Lifetime Mating Success Research Articles

Development time mediates the effect of larval diet on ageing and mating success of male antler flies in the wild.

High-quality developmental environments often improve individual performance into adulthood, but allocating toward early life traits, such as growth, development rate and reproduction, may lead to trade-offs with late-life performance. It is, therefore, uncertain how a rich developmental environment will affect the ageing process (senescence), particularly in wild insects. To investigate the effects of early life environmental quality on insect life-history traits, including senescence, we reared larval antler flies (Protopiophila litigata) on four diets of varying nutrient concentration, then recorded survival and mating success of adult males released in the wild. Declining diet quality was associated with slower development, but had no effect on other life-history traits once development time was accounted for. Fast-developing males were larger and lived longer, but experienced more rapid senescence in survival and lower average mating rate compared to slow developers. Ultimately, larval diet, development time and body size did not predict lifetime mating success. Thus, a rich environment led to a mixture of apparent benefits and costs, mediated by development time. Our results indicate that 'silver spoon' effects can be complex and that development time mediates the response of adult life-history traits to early life environmental quality.

Variance in lifetime reproductive success of male polar bears

Abstract Despite the important role that population density plays in ecological and evolutionary processes, studies of solitary species that occur at low densities remain scarce. In the context of mating systems, density is expected to influence the ability of males to find and monopolize mates, in turn, influencing variance in lifetime mating/reproductive success and the opportunity for selection. Herein, we investigate variance in male lifetime mating success (LMS), lifetime reproductive success (LRS), and the mating system of a sexually dimorphic carnivore that occurs at low densities, the polar bear (Ursus maritimus). Across 17 cohorts, born from 1975 to 1991, male LMS ranged from 0 to10 mates and LRS from 0 to 14 cubs; 40% of known-age males were not known to have reproduced. The opportunity for sexual selection (Is = 1.66, range = 0.60–4.99) and selection (I = 1.76, range: 0.65–4.89) were low compared to species with similar levels of sexual size dimorphism. Skew in male LRS was also low but significant for most cohorts indicating nonrandom reproductive success. Age-specific reproductive success was biased toward males from 11 to 17 years of age, with variation in fecundity (54%) but not longevity (10%) playing an important role in male reproduction. Our results support a growing body of evidence that suggests that male-biased size dimorphism and polygynous mating systems need not be associated with high variance in male mating and/or reproductive success.

Field estimates of fitness costs of the pace‐of‐life in an endangered damselfly

Theory predicts that within-population differences in the pace-of-life can lead to cohort splitting and produce marked intraspecific variation in body size. Although many studies showed that body size is positively correlated with fitness, many argue that selection for the larger body is counterbalanced by opposing physiological and ecological selective mechanisms that favour smaller body. When a population split into cohorts with different paces of life (slow or fast cohort), one would expect to detect the fitness-size relationship among and within cohorts, that is, (a) slower-developing cohort has larger body size and higher fitness than faster-developing cohort, and (b) larger individuals within each cohort show higher fitness than smaller individuals. Here, we test these hypotheses in capture-mark-recapture field surveys that assess body size, lifespan, survival and lifetime mating success in two consecutive generations of a partially bivoltine aquatic insect, Coenagrion mercuriale, where the spring cohort is slower-developing than the autumn cohort. As expected, body size was larger in the slow-developing cohort, which is consistent with the temperature-size rule and also with the duration of development. Body size seasonal variation was greater in slow-developing cohort most likely because of the higher variation in age at maturity. Concordant with theory, survival probability, lifespan and lifetime mating success were higher in the slow-developing cohort. Moreover, individual body size was positively correlated with survival and mating success in both cohorts. Our study confirms the fitness costs of fast pace-of-life and the benefits of larger body size to adult fitness.

Reproductive habitat provisioning promotes survival and reproduction of the endangered endemic damselfly Calopteryx exul

Effective habitat management is predicted to have positive effects on populations and species of conservation concern. Although studies have shown that ecological processes such as colonization can be promoted after habitat management, we still need more information on the survival and reproductive consequences at the individual level in order to reach positive conservation outcome. Here we assess the effects of reproductive habitat supplementation (host oviposition plant) on survival and mating success of an endangered endemic damselfly, Calopteryx exul, using capture-mark-recapture data. We first determined that the species prefer to oviposit on floating leaves of Potamogeton spp. Based on Cormack-Jolly-Seber modeling, we found that recapture and survival probabilities were positively affected by the number of the host oviposition patches of the host plant. Moreover, we showed a strong positive relationship between adult lifespan and lifetime mating success. Our results suggest that host-plant provisioning for reproduction not only increases the survival of individuals, but also increases the number of matings per lifetime. The procedure of supplying reproductive sites may enhance population growth of threatened odonates and other aquatic insects.

Pathways to fitness: carry‐over effects of late hatching and urbanisation on lifetime mating success

Life history theory and most empirical studies assume carry‐over effects of larval ­conditions to shape adult fitness through their impact on metamorphic traits (age and mass at metamorphosis). Yet, very few formal tests of this connection across metamorphosis exist, because this entails longitudinal studies from the egg stage and requires measuring fitness in (semi)natural conditions. In a longitudinal one‐year common‐garden rearing experiment consisting of an outdoor microcosm part for the larval stage and a large outdoor insectary part for the adult stage, we studied the effects of two factors related to time constraints in the larval stage (egg hatching period and urbanisation) on life history traits and lifetime mating success in the males of the damselfly Coenagrion puella. We reared early‐ and late‐hatched larvae from each of three rural and three urban populations from the egg stage throughout their adult life. Key findings were that both the hatching period and urbanisation shaped adult fitness, yet through different pathways. As expected, the more time‐constrained late‐hatched individuals accelerated their larval life history and this was associated with a lower lifetime mating success. A path analysis revealed this carry‐over effect was mediated by the changes in the two metamorphic traits (reduced age and lower mass at emergence). Notably, urban males had a 50% lower lifetime mating success, which was not mediated by age and mass at emergence, and possibly driven by their shorter lifespan. Our results point to long‐term carry‐over effects of the usually ignored natural variation in egg hatching dates, and further contribute to the limited evidence showing fitness costs of adjusting to an urban lifestyle.

Carry-Over Effects Across Metamorphosis of a Pesticide on Female Lifetime Fitness Strongly Depend on Egg Hatching Phenology: A Longitudinal Study under Seminatural Conditions

Current ecological risk assessment of pesticides fails to protect aquatic biodiversity. For the first time, we tested two potential reasons for this failure with regard to carry-over effects across metamorphosis: their dependence on hatching period, and the lack of studies quantifying adult fitness under seminatural conditions. Using the damselfly Coenagrion puella sampled from six populations, we designed an outdoor longitudinal one-year study starting from the egg stage. We exposed the aquatic larvae to the pesticide esfenvalerate (0.11 μg/L) during the initial microcosm part. Next, we monitored the lifetime fitness of the terrestrial adults in an insectary. Exposure to the pesticide negatively impacted not only larval traits, but also drastically reduced lifetime mating success of adult females. The impact of this postmetamorphic effect of the pesticide on the population level was three times more important than the effects in the larval stage. Importantly, this carry-over effect was only present in females that hatched early in the season, and was not mediated by metamorphic traits (age and mass at emergence). We provide proof-of-principle under seminatural conditions for two potential pitfalls that need to be considered when improving risk assessment: carry-over effects on adult fitness can (i) be much more important than effects during the larval stage and may not be captured by metamorphic traits, and (ii) be strongly modulated by egg hatching dates.

Long-Term Effect of Social Interactions on Behavioral Plasticity and Lifetime Mating Success

Behavioral traits often change over an individual's lifetime. Experience, physiological senescence, and age-dependent differences in optimal behavior can, in theory, all cause longitudinal behavioral changes. Yet most studies of behavioral plasticity and selection on behavior focus on short-term population-level responses to social factors such as conspecific density or sex ratio. Longer-term effects of social interactions on individual behavior have rarely been tested. Here we tested these effects by exposing male water striders (Hemiptera: Gerridae) to two different social conditions throughout their lifetime; we call these the nonsocial and social treatments. We then measured each male's lifetime mating success and individual behavioral plasticity by observing four different behaviors (exploring a novel environment, dispersal ability, sex-recognition sensitivity, and tendency to remount a resistant female after being dislodged) every 2 weeks. The social environment influenced individual variation in behavioral plasticity as well as population-level behavioral plasticity. Moreover, when we calculated linear selection gradients of individual behavioral traits and their plasticities on lifetime mating success, male remounting tendency and individual plasticity in exploration ability were likely to be the most important factors explaining variation in male lifetime mating success. In conclusion, the variation in social interactions throughout an individual's lifetime contributes to the individual variation in behavioral plasticity, which can significantly affect a male's lifetime fitness.

Similar Performance of Diploid and Haploid Males in an Ant Species without Inbreeding Avoidance

AbstractUnder haplodiploidy, a characteristic trait of all Hymenoptera, females develop from fertilised eggs, and males from unfertilised ones. Males are therefore typically haploid. Yet, inbreeding can lead to the production of diploid males that often fail in development, are sterile or are of lower fertility. In most Hymenoptera, inbreeding is avoided by dispersal flights of one or both sexes, leading to low diploid male loads. We investigated causes for the production of diploid males and their performance in a highly inbred social Hymenopteran species. In the ant Hypoponera opacior, inbreeding occurs between wingless sexuals, which mate within the mother nest, whereas winged sexuals outbreed during mating flights earlier in the season. Wingless males mate with queen pupae and guard their mating partners. We found that they mated randomly with respect to relatedness, indicating that males do not avoid mating with close kin. These frequent sib‐matings lead to the production of diploid males, which are able to sire sterile triploid offspring. We compared mating activity and lifespan of haploid and diploid wingless males. As sexual selection acts on the time of emergence and body size in this species, we also investigated these traits. Diploid males resembled haploid ones in all investigated traits. Hence, albeit diploid males cannot produce fertile offspring, they keep up with haploid males in their lifetime mating success. Moreover, by fathering viable triploid workers, they contribute to the colonies' work force. In conclusion, the lack of inbreeding avoidance led to frequent sib‐matings of wingless sexuals, which in turn resulted in the regular production of diploid males. However, in contrast to many other Hymenopteran species, diploid males exhibit normal sexual behaviour and sire viable, albeit sterile daughters.

Determinants of yearling male lekking effort and mating success in black grouse (Tetrao tetrix)

Age at first reproduction is a crucial component of individual fitness as it often determines the length of reproductive lifespan. The reproductive success of males generally varies more than that of females, but it is challenging to study because the genetic data or proper surrogate measure needed to investigate reproductive success are usually not available. In black grouse (Tetrao tetrix), a lekking species with strong male mating skew and female preference for older males, there is a strong relationship between observed matings and genetic paternity. Using this relationship, we studied the effects of morphological, and behavioral traits on probability of being territorial, mating success, and survival of yearling males. Heavier yearling males were more likely to be territorial, and higher population density increased the frequency of yearling male territoriality. Mating success was positively related to population density, lek attendance, and fighting rate, but not to morphological traits. Overwinter survival did not differ between territorial and nonterritorial yearling males. Our results show that yearling male black grouse in good condition can establish territories and have some limited mating success, especially during increasing population density. In black grouse, the direct fitness benefits gained as yearlings undoubtedly contribute substantially to individual fitness, as the high reproductive skew means few males successfully copulate during their lifetime. For other species, early reproduction may relate to individual lifetime mating success but depends both on the direction and magnitude of the relationship between age-specific mating success and survival, and, as our results also demonstrate, on extrinsic factors such as population density.

Studies on the bionomics of male Anopheles gambiae Giles and male Anopheles funestus Giles from southern Mozambique

Little is known about the fitness of wild male mosquitoes, the females of which are vectors of malaria. The problem of studying male biology has been exacerbated by difficulties associated with catching them. In southern Mozambique, however, almost the entire adult population of An. funestus and An. gambiae s.l. rest inside houses. They leave in a dusk exodus, which makes them easy to collect. In 8,348 exit collections from a village from 2003 to 2009, 567,195 male An. funestus and 34,591 male An. gambiae s.l. were collected. During the study, numbers of An. funestus increased but numbers of An. gambiae s.l. declined to the point of extinction. Overall numbers of An. gambiae s.l. were positively correlated with temperature, whilst the relationship between temperature and numbers of An. funestus changed from an initially positive one in the first three years of the study to a negative one in the last three years. Marked males were recaptured up to 300 m from the release site, with most recaptures occurring within 150 m. Estimated mean daily survival of male An. funestus was 0.86 (95% C.I. 0.869-0.850). For the years 2003-2007, estimated mean daily survival of male An gambiae s.l. was 0.660 (95% C.I. 0.682-0.638). For either species, there was no relationship between mean weekly temperature and estimated daily survival. These results imply that males of An. funestus live as long as females but have a relatively short flight range. They are discussed in the light of possible release strategies of sterile or genetically modified mosquitoes.

Sexual Selection of Male Song in Free-Living Sagebrush Crickets, Cyphoderris Strepitans

Measures of lifetime mating success in the sagebrush cricket, Cyphoderris strepitans, have revealed that most males succeed in obtaining only 1 mating, while many males fail to attract a female at all and a small minority mate 2 to 4 times. Relative to their abundance in the population, virgin males have a greater likelihood of obtaining a mating than non-virgin males have of securing additional matings, a phenomenon known as the virgin male mating advantage. Previous studies of sagebrush crickets have focused primarily on determining the proximate mechanisms responsible for the virgin male mating advantage, but little work has been done to identify the factors that influence male attractiveness in the first place. Because song plays a central role in mate attraction, it’s likely that variability in song parameters among males could account for the observed differences in mating success. Song is an energetically costly signal to produce and could serve as an honest indicator of male quality. Consequently, males that are able to invest greater amounts of energy into singing should be more attractive to females. In a previous field season, we recorded and analyzed the songs of virgin and non-virgin males and indeed found some evidence that females prefer males which invest greater energy into calling. In the present study, we synthesized artificial sagebrush cricket songs and directly measured female song preference with an arena playback experiment. Females were shown to consistently prefer song characteristics that would require greater energy expenditure by males. Males that sing with long pulse duration, long train duration, and at an intermediate dominant frequency were found to be highly attractive to females.

THE IMPORTANCE OF FEMALE CHOICE, MALE-MALE COMPETITION, AND SIGNAL TRANSMISSION AS CAUSES OF SELECTION ON MALE MATING SIGNALS

Selection on advertisement signals arises from interacting sources including female choice, male-male competition, and the communication channel (i.e., the signaling environment). To identify the contribution of individual sources of selection, we used previously quantified relationships between signal traits and each putative source to predict relationships between signal variation and fitness in Enchenopa binotata treehoppers (Hemiptera: Membracidae). We then measured phenotypic selection on signals and compared predicted and realized relationships between signal traits and mating success. We recorded male signals, then measured lifetime mating success at two population densities in a realistic environment in which sources of selection could interact. We identified which sources best predicted the relationship between signal variation and mating success using a multiple regression approach. All signal traits were under selection in at least one of the two breeding seasons measured, and in some cases selection was variable between years. Female preference was the strongest source of selection shaping male signals. The E. binotata species complex is a model of ecological speciation initiated by host shifts. Signal and preference divergence contribute to behavioral isolation within the complex, and the finding that female mate preferences drive signal evolution suggests that speciation in this group results from both ecological divergence and sexual selection.

Context-dependent acquisition of territories by male collared lizards: the role of mortality

We recorded the behavior of free-ranging collared lizards for 11 consecutive seasons to test the hypotheses that natural mortality of territorial males that were 2 years and older (2yp) allows first-year males to switch to territorial tactics and that such events increase opportunities for courtship. Because neighboring 2yp males sometimes expanded and sometimes did not expand into the areas made vacant by mortality, we also compared first-year male behavior under these 2 conditions. In response to 2yp male mortality, first-year males increased rates of travel, distant display, courtship frequency, and number of different females courted. Newly territorial first-year males did not significantly increase aggression with rival males. Travel and both courtship frequency and number of females courted were higher when neighboring males did not expand. First-year males that acquired territories during the breeding season had lower values for all variables than 2yp males, whereas first-year males acquiring territories after over-winter mortality courted less frequently than 2yp males. First-year males acquiring territories after over-winter mortality traveled at higher rates and were more aggressive with rivals than those that gained territories after mortality during the breeding season and established 2yp males. Our results indicate that mortality of territorial males both during the reproductive season and over winter prompts first-year males to adopt territorial tactics that promote increased opportunities to court females. Acquisition of territories during the first-year as a consequence of territory owner mortality potentially increases the lifetime mating success of these males markedly. Copyright 2010, Oxford University Press.

Cost of reproduction in male medflies: The primacy of sexual courting in extreme longevity reduction

In polygynous insect species, male reproductive success is directly related to lifetime mating success. However, the costs for males of sexual activities such as courting, signaling, and mating are largely unknown. We studied the cost of sexual activities in male Mediterranean fruit flies, Ceratitis capitata (Tephritidae), a polygynous lekking species, by keeping cohorts of individual male flies under relaxed crowding conditions in the laboratory. We used 5 cohorts among which individuals differed in their opportunities to interact with con-specifics and recorded life span, and in one treatment, mating rate. We found that males kept singly lived more than twice as long as males that interacted intensively with mature virgin females, while male–male interactions caused a smaller reduction in longevity. Because longevity of males that could court but not mate was not significantly different from those that could court and mate, we conclude that courting (not mating) was responsible for the observed longevity reduction. Moreover, we detected high variability in male mating success, when 5 virgin females were offered daily. In contrast to the cohort level, individual males that mated at a high rate lived relatively long, thus indicating heterogeneity in quality or sexual strategy among males.

When Love Comes Calling: Measuring Sexual Selection on Sagebrush Crickets

Male sagebrush crickets exhibit differential mating success based on their previous mating experience: virgin males have a higher probability of obtaining a mating than do non-virgin males. Measures of lifetime mating success in male sagebrush crickets have revealed that the median mating frequency is one, with many males failing to secure a mate at all and a small minority obtaining two to four mates. The purpose of this study was to investigate the acoustic and morphological characteristics that make male sagebrush crickets attractive to females. Male crickets were captured from Deadman’s Bar in Grand Teton National Park and their songs were recorded on subsequent evenings. Five song characteristics were measured including pulse duration, interpulse duration, dominant frequency, train duration, and intertrain duration. Multivariate selection analysis revealed significant linear and nonlinear selection on male song, with each of the five measured song characters contributing to male attractiveness. There was significant directional selection favoring longer pulse durations and shorter interpulse durations, which could be an honest indicator of male quality because these song characters likely impose high energetic costs. Significant stabilizing selection favored males with ~ 13.2 kHz calls and intermediate intertrain durations, which may be imposed by the auditory sensitivity of females.

Courtship strategies of male insects: when is learning advantageous?

Experiments indicating learning in the context of courtship in fruit flies challenge the prevailing views that male insects are either indiscriminate or rely on innate rules for courtship. We investigated the conditions favouring learning during courtship in insects by using a model that compared a learning strategy to two alternatives, indiscriminate courtship and innate selectivity. Our analyses indicated that, under the two conditions of high encounter rates with females and long courtship durations, indiscriminate courtship resulted in much lower lifetime mating success than either selectivity or learning. Learning had moderate advantages over selectivity when encounter rates with females were high, when a large proportion of females were sexually receptive, and when acceptance rates by sexually receptive females were high. We predict that species in which such conditions commonly occur are most likely to show learning in the context of male courtship.

Fluctuating asymmetry, body size, reproductive period and life time mating success of males of Cercion lindeni (Odonata: Coenagrionidae)

Mating success is linked to reproductive success in males, but parameters influencing it are poorly known. The relation- ships between lifetime mating success (LMS), fluctuating asymmetry (FA), body size (SIZE), reproductive period (RP) and emer- gence date (MD) of males of Cercion lindeni were investigated. Males were marked and photographed in their pre-reproductive period, and their matings monitored. RP was assumed to be the period between the MD and the last sighting of each individual. Three different FA measures and the size of each individual were determined. The results showed that the individuals not present at the pond during the reproductive period had a higher FA (but not for meristic characters) than those present. For those individuals actually involved in reproductive activity, LMS was only positively correlated with RP, which was negatively related with MD, and this with SIZE.

Lifetime mating success in a marginal population of a damselfly, Coenagrion mercuriale

In scrambling species, where males obtain matings by actively searching for females, the timing and location of mating may be more important to females than choice of males based on phenotype. Since their activity rates are constrained by climate, variation in lifetime reproductive success in marginal populations of scrambling insects may be governed primarily by stochastic processes, limiting the role of selection. Using multivariate analysis, we examined activity patterns and lifetime mating success (LMS) in a marginal British population of Coenagrion mercuriale, a rare, scrambling damselfly, versus that in a core population of a similarly sized scrambling congeneric. Time spent at the breeding site and mating efficiency were the most important factors explaining variation (<75% correct predictions) in LMS in both species, whereas body size, age, and day of entry to the mature population were unimportant. This suggests that LMS in these scrambling species is governed by sexual and natural selection as well as stochastic processes such as weather. However, in C. mercuriale, daily mating and activity rates were highly constrained by poor environmental conditions (and increased with sunlight and temperature). Breeding site visits were so curtailed that an equal distribution of LMS between the sexes was observed. Selection in marginal populations of C. mercuriale may operate upon traits that confer endurance ability in poor environmental conditions rather than body size, life span or age. Climatic variation across species' ranges will in turn generate geographical variation in mating behaviour, in the intensity of sexual selection and the type of traits selected.

FITNESS EFFECTS FROM EGG TO REPRODUCTION: BRIDGING THE LIFE HISTORY TRANSITION

Although complex life cycles are widespread, we know little about how constraints in the larval stage influence adult fitness. Most models assume a tight coupling of larval conditions and adult fitness through size and timing of the life history transition. However, there are few empirical tests of this assumption. We combined an experimental manipulation of larval environment with a subsequent study of adult fitness, measured as lifetime mating success. Individuals of the damselfly Lestes viridis were followed from the egg stage to adult reproduction and death. Under time constraints, emergence occurred earlier, but in late-hatched larvae, this did not result in a lower size. Under nutritional constraints, emergence occurred later, and size was reduced. Variation in survival to maturity was better explained by larval constraints than by emergence traits, whereas both larval constraints and emergence traits explained variation in lifetime mating success. Sexes reacted differently to larval constraints, and the coupling of larval constraints to adult fitness also was sex specific. Our results indicate that larval constraints do not necessarily carry over to adult fitness through size and timing of transition, and that carryover effects may be sex specific. This may explain the existence of hidden costs that become visible after maturation and may explain part of the unexplained variation in selection studies on adults.

Selection on insect immunity in the wild

The strength of selection on immune function in wild populations has only been examined in a few vertebrate species. We report the results from a study measuring selection on a key insect immune enzyme, phenoloxidase (PO), in a wild population of the damselfly Calopteryx xanthostoma. We followed individually marked males from the pre-reproductive adult phase and recorded their lifetime mating success. We found positive selection on PO activity in response to an immune insult, but no selection on wing-spot quality, a trait actively displayed to females during courtship. We suggest that positive selection on PO activity in the year of study may be explained by annual fluctuations in parasite loads.