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1.
Sexual selection theory predicts that, when body size is correlated with fecundity, there should be fitness advantages for mate choice of the largest females. Moreover, because larger males are expected to monopolise the largest females, this should result in an assortative mating based on body size. Although such patterns could be expected in both explosive and prolonged breeders, non‐assortative mating should be more widespread in species under time constraints. However, patterns of sexual selection are largely unexplored in explosive breeding species, and contrasting patterns have been found previously. We expect that the active choice of partners may be particularly risky when the time period during which sexual partners are available is severely limited. Therefore, to avoid missing an entire reproductive act, males and females should pair irrespective of traits, such as body size. We tested this hypothesis by investigating the mating patterns of the Pacific horned toad, Ceratophrys stolzmanni, a short‐lived fossorial species inhabiting Neotropical dry forests. This species is particularly adequate to test our prediction because it reproduces explosively over the course of a single night per year. Although the number of eggs laid was proportional to the size of females, and individuals of both sexes showed variation in body size, there was no assortative mating based either on size, body condition or age of mates. Egg size was not influenced by either female size or clutch size. The larger body size of females compared to males is likely due to fecundity selection, that is, the selective pressure that enhances reproductive output. Although we cannot dismiss the possibility that individuals could select their partners based on other criteria than those related to size or age, the results fit well our prediction, showing that the explosive breeding makes improbable an active choice of partners in both sexes and therefore favours a random mating pattern.  相似文献   

2.
In many damselfly species mature females exhibit colour polymorphism: one female morph resembles the conspecific male (androchrome) while the others do not (gynochromes). Hypotheses for the maintenance of such polymorphisms differ mainly as to whether they are based on density- and/or frequency-dependent selection and on the nature of the frequency dependence. We collected lifetime fitness data (individual lifespan, number of copulations and number of ovipositions) for female morphs of the damselfly Ischnura elegans from 15 insectaries differing in population parameters (density, sex ratio and ratio of andro- to gynochromes). Both density and frequency affected a specific set of the studied fitness components. While morph frequency influenced lifespan, sex ratio influenced the number of copulations, and density affected lifespan and the number of ovipositions. Clearly, discrepancies among studies may be generated if the studied fitness components differ. Our final fitness estimate, the number of ovipositions, was only influenced by density, thereby not supporting frequency-based hypotheses. Contrary to expectation under the current density-based hypothesis, androchromes compared to gynochromes had a lower number of ovipositions at high density. We discuss our findings in the light of mechanisms maintaining the female polymorphism.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 515–523.  相似文献   

3.
In polygynandrous animals, post‐copulatory processes likely interfere with precopulatory sexual selection. In water striders, sexual conflict over mating rate and post‐copulatory processes are well documented, but their combined effect on reproductive success has seldom been investigated. We combine genetic parentage analyses and behavioural observations conducted in a competitive reproductive environment to investigate how pre‐ and post‐copulatory processes influence reproductive success in Gerris buenoi Kirkaldy. Precopulatory struggles had antagonistic effects on male and female reproductive success: efficiently gaining copulations was beneficial for males, whereas efficiently avoiding copulations was profitable for females. Also, high mating rates and an intermediate optimal resistance level of females supported the hypothesis of convenience polyandry. Contrary to formal predictions, high mating rates (i.e. the number of copulations) did not increase reproductive success in males or decrease reproductive success in females. Instead, the reproductive success of both sexes was higher when offspring were produced with several partners and when there were few unnecessary matings. Thus, male and female G. buenoi displayed different interests in reproduction, but post‐copulatory processes were masking the effects of copulatory mating success on reproductive success. Given the high mating rates observed, sperm competition could easily counter the effect of mating rates, perhaps in interaction with cryptic female choice and/or fecundity selection. Our study presents a complex but realistic overview of sexual selection forces at work in a model organism for the study of sexual conflict, confirming that insights are gained from investigating all episodes in the reproduction cycle of polygynandrous animals.  相似文献   

4.
Previous studies on the reproductive biology of littorinid snails have focused on rocky shore species, investigating how these gastropods can achieve maximal reproductive success, as well as on processes of sexual selection. This study documented differences in the reproductive traits of two mangrove‐dwelling littorinids, Littoraria ardouiniana and L. melanostoma, in Hong Kong. Reproductive activity of both species was most intense during the summer months. Mating pairs of the two species generally occurred in the tree canopies. Few false mating pairs (same sex or heterospecific pairs: <10%) were recorded, and members of both species showed size‐assortative mating. Littoraria ardouiniana had a shorter reproductive season but a higher intensity of mating and higher seasonal fecundity, than did L. melanostoma. Members of both species showed bi‐lunar periodicities of egg or larval release, synchronized with spring tides. Fecundity showed a strong positive relationship with body size in L. ardouiniana, but not in L. melanostoma. Females of L. ardouiniana released entire broods of larvae in a single brief event, whereas females of L. melanostoma released fewer eggs over 1–8 d. Release of larvae in L. ardouiniana involved a series of short bursts and was much faster than the trickle release of eggs in L. melanostoma. The contrasting reproductive traits in these two species represent different strategies to optimize reproductive success in mangrove habitats.  相似文献   

5.
Understanding life history traits is an important first step in formulating effective conservation and management strategies. The use of artificial propagation and supplementation as such a strategy can have numerous effects on the supplemented natural populations and minimizing life history divergence is crucial in minimizing these effects. Here, we use single nucleotide polymorphism (SNP) genotypes for large‐scale parentage analysis and pedigree reconstruction in a hatchery population of steelhead, the anadromous form of rainbow trout. Nearly complete sampling of the broodstock for several consecutive years in two hatchery programmes allowed inference about multiple aspects of life history. Reconstruction of cohort age distribution revealed a strong component of fish that spawn at 2 years of age, in contrast to programme goals and distinct from naturally spawning steelhead in the region, which raises a significant conservation concern. The first estimates of variance in family size for steelhead in this region can be used to calculate effective population size and probabilities of inbreeding, and estimation of iteroparity rate indicates that it is reduced by hatchery production. Finally, correlations between family members in the day of spawning revealed for the first time a strongly heritable component to this important life history trait in steelhead and demonstrated the potential for selection to alter life history traits rapidly in response to changes in environmental conditions. Taken together, these results demonstrate the extraordinary promise of SNP‐based pedigree reconstruction for providing biological inference in high‐fecundity organisms that is not easily achievable with traditional physical tags.  相似文献   

6.
Animal personality has been studied extensively in recent years, yet multidimensionality in tendencies of risk‐related behavior, and the role of such consistency from a mating tactics perspective, is yet to be investigated. We used a semi‐domesticated herd of reindeer (Rangifer tarandus) to examine individual subdominant male propensity to risk mating attempts on guarded females, as well as flight initiation distance (FID), within the personality paradigm to elucidate potential fitness consequences of consistency from an adaptive perspective. Data were collected at the Kutuharju Reindeer Research Station in Kaamanen, Finland, where measures of personality were generated using field observation data based on the relative frequency of dominant male–subdominant male agonistic interactions over 4 years and subdominant males' FID measured over 1 year. Individual propensity for transient mating attempts was not significantly repeatable and did not significantly predict reproductive success or somatic cost during the mating season. Individuals varied consistently in FID, and although repeatable, FID was not related to reproductive success or somatic cost. Proximate state‐dependent or social mechanisms may be driving decision‐making with respect to mating effort, whereas consistent between‐individual differences in FID may be maintained by mechanisms unrelated to life‐history trade‐offs involving productivity.  相似文献   

7.
Polymorphic genes involved in the conserved molecular signalling of circadian and circannual clocks may play important roles in governing the timing of breeding and dispersal and thereby affect fitness in vertebrates. However, relatively few studies have explored associations between phenological candidate genes and behaviour, and these are somewhat biased towards particular taxonomic groups such as passerine birds and salmonid fish. Consequently, we assayed microsatellite polymorphisms within the exonic and 3′ untranslated regions of the regulatory genes CLOCK, NPAS2, ADCYAP1 and CREB1 in the common buzzard (Buteo buteo), a polymorphic raptor species with three plumage morphs that differ in key life history traits including lifetime reproductive success. In contrast to studies of passerines, CLOCK poly‐glutamine (poly‐Q) was found to be monomorphic in 976 common buzzard nestlings as well as in three other Buteo species. Moreover, none of the candidate genes were significantly associated with fledging dates, although intermediately melanized females were found to lay earlier on average than light or dark morph individuals, and their offspring carried longer ADCYAP1 alleles. In contrast, all three candidate genes explained significant variation in one or more measures of juvenile buzzard dispersal (resighting probability, timing of dispersal and distance dispersed). Our findings contribute towards a broader body of work on the adaptive significance of CLOCK polymorphism, while also building upon previous studies that have documented links between ADCYAP1 variability and the timing of migration.  相似文献   

8.
Both differences in local plant density and phenotypic traits may affect pollination and plant reproduction, but little is known about how density affects trait–fitness relationships via changes in pollinator activity. In this study we examined how plant density and traits interact to determine pollinator behaviour and female reproductive success in the self‐incompatible, perennial herb Phyteuma spicatum. Specifically, we hypothesised that limited pollination service in more isolated plants would lead to increased selection for traits that attract pollinators. We conducted pollinator observations and assessed trait–fitness relationships in a natural population, whose individuals were surrounded by a variable number of inflorescences. Both local plant density and plant phenotypic traits affected pollinator foraging behaviour. At low densities, pollinator visitation rates were low, but increased with increasing inflorescence size, while this relationship disappeared at high densities, where visitation rates were higher. Plant fitness, in terms of seed production per plant and per capsule, was related to both floral display size and flowering time. Seed production increased with increasing inflorescence size and was highest at peak flowering. However, trait–fitness relationships were not density‐dependent, and differences in seed production did not appear to be related to differences in pollination. The reasons for this remain unclear, and additional studies are needed to fully understand and explain the observed patterns.  相似文献   

9.
Multiple pathways exist for species to respond to changing climates. However, responses of dispersal‐limited species will be more strongly tied to ability to adapt within existing populations as rates of environmental change will likely exceed movement rates. Here, we assess adaptive capacity in Plethodon cinereus, a dispersal‐limited woodland salamander. We quantify plasticity in behavior and variation in demography to observed variation in environmental variables over a 5‐year period. We found strong evidence that temperature and rainfall influence P. cinereus surface presence, indicating changes in climate are likely to affect seasonal activity patterns. We also found that warmer summer temperatures reduced individual growth rates into the autumn, which is likely to have negative demographic consequences. Reduced growth rates may delay reproductive maturity and lead to reductions in size‐specific fecundity, potentially reducing population‐level persistence. To better understand within‐population variability in responses, we examined differences between two common color morphs. Previous evidence suggests that the color polymorphism may be linked to physiological differences in heat and moisture tolerance. We found only moderate support for morph‐specific differences for the relationship between individual growth and temperature. Measuring environmental sensitivity to climatic variability is the first step in predicting species' responses to climate change. Our results suggest phenological shifts and changes in growth rates are likely responses under scenarios where further warming occurs, and we discuss possible adaptive strategies for resulting selective pressures.  相似文献   

10.
There is discussion over whether pollen limitation exerts selection on floral traits to increase floral display or selects for traits that promote autonomous self‐fertilization. Some studies have indicated that pollen limitation does not mediate selection on traits associated with either pollinator attraction or self‐fertilization. Primula tibetica is an inconspicuous cross‐fertilized plant that may suffer from pollen limitation. We conducted a selection analysis on P. tibetica to investigate whether pollen limitation results in selection for an increased floral display in case the evolution of autonomous self‐fertilization has been difficult for this plant. The self‐ and intra‐morph incompatibility features, the capacity for autonomous self‐fertilization, and the magnitude of pollen limitation were examined through hand‐pollination experiments. In 2016, we applied selection analysis on the flowering time, corolla width, stalk height, flower tube length, and flower number in P. tibetica by tagging 76 open‐pollinated plants and 37 hand‐pollinated plants in the field. Our results demonstrated that P. tibetica was strictly self‐ and intra‐morph incompatible. Moreover, the study population underwent severe pollen limitation during the 2016 flowering season. The selection gradients were found to be significantly positive for flowering time, flower number, and corolla width, and marginally significant for the stalk height. Pollinator‐mediated selection was found to be significant on the flower number and corolla width, and marginally significant on stalk height. Our results indicate that the increased floral display may be a vital strategy for small distylous species that have faced difficulty in evolving autonomous self‐fertilization.  相似文献   

11.
  1. Overwintering Drosophila often display adaptive phenotypic differences beneficial for survival at low temperatures. However, it is unclear which morphological traits are the best estimators of abiotic conditions, how those traits are correlated with functional outcomes in cold tolerance, and whether there are regional differences in trait expression.
  2. We used a combination of controlled laboratory assays, and collaborative field collections of invasive Drosophila suzukii in different areas of the United States, to study the factors affecting phenotype variability of this temperate fruit pest now found globally.
  3. Laboratory studies demonstrated that winter morph (WM) trait expression is continuous within the developmental temperature niche of this species (10–25°C) and that wing length and abdominal melanization are the best predictors of the larval abiotic environment.
  4. However, the duration and timing of cold exposure also produced significant variation in development time, morphology, and survival at cold temperatures. During a stress test assay conducted at ?5°C, although cold tolerance was greater among WM flies, long‐term exposure to cold temperatures as adults significantly improved summer morph (SM) survival, indicating that these traits are not controlled by a single mechanism.
  5. Among wild D. suzukii populations, we found that regional variation in abiotic conditions differentially affects the expression of morphological traits, although further research is needed to determine whether these differences are genetic or environmental in origin and whether thermal susceptibility thresholds differ among populations within its invaded range.
  相似文献   

12.
13.
Inbreeding depression, the reduction in fitness due to mating of related individuals, is of particular conservation concern in species with small, isolated populations. Although inbreeding depression is widespread in natural populations, long‐lived species may be buffered from its effects during population declines due to long generation times and thus are less likely to have evolved mechanisms of inbreeding avoidance than species with shorter generation times. However, empirical evidence of the consequences of inbreeding in threatened, long‐lived species is limited. In this study, we leverage a well‐studied population of gopher tortoises, Gopherus polyphemus, to examine the role of inbreeding depression and the potential for behavioural inbreeding avoidance in a natural population of a long‐lived species. We tested the hypothesis that increased parental inbreeding leads to reduced hatching rates and offspring quality. Additionally, we tested for evidence of inbreeding avoidance. We found that high parental relatedness results in offspring with lower quality and that high parental relatedness is correlated with reduced hatching success. However, we found that hatching success and offspring quality increase with maternal inbreeding, likely due to highly inbred females mating with more distantly related males. We did not find evidence for inbreeding avoidance in males and outbred females, suggesting sex‐specific evolutionary trade‐offs may have driven the evolution of mating behaviour. Our results demonstrate inbreeding depression in a long‐lived species and that the evolution of inbreeding avoidance is shaped by multiple selective forces.  相似文献   

14.
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.  相似文献   

15.
According to Bateman's principle, female fecundity is limited relative to males, setting the expectation that males should be promiscuous, while females should be choosy and select fewer mates. However, several surfperches (Embiotocidae) exhibit multiple paternity within broods indicating that females mate with multiple males throughout the mating season. Previous studies found no correlation between mating success and reproductive success (i.e., a Bateman gradient). However, by including samples from a broader range of reproductive size classes, we found evidence of a Bateman gradient in two surfperch species from distinct embiotocid clades. Using microsatellite analyses, we found that 100% of the spotfin surfperch families sampled exhibit multiple paternity (Hyperprosopon anale, the basal taxon from the only clade that has not previously been investigated) indicating that this tactic is a shared reproductive strategy among surfperches. Further, we detected evidence for a Bateman gradient in H. anale; however, this result was not significant after correction for biases. Similarly, we found evidence for multiple paternity in 83% of the shiner surfperch families (Cymatogaster aggregata) sampled. When we combine these data with a previous study on the same species, representing a larger range of reproductive size classes and associated brood sizes, we detect a Bateman gradient in shiner surfperch for the first time that remains significant after several conservative tests for bias correction. These results indicate that sexual selection is likely complex in this system, with the potential for conflicting optima between sexes, and imply a positive shift in fertility (i.e., increasing number) and reproductive tactic with respect to the mating system and number of sires throughout the reproductive life history of females. We argue that the complex reproductive natural history of surfperches is characterized by several traits that may be associated with cryptic female choice, including protracted oogenesis, uterine sac complexity, and sperm storage.  相似文献   

16.
Mating patterns and natural selection play important roles in determining whether genetic polymorphisms are maintained or lost. Here, we document an atypical population of Lapeirousia anceps (Iridaceae) with a bimodal distribution of floral‐tube length and investigate the reproductive mechanisms associated with this pattern of variation. Flowers were visited exclusively by the long‐proboscid fly Moegistorhynchus longirostris (Nemestrinidae), which exhibited a unimodal distribution of proboscis length and displayed a preference for long‐tubed phenotypes. Despite being visited by a single pollinator species, allozyme markers revealed significant genetic differentiation between open‐pollinated progeny of long‐ and short‐tubed phenotypes suggesting mating barriers between them. We obtained direct evidence for mating barriers between the floral‐tube phenotypes through observations of pollinator foraging, controlled hand pollinations and measurements of pollen competition and seed set. Intermediate tube‐length phenotypes produced fewer seeds in the field than either long‐ or short‐tubed phenotypes. Although floral‐tube length bimodality may not be a stable state over long timescales, reproductive barriers to mating and low ‘hybrid’ fitness have the potential to contribute to the maintenance of this state in the short term.  相似文献   

17.
Aims: To analyse the occurrence of faecal carriage of vancomycin‐resistant enterococci (VRE) in Buteo buteo and to study the associated resistance and virulence genes. Methods and Results: The presence of VRE was investigated in 33 faecal samples of B. buteo. Samples were seeded in Slanetz–Bartley agar plates supplemented with vancomycin for VRE recovery. Genes encoding antimicrobial resistance and virulence were studied by polymerase chain reaction. Vancomycin‐resistant Enterococcus faecium isolates were characterized by multilocus sequence typing. VRE with an acquired mechanism of resistance (vanA genotype) were detected in 9% of samples analysed (Ent. faecium and Enterococcus durans). In addition, 27% of samples contained VRE with an intrinsic mechanism of resistance (Enterococcus gallinarum, vanC1). All vanA‐containing isolates showed resistance to tetracycline and erythromycin and harboured the tet(M) and/or tet(L) genes, in addition to the ermB gene. The vat(E) and/or vat(D), cat(A) and aph(3′)‐IIIa genes were identified in quinupristin–dalfopristin‐, chloramphenicol‐, and kanamycin‐resistant vanA‐containing strains, respectively. The sequence types ST273 and ST5 were identified in two vanA‐positive Ent. faecium isolates, and the presence of hyl, gelE, cylA, cylL and cylM virulence genes and gelatinase activity were identified in Ent. faecium ST5 strain. Conclusions: The intestinal tract of B. buteo could be a reservoir of vanA‐positive enterococci. Significance and Impact of the Study: First study focused to define the occurrence of vanA‐containing Enterococcus strains in B. buteo.  相似文献   

18.
Dispersal is a key process in population and evolutionary ecology. Individual decisions are affected by fitness consequences of dispersal, but these are difficult to measure in wild populations. A long‐term dataset on a geographically closed bird population, the Mauritius kestrel, offers a rare opportunity to explore fitness consequences. Females dispersed further when the availability of local breeding sites was limited, whereas male dispersal correlated with phenotypic traits. Female but not male fitness was lower when they dispersed longer distances compared to settling close to home. These results suggest a cost of dispersal in females. We found evidence of both short‐ and long‐term fitness consequences of natal dispersal in females, including reduced fecundity in early life and more rapid aging in later life. Taken together, our results indicate that dispersal in early life might shape life history strategies in wild populations.  相似文献   

19.
Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage‐dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage‐specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.  相似文献   

20.
Ornaments displayed by females have often been denied evolutionary interest due to their frequently reduced expression relative to males, habitually attributed to a genetic correlation between the sexes. We estimated annual and lifetime reproductive success of female pied flycatchers (Ficedula hypoleuca) and applied capture–mark–recapture models to analyse annual survival rates in relation to the patterns of expression (absence/presence) of an ornament displayed by all males and a fraction of females. Overall, the likelihood of expressing the ornament increased nonlinearly with female age and was due to within‐individual variation, not to the selective appearance or disappearance of ornament‐related expression of phenotypes in the population. Accordingly, expressing the forehead patch in a given year did not influence survival probability. However, those females expressing the ornament at early ages (1–2 years old) enjoyed survival advantages throughout lifetime. Although ornamented females had higher lifetime fecundity and fledging success, their yearly reproductive performance, in terms of fledging productivity, decreased as they aged so that, late in life, ornamented females reared fewer offspring than nonexpressing females of the same age. In addition, both strategies (expressing vs. not expressing the trait) returned similar fitness payoffs in terms of recruited offspring. Our results support the hypothesis that fecundity and survival selection are involved in the displaying of this ‘male’ ornament by females.  相似文献   

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