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Göran Arnqvist

Publications and source records attributed to Göran Arnqvist.

14 recordsLinked to original sources
PubMed2006

Sex-role reversed nuptial feeding reduces male kleptoparasitism of females in Zeus bugs (Heteroptera; Veliidae).

Males of a variety of taxa occasionally steal food secured by their mates. In some spiders and insects, males rely entirely on this form of intraspecific kleptoparasitism for their subsistence. However, this male strategy may be costly for females and a variety of different female counteradaptations have been proposed. In Zeus bugs (Phoreticovelia spp.), males ride on the back of their mates for extended periods and females produce a gland secretion that males feed on. By experimentally occluding the dorsal glands in females and varying food availability, we show that nuptial feeding by females reduces the extent to which the males kleptoparasitize their mates. We suggest that females have, at least in part, evolved this unique form of nuptial feeding as a counteradaptation to reduce the rate of kleptoparasitism by males.

Adaptation, Biological↗
PubMed2006

Intergenomic epistasis for fitness: within-population interactions between cytoplasmic and nuclear genes in Drosophila melanogaster.

The symbiotic relationship between the mitochondrial and nuclear genomes coordinates metabolic energy production and is fundamental to life among eukaryotes. Consequently, there is potential for strong selection to shape interactions between these two genomes. Substantial research attention has focused on the possibility that within-population sequence polymorphism in mitochondrial DNA (mtDNA) is maintained by mitonuclear fitness interactions. Early theory predicted that selection will often eliminate mitochondrial polymorphisms. However, recent models demonstrate that intergenomic interactions can promote the maintenance of polymorphism, especially if the nuclear genes involved are linked to the X chromosome. Most empirical studies to date that have assessed cytonuclear fitness interactions have studied variation across populations and it is still unclear how general and strong such interactions are within populations. We experimentally tested for cytonuclear interactions within a laboratory population of Drosophila melanogaster using 25 randomly sampled cytoplasmic genomes, expressed in three different haploid nuclear genetic backgrounds, while eliminating confounding effects of intracellular bacteria (e.g., Wolbachia). We found sizable cytonuclear fitness interactions within this population and present limited evidence suggesting that these effects were sex specific. Moreover, the relative fitness of cytonuclear genotypes was environment specific. Sequencing of mtDNA (2752 bp) revealed polymorphism within the population, suggesting that the observed cytoplasmic genetic effects may be mitochondrial in origin.

Animals↗
PubMed2006

Ageing and the evolution of female resistance to remating in seed beetles.

Female remating behaviour is a key mating system parameter that is predicted to evolve according to the net effect of remating on female fitness. In many taxa, females commonly resist male remating attempts because of the costs of mating. Here, we use replicated populations of the seed beetle Acanthoscelides obtectus selected for either early or late life reproduction and show that 'Early' and 'Late' females evolved different age-specific rates of remating. Early females were more likely to remate with control males as they aged, while Late females were more resistant to remating later in life. Thus, female remating rate decreases with age when direct selection on late-life fitness is operating and increases when such selection is relaxed. Our findings not only demonstrate that female resistance to remating can evolve rapidly, but also that such evolution is in accordance with the genetic interests of females.

Aging↗
PubMed2006

Sensory exploitation and sexual conflict.

Much of the literature on male-female coevolution concerns the processes by which male traits and female preferences for these can coevolve and be maintained by selection. There has been less explicit focus on the origin of male traits and female preferences. Here, I argue that it is important to distinguish origin from subsequent coevolution and that insights into the origin can help us appreciate the relative roles of various coevolutionary processes for the evolution of diversity in sexual dimorphism. I delineate four distinct scenarios for the origin of male traits and female preferences that build on past contributions, two of which are based on pre-existing variation in quality indicators among males and two on exploitation of pre-existing sensory biases among females. Recent empirical research, and theoretical models, suggest that origin by sensory exploitation has been widespread. I argue that this points to a key, but perhaps transient, role for sexually antagonistic coevolution (SAC) in the subsequent evolutionary elaboration of sexual traits, because (i) sensory exploitation is often likely to be initially costly for individuals of the exploited sex and (ii) the subsequent evolution of resistance to sensory exploitation should often be associated with costs due to selective constraints. A review of a few case studies is used to illustrate these points. Empirical data directly relevant to the costs of being sensory exploited and the costs of evolving resistance is largely lacking, and I stress that such data would help determining the general importance of sexual conflict and SAC for the evolution of sexual dimorphism.

Animals↗
PubMed2006

No apparent indirect genetic benefits to female red flour beetles preferring males with intense copulatory courtship.

Whether females gain indirect genetic benefits through mate choice is a controversial issue since this requires additive genetic variance in the preferred male traits. Condition dependence could maintain the necessary genetic variance by linking the expression of male traits to the supposedly large number of genes affecting condition. Copulating males of the red flour beetle Tribolium castaneum rub their legs along the female elytra. Females favor males with vigorous rubbing through cryptic female choice. We measured the repeatability and heritability of this behavior and assessed its potential use as indicator of viability and condition. We found genetic variance in larval to adult survival and in the rate of leg rubbing in males. However, the rate of leg rubbing was not related to offspring survival or condition dependent. The genetic variance in leg rubbing was mostly non-additive with very low narrow sense heritability. Therefore, we failed to document any indirect genetic benefits to choosy females through viability of their offspring or attractiveness of their sons.

Animals↗
PubMed2006

Within-population variation in cytoplasmic genes affects female life span and aging in Drosophila melanogaster.

It has been suggested that mitochondrial DNA (mtDNA) may play an important role in aging. Yet, few empirical studies have tested this hypothesis, partly because the degree of sequence polymorphism in mtDNA is assumed to be low. However, low sequence variation may not necessarily translate into low phenotypic variation. Here, we report an experiment that tests whether there is within-population variation in cytoplasmic genes for female longevity and senescence. To achieve this, we randomly selected 25 "mitochondrial founders" from a single, panmictic population of Drosophila melanogaster and used these founders to generate distinct "mt" lines in which we controlled for the nuclear background by successive backcrossing. Potential confounding effects of cytoplasmically transmitted bacteria were eliminated by tetracycline treatment. The mt lines were then assayed for differences in longevity, Gompertz intercept (frailty), and demographic rate of change in mortality with age (rate-of-senescence) in females. We found significant cytoplasmic effects on all three variables. This provides evidence that genetic variation in cytoplasmic genes, presumably mtDNA, contributes to variation in female mortality and aging.

Aging↗
PubMed2005

Adaptive male effects on female ageing in seed beetles.

Selection can favour the evolution of a high reproductive rate early in life even when this results in a subsequent increase in the rate of mortality, because selection is relatively weak late in life. However, the optimal reproductive schedule of a female may be suboptimal to any one of her mates, and males may thus be selected to modulate female reproductive rate. Owing to such sexual conflict, coevolution between males and females may contribute to the evolution of senescence. By using replicated beetle populations selected for reproduction at an early or late age, we show that males evolve to affect senescence in females in a manner consistent with the genetic interests of males. 'Late' males evolved to decelerate senescence and increase the lifespan of control females, relative to 'early' males. Our findings demonstrate that adaptive evolution in one sex may involve its effects on senescence in the other, showing that the evolution of optimal life histories in one sex may be either facilitated or constrained by genes expressed in the other.

Adaptation, Biological↗
PubMed2005

The evolution of infidelity in socially monogamous passerines: the strength of direct and indirect selection on extrapair copulation behavior in females.

Many studies have been aimed at understanding the maintenance of female infidelity in socially monogamous birds. Because engaging in extrapair copulations (EPCs) is believed to be costly for females, it has been argued that EPC behavior must bring indirect benefits to females by elevating offspring fitness. We use empirical data from the literature to assess the relative strength of indirect and direct selection on female EPC behavior, using quantitative genetic approximations of selection. This analysis confirmed that there is generally negative direct selection on EPC behavior caused by depressed paternal investment by social males. In contrast, there was no significant positive indirect selection on EPC behavior in females. A comparison between the two types of selection suggests that the force of direct negative selection is generally much stronger than that of indirect positive selection. Indirect selection is thus unlikely to maintain EPC behavior in the face of direct selection against it. We suggest that EPCs may instead be the result of antagonistic selection on loci influencing the outcome of male-female encounters and that EPC behavior per se may not be adaptive for females but may reflect sexual conflict due to strong selection in males to achieve extrapair copulations.

Animals↗
PubMed2004

Sexual conflict and sexual selection: lost in the chase.

The emergent field of evolutionary biology that studies disparities between the evolutionary interests of alleles expressed in the two sexes, or sexual conflict, promises to offer novel insights into male-female coevolution and speciation. Our theoretical understanding of basic concepts is, however, still incomplete. In a recent perspective paper, Pizzari and Snook provided a framework for understanding sexually antagonistic coevolution and for distinguishing this process from other models of male-female coevolution and suggested an experimental protocol to test for sexually antagonistic coevolution. Here, I show that the framework is flawed, primarily because it is built upon the mistaken assumption that male and female fitness can evolve independently. Further, while the empirical strategy advocated has indeed offered important insights in the past, it does not allow unambiguous discrimination between competing hypotheses.

Animals↗
PubMed2003

Costly traumatic insemination and a female counter-adaptation in bed bugs.

Male bed bugs pierce females through the body wall and inseminate directly into the body cavity. It has previously been shown that such traumatic insemination carries costs for females, and sexual conflict regarding the mode of insemination should thus propel male-female coevolution. Since males accumulate sexually antagonistic adaptations, females should evolve counter-adaptations that efficiently abate the costs to females of sexual interactions. Yet, unambiguous experimental evidence for female counter-adaptations is lacking. In bed bugs, the spermalege (a highly modified region of the abdomen where the male usually pierces the female) may represent a female counter-adaptation. We assess the female costs of traumatic insemination by varying the rate of insemination on the one hand, and the rate and mode of piercing trauma to females on the other. Our results show that female mating costs are not extreme-elevated mating rate shortened female lifespan but had no significant effect on lifetime egg production. More importantly, additional abdominal piercing in the spermalege had no effect on females whereas even a very low rate of such piercing outside the spermalege reduced female lifetime egg production by 50%. Thus, females are well counter-adapted to the intrusive mode of insemination exhibited by male bed bugs and the costs of elevated mating are comparable with those in other insects, as predicted by theory. We therefore demonstrate that the spermalege efficiently reduces the direct costs of piercing trauma to females, and hence provide experimental evidence for a female counter-adaptation to a sexually antagonistic male trait.

Adaptation, Biological↗
PubMed2002

Antagonistic coevolution between the sexes in a group of insects.

In coevolutionary 'arms races' between the sexes, the outcome of antagonistic interactions may remain at an evolutionary standstill. The advantage gained by one sex, with any evolutionary exaggeration of arms, is expected to be matched by analogous counteradaptations in the other sex. This fundamental coevolutionary process may thus be hidden from the evolutionist's eye, and no natural examples are known. We have studied the effects of male and female armament (clasping and anti-clasping morphologies) on the outcome of antagonistic mating interactions in 15 species of water strider, using a combination of experimental and phylogenetic comparative methods. Here we present, by assessing the independent effects of both species-specific level of arms escalation and small imbalances in the amounts of arms between the sexes within species, the consequences of a sexual arms race. Evolutionary change in the balance of armament between males and females, but not in the species-specific level of escalation, has resulted in evolutionary change in the outcome of sexually antagonistic interactions such as mating rate.

Animals↗
PubMed2002

Sexually antagonistic coevolution in a mating system: combining experimental and comparative approaches to address evolutionary processes.

We combined experimental and comparative techniques to study the evolution of mating behaviors within in a clade of 15 water striders (Gerris spp.). Superfluous multiple mating is costly to females in this group, and consequently there is overt conflict between the sexes over mating. Two alternative hypotheses that could generate interspecific variation in mating behaviors are tested: interspecific variation in optimal female mating rate versus sexually antagonistic coevolution of persistence and resistance traits. These potentially coevolving traits include male grasping and female antigrasping structures that further the interests of one sex over the other during premating struggles. Both processes are known to play a role in observed behavioral variation within species. We used two large sets of experiments to quantify behavioral differences among species, as well as their response to an environmentally (sex-ratio) induced change in optimal female mating rate. Our analysis revealed a large degree of continuous interspecific variation in all 20 quantified behavioral variables. Nevertheless, species shared the same set of behaviors, and each responded in a qualitatively similar fashion to sex-ratio alterations. A remarkably large proportion (> 50%) of all interspecific variation in the magnitude of behaviors, including their response to sex ratio, could be captured by a single multivariate axis. These data suggest tight coevolution of behaviors within a shared mating system. The pattern of correlated evolution was best accounted for by antagonistic coevolution in the relative abilities of each sex to control the outcome of premating struggles. In species where males have a relative advantage, mating activity is high, and the opposite is found in species where females have gained a relative advantage. Our analyses also suggested that evolution has been unconstrained by history, with no consistent evolutionary tendency toward or away from male or female relative advantage.

Analysis of Variance↗
PubMed2002

Correlated evolution of male and female morphologles in water striders.

Sexually antagonistic coevolution may be an important force in the evolution of sexual dimorphism. We undertake a comparative study of correlated evolution of male and female morphologies in a clade of 15 water strider species in the genus Gerris (Heteroptera: Gerridae). Earlier studies have shown that superfluous matings impose costs on females, including increased energetic expenditure and predation risk, and females therefore resist males with premating struggles. Males of some species possess grasping structures and females of some species exhibit distinct antigrasping structures, which are used to further the interests of each sex during these premating struggles. We use this understanding, combined with coevolutionary theory, to derive a series of a priori predictions concerning both the types of traits in the two sexes that are expected to coevolve and the coevolutionary dynamics of these traits expected under sexually antagonistic coevolution. We then assess the actual pattern of correlated evolution in this clade with new morphometric methods combined with standard comparative techniques. The results were in agreement with the a priori predictions. The level of armament (different abdominal structures in the two sexes) was closely correlated between the sexes across species. Males are well adapted to grasping females in species in which females are well adapted to thwart harassing males and vice versa. Furthermore, our comparative analyses supports the prediction that correlated evolution of armament in the two sexes should be both rapid and bidirectional.

Animals↗