Species-energy Relationships Research Articles

Retail rings of influence: Rethinking retail catchment analysis in the light of purchasing power

Catchment areas are vital indicators of purchasing power that significantly influence the retail sales of shopping malls. However, conventional models, typically provided by mall owners, often assume a fixed isochrone, neglecting the sensitivity of the catchment size on mall's positioning strategies and sizes. This study introduces a novel, flexible approach, leveraging the population and household incomes of administrative units as a proxy for purchasing power, thereby enabling a sensitivity analysis on adjustable catchment sizes. We develop a Python programme to geofence these units based on an adjustable isochrone radius. This pioneering research also applies principles from the species-energy relationship and niche specialisation theory to build a theoretical model of catchment areas, empirically testing it using Australian data. Our findings confirm that while purchasing power within varying catchment sizes exerts a positive influence on retail sales, the impact is less pronounced for larger malls due to their more generalised niche in attracting customers far away from the malls. This study sheds new light on the dynamic interplay between catchment area characteristics and mall performance, offering valuable insights for future research and retail strategy planning.

Disentangling mechanisms of species–energy relationships in experimental deep‐sea wood falls

AbstractA multitude of hypotheses have been invoked to explain increases in richness with increases in energy availability. Experiments have the potential to reveal causality, and species–energy experiments have yielded substantial insights into energetic community assembly. Here, we examine six mechanisms underlying species–energy relationships in an experimental wood fall system in the deep Gulf of Mexico. Twenty‐four wood falls were deployed in the deep Gulf of Mexico for 21 months. To test for differences in total energy availability, individual wood falls ranged in size from 0.91 to 24 kg, corresponding to different levels of energy available to the wood‐obligate invertebrate communities assembling on wood falls. To test for differences in total energy accessibility, we chose a softwood (pine, n = 12) and soft hardwood (sugarberry, n = 12). Structural equation models were used to disentangle the multiple hypothesized pathways by which changes in wood fall type and mass correlated with richness. Whereas we find support for the more individuals hypothesis, we also find that niche dynamics and competition play important roles as well linking energy and diversity. Furthermore, we find that not only the total energy but also the accessibility of that energy, dictating rates of energy flow, leads to differences in community structure. Using structural equation modeling (SEM), we evaluate seven hypotheses to demonstrate that no single hypotheses alone can predict the species–energy relationship.

More individuals or specialized niches? Distinguishing support for hypotheses explaining positive species–energy relationships

AbstractAimPositive productivity–richness relationships have been observed across taxa and ecosystems. We assessed support for two hypotheses explaining these relationships, the More Individuals Hypothesis (MIH) and the Niche Specialization Hypothesis (NSH) in two complementary datasets of avian communities in North America, the Breeding Bird Survey (BBS), which has been widely used to study productivity–richness relationships, and the Breeding Bird Census (BBC), which has been used rarely yet offers accurate population density estimates and more homogeneous landscapes, eliminating confounding variables that may make it more difficult to test predictions of the NSH and MIH in the BBS alone.LocationCoterminous United States, 1988–2009.TaxonBirds.MethodsWe first evaluated the strength of productivity–richness relationships in the BBS and BBC, and tested predictions from the MIH and NSH in the two datasets by examining patterns in community abundance, productivity niche breadth and number of foraging guilds along a gradient of normalized difference vegetation index (a measure of vegetation productivity). We also implemented a null model to examine the contribution of sampling effects due to increasing species richness in explaining patterns in number of foraging guilds in both datasets.ResultsWe found that the BBS had a much stronger productivity–richness relationship than the BBC, potentially as a result of increased landscape diversity with increasing productivity at BBS survey sites. Although the MIH and NSH may not be mutually exclusive, we found weaker support for the MIH in the BBC, and stronger support for the NSH in the BBC and BBS.Main ConclusionsResearchers should consider the role of confounding variables such as landscape diversity and focus on developing direct measurements of food resources at macroecological scales to determine the relative importance of mechanisms driving productivity–richness relationships.

Water and energy availability mediate biodiversity patterns along an elevational gradient in the tropical Andes

AbstractAimHow tree taxonomic and phylogenetic diversity vary with elevation at multiple spatial scales may provide new insights into the ecological and evolutionary processes influencing biogeographical patterns. The effect of water‐ and energy‐related climatic variables on forests diversity across elevations, as well as how clades have evolved on and established across mountain regions lack consensus. Here, we tested whether changes in biodiversity with elevation are consistent with one of, or multiple, competing hypotheses: the water–energy dynamics (WED), species–energy relationship (SER), Tropical Niche Conservatism (TNC) and Out of The Tropics hypothesis (OTT).LocationPatia watershed, ColombiaTaxonSeed plants (trees)MethodsWe used a large dataset of 490 0.1 ha forest plots in nine elevational belts (545–3410 m a.s.l) that correspond to three different life zones, and quantified alpha and gamma scales using taxonomic and phylogenetic diversity indices. We fitted linear mixed‐effects models to evaluate how taxonomic and phylogenetic alpha diversity changed with elevation, precipitation and aboveground biomass. We assessed taxonomic and phylogenetic beta diversity using the Sørensen index and its spatial turnover and nestedness components.ResultsTaxonomic and phylogenetic alpha diversity decrease with elevation. Yet, at the gamma scale, taxonomic and phylogenetic diversity predominantly increased with elevation. Taxonomic and phylogenetic beta diversity were strongly influenced by species turnover, and followed a hump‐shaped pattern with elevation.Main conclusionsOverall, diversity shows a decreasing trend at the local scale, while coarse‐scale gamma diversity followed a pattern of nonlinear increases for both taxonomic and phylogenetic diversity. Evidence supports the influence of SER and WED on diversity patterns across elevations, yet neither evolutionary hypotheses had sufficient empirical support to be conclusive.

Towards an integrative understanding of soil biodiversity.

ABSTRACTSoil is one of the most biodiverse terrestrial habitats. Yet, we lack an integrative conceptual framework for understanding the patterns and mechanisms driving soil biodiversity. One of the underlying reasons for our poor understanding of soil biodiversity patterns relates to whether key biodiversity theories (historically developed for aboveground and aquatic organisms) are applicable to patterns of soil biodiversity. Here, we present a systematic literature review to investigate whether and how key biodiversity theories (species–energy relationship, theory of island biogeography, metacommunity theory, niche theory and neutral theory) can explain observed patterns of soil biodiversity. We then discuss two spatial compartments nested within soil at which biodiversity theories can be applied to acknowledge the scale‐dependent nature of soil biodiversity.

Species-energy relationships of indigenous and invasive species may arise in different ways \u2013 a demonstration using springtails

Although the relationship between species richness and available energy is well established for a range of spatial scales, exploration of the plausible underlying explanations for this relationship is less common. Speciation, extinction, dispersal and environmental filters all play a role. Here we make use of replicated elevational transects and the insights offered by comparing indigenous and invasive species to test four proximal mechanisms that have been offered to explain relationships between energy availability, abundance and species richness: the sampling mechanism (a null expectation), and the more individuals, dynamic equilibrium and range limitation mechanisms. We also briefly consider the time for speciation mechanism. We do so for springtails on sub-Antarctic Marion Island. Relationships between energy availability and species richness are stronger for invasive than indigenous species, with geometric constraints and area variation playing minor roles. We reject the sampling and more individuals mechanisms, but show that dynamic equilibrium and range limitation are plausible mechanisms underlying these gradients, especially for invasive species. Time for speciation cannot be ruled out as contributing to richness variation in the indigenous species. Differences between the indigenous and invasive species highlight the ways in which deconstruction of richness gradients may usefully inform investigations of the mechanisms underlying them. They also point to the importance of population size-related mechanisms in accounting for such variation. In the context of the sub-Antarctic our findings suggest that warming climates may favour invasive over indigenous species in the context of changes to elevational distributions, a situation found for vascular plants, and predicted for springtails on the basis of smaller-scale manipulative field experiments.

Primary productivity and habitat diversity predict bird species richness and composition along urban-rural gradients of central Argentina

Although the role of primary productivity and habitat diversity in determining patterns of species richness and composition have been explored in urban areas, they have been rarely analysed in the context of species-energy relationships (SERs). Therefore, two hypotheses related to SERs were tested in bird communities: the more individuals hypothesis (MIH) and the niche position hypothesis (NPH). The MIH states that sites with more energy availability have more individuals, with extinction probability decreased thereby increasing the species richness. The NPH predicts that the amount of rare resources increases at sites with greater energy availability and environmental heterogeneity, increasing species richness. Birds were counted along three urban-rural gradients in the Pampas region of Argentina during the breeding season. Productive energy was measured using the NDVI and environmental heterogeneity via the diversity of different substrates. Although there was a positive relationship between bird richness and abundance, there was no positive relationship between bird abundance and primary productivity. Bird richness showed a positive relationship with habitat diversity and primary productivity, supporting the NPH. The exclusion of exotic species resulted in a tight relationship between bird richness and abundance, and between bird abundance and primary productivity, supporting the MIH. Bird composition varied with changes in habitat diversity and primary productivity. Path analysis revealed that habitat diversity increased bird richness through an increase of bird abundance. The NPH was the most consistent to predict bird richness along urban-rural gradients. Therefore, it is necessary to create areas with greater amount and variety of vegetation to increase bird richness.

Debunking paradigms in estuarine fish species richness

The comparison of species complements within and between habitats and geographical areas is a fundamental aspect of ecological assessments. However, many influences resulting from variability in sampling and data analysis often hinder the ability to determine important patterns in community structure. The study is based on the hypothesis that using a standard sampling method, an asymptote in the rarefaction curve represents the total (gear-specific) species complement likely to be encountered for the geographical area. Accordingly, an asymptotic species richness estimator was used to predict the full complement of species present within each estuary that could be caught using seine netting. The rarefaction curves and species richness estimator enable the interrogation of two underlying paradigms of ecological species richness: the species-energy relationship and the species-area relationship. This analysis reveals distinct groups which show a significant relationship with latitude and size, although the size effect has a smaller influence. In particular, the species-latitude relationship paradigm holds true in this study while the species-area relationship paradigm only applies when latitude is considered concomitantly. Marine species in particular appear to account for the increased fish species number at lower latitudes. The underlying influence of latitude and estuary size suggests that any managerial tool that explores anthropogenic impacts (such as those used in the European Water Framework Directive) should include these aspects. It is concluded that the analysis gives environmental managers an objective cost-beneficial method of identifying when and where further sampling does not give further information for management.

Species richness of polypores can be increased by supplementing dead wood resource into a boreal forest landscape

Abstract To prevent local species extinction and to counteract population declines, we must ensure species have access to resources they require for life. This can be done through ecological restoration where previously depleted resources are reintroduced. If the restoration is conducted as a one‐off action in a large area, it resembles a natural resource pulse, which should lead to increased abundance of individuals, accompanied possibly by increased species richness. Species–energy relationship and underlying theory enable predictions about how different features of resource pulses affect species richness. We conducted a large‐scale, controlled, randomized and replicated field experiment to study the effect of a resource addition on polypore species richness in a previously managed boreal forest landscape in Finland. We manipulated the amount and distribution of dead wood and studied the effects on polypore assemblages on added and natural dead wood during 9 years after manipulation (2004–2012). By adding dead wood, species richness grew, mainly through increasing abundances: a large amount of dead wood resulted in higher abundance, higher number and faster accumulation of species than a small amount of dead wood. For a given abundance, dead wood addition contained fewer species than natural dead wood. This is most probably because added dead wood was of low diversity and provided habitat only for a limited number of species. Species richness on natural dead wood increased substantially during the study period, and this increase was not related to the resource manipulation. Thus, habitat improvement through natural succession can occur within a relatively short time period irrespective of human intervention. Synthesis and applications. We demonstrate how the introduction of dead wood additions can strengthen polypore populations. The species taking advance of the introduced resource were primarily common species, instead of rare or red‐listed species. Thus, we recommend ensuring the natural formation of dead wood while the populations of the common species supporting ecosystem functions can be increased by adding dead wood in the landscape.

Patterns of landscape seasonality influence passerine diversity: Implications for conservation management under global change

The importance of environmental heterogeneity for biodiversity across scales is widely recognized in ecological theory and profusely supported by evidence. However, our understanding of the effects of spatiotemporal patterns of landscape functional properties on biodiversity is still rather limited. We examined the relationship between common passerine species richness and ecosystem functioning dynamics, namely seasonality, measured by satellite remote sensing. We focused on rural landscapes of a mountain National Park in Portugal undergoing rapid reshaping from agro-pastoral mosaics to early successional landscapes. We applied multi-model inference to compare the hypothesis of landscape seasonality as a driver of species richness with three competing hypotheses representing structural habitat heterogeneity, disturbance, and availability of food resources. We found support for landscape seasonality and its spatial heterogeneity in explaining passerine richness in mountain rural landscapes. Conversely, no significant support of the remaining hypotheses was found. These results highlight the role of ecosystem functioning variability in space and time. They also stress the importance of considering species-energy relationships for conservation at the landscape level. Specifically, they provide support and guidance to the identification of meaningful functional attributes of the landscape that shape its biodiversity. Our results further demonstrate the utility of remote sensing approaches and products to measure those attributes and follow their trends through time. Spatially-explicit measures of energy variability, such as the functional amplitude between winter and summer retrieved from earth observations, can link global socio-environmental change to species’ responses and support the inclusion of landscape seasonality on conservation and monitoring frameworks.

The prevalence and impact of transient species in ecological communities.

Transient species occur infrequently in a community over time and do not maintain viable local populations. Because transient species interact differently than non-transients with their biotic and abiotic environment, it is important to characterize the prevalence of these species and how they impact our understanding of ecological systems. We quantified the prevalence and impact of transient species in communities using data on over 19,000 community time series spanning an array of ecosystems, taxonomic groups, and spatial scales. We found that transient species are a general feature of communities regardless of taxa or ecosystem. The proportion of these species decreases with increasing spatial scale leading to a need to control for scale in comparative work. Removing transient species from analyses influences the form of a suite of commonly studied ecological patterns including species-abundance distributions, species-energy relationships, species-area relationships, and temporal turnover. Careful consideration should be given to whether transient species are included in analyses depending on the theoretical and practical relevance of these species for the question being studied.

Energy efficiency drives the global seasonal distribution of birds.

The uneven distribution of biodiversity on Earth is one of the most general and puzzling patterns in ecology. Many hypotheses have been proposed to explain it, based on evolutionary processes or on constraints related to geography and energy. However, previous studies investigating these hypotheses have been largely descriptive due to the logistical difficulties of conducting controlled experiments on such large geographical scales. Here, we use bird migration-the seasonal redistribution of approximately 15% of bird species across the world-as a natural experiment for testing the species-energy relationship, the hypothesis that animal diversity is driven by energetic constraints. We develop a mechanistic model of bird distributions across the world, and across seasons, based on simple ecological and energetic principles. Using this model, we show that bird species distributions optimize the balance between energy acquisition and energy expenditure while taking into account competition with other species. These findings support, and provide a mechanistic explanation for, the species-energy relationship. The findings also provide a general explanation of migration as a mechanism that allows birds to optimize their energy budget in the face of seasonality and competition. Finally, our mechanistic model provides a tool for predicting how ecosystems will respond to global anthropogenic change.

The more-individuals hypothesis revisited: the role of community abundance in species richness regulation and the productivity-diversity relationship.

Species richness increases with energy availability, yet there is little consensus as to the exact processes driving this species-energy relationship. The most straightforward explanation is the more-individuals hypothesis (MIH). It states that higher energy availability promotes a higher total number of individuals in a community, which consequently increases species richness by allowing for a greater number of species with viable populations. Empirical support for the MIH is mixed, partially due to the lack of proper formalisation of the MIH and consequent confusion as to its exact predictions. Here, we review the evidence of the MIH and evaluate the reliability of various predictions that have been tested. There is only limited evidence that spatial variation in species richness is driven by variation in the total number of individuals. There are also problems with measures of energy availability, with scale-dependence, and with the direction of causality, as the total number of individuals may sometimes itself be driven by the number of species. However, even in such a case the total number of individuals may be involved in diversity regulation. We propose a formal theory that encompasses these processes, clarifying how the different factors affecting diversity dynamics can be disentangled.

Tree growth indicates resource quality for foliage-feeding insects: Pattern and structure of herbivore diversity in response to productivity

In forests, local site conditions can affect both trees and herbivores and hence site-related factors act indirectly on herbivores mediated by tree growth rates. Here, tree foliage represents a fundamental prerequisite for insect herbivore development providing energy in the form of plant tissue quality. Resource-based theories, on the other hand, assume that the synthesis of defensive compounds is a trade-off with growth and peaks at low resource availability. However, the extent to which plant tissue quality in response to site productivity is relevant in the species-energy relationship is unknown. Therefore, we aimed at a better understanding of the form and structure of the species-energy relationship in forest insects. We used census data of foliage-feeding insects along a productivity gradient of Scots pine forests defined by relative growth rates of trees (RGR). As a result, diversity monotonically increases with decreasing RGR (as a proxy for energy) during almost two decades of sampling. Herbivore assemblages become more similar with available energy as species turnover linearly decreases and proportions of sites occupied by individual species rise. The results suggest that tree growth rate influences herbivore dynamics in this system by altering the chemical composition of needles, without necessarily affecting the form in the relationship. The site-specific resource availability requires trees to adjust their allocation to synthesis of carbon-based secondary metabolites or growth, which then results in fundamental differences in herbivore dynamics at low vs. lowest RGR (regular cycles (dominance) vs. dampened cycles (evenness)). However, these differences inevitably demonstrate that species richness is not necessarily a result of more individuals and implicate that different mechanisms are involved (facilitation vs. competition/temporal heterogeneity). The resulting pattern and structure of foliage-feeding insects advance our understanding of herbivore dynamics in response to site quality and tree growth, which may ultimately improve our knowledge of plant-insect interactions in the face of environmental change.

Trade-offs between microbiome diversity and productivity in a stratified microbial mat.

Productivity is a major determinant of ecosystem diversity. Microbial ecosystems are the most diverse on the planet yet very few relationships between diversity and productivity have been reported as compared with macro-ecological studies. Here we evaluated the spatial relationships of productivity and microbiome diversity in a laboratory-cultivated photosynthetic mat. The goal was to determine how spatial diversification of microorganisms drives localized carbon and energy acquisition rates. We measured sub-millimeter depth profiles of net primary productivity and gross oxygenic photosynthesis in the context of the localized microenvironment and community structure, and observed negative correlations between species richness and productivity within the energy-replete, photic zone. Variations between localized community structures were associated with distinct taxa as well as environmental profiles describing a continuum of biological niches. Spatial regions in the photic zone corresponding to high primary productivity and photosynthesis rates had relatively low-species richness and high evenness. Hence, this system exhibited negative species-productivity and species-energy relationships. These negative relationships may be indicative of stratified, light-driven microbial ecosystems that are able to be the most productive with a relatively smaller, even distributions of species that specialize within photic zones.

A macroecological perspective on strategic bat conservation in the U.S. National Park Service

AbstractNorth American bat populations face unprecedented threats from disease and rapid environmental change, requiring a commensurate strategic conservation response. Protected‐area networks have tremendous potential to support coordinated resource protection, disease surveillance, and population monitoring that could become a cornerstone of 21st‐century bat conservation. To motivate this idea, we develop a macroecological perspective about bat diversity and associated conservation challenges and opportunities on U.S. National Park Service (NPS) lands. We compared occurrence records from parks against published range maps. Only 55 (19%) of parks reported as present ≥90% of the bat species expected based on range maps, highlighting the information‐gap challenge. Discrepancies suggest substantial under‐reporting and under‐sampling of bats on NPS lands; inadequate range maps and habitat specificity are implicated for some species. Despite these discrepancies, 50 species, including several range‐restricted and endangered taxa, were reported in at least one park unit, including those in the Caribbean and tropical Pacific. Species richness increased with park area at a rate (z) of ~0.1, a pattern confounded by covariation with latitude, elevation, and habitat. When accounting for these factors, richness decreased predictably at higher latitudes and increased at mid‐elevations and with greater numbers of keystone underground habitat structures (caves and mines), reflecting a strong species–energy relationship. The inclusion of covariates that represented percentage of natural vs. human‐modified (converted) landscapes and elevation range—a proxy for environmental heterogeneity—was uninformative. White‐nose syndrome (WNS) presents a tremendous challenge to the NPS: All 12 species currently known to be affected by the disease or to host the causal fungus are represented in the NPS system. One hundred and twenty‐seven NPS parks are in counties currently or likely to become WNS‐positive by 2026. All parks are expected to experience increasing temperatures in coming decades; forecasted climate change velocity is particularly high (>1 SD) for 50 parks. Seventeen parks are in the vicinity of high (>1 SD) wind turbine density. Based on these biogeographic patterns, we suggest ways to prioritize NPS parks for additional inventories, monitoring, and resource protection. Our results demonstrate how macroecology and bioinformatics together can guide strategic conservation capacity‐building among protected areas.

Temperature and food constraints in wintering birds — an experimental approach in montane Mediterranean oakwoods

Although energy is a major driver of global patterns of biodiversity and species distribution, the test of species-energy relationships needs further development using fine-grained approaches involving different functional groups of species and small geographical scales of known characteristics (habitat heterogeneity, food availability, direct measures of temperature). We carried out an experiment over a broad range of habitat structure and environmental conditions to disentangle the effects of two different energy measures on the small-scale variation of habitat use in winter: one directly related to food resources (manipulated food availability with artificial feeders), and another related to thermoregulatory costs (night temperature). The spatial variation in abundance of a guild of tree-gleaning birds wintering in montane Mediterranean oakwoods of Central Spain was positively related to both components of energy availability (temperature and food resources), even in these mild Mediterranean montane forest of southern Europe. Spatial variation in consumption of food from artificial feeders was negatively related to spatial variation in temperature. The influence of food availability on bird abundance was mediated by vegetation structure, with a lower influence in maturer oakwoods. This study highlights the important role of the energy-related factors, over habitat structure, in determining winter abundance of the studied tree-gleaning guild.

Thermal, food and vegetation effects on winter bird species richness of Mediterranean oakwoods

AbstractA better understanding of species–energy relationships needs to be developed using fine‐grained approaches that involve the use of small geographical scales of known characteristics, such as habitat heterogeneity, food availability, direct measures of temperature, and functional groups of species. We carried out a 2‐year study to analyze the effects of the thermal environment and food availability, while controlling for the influence of habitat structure, on winter species richness of birds living in oakwoods of a mountanious region of Central Spain of Mediterranean continental climate. The guild of ground‐foraging birds was selected as model organisms considering its susceptibility to winter conditions associated with unpredictable snowfalls. The spatial variation in species richness of this guild was determined by food availability, but only for those stable and predictable resources not affected by frequent snowfall (shrubs producing fruits; a complete lack of association was found with arthropod abundance on the ground). Thermal effects associated directly with air temperature, and mediated indirectly by vegetation structure providing a mosaic of sun‐shade patches, were also very influential. These patterns were highly repeatable across years. Daytime temperature had no influence on determining spatial variation in species richness, but night (minimum) temperature was a very important predictor (explained considering the lower temperatures at night, the longer duration of night, and the inability of diurnal birds to develop active behavioral thermoregulation during nighttime). This result highlights the need to consider physiological processes mediating species–environment relationships when analyzing the relationship between climatic variables and biodiversity phenomena.

Habitat specificity can blur the predictions of species–energy theory: A case study of tenebrionid beetles adapted to aridity

Species–energy theory predicts a positive relationship between species richness and energy. The mechanism assumed by this theory is that high energy promotes high population abundance, which in turn promotes high species richness. Evaluations of this mechanism have rendered conflicting evidence, suggesting that more effort is needed to understand the theory’s limitations. Several studies have addressed these limitations, contributing to expand the theory’s scope by incorporating energy variation, whereas others have demonstrated scale dependence of the more individuals hypothesis. We propose that another limitation of this theory is related to its application to groups of species with strong habitat specificity. We suggest that the expected relationship between energy and richness is not necessarily positive at large scales for groups of species adapted to harsh environments. Using data on tenebrionid beetles from arid areas of southern South America, we contrasted four hypotheses that lead to contrasting predictions about the strength and direction of the species–energy relationship on tenebrionid richness. We found a negative relationship between richness and energy availability. We propose that this negative relationship is the result of a constraint in the mechanisms assumed by species−energy theory because organisms evolve adaptations to survive climatic harshness, which influences population abundances.

Species–energy relationships in deep-sea molluscs

Consensus is growing among ecologists that energy and the factors influencing its utilization can play overarching roles in regulating large-scale patterns of biodiversity. The deep sea--the world's largest ecosystem--has simplified energetic inputs and thus provides an excellent opportunity to study how these processes structure spatial diversity patterns. Two factors influencing energy availability and use are chemical (productive) and thermal energy, here represented as seafloor particulate organic carbon (POC) flux and temperature. We related regional patterns of benthic molluscan diversity in the North Atlantic to these factors, to conduct an explicit test of species-energy relationships in the modern day fauna of the deep ocean. Spatial regression analyses in a model-averaging framework indicated that POC flux had a substantially higher relative importance than temperature for both gastropods and protobranch bivalves, although high correlations between variables prevented definitive interpretation. This contrasts with recent research on temporal variation in fossil diversity from deep-sea cores, where temperature is generally a more significant predictor. These differences may reflect the scales of time and space at which productivity and temperature operate, or differences in body size; but both lines of evidence implicate processes influencing energy utilization as major determinants of deep-sea species diversity.