Biology subjects

Davis, K. E.

Publications and source records attributed to Davis, K. E..

5 recordsLinked to original sources

bioRxiv2025

Dispersal transiently modifies the temperature dependence of ecosystem productivity after an extreme thermal fluctuation

Effects of warming on ecosystem productivity are typically summarized over broad time scales, yet they emerge from communities that can reorganize in a matter of days. Temperature accelerates ecosystem productivity through predictable effects on metabolic rates, but dispersal across thermally heterogeneous metacommunities may modify this effect by redistributing communities and their underlying thermal phenotypes. Using multi-trophic freshwater mesocosm communities in which warming and dispersal were manipulated, we tested the hypothesis that increasing dispersal modifies the thermal sensitivity of gross primary productivity (GPP) through the redistribution of phytoplankton biomass, size spectra, and thermal phenotype composition along spatial thermal gradients. High dispersal temporarily weakened the thermal sensitivity of GPP after an unplanned heatwave. This effect was caused by reduced mass-specific GPP in the warmest mesocosms accompanied by regional homogenization of phytoplankton communities and the spread of poorly adapted thermal phenotypes under the highest dispersal treatments. Except immediately post-heatwave, the thermal sensitivity of GPP was robust to dispersal, despite evidence of metacommunity dynamics. These findings suggest that the temperature dependence of ecosystem metabolism can be briefly modified by dispersal after a perturbation, but remains robust under steady-state conditions.

ecology↗

bioRxiv2025

A general temperature dependence for biological nitrogen fixation across systems and levels of organization

Biological nitrogen fixation (BNF) provides half of global new nitrogen annually and plays an important role in biodiversity patterns and global biological carbon uptake processes. BNF rates accelerate with warming, with known implications for ecological functioning, yet the strength of this temperature sensitivity and its context dependence are not well understood. Here we synthesized 70 controlled experimental tests of the acute temperature dependence of nitrogen fixation rates and found that BNF rates accelerate with temperature in a consistent way across levels of biological organization from enzyme to community, mirroring scaling of metabolic temperature dependence across levels of organization for respiration, photosynthesis and methane production. This BNF temperature dependence is also remarkably consistent across biological systems. This analysis shows multiple lines of evidence for general, scalable effects of temperature on nitrogen fixation rates, in line with previous suggestions of a strong enzyme-level constraint. This widespread pattern may be important for understanding effects of warming on coupled carbon-nitrogen systems with ongoing global change.

ecology↗

bioRxiv2019

Dimensions of passerine biodiversity along an elevational gradient: a nexus for historical biogeography and contemporary ecology

AimThe incorporation of functional and phylogenetic information is necessary to comprehensively characterize spatial patterns of biodiversity and to evaluate the relative importance of ecological and evolutionary mechanisms in molding such patterns. We evaluated the relative importance of mechanisms that shape passerine biodiversity along an extensive elevational gradient. LocationManu Biosphere Reserve in the Peruvian Andes TaxonSongbirds (order Passeriformes) MethodsWe quantified elevational gradients of species richness, phylogenetic biodiversity, and functional biodiversity for all passerines as well as separately for suboscines and oscines; determined if phylogenetic or functional biodiversity was consistent with random selection or if there was evidence of particular mechanisms dominating community assembly; and compared patterns for each dimension of biodiversity for the two suborders. ResultsFor all passerines and for suboscines, species richness decreased in a saturating fashion, phylogenetic biodiversity declined linearly, and functional biodiversity was stochastic along the elevation gradient. For oscines, species richness and phylogenetic biodiversity decreased linearly, and functional biodiversity decreased in a saturating fashion. Main conclusionsElevational gradients of biodiversity at Manu result from a combination of adaptations associated with radiations that occurred elsewhere (suboscines in Amazonian lowlands, oscines in colder climes of North America) and an in situ radiation in the Andes (tanagers). Our results suggest a combination of temperature-related physiological constraints and a reduction in functional redundancy associated with decreasing resource abundance at higher elevations molded the passerine assemblages along this elevational gradient. Explicit consideration of historical biogeography and conservatism of ancestral niches is necessary to comprehensively understand the mechanisms that mold gradients of biodiversity.

ecology↗

bioRxiv2019

Integrating multiple dimensions of biodiversity to inform global parrot conservation

Because biodiversity is increasingly threatened by habitat destruction and climate change, conservation agencies face challenges associated with an uncertain future. In addition to changes associated with climate and land use, parrots are threatened by hunting and capture for the pet trade, making them the most at-risk order of birds in the world. Parrots provide key ecosystem services, but remain understudied compared to other major bird orders despite their high extinction risk and ecological importance. Species richness is often used to identify high priority areas for conserving biodiversity. By definition, richness considers all species to be equally different. However, ongoing research emphasizes the importance of incorporating ecological functions (functional diversity) or evolutionary relationships (phylogenetic diversity) to more fully understand patterns of biodiversity, suggesting that using functional and phylogenetic information could improve conservation strategies. These distinctions among dimensions of biodiversity are important, because (1) areas of high species richness do not always represent areas of high functional or phylogenetic diversity, and (2) functional or phylogenetic diversity may better predict ecosystem function and evolutionary potential, which are essential for effective long-term conservation policy and management.\n\nOur objective was to create a framework for identifying areas of high species richness, functional diversity, and phylogenetic diversity within the global distribution of parrots We combined species richness, functional diversity, and phylogenetic diversity into an Integrated Biodiversity Index (IBI) to identify global biodiversity hotspots for parrots. We found important spatial mismatches among dimensions, which demonstrate that species richness is not always an effective proxy for other dimensions of parrot biodiversity. The IBI is an integrative and flexible index that can incorporate multiple dimensions of biodiversity, resulting in an intuitive and more direct way of assessing comprehensive goals in conservation planning (i.e., healthy ecosystem functioning and climate change resilience).

ecology↗

bioRxiv2018

Global cooling & the rise of modern grasslands: Revealing cause & effect of environmental change on insect diversification dynamics

Utilising geo-historical environmental data to disentangle cause and effect in complex natural systems is a major goal in our quest to better understand how climate change has shaped life on Earth. Global temperature is known to drive biotic change over macro-evolutionary time-scales but the mechanisms by which it acts are often unclear. Here, we model speciation rates for Orthoptera within a phylogenetic framework and use this to demonstrate that global cooling is strongly correlated with increased speciation rates. Transfer Entropy analyses reveal the presence of one or more additional processes that are required to explain the information transfer from global temperature to Orthoptera speciation. We identify the rise of C4 grasslands as one such mechanism operating from the Miocene onwards. We therefore demonstrate the value of the geological record in increasing our understanding of climate change on macro-evolutionary and macro-ecological processes.

ecology↗