Long-term dynamic of fecal corticosterone and its ecological and social correlates in males of great gerbil (Rhombomys opimus Licht.). Non-invasive approach in studies of stress in natural populations

The relationship between fecal corticosterone concentrations and characteristics of the environment and population demography were studied in adult male gerbils (Rhombomys opimus Licht.) at the southern border of Kyzylkum desert (Reserve "Ecocentre Dzeiran", Bukhara region, Republic Uzbekistan) in spring and fall seasons from 1999 to 2004. We extracted hormones from air-dried fecal samples and analyzed their concentrations by radioimmunoassay (Gerlinskaya et al., 1993). An analysis for year-specific relationships between hormone concentrations and environmental variables of temperature and precipitation using Pearson's r statistic revealed that corticosterone concentrations correlated positively with total precipitation in January and February and negatively with precipitation during March and April. There was also a significant negative relationship between fecal corticosterone and the number of hot days in March (>20 degrees C). Demographic variables that characterized population densities (percent of burrow systems occupied, mean and maximum number of burrow systems/1 ha, number of females in the burrow system) correlated positively with corticosterone concentrations in feces in the beginning of spring, but these relationships were small compared with mean concentrations of corticosterone for the entire spring season that were strongly and positively correlated with number of gerbils, including all pups emerged, in burrow systems owned by one male (within its home range). In contrast, correlation coefficients of corticosterone concentrations with characteristics of feeding resources in the spring were low and negative. In the long-term perspective (interannual comparison), mortality among adult males was highly negatively correlated with mean corticosterone concentrations in the beginning of spring, which is within the period of maximum reproductive effort and potential stress. Body mass was independent of corticosterone concentrations in males in either the beginning of spring, or during the whole spring. In the fall, mean concentrations of fecal corticosterone in males was positively correlated with the number of days from June to October with mean daily temperatures exceeding 30 degrees C, and with percent of burrow systems where at least one adult, > or = 1 year old gerbil had survived. Mortality from fall to spring of the next year and the fall body mass did not correlate with concentrations of corticosterone in feces collected in the fall. When we analyzed corticosterone concentrations in spring seasons of all years combined using a stepwise regression analysis of a sampling of individual males (we analyzed residuals after withdrawal of year effect) on a set of variables representing habitat resources, distances between nearest neighbor males, and variables representing group demography we found low R2 values not exceeding 0.17. Within the six-year period, concentrations of corticosterone in the spring related negatively with abundance of annual herbs and positively with number of females in a male's social group. When only years of high density were analyzed, fecal corticosterone concentrations in males in the spring were again negatively determined by abundance of herbs, as well as by the nearest neighbor distance, and positively determined by the number of females within a male's home range. At the beginning of spring the only determinants were distance to the nearest neighbor male and number of females. In years of low density none of the variables were found to affect corticosterone levels during the whole spring, while in the beginning of spring only partial regression coefficients of abundance of herbs were negative and significant. Stepwise logistic regression analysis revealed positive dependence (P = 0.05) of disappearance of adult males during summer drought on concentrations of fecal corticosterone in the spring, but only when burrow systems with at least one adult (male or female) surviving after the summer were considered. Our results provide evidence ground for the assumption that in a desert rodent with non-regular population fluctuations such as the great gerbil, density may be more suppressed by external factors and not by density dependent mortality mediated by stress. Density dependent increases of stress caused by intense reproductive effort occurred when feeding and climatic conditions were favorable to compensate for negative effects on survival. However, in individual gerbils mortality mediated by stress can take place because we found higher stress in the beginning of spring in males, which did not occur in the population after the summer drought.     

Spatial organisation and dynamics of the pine marten Martes martes population in Białowieza Forest (E Poland) compared with other European woodlands

We studied factors affecting density and spacing patterns in the pine marten Martes martes population inhabiting temperate forests of Bia?owieza National Park, eastern Poland. From 1985/1986 to 1995/1996 marten densities ranged from 3.63 to 7.57 individuals 10 km^?2 (mean 5.4) and were positively correlated with abundance of forest rodents in the previous year. The rate of marten population growth was inversely density‐dependent and positively related to rodent density. Annual mortality rate averaged 0.384 and tended to be negatively related to marten densities. Mean annual home range of males (2.58 km², SE=0.24) was larger than that of females (1.41 km², SE=0.20). Seasonal home ranges also differed significantly between males and females. Both sexes held the smallest ranges in December–January. Female ranges increased in April–May, whereas those of males increased in June–September when they were mating. Fidelity of pine martens to their home ranges was very high. The mean shift between arithmetic centres of seasonal ranges was 0.25 km, and the ranges recorded in two consecutive seasons overlapped, on average, by 87–90%. We observed very little home range overlap between neighbouring male (mean 4–6%) or female (mean 6%) marten. Year round the neighbouring individuals of the same sex neither avoided nor attracted each other. Females attracted males only during the spring‐summer mating season. A review of other studies has documented that winter severity and seasonal variation in ecosystem productivity were essential factors shaping the biogeographic variation in pine marten densities between 41^o and 68^oN. The density of marten populations increased in areas with mild winters and lower seasonality. Maximum population densities (indicative of habitat carrying capacity) were correlated with mean winter temperature. In Europe, male home ranges increased with decreasing forest cover in a study area, whereas female ranges varied positively with rodent abundance.     

Warm temperatures during cold season can negatively affect adult survival in an alpine bird

Climate seasonality is a predominant constraint on the lifecycles of species in alpine and polar biomes. Assessing the response of these species to climate change thus requires taking into account seasonal constraints on populations. However, interactions between seasonality, weather fluctuations, and population parameters remain poorly explored as they require long‐term studies with high sampling frequency. This study investigated the influence of environmental covariates on the demography of a corvid species, the alpine chough Pyrrhocorax graculus, in the highly seasonal environment of the Mont Blanc region. In two steps, we estimated: (1) the seasonal survival of categories of individuals based on their age, sex, etc., (2) the effect of environmental covariates on seasonal survival. We hypothesized that the cold season—and more specifically, the end of the cold season (spring)—would be a critical period for individuals, and we expected that weather and individual covariates would influence survival variation during critical periods. We found that while spring was a critical season for adult female survival, it was not for males. This is likely because females are dominated by males at feeding sites during snowy seasons (winter and spring), and additionally must invest energy in egg production. When conditions were not favorable, which seemed to happen when the cold season was warmer than usual, females probably reached their physiological limits. Surprisingly, adult survival was higher at the beginning of the cold season than in summer, which may result from adaptation to harsh weather in alpine and polar vertebrates. This hypothesis could be confirmed by testing it with larger sets of populations. This first seasonal analysis of individual survival over the full life cycle in a sedentary alpine bird shows that including seasonality in demographic investigations is crucial to better understand the potential impacts of climate change on cold ecosystems.     

Seasonal population dynamics of Pallisentis (Neosentis) celatus (Acanthocephala: Quadrigyridae) in the intestine of the rice-field eel Monopterus albus in China

Studies on the seasonal population dynamics of Pallisentis (Neosentis) celatus (Acanthocephala: Quadrigyridae) in the intestine of the rice-field eel Monopterus albus from the paddies and ditches in the Dong-ting Lake basin of China, were carried out with samples taken from June 2002 to May 2003. Prevalences were above 21% in all seasons sampled and with a distinct seasonal trend, which was highest (45.81%) in the spring and decreased by degrees. The mean intensity of infection was above 4.0 worms per fish. The maximum intensity of worms recovered from a single fish was 86 in the autumn of 2002. No significant seasonal differences were found in mean intensities, and differences in the mean abundance between winter and spring, winter and autumn were significant. Over-dispersed distributions of P. (N.) celatus in the host population, due to heterogeneity and feeding habits, were observed in all seasons. The size composition of both sexes of P. (N.) celatus showed males between 2.0 mm and 14.0 mm and females between 2.2 mm and 22.2 mm, with the main recruitment phase in the worm populations occurring in the summer and autumn, especially in the autumn, with the lowest recruitment occurring in the winter. The maturation and copulation of worms were mainly focused in the spring season. The sex ratio of female to male was both high in summer (1.09:1) and autumn (1.08:1). The higher proportion of females and the change in the worm sex ratio in summer can be attributed to the reduced longevity of male worms. As immature male worms exhibit a higher proportion of the worm population than females in all seasons, further studies are needed to determine if such a situation compensates for the shorter life span of males.     

5. GENERAL NOTES

Olive Thrushes Turdus olivaceus olivaceus in Grahamstown, South Africa, were present in their territories throughout the year. Mist-net captures showed no seasonal fluctuation in the population density of adults. The breeding season had a main peak from August to November and a minor peak in April. Song output was greatest at the beginning of the breeding periods, when territorial boundaries were most keenly contested. There was a positive correlation between seasonal variation in breeding intensity and song output. The adult survival rate was estimated at 80%, and 56% of the fledglings were alive in their natal territories at the age of independence. In this study area, only females built nests and brooded nestlings. Only males sang. Both males and females defended their territories.     

Influence of weather and phenotypic characteristics on pregnancy rates of female roe deer in central Italy

In many ungulates, female fecundity is influenced by weather, population density and body condition. Based on a six-year survey of the reproductive tracts of adult female roe deer (Capreolus capreolus) harvested in the province of Pisa (Tuscany, central Italy), we evaluated the influence of weather, population density and individual characteristics on pregnancy rates. Eighty-five percent of females were pregnant, with a median litter size of two (range one—three). We found that pregnancy rate was positively correlated with summer rainfall and body mass of females, whereas early-winter conditions, spring rainfall, the age of females and density-dependent factors did not appear to influence pregnancy rate. These results reflect the particular seasonal variation in the abundance and quality of resources in Mediterranean habitats and show that heavier females (high-quality mothers) are more productive than lighter females.     

Seasonal population dynamics of Neoechinorhynchus qinghaiensis in the carp, Gymnocypris przewalskii przewalskii, from Qinghai Lake, China

Studies on the seasonal population dynamics of Neoechinorhynchus qinghaiensis (Acanthocephala: Neoechinorhynchidae) in its fish host Gymnocypris przewalskii przewalskii in the Qinghai Lake, China, were carried out with samples taken in May 1991, August 1992, November 1992 and February 1993. Prevalences were higher than 44% in all seasons. The mean intensity of infection was above 124 worms per fish. The maximum intensity of worms recovered from a single fish was 1402 in the autumn of 1992. Differences in the mean abundance, mean intensity and prevalence are not statistically significant relative to season and this is likely to be related to the stable temperatures recorded at the bottom of Qinghai Lake. Over-dispersed distributions of N. qinghaiensis in the host population, due to heterogeneity and feeding habits, were observed in all seasons. The size composition of both sexes of N. qinghaiensis showed males to be less than 3.5 mm and females between 0.5 and 4.25 mm, with the main recruitment phase in the worm populations occurring in the autumn, extending through winter and spring with the lowest recruitment occurring in the summer. The maturation and copulation of worms were mainly focused in the summer season. The sex ratio of female to male was both high in winter (1.51:1) and spring (1.48:1). The higher proportion of females and the change in the worm sex ratio in winter can be attributed to the reduced longevity of male worms. As immature male worms exhibit a higher proportion of the worm population than females in all seasons, further studies are needed to determine if such a situation compensates for the shorter life span of males.     

Size- and density-dependent reproductive success of bagworms, Metisa plana

A study conducted in a Malaysian plantation of oil palm over 5 consecutive generations of bagworms, Metisa plana (Walker) (Lepidoptera: Psychidae), evaluated extent and causes of variability for 3 components of reproductive success: pupal mortality, mating success and fecundity. The population of M. plana in the experimental site exhibited cycles of 70–80 days with discrete generations. Females emerged before males during all generations. Relatively large proportions of M. plana did not reproduce, either because they did not survive as pupa or (for females) mate as adult. Occurrence of unmated female bagworms may be attributed to complex mating procedure, short lifespan of females, limited mating capacity of males, protogyny inducing female-biased operational sex-ratio, and/or flightlessness per se constraining mating success of females. Size attained at pupation is a significant component of reproductive success, with large individuals having greatest survival during pupal stage, mating success and fecundity. Population density also influenced reproductive success of M. plana: female and (to a lesser extent) male larvae on crowded palms attained small size at pupation; survival of pupae was density-dependent during 2 generations for females and density-independent during 5 generations for males; mating success of females was inverse density-dependent during 4 generations. Size- and density-dependent mating success of females may be attributed to mate choice by males, size-dependent pheromone production by and longevity of females, and/or disorientation of mate-seeking males around heavily infested palms. Long-term studies are needed to determine whether and to what extent attributes of oil palm, seasonal fluctuations of abiotic factors and inter-generational variations of reproductive success influence population dynamics of M. plana.     

Growth and body size in populations of mink frogs Rana septentrionalis from two latitudes

Age, longevity, and growth in mink frogs Rana septentrionalis from two latitudes in Quebec, Canada, were assessed by skeletochronological and back-calculation methods in order to document proximate causes for intraspecific variations in adult body size. In both study sites, females grew faster and were on average 11% larger than males. Mean age and maximal longevity were significantly higher in females than in males only in the southern populations. There was thus an interpopulation difference in the relative contribution of age and growth to sexual size dimorphisms. Sex-ratio also favored females (males sulfering higher mortality) only in the southern populations. Specimens from the northern population had higher mean ages (but not higher longevities) and were 17% larger than specimens from the southern populations. Annual growth rate appeared similar at the two study sites despite a shorter growing season at the northern locality. Maturity was reached by both sexes after 1 yr of post-metamorphic life (PML) in the southern populations but after 2 yr of PML in the northern population. There are indications that tadpoles metamorphose at larger body size at the northern locality after a prolonged larval period. It is concluded that growth rate, delayed maturity, greater mean ages, and eventually size at transformation, all contribute to the larger size of adult mink frogs at northern localities.     

Lack of seasonal and moult-related stress modulation in an opportunistically breeding bird: The white-plumed honeyeater (Lichenostomus penicillatus)

This article is part of a Special Issue “SBN 2014”.In most vertebrate species, glucocorticoid levels and stress sensitivity vary in relation to season and life-history stage. In birds, baseline corticosterone (CORT) and stress sensitivity are typically highest while breeding and decrease substantially during moult. Because elevated CORT adversely affects protein synthesis, moult-related CORT suppression is thought to be necessary for forming high-quality feathers. Surprisingly, some passerine species lack moult-related CORT suppression, but these are distinguished by having slow rates of moult and being opportunistic breeders. We examined baseline and stress-induced CORT levels in an opportunistically breeding Australian passerine, the white-plumed honeyeater (Lichenostomus penicillatus). Although this species has a slower moult rate than high-latitude breeders, it differs little from north-temperate passerines. Neither baseline nor stress-induced CORT levels varied with season (winter, spring or summer), sex or moult status in adult birds. While breeding tended to be highest in early spring through late summer, laparotomies revealed only limited reduction in testicular size in males the year round. In all but one sampling period, at least some females displayed follicular hierarchy. Breeding usually coincides with outbreaks of phytophagous insects, which can happen at any time of the year. This results in moult/breeding overlap when infestations occur in late spring or summer. The ability of this species to moult and breed at the same time while having breeding-levels of CORT demonstrates that CORT suppression is not a prerequisite for synthesis of high-quality feathers. An experimental design incorporating moulting and non-moulting phenotypes is suggested to test the functional significance of CORT suppression in other species.     

Male‐skewed adult sex ratio,survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.     

Home range size and activity of the wood lemming, Myopus schisticolor

We present the results from a radiotelemetric study on space use and activity in a natural population of the wood lemming Myopus schisticolor. Male home ranges were larger than females, and the ratio female home range to male home range was smaller than expected compared to other small rodents. Males moved distances 4-12 times longer than females. We argue that this difference in mobility gives a higher probability of capturing males than females in snap trap studies. If there is a sex biased trappability, this might explain the increasing female biased sex ratio during the snow free season (1:1 in spring, 3:1 [female:male| in autumn), as a higher mortality of males during the reproductive season.     

The Role of Climatic and Density Dependent Factors in Shaping Mosquito Population Dynamics: The Case of Culex pipiens in Northwestern Italy

Culex pipiens mosquito is a species widely spread across Europe and represents a competent vector for many arboviruses such as West Nile virus (WNV), which has been recently circulating in many European countries, causing hundreds of human cases. In order to identify the main determinants of the high heterogeneity in Cx. pipiens abundance observed in Piedmont region (Northwestern Italy) among different seasons, we developed a density-dependent stochastic model that takes explicitly into account the role played by temperature, which affects both developmental and mortality rates of different life stages. The model was calibrated with a Markov chain Monte Carlo approach exploring the likelihood of recorded capture data gathered in the study area from 2000 to 2011; in this way, we disentangled the role played by different seasonal eco-climatic factors in shaping the vector abundance. Illustrative simulations have been performed to forecast likely changes if temperature or density–dependent inputs would change. Our analysis suggests that inter-seasonal differences in the mosquito dynamics are largely driven by different temporal patterns of temperature and seasonal-specific larval carrying capacities. Specifically, high temperatures during early spring hasten the onset of the breeding season and increase population abundance in that period, while, high temperatures during the summer can decrease population size by increasing adult mortality. Higher densities of adult mosquitoes are associated with higher larval carrying capacities, which are positively correlated with spring precipitations. Finally, an increase in larval carrying capacity is expected to proportionally increase adult mosquito abundance.     

Life History of Cercopithecus mitis stuhlmanni in the Kakamega Forest, Kenya

Comparative data from wild populations are necessary to understand the evolution of primate life history strategies. We present demographic data from a 29-yr longitudinal study of 8 groups of individually recognized wild blue monkeys (Cercopithecus mitis stuhlmanni). We provide estimates of life history variables and a life table for females. Most females had their first infant at 7 yr. The mean interbirth interval was 28 mo, and decreased from 31 to 18 mo if the first infant died within a year. Interbirth intervals did not differ according to infant sex, but females had longer intervals after their first vs. subsequent births. Infant mortality was 23% and did not differ strongly by sex or mother’s parity. Maximal female lifespan was 32.5–34.5 yr. Across the lifespan, both survivorship and fecundity showed typical primate patterns. Survivorship was lowest in infants, leveled off among juveniles, and then decreased gradually with increasing age in later life. Fecundity was highest among young females and decreased among older females. Births were seasonal, with 64% occurring within 3 mo at the end of the dry season and beginning of the wet season. Survival to 12 mo was higher for infants born during drier months. Birth season timing is plausibly related to thermoregulation of infants, weanling foods, or maternal energy demand. Blue monkeys are a forest-dependent species with a very slow life history and relatively low immature and adult mortality rates compared to closely related guenons living in open habitats. Even among cercopithecines as a whole, they appear to have an exceptionally slow life history relative to body size. Differences in life history “speed” between blue monkeys and their close relatives seem to be related to lower juvenile and adult mortality in forests relative to more open habitats.     

Reproductive strategies of Diaeretiella rapae (Hymenoptera: Aphidiinae) during fluctuating temperatures of spring season in New Zealand

Reproductive activities of naturally occurring population of Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiinae) on Myzus persicae were studied during spring season in New Zealand. The cabbage seedlings were highly infested with the aphids (272±25 individuals/plant) with about 30% on average parasitised by D. rapae. Rate of parasitism was positively correlated with the aphid density (R ²=0.64). Adult emergence from aphid mummies was 90%, with a higher frequency of females than males. Increase in female/male sex ratio was found between early and late spring (1.1 vs. 1.8). Mating in D. rapae occurred throughout the day. Nearly half of the mating pairs collected were male–male pairs, which were especially prevalent during morning and evening while more male–female mating pairs were found during midday. Male–male mounting was probably because of low number of virgin females in morning and evening populations. About 80% females were mounted by smaller size males. Male–male mounting is discussed in correlation with operational sex ratio of D. rapae population.     

The breeding season duration hypothesis: acute handling stress and total plasma concentrations of corticosterone and androgens in male and female striped plateau lizards (Sceloporus virgatus)

Acute glucocorticoid elevations can be adaptations to short-term stressors. The breeding season hypothesis predicts reduced glucocorticoid responsiveness to acute stressors in populations or species with short breeding seasons. The striped plateau lizard (Sceloporus virgatus) has a short breeding season in Arizona. We measured plasma corticosterone and total androgen levels (dihydrotestosterone and testosterone) following one of the four stress-handling treatments (0, 10, 60, or 180 min). In both sexes, longer handling stress yielded higher corticosterone; females had higher corticosterone than males at all time points. Androgens did not vary with handling duration, in either sex. Combining treatments, plasma androgens correlated positively with corticosterone (CORT) in females but not in males; plasma CORT and body mass residuals were negatively correlated in both sexes, suggesting lizards in poor body condition and/or not investing heavily in reproduction (follicle mass) have higher acute corticosterone. Total plasma androgens and body mass residuals were positively associated in males, but showed no association in females. The maximal CORT elevation after handling stress in this single-clutching species was of comparable magnitude to responses in related multi-clutching lizard species with longer breeding seasons. Using data from studies of multiple populations of three Sceloporus species, we found no relationship between the relative magnitude of the CORT increase and either latitude or elevation, two variables in the literature correlated with duration of the breeding season, and only weak relationships with geographic elevation and actual (not relative) stress-elevated CORT values in this multi-population comparison.     

Reproductive ecology of the jacky dragon (Amphibolurus muricatus): an agamid lizard with temperature‐dependent sex determination

Abstract The jacky dragon, Amphibolurus muricatus (White, ex Shaw 1790) is a medium sized agamid lizard from the southeast of Australia. Laboratory incubation trials show that this species possesses temperature‐dependent sex determination. Both high and low incubation temperatures produced all female offspring, while varying proportions of males hatched at intermediate temperatures. Females may lay several clutches containing from three to nine eggs during the spring and summer. We report the first field nest temperature recordings for a squamate reptile with temperature‐dependent sex determination. Hatchling sex is determined by nest temperatures that are due to the combination of daily and seasonal weather conditions, together with maternal nest site selection. Over the prolonged egg‐laying season, mean nest temperatures steadily increase. This suggests that hatchling sex is best predicted by the date of egg laying, and that sex ratios from field nests will vary over the course of the breeding season. Lizards hatching from eggs laid in the spring (October) experience a longer growing season and should reach a larger body size by the beginning of their first reproductive season, compared to lizards from eggs laid in late summer (February). Adult male A. muricatus attain a greater maximum body size and have relatively larger heads than females, possibly as a consequence of sexual selection due to male‐male competition for territories and mates. If reproductive success in males increases with larger body size, then early hatching males may obtain a greater fitness benefit as adults, compared to males that hatch in late summer. We hypothesize that early season nests should produce male‐biased sex ratios, and that this provides an adaptive explanation for temperature‐dependent sex determination in A. muricatus.     

SEX-RATIO SELECTION IN A BIVOLTINE THRIPS. I. CONDITIONAL SEX-RATIO MANIPULATION AND FITNESS VARIATION

Females of the bivoltine thrips Elaphrothrips tuberculatus (Hood) (Insecta: Thysanoptera) produce broods of either all males (by viviparity) or all females (by oviparity). Measurements of the sex-allocation ratio, ecological and physiological conditions affecting male and female offspring body size, and correlates of the relative fitnesses of adult males and females in relation to size indicate that female parents tend to be viviparous (produce males) if their offspring will become relatively large adults, and that males gain more in fitness from large size than do females. However, the conditions that link sex allocation with offspring fitness differ between the spring and summer generations. In spring, when breeding is synchronous, 1) oviparous and viviparous females do not differ in body size, 2) females tend to be viviparous where the fungus upon which they feed is relatively dense and where their offspring will become relatively large adults, and 3) fungus density is highly correlated with male and female offspring size. In summer, when breeding is relatively asynchronous, 1) viviparous females are much larger than oviparous females early (but not late) in the season, 2) large viviparous females begin breeding earlier than smaller ones, 3) offspring developing earlier in the season become larger adults, and 4) a higher proportion of females are viviparous earlier than later. Field experiments and field collections show that the covariation among sex allocation, conditions, and fitness is not caused by differential mortality by size or sex. Differences between the spring and summer generations in the cues used by females to adjust offspring sex ratio may be caused by seasonal variation in the factors that affect offspring size. However, in both generations, females tend to produce sons only when their offspring will become relatively large adults, whereas daughters are produced regardless of offspring size. These data suggest that females of E. tuberculatus avoid production of males (the sex with higher variance in expected fitness) when the size of their offspring is relatively uncertain.     

Male ornamentation and its condition-dependence in a paternal mouthbrooding cardinalfish with extraordinary sex roles

Cardinalfishes, in which males alone provide mouthbrooding, are likely candidates for sex-role reversal because of a higher potential reproductive rate for females than for males. In the gregarious cardinalfish, Apogon notatus, females establish breeding territories to form pairs prior to the breeding season. Within breeding pairs, females are more active in courtship and in attacks against conspecific intruders. Sex roles thus seem to be behaviorally reversed. The operational sex ratio is, however, male-biased because females suffer higher mortality than males and consequently males predominate in number in the adult population, leading to the prediction that males would be sexually selected. In the present study, morphological measurements showed that males had a protrudent lower lip that was expressed markedly during the breeding season. Field observation revealed that males with a longer and wider lip were preferentially accepted as a mating partner by territorial females. The male lip size positively correlated with their somatic condition, suggesting that the ornamental lip has evolved through indicator mechanisms of sexual selection. By contrast, females had longer fins than males, but these sexual dimorphisms were less pronounced and most of them were seasonally constant. These results support the prediction that sexual selection acts on males in this fish. Electronic Publication     

Seasonal variation of mortality,detectability, and body condition in a population of the adder (Vipera berus)

We analyzed seasonal variation in mortality rates in adult males and females of the European adder (Vipera berus), using data collected during a 13‐year capture–recapture study (2005–2017) in a large population. We concurrently obtained quantitative information on the seasonal variation in the detectability and body condition of adders. Our results show strong seasonality in body condition, encounter, and capture rates of adult adders, and these patterns differ markedly between sexes and between breeding and nonbreeding females. Seasonal variation in mortality rates was however virtually nonexistent in males and moderately low in both breeding and nonbreeding females. In addition, we found no evidence for among‐year differences in the seasonal mortality schedules of males and females. During periods of intensive basking, both males and pregnant females are highly visible for humans, but are not subject to strong natural mortality. This low susceptibility to predation is presumably induced by various factors, including the limitation of overt exposure to short periods of time and specific microhabitats, the dorsal coloration pattern that provides cryptic protection and possibly also an aposematic warning signal, and presumed seasonal differences in the foraging behavior and food requirements of natural predators. Our data provide some evidence that female adders, but not males, are relatively vulnerable to predation during the seasonal migrations between the hibernation and feeding habitats. Mortality in the females was not much elevated during their breeding years, but was notably highest in the spring of the ensuing nonbreeding year. After giving birth, reproductive females are extremely emaciated and have a weakened general condition. They then run the risk of dying from starvation either before, during, or after hibernation. The higher mortality after giving birth, that is sustained over a period of ca. 9 months, should be considered as an indirect and delayed survival cost of reproduction.