bluuebunny/crossref_metadata_2025 huggingface dataset:
Opportunities in Farm Management: Discussion/Challenge
Authors: Hanson Gregory D.
Published: July 2016

The role of cognitive science as presented by Black offers an in-depth treatment of the current agricultural information processing and interpretation revolution and the contributions of other disciplines, ranging from engineering and psychology, finance and medicine, to the science of decisionmaking in agriculture. Certainly, many farm management economists will find the issues of information reception, styles of thinking, systems science approaches, biological pathways in modeling, psychological types, and other cognitive science issues raised in this session to be important and useful in the context of both basic and applied research. Agricultural economists are again reminded of the need to integrate approaches across models, the payoff to alternative degrees of approximating reality and the usefulness of a better balance in the portfolio of microcomputer activities.
Use of Biophysical Simulation in Production Economics
Authors: Musser Wesley N. , Tew Bernard V.
Published: July 2016

Simulation has become a standard methodology in agricultural economics with models being used in all aspects of the profession. Johnson and Rausser identify two major types of production simulation models in their recent survey of the topic—firm and process models. Firm models, especially those concerned with growth, are most prominent in the agricultural economics literature. However, Johnson and Rausser also review some application of process models, which emphasize specific types of firm decisions. Biophysical simulation models are a specific form of these models concerned with the interaction of weather, soil, and/or biological processes in agricultural production and/or environmental loadings. In the recent agricultural economics literature, these models often are identified as bio-economic simulators. However, similar models are being utilized to evaluate erosion. Since erosion is largely a physical process, biophysical simulation seems more appropriate for the general classification of models considered in this paper.
Estimating Returns to Agricultural Research, Extension, and Teaching at the State Level
Authors: Norton George W. , Coffey Joseph D. , Frye E. Berrier
Published: July 2016

The majority of decisions concerning investment and allocation of public funds for agricultural research, extension, and teaching (RET) are made at the state-level, while most of the quantitative RET evaluations are made on a national basis. This paper illustrates an approach for conducting a disaggregated state-level evaluation of agricultural research, extension, and teaching. Ridge regression is employed to handle multicollinearity problems.
The Effects of the 1980, 1981, and 1982 Tax Laws on Texas Rice Farmers
Authors: Richardson James W. , Nixon Clair J.
Published: July 2016

A whole farm Monte Carlo simulation model was used to simulate a typical rice farm on the Texas Gulf Coast for 10 years under the 1980, 1981, and 1982 income tax provisions. Results for this analysis indicate that the 1981 tax provisions clearly were more beneficial to farm operators than the 1980 or 1982 income tax provisions. While the 1981 and 1982 tax law changes clearly improved the cash flow of farm operators, they did not greatly improve the wealth positions of farm operators in the Texas Gulf Coast.
A Translog Cost Analysis of Turkey Production in the Mid-Atlantic Region
Authors: Grisley William , Gitu Kangethe W.
Published: July 2016

The production structure of 165-hen and 200-tom turkey flocks is investigated using a translog (dual) variable cost function. The partial static equilibrium elasticities of scale, input demand, input substitution, and cross price elasticities of demand are calculated. The elasticity of scale is found to be not significantly different from one over the range of 5,900 to 9,822 birds for the hen flocks and over the range of 7,765 to 11,043 birds for the torn flocks. In general, the input demand elasticities are inelastic with the exception of the input fuel. The cross-price elasticities are in general inelastic.
The Market Value of Ingress Rights for White-Tailed Deer Hunting in Texas
Authors: Pope C. Arden , Stoll John R.
Published: July 2016

The lease hunting system in Texas is described and discussed. Results of a hunter survey are reported and the value of ingress rights for white-tailed deer hunting in Texas is estimated. Results suggest that these rights are highly valuable and that services and facilities provided generally do not enhance the value of the hunting experience as much as access to additional game species on adequately large parcels of land.
Regional Cotton Acreage Response
Authors: Duffy Patricia A. , Richardson James W. , Wohlgenant Michael K.
Published: July 2016

An econometric model of cotton acreage response was estimated for four distinct production regions in the United States. This work builds on previous work in the area of supply response under government farm programs and provides up-to-date regionalized estimates of own-price elasticity of cotton acreage supply. The own-price variable used in this study is a weighted combination of expected market price and government policy variables. Results indicate regional similarity in response to own price but differences with respect to the prices of alternative enterprises. Differences in regional response to paid diversion are also indicated.
Rationality, Price Risk, and Response
Authors: Seale James L. , Shonkwiler J. S.
Published: July 2016

Risk has long been recognized as potentially important in determining agricultural supply. However, supply response models have either incorporated risk in an ad hoc manner or not at all. A rational expectations supply response model incorporating price risk is developed, an estimation procedure suggested, and an empirical example presented.
Optimal Use of Qualitative Models: An Application to Country Grain Elevator Bankruptcies
Authors: Kaylen Michael S. , Devino Gary T. , Procter Michael H.
Published: July 2016

Qualitative models can be used for decision making under uncertainty. This provides a useful framework for evaluating the models. If the costs for every action/state of nature combination are known, decisions made using a well-calibrated model would result in actual costs being close to expected costs. In addition, the actual cost can be compared to the cost of perfect foresight actions, giving a bound on the value of a better model. Application of these procedures is made using a logit model developed to predict Missouri country grain elevator bankruptcies.
Adoption of Double-Cropping Soybeans and Wheat
Authors: Shapiro B.I. , Brorsen B.Wade , Doster D. Howard
Published: July 2016

Double-cropping of soybeans and wheat is often promoted by extension personnel. This paper seeks to explain how the decision to adopt double-cropping is made, using a Tobit regression model. Tobit makes use of more of the information in the data set than do logit or probit and explains not only the decision to double-crop but also the rate of adoption. The paper considers factors such as profit and risk perceptions and risk which have not been included in the past models used to explain adoption of technology. The results show that risk perception is important. Contrary to the findings of some other adoption studies, this decision in not influenced by human capital factors. The farmers who double-crop are more highly leveraged and appear to do so both to achieve higher income and as part of a risk diversification strategy. This is consistent with the importance of the location factor, measured as the average number of growing degree days at the farm's location. Growing degree days is a proxy for the actual distribution of returns from double-cropping and is the main factor explaining this decision. Extensive adoption of double-cropping in cooler regions of the Midwest must await technological advances that can increase the profitability of double-cropping by reducing the growing season for wheat and/or beans.
Estimating the Benefits of Groundwater Contamination Control
Authors: Sun Henglun , Bergstrom John C. , Dorfman Jeffrey H.
Published: July 2016

In this paper, a conceptual model for estimating option price for groundwater quality protection is developed, and the effects of subjective demand and supply uncertainty and other variables on option price are examined. A contingent valuation study to measure option price for groundwater quality protection was conducted in southwestern Georgia. Valuation results suggest that the monetary benefits to citizens of protecting groundwater supplies from agricultural chemical contamination are quite large.
Implications of Raising the Nonfat Solids Standards for Beverage Milk
Authors: Salathe Larry , Price J. Michael
Published: July 2016

An econometric model of the dairy industry was used to estimate the effects on farmers, consumers, and taxpayers of nationwide adoption of the California nonfat solids standards for fluid milk. It was estimated that adoption of the California standards would raise farm-level milk prices by 1 to 5 percent in the short run and by 1 to 2 percent in the long run. The average retail price of fluid milk would rise by 9 to 13 cents per gallon. Dairy program costs fall under most scenarios, but could rise if surpluses fall to levels that would trigger increases in the support price.
Future Agricultural and Food Policy
Authors: Spitze Robert G. F.
Published: July 2016

The agricultural and food policy future now offers more than usual excitement—and also uncertainty. As the calendar turned, it ushered in a year of decision about the future of this nation's public policy concerning its agriculture production, farm family and rural community welfare, consumers' food supply, and agricultural trade. It also signaled the changing of the leading actors who will perform yet unwritten roles in a yet-to-be-titled drama of policy development. All of this will unfold both within an international and national environment of volatile economic forces. It offers all the challenge that a student of policy could expect.
The Role of Food in the International Affairs of the United States
Authors: Coffey Joseph D.
Published: July 2016

From the early 1600s, when tobacco exports literally saved the struggling Jamestown settlement, to the January 4, 1980, embargo of grain to the Soviet Union, food and agriculture have played varied roles in international affairs of the U.S., that is, in the political, military, economic, and cultural exchanges that affect the power of the U.S. relative to other sovereign nations. Food donations have been used as a humanitarian gesture to avert starvation. Food export embargoes have been used as weapons against foreign adversaries and domestic scarcities. Food pledges have been used to promote international food aid conventions. Food import quotas have been reallocated to reward friendly nations and penalize unfriendly ones. U.S. food shipments have been used to feed Allied soldiers and to barter for strategic materials. Food exports have been used to bolster the domestic economy and strengthen the dollar.
Protection of Agricultural Land: An Institutionalist Perspective
Authors: Hite J. C. , Dillman B. L.
Published: July 2016

For a long time, the consensus of old farmers sitting around crossroads stores has been that, sooner or later, America is going to run out of agricultural land because of all the houses, shopping centers, and highways that are spreading out onto the nation's cropland. And for years, such observations have been summarily dismissed as the ravings of ignorant men with too much time on their hands. Yet in the last half of the 1970s, a significant part of the educated elite in the United States began to suspect that those old farmers just might be correct. The farm press began to run articles concerning the loss of prime agricultural land to urban sprawl (Johnson); some of the more prestigious national journals appealing to educated laymen began to publish articles on the subject (Blundell); and even general circulation newspapers that seldom deign to print anything other than stories on political corruption or murder and mayhem devoted space to feature-length articles warning of the loss of cropland to non-agricultural uses (Burnside).
Spline Functions: An Alternative to Estimating Income-Expenditure Relationships for Beef
Authors: Huang Chung-Liang , Raunikar Robert
Published: July 2016

Income-expenditure relationships are important components in many economic models used to project food expenditure and to understand food-expenditure behavior. The empirical estimation of income-expenditure relations has concentrated on the effects of income in explaining the variations of the household food expenditure. However, the problem of structural or parametric homogeneity for Engel curves in the analysis of household food expenditure behavior has received less attention in the applied demand literature.
Conversion of Prime Agricultural Land to Nonagricultural Uses in One Area of the Sunbelt
Authors: Ramsey A. Frank , Corty Floyd L.
Published: July 2016

In general, people are aware of the rapid growth of urban areas, the spread of suburban developments, urban sprawl, strip developments, and extensive highway systems, but they are seldom aware of the extent to which prime agricultural land has been, and is being, diverted to these and other nonagricultural uses.
The Structural Stability of the Concentration-Performance Relationship in Food Manufacturing
Authors: Miller Stephen E.
Published: July 2016

The literature of industrial organization is replete with analyses of the relationship between seller concentration and market performance. Most researchers have hypothesized a continuous linear relationship between profitability and concentration and have estimated that relationship accordingly.
An Analysis of the Southeastern Feeder Pig Market
Authors: Reid Donald W. , Reed Michael R.
Published: July 2016

The production of feeder pigs as a cash commodity has been widespread in the southeastern U.S. during the past several years. One indication of the extent of marketing pigs at this intermediate stage is the fact that in 1979, 41 percent of the total Tennessee pig crop was sold through organized feeder pig sales (Rawls). This specialized production is continuing in many areas of the Southeast, although a trend has emerged that has more producers holding feeder pigs and feeding them to market weight.
Efficient Cash and Hedged Enterprise Combinations in Feeder Calf Backgrounding Operations
Authors: Bobst Barry W. , Grunewald Orlen C. , Davis J. T.
Published: July 2016

Backgrounding of feeder cattle is a growing specialty operation in the so-called “Fescue Belt” grasslands of the South (Bradford et al.). Backgrounding is largely a seasonal enterprise, consisting of the purchase of weaned calves that are placed on pasture and supplemental feed for several months and then resold for placement in feedlots. Since feeder calf and feeder cattle prices are among the most volatile of all classes of cattle, backgrounders face considerable price risk (Russell and Franzmann). In principle, hedging could shift this risk, but there has been a question whether hedging can be worthwhile, given the additional costs and financial obligations involved.
Relationship Between Farm Size and Technical Efficiency in West Tennessee Agriculture
Authors: Bagi Faqir Singh
Published: July 2016

There has been persistent interest in the issues relating to farm size and survival of family farms since the beginning of agricultural economics as a discipline. Since the early 1950s, the number of farms has been decreasing and the average farm size has been increasing.
Dynamic Factor Demands for Aggregate Southeastern United States Agriculture
Authors: Taylor Timothy G. , Monson Michael J.
Published: July 2016

A four equation input demand system for aggregate Southeastern United States agriculture consistent with dynamic optimizing behavior is specified and estimated. Labor and materials are considered as variable inputs while land and capital are treated as quasi-fixed inputs. It is found that the adjustment rates for capital and land differ considerably and are interdependent. Further, the data appear consistent with the existence of an aggregate production technology and the hypothesized optimizing behavior.
A Markov Chain Analysis of Structural Changes in the Texas High Plains Cotton Ginning Industry
Authors: Ethridge Don E. , Roy Sujit K. , Myers David W.
Published: July 2016

Markov chain analysis of changes in the number and size of cotton gin firms in West Texas was conducted assuming stationary and non-stationary transition probabilities. Projections of industry structure were made to 1999 with stationary probability assumptions and six sets of assumed conditions for labor and energy costs and technological change in the non-stationary transition model. Results indicate a continued decline in number of firms, but labor, energy, and technology conditions alter the configuration of the structural changes.
Estimating Implicit Marginal Prices of Quality Characteristics of Tomatoes
Authors: Jordan Jeffery L. , Shewfelt R. L. , Prussia S. E. , Hurst W. C.
Published: July 2016

A hedonic price function is developed for estimating the implicit prices for selected quality characteristics of fresh tomatoes at three points in the marketing season. The estimation of this function, proposed as a method of evaluating changes in the post-harvest system, is accomplished using a flexible functional form. Those quality characteristics that most affect the price of tomatoes can help determine the economic feasibility of alternative handling techniques or new technologies.
An Evaluation of the Rice Outlook and Situation Price Forecasts
Authors: Elam Emmett W. , Holder Shelby H.
Published: July 2016

The Rice Outlook and Situation (RO&S) forecasts were compared to the forecasts of a univariate Box-Jenkins (BJ) model. On balance, the RO&S forecasts had lower mean square forecast errors and lower mean absolute forecast errors than the BJ model forecasts. The differences in the squared and absolute forecast errors were not significant, however. Based on the concept of conditional efficiency as set forth by Granger and Newbold, it was found that the BJ forecasts did not add any information that might improve forecast accuracy beyond what was already incorporated in the RO&S forecasts.
Wheat Acreage Response: Investigation a Regional Econometric Investigation
Authors: Bailey Kenneth W. , Womack Abner W.
Published: July 2016

An econometric model of planted wheat acreage was estimated for five distinct production regions in the United States. This structural investigation represents an update of previous published work with specific attention given to policy program variables, weather, production cost, risk, market price influences, and program participation. Estimated results indicated regional divergence in responsiveness to government program variables. The most significant divergence occurred in the Cornbelt and Southeast—soft red winter wheat areas. Results indicate that management of the wheat program from the USDA level will contain countervailing production incentives unless these regional characteristics are taken into consideration in policy directives.
Egg Prices Revisited
Authors: Schrader Lee F. , Bessler David A. , Preston Warren
Published: July 2016

Recent egg price quotes are evaluated in a vector autoregression. The results indicate that empirical relationships observed over the period 1975-1976 differ from those observed over the period 1979-1982.
Agriculture as the Problem: New Agendas and New Opportunities
Authors: Batie Sandra S.
Published: July 2016

Agriculture was once seen as the solution to many of the nation's problems. A strong agricultural sector translated into a strong America. Kohl et al. have presented four reasons for the past public commitment to agriculture. First, the agricultural sector has had considerable political power; second, there has been a widely held perception that farmers were economically disadvantaged relative to the rest of society; third, for many decades the growth of rural economies has been dependent on healthy agricultural sectors; and, finally, information produced by colleges of agriculture has been seen as a public good worthy of support by general tax revenues.
The Pricing Efficiency of Agricultural Futures Markets: An Analysis of Previous Research Results
Authors: Garcia Philip , Hudson Michael A. , Waller Mark L.
Published: July 2016

The analysis examines quantitatively the findings of previous studies of the pricing efficiency of various agricultural markets using a logit framework. The findings provide insight into the importance of commodity characteristics, uncertainty, and testing procedures used on the results of past research of pricing efficiency. The study also identifies several areas for further research.
Patenting Life Forms: Issues Surrounding the Plant Variety Protection Act
Authors: Claffey Barbara A.
Published: July 2016

This paper examines the issues surrounding the patenting of life forms, specifically the social and private costs and benefits of the Plant Variety Protection Act (PVPA) (Plant Variety Protection Act, 1970). The PVPA is a current issue, encompassing all the elements of the economic, social, and moral controversy aroused by the broader issue of patenting life forms generally.

The subsequent sections of the paper outline the specific issues surrounding the PVPA, discuss the issue of plant patenting, present the arguments favoring and opposing plant patenting, and, finally, present an analysis of the major issues of the PVPA.
Linkages Between Crop Insurance and Pre-Harvest Hedging
Authors: Dhuyvetter Kevin C. , Kastens Terry L.
Published: July 2016

The impact pre-harvest hedging and crop insurance strategies have on expected revenue and associated risk as well as how producers' risk attitudes affect optimal strategies was analyzed for Kansas wheat farms. No insurance, Catastrophic (CAT), Actual Production History (APH), and Crop Revenue Coverage (CRC) were considered. Average revenue was similar across alternatives, but APH and CRC resulted in the least income variability. Risk reduction effects of hedging were small and the advantage of CRC over APH decreases as hedging increases. This historical study provides useful information; however, if future market conditions differ significantly from the past, optimal strategies may change.
Impacts of Within-Farm Soil Variability on Nitrogen Pollution Control Costs
Authors: VanDyke Laura S. , Bosch Darrell J. , Pease James W.
Published: July 2016

The effects of considering variable within-farm soil runoff and leaching potential on costs of reducing nitrogen losses are analyzed for a Virginia dairy. Manure applications may cause nitrogen losses through runoff and leaching because of factors such as uncertain nitrogen mineralization. Farmers can reduce nitrogen control costs by applying manure on soils with less nitrogen loss potential. Ignoring within-farm soil variability may result in overstating the farm's costs of reducing nitrogen losses.
Accounting for Spatial Characteristics of Watersheds in Evaluating Water Pollution Abatement Policies
Authors: Qiu Zeyuan , Prato Tony
Published: July 2016

This study evaluates three agricultural nonpoint pollution abatement policies: regulating the spatial pattern of agricultural activities, ambient tax, and abatement tax/subsidy. All three policies incorporate spatial characteristics of agricultural emission loading and movement for an agricultural watershed in the Midwest. The effects of spatial variation in natural conditions and landscape features on agricultural emissions and crop yield are evaluated using a newly developed biophysical simulation model and experimental data. While the policies are equally cost effective in reducing agricultural nonpoint source pollution, their implementation feasibility is quite different.
Sources of variation in extinction rates, turnover, and diversity of marine invertebrate families during the Paleozoic
Authors: Nichols James D. , Morris Richard W. , Brownie Cavell , Pollock Kenneth H.
Published: July 2016

We have recently shown how capture-recapture models can be used in conjunction with stratigraphic range data to estimate taxonomic extinction rates and taxonomic diversity. Here we present a new method that can be used to estimate taxonomic turnover (defined here as the proportion of taxa extant at timei, that originated in the intervali– 1 toi). We used these methods in conjunction with stratigraphic range data for families in five phyla of Paleozoic marine invertebrates. We estimated fossil encounter probabilities, extinction rates, diversity, and turnover and used these estimates to test hypotheses about variation among phyla and geologic series. Encounter probabilities varied among taxa and showed evidence of a decrease over time for the geologic series examined. The number of families varied substantially among the five phyla and showed some evidence of an increase over the series examined. There was no evidence of variation in extinction probabilities among the phyla. Although there was evidence of temporal variation in extinction probabilities within phyla, there was no evidence of a linear decrease in extinction probabilities over time, as has been reported by others. We did find evidence of high extinction probabilities for the two intervals that had been identified by others as periods of mass extinction. We found no evidence of variation in turnover among the five phyla. There was evidence of temporal variation in turnover, with greater turnover occurring in the older series.
Effects of differential preservation on the measurement of taxonomic diversity
Authors: Lasker Howard
Published: July 2016

A computer simulation was developed which estimates the effects of differential preservation on the value of taxonomic diversity in fossil assemblages. Taxonomic diversity was measured with the Shannon-Weaver index, H′ and with evenness, J. Preservation markedly alters quantitative measurements of taxonomic diversity. The degree of alteration can, however, be predicted on the basis of the species-abundance distribution and on the distributions of species of varying preservability. The indices of diversity H′ and J measure different aspects of diversity, but respond to differential preservation in a similar manner. Evenness, J, is recommended for paleoecologic use. The computer model can be used to revise fossil diversity data. A simple form of such a model has been used, and suggests that some previous interpretations of paleoecologic diversity may be in error.
Trophic model for the adaptive radiations and extinctions of pelagic marine mammals
Authors: Lipps Jere H. , Mitchell Edward
Published: July 2016

Pelagic marine mammals (cetaceans and pinnipeds) generally invaded the seas rapidly in response to new ecologic opportunities. After cetaceans initially appeared and radiated in the Eocene, they declined in the Oligocene, but radiated into many new adaptive types in the Miocene. Pinnipeds apparently evolved in the earliest Miocene, rapidly radiating into many adaptive types. We propose that the radiations, and declines, of species were responses to the availability of trophic resources in oceanic environments. These trophic resources are closely related to upwelling processes in the oceans. We suggest that increased upwelling intensity, due to climatic or tectonic events, permitted the initial invasions and radiations and that decreased intensity caused cetacean extinctions in the Oligocene.
Environmental versus genetic causes of morphologic variability in bryozoan colonies from the deep sea
Authors: Schopf Thomas J. M.
Published: July 2016

Bryozoans are colonial animals and this permits the partitioning of their morphologic variability into components of within colony (i.e. within a single genotype) and between colony (i.e. between genotype) variance. These data have been obtained for four species of the endemic deep-sea genus Euginoma for a series of characters. In 8 comparisons, one component of the total variance dominated at the 5% level. Population (between colony) variance contributed significantly to the total variance in 63% of the comparisons (5 of 8); individual (within colony) variance contributed significantly to the total variance in 37% of the comparisons (3 of 8).

Compared to shallow water species, the surprising feature of the deep-sea data is that the between colony component of variance is as high as it is. Possibly in the more stable, deep-sea environment, the genotypic contribution to the variance of each individual colony is expressed to a greater degree than in the more variable, shallow water regime. If so, then analyses of variability in colonial animals may be an independent means of ascertaining stability gradients in the fossil record.
Covariation patterns in the postcranial skeleton of moas (Aves, Dinornithidae): A factor analytic study
Authors: Cracraft Joel
Published: July 2016

The covariation patterns of the postcranial skeleton in eight species of moas (Aves, Dinornithidae) from the Pleistocene of New Zealand are described using multiple factor analysis. Rotation schemes include an orthogonal Varimax and oblique (direct quartimin) simple structure solutions.

Four major patterns of covariation are resolved: a length factor, primarily that of leg length; a width factor, including pelvis width and long bone widths; a sternal breadth factor; and a sternal length-posterior pelvis length factor. The first two patterns represent a functional separation between body size and those aspects of the skeleton, scaling allometrically, adapted to support body weight. The sternal breadth factor may indicate that features contributing to trunk support are independent from those width measurements of the pelvis and hindlimb bones. The sternal length-posterior pelvis length factor reveals a pattern of covariation that is somewhat independent of other patterns (long bone lengths) determining variability in body size.
Microstratigraphic sampling and the limits of paleontologic resolution
Authors: Schindelz David E.
Published: July 2016

Rates of modern sedimentation in various depositional settings have been compiled and adjusted for compaction for the purpose of estimating the spans of time represented in thin stratigraphic samples. Owing to discontinuous or low rates of sedimentation, it is either impossible or impractical to recover a continuous series of discrete life assemblages of fossil populations by collecting microstratigraphic samples from continuously fossiliferous intervals. Assemblages that are less time-averaged may be recovered from discontinuous records formed in depositional environments with higher rates of intermittent sedimentation, but these are isolated in time and cannot be used to observe the dynamics of local faunal history. Patterns of fossil distribution may appear similar to patterns of living populations explained by neontologic processes, but the longer time scale of even the best fossil sequences suggests the action of uniquely paleontologic processes that may be driven by environmental changes.
Bone-collecting by harvesting ants
Authors: Shipman Pat , Walker Alan
Published: July 2016

Bone-collecting behavior in the harvester ant,Messor barbarus, has been observed for the first time. Excavation to the depth of the packed substrate of a single ant hill yielded 1167 modern bones derived from nine or more species of small vertebrates. Since harvester ants of various species are well-known from the Americas, Africa, and Eurasia, ants may have served as important agents of concentration for micromammal assemblages in the fossil record. Analysis of the faunal and skeletal representation of the ant hill assemblages reveals characteristic patterns that might be used to distinguish such assemblages from those collected by avian or mammalian predators.
Growth models in fossil arborescent cheilostome bryozoans
Authors: Cheetham Alan H. , Hayek Lee-Ann C. , Thomsen Erik
Published: July 2016

Cheilostome bryozoans that grew as rigidly erect arborescent colonies dominate many bryozoan-rich assemblages of Tertiary age, in which they are found most commonly as small dissociated fragments. The regularity with which branching and branch thickening occur in intact colonies of living species provides a basis for quantitative reconstruction of these growth processes in fossils. We propose models to describe branch thickening, develop methods to extend both thickening and branching models to fossils, investigate the thickening and branching properties of four Paleocene and five Oligocene species and compare the properties of these fossils to those of nine living species.

The properties investigated are largely mutually independent and species specific irrespective of geologic age and have similar numerical ranges among different assemblages of coeval species. Species are evenly distributed across the range of possible morphologies between observed extremes, without obvious gaps. Statistically significant trends through time are identified in gradients of branch thickening, which have implications for the resistance of colonies to mechanical stress, and in angles of bifurcation, that are important in the way growing colonies occupy space.
Patterns in the evolution ofHomo erectus
Authors: Rightmire G. Philip
Published: July 2016

Skull and tooth dimensions ofHomo erectusfossils from Africa, Europe and Asia appear to fluctuate rather than to change progressively during an interval of 1.3 Myr prior to the start of the Upper Pleistocene. No significant trends can be observed. This suggests a period of stasis in human evolution, after whichHomo sapiensmay have evolved rapidly from archaic mid-Pleistocene ancestors.
Intercolony fusion suggests polyembryony in Paleozoic fenestrate bryozoans
Authors: McKinney Frank K.
Published: July 2016

Fusion occurred between pairs of conspecific colonies of Permian fenestrate bryozoans that were of approximately equal radius at time of contact. In contrast, no fusion occurred in pairs of conspecific colonies that were of unequal radius at time of contact. It is suggested that histologically compatible colonies developed from larvae that settled essentially simultaneously and that the larvae were siblings, lecithotrophic with low mobility, and of the same genotype (i.e., polyembryonic). Thus polyembryony appears to have existed as a reproductive “strategy” for at least 275 Myr, and its scarcity in modern taxa cannot be due to recentness of evolution.
Acoustic analyses of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia)
Authors: Weishampel David B.
Published: July 2016

Lambeosaurine dinosaur crests are judged to have been conducive to resonation on the basis of an acoustic analysis of the structure of the nasal cavity. Size and shape of the nasal cavity suggest low vocal frequencies in adults, as does information on potential auditory acuity in these animals. Lateral diverticula (present in all but juvenile specimens) acted to suppress portions of the vocal spectrum. Juveniles vocalized at higher frequencies than adults and potential auditory sensitivity at high frequencies in adults suggests a high degree of parent-offspring vocal communication. Sexual variation and causes of selection for low frequency vocalization are also examined.
Development of cell arrangement in ostracod carapaces
Authors: Okada Yutaka
Published: July 2016

The correlation between epidermal cells and cuticular reticulation was clearly shown by transmission and scanning electron microscopes with larval ostracods just before ecdysis. Comparison of the reticulation patterns of Recent and Pleistocene specimens revealed that the epidermal cell arrangement of the adult ostracods is both consistent in the Recent population and conservative in phylogeny. Ontogenetic changes of the reticulation pattern were studied with specimens cultivated separately. Some gene control over the mitosis of epidermal cells was assumed, based on the ontogenetic development of the reticulation pattern. The pattern of fossil specimens suggests that the control has been well maintained in ostracod phylogeny.
Predation and Parallel Evolution: Recurrent Parietal Plate Reduction in Balanomorph Barnacles
Authors: Palmer A. Richard
Published: July 2016

Field and laboratory data indicate that all four species of Thais (Gastropoda, Muricacea) from rocky shores of the northeastern Pacific selectively attack barnacles at the margins of parietal (lateral) and opercular plates. Attacks are also more likely to be successful at plate margins. Such preferential attack and differential attack success may account for the evolutionary reduction in the number of parietal plates exhibited within seven of the eight families of balanomorph barnacles. Additional evidence suggests that predation by drilling gastropods may have also favored the evolution of strong external ribbing on these plates within some balanomorph lineages.

Radiation and plate reduction in the Balanomorpha occurred in concert with extensive radiation in muricacean gastropods, starting in the Late Cretaceous. Of the three skeletal conformations exhibited by open-surface dwelling barnacles (8, 6 and 4 parietal plates), only genera of the four-plated form have become proportionally more common in the Recent. Further, in a rather striking evolutionary experiment, a lineage of barnacles evolving free from gastropod predation retained primitive skeletal features. This supports the interpretation that predation by drilling gastropods has been an important selective force behind the widespread, parallel evolutionary tendency towards plate reduction in the Balanomorpha; a trend recognized by Darwin (1854), but for which he offered no explanation.
Age (Mortality) Profiles as a Means of Distinguishing Hunted Species from Scavenged Ones in Stone Age Archeological Sites
Authors: Klein Richard G.
Published: July 2016

Some ungulate species at Upper Pleistocene and Holocene archeological sites in South Africa exhibit catastrophic mortality profiles, while others exhibit attritional ones. The awareness by Stone Age people that some species are especially amenable to driving or snaring probably accounts for the catastrophic profiles. Natural catastrophic death immediately followed by human scavenging is a much less likely explanation because the species samples comprise material lumped from deposits that accumulated more or less continuously over hundreds or even thousands of years during which period there is no reason to suppose the repeated occurrence of natural catastrophes nearby.

The inability of Stone Age people to obtain prime-age adults in species that are not particularly amenable to driving or snaring presumably accounts for the attritional mortality profiles. Although the species that display attritional profiles conceivably were scavenged, the high proportion of very young individuals in the profiles suggests active hunting. Very young individuals are much less abundant in attritional profiles from local non-archeological sites, probably because their carcasses were removed from the record before burial, primarily by carnivore or scavenger feeding. Scavenging would account for the abundance of very young individuals in the archeological sites only in the unlikely event that people could regularly locate carcasses before other predators did.

In general, geomorphic/sedimentologic context is probably the best criterion for determining whether a species characterized by a catastrophic profile in an archeological site was hunted or scavenged. At the majority of known sites, active hunting is suggested. In the case of a species characterized by an attritional profile in an archeological site, the proportion of very young individuals in the sample probably provides the best criterion for distinguishing hunting from scavenging. A relatively high proportion of very young individuals suggests active hunting.
Out with a whimper not a bang
Authors: Clemens W. A. , Archibald J. David , Hickey Leo J.
Published: July 2016

The recurring debate over the causes of the massive extinctions of such groups as the dinosaurs, ammonites, and calcareous nannoplankton, and the crash of the distinctive Aquilapollenites pollen province, used by biostratigraphers to mark the close of the Cretaceous, has been considerably enlivened with the resurgence of hypotheses suggesting catastrophic events. The impact of an asteroid, explosion of a supernova, sudden changes in oceanic circulation and composition, or atmospheric perturbations, to mention a few, have been put forward as malefactors. But, just how sound is the evidence of a biotic catastrophe?
Cambridge Genome Meeting, June 22–24, 1981
Authors: Schopf Thomas J. M.
Published: July 2016

Almost at the end of his chapter on Mutation, G. G. Simpson in 1953 in The Major Features of Evolution noted that “There is also increasing evidence that mutation rate is itself, to some degree, a genetically controlled character.” If for mutation one uses the broad definition of the origin of new hereditary types, then the glimmerings to which Simpson referred now have become a documented fact at the molecular level.
Stabilizing species selection in the Archaeogastropoda
Authors: Gilinsky Norman L.
Published: July 2016

Factor analysis of morphometric data from fossil and recent Archaeogastropoda reveals that there has been a progressive reduction in the variety of archaeogastropod shell shapes through time. High and low spired genera have slowly disappeared while equidimensional forms, which have always been the most common, have become even more abundant. The taxonomic manifestation of this trend has long been appreciated and involves: 1) the extinction of most of the Pleurotomariacea, the Euomphalacea, Trochonematacea, and several other superfamilies, which collectively comprise most of the variation in shape among early archaeogastropods, and 2) the proliferation of the primarily equidimensional Trochacea and Neritacea. I suggest that this macroevolutionary trend may be explained by the general process I refer to as “stabilizing species selection.” More specifically, I suggest that the mechanism of stabilizing species selection in the case presented here may have been differential rates of origination.

I believe that the innovative concept of species selection has been burdened by the adherence of its advocates to the idea that differential extinction is its primary mechanism. This preference for differential extinction is rooted in our emphasis upon differential mortality in microevolution and is not based upon data of macroevolutionary change. I argue that differential origination may be as important as differential extinction in directing macroevolutionary change and that demographical and autecological properties of species may be its agents. Recognition of the importance of differential origination will have an important impact upon our concept of the relationship between adaptation and the evolutionary process.
Was marine faunal diversity in the Pleistocene affected by changes in sea level?
Authors: Wise Kurt P. , Schopf Thomas J. M.
Published: July 2016

We have investigated whether changes in marine faunal diversity during the Pleistocene would have been affected by changes in sea level. Our estimate of changes in area of shallow marine seas between low stand and high stand of sea level (approximately 200 m) leads to a prediction of approximately a 25% change in species diversity, 10% change in generic diversity and less than a 5% change in familial diversity. This agrees with the observation that large scale generic or familial changes have not been widely noted for the Pleistocene. As in other intervals of geologic time, changes in the sizes of faunal provinces owing to changes in sea level are less likely to be the significant factor in changing marine diversity than are changes in the number of faunal provinces.
Ideas on the timing of metazoan diversification
Authors: Stanley Steven M.
Published: July 2016

Fossil data suggest that the great majority of metazoan classes that existed in the Early Cambrian arose after about 700 my ago. The rectangular model of evolution, which views most evolutionary change as being concentrated in speciation events, can easily accommodate the implied rate of divergence.

If, as some authors believe, the eukaryotic cell arose long before the start of the Cambrian, an explanation is required for the delay of large-scale metazoan divergence. The advent of sexuality may have triggered diversification, not by accelerating phyletic evolution, as traditionally believed, but by making possible speciation and, hence, adaptive radiation. Another important delaying factor may have been the near-saturation of Precambrian algal systems in the absence of cropping by herbivores. Uncropped Precambrian systems should have been self-limiting in terms of diversification. When advanced heterotrophy finally arose, self-propagating feedback systems of diversification should have been set in motion. Even if the eukaryotic cell arose later than commonly envisioned and triggered the radiation of the Metazoa about 700 my ago, the earlier absence of sexuality and cropping may have delayed the transition from the prokaryotic condition to the eukaryotic condition.
Parallel clines in morphologic and genetic differentiation in a coastal zone marine invertebrate: the bryozoanSchizoporella errata
Authors: Schopf Thomas J. M. , Dutton Alan R.
Published: July 2016

Genetic and morphologic differentiation in the bryozoanSchizoporella errataparallel each other over a distance of 102 km along the southern shore of Cape Cod. This is seen in the allele frequencies of two marker genes and in the length of the avicularium (a type of defensive polymorph of the bryozoan colony). These changes appear to be part of the continuing evolutionary adaptation to local environmental conditions, perhaps characteristic of marine species whose dispersal ability is very limited. The length scale of significant changes in allele frequencies at the two loci is as low as 10–11 km, and for avicularium length is 13 km.
Species diversity in the Phanerozoic: an interpretation
Authors: Raup David M.
Published: July 2016

Species diversity among fossil invertebrates of the Phanerozoic is highly correlated with volume and area of sedimentary rocks. The correlations are statistically significant at the 1% level. The relationship holds even in regions (such as Canada) where the area and volume of rock do not increase through time. These results are interpreted as indicating that the apparent number of species is strongly dependent on sampling and that many of the changes in diversity seen in the Phanerozoic are artifactual. Consequently, there is no compelling evidence for a general increase in the number of invertebrate species from Paleozoic to Recent. This conclusion applies primarily to marine organisms. Diversity may have been in dynamic equilibrium throughout much of this time.

A few intervals of the Phanerozoic have consistently fewer invertebrate species than would be predicted from the amount of sedimentary rock available for study. The Silurian, Permian, and Cretaceous stand out in this regard. This may result either from lower than normal diversity during these periods or from an unusual abundance of unfossiliferous rocks (evaporites, red beds, etc.).
Species diversity in the Phanerozoic: species-area effects
Authors: Sepkoski J. John
Published: July 2016

Raup's (1976a) data on Phanerozoic species numbers are examined for species-area relationships, using published estimates of areas of continental seas. By means of multiple regression, species numbers are regressed on both estimated areas of seas and amounts of available rock for sampling, as measured by outcrop area and rock volume. Although the sampling effects apparently have the strongest influence on fossil species diversity, areas of seas substantially increase the total correlation, suggesting that Phanerozoic species numbers were in equilibrium with habitat area. This is further supported by the fact that estimated parameters in the regressions are fairly consistent with established island biogeographic theory. Much of the remaining residual variation can be explained by periods of disequilibrium.