Here we review and extend the equal fitness paradigm (EFP) as an important step in developing and testing a synthetic theory of ecology and evolution based on energy and metabolism. The EFP states that all organisms are equally fit at steady state, because they allocate the same quantity of energy, ~22.4 kJ/g/generation to production of offspring. On the one hand, the EFP may seem tautological, because equal fitness is necessary for the origin and persistence of biodiversity. On the other hand, the EFP reflects universal laws of life: how biological metabolism – the uptake, transformation and allocation of energy – links ecological and evolutionary patterns and processes across levels of organization from: i) structure and function of individual organisms, ii) life history and dynamics of populations, iii) interactions and coevolution of species in ecosystems. The physics and biology of metabolism have facilitated the evolution of millions of species with idiosyncratic anatomy, physiology, behavior and ecology but also with many shared traits and tradeoffs that reflect the single origin and universal rules of life.
Invasive ants shape assemblages and interactions of native species, but their effect on fundamental ecological processes is poorly understood. In East Africa, Pheidole megacephala ants have invaded monodominant stands of the ant-tree Acacia drepanolobium, extirpating native ant defenders and rendering trees vulnerable to canopy damage by vertebrate herbivores. We used experiments and observations to quantify direct and interactive effects of invasive ants and large herbivores on A. drepanolobium photosynthesis over a 2-year period. Trees that had been invaded for ≥ 5 years exhibited 69% lower whole-tree photosynthesis during key growing seasons, resulting from interaction between invasive ants and vertebrate herbivores that caused leaf- and canopy-level photosynthesis declines. We also surveyed trees shortly before and after invasion, finding that recent invasion induced only minor changes in leaf physiology. Our results from individual trees likely scale up, highlighting the potential of invasive species to alter ecosystem-level carbon fixation and other biogeochemical cycles.
Over the past fifteen years, the number of papers focused on “eco-evo dynamics” has increased exponentially (Figure 1). This pattern suggests the rapid growth of a new, integrative discipline. We argue that this overstates the case. First, the terms “eco-evo dynamics” and “eco-evo interactions” are used too imprecisely. As a result, many studies that claim to describe eco-evo dynamics are actually describing basic ecological or evolutionary processes. Second, these terms are often used as if the study of how ecological and evolutionary processes are intertwined is novel when, in fact, it is not. The result is confusion over what the term “eco-evolution” and its derivatives describe, a loss of appreciation for the history of genuine eco-evolutionary studies, and a loss of appreciation for the novelty associated with the original rise of the term. We advocate a more precise definition of eco-evolution that is more useful in our effort to understand and characterize the diversity of ecological and evolutionary processes and that focuses attention on the subset of those processes that offer novel results.
Large occurrence datasets provide a sizable resource for ecological analyses, but have substantial limitations. Phenological analyses in Fric et al. (2020) were misleading due to inadequate curation and improper statistics. Our reanalysis of 22 univoltine species with sufficient data for independent analysis found substantive differences in macroscale phenological patterns.
Banks-Leite et al. (2021) claim that our suggestion of preserving ≥40% forest cover lacks evidence and can be problematic. We find these claims unfounded, and discuss why conservation planning urgently requires valuable, well-supported, and feasible general guidelines like the 40% criterion. Using region-specific thresholds worldwide is unfeasible and potentially harmful.
Research in ecology and evolutionary biology (EEB) plays a key role in understanding and intervening in our current environmental and climate crisis. Although anthropogenic stressors and climate change continue to disproportionately affect Black, Indigenous, and people of colour (BIPOC) individuals, their valuable scientific voices are shockingly underrepresented within EEB. To underscore this problem, we present a case study on EEB PhD graduates in the US (1994-2018), which illustrates that BIPOC scholars are significantly underrepresented in their cohorts. We recommend key steps that the EEB Academy should take to increase representation of BIPOC scholars in EEB, including anti-racism education and practice, increased funding opportunities, integration of diverse cultural perspectives, and a community-minded shift in PhDs. Importantly, this advice is directed at those who wield power in the Academy (e.g., funding agencies, societies, institutions, departments, and faculty), rather than BIPOC scholars already struggling against inequitable frameworks in EEB.
Long-term experiments are important in evaluating ecosystem properties and processes that are slow to develop or require proper evaluation over an appropriately variable climate. We repurpose the wealth of data accessible through the forty-year-old Long-Term Ecological Research (LTER) network with a novel moving window algorithm and meta-analysis approach to ask if aspects of study taxa or environment alter the extent of research necessary to detect consistent results, or the proportion of spurious short-term trends. We found that experimental studies focused on plants, and those conducted in dynamic abiotic environments, were characterized by longer critical temporal thresholds and more spurious trends. Further, nearly half of the studies we investigated required 10 years or longer to reach a temporal threshold, and 4 studies (of 100) required longer than 20 years. We champion long-term data and argue that long-term experiments are more necessary than ever to understand, explain, and predict long-term trends.
Vector-borne diseases (VBDs) are embedded within complex socio-ecological systems. While research has traditionally focused on direct effects of VBDs on morbidity and mortality, it is increasingly clear that VBD impacts are much more pervasive, dynamically linked to feedbacks between environmental conditions, vector ecology, disease burden, and societal responses that drive transmission. VBDs have had profound influence on human history via mechanisms that include: (1) killing or debilitating large numbers of people, with direct demographic and population-level impacts; (2) differentially affecting populations based on prior history of disease exposure, immunity, and resistance; (3) being weaponized to promote or justify existing hierarchies of power, colonialism, racism, classism, and sexism; (4) catalyzing changes in ideas, institutions, infrastructure, technologies, and social practices in efforts to control disease outbreaks; and (5) changing human relationships with the land and environment. We use historical and archaeological evidence interpreted through an ecological lens to illustrate how four major VBDs have shaped society and culture: plague, malaria, yellow fever, and trypanosomiasis. By comparing across diseases, time periods, and geographies, this review highlights the enormous scope and variety of mechanisms by which VBDs have influenced human history from the age of early Homo sapiens to the modern context.
Boreal forests soils are important global carbon sinks, with significant storage in the organic topsoil. Decomposition of these stocks requires oxidative enzymes, uniquely produced by fungi, of which many live in ectomycorrhizal symbiosis with the trees. Here we show that presence of a group of closely related species of ectomycorrhizal fungi – Cortinarius acutus s.l. – decreased local carbon storage in the organic topsoil by 33% across Swedish forests. Our findings challenge the prevailing view that ectomycorrhizal fungi generally act to increase carbon storage in soils and show that certain ectomycorrhizal fungi can complement free-living decomposers, maintaining nutrient cycling and tree productivity under nutrient poor conditions. The finding that a narrow group of fungi exerts a major influence on carbon cycling refutes the prevailing dogma of functional redundancy among microbial decomposers. Cortinarius acutus s.l. responds negatively to forestry, and population declines are likely to increase soil carbon sequestration while impeding nutrient cycling.
A recent review on optimal strategies for preserving biodiversity within human-modified landscapes suggests that that forest cover needs to be restored or maintained to at least 40%. While we agree that it is paramount to protect and increase cover in forested biomes, no evidence is presented to support this 40% threshold. Furthermore, there are several issues regarding implementation of such policy or social-economic constraints that makes this suggestion unhelpful and potentially dangerous.
Size and shape profoundly influence an organism’s ecophysiological performance and evolutionary fitness, suggesting a link between morphology and diversity. However, not much is known about how body shape is related to taxonomic richness, in particular in the microbial realm. Here we analyse global datasets of unicellular phytoplankton, a major photosynthetic group with an exceptional diversity of cell sizes and shapes. Using two measures of cell shape elongation, we quantify taxonomic diversity as a function of cell size and shape. We find that cells of intermediate volume have the greatest shape variation, from oblate to extremely elongated forms, while small and large cells are mostly compact (e.g., spherical or cubic). Taxonomic diversity is strongly related with cell elongation and cell volume, with both traits, in combination, explaining up to 92% of total variance. Diversity decays exponentially with cell elongation and displays a log-normal dependence on cell volume, peaking for compact, intermediate-volume cells. These previously unreported broad patterns in phytoplankton diversity reveal selective pressures and ecophysiological constraints on the geometry of phytoplankton cells which may improve our understanding of marine ecology and the evolutionary rules of life.
The Maximum Entropy Theory of Ecology (METE) predicts the shapes of macroecological metrics in relatively static ecosystems using constraints imposed by static state variables. In disturbed ecosystems, however, with time-varying state variables, its predictions often fail. We extend macroecological theory from static to dynamic by combining the MaxEnt inference procedure with explicit mechanisms governing disturbance. In the static limit, the resulting theory, DynaMETE, reduces to METE but also predicts new scaling relationships among static state variables. Under disturbances, expressed as shifts in demographic, ontogenic growth, or migration rates, DynaMETE predicts the time trajectories of the state variables as well as the time-varying shapes of macroecological metrics such as the species abundance distribution and the distribution of metabolic rates over individuals. An iterative procedure for completely solving the dynamic theory is presented. In a lowest-order iteration, characteristic signatures of the deviation from static predictions of macroecolgoical patterns are shown to result from different kinds of disturbance. Because DynaMETE combines MaxEnt inference with explicit dynamical mechanisms, but does not assume any specific trait distributions over species or individuals, it is widely applicable across diverse ecosystems. This makes it a promising theory of macroecology for ecosystems responding to anthropogenic or natural disturbances.
In ectothermic predator-prey relationships, the capacity for prey to successfully evade predation will depend upon physiological and behavioural responses that relate to both players’ thermal biology. On the Izu Islands of Japan, we investigated how a prey lizard species has responded physiologically and thermally to the presence of a snake predator over evolutionary time in addition to recent climatic warming. Foraging lizard body temperatures have increased by 1.0°C from 1981 to 2019 while lizard body temperatures were 3.4°C warmer on islands where the snake predator is present relative to snake-free islands. We also found that warmer prey body temperatures result in faster running speeds of the prey at temperatures suboptimal for the snake predator. The results show that lizard body temperatures have increased with warming but not to the same extent as that exerted by predation pressure. However, further warming could irrevocably alter this and other ectothermic predator-prey relationships.
Forecasts of forest responses to climate variability are governed by climate exposure and ecosystem sensitivity, but ecosystem model projections and process representations are under-constrained by data at multidecadal and longer timescales. Here, we assess ecosystem sensitivity to centennial-scale hydroclimate variability, by comparing dendroclimatic and pollen-inferred reconstructions of drought, forest composition and biomass for the last millennium with five ecosystem model simulations. In both observations and models, spatial patterns in ecosystem responses to hydroclimate variability are strongly governed by ecosystem sensitivity rather than climate exposure. Ecosystem sensitivity was highest in simpler models and higher than observations, suggesting that interactions among biodiversity, demography, and ecophysiology processes dampen the sensitivity of forest composition and biomass to climate variability and change. By integrating ecosystem models with observations from timescales extending beyond the instrumental record, we can better understand and forecast the mechanisms regulating forest sensitivity to climate variability in a complex and changing world.
The recent upsurge in the edible insect market has seen industrialisation and intensification without adequate regulatory policy guidelines in place. The species being reared and sold are often non-native, in rearing centres not equipped to contain the species, and in areas without regional or national pre-entry regulations, post-entry monitoring guidelines and early response programs to address escapee species. Such unregulated transport, trade and rearing of species, compounded by the policy and implementation loopholes at the regional, national and international levels will most likely lead to new biological invasions, as has been witnessed with other unregulated trade practices. To avoid this, it is necessary to monitor and regulate the species to be reared, to improve the quarantine guidelines of the rearing centres, and to be more stringent about the policies and practices that allow movements of non-native species across international borders.
Despite widespread evidence that biological invasion influences both the biotic and abiotic soil environments, the extent to which these two pathways underpin the effects of invasion on plant traits and performance is unknown. Leveraging a long-term (14-yr) field experiment, we show that an allelochemical-producing invader affects plants through biotic mechanisms, altering the soil fungal community composition, with no apparent shifts in soil nutrient availability. Changes in belowground fungal communities result in high costs of nutrient uptake for native perennials and a shift in functional traits linked to their water and nutrient use efficiencies. Some species in the invaded community compensate for high nutrient costs by reducing nutrient uptake and maintaining photosynthesis by expending more water, which demonstrates a trade-off in trait investment. For the first time, we show that the disruption of belowground nutritional symbionts can drive native plants toward novel regions in order to maintain their water and nutrient economics.
Changing environments and habitat structure likely affect eco-evolutionary processes involved in the spatial spread of disease. Exploitative parasites are predicted to evolve in highly connected populations or in expanding epidemics. However, many parasites rely on host dispersal to reach new populations, potentially causing conflict between local transmission and global spread. We performed experimental range expansions in interconnected microcosms of the protozoan Paramecium caudatum, allowing natural dispersal of hosts infected with the bacterial parasite Holospora undulata. Parasites from range front treatments were less virulent and interfered less with host dispersal, but also invested less in horizontal transmission than parasites from range cores. An epidemiological model fitted on experimental time-series data confirmed this trade-off between dispersal adaptation and transmission, so far rarely considered in theoretical models. Our study illustrates the importance of the ecology and evolution of dispersal-related traits in spatial non-equilibrium scenarios, including emerging diseases, metapopulations or biological invasions.
Natural systems are always fluctuating: no two years are identical, with population and community sizes varying from one year to the next. Such variation has led to “equilibrium” becoming almost a dirty word in ecology. Some researchers see the world as being in permanent flux, and consider our field’s historical focus on equilibria as out-dated. But this view is flawed, is driven by current day observations of a world out of kilter, and risks downplaying the risks of ongoing anthropogenic change to civilisation and perhaps too to life on Earth. In this viewpoint, I mount a defence for equilibria.