Correlates of extra-pair fertilization success in hooded warblers

We examined correlates of extra-pair fertilization (EPF) success in the hooded warbler (Wilsonia citrina), a species where females pursue extra-pair matings. The good genes hypothesis predicts that females choose extra-pair mates with morphological or behavioral traits that reflect differences in male genetic quality. EPFs were common, as 35.3% (42/119) of broods contained extra-pair young (EPY) and 26.7% (95/356) of nestlings were the result of EPFs. There was a strong skew in male EPF success which increased the variance in annual male mating success 2–3 fold. However, male morphology did not predict EPF success, as extra-pair males were not older or larger than the males they cuckolded. Likewise, there were no significant correlations between the proportion of extra-pair young in a brood and male size or age. The good genes hypothesis predicts that high-quality males will be consistently preferred as genetic mates, but the number of young sired by a male with his social mate was not consistent from one year to the next. There was a significant negative correlation between female age and proportion of EPY produced, which could result if older females obtain higher-quality social mates. We found no strong evidence that females choose extra-pair mates for good genes, but females may use behavioral rather than morphological cues to assess relative male quality. Received: 31 May 1996 / Accepted after revision: 17 October 1996     

Genetics of growth in blue mussels: family and enzyme-heterozygosity effects

Shell length and electrophoretic heterozygosity at six enzyme loci were scored in juveniles of 30 hatchery-grown families and in adults of 10 field-grown families of the blue mussel Mytilus edulis. A total of 4 809 offspring were scored. We found no consistent pattern in the correlations between shell length and enzyme heterozygosity among sibs within families. However, a significant family effect on shell length was observed, suggesting an influence of background genotype on this character. A family effect on viability was also observed. When the environment and family effects were accounted for, a small positive correlation between heterozygosity and shell length at the juvenile stage remained. This correlation was significant in one of the three experiments. No such correlation was evident at the adult stage. Our interpretation of these results is that electrophoretic alleles appear to have no direct of independent effect of their own on growth. We suggest that the negative correlation of homozygosity with these characters, seen in natural populations, results from homozygosity for hidden recessive deleterious genes with which the electromorphs are in a steady state of quasilinkage disequilibrium.     

Are behavioral syndromes invariant? Spatiotemporal variation in shy/bold behavior in squid

Behavioral syndromes are correlated suites of behavior, analogous to human personality traits. Most work to date has been taken from limited “snapshots” in space and time, with the implicit assumption that a behavioral syndrome is an invariant property, fixed by evolutionary constraints or adaptations. However, directional selection on two mechanistically independent traits (selective covariance) could also result in correlated behaviors. Previously, we have shown that shy/bold behavior in Southern dumpling squid (Euprymna tasmanica) across predator encounter and feeding risk contexts is genetically and phenotypically uncoupled, and hence potentially free to vary independently. Here, we collected data on shy/bold behaviors from two independent wild populations of squid in two different years to test whether behavioral correlations across these same two functional contexts vary through time and space. We detected significant influences of population, sex, and body size on the expression of boldness in squid within each functional context, and this was coupled with significant differences in relative population density and adult sex ratio. Despite these changes in behavior and demographic parameters, we found that correlations between boldness scores across the two functional contexts were largely absent in both wild populations of squid in both years. Our work suggests that some animal groups may be largely characterized by context-specific behavioral expression. A theoretical framework which conceptualizes behavioral syndromes resulting from context-specific behavioral rules may be needed to fully understand why behaviors are sometimes correlated, and why sometimes they are not.     

Female choice of multiple male criteria in guppies: interacting effects of dominance,coloration and courtship

Summary I experimentally examined the relative importance of social dominance, color patterns, and courtship behavior in male mating and reproductive success in the guppy Poecilia reticulata. Female choice of males is based on a complex set of behavioral and morphological traits. The results of 59 paired-male one-female visual choice and mating trials showed that male mating success was positively correlated with dominance, courtship intensity, and male coloration. Only dominant males engaged in full copoulations, and they sired two-thirds of the broods. An analysis of the paternity of broods and results of mating trials showed that a female's visual response when the sexes are separated by a glass partition is a good predictor of a male's reproductive success when the partition is removed and they are allowed to mate. A canonical correlation analysis of male behavioral and morphological traits indicated that female visual response and male mating success were positively correlated with male courtship and with agonistic behavior. However, the relative importance of color varied. Carotenoid and iridescent spots were important both in attracting the female's attention and in enhancing male mating success. Melanins were not correlated with either mating success or female response. There was a relatively low correlation (48%) between male behavioral and morphological variables and female response variables (full copulation and female visual response). These results suggest that female choice is subtle, and is based on a complex suite of male behavioral and morphological traits as well as on competitive interactions among males.     

Behavioral type–environment correlations in the field: a study of three-spined stickleback

Behavioral type–environment correlations occur when specific behavioral types of individuals are more common in certain environments. Behavioral type–environment correlations can be generated by several different mechanisms that are probably very common such as niche construction and phenotypic plasticity. Moreover, behavioral type–environment correlations have important ecological and evolutionary implications. However, few studies have examined behavioral type–environment correlations in natural populations. In this study, we asked whether some behavioral types of three-spined stickleback were more likely to occur in certain social environments (alone or in a shoal with other stickleback) or in certain microhabitats in a river (in the open or under cover). We found that individuals that were in shoals with other stickleback at the time of collection from the field emerged from a refuge more quickly compared to individuals that were found alone. In addition, fish that were alone in an open microhabitat explored more of a pool compared to fish that were alone in cover, but this difference did not occur among fish that were in shoals at the time of collection. Subsequent analyses of gut contents suggested that differences in microhabitat use were consistent over time. Our study provides some of the first evidence for behavioral type–environment correlations in a natural population of non-human animals.     

Sex bias or equal opportunity? Patterns of maternal investment in bison

Summary In polygynous mammals, it may be adaptive for mothers to invest more in sons and/or to adjust the sex ratio of offspring in relation to body condition. Calving patterns were examined over an 8-year period (1982–1989) for a population of Bison bison in which barren females are not selectively culled. From these data, we tested predictions of the sex ratio adjustment hypothesis as well as two assumptions: (1) that offspring weight at the end of the period of parental investment (PI) is correlated with later condition, and (2) that maternal and offspring condition during the period of PI are correlated. In contrast to predictions, there was little evidence that mothers in better condition bear more sons. Short- and long-term measures of maternal condition (previous reproductive status, age, dominance status, pre-pubertal body weight, age at first reproduction, birth date, and the duration of the mother's own suckling period) were little related to offspring sex ratio, although the last calves of old females were nearly always female. Similarly, there was little evidence for sex-biased PI. Weights at about 7 months of age were greater for males than females; males also had somewhat later birth dates, suggesting either longer gestation or later conception. However, maternal reproductive costs, as measured by subsequent fecundity, weight loss, and interbirth intervals, did not vary with calf sex. Both assumptions of the model received some support. However, while maternal condition was correlated with offspring condition, there may be sex differences in investment patterns. Mothers appear better able to influence the condition of daughters than of sons. This sex difference may negate any benefit from male-biased investment.     

Behavioral correlations across activity, mating, exploration, aggression, and antipredator contexts in the European house cricket, Acheta domesticus

Recently, there has been increasing interest in behavioral syndrome research across a range of taxa. Behavioral syndromes are suites of correlated behaviors that are expressed either within a given behavioral context (e.g., mating) or between different contexts (e.g., foraging and mating). Syndrome research holds profound implications for animal behavior as it promotes a holistic view in which seemingly autonomous behaviors may not evolve independently, but as a “suite” or “package.” We tested whether laboratory-reared male and female European house crickets, Acheta domesticus, exhibited behavioral syndromes by quantifying individual differences in activity, exploration, mate attraction, aggressiveness, and antipredator behavior. To our knowledge, our study is the first to consider such a breadth of behavioral traits in one organism using the syndrome framework. We found positive correlations across mating, exploratory, and antipredatory contexts, but not aggression and general activity. These behavioral differences were not correlated with body size or condition, although age explained some of the variation in motivation to mate. We suggest that these across-context correlations represent a boldness syndrome as individual risk-taking and exploration was central to across-context mating and antipredation correlations in both sexes.     

Song repertoires and reproductive success in the great reed warbler Acrocephalus arundinaceus

Summary The relationship between song repertoire size and reproductive success was investigated in a population of great reed warblers breeding in southern Germany. No correlations were found between repertoire size and various measures of male quality such as weight, wing length and age. Repertoire size was not correlated with territory size, but showed strong correlations with some measures of territory quality such as the amount of high quality reeds and reed-water interface. Repertoire size and territory quality were both correlated with various measures of reproductive success. Partial correlation analysis revealed that territory quality had a more significant effect upon the number of females obtained, but that repertoire size had a more significant effect upon the number of young produced.     

Swimming performance trade-offs across a gradient in community composition in Trinidadian killifish (Rivulus hartii)

The impacts of predation and competition on life history, behavioral, and morphological traits are well established for many organisms, but effects on locomotor performance have received relatively little attention. We examined variation in sprint speed and critical swimming speed (U(crit), a measure of stamina) in the Trinidadian killifish (Rivulus hartii) across a gradient of ecological communities. R. hartii are located in (1) "high-predation" sites with large, piscine piscivores, (2) "Rivulus-guppy" sites with guppies, and (3) "Rivulus-only" sites with only R. hartii. R. hartii suffer higher mortality in high-predation sites. In Rivulus-guppy sites, population densities are reduced and growth rates increased compared with Rivulus-only sites, which likely represent indirect effects of guppy predation on young R. hartii. We show a significant negative relationship, suggesting a trade-off, between sprint speed and endurance; Rivulus from high-predation sites were faster sprinters but had reduced critical swimming speeds. This trade-off was also apparent in correlations of the nine population means. At the individual level, the correlation was weaker and only significantly negative when all nine populations (three from each site) were pooled and values were not corrected for body size. Sex had a significant effect on U(crit), with females having a lower U(crit), but sexes did not differ in sprint speed. Fish from high-predation sites also exhibited increased tail lengths and fineness ratios compared to sites without large predators. The two low-predation sites showed no statistical differences in locomotor performance or morphology.     

甘蔗不同叶位叶片形态与冠层特征的关系

利用CI-100数字植物冠层分析仪和CI-203叶面积分析仪测定了4个甘蔗品种不同叶位层的冠层参数和相应叶位叶片的形态特征，结果表明：不同基因型不同叶位层问叶片形态、冠层空间结构和冠层辐射特征存在显著差异，不同叶位层叶面积指数、叶簇倾角和叶分布的变化主要由冠层内不同叶位叶片叶宽的变化引起，而不同叶位层消光系数的变化主要与叶簇倾角和叶分布有关；散射光透过系数的变化主要与叶面积指数、叶簇倾角和叶分布有关，直射光透过系数的变化主要与叶分布、叶宽、长宽比有关，光合有效辐射的变化与叶面积指数、叶面积、叶宽、长宽比有关．研究结果同时表明，叶片形态与冠层辐射特征存在显著的典型相关关系．图2表4参15。     

Reproductive sharing and proximate factors mediating cooperative breeding in the African wild dog (Lycaon pictus)

Although dominant African wild dogs (Lycaon pictus) are generally believed to be the sole breeders within a pack, earlier behavioral and endocrine data suggest that reproduction could be shared with subordinates. We performed an extensive behavioral, demographic, and genetic evaluation of a wild dog population in South Africa to examine the level of such sharing and the proximate mechanisms influencing reproductive contributions of each sex. While a majority of pups were born to dominants because of a lack of subordinate potential breeders, we discovered a substantial portion of reproductive sharing between dominants and subordinates. Compared with alpha females that mated annually, subordinate beta females bred in 54.5% of years whereas thetas never bred. The three top-ranking males all sired pups (56.0%, 32.0%, and 12.0%, respectively) when three or more adult males were present. With only two pack males, alpha and beta individuals shared reproduction nearly equally (55.2% and 44.8%, respectively), and litters of mixed paternity were discovered on eight of 15 (53.3%) occasions. A skewed adult sex-ratio and frequent alpha mortalities for females and behavioral aggression in males allowed most individuals to attain dominant status in their lifetime, creating a constantly shifting social hierarchy. Genetic parentage results corresponded to reported hormone profiles, suggesting physiological suppression in some lower-ranked individuals of both sexes. Thus, a combination of demographic, behavioral, and hormonal proximate factors mediates reproductive partitioning in wild dogs. We conclude that reproductive sharing can be significant in this species, especially for males that have less robust suppressive mechanisms than females.     

Pairing patterns in relation to body size,genetic similarity and multilocus heterozygosity in a tropical monogamous bird species

The relative influence of genetic and phenotypic quality on pairing status and mating patterns in socially monogamous species remains poorly documented. We studied social status and pairing patterns in relation to genetic similarity and multilocus heterozygosity (MLH) estimates from 11 microsatellite markers, and both tarsus length and wing chord (as a measure of competitive ability in territorial defence) in a socially monogamous tropical bird species where individuals defend territories year-round, alone or in pairs, the Zenaida dove, Zenaida aurita. Tarsus length and wing chord did not differ between unpaired territorial birds and paired ones in either sex, whereas paired females, but not paired males, tended to be more heterozygous than unpaired ones. Among 84 pairs, we found no evidence for assortative mating for tarsus length, wing chord, MLH or genetic similarity. However, within pairs, male wing chord was positively related to female MLH and female tarsus length was positively related to male MLH, with no evidence for local effects, suggesting assortative mating by individual quality. Although the observed pattern of mating in Zenaida doves may be the product of mutual mate choice, further assessment of this hypothesis requires direct investigation of both mating preference in each sex and lifetime reproductive success in relation to body size and MLH.     

Maternal effects on post-weaning physical and social development in juvenile mountain goats (Oreamnos americanus)

Little is known about maternal effects on post-weaning development, yet they may be important because maternal care could have long-term consequences only evident when offspring approach adulthood. We have assessed the effects of maternal age, current reproduction (presence of a kid of the year) and social rank on the body mass, horn length and social rank of 1- and 2-year-old mountain goats (Oreamnos americanus). Maternal reproductive status and social rank did not affect the mass or horn length of either yearlings or 2-year-olds. Maternal age was positively correlated with yearling body mass for males but not females. We could not detect any maternal age effects on body mass of 2-year-olds. Maternal age and spring forage quality were positively correlated with horn length of yearlings of both sexes, but not of 2-year-olds. Juvenile females showed compensatory growth in mass between 1 and 2 years of age, but males did not. Neither sex showed compensatory growth in horn length. None of the maternal characteristics we examined directly affected the social rank of juveniles, which increased with body mass. Social rank in female mountain goats seems to be established early in life and maintained to adulthood. By affecting yearling development, maternal age could affect the reproductive success of males.     

Male mating competitiveness and age-dependent relationship between testosterone and social rank in bighorn sheep

In males, the acquisition and development of behavioral and morphological secondary sexual traits typically depends on testosterone and correlates with mating success. Testosterone level could affect competition for mates and thus be a target of sexual selection. We sought to relate testosterone levels to male mating competitiveness, by teasing apart the relationships between testosterone, behavior, and growth before the mating period. We monitored 24 adult bighorn rams (Ovis canadensis) at Ram Mountain, Alberta, from 2008 to 2011. Using linear mixed models, we tested the relationships between testosterone metabolites in feces, social rank, and both growth and size of two sexually selected traits: horns and body mass. The correlation between testosterone and social rank varied with age. Testosterone and rank were weakly and negatively correlated for young rams, positively correlated for prime-aged rams, and negatively correlated for older rams. Although testosterone had an increasingly positive effect on total horn length until 8 years of age, we could not detect any effects on annual growth rate of horns or body mass. Testosterone may be related to male’s ability to compete for mates through its relationship with behaviors determining social rank, rather than by influencing the development of morphological traits. Differences in testosterone levels among competitors may be a proximate cause of variance in fitness.     

不同底质和透明度下马来眼子菜的表型可塑性研究

马来眼子菜(Potamogeton malaianusMiq.)是目前太湖沉水植物优势种之一。文章比较分析了3种不同底质和透明度情况下马来眼子菜的生长特征,探索其在太湖不断扩展的原因及其适应性。分别选取粘土质粉砂、粉砂和下蜀黄土底质上生长的马来眼子菜进行观察试验。结果表明,这3种底质在粒度组成、营养盐和分布特征上具有显著差异。在太湖粘土质粉砂和粉砂底质上马来眼子菜的生物量比下蜀黄土底质上的马来眼子菜高,其生物量随着底质营养盐的增加而增加。马来眼子菜与觅光相关的形态指标,如高度、节间距、节数、叶数、叶长及叶面积均随着底质营养盐的增加而显著增加。马来眼子菜的冠层高度与水体的透明度呈显著负相关,表明其对剧烈变化的湖泊光环境具有很强的适应能力。马来眼子菜在不同底质上的形态可塑性是其优先占据湖泊资源成为优势种的重要原因。     

Insects perceive local sex ratio in the absence of tactile or visual sex-specific cues

Numerous studies have demonstrated adaptive behavioral responses of males and females to changes in operational sex ratio (the ratio of potentially receptive males to receptive females; OSR), and theory often assumes that animals have perfect instantaneous knowledge about the OSR. However, the role of sensory mechanisms in monitoring the local sex ratio by animals and whether animals can perceive local sex ratio in a manner consistent with model assumptions have not been well addressed. Here, we show that mating water striders Gerris gracilicornis respond to local sex ratio even when visual and physical contact with other individuals were experimentally prohibited. Our study shows that insects are able to estimate local population's sex ratio and adjust their behavior based on nonvisual cues perceived at a distance or released to the habitat. Hence, the frequent theoretical assumption that individuals have knowledge about their local sex ratio regardless of their direct behavioral interactions may be an acceptable approximation of reality.     

Estimation of age in the sex-changing, coral-inhabiting snail Coralliophila violacea from the growth striae on opercula and a mark–recapture experiment

Change of sex in the coral-inhabiting snail Coralliophila violacea (Lamarck) may occur in a wide range of sizes in the field. One proposed explanation for this is that the snails change their sex at a certain age and that individuals have different growth rates caused by microhabitat differences. In this study, we attempt to establish a method to determine the age of this snail and age at sex change. The growth striae on the operculum were studied and compared to the age estimated by the Gompertz growth function based on growth data obtained from mark-recapture experiments in southern Taiwan. There is a significant correlation between the number of striae on the operculum and the age estimated from the Gompertz growth function, and the relationship is 1:1. These results suggest that the number of striae on the operculum can be used as an age index, with each stria representing 1 year of age. The age of sex change of this snail, according to our estimates by both stria number and aperture-length inferences, occurs between 4 and 6 years old. Growth rates of the snails are negatively correlated to size. Furthermore, individuals undergoing sex-change grow faster than males and females.     

Age before beauty? Relationships between fertilization success and age-dependent ornaments in barn swallows

When males become more ornamented and reproduce more successfully as they grow older, phenotypic correlations between ornament exaggeration and reproductive success can be confounded with age effects in cross-sectional studies, and thus say relatively little about sexual selection on these traits. This is exemplified here in a correlative study of male fertilization success in a large colony of American barn swallows (Hirundo rustica erythrogaster). Previous studies of this species have indicated that two sexually dimorphic traits, tail length and ventral plumage coloration, are positively correlated with male fertilization success, and a mechanism of sexual selection by female choice has been invoked. However, these studies did not control for potential age-related variation in trait expression. Here, we show that male fertilization success was positively correlated with male tail length but not with plumage coloration. We also show that 1-year-old males had shorter tails and lower fertilization success than older males. This age effect accounted for much of the covariance between tail length and fertilization success. Still, there was a positive relationship between tail length and fertilization success among older males. But as this group consisted of males from different age classes, an age effect may be hidden in this relationship as well. Our data also revealed a longitudinal increase in both tail length and fertilization success for individual males. We argue that age-dependent ornament expression and reproductive performance in males complicate inferences about female preferences and sexual selection.     

Phenotypic correlates and survival consequences of male mating success in lek-mating greater prairie-chickens (<Emphasis Type="Italic">Tympanuchus cupido</Emphasis>)

Female choice and male–male aggression are two modes of sexual selection that can lead to elaboration of male morphological and behavioral traits. In lek-mating species, male mating success is often strongly skewed, and it is puzzling why variation in male traits is still observed given directional female choice. If male traits correlated with reproductive success are honest signals of male quality, there may be survival costs associated with the expression of those traits. In this study, we examined whether morphological, behavioral, and territorial traits are correlated with male mating success and survival in the lek-mating greater prairie-chicken (Tympanuchus cupido). We introduce a novel application of multinomial discrete choice models for analysis of female mate choice behavior. We found that behavioral and territorial attributes showed 6.5 times more variability among males than morphological traits. Both display and aggressive behaviors were strong predictors of male mating success, suggesting that both female choice and male–male aggression were important in determining mating success among male greater prairie-chickens. Moreover, annual survival of male prairie-chickens was independent of mating success and male traits. Females appear to be choosing males based on behavioral traits where large variation exists between males (coefficient of variation >30%). Behavioral traits were the most important factor in determining mating success of male prairie-chickens, but the mechanism underlying this relationship is unknown. In the future, experimental manipulations of male hormones or parasite loads could bridge the proximate mechanisms and ultimate consequences of factors mediating male mating success in lek-mating grouse.     

Interactions between metals accumulated in the narrow-clawed crayfish Astacus leptodactylus (Eschscholtz, 1823) in Dikilitaş Lake,Turkey

The accumulations of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn in the exoskeleton, gills, hepatopancreas and abdominal muscles of crayfish Astacus leptodactylus (Eschscholtz, 1823) were determined. The strongest correlation observed was between Cr and Ni in the gills (r?=?0.904); moderate to strong correlations between Al, Cr, Fe, Ni and Cu were also observed in gill tissue. Disregarding the gills, the strongest correlation was found between Cu and Zn in the hepatopancreas (r?=?0.808); the correlation between these two metals might have been a result of metallothionein activity. The accumulation of Pb was found to correlate with that of Cd in the exoskeleton, Cd and Zn in the gills, Zn and Cu in the hepatopancreas and Cu in the abdominal muscle. None of these correlations were present in lakewater and sediment samples, suggesting that the crayfish metabolism may be responsible for the co-accumulation of metal–metal pairs. As all correlations in non-gill tissues are observed between divalent metals, a shared transporter such as divalent metal transporter 1 might be involved in the accumulation of these metals.