Steve Wolverton

The global distribution of net primary production: resolving the paradox

The distribution of the diversity and abundance of life on Earth is thought to be shaped by the patterns of plant growth (net primary production, NPP) in the oceans and on land. The well-known latitudinal gradient of species diversity reaches its maximum in tropical rain forests, which are considered to be the most productive ecosystems on the planet. However, this high tropical productivity on land is the opposite of the well-documented distribution of marine productivity, which is greatest in the high-latitude oceans around the poles. This paradox can be resolved by a reevaluation of the terrestrial productivity gradient. Compilations of direct measurements of forest NPP show that annual NPP in tropical forests is no different than annual NPP in temperate forests, contrary to recent syntheses and to the output of global vegetation models. Other properties of forest ecosystems, such as basal area of trees, wood density, and the ratio of wood to leaf production, as well as animal properties such as body size, population density, and reproductive rates, support the conclusion that ecologically relevant terrestrial productivity is actually highest in the temperate latitudes, reaching a maximum between 30° and 50° before declining toward the poles. This “reversal” of the latitudinal productivity gradient, if substantiated by a systematic global sampling effort, will necessitate a major reevaluation of ecological and evolutionary theory, as well as conservation strategies and international development policies.

Regulation of animal size by eNPP, Bergmann's rule and related phenomena

Bergmanns rule, which proposes a heat-balance explanation for the observed latitudinal gradient of increasing animal body size with increasing latitude, has dominated the study of geographic patterns in animal size since it was first proposed in 1847. Several critical reviews have determined that as many as half of the species examined do not fit the predictions of Bergmanns rule. We have proposed an alternative hypothesis for geographic variation in body size based on food availability, as regulated by the net primary production (NPP) of plants, specifically NPP during the growing season, or eNPP (ecologically and evolutionarily relevant NPP). Our hypothesis, “the eNPP rule,” is independent of latitude and predicts both spatial and temporal variation in body size, as well as in total population biomass, population growth rates, individual health, and life history traits of animals, including humans, wherever eNPP varies across appropriate scales of space or time. In the context of a revised interpretat...

The effects of the hypsithermal on prehistoric foraging efficiency in Missouri

Archaeological studies of temporal changes in human predation strategy using foraging theory tend to focus on the role of overexploitation of important prey resources and resulting resource depression. An alternative use of the prey-choice model framed under foraging theory is to investigate the influence of environmental changes, such as increases in climate stress, on prey availability. Environmental change can be expected to produce many of the same effects on human predation strategy as resource depression. Here analytical techniques typically used to study the effects of over-predation and resource depression caused by humans are used to monitor their response to fluctuations in prey availability related to climate change during the Holocene in Missouri. Data and interpretations presented here add to the growing body of zooarchaeological foraging theory literature implicating environmental change as a critical factor in human diet.

HARVEST PRESSURE AND ENVIRONMENTAL CARRYING CAPACITY : AN ORDINAL-SCALE MODEL OF EFFECTS ON UNGULATE PREY

Zooarchaeologists have long realized the analytical potential of ungulate mortality data in studies of temporally shifting foraging efficiency. An additional but seldom examined form of evidence from ungulate remains is the morphometry of age-independent body size. Together simple bivariate morphometric and mortality data from ungulate remains reveal shifts through time in harvest pressure and/or environmental carrying capacity. A proposed model of these effects is validated using wildlife biology data from white-tailed deer (Odocoileus virginianus), an ungulate taxon that is very common in North American archaeological faunas. Several archaeological implications that bear on studies of foraging efficiency in subsistence hunting economies arise from this ordinal-scale model, such as the conditions under which harvest pressure increases or decreases or when carrying capacity rises or declines.

Conformation to Bergmann's Rule in White-tailed Deer can be Explained by Food Availability

Abstract The body size of white-tailed deer (Odocoileus virginianus) increases with latitude and thus exhibits the pattern predicted by Bergmanns rule on the basis of surface to volume ratios and heat loss. This pattern is more simply explained by the distribution of food available per individual animal, which is driven by two factors, the net primary production (NPP) of plants and deer population density. Food availability is often overlooked as a cause of an increase in body size in large terrestrial herbivores in temperate latitudes because of a fundamental misconception about the global distribution of plant productivity. Within a small latitudinal range, white-tailed deer body size as evidenced by modern deer and Holocene paleozoological remains is inversely related to population density and directly related to food availability. Food availability per animal is a product of plant productivity and population density, and is correlated with both local and regional body size variability. These local and regional food-body size patterns are consistent with recent analyses of global NPP datasets which show that ecologically relevant NPP is highest in the north temperate latitudes where white-tailed deer attain their largest body size.

Nisp:Mne and %Whole in Analysis of Prehistoric Carcass Exploitation:

Several analytical problems with the use of utility curves in archaeofaunal analysis have arisen since Lewis Binford first introduced them in 1978. First, do utility curves actually reflect which parts of an animal carcass were chosen or preferred by prehistoric hunters, or do the curves represent transport choices of hunters (what they could carry)? Second, differential preservation of elements mediated by bone density also contributes to what bones archaeologists recover from sites. Density-mediated destruction of bone can produce curves that mimic those of human behavior; thus, inferences about human behavior might be better attributed to bone-preservation factors. A shift from use of prey body-part representation to the use of fragmentation of prey bones as an inferential tool to study prehistoric foraging of prey carcasses diminishes both analytical problems.

A paleozoological perspective on unionid (Mollusca: Unionidae) zoogeography in the upper Trinity River basin, Texas

In north central Texas, USA, the zoogeography of unionids in the Trinity River is thought to consist of upland and lowland biogeographic components reflective of differences in upstream and downstream hydraulic conditions. Historical and modern surveys from a limited number of localities were used to delineate these zoogeographic provinces based on the absence of several species thought to occur only in the lower Trinity River drainage. Available zooarchaeological data indicate that at least one species considered absent from the upper Trinity River basin was present during the late Holocene (roughly the last 2500 years), suggesting that both biogeographical provinces shared similar mussel fauna in the recent geological past. The discrepancy between historical and zooarchaeological data is probably the result of inadequate sampling and of an extirpation gradient related to impoundments that have been constructed in this drainage during the last century. The presence of lower Trinity species during the late Holocene in the upper Trinity drainage challenges interpretations drawn from modern biogeographic studies.

ETHNOBIOLOGY, POLITICAL ECOLOGY, AND CONSERVATION

Abstract Ethnobiology is increasingly recognized from within and outside of its boundaries as interdisciplinary. The Society of Ethnobiology defines the field as “the scientific study of dynamic relationships among peoples, biota, and environments.” Ethnobiologists are able to skillfully assess challenges of biocultural conservation across the divides of political ecology. They are situated to mediate between conservation programs that target biodiversity preservation with little concern for the needs of human communities, and those (such as the New Conservation movement) that privilege those needs. Ethnobiology also transcends the pervasive assumption in these fields that Western knowledge and economic goals should guide change. Because of ethnobiologys importance as a bridging discipline, it is important to ask what unifies ethnobiology. Is it common subject matter? Or, is there an underlying emphasis representing an “ethnobiological perspective?” Answers to these questions are explored here using content analysis and discourse-and-ideology analysis. We use the results to identify the unique roles ethnobiologists play in biocultural conservation. This analysis also proved useful in the systematic identification of four salient themes that unify ethnobiology—ethics in ethnobiology, shared environmental and cultural heritage, interdisciplinary science and non-science, and ecological understanding. How ethnobiologists conceive of themselves is critical for further enrichment of the field as interdisciplinary human-environmental scholarship, particularly in reference to biocultural conservation. Self-definition makes explicit the unique strengths of the field, which by its very nature integrates a sophisticated understanding of political ecology with appreciation of the value of traditional ecological knowledge (TEK), social science, and the biological sciences.

The Terminal Pleistocene Extinctions in North America, Hypermorphic Evolution, and the Dynamic Equilibrium Model

Abstract The cause of megafaunal extinctions at the end of the last glaciation has been hotly debated during the last few decades, most recently at the global scale. In North America and elsewhere the debate centers on whether or not human hunters, who seemingly first entered the continent during the extinction period, caused the extinctions through over-hunting. An alternative explanation is that climate change during the terminal Pleistocene radically modified existing habitats and this caused the extinctions. Hustons (1979, 1994) dynamic equilibrium model (DEM) of community species richness provides a theoretical context for explanations of the extinctions in North America and highlights life history characteristics of extinct mammals. These life history traits and associated phenotypes are a seldom-explored line of evidence concerning the causes of the extinctions. In light of life history traits, environmental disturbance is implicated as the proximate cause of the extinctions, but the DEM does not preclude overkill as a contributing cause in North America.

Immanence and Configuration in Analogical Reasoning

The role of analogical reasoning has been extensively discussed by American archaeologists. Geologists and evolutionary biologists suggest two kinds of analogy are necessary in historical science. The distinction between immanent and configurational properties and processes in these affinal disciplines clarifies the role of analogical reasoning in archaeology. Examples of archaeological analogies reveals conflation of the two kinds of processes and properties. Distinction between immanence and configuration provides a basis to identify the potentials and pitfalls of analogical reasoning in archaeology.