Variation in colour markings of German wasps Vespula germanica (F.) and common wasps Vespula vulgaris (L.) (Hymenoptera: Vespidae) in New Zealand

Abstract

German wasps (Vespula germanica F.) and common wasps (V. vulgaris L.) both show variations in colour markings in New Zealand. Overlap in the ranges of markings of the head and thorax is limited enough for ready distinction of queens and workers of the two species. Abdominal markings overlap considerably between the species. Colour markings of males were too similar to identify the species, which were completely separated by the shape of their genitalia. The frequency of occurrence of “intermediate” markings in V. germanica populations did not increase in areas where the two species overlap. This suggests there is little or no genetic exchange between the two species.     

Opportunistic predation and offspring sex ratios of cicada-killer wasps (Sphecius speciosus Drury)

Abstract.  1. The way in which hunting of prey affects the sex ratio of the predator's offspring is not well understood. Female cicada-killer wasps are convenient for study because they specialise in capturing cicadas to provision their offspring. Cicada prey are nearly twice as heavy as the wasps that carry them, hence some degree of prey selectivity by the wasps is to be expected. It has been suggested that wasps bias their offspring towards females by foraging selectively for female prey, whereas there is some evidence that sex ratios are actually male-biased. This study was designed to establish the connection between foraging and offspring sex ratio.
2. Three, non-exclusive, hypotheses of selective predation were tested. The frequency of predation on different classes of prey in conjunction with their availability was estimated by intercepting the wasps on their way to their nests and by sampling cicadas in the environment. The hypothesis of selective predation was not supported; predation appears to be opportunistic and non-selective. Cicada prey weight was not a simple linear function of wasp weight, although the smallest wasps were constrained to carry small prey.
3. Wasp offspring (larvae) were excavated from subterranean nests and found to be male-biased (3 : 1 or 4 : 1) in 2 years. The observed ratios are close to expectation from Fisher's equal-investment model, taking account of sexual size dimorphism, and are evidently unrelated to the sex of the prey. A simple binomial probability rule of sex allocation provides a behavioural mechanism for producing the observed sex ratio of offspring.     

Larval food source promotes cyclic seasonal variation in polyandry in the moth Lobesia botrana

In Mediterranean vineyards the European grapevine moth, Lobesiabotrana, usually completes three non-overlapping larval generationsper year. Larvae feed on inflorescences and unripe or ripe grapes.Previous work has shown that the larval food source has a hugeeffect on adult size and fitness. We investigated if larvalfood also affects the propensity of females to mate polyandrously.Levels of polyandry were monitored with baited traps in a vineyardfor two years and then compared with data from laboratory trialsusing vine-reared individuals. In the field, polyandry levelsfollowed a cyclic annual pattern associated with the larvalfood source. Large females that fed on ripe grapes exhibitedsignificantly higher levels of polyandry than smaller femalesthat fed on inflorescences. Females that fed on unripe grapesshowed intermediate levels of remating. Polyandry also tendedto increase later in each flight. Laboratory trials confirmeda direct effect of larval feeding on levels of polyandry. Overall,these results showed that the seasonal variation in polyandryexhibited by L. botrana in the field occurs, at least in part,because of food-derived changes regulating female size. Resultsalso suggested that larval feeding could shape sexual size dimorphismand polyandry levels. Larval nutrition should therefore be consideredas an important ecological factor by those studying the evolutionarysignificance of polyandry and sperm competition in the Lepidoptera.     

Birth sex ratio and social rank: consistency and variability within and between primate groups

Variations in birth sex ratios in primates are notoriously inconsistentand have been repeatedly suggested to be mainly owing to stochasticprocesses. An examination of temporal consistency within primatepopulations revealed that the effect of dominance rank on birthsex ratio tends to remains stable over time. Furthermore, ameta-analysis of published data on sex ratio variations in primatesshows that although no overall effect was detectable, the relationbetween birth sex ratio and dominance rank was affected by levelof resource availability and degree of sexual dimorphism. Theseresults suggest that purely stochastic processes are unlikelyto explain observed variations in primate birth sex ratios,and may explain why adaptive sex ratio variations in primateshave been so difficult to demonstrate.     

Detecting selection on morphological traits in social insect castes: the case of the social wasp Vespula maculifrons

Highly social insects dominate terrestrial ecosystems because society members belong to discrete castes that undertake distinct tasks. The distinct functional roles of members of different castes may lead to divergent selective regimes, which may ultimately lead to morphological specialization and differentiation of the castes. This study used morphological and genetic analyses to identify traits that experienced caste‐specific selection in the social wasp Vespula maculifrons (Buysson, 1905). Traits putatively under selection were identified based on their degree of caste dimorphism, levels of variability, strength of correlations with other traits, and patterns of allometric scaling. Analyses of trait characteristics suggested that queen thorax length, thorax width, and possibly mass, have experienced queen‐specific selection. Additionally, trait dimorphism and intercaste phenotypic correlation values were negatively correlated, as expected if some morphological traits were subject to selection, leading to alternate phenotypic optima in the two castes. Overall, our analyses demonstrate how techniques used to identify selection between dimorphic groups can be applied to social species with distinct castes. In addition, our analyses suggest the operation of selection may be stronger in reproductive than in non‐reproductive castes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 93–102.     

Understanding sex differences in the cost of terrestrial locomotion

Little is known regarding the physiological consequences of the behavioural and morphological differences that result from sexual selection in birds. Male and female Svalbard rock ptarmigans (Lagopus muta hyperborea) exhibit distinctive behavioural differences during the breeding season. In particular, males continuously compete for and defend territories in order to breed successfully, placing large demands on their locomotor system. Here, we demonstrate that male birds have improved locomotor performance compared with females, showing both a lower cost of locomotion (CoL) and a higher top speed. We propose that the observed sex differences in locomotor capability may be due to sexual selection for improved male performance. While the mechanisms underlying these energetic differences are unclear, future studies should be wary when pooling male and female data.     

Sex chromosomes and sex determination pathway dynamics in plant and animal models

In this review, we discuss and compare data obtained from animal and plant models, focusing our attention on the mechanisms that affect sex linkage and changes in sex‐determining pathways. Patterns in data across taxa suggest that sex bias and the dynamics that occurs within hybrid zones can play an important role in these processes that enable the spread of some otherwise handicapped genotypes. We discuss the data obtained from several main plant model species in the light of the patterns demonstrated in animal models. In several plant models, we discuss possible differences in the age of their sex‐determining pathways and the age of their current sex chromosomes. We also address an open question: how can an X/A ratio based sex‐determining system evolve from a sex‐determining system based on two genes on the Y chromosome that control two separate sex‐determining pathways (for the control of gynoecium suppression and anther promotion)? Taking inspiration from the well described mechanisms involved in sex determination dynamics in animals, we suggest a hypothetical stepwise scenario of change of the plant sex‐determining system based on two separate sex‐determining pathways (for the control of gynoecium suppression and anther promotion) into the other sex‐determining systems. We suppose that an intermediate step occurs before shift to X/A based sex determination. At that phase, sex determination in plants is still based on an active Y chromosome, although there exists already a connected control of both sex‐determining pathways. We suggest that this connection is enabled by the existence of the genes that control sexual dimorphism in the vegetative state of plant development, and that, in some circumstances, these genes can become sex‐determining genes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 737–752.     

Functional and ecological relevance of intraspecific variation in body size and shape in the lizard Podarcis melisellensis (Lacertidae)

Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 251–264.     

The spread of the social wasp,Vespula germanica,in Australia

Abstract

Between 1977 and 1989 the social wasp Vespula germanicacolonised mainland Australia and became established in New South Wales, Victoria, and South Australia. Accidental transport between towns is the main mechanism of spread. In many towns wasp nests have not been detected until they became widespread; therefore, eradication is difficult Successful eradication has, however, been achieved in many other towns.

Nesting places vary considerably among localities but relatively little among years at anyone locality. Peak wasp abundance occurs between January and April. Control of V. germanica nests costs Australia an estimated $600,000 (Aust. $) annually.     

Worker interests and male production in Polistes gallicus, a Mediterranean social wasp

The resolution of social conflict in colonies may accord with the interests of the most numerous party. In social insect colonies with single once-mated queens, workers are more closely related to the workers' sons than they are to the queens' sons. Therefore, they should prefer workers to produce males, against the queen's interests. Workers are capable of producing males as they arise from unfertilized eggs. We found Polistes gallicus to have colonies of single, once-mated queens, as determined by microsatellite genotyping of the workers, so worker interests predict worker male production. In colonies lacking queens, workers produced the males, but not in colonies with original queens. Thus worker interests were expressed only when the queen was gone. The high fraction of missing queens and early end to the colony cycle relative to climate so early in the season is surprising and may indicate a forceful elimination of the queen.     

Carbohydrate bait preferences of wasps (Vespula vulgaris and V. germanica) (Hymenoptera: Vespidae) in New Zealand

Abstract

Carbohydrates are both a source of food and a potential bait for control of common and German wasps. Carbohydrate preferences of wasps were determined in a series of paired trials by counting the number of wasps caught in traps baited with carbohydrate‐based baits versus a standard protein‐based bait. Factors influencing wasp attraction to carbohydrate‐based baits included bait type, season, weather, and location. A 30% sucrose solution was more attractive than honey, jams, gels, or dry (solid) sugars. The sucrose solution was more attractive in spring and autumn than in summer, probably because rainfall washed away natural carbohydrate supplies. There was a significant relationship between rainfall in the previous week and the proportion of wasps caught in traps baited with sucrose solution versus sardine cat‐food. A higher proportion of German wasps than common wasps was caught in sucrose‐baited traps. This may have been related to seasonal differences in abundance and/or behavioural differences between the two species. In some locations, more wasps were caught in traps baited with sucrose solution than in those baited with sardine cat‐food. The proportion of wasps caught in sucrose‐baited traps was higher in locations without beech scale honeydew than with beech scale honey‐dew. Proportionally more non‐target species (mainly honey bees) and fewer wasps were caught in traps baited with sucrose solution than in those baited with sardine cat‐food. All five bee repellents tested also repelled wasps. These results indicate the importance of determining the bait preferences of wasps (carbohydrate or protein) and the presence of non‐target species before attempting a poison‐baiting operation. They also emphasise the need for a wasp‐specific carbohydrate‐based bait.     

Mate choice, operational sex ratio, and social promiscuity in a wild population of the long-snouted seahorse Hippocampus guttulatus

Mate competition and mate choice are not mutually exclusivebehaviors. Both behaviors may drive sexual selection in oneor both sexes of a population. One of several factors affectingwhich behavior is exhibited by which sex is the operationalsex ratio (OSR) in the study population. The present study combinesbehavioral observations in the field with controlled experimentsin aquaria to investigate social interactions and mate choicein both male and female long-snouted seahorses Hippocampus guttulatusin the context of the population OSR. Compared with the morereadily studied pipefishes, data on OSR and mate choice in seahorsesare scarce in the published literature. Our field data providenovel evidence of social promiscuity, size-assortative mating,and an OSR that varies from being unbiased early and midseasonto male biased at the end of the breeding season. Our mate choiceexperiments revealed intersexual differences in mate preferencewith males significantly preferring larger females to familiarones. Taken together, our field and experimental results suggestthat mate choice rather than intrasexual competition could drivesexual selection in seahorses.     

Distribution of social wasps (Hymenoptera: Vespidae) in New Zealand in 1987

Abstract

More than 50 000 social wasps (Hymenoptera: Vespidae) were collected between March and August 1987 from throughout New Zealand. The most widespread species is the German wasp (Vespula germanica). The common wasp (V. vulgaris) has colonised about half the country and appears to be still spreading. It tends to appear in urban areas first, presumably because it is transported there with people and/or their belongings. The Asian paper wasp (Polistes chinensis) and Australian paper wasp (P. humilis), are confined to the northern half of the North Island, but the former species is spreading south.     

The form of the supraorbital margin as a criterion in identification of sex from the skull: Investigations based on modern human skulls

Sexual dimorphism in the shape of the supraorbital margin was reported by Broca and various subsequent authors, but no consistently applied, precise definition has been established. In this study of modern human skulls, the value of our definition of the sex-related difference in this area in the identification of sex from the skull was investigated. It was found that this feature can be assessed reliably, is strongly related to sex, and is independent of the side. The accuracy of identification of sex using this method alone was found to be about 70%. Am J Phys Anthropol 108:91–96, 1999. © 1999 Wiley-Liss, Inc.     

Phylomitogenomics reveals mito-nuclear concordance in social wasps: The performance of mitochondrial markers and gene order for hymenopteran systematics

Mitochondrial (mtDNA) genes have served as widely utilised genetic loci for phylogenetic and phylogeographic studies of animals. However, the phylogenetic performance of many mtDNA genes has not been empirically evaluated across lineages within hymenopteran wasps. To address this question, we assembled and analysed mitogenomic data from social wasps, representing the four recognised tribes of Polistinae and all Epiponini genera. Additionally, we evaluated whether mtDNA gene order in Polistinae is congruent with its tribal classification. Using concatenation phylogenetic methods, we show phylogenetic congruence between mitogenomic and nuclear data. Statistically comparing the phylogenetic performance of individual mtDNA genes, we demonstrate that for social wasps the molecular markers COI, 16S, NAD5, and NAD2 perform best, while ATP6, COII, and 12S show the worst results. Finally, we verified that the tRNA cluster close to the noncoding region is a hotspot of genetic rearrangements in Vespidae and can be used as additional information for the systematics of this group. Together, these results indicate that mitogenomes contain robust phylogenetic signal to elucidate the evolutionary history of Vespidae. Moreover, our study identifies the best choice of mtDNA markers for systematic investigations of social wasps.     

韩国枝尺蛾亚科三种幼虫记述（鳞翅目：尺蛾科）

在韩国已记录527种尺蛾科成虫,本科的大多数幼虫是林业和农业害虫。本文详细记述了枝尺蛾亚科白厚尺蛾Pachyligia dolosa Butler、蜻蜓尺蛾Cystidia stratonice(Stoll)及角子尺蛾Planociampa antipala Prout幼虫的形态特征,并提供了形态特征图。标本存放在韩国江源大学校山林科学大学森林资源保护学科标本室。     

Perspective: female remating,operational sex ratio,and the arena of sexual selection in Drosophila species

Abstract.— As commonly observed among closely related species within a variety of taxa, Drosophila species differ considerably in whether they exhibit sexual dimorphism in coloration or morphology. Those Drosophila species in which male external sexual characters are minimal or absent tend, instead, to have exaggerated ejaculate traits such as sperm gigantism or seminal nutrient donations. Underlying explanations for the interspecific differences in the presence of external morphological sexual dimorphism versus exaggerated ejaculate traits are addressed here by examining the opportunity for sexual selection on males to occur before versus after mating in 21 species of Drosophila . Female remating frequency, an important component of the operational sex ratio, differs widely among Drosophila species and appears to dictate whether the arena of sexual selection is prior to, as opposed to after, copulation. Infrequent female mating results in fewer mating opportunities for males and thus stronger competition for receptive females that favors the evolution of male characters that maximize mating success. On the other hand, rapid female remating results in overlapping ejaculates in the female reproductive tract, such that ejaculate traits which enhance fertilization success are favored. The strong association between female remating frequency in a given species and the presence of sexually selected external versus internal male characters indicates that the relationship be examined in other taxa as well.     

Maternal control of offspring sex and male morphology in the Otitesella fig wasps

Models concerning the evolution of alternative mating tactics commonly assume that individuals determine their own strategies. Here we develop a computer-based ESS model that allows mothers, ovipositing in discrete patches, to choose both the sex and the male mating tactics (natal-patch mating or dispersing) of their offspring based only on how many other mothers have used the specific patch before them. Data for three species of nonpollinating fig wasps from the Otitesella genus agree quantitatively with the model's assumptions and predictions. This suggests that females respond to population densities at the level of individual figs. The alternative male tactics in the species we studied are probably a result of a conditional strategy exercised by the mother that laid them. In addition, as females were only allowed to lay one egg per patch, our results suggest a new mechanism that can skew population sex ratios towards a female bias.