Biology subjects

Sunday, J. M.

Publications and source records attributed to Sunday, J. M..

7 recordsLinked to original sources

bioRxiv2026

Temperature-dependent performance scales with maximum heat tolerance across ectotherms

Projecting species responses to changing temperatures remains a major challenge in ecology. Central to this effort is harnessing our understanding of species thermal physiological traits, which underlie ectotherm fitness. These traits are typically characterized by describing performance across temperatures (thermal performance curve, TPC), and/or tolerance limits, which capture endpoints of biological failure. Despite their importance, we still lack an understanding of the functional relationship between these traits, limiting our ability to integrate them into comprehensive vulnerability assessments. Using a synthesized dataset of >100 ectotherms, we tested how heat tolerance (CTmax) relates to key TPC traits: thermal optima, thermal maxima, and the supra-optimal range of temperatures where performance is positive. Across taxa, TPC traits were positively related to CTmax, demonstrating a link between heat tolerance and temperature-dependent performance at sub-critical temperatures. While acute locomotor performance scaled proportionally with CTmax, metabolic processes and sustained locomotion scaled sub-proportionally, suggesting decoupling of CTmax and performance among high-CTmax species. This suggests that using CTmax as a comparative metric may overestimate thermal safety margins for metabolic processes critical to growth. Our results indicate that while CTmax and TPCs reflect shared underlying constraints--particularly in acute neuro-muscular traits--their relationship is dependent on timescale and the TPC response trait. Our findings connect our understanding of the processes that maintain performance over thermal gradients with those that cause performance to fail, improving our ability to project species persistence in a warming world. SignificanceClimate warming is increasingly reshaping the thermal environments that govern species persistence worldwide. Predicting vulnerability requires integrating multiple aspects of thermal biology, yet relationships among widely used thermal traits remain poorly understood. By synthesizing data from more than 100 ectotherm species, we quantify links between acute heat tolerance and traits describing sustained biological function across temperatures. We show that performance at relatively benign temperatures and performance at thermal extremes are coupled, but this coupling is strongly process and timescale dependent, with close correspondence for short term locomotion but weaker coupling for metabolic processes. Our results link the processes that maintain performance across temperatures with those that cause failure, fundamentally advancing our projections of species performance in a warming world.

ecology↗

bioRxiv2026

Dispersal rate limits range expansion rate only when it is slower than climate velocity

Low dispersal ability might limit a species capacity to track its climate preferences across the landscape, yet evidence that low dispersal slows species range shifts under contemporary climate change remains contentious. Here we develop a new hypothesis under which we expect variation in dispersal ability to affect range expansion rates only when climate velocity exceeds dispersal rates, which is logical yet rarely applied because it requires a common yardstick to compare rates. We test this hypothesis using empirical relationships between dispersal ability, local range expansion rate, and the velocity of isotherm shifts in terrestrial plants and birds, all estimated in km/yr. In 370 range shifts, we found that range expansion rates were best explained by the slower of either a species dispersal rate or the velocity of isotherm shifts, as predicted under our hypothesis. Furthermore, when species dispersal rates were slower than the velocity of isotherm shifts, we found that dispersal ability positively affects range shift rates. Substantial variation in range expansion rates remained unexplained, indicating that additional factors influence range shift dynamics. Our results provide new clarity when understanding the role of dispersal ability on variation in range shift rates and emphasize the importance of evaluating dispersal capacity relative to climatic change exposure when testing hypotheses about species responses to ongoing environmental change. Significance StatementSpecies dispersal ability is widely thought to limit biodiversity redistribution in response to climate change, but we still lack a clear understanding of when or for which species dispersal limitations matter. Using hundreds of range expansion rates documented over the 10 last decades for terrestrial birds and plants together with their dispersal rates, in common units of km/yr, we show that dispersal ability slows climate-mediated range expansion, but that dispersal limitations occur only when the rates of climate change are faster than the ability of species to redistribute. So far, many species display dispersal rates higher than the velocity of climate change but dispersal limitations may become more pronounced in the future.

ecology↗

bioRxiv2026

Thermal performance in fishes varies systematically across latitude, habitat, and biological organization

Thermal performance curves are widely used to understand how ectotherms respond to anthropogenic climate change, yet comparable data remain fragmented for fishes despite their predicted sensitivity to warming. Here we introduce FishTherm, a compilation of 457 thermal responses from 107 wild fish species, spanning diverse performance metrics and temperatures. With this dataset, we estimated thermal optima, performance breadth, tolerance breadth, and activation energies, and tested how these thermal traits vary geographically, across latitude and habitat, and by type and functional context of performance. Thermal optima increase toward lower latitudes and warmer waters, consistent with established biogeographic patterns. We also found that responses measured at lower levels of biological organization exhibit higher thermal optima than population-level responses, supporting complexity constraints on thermal performance curves. Activation energies broadly matched predictions from the Metabolic Theory of Ecology, and we further found systematic variation of lower values in negatively-motivated responses, and associated with narrower thermal performance breadths, in line with theory. Our results provide supporting evidence for several unifying principles that advance our understanding of constraints and variation in thermal performance. FishTherm is a new resource for comparative thermal ecology and for improving our understanding of fish vulnerability under climate warming.

ecology↗

bioRxiv2025

Urbanization weakens the latitudinal diversity gradient in birds

The latitudinal diversity gradient of increasing species richness toward the tropics is Earths most ubiquitous and ancient macroecological pattern, but may not be immune to modern anthropogenic change. Urbanization represents a particularly severe and globally-distributed ecological change; while urbanization generally reduces local diversity, whether it affects large- scale diversity patterns is unclear. Analyzing global databases including >10,000 bird species on five continents, we show that the avian latitudinal diversity gradient is 3x weaker in urban than natural areas. Urbanization reduces diversity across latitudes, but tropical cities lose disproportionately more species, partly because tropical bird assemblages contain more specialists and specialists are particularly excluded by urbanization. Our results show that urbanization is disrupting macroecological patterns, and suggest that specialization mediates both latitudinal diversity gradients and urbanization impacts.

ecology↗

bioRxiv2022

Temperature dependence of competitive ability differs from that of growth rate

The effect of climate warming on future community composition is expected to be contingent on competitive outcomes, yet we currently lack mechanistic ecological understanding of how temperature affects competitive ability. Here, we combine resource competition theory with metabolic scaling theory and test hypotheses about how the temperature dependence of competitive ability changes with temperature. We find that the minimum resource requirement for growth, R* - an inverse indicator of competitive ability in phytoplankton - changes with temperature following a U-shaped pattern in all four species tested. The shape of temperature-dependence of competitive ability is systematically different from the temperature-dependence of population growth rates, both in our experiments and in collated data from previous studies. Our results suggest that exploitative competitive success is highest at temperatures that are sub-optimal for growth, and declines rapidly at both cold and warm ends of the thermal performance curve.

ecology↗

bioRxiv2018

Nonlinear averaging of thermal experience predicts population growth rates in a thermally variable environment

As thermal regimes change worldwide, projections of future population and species persistence often require estimates of how population growth rates depend on temperature. These projections rarely account for how temporal variation in temperature can systematically modify growth rates relative to projections based on constant temperatures. Here, we tested the hypothesis that population growth rates in fluctuating thermal environments differ from growth rates in constant conditions, and that the differing thermal performance curves (TPCs) can be predicted quantitatively. With experimental populations of the green alga Tetraselmis tetrahele, we show that nonlinear averaging techniques accurately predicted increased as well as decreased population growth rates in fluctuating thermal regimes relative to constant thermal regimes. We extrapolate from these results to project critical temperatures for population growth and persistence of 89 phytoplankton species in naturally variable thermal environments. These results advance our ability to predict population dynamics in the context of global change.

ecology↗

bioRxiv2017

An empirical test of the temperature dependence of carrying capacity

Predicting population persistence and dynamics in the context of global change is a major challenge for ecology. A widely held prediction is that population abundance at carrying capacity decreases with warming, assuming no change in resource supply, due to increased individual resource demands associated with higher metabolic rates. However, this prediction, which is based on metabolic scaling theory (MST), has not been tested empirically. Here we experimentally tested whether effects of temperature on short-term metabolic performance (rates of photosynthesis and respiration) translate directly to effects of temperature on population rates in a phytoplankton species. We found that effects of temperature on organismal metabolic rates matched theoretical predictions, and that the temperature dependence of individual metabolic performance translated to population abundance. Population abundance at carrying capacity, K, decreased with temperature less than expected based on the temperature dependence of photosynthesis. Concurrent with declines in abundance, we observed a linear decline in cell size of approximately 2.3% {degrees}C-1, which is consistent with broadly observed patterns in unicellular organisms, known as the temperature-size rule. When theoretical predictions include higher densities allowed by shifts toward smaller individual size, observed declines in K were quantitatively consistent with theoretical predictions. Our results indicate that outcomes of population dynamics across a range of temperatures reflect organismal responses to temperature via metabolic scaling, providing a general basis for forecasting population responses to global change.

ecology↗