To understand resource partitioning, essentially a community phenomenon, we require a holistic theory that draws upon models at the individual and population level. Yet some investigators are still content mainly to document differences between species, a procedure of only limited interest. Therefore, it may be useful to conclude with a list of questions appropriate for studies of resource partitioning, questions this article has related to the theory in a preliminary way. 1) What is the mechanism of competition? What is the relative importance of predation? Are differences likely to be caused by pressures toward reproductive isolation? 2) Are niches (utilizations) regularly spaced along a single dimension? 3) How many dimensions are important, and is there a tendency for more dimensions to be added as species number increases? 4) Is dimensional separation complementary? 5) Which dimensions are utilized, how do they rank in importance, and why? How do particular dimensions change in rank as species nuimber increases? 6) What is the relation of dimensional separation to difference in phenotypic indicators? To what extent does the functional relation of phenotype to resource characteristics constrain partitioning? 7) What is the distance between mean position of niches, what is the niche standard deviation, and what is the ratio of the two? What is the niche shape?

https://science.sciencemag.org/content/sci/185/4145/27.full.pdf

Resource Partitioning in Ecological Communities

A new hypothesis, based on differences in the rates at which populations of competing species approach competitive equilibrium (reduction or exclusion of some species), is proposed to explain patte...

A General Hypothesis of Species Diversity

It is often claimed that we do not understand the forces driving the global diversity gradient. However, an extensive literature suggests that contemporary climate constrains terrestrial taxonomic richness over broad geographic extents. Here, we review the empirical literature to examine the nature and form of the relationship between climate and richness. Our goals were to document the support for the climatically based energy hypothesis, and within the constraints imposed by correlative analyses, to evaluate two versions of the hypothesis: the productivity and ambient energy hypotheses. Focusing on studies extending over 800 km, we found that measures of energy, water, or water-energy balance explain spatial variation in richness better than other climatic and non-climatic variables in 82 of 85 cases. Even when considered individually and in isolation, water/ energy variables explain on average over 60% of the variation in the richness of a wide range of plant and animal groups. Further, water variables usually represent the strongest predictors in the tropics, subtropics, and warm temperate zones, whereas energy variables (for animals) or water-energy variables (for plants) dominate in high latitudes. We conclude that the interaction between water and energy, either directly or indirectly (via plant productivity), provides a strong explanation for globally extensive plant and animal diversity gradients, but for animals there also is a latitudinal shift in the relative importance of ambient energy vs. water moving from the poles to the equator. Although contemporary climate is not the only factor influencing species richness and may not explain the diversity pattern for all taxonomic groups, it is clear that understanding water-energy dynamics is critical to future biodiversity research. Analyses that do not include water-energy variables are missing a key component for explaining broad-scale patterns of diversity.

/pdf/energy-water-and-broad-scale-geographic-patterns-of-species-4muvqfsaj0.pdf

Energy, water, and broad-scale geographic patterns of species richness

▪ Abstract The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas f...

LATITUDINAL GRADIENTS OF BIODIVERSITY:Pattern,Process,Scale,and Synthesis

Null models in ecology

Hydrothermal vents jetting out water at 380° ± 30°C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galapagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.

https://science.sciencemag.org/content/sci/207/4438/1421.full.pdf

East Pacific Rise: Hot Springs and Geophysical Experiments

Role of biological disturbance in maintaining diversity in the deep sea

LATITUDINAL gradients of species diversity are ubiquitous features of terrestrial and coastal marine biotas, and they have inspired the development of theoretical ecology1–3. Since the discovery of high species diversity in the deep-sea benthos4, much has been learned about local5,6and regional7–9patterns of diversity. Variation in diversity on larger scales remains poorly described. Latitudinal gradients of diversity were unexpected because it was assumed that the environmental gradients that cause large-scale patterns in surface environments could not affect communities living at great depths10. Here we report that deep-sea bivalves, gastropods and isopods show clear latitudinal diversity gradients in the North Atlantic, and strong interregional variation in the South Atlantic. Many seemingly incompatible mechanisms have been proposed to explain deep-sea species diversity11. The existence of regular global patterns suggests that these mechanisms operate at different spatial and temporal scales.

Global-scale latitudinal patterns of species diversity in the deep-sea benthos

Abyssal community analysis from replicate box cores in the central North Pacific

https://science.sciencemag.org/content/sci/163/3874/1419.full.pdf

Robert R. Hessler

Papers

East Pacific Rise: Hot Springs and Geophysical Experiments

Role of biological disturbance in maintaining diversity in the deep sea

Global-scale latitudinal patterns of species diversity in the deep-sea benthos

Abyssal community analysis from replicate box cores in the central North Pacific

Ecology of the deep-sea benthos.