Within-species differences in primate social structure: evolution of plasticity and phylogenetic constraints

Primate socioecological studies have attempted to derive general frameworks using the average behavioural traits of species or genera to place them into categories. However, with the accumulation of primate studies, it is timely to place more emphasis on understanding within-species variation in social structure. In this review we have four objectives. First, we examine within-species variation in the potential determinants of social structure, including diet, demography, predation and infanticide, and document considerable variation. Second, we present case studies of within-species variation in social structure to illustrate the potential magnitude of this variation. For example, there are cases within a single interbreeding population where multi-male, uni-male, fission–fusion and monogamous groups are found. Third, by examining widespread primate lineages that occur in a variety of habitats, we note that there are differences in the magnitude of variation in social structures across different lineages and as a result we consider phylogenetic constraints on phenotypic variation in social structure. Finally, we reflect on the implications of extensive variation in social structure. We suggest that primate social structure will represent a combination of adaptation to present-day environment and phylogenetic inertia. To advance our understanding of the relative contribution of phylogeny versus ecology we propose two approaches. One approach is to compare groups in the same interbreeding population that inhabit different ecological conditions. Any differences that are found can be attributed to ecological differences, since phylogeny should not play a role within a single population. The second approach is to study distantly related species that have similar social structures to illustrate how similar ecological pressures might be operating to select for parallel social structures.     

How genes causing unfit hybrids evolve within populations: a review of models of postzygotic isolation

 The main subject for models of postzygotic isolation has been how reproductive isolation genes (RI genes) which cause hybrid inviability or sterility spread within populations despite their deleterious effects. The models are divided into three categories according to the within-population effect of RI genes in their fixation process. (1) The beneficial effect model, where RI genes are assumed to spread within populations by a positive selective force via natural or sexual selection. (2) The neutral effect model, where RI genes are assumed not to affect the fitness of individuals in their fixation process and to be spread by genetic drift. (3) The deleterious effect model, where RI genes are assumed to exhibit some (slightly) deleterious effects in their fixation process and to be spread by genetic drift. Factors that affect the applicability of these models are discussed. If a selective force such as sexual conflict or natural selection facilitates the evolution of RI genes, the beneficial effect model should be applied. Many empirical studies have suggested that positive selection plays an important role in the evolution of hybrid male sterility. If the mutation rates of RI genes are low, and the specificity of epistatic interaction causing hybrid inviability or sterility is high, the neutral effect model should be applied. However, if the opposite condition applies, the deleterious effect model should be applied. Received: February 7, 2002 / Accepted: October 17, 2002 Acknowledgments We are grateful to two anonymous reviewers and the editor for helpful comments and suggestions. Correspondence to:T.I. Hayashi     

Mathematical modelling of the intravenous glucose tolerance test

 Several attempts at building a satisfactory model of the glucose-insulin system are recorded in the literature. The minimal model, which is the model currently mostly used in physiological research on the metabolism of glucose, was proposed in the early eighties for the interpretation of the glucose and insulin plasma concentrations following the intravenous glucose tolerance test. It is composed of two parts: the first consists of two differential equations and describes the glucose plasma concentration time-course treating insulin plasma concentration as a known forcing function; the second consists of a single equation and describes the time course of plasma insulin concentration treating glucose plasma concentration as a known forcing function. The two parts are to be separately estimated on the available data. In order to study glucose-insulin homeostasis as a single dynamical system, a unified model would be desirable. To this end, the simple coupling of the original two parts of the minimal model is not appropriate, since it can be shown that, for commonly observed combinations of parameter values, the coupled model would not admit an equilibrium and the concentration of active insulin in the “distant” compartment would be predicted to increase without bounds. For comparison, a simple delay-differential model is introduced, is demonstrated to be globally asymptotically stable around a unique equilibrium point corresponding to the pre-bolus conditions, and is shown to have positive and bounded solutions for all times. The results of fitting the delay-differential model to experimental data from ten healthy volunteers are also shown. It is concluded that a global unified model is both theoretically desirable and practically usable, and that any such model ought to undergo formal analysis to establish its appropriateness and to exclude conflicts with accepted physiological notions. Received: 22 June 1998 / Revised version: 24 February 1999     

Travelling of proteins through membranes: translocation into chloroplasts

 Most proteins involved in plastid biogenesis are encoded by the nuclear genome. They are synthesised in the cytosol and have to be transported toward and subsequently translocated into the organelle. This targeting and import process is initiated by a specific chloroplast-targeting signal. The targeting signal of the preprotein is recognised and modified by cytosolic proteins which function in transport toward the chloroplast and in maintaining the import-competent state of the preprotein. The precursor is transferred onto a multi-component complex in the outer envelope of the chloroplasts, which is formed by receptor proteins and the translocation channel. Some proteins, not containing transit sequences, are directly sorted into the outer membrane whereas the majority, containing transit sequences, will be translocated into the stroma. This involves the joint action of a protein complex in the outer envelope, one complex in the inner envelope, and soluble proteins in the intermembrane space and the stroma. The origin of this translocation complex following the endosymbiotic events is an unsolved question. Recent identification of homologous proteins to some members of this machinery in the cyanobacterium Synechocystis PCC6803 gives an initial insight into the origin of the translocation complex. Received: 27 December 1999 / Accepted: 29 March 2000     

Maternal factors and the evolution of developmental mode: Evolution of oogenesis in Heliocidaris erythrogramma

 Evolutionary change in developmental mode in sea urchins is closely tied to an increase in maternal provisioning. We examined the oogenic modifications involved in production of a large egg by comparison of oogenesis in congeneric sea urchins with markedly different sized oocytes and divergent modes of development. Heliocidaris tuberculata has small eggs (95 μm diameter) and the ancestral mode of development through feeding larvae, whereas H. erythrogramma has large eggs (430 μm diameter) and highly modified non-feeding lecithotrophic larvae. Production of a large egg in H. erythrogramma involved both conserved and divergent mechanisms. The pattern and level of vitellogenin gene expression is similar in the two species. Vitellogenin processing is also similar with the gonads of both species incorporating yolk protein from coelomic and hemal stores into nutritive cells with subsequent transfer of this protein into yolk granules in the developing vitellogenic oocyte. Immunocytology of the eggs of both Heliocidaris species indicates they incorporate similar levels of yolk protein. However, H. erythrogramma has evolved a highly divergent second phase of oogenesis characterised by massive deposition of non-vitellogenic material including additional maternal protein and lipid. Maternal provisioning in H. erythrogramma exhibits recapitulation of the ancestral vitellogenic program followed by a novel oogenic phase with hypertrophy of the lipogenic program being a major contributor to the increase in egg size. Received: 12 August 1998 / Accepted: 25 November 1998     

Selfing facilitates reproductive isolation among three sympatric species of Pitcairnia (Bromeliaceae)

 The reproductive biology of three sympatric species Pitcairnia flammea, P. corcovadensis and P. albiflos (Bromeliaceae) was studied on Corcovado Mountain in the city of Rio de Janeiro, Brazil. Controlled pollination experiments were also conducted using plants transplanted to a greenhouse. The three species are self-compatible and interspecifically cross compatible. Pitcairnia corcovadensis was principally an autonomous self-pollinator, having scarce pollinator activity, anthers and stigmas at the same level, and absence of nectar. In P. flammea, many flowers opened per day, the stigma and anther were close to each other, and its nectar was regularly consumed by hummingbirds; all factors that promote geitonogamy in this species. Although fully self-compatible, P. albiflos always opened a few flowers per days showing an adaptation to cross-pollination. Observations during two flowering seasons showed that despite different times for peak flowering, blooming of these three species overlapped in April. They grow in mixed clumps that may facilitate promiscuous pollination between them but no intermediate forms were observed under natural conditions. The absence of temporal isolation, geographic isolation and isolation via post-pollination reproduction suggests that evolution toward selfing was important to avoid hybridization between these sympatric species. Received May 10, 2001 Accepted February 25, 2002     

The origins of postmating reproductive isolation: testing hypotheses in the grasshopper <Emphasis Type="Italic">Chorthippus parallelus</Emphasis>

 Although there are several well-established hypotheses for the origins of postmating isolation during allopatric divergence, there have been very few attempts to determine their relative importance in nature. We have developed an approach based on knowledge of the differing evolutionary histories of populations within species that allows systematic comparison of the predictions of these hypotheses. In previous work, we have applied this methodology to mating signal variation and premating reproductive isolation between populations of the meadow grasshopper Chorthippus parallelus. Here we review the principles behind our approach and report a study measuring postmating isolation in the same set of populations. The populations have known and differing evolutionary histories and relationships resulting from the colonization of northern Europe following the last glaciation. We use a maximum-likelihood analysis to compare the observed pattern of postmating isolation with the predictions of the hypotheses that isolation primarily evolves either as a result of gradual accumulation of mutations in allopatry, or through processes associated with colonization, such as founder events. We also quantify the extent to which degree of postmating isolation can be predicted by genetic distance. Our results suggest that although there is only a weak correlation between genetic distance and postmating isolation, long periods of allopatry do lead to postmating isolation. In contrast to the pattern of premating isolation described in our previous study, colonization does not seem to be associated with increased postmating isolation. Received: January 24, 2002 / Accepted: July 26, 2002 Acknowledgments Numerous people helped with collecting and rearing grasshoppers. We are grateful to NERC for funding. Correspondence to:R.K. Butlin     

Plasticity of seed output in response to soil nutrients and density in Abutilon theophrasti: implications for maintenance of genetic variation

 Seed output is determined by two processes: resource acquisition and the allocation of resources to seeds. In order to clarify how the reaction norm of seed output is controlled by the phenotypic expression of its two components, we examined the genetic components of plasticity of seed dry mass, plant size, and reproductive allocation under different conditions of soil nutrient availability and conspecific competition among eight families of Abutilon theophrasti. Without competition, the reaction norm of seed mass of the families crossed between the lowest and other nutrient levels, although neither of its components, plant size and reproductive allocation, showed such a response. The crossing reaction norm (i.e., reversal of relative fitnesses of different genotypes along the environmental gradient) of seed mass resulted from (1) a trade-off between plant size and reproductive allocation, and (2) changes in the relative magnitude of genetic variances in plant size and reproductive allocation with soil nutrient availability. While allocation was more important in determining seed mass under limiting nutrient conditions, plant size became more important under high-nutrient conditions. There were no significant genetic variances in seed mass, plant size, and reproductive allocation in the competition treatment, except at the highest nutrient level. The results show that plant competition mitigated the effects of genetic differences in plant performance among the families. We discuss the results in relation to maintenance of genetic variation within a population. Received: 16 August 1996 / Accepted 26 April 1997     

To treat or not to treat: the case of tuberculosis

. Incomplete treatment of patients with infectious tuberculosis (TB) may not only lead to relapse but also to the development of antibiotic resistant TB – one of the most serious health problems facing society today. In this article, we formulate one-strain and two-strain TB models to determine possible mechanisms that may allow for the survival and spread of naturally resistant strains of TB as well as antibiotic-generated resistant strains of TB. Analysis of our models shows that non-antibiotic co-existence is possible but rare for naturally resistant strains while co-existence is almost the rule for strains that result from the lack of compliance with antibiotic treatment by TB infected individuals. Received 22 May 1995; received in revised form 28 February 1996     

Evolutionary dynamics of predator-prey systems: an ecological perspective

 Evolution takes place in an ecological setting that typically involves interactions with other organisms. To describe such evolution, a structure is needed which incorporates the simultaneous evolution of interacting species. Here a formal framework for this purpose is suggested, extending from the microscopic interactions between individuals – the immediate cause of natural selection, through the mesoscopic population dynamics responsible for driving the replacement of one mutant phenotype by another, to the macroscopic process of phenotypic evolution arising from many such substitutions. The process of coevolution that results from this is illustrated in the context of predator–prey systems. With no more than qualitative information about the evolutionary dynamics, some basic properties of predator–prey coevolution become evident. More detailed understanding requires specification of an evolutionary dynamic; two models for this purpose are outlined, one from our own research on a stochastic process of mutation and selection and the other from quantitative genetics. Much of the interest in coevolution has been to characterize the properties of fixed points at which there is no further phenotypic evolution. Stability analysis of the fixed points of evolutionary dynamical systems is reviewed and leads to conclusions about the asymptotic states of evolution rather different from those of game-theoretic methods. These differences become especially important when evolution involves more than one species. Received 10 November 1993; received in revised form 25 July 1994     

Life cycle of a giant carnivorous caddisfly, <Emphasis Type="Italic">Himalopsyche japonica</Emphasis> (Morton) (Trichoptera: Rhyacophilidae), in the mountain streams of Nagano,Central Japan

 The life cycle of a giant carnivorous caddisfly, Himalopsyche japonica (Morton), was studied in two mountain streams in Nagano Prefecture, Central Japan. Field surveys and rearing experiments in the laboratory were conducted from October 1997 to September 2001. The life cycle of H. japonica was estimated to be a complex univoltine cycle that partly includes bivoltine populations. The adults had a long flight period, from April to September, with three distinct peaks of emergence. First to third instar larvae were collected from June to February, and the last (fifth) instar larvae and pupae appeared throughout the year. In autumn, the larvae belonging to all instars were found, and younger ones overwintered in the fourth instar stage and others in the fifth instar stage. On the other hand, fifth instar larvae and pupae ceased developing in autumn even though the water temperature was higher than the developmental zero temperature. The overwintered pupae emerged as adults in April, and the overwintered fifth instar larvae pupated in May and emerged in June. The larvae which overwintered in the fourth instar stage probably emerged after June. Received: March 19, 2002 / Accepted: January 10, 2003 Present address: United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan Tel. +81-265-77-1401; Fax +81-265-74-7496 e-mail: himalo@f8.dion.ne.jp Acknowledgments The author thanks Prof. T. Yoshida, Prof. H. Nakamura, and Associate professor K. Soma, Shinshu University; Mr. T. Nozaki, Kanagawa Environmental Research Center; and Mr. N. Kubota, Environmental Assessment Center in Matsumoto laboratory for their advice and help in accomplishing this research. The author is also grateful to Prof. K. Tanida, Osaka Prefecture University; Dr. T. Ito, Hokkaido Fish Hatchery; Mr. K. Okazaki, Kutchan City Museum; and Mrs. Y. Isobe, Nara Women's University, for suggesting references. Miss. T. Ishiyama, Mr. H. Kojima, Mr. M. Yagyu, and the students of the Forest Animals Laboratory in Shinshu University kindly provided field samples. Correspondence to:T. Tsuruishi