DIVERGENT AMBULATORY AND GROOMING BEHAVIOR IN SERIALLY BOTTLENECKED LINES OF THE HOUSEFLY

The extent of genome-wide restructuring predicted in bottleneck models of speciation is addressed in assays of non-reproductive behavior in lines of the housefly. After five serial founder-flush cycles of one of three sizes (1, 4, or 16 pairs), each bottleneck line showed significant differentiation from the outbred control in ambulatory levels and grooming sequences in videotaped records of precopulatory activity. Only one line (4-pair) showed overall lethargy which was associated to inbreeding depression in egg-to-adult viability, thus exemplifying a case of probable extinction due to bottlenecks. The two most hyperactive lines (1- and 16-pair) showed very similar directions of differentiation from the control in locomotor activity and grooming behavior, as well as in mating behavior evaluated from a separate study. This high congruence suggested that directional selection toward the phenotypic optima of the ancestor operated on the bottleneck populations and that a 10-fold difference in theoretical inbreeding coefficients did not affect the magnitude of response. The remaining two bottleneck lines showed some independence from these general trajectories, their divergence along minor axes of ancestral intercorrelation structure possibly being more important to the formation of new species. Significant perturbations of the thresholds for execution of grooming and locomotor movements suggested increased evolutionary potential for ritualization (i.e., sexual selection for adoption of non-reproductive behavior into courtship repertoire) due to bottlenecks.     

THE EVOLUTIONARY ECOLOGY OF AN ANTIPREDATOR REACTION NORM: DAPHNIA PULEX AND CHAOBORUS AMERICANUS

Ponds containing the parthenogenetic zooplankter Daphnia pulex with and without chaoborid predators were sampled over the course of a season. A significant (P < 0.05) Spearman rank correlation was found between predator density and the expression of an antipredator defense (neckteeth) by the Daphnia. The reaction norms (percent induction of a single genotype versus predator density) of clones isolated from predator-free and predator-rich habitats were determined in a laboratory setting. There was a statistically significant different response among the six clones tested (P < 0.05). Clones isolated from chaoborid ponds showed significantly greater sensitivity to the presence of predator than clones from predator-free ponds (P < 0.05). In the laboratory, food levels under which prey were cultured affected induction of the antipredator response. Highest induction was found at the lowest food level used.     

Relationships among didelphid marsupials based on sequence variation in the mitochondrial cytochrome B gene

Variation in the mitochondrial cytochrome b gene (nucleotide and amino acid sequences) is evaluated for 9 genera and 15 species of American opossums in the family Didelphidae, using the American caenolestid rat opossumLestoros and the New Guinean peroryctid bandicootEchimypera as outgroups. Phylogenetic analyses (parsimony and distance) strongly support the monophyly of the Didelphidae and delineate two major clades; (1)Didelphis andPhilander are strongly aligned sister taxa, withMetachirus weakly but consistently associated with them, and (2)Marmosa plusMicoureus, withMonodelphis falling outside that pair. The generaMarmosops, Caluromys, andGlironia exhibit varied relationships, depending upon the method of analysis and data (DNA or amino acid sequences) used, but generally are placed individually or in combinations near or at the base of the didelphid radiation. Some aspects of these relationships are consistent with current taxonomic views, but others are in marked contrast. Specifically, a clade comprised of the mouse opossumsMarmosa, Micoureus, andMarmosops is strongly rejected by log-likelihood analysis, contrary to expectations from some current classifications. Also, the woolly opossumsCaluromys andGlironia also do not form a sister-taxon relationship, as suggested by their placement in a subfamily separate from the remaining didelphids examined. However, such a relationship cannot be rejected from log-likelihood analyses. The relationships suggested fromcyt-b sequences are strongly concordant with those based on DNA-DNA hybridization analyses. In addition to systematic and phylogenetic properties, molecular evolution of the didelphid cytochrome b gene sequence is characterized according to nucleotide bias and rate differentials at each codon position and across the entire sequence.To whom correspondence should be addressed.     

Moral Darwinism: Ethical evidence for the descent of man

Could an ethical theory ever play a substantial evidential role in a scientific argument for an empirical hypothesis? InThe Descent of Man, Darwin includes an extended discussion of the nature of human morality, and the ethical theory which he sketches is not simply developed as an interesting ramification of his theory of evolution, but is used as a key part of his evidence for human descent from animal ancestors. Darwin must rebut the argument that, because of our moral nature, humans are essentially different in kind from other animals and so had to have had a different origin. I trace his causal story of how the moral sense could develop out of social instincts by evolutionary mechanisms of group selection, and show that the form of Utilitarianism he proposes involves a radical reduction of the standard of value to the concept of biological fitness. I argue that this causal analysis, although a weakness from a normative standpoint, is a strength when judged for its intended purpose as part of an evidential argument to confirm the hypothesis of human descent.     

Uncertain branch lengths, taxonomic sampling error, and the egg to body size allometry in temperate butterflies (Lepidoptera)

The allometry of egg to body size in temperate butterflies, and the relationships between egg size and larval host structure, taxonomy, voltinism, and duration of the egg stage, are investigated using cross-species analysis and the comparative analysis of independent contrasts. In addition, the effect of two sources of uncertainty that may affect continuous data when treated under a statistical, comparative, framework, is assessed: (1) unknown evolutionary distances, and (2) taxonomic representativity (proportion of species of a given taxon, from which data are available). It is suggested that the effects of taxonomic under-representation could be important in comparative, quantitative studies, but this problem may be tempered by means of weighted regression. Under the assumption that taxonomy represents butterfly phylogeny, egg and adult body size are related by negative allometry (i.e. the slope of the line fitted to the logarithmically transformed data is lower than 1.0). However, the precise slope (0.2-0.9) depends on the method used, branch lengths, and taxonomic sampling. There is evidence for a relationship between a species' voltinism and the number of days it spends in the egg stage, as well as between adult butterfly size and the gross structure of the plants used as larval hosts (woody plants or herbs). Egg size proves to be related to foodplant taxonomy, voltinism, and duration of the egg stage when the data are analysed using species means, but these relationships become non-significant when the comparative method is employed.     

Pathways in the emergence of developmental neuroethology: Antecedents to current views of neurobehavioral ontogeny

The historical forces that have contributed to our current views of neurobehavioral development (and thus to the fields of developmental psychobiology and neuroethology) are many and varied. Although similar statements might be made about almost any field of science, it is in particular true of this field, which represents a kind of mongrel discipline derived from at least three major sources (psychology, embryology, and neuroscience) and several more minor ones (including developmental psychology and psychiatry, psychoanalysis, education, zoology, ethology, and sociology). Although I attempt to demonstrate here how each of these sources may have influenced the emergence of a unified field of developmental psychobiology or developmental neuroethology, because the present article represents the first attempt of which I am aware to trace the history of these fields I am certain that there is considerable room for improvement, correction, and revision of the views expressed here. Accordingly, I consider this inaugural effort a kind of reconnaissance intended to trace a necessarily imperfect historic path for others to follow and improve upon. In the final analysis, I will be satisfied if this article only serves to underscore two related points: first is the value derived from historical studies of contemporary issues in development, and the second concerns the extent to which our current ideas and concepts about neurobehavioral development, ideas often considered new and contemporary, were already well known to those who came before us. The first point underscores the arguments expressed in the Introduction that the present must always be reconciled with the past, for the past is never entirely past. The second point returns full circle to an important thought expressed in the opening quotation to this article, namely, that even though our historic predecessors lacked much of the empirical facts available to us they were nonetheless able to attain a surprisingly deep understanding of neurobehavioral ontogeny. © 1992 John Wiley & Sons, Inc.     

DISCOVERY OF MONOGRAPTIDS IN BASAL PART OF LOWER SILURIAN FROM S. ANHUI WITH SPECIAL REFERENCE TO THEIR ORIGIN

For a long time, the evolutionary series of a idoraptids-dimorphograptids-monograptids has been generally recognized by graptolite researchers. In the past years, the akidograptids were found to appear in the Lower Silurian Parakidograptus acuminatus Zone, while the dimorphograptids in the P. acuminatus and Orthograpius vesiculosus Zones, but the monograptids appeared as late as in the O. vesiculosus zone; this evolutionary series can be easily accepted by other people. Chen Xu and Lin Yao-kun (1978) pu...     

Was globin evolution very rapid in its early stages?: A dubious case against the rate-constancy hypothesis

Summary Goodman et al's (1975) claim of accelerated evolution in the early stages of globin evolution is based on an erroneous assignment of the time of divergence of vertebrate myoglobin and hemoglobin. When this is corrected, there is no basis for their claim. The data are much more consistent with the nearly constant rate expected on the neutral mutation-random drift hypothesis than with the uneven rates expected if most amino acid changes were caused by substitution of favorable mutants through Darwinian selection. In addition, the majority of the codons determined by their maximum parsimony method have turned out to be wrong when compared to the actual nucleotide sequences of rabbit and human hemoglobins determined by direct sequencing.Contribution No. 1314 from the National Institute of Genetics, Mishima, 411 Japan.