Leigh Van Valen

Homology and causes

Homology is resemblance caused by a continuity of information. In biology it is a unified developmental phenomenon. Homologies among and within individuals intergrade in several ways, so historical homology cannot be separated sharply from repetitive homology. Nevertheless, the consequences of historical and repetitive homologies can be mutually contradictory. A detailed discussion of the rise and fall of the “premolar‐analogy” theory of homologies of mammalian molar‐tooth cusps exemplifies such a contradiction. All other hypotheses of historical homology which are based on repetitive homology, such as the foliar theory of the flower considered phyletically, are suspect.

Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation

Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of dinosaurs, and Paleocene pollen. The top of this channel is 1.3 meters above the likely position of the iridium anomaly, the Cretaceous/Tertiary boundary.

Multivariate structural statistics in natural history

Abstract Some multivariate statistics usually used for structural purposes are inappropriate for this. The total variance and derived parameters, some new, measure multivariate variation. The two major properties of correlation must be generalized differently: the total correlation for joint dependence and the tightness . The term coregression refers to the trend of two mutually dependent variables. A generalization of information theory permits estimation of the redundance produced by correlations among many continuous variables. A new parameter, the modality , expresses the non-uniformity of a set of metric points. A suitable distance among populations can be determined in the general bivariate case and, approximately, in most realistic multivariate cases.

Molecular evolution as predicted by natural selection

SummaryThe major difficulty with selectionist explanations of molecular evolution has been their lack of a prediction of roughly constant evolutionary rates. A new selectionist theory (the Red Queens Hypothesis), motivated by paleontology and derivable ecologically, makes such a prediction directly. Not all its other predictions are now verified. The counter-intuitive theory presupposes that an increase in momentary fitness by one species causes an equal total decline in momentary fitness among ecologically interacting species. Although some arguments for the selectionist approach seem invalid, this general approach remains plausible.

The Statistics of Variation

Publisher Summary This chapter reviews univariate and multivariate measures of variation, for both absolute and relative variation. Biologists almost never test variation appropriately; in particular, the F test should never be used for this purpose. There are, however, several useful and robust tests that apply, with modifications, to all useful measures of variation, including the multivariate coefficient of variation. Some of these applications are little known or new. A measure of the effective dimensionality of variation permits the relative variation of quantities such as volumes to be compared with that of linear measurements. Several measures exist for the tightness of a distribution in two or more dimensions, one of which generalizes this property of the correlation coefficient. Measurement error is part of observed variation and can be subtracted from it. ABSTRACT Univariate and multivariate measures of variation are reviewed, for both absolute and relative variation. Biologists almost never test variation appropriately; in particular, the F test should never be used for this purpose. There are, however, several useful and robust tests that apply, with modifications, to all useful measures of variation, including the multivariate coefficient of variation. Some of these applications are little known or new. A measure of the effective dimensionality of variation permits the relative variation of quantities such as volumes to be compared with that of linear measurements. Several measures exist for the tightness of a distribution in two or more dimensions, one of which generalizes this property of the correlation coefficient. Measurement error is part of observed variation and can be subtracted from it.

Red Queen: from populations to taxa and communities

Biotic interactions via the struggle for control of energy and the interactive effects of biota with their physical environment characterize Van Valens Red Queen (VRQ). Here, we review new evidence for and against a VRQ view of the world from studies of increasing temporal and spatial scales. Interactions among biota and with the physical environment are important for generating and maintaining diversity on diverse timescales, but detailed mechanisms remain poorly understood. We recommend directly estimating the effect of biota and the physical environment on ecological and evolutionary processes. Promising approaches for elucidating VRQ include using mathematical modelling, controlled experimental systems, sampling and processes-oriented approaches for analysing data from natural systems, while paying extra attention to biotic interactions discernable from the fossil record.

The History and Stability of Atmospheric Oxygen

There are three processes weakly concentration-dependent that keep changes in concentration of atmospheric pressure from being a random walk—inhibition of net photosynthesis by oxygen, the passage of hydrogen through the oxidizing part of the atmosphere before it escapes from the earth, and burial of reduced carbon in anaerobic water. A stronger regulator seems desirable but remains to be found. The cause of the initial rise in oxygen concentration presents a serious and unresolved quantitative problem.

Predation and species diversity.

Except for doubtful interactions with interference competition and density-dependent extinction, equivalent predation cannot increase the number of species of prey.

An analysis of developmental fields

Abstract Critical examination of variation of appropriate adult structures can give information on their ontogeny. In a Cretaceous insectivore, the patterns of serial variation of cheek tooth structures exhibit many kinds of morphological gradients. All these observed gradients can be explained by a minimum of two or three embryological gradients acting on a prepattern that is common to each tooth primordium. Three dichotomous signals are necessary for other features. Thus the simplest program of dental ontogeny can be derived. Extensions, tests, and other matters are discussed.

Species, sets, and the derivative nature of Philosophy

Concepts and methods originating in one discipline can distort the structure of another when they are applied to the latter. I exemplify this mostly with reference to systematic biology, especially problems which have arisen in relation to the nature of species. Thus the received views of classes, individuals (which term I suggest be replaced by “units” to avoid misunderstandings), and sets are all inapplicable, but each can be suitably modified. The concept of fuzzy set was developed to deal with species and I defend its applicability. Taxa at all levels are real and participate in biological processes. Analysis of cause and pattern provides the deep structure in which metabiology is grounded; violation of this principle has led to diverse errors in biology.