. agathidicida. We also compared it with the FAME profile of P. cinnamomi and assessed the efficacy of FAME analysis as a diagnostic tool for detecting the pathogen in soil samples. In FAME analysis, the total fatty acid content is isolated from a sample and converted to FAMEs for analysis, a process that takes less than a day. Unique fatty acid acyl chains can serve as biomarkers for specific organisms. We detected 12 fatty acids in P. agathidicida, two of which (20:4{omega}6 and 20:5{omega}3) show promise as potential Phytophthora specific biomarkers. Collectively, these findings advance our fundamental understanding of P. agathidicida biology and provide a promising technique to increase the rate of sample processing and the speed of pathogen detection for P. agathidicida in soil.

microbiology↗