Natural history and evolution of paper-wasps

Journal ArticlePaper-wasps occupy a special place in the history of animal behavior. Temperate species o f Polistes are large, beautiful, intelligent, adaptable, easy to observe, and thoroughly committed to social life. They are also aptly named, being intensely political, in the limited sense that any nonhuman animal may be said to be political. Although they lack parties, states, and ideologies, their power struggles seem eerily familiar to anyone who watches closely enough to see the protagonists as individuals

Intraspecific resource competition as a cause of sympatric speciation

Journal Article[In most models of speciation], the fitness value of an animal is determined by the genotype it has, and the habitat in which it lives. In a more realistic model it should also depend on how much necessary resource is available for the animal and the competition from other genotypes for this resource. Models can be constructed which take into account such competition between genotypes. In a special case one can find the exact conditions for the stable coexistence of two incipient species, which have some degree of gene flow between them but also slightly different resource utilization distributions. An interesting property of this class of models is that they show how sympatric speciation can occur in a species where all animals live in the same habitat and under the same fitness regime, but differ, due to their genetic constitution, in their resource utilization

Evolution of individuality by Leo W. Buss

Journal ArticleMetazoans seldom reproduce vegetatively; they often die of cancer; and they almost always sequester their germ lines. Plants often reproduce vegetatively, seldom die of cancer, and almost never sequester a germ line. Buss argues that these and many other patterns can all be understood in a unified way as the evolutionary outcomes of conflicts that occur during development among genetically variant cell lines

Conditional relatedness, recombination, and the chromosome numbers of insects

Book ChapterIf two polymorphic loci are out of phase equilibrium, a homozygote at one of these loci is more highly related to its kin, at the other locus, than is an equivalent heterozygote. As a result, selection can favor (1) phenotypic responses to relative heterozygosity, and (2) increased recombination between the loci inducing these responses. Selection is expected to have these consequences only to the extent that kin strongly affect each other's fitnesses. The chromosome numbers of social insects appear to be higher, on average, than those of allied solitary species, which is consistent with this model on the assumption that chromosome numbers are selected in part for their effects on recombination

Numerical method for estimating coefficients of relationship in a langur troop

Journal ArticleThe average coefficient of relationship ( r ij) among the members of a social group is expected to influence the evolution of any trait that affects the average fitness of group members other than the bearer of the trait. It is usually impossible to write a general expression for r ij , because it depends on a large number of variables, including the means and variances of group size, age-specific reproduction and mortality for males and females (lx and mx schedules), and migration rates (both into and out of the group, for males and females, by age), as well as other features of the mating system such as patterns of assortative or disassortative mating. Fortunately, tractable numerical methods are easy to devise for some special cases. This appendix describes a method that was used to estimate rij among the adult females of a hypothetical troop modeled after the langurs of the Mount Abu region

1998 Sewall Wright Award: William Donald Hamilton

Journal ArticleThe Sewall Wright Award was established in 1991 to honor active investigators who have contributed in especially significant ways to the conceptual unification of the biological sciences. This year's recipient is William D. Hamilton of Oxford University. Beginning in the 1960s with his papers on the theory of inclusive fitness and the evolution of eusociality, Bill Hamilton's publications have permanently changed the landscape of ideas and interpretation surrounding a wide range of biological phenomena. His papers have clarified murky problems, generated new research agendas, and unified our understanding of many central concepts, on a truly revolutionary scale

Evidence for a cryptic species complex in the ant parasitoid Apocephalus paraponerae (Diptera: Phoridae)

Journal ArticleCryptic species complexes occur in many taxa, in particular in the insect order Diptera. Here we describe a possible new cryptic species complex in the family Phoridae. Three lines of evidence suggest that Apocephalus paraponerae, an ant parasitoid, is actually a complex of at least four genetically distinct but morphologically almost indistinguishable populations attacking at least three different ant hosts. First, the host-location cues used by A. paraponerae to locate two of the host species differ. Second, A. paraponerae attracted to these two ant host species differ consistently in average hind femur length and costal vein length, two measures of body size. Finally, mtDNA sequence comparisons of individuals from a variety of locations and host ant species indicate high sequence divergence between populations and low sequence divergence within populations. We discuss aspects of host location behaviour that may be important in cryptic species formation, and we speculate that many such cryptic complexes may exist in this family and others with similar mechanisms of host location and exploitation

Models of sex ratio evolution

Journal ArticleOur understanding of sex ratio evolution depends strongly on models that identify: (1) constraints on the production of male and female offspring, and (2) fitness consequences entailed by the production of different attainable brood sex ratios. Verbal and mathematical arguments by, among others, Darwin, Dusing, Fisher, and Shaw and Mohler established the fundamental principle that members of the minority sex tend to have higher fitness than members of the majority sex. They also outlined how various ecological, demographic and genetic variables might affect the details of sex-allocation strategies by modifying both the constraints and the fitness functions. Modern sex-allocation research is devoted largely to the exploration of such effects, which connect sex ratios to many other aspects of the biologies of many species

Parasites and sex

Book ChapterParasites of many kinds have long been recognized as important regulators of population size (e.g., May, 1983b), but only during the last decade or two have they been widely viewed as the protagonists in fast-paced (and long-running) evolutionary thrillers involving subtle features of the biochemistry, anatomy, and behavior of their hosts. On this view, their power as agents of evolution derives from their ubiquity and from the great amounts of mortality they can cause (which are also the properties that make them effective agents of population regulation) and, just as importantly, from their imperfect (but improvable) abilities to defeat the imperfect (but improvable) defenses of their hosts. Thus each party is expected to experience the other as a changeable (and generally worsening) part of its environment

Sexual dimorphism in the Hymenoptera

Journal ArticleSpectacular sex differences of many kinds occur abundantly among the wasps, bees and ants that make up the insect order Hymenoptera. In some cases these differences are so extreme that males and females of the same species have been classified in different genera for decades, until a chance observation of mating, or emergence from a single nest, establishes their identity. Even where the sexes are similar in morphology they lead very different lives. The hard-working females hunt for prey or other larval provisions, and in many taxa they carry these provisions back to a nest that they have constructed to protect their offspring. The males, by contrast, lead short lives (sometimes nasty and brutish), devoted to the single purpose of inseminating females. Countless variations on this theme have evolved during the long and successful history of the order, and other features of hymenopteran biology have allowed these sex differences of ecology to be translated into equally striking sex differences of behavior, morphology and physiology