bluuebunny/crossref_metadata_2025 huggingface dataset:
Financial Control and Variable Amortization Under Uncertainty: An Application To Texas Rice Farms
Authors: Rahman Md. Lutfor , Barry Peter J.
Published: July 2016

Variability in commodity prices and yields, together with greater financial obligations for highly leveraged farms, have added much uncertainty about farmers' debt servicing capacity (Barry and Fraser; Hanson and Thompson). As a result, financial responses must come more to the forefront in farmers' risk management, through emphasis on fuller development and application of the financial control process; and development of specific financial programs and instruments for dealing with random variations in debt servicing capacity (Baker; Lee). An example of the second response is the variable amortization payment plan VAPP suggested by Baker and tested empirically by Stone for use in farm mortgage lending.
Regional and Functional Disaggregation of the Cotton Industry in a National Input-Output Model
Authors: Collins Keith J. , Glade Edward H.
Published: July 2016

Various classes of models possess characteristics essential for commodity analysis. One class, input-output (I-O) models, can complement more widely used ommodity models, such as econometric and mathematical programming, which are often directed at a few specific production and use markets for the commodity under analysis. I-O models either formally linked with, or used independently of, these other models provide an analytical framework for examining macroeconomic adjustments to commodity market shocks. Further, I-O allows the tracing of resource flows to and from the commodity market and among all secondary markets. These characteristics suggest that a commodity-oriented I-O model ought to be a component of a package of models designed to provide complete coverage of a commodity for economic analysis.
Agricultural Economics Students at Southern Land Grant Universities
Authors: Adrian John L. , Dunkelberger John E. , Molnar Joseph J.
Published: July 2016

Agricultural economics occupies an unique position in most agriculture programs because it and rural sociology are the only social sciences among a broad array of plant, animal, and technical disciplines. As economic and technological changes have added to the complexity, of U.S. agriculture, the relative importance of agricultural economics has increased. The demand for individuals possessing knowledge of the technical aspects of agriculture and the ability to evaluate the social and economic ramifications of alternatives is increasing.
Reply: Energy Accounting: The Case of Farm Machinery in Maryland
Authors: Foster Phillips , Wichelns Dennis
Published: July 2016

The most important issue raised in the comment by Bradford involves the problem of how to handle the fact that, although the logical period for accounting for energy use on the farm is one year, farm machinery is typically used over a period of several years. No solution to this problem will be entirely satisfactory, and the alternative offered by Bradford has its own difficulties. Nevertheless, the Bradford alternative is worth trying, and this response to the comment will consider briefly his proposal.
Productivity in U.S. Food and Agriculture: Implications for Research and Education
Authors: Eddleman B. R. , Teigen Lloyd D. , Purcell Joseph C.
Published: July 2016

Increased demand for U.S. farm exports—primarily food grains, feed grains, and oil crops—emerged as an important factor influencing food and agricultural research and education in the 1970s. Maintaining producers' revenue remained as a motivating force in agricultural research.
Profitability and Risks in Dairy Feeding Programs: A Multiperiod Optimization
Authors: Shumway C. Richard , Reyes Alberto A. , Blake Robert W.
Published: July 2016

Considerable research has been conducted over the years to determine optimal rations for dairy cattle. Dean et al. extended earlier work through a comprehensive examination of milk production functions, isoquant shapes, and feed systems to maximize income over feed cost (IOFC) for a given point in time.
Importance, Causes, and Management Responses to Farm Risks: Evidence From Florida and Alabama
Authors: Boggess William G. , Anaman Kwabena A. , Hanson Gregory D.
Published: July 2016

Despite the contention that risk and uncertainty play an important role in agriculture in North Florida and South Alabama, very little is known about producers' perceptions of risk. This paper describes the procedures used and the results obtained from a statistically random survey of farmers' perceptions of the importance of various sources of risk and alternative risk management practices. Initially, farmers were asked to define risk and then to rank various sources of risk and management responses to risk based on the relative importance of each to their operation. Summary statistics, Chi-square analyses, and logistic regression techniques were used to analyze the data.
Optimal Management Strategies for Alfalfa Production Within a Total Farm Plan
Authors: Debertin David L. , Pagoulatos Angelos
Published: July 2016

This paper examines the impacts of alternative management strategies for the production of alfalfa within the context of a total farm plan. A linear programming model is used to represent a 600-acre farm which can grow either grain crops or alfalfa. Alfalfa production competes with the grain crops for available land, labor, machinery, and field time over a calendar of tillage, planting, cutting, spraying, and harvesting activities. The profitability of an acre of alfalfa and the contribution of alfalfa to net returns for the farm varies quite widely depending on the particular alfalfa management strategy selected.
Optimal Irrigation Pivot Location on Irregularly Shaped Fields
Authors: Hatch L. Upton , Hardy William E. , Rochester Eugene W. , Johnson Gregory C.
Published: July 2016

Although annual rainfall in the Southeast is adequate, its distribution is a potential constraint to agricultural production. Farmers require production information concerning efficient use of irrigation technology adapted to regional growing conditions. Selection of optimal position, size, and number of pivots in center pivot irrigation systems poses special problems on small, irregularly shaped fields. In the southeastern United States, field size and shape are often varied and irregular. A mixed integer programming model was constructed to assist in irrigation investment decisions. The model is illustrated using irrigated peanut production in southeast Alabama. Results indicate the importance of economic engineering considerations.
Developing Country Perspective: Southern Agriculture and the World Economy: The Multilateral Trade Negotiations
Authors: Knudsen Odin
Published: July 2016

The Uruguay Round marks the eighth time since the end of World War II that the member countries of General Agreement on Tariffs and Trade (GATT) have attempted to negotiate a reduction in trade restrictions and protection. Previous rounds of negotiation have had remarkable success in reducing trade protection.
European Community Perspective: Southern Agriculture and the World Economy: The Multilateral Trade Negotiations
Authors: Vonthron Jacques
Published: July 2016

Let me start out by thanking you for giving me this opportunity to share a few thoughts with you on the European Community's (EC) agricultural policy—and on some recent important developments affecting farm trade. I am especially grateful to you because the opportunity comes at a time when consideration of farm policy and farm trade is more than ever on people's minds.
Australian/Cairns Group Perspective: Southern Agriculture and the World Economy: The Multilateral Trade Negotiations
Authors: Shires David
Published: July 2016

Last week was Australia's 200th birthday. When the rebels in America won what they called their war of independence, Britain lost her penal colonies in the Carolinas and looked around for replacements. The first colonial fleet arrived in Australia on January 26,1788, and included, along with 700 convicts, 44 sheep and 6 cattle. If Britain had defeated her American colonists, then the history of both Australia and Louisiana would likely have been very different. The French flag might be flying today over both Sydney and New Orleans.
United States Perspective: Southern Agriculture and the World Economy: The Multilateral Trade Negotiations
Authors: Clayton Kenneth C.
Published: July 2016

The current “Uruguay Round” of trade negotiations under the General Agreement on Tariffs and Trade (GATT) began with the Declaration by trade ministers at Punta del Este, Uruguay, in September 1986. To conduct the negotiations, an agricultural negotiating group, along with fourteen other such groups, has been established. Negotiating proposals on agriculture have been offered by the Nordic Countries, the European Community (EC), Canada, the Cairns group, Japan, and the United States.
Profit-Maximizing Dairy Sire Selection Package
Authors: Blake Robert W. , Shumway C. Richard , Tomaszewski Michael A. , Rickard Greg P. , LaBore John M.
Published: July 2016

The Net Present Value Sire Summary Professional Package (NPVSS) is a microcomputer program designed for technical personnel to help dairy producers better manage investments in genetic improvement. NPVSS is written in C language, utilizes the MS-DOS operating system, and requires 256K of RAM. It is menu driven and includes parameter screens to define herd management characteristics of individual producers. Profit rankings of bulls can be generated to evaluate alternative: a) objective functions (selection policies for genetic merit in milk income and type scores), b) herd management performance factors (conception rate, calving interval, age at first calving), and c) economic factors (milk price, semen price, discount rate, planning horizon).
Efficiency Criteria and Risk Aversion: An Empirical Evaluation
Authors: Wetzstein Michael E. , Szmedra Philip I. , McClendon Ronald W. , Edwards David M.
Published: July 2016

A conceptual link among mean-variance (EV), stochastic dominance (SD), mean-risk (ET), and Gini mean difference (EG) is established for determining risk efficient decision sets. The theoretical relations among the various efficiency criteria are then empirically demonstrated with a soybean and wheat double-crop simulation model. Empirical results associated with extended Gini mean difference (EEG) and extended mean-absolute Gini (EEΓ) for risk analysis are encouraging.
Modeling the Effects of the Food Stamp Program on Participating Households' Purchases: An Empirical Application
Authors: Huang Chung L. , Fletcher Stanley M. , Raunikar Robert
Published: July 2016

The present legal authority for the Food Stamp Program (FSP) is the Food and Agriculture Act of 1977. As adopted, the legislation includes a thorough overhaul of the FSP enacted into law in 1964. The FSP provides direct subsidies in the form of additional food dollars to low-income households to enhance the purchasing of nutritionally adequate diets. The most significant effect both on participating households and the food industry is the elimination of the purchase requirement whereby participants pay for food stamps. Under the new legislation, participants receive food stamps free of charge. The benefits received are roughly equivalent to the value of bonus stamps under the old program (Stucker and Boehm).
Energy Efficiency in Food Processing in the Southern Region
Authors: Broder Josef M. , Booth John T.
Published: July 2016

Food processing accounts for a large part of the total energy consumed in the food and fiber system, second only to household preparation. Havlicek and Capps emphasized that processing and distribution of food and fiber require 12 to 17 percent of the total U.S. energy budget. Thus far, research on energy use by agriculture in the southern region has concentrated on production of raw products at the farm level (Debertin and Pagoulatos) and consumption of food in the home (Lovingood and Goss; Rhee and Drew). The large processing and distribution network has been generally excluded from analysis because of a lack of information on energy used in these industries. Comprehensive data bases on energy use in food processing have been relatively limited because of the imperfectly competitive nature of food processing industries and because of unfavorable costs and benefits of compiling such information. Because of a lack of accurate and reliable data, little is known about the behavioral relationship of energy use in food processing and distribution.
Part-Time Farming: Productivity and Some Implications of Off-Farm Work by Farmers
Authors: Singh Surendra P. , Williamson Handy
Published: July 2016

The technological revolution in agriculture has produced a structural transformation in fanning that has changed the face of rural America. With improved technology and long-term U.S. economic growth, one major adjustment has been a reallocation of labor between farm and non-farm labor markets. After 1948, long-term economic forces created prospects of higher incomes in the non-farm sector. As a result, a large proportion of both white and black families ceased farming and took non-farm jobs. However, a number of other farm families have continued to work their farms, but have also taken off-farm jobs to supplement their income. Krasovec describes part-time farming as a regular two-fold occupation of the head of the family. That person may, on the one hand, be working permanently in non-agricultural industries either as an employee or as an independent craftsman, merchant or member of a profession, and on the other, in agriculture on a holding not large enough to justify a full-time occupation.
Economic Evaluation of an Alternative Marketing System For Feeder Cattle in Alabama
Authors: Sullivan Gregory M. , Linton Daniel A.
Published: July 2016

The marketing system for cattle in the United States has evolved with shifts from delivery to large terminal centers, to more decentralized markets. Because of innovations in transportation and processing technology, these structural changes have created a need for greater vertical coordination between different stages in the cattle marketing channels (Rhodes, p. 174; Sporleder, p. 101). Improved coordination requires appropriate market information about product supplies and the form of cattle preferred by buyers (Purcell, 1973, 1980).
Wood Fuel: An Alternative Energy Source for Agribusiness and Industry
Authors: Ames Glenn C. W. , Baxter Harold O.
Published: July 2016

Wood fuel is becoming increasingly more important as an alternate energy source because of price and shortages of fossil fuels. Furthermore, energy prices are expected to continue to rise in future years (U.S. Dept. of Energy, pp. 56–72). As a result, agribusiness firms in the Southeast are investigating the feasibility, of utilizing wood residues or whole tree green chips for their fuel supply. Some industries may continue to rely partially on their present gas- or oil-fired systems and add a wood-fired boiler as a backup system. The availability of wood as an industrial fuel at a competitive price is one of the major concerns of these firms.
The Effect of Increasing Transportation Costs on Florida's Cattle Feeding Industry: An Extension Application
Authors: Simpson James R. , Stegelin Forrest E.
Published: July 2016

Rapid fuel price increases in 1979 and early 1980, along with concern about further rises, have led to speculation that Florida, a net calf exporter but net importer of finished cattle and beef, will be increasingly competitive in finishing cattle to slaughter weight. This hypothesis is strengthened by recognition of significant structural changes in the Florida cattle feeding industry since the late 1960s, as large-scale feedlots were developed and smaller-scale feeders declined in importance (Simpson and Baker). Furthermore, yield improvements and new techniques, such as the use of bagasse for silage and feeding of high-moisture corn, have been adopted in the production of Florida feedstuff s. There is no crucial evidence showing differences in investment or operating costs between Florida and the major cattle feeding areas because of the relatively large size feedlots in Florida that allow them to take advantage of substantial economies of size (Simpson, et al.). This paper evaluates the potential effect that increased transportation costs, as a result of higher fuel prices, might have on Florida's competitive cattle feeding position.
Areas of Critical State Concern: Florida's Experience With the Green Swamp
Authors: Kiker Clyde , Lynne Gary D.
Published: July 2016

Public concern has been expressed in most states over the adequacy of present allocative mechanisms to guide land and water use effectively. Private land and water use decisions are seen to have effects far beyond those intended by the decision makers. People intuitively recognize that society's natural resources are not being used to the greatest good when these “spillovers” occur. Ervin et al. (p. 4) have described the situation: “… given our (society's) broader viewpoint where impacts are taken into account which do not enter a firm's profit calculations (or a consumer's), the decision may well be socially inefficient.” The concern about these “spillovers” has led to calls for increased government intervention by way of regulation (Healy and Rosenberg). The implicit assumption is that government action can improve the efficiency of land and water use.
Southern Agriculture in an Era of Expanding Exports
Authors: Clayton Kenneth C.
Published: July 2016

Exports have played an important role in the history of southern agriculture. C. E. Bishop noted more than two decades ago that “southern agriculture has a high stake in international trade.” In recent years, the effects of exports on the southern region have become even more pervasive. Rudd was recently led to observe that “the shift to a substantially greater involvement and interdependency of agriculture in international trade during the 1970s is perhaps the most far-reaching event of [that] decade.”
Economic Growth of the South Versus other Regions: Past Trends and Future Prospects
Authors: Bluestone Herman
Published: July 2016

The dramatic surge of economic activity in the South is a relatively recent development. During the first half of the postwar period, the South, along with the Northeast and North Central region, lagged well behind the nation in population and employment growth (Table 1). It was only in the 1960s that rates of growth in the South began to exceed the national averages, and it was only in the 1970s that the South began to mount a serious challenge to the West for first place in regional growth. It also should be noted that the surge in southern growth was not uniformly distributed; most of it occurred in the region's two western subregions, the East South Central division and the energy-rich West South Central division.
The Agricultural Marketing Agenda for the Eighties
Authors: Ward Ronald W.
Published: July 2016

The agenda for marketing research in the 1980s, to a great extent, has already been set by the events of the 1970s. Agriculture is in a period of transition in which commodity surpluses are expected to be less of a problem area. International markets are expanding, and the delivery systems have become complex in both structure and in the functions performed. The dynamics of the marketplace obviously influence the research agenda.

Before looking at the changing research needs for agricultural marketing, a definition of the concept is needed. For the context of this paper, marketing research is defined to be the process of assimilation and creation of information on the economic performance of potential and existing arrangements that facilitate the assembling, distribution, and consumption of foods, fibers, and ornamentals.
Using Mechanical Trading Systems to Evaluate the Weak Form Efficiency of Futures Markets
Authors: Peterson Paul E. , Leuthold Raymond M.
Published: July 2016

An efficient market has been described by Fama (1970) as one in which prices always fully reflect all available information. Of the three tests of efficiency discussed, the weak form test is concerned with the randomness of price movements and measures the ability to predict future price changes from past and present changes. There are two general ways to evaluate weak form efficiency: statistical tests and mechanical trading rules. Statistical methods, including serial correlation, spectral analysis and nonparametric runs tests, permit hypothesis testing, but Fama and Blume (p. 227) point out that they may be of limited value with complex or irregular price structures.
Estimating Market Power and Pricing Conduct in a Product-Differentiated Oligopoly: The Case of the Domestic Spaghetti Sauce Industry
Authors: Vickner Steven S. , Davies Stephen P.
Published: July 2016

This paper develops a simultaneous-equations panel data econometric model to obtain point estimates of market power and pricing conduct in a representative product-differentiated, oligopolistic food market. The importance of this class of markets is recognized given its prevalence in the food and fiber system, especially for final consumer food products. The $1.3 billion domestic spaghetti sauce industry is featured. Although the results indicate firms exert limited market power, a portion of this power is derived from tacit price collusion. A higher degree of price collusion was found among brands within a market segment than between segments.
Farm Computer Adoption in the Great Plains
Authors: Hoag Dana L. , Ascough James C. , Frasier W. Marshall
Published: July 2016

Computers change rapidly, yet the last survey on computer use in agriculture was in 1991. We surveyed Great Plains producers in 1995 and used logit analysis to characterize adopters and non-adopters. About 37% of these producers use computers which is consistent with the general population. We confirmed previous surveys emphasizing the importance of education, age/experience, and other farm characteristics on adoption. However, we also found that education and experience may no longer be a significant influence. Future research and education could focus on when and where computers are most needed, and therefore when adoption is most appropriate.
Symposium on comparative biology and its bearing on Phanerozoic patterns of evolution: an introduction
Authors: Rhodes Melissa Clark , Vermeij Geerat J.
Published: July 2016

Evolution does not occur in a vacuum. It takes place against a background of changing conditions, some of a climatic or tectonic nature, some created by organisms themselves. The extent to which the rate and direction of evolution are controlled by organisms is the central question in a debate that has been raging for as long as evolution has been part of the intellectual vocabulary of scientists. In an effort to stimulate empirical work on the subject, we organized a symposium on the contributions that functional morphology and comparative physiology are making to paleobiology. The symposium was held as part of the North American Paleontological Convention on July 1, 1992, at the Field Museum of Natural History in Chicago. This issue ofPaleobiologycontains all the submitted and accepted papers presented at the symposium.
Survivorship analysis of Paleozoic Crinoidea: effect of filter morphology on evolutionary rates
Authors: Baumiller Tomasz K.
Published: July 2016

The evolutionary rates of Paleozoic Crinoidea were obtained using dynamic survivorship analysis. The stratigraphic ranges of 838 genera were used in the analyses, revealing a mean generic duration of 12.0 m.y. and a mean species duration of 6.7 m.y., values within the range of longevities reported for other taxa.

Further analyses showed differences in evolutionary rates among crinoid taxa: camerate species and genera were shorter-lived than species and genera of flexibles and inadunates. This pattern may result from ecological differences among these taxa: an energy budget equation solved for crinoids with various filter morphologies revealed that crinoids with fine-mesh filters require higher current velocities to supply them with sufficient particulate nutrients than do crinoids with coarse-mesh filters. A hypothesis stipulating that these differences control the distribution of crinoids among different environments is supported by patterns of occurrence of Mississippian crinoids: the pinnulate camerates (fine filter) dominate higher energy settings while the non-pinnulate inadunates and flexibles (coarse filter) are found in all environments. The “specialized” pinnulate crinoids may therefore be more prone to speciation and extinction than the non-pinnulate “generalists,” thus accounting for the observed differences in the evolutionary rates of the three subclasses.

The above hypothesis was tested by comparing evolutionary rates of two morphological groups: fine-filtered crinoids (camerates) and coarse-filtered crinoids (non-pinnulate Paleozoic crinoids). As predicted, fine-filtered taxa had higher extinction and origination rates. A “bootstrapping” technique revealed that the differences in extinction rates were significant at thep< 0.10 level.
Competition, clade replacement, and a history of cyclostome and cheilostome bryozoan diversity
Authors: Lidgard Scott , McKinney Frank K. , Taylor Paul D.
Published: July 2016

One of the striking yet scarcely documented episodes of clade replacement in the post-Paleozoic fossil record is the decline of cyclostome Bryozoa and the corresponding, rapid diversification of cheilostome Bryozoa. These clades are closely associated morphologically and phylogenetically, and their ecological similarities have previously led to the inference that competition was a primary cause of the overt pattern of replacement. Alternatively, previous compilations of bryozoan families and genera have implied that extinctions at the Cretaceous/Tertiary boundary differentially affected cyclostomes, and thus were also an important factor in the transition.

We first evaluated the ecological context for competition between the two clades, then updated and reexamined the history of absolute family diversity for bryozoans in consecutive geologic stages from Jurassic to Recent. The resulting trends echo the patterns shown in earlier family level compilations, but indicate a slight shift in the frequency of cheilostome family originations from Late Cretaceous to early Paleogene. The relative fall in cyclostome family diversity at the Cretaceous/Tertiary boundary is significantly less than shown in earlier genus level compilations. We then assessed these various compilations of absolute diversity by analyzing species counts and percentages in 728 fossil assemblages, primarily from North America and Europe, over the same time interval. Cyclostome species overwhelmingly dominate assemblages from Jurassic through Cenomanian, then decline significantly in average percentage dominance through the Campanian. Cheilostomes are predominant in Campanian and later assemblages. Cyclostome species percentages do decrease overall through the Tertiary, but this decrease is small and non-uniform, varying around 30%, with a sharp drop in the Late Neogene. Our within-assemblage results indicate that as cheilostomes radiate, their mean species diversity, maximum diversity, and variance all increase, thereby accounting for much of the decline in average percentage of cyclostomes within assemblages. While this result does not exclude a role for competition, an hypothesis of relative decline in cyclostome species richness based on competitive extinction alone seems unlikely. Further, despite decreases in absolute species counts following end-Cretaceous extinctions, within-assemblage percentages of cheilostome or cyclostome species show only slight change relative to one another. Comparison of these and earlier diversity compilations indicates that the dynamics of bryozoan clade replacement may be perceived differently at different ecologic scales or taxonomic ranks.
Symbiotic relationships between worms and solitary rugose corals in the Late Ordovician
Authors: Elias Robert J.
Published: July 2016

Symbiotic relationships involving physical contact between worms and solitary rugosan polyps are recorded by the following structures in North American Late Ordovician corals: (1)Trypanitesborings enclosed within septal swellings in two specimens, (2) vermiform grooves and openings along the external wall of one corallum, and (3) a chamber containing a unique brown tube within one individual. These features are indicative, respectively, of commensal boring polychaete annelids that penetrated through coralla, commensal epizoic worms of unknown taxonomic affinity that attached to the side of a polyp, and a tubicolous worm (possibly a polychaete) that was likely a parasitic endozoan. Symbionts comparable to the latter two types are also known from two specimens of Devonian solitary rugose corals.

Indirect evidence suggests that symbioses between solitary rugosans and the worms that producedTrypanitesborings as dwelling structures in the sides of coralla were relatively common. However, direct evidence that the hosts were alive has been found in only two corals. In both cases, worms bored through septa within the calices and came into contact with basal surfaces of the polyps, which secreted skeletal material that sealed off the intruders. The rarity of such structures suggests that the encounters were inadvertent. If boring worms favored upcurrent portions of objects in order to maximize feeding benefits and avoid sedimentation, their locations indicate that the concave sides of curved coralla faced toward prevailing currents when in life positions.

“Opportunistic” worms are known to have attached to the sides of polyps only in rare instances when the hosts became temporarily exposed as a result of accidents or abnormalities. This indicates that coralla normally served to shield polyps from colonization by nonboring epizoans.

Worms that apparently extended up through openings in basal surfaces of polyps likely obtained sustenance parasitically within the central cavities. They could have entered the hosts through their mouths, or via the calices when parts of the polyps detached from their coralla and contracted radially. The rarity of this type of relationship in solitary Rugosa suggests that the worms entered inadvertently.

Symbioses involving physical contact between worms and polyps seem to have been rare throughout the history of solitary rugose corals. Both groups apparently tolerated such associations when they did occur, although the rugosans secreted structures in their coralla that served to isolate the symbionts. In doing so, they recorded the presence of worms not likely to be preserved as body fossils. The interpretation of such features provides information on the physiology and ethology of both organisms, on the history of symbiotic relationships, and on the diversity of soft-bodied organisms in ancient environments.
Population size, extinction, and speciation: the fission effect in Neogene Bivalvia
Authors: Stanley Steven M.
Published: July 2016

The extinction of a species represents reduction of both geographic range and population size to zero. Most workers have focused on geographic range as a variable strongly affecting the vulnerability of established species to extinction, but Lyellian percentages for Neogene bivalve faunas of California and Japan suggest that population size is a more important variable along continental shelves. The data employed to reach this conclusion are Lyellian percentages for latest Pliocene (∼2 ma old) bivalve faunas of California and Japan (N = 245 species). These regions did not suffer heavy extinction during the recent Ice Age, and for each region the Lyellian percentage is 70%–71%.

Discrepancies in population size appear to explain the following differences in survivorship to the Recent (Lyellian percentage) for three pairs of subgroups: (1) burrowing nonsiphonate species (42%) versus burrowing siphonate species (84%), which suffer less heavy predation; (2) burrowing nonsiphonate species of small size (73%) versus burrowing nonsiphonate species of large body size (96%); (3) Pectinacea (30%) versus other epifauna (71%), which suffer less heavy predation. During the Mesozoic Era, when predation was less effective in benthic settings, mean species duration for the Pectinacea was much greater (∼20 ma).

Along the west coast of North and Central America, mean geographic range is greater for siphonate species of large body size than for siphonate species of small body size and greater still for pectinacean species. These ranges are inversely related to mean species longevity for the three groups, which indicates that geographic range is not of first-order importance in influencing species longevity. Species with nonplanktotrophic development neither exhibit narrow geographic ranges along the west coast of North and Central America nor have experienced high rates of extinction in California and Japan.

Rates of extinction are so high for Neogene pectinaceans and nonsiphonate burrowers that without enjoying high rates of speciation these groups could not exist at the diversities they have maintained during the Neogene Period. They are apparently speciating rapidly because of the fission effect: the relatively frequent generation of new species from populations that are fragmented by heavy predation. Thus, ironically, there may be a tendency for high rates of speciation to be approximately offset by high rates of extinction. Only if mean population size for species in a particular group becomes extremely small is it likely to result in a high rate of extinction and a low rate of speciation—and hence a dramatic decline of the group. The fission effect may contribute to the general correlation in the animal world between rate of speciation and rate of extinction.
Energy, ecology, and cotton rat evolution
Authors: Martin Robert A.
Published: July 2016

Body mass is estimated for extinct species of Sigmodon. These data are then used in appropriate equations derived among Recent mammals to estimate a suite of physiological and ecological variables which are followed through almost 4 ma of cotton rat history. A statistical trend towards large size is documented. Despite large swings in population size and other parameters, hypothetical values of population metabolism remain virtually constant, suggesting negligible population energetic benefit to size change in either direction. Studies of extant cotton rats and unrelated taxa sharing the same adaptive zone suggest that there is now, and has been in the past, negligible thermoregulatory advantage to modification of cotton rat body mass. Large size appears to be associated in Sigmodon with heightened aggression to the point that two species, particularly if of dichotomous size, cannot coexist in the same microhabitat. At least with regard to cotton rats, this conclusion represents a challenge to the comfortable hypotheses of coevolution and character displacement. The overall trend toward large size during Pleistocene time is considered then as the interplay of selection acting to favor large size in areas of sympatry and stochastic processes originating cotton rat populations of different body size. Because morphology and ecological strategies are stable within the cotton rat adaptive zone for millions of years, it is suggested that mammalian speciation events that result in exploitation of a new adaptive zone are uncommon and occasionally cross higher taxonomic categories. These events are defined as first-order speciation events, in contrast to second-order events that occur in clades within the same adaptive zone.
Constraints of ligament growth, form and function on evolution in the Arcoida (Mollusca: Bivalvia)
Authors: Thomas R. D. K.
Published: July 2016

Growth processes and patterns set functional limits on the adaptive range of organisms that have evolved a particular “Bauplan.” The design of the elastic ligament has played a large part in determining the scope of the evolutionary radiation of the Arcoida. Tensional lamellar and compressional fibrous materials of this ligament, which appear to be similar in their elastic properties to those of other bivalves, are not segregated in positions where they could best perform their different mechanical functions. The growth of this unspecialized ligament exhibits strong positive allometry, with respect to shell size, in many fossil and living arcoids. A simple mechanical model shows that this allometry is essential if the strength of the ligament is to keep up with the weight of the animal, during ontogeny. Inherent disadvantages of the allometry include increasing dorsal breakage of the ligament itself, interference with the function of the hinge teeth and reduction of the closing moment exerted by the adductor muscles. Direct measurements of living arcoids show that allometric growth just maintains a linear relationship between ligament strength and animal volume. Major differences in ligament strength are related to shell growth patterns and substantially different environmental adaptations. Ligament strength is highly variable within individual populations; between populations, it is correlated with shell thickness and local environmental conditions. Most arcoids are adapted for shallow-burrowing or epifaunal modes of life in physically unstable environments, where they are frequently disturbed. The large, muscular foot enables these mobile animals to regain suitable living positions after such disturbances. The weak ligament has limited the potential specialization of the arcoids for either deeper burrowing or permanent epibyssal attachment, also requiring the retention of the foot in epifaunal forms. This ligament has made diverse adaptations possible, while preventing extreme specialization, except in isolated taxa. As such, it is largely responsible for the evolutionary reversals documented by Stanley (1972). This is konstrukionsmorphologie No.46.
Relationship between diatoms in surface sediments of the Atlantic Ocean and the biological and physical oceanography of overlying waters
Authors: Maynard Nancy G.
Published: July 2016

The number of diatom valves and fragments per gram of surface sediment in the Atlantic Ocean accurately reflects diatom abundance in the overlying waters, without any evidence of significant lateral drift during settling to the sea bottom. The distribution pattern of the number of resting spores per gram is similar to that for the whole and fragmented diatom valves. Fresh water diatoms and opal phytoliths are abundant in the sediments off the west coast of Africa where they have been deposited by the Trade Winds.

Despite the relatively small number of core tops analyzed, the abundance and distribution patterns of diatoms in the sediments exhibit striking similarities to the patterns of primary productivity, phosphates, and annual production of silica in suspension in surface waters. Areas with high phosphate values and primary productivity and, therefore, areas of upwelling can be inferred from the quantitative distribution of diatoms in the sediments. Q-mode factor analysis, based on the abundance of forty-two species in thirty-seven core tops, produced six diatom species assemblages whose distributions provide additional information on the positions of certain water masses and major currents.

Since the data on the quantitative distribution of diatom valves as well as on the diatom assemblages in the sediments of the Atlantic Ocean today allow prediction of certain water mass characteristics and circulation patterns of the overlying waters, they therefore, permit the reconstruction of paleoceanographic circulation patterns in ancient Atlantic Oceans, using the diatom distribution in sediments from dated horizons.
Why does a larva swim so long?
Authors: Strathmann Richard R.
Published: July 2016

In recent articles in this journal Hansen (1980) and Jablonski (1980) discussed the planktonic larval stages of fossil benthic invertebrates and the relation of type of larval development to geographic ranges, nearshore-offshore position, speciation, and extinction. The fossil record provides a view of long term consequences of types of larval development, and the emphasis of these, and other, paleobiological studies was on selection among species which are characterized by different developmental adaptations.
The Modern Synthesis is Partly Wright
Authors: Orzack Steven Hecht
Published: July 2016

Gould (1980) claims that a “new and general theory of evolution” is emerging. He examines the modern synthesis and asserts that it is being rejected by present day evolutionary biologists. The purpose of this note is to show that Gould's view of the modern synthesis is distorted. Any rejection of the modern synthesis must rest on a more balanced characterization than that presented by Gould.
Punctuated equilibrium and evolutionary stasis
Authors: Schopf Thomas J. M.
Published: July 2016

Writers as disparate in professional interest as those describing speciation in Drosophila, predicting weather, or supporting creationism have all recently focused on the “sudden” appearance of taxa in the geologic record. In the process, each has cited the punctuated equilibrium argument. Owing to the enormously wide attention which this issue has received since its introduction almost a decade ago, it seems worthwhile to try to place the paleontological and biological evidence in a 1981 perspective. The focus I have chosen is to try to analyze the issue, much as in recent columns in Current Happenings on competitive exclusion, and on larval dispersal and biogeography, in which are put forth alternative explanations for a set of data on a general problem.
Phyletic gradualism in a Late Cenozoic planktonic foraminiferal lineage; DSDP Site 284, southwest Pacific
Authors: Malmgren Björn A. , Kennett James P.
Published: July 2016

Shape measurements have been made on planktonic foraminifera from a South Pacific Late Miocene to Recent temperate evolutionary lineage (Globorotalia conoidea through intermediate forms to G. inflata in DSDP Site 284). The sampling interval is about 0.1 Myr over nearly 8 Myr. Gradual evolution (phyletic gradualism) clearly occurs in all but one measured parameter. No clear evidence exists for abrupt evolutionary steps (punctuated equilibria) within the bioseries. If they occur, they are the exception rather than the rule. The number of chambers in the final whorl decreases almost linearly, despite known paleoceanographic oscillations within the temperate water mass. Mean size and apertural shape variations seem to correlate with paleoceanographic change. It is speculated that certain major morphological changes that took place within this evolutionary bioseries (i.e. loss of keel, rounding of periphery) developed in response to a major latest Miocene cooling, associated with instability in the water column and resulting adjustments of the test structure to water density changes. Changes exhibited in shape measurements may offer a precise method of stratigraphic correlation between temperate South Pacific Late Cenozoic sequences. Four species and two subspecies, long recognized to form the basis of this lineage, are redefined biometrically.
Neutral Hypotheses and Patterns of Species Diversity: Fact or Artifact?
Authors: Thomas William R. , Foin Theodore C.
Published: July 2016

Species diversity is a product of both biological interactions and physical-geographic factors. A model which eliminates biological interactions as a determinant of diversity can be used to assess the potential impact of physical and geographic factors operating alone on temporal trends in diversity (succession) and on spatial differences along latitudinal or environmental gradients. If a biologically neutral model can generate diversity patterns similar to those we observe, it can be argued that traditional hypotheses which depend on biological interactions are not the most parsimonious explanations for diversity patterns. If the neutral model approach supports a spectrum of possible hypotheses, perhaps the entire concept of species diversity can be discarded as a useful measure of community structure.

An earlier analysis of this type supported the notion that diversity patterns can be adequately explained by physical disturbance, global geography gradients, and stochastic immigration and extinction events. Our neutral model analysis does not affirm this view. We argue that the coarse level at which simple colonization models operate does not permit strong conclusions regarding the underlying mechanisms. Detailed community analyses may provide the best evidence for the nature of structuring processes. Based on the evidence available in the literature, species diversity is likely to be generated by a small number of biological processes interacting with physical-geographic gradients.
Population Dynamics of the Three-Toed Horse Neohipparion from the Late Miocene of Florida
Authors: Hulbert Richard C.
Published: July 2016

A late Miocene population of Neohipparion cf. leptode from the Love Bone Bed of Florida was found to have 13 discrete annual age classes based on eruption sequences and tooth wear. The large sample size of individuals (minimum number = 229) allowed the estimation of standard population parameters, including age-specific mortality rates. The average age of death for a newborn was 3.5 years, but those individuals that survived the 64% juvenile mortality occurring during the first two years lived an average of 8.0 years. The potential longevity of this species of Neohipparion had not increased beyond that of known samples of Merychippus, despite increased crown height. The paleoenvironment of the collecting site was a wooded grassland savanna with annual wet and dry seasons. The Neohipparion population migrated into the area during the dry season but left in the wet season to give birth away from the collecting site.
Do centers of origin have a center?
Authors: Briggs John C.
Published: July 2016

A current question being debated with considerable intensity is whether or not certain geographic areas act as centers of evolutionary radiation and supply species to other areas that are less active or less effective in an evolutionary sense. Darwin (1859) was the first to write about centers of origin which he called “single centers of creation.” He argued that each species was first produced within a single region and that it subsequently migrated from that area as far as its powers of migration and subsistence under past and present conditions permitted. Adams (1902), in discussing the influence of the southeastern United States as a center of distribution for the flora and fauna of North America, provided a series of criteria for the determination of “centers of dispersal.” His first, and evidently most important criterion was the location of “the greatest differentiation of a type.”
Planar branch systems in colonial suspension feeders
Authors: McKinney Frank K.
Published: July 2016

Among the various forms developed by marine colonial filter feeders, erect colonial fans have evolved in representatives of several phyla. Branches are relatively narrow, evenly spaced from one another, proliferate by bifurcation, and in most colonies continue from their point of origin to the distal margin of the colony. Their narrowness and uniform placement is apparently related to filling an area with multiple tentacle bells of similar size. The major architectural problem for such a colonial suspension feeder seems to be construction of a sheet composed of narrow branches such that water may be filtered as it flows through the sheet, between branches.

The simplest form of the filtration sheets is a uniformly expanding wedge, in which new branches originate at regular intervals from the point of origin of the wedge. Variation in rate of addition of new branches results in more complex forms, such as paraboloids, flaring fans, spirals, and highly folded sheets.