Divorce in common murres (Uria aalge): relationship to parental quality

Behavioral precursors of 12 divorces were examined in 30 color-banded pairs of common murres (Uria aalge) over six breeding seasons. Common murres are long-lived seabirds that typically return each year to the same mate and nest site in dense colonies. At least one parent is present continuously from egg lay to chick fledging. Murres, therefore, have considerable opportunities to compare their mates parental behavior with that of several familiar neighbors. Previous reproductive success was lower for divorcing birds than for reuniting pairs. As predicted by the better option hypothesis, there were clear choosers (seven females and five males) that initiated divorce by moving to a new birds site or by courting a new partner at their current site. Choosers improved their reproductive success after the divorce, whereas their previous partners, the victims did not. Yearly divorce rates (average 8.2% per year) were significantly correlated with yearly mortality rates. Divorces appear to be opportunistic: pairs divorced after varying numbers of reproductive failures with the immediate precursor usually being the disappearance (death) of a murre from a successful neighboring site. In contrast to the delays experienced by victims, choosers formed new pairs quickly and laid their eggs no later than reuniting pairs. Prior to the divorce, victims fed their chicks less often than choosers, and some engaged in other behaviors that compromised egg or chick survival. These observations suggest that deficiencies in parental behavior were precursors to the divorce. This report is one of the first cases where reproductive failure of divorcing pairs has been linked to deficits in the parental behavior of the subsequent divorce victim.Communicated by C. Brown     

Alternative reproductive tactics in male common shrews: relationships between mate-searching behaviour,sperm production,and reproductive success as revealed by DNA fingerprinting

The common shrew (Sorex araneus) is a solitary small mammal with a promiscuous mating system. Previous studies of this species suggest that females typically mate multiply, and that males may adopt alternative mate-searching tactics. We studied two generations of common shrews in a population near Oxford, England. Males were found to adopt two different mate-searching tactics. Those classed as type A occupied relatively small exclusive ranges during March, and made repeated long-distance movements to visit female ranges around the time of first oestrus in April. Males classed as type B established large overlapping ranges in areas of relatively high female density during March, and maintained these ranges throughout April. Type B males were larger than type A males at an early stage of sexual maturation, but there was no difference in the adult body size of the two types of male. Type A males had significantly higher epididymal sperm counts than type B males. Paternity analyses of litters born during the first year of the study reveal that the mean number of offspring fathered by type B males was greater than the mean number fathered by type A males. It is concluded that different mate-searching tactics may be conditional upon the timing of sexual maturation. Differences in sperm production are discussed in relation to sperm competition theory.     

Racketed tail of the male and female turquoise-browed motmot: male but not female tail length correlates with pairing success,performance, and reproductive success

Both males and females of many avian species maintain elaborate plumage traits, and elaborate monomorphic plumage may convey adaptive benefits to one or both sexes as inter- or intraspecific signals. Both sexes of the turquoise-browed motmot (Eumomota superciliosa) are elaborately plumed with long racket-tipped tail. I investigated whether the racketed tail functions as a sexually selected signal in one or both sexes by testing the predictions that males and/or females with the largest tails have: (1) greater pairing success, (2) greater reproductive performance (clutch-initiation date, clutch size, and hatching success), and (3) greater reproductive success. Yearling males with longer denuded rachises (wires) on the central tail feathers had greater pairing success. In addition, adult males with longer wires paired with females who laid larger clutches, had greater hatching success independent of clutch size, and fledged more young. There was no relationship between female tail plumage and pairing success, reproductive performance, or fledgling success. These results are consistent with the hypothesis that male tail plumage functions as a mate choice or status signal, but that the tail of the female does not function in a sexually selected context. I discuss alternative hypotheses for the evolutionary maintenance of the elaborate female tail plumage.     

Cooperative breeding increases reproductive success in the social spider <Emphasis Type="Italic">Stegodyphus dumicola</Emphasis> (Araneae,Eresidae)

Sociality in some birds, mammals, and social insects was suggested to have evolved through the lengthening and extension of parental care behaviors to nondirect descendents. In these systems, group members care for young cooperatively and, thus, increase the reproductive success of the breeders and fitness of the young. Parental care behaviors, such as regurgitation feeding and matriphagy (consumption of the mother), occur in several subsocial and social spiders. However, it is not known whether females in a colony cooperate in caring for the young of other females and whether such cooperative care improves reproductive success. To answer this question, we created experimental colonies of the social spider Stegodyphus dumicola (Araneae, Eresidae), allowing only one female in a group to produce young, simulating reproductive skew occurring in nests in nature. In this paper, we show for the first time that females of S. dumicola cooperate in providing regurgitated food for young of other females and are even eaten by those young. Young raised by a group of females were larger and had greater survival than young raised only by their mother. Thus, fitness benefits from raising broods cooperatively may have favored the evolution of sociality in spiders.     

Alternative male mating tactics in a cichlid, Pelvicachromis pulcher: a comparison of reproductive effort and success

Pelvicachromis pulcher is a small African cichlid which breeds in holes. Males may either reproduce monogamously (pair males), polygynously (harem males), or be tolerated as helpers in a harem territory (satellite males). These helpers share in defence of the territory against conspecifics, heterospecific competitors and predators. There are two male colour morphs that are fixed for life and are apparently genetically determined. These differ in their potential mating strategy. Red morph males may become harem owners, while yellow morph males may become satellite males, and males of both morphs may alternatively pair up monogamously. We compared the reproductive effort and success of these three male reproductive strategies. Effort was measured as attack rates, time expenditure and the risk of being injured or killed when attacking competitors or predators of three sympatric fish species. Reproductive success was measured by observing how many eggs were fertilized by each male when this was possible, and by using genetic markers. The number of fry surviving to independence of parental care was used as a criterion of success. The reproductive success of harem males was 3.3 times higher than that of pair males and 7 times higher than that of the average satellite male. Dominant satellite males, however, were as successful as monogamous pair males, using the measure of fertilized eggs. To our knowledge, this has not been found previously in any fish species. Both harem and pair males had lower parental defence costs per sired offspring, however, than males using the alternative satellite tactic. Defence effort was significantly related to the risk of injury. Received: 17 January 1996 / Accepted after revision: 9 June 1997     

Biparental investment and reproductive success in a subsocial desert beetle: the role of maternal effort

Parastizopus armaticeps is a nocturnal subsocial detritivorous desert tenebrionid that produces very few offspring per brood. The two environmental factors that constrain reproduction, rapid sand desiccation rate and food scarcity, are countered by biparental effort. Males dig and extend breeding burrows, maintaining their moisture level; females forage on the surface at night for high-quality detritus, the larval food. This was shown to be a scarce and unpredictable resource for which there is high competition. When food was supplemented in a field experiment, offspring number and survivorship doubled and burrow failure due to desiccation dropped from approximately half, the typical failure rate for unsupplemented burrows, to zero. Food supplementation did not, however, increase larval foodstore size and there was no difference in the size of the offspring produced. Supplemented females reallocated their time, foraging less and digging more with the male. This change in maternal behaviour patterns resulted in deeper burrows which remained moist longer, thus extending the larval production period. Female foraging efficiency, particularly food retrieval speed, determined how much time females could allocate to digging, consequently increasing the reproductive success of the pair. Burrow depth and sand moisture level at the burrow base were the major correlates of reproductive success, but the scarcity and unpredictability of high-quality food on the surface and the competition for this resource influenced the number of offspring indirectly through their effect on female behaviour. Received: 29 November 1996 / Accepted after revision: 7 December 1997     

MHC, health, color, and reproductive success in sand lizards

Good genes are genetic elements that contribute to lifetime reproductive success, regardless of an individuals additional genotype. Their existence is debated, and most work has targeted their viability benefits to the offspring of choosy females. In the present study, we analyze a case of potential good genes effects in adult male sand lizards (Lacerta agilis). We show that males with a particular RFLP (Restriction Fragment Length Polymorphism) MHC genotype (O-males), as opposed to those that lack this genetic element (NO-males), have less ectoparasites under increasing physiological stress (indexed by baseline corticosterone level), and are not constrained by parasites at production of status coloration. Furthermore, O-males are more successful at mate acquisition and guard their partners longer. Ultimately, they have a higher genetic reproductive success as assigned by microsatellites.Communicated by W. Cooper     

Differences in reproductive success between laboratory and wild-derived golden hamsters (Mesocricetus auratus) as a consequence of inbreeding

All laboratory golden hamsters (Mesocricetus auratus) originated from a sibling pairing back in 1930. Due to this extreme founder event, domestic golden hamsters are presumed to be one of the most bottlenecked animal populations. Nevertheless, domestic hamsters show no obvious signs of inbreeding depression in commonly used breeding stocks. To explore the existence of potentially masked inbreeding effects, we compared the reproductive success of laboratory (lab) and wild-derived (wild) golden hamsters. We allowed oestrus females to mate consecutively with lab and wild males. The resulting offspring was genotyped using microsatellites to assess paternity. Finally, we compared male reproductive success to genetic variability, sexual behaviour and different sperm characteristics. Both hamster strains exhibited the expected large difference in genetic diversity (H _wild =0.712±0.062 vs H _lab =0.007±0.007. The reproductive success of wild males dramatically exceeded that of lab males (87% of pups were sired by wild males). Sexual behaviour of wild and lab males only varied in the number of long intromissions (intromissions without ejaculation at the end of the mating). No significant differences were observed in relation to mounting, ejaculation and intromission. There were also no apparent differences in sperm motility, velocity and density or testis histology between wild and lab hamsters. We conclude that the reduced reproductive success of lab males represents a hidden inbreeding effect, although its precise physiological cause remains unclear. These results provide first evidence for a major fitness disadvantage in captive golden hamsters.     

The interrelationships between resource-holding potential,resource-value and reproductive success in territorial males: How much variation can we explain?

A long-standing hypothesis in behavioural ecology posits that males with greater resource-holding potential (RHP) control resource sites deemed more valuable by sexually-receptive females and, thereby, males controlling such sites accrue greater reproductive success (RS). This hypothesis has historically been investigated using three separate but non-mutually exclusive relationships (male RHP vs. resource value, resource value vs. male RS and male RHP vs. RS). The relationships between these three variables are predicted to be strongly positive, however, due to measurement error and biological noise, perfect correlations (r = 1.0) are rare in biology even for well-established relationships. Moreover, the inaccurate identification of either the male trait(s) important to RHP or the resource characteristic sought by females will weaken the observed strength of the relationships. Here, I use meta-analysis to quantitatively describe the general pattern of these relationships in animals. I predict that the relationships between male RHP, resource-value and RS should be significantly positive (male RHP and resource-value should explain a large amount of the variation in male RS). My meta-analysis supports this hypothesis; however, in the best case scenario only ca. 20% of the variation in the response variable was explained. I conclude by identifying areas in which we need to improve our investigations of resource-defence animals and recommending approaches to meet these needs. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mating system and individual reproductive success of sympatric anadromous and resident brook charr, <Emphasis Type="Italic">Salvelinus fontinalis</Emphasis>, under natural conditions

Salmonids are known for the occurrence in sympatry of two life-history forms, one that undergoes migration to sea before returning to freshwater to reproduce (anadromous) and one that inhabits freshwater without a migration phase (resident). Whereas one breeding population is often suggested by population genetic studies, mating patterns have rarely been directly assessed, especially when both sexes are found within each life-history form. By using highly polymorphic microsatellite loci and parentage analysis in a natural population of sympatric anadromous and resident brook charr (Salvelinus fontinalis), we found that gene flow occurred between the two forms and was mediated by resident males mating with both resident and anadromous females. Determinants of reproductive success, estimated by the number of surviving juveniles (ages 1 and 2 years), differed between the sexes. No strong evidence of the influence of size on individual reproductive success was found for males, whereas larger females (and hence most likely to be anadromous) were more successful. The higher individual reproductive success of anadromous fish compared to residents was mainly explained by this higher reproductive success of anadromous females. We suggest that resident males adopt a “sneaking” reproductive tactic as a way of increasing their reproductive success by mating with females of all sizes in all habitats. The persistence of the resident tactic among females may be linked to their advantage in accessing spatially constrained spawning areas in small tributary streams unavailable to larger females.     

Divergent effects of climate change on the egg-laying opportunity of species in cold and warm regions

Climate warming can substantially impact embryonic development and juvenile growth in oviparous species. Estimating the overall impacts of climate warming on oviparous reproduction is difficult because egg-laying events happen throughout the reproductive season. Successful egg laying requires the completion of embryonic development as well as hatching timing conducive to offspring survival and energy accumulation. We propose a new metric—egg-laying opportunity (EO)—to estimate the annual hours during which a clutch of freshly laid eggs yields surviving offspring that store sufficient energy for overwintering. We estimated the EO within the distribution of a model species, Sceloporus undulatus, under recent climate condition and a climate-warming scenario by combining microclimate data, developmental functions, and biophysical models. We predicted that EO will decline as the climate warms at 74.8% of 11,407 sites. Decreasing hatching success and offspring energy accounted for more lost EO hours (72.6% and 72.9%) than the occurrence of offspring heat stress (59.9%). Nesting deeper (at a depth of 12 cm) may be a more effective behavioral adjustment for retaining EO than using shadier (50% shade) nests because the former fully mitigated the decline of EO under the considered warming scenario at more sites (66.1%) than the latter (28.3%). We advocate for the use of EO in predicting the impacts of climate warming on oviparous animals because it encapsulates the integrative impacts of climate warming on all stages of reproductive life history.     

Experimental assessment of ecological and phenotypic factors affecting male mating success and polyandry in northern watersnakes, Nerodia sipedon

To resolve conflicting field observations regarding the action of sexual selection, we used breeding experiments and paternity analysis of the 927 resulting offspring to assess how male size, condition, tail length, genetic similarity to the female, and variation in operational sex ratio (OSR) affected male reproductive success and the incidence of polyandry in northern watersnakes (Nerodia sipedon). Only size affected male mating success. Large males were more successful, but only when male size varied substantially and competition among males was intense (i.e., male-biased OSR). The conditional nature of the size advantage may explain why studies of free-living watersnakes have produced inconsistent results regarding the relationship between male size and mating success. Size differences between males did not affect the proportion of offspring each male sired within multiply sired litters. We found positive size-assortative mating, but only when the OSR was female biased, suggesting that smaller males had improved access to females when competition among males was reduced, but that competition with larger males still restricted mating opportunities of small males to less preferred, smaller females. Most litters (58%) were multiply sired and larger females were more likely to produce multiply sired litters, similar to free-living watersnakes. There was no association between the incidence of multiple paternity and OSR, however, suggesting that polyandry is not simply a function of opportunity, with females passively waiting for males to court them.     

Relationship between body size, provisioning rate, longevity and reproductive success in females of the solitary bee Osmia cornuta

Body size has often been related to reproductive success in bees and wasps. The objective of this 3-year study was to analyze the relationship between nesting female body size, provisioning rate and longevity and their effect on several traits related to parental investment and reproductive success in the solitary bee Osmia cornuta. Body size was not correlated to longevity, and it was only correlated to provisioning rate in the third year (with poor weather conditions during nesting). Variation in fecundity, offspring size and offspring mortality was not well explained by nesting female body size in any of the 3 years. However, in the third year, small females biased their investment toward males, the sex requiring smaller pollen–nectar provisions. Large females were more successful usurpers of other females' nests, but fecundity of usurpers was no higher than fecundity of nonusurpers. Large females were more likely to establish at the release site, probably in relation to size-dependent vigor at emergence. A review of the literature on parental investment in solitary aculeate Hymenoptera showed a stronger relationship between body size and reproductive success in wasps than in bees. In O. cornuta, fecundity was strongly related to longevity and provisioning rate in all 3 years. Offspring size was associated with provisioning rate in 1 year, when females with higher provisioning rates tended to produce larger sons and daughters. Both longevity and provisioning rate appeared to be strongly conditioned by stochastic events.     

Infant care,infanticide, and female reproductive strategies in polygynous groups of common marmosets (Callithrix jacchus)

Reproduction in marmoset and tamarin groups is typically restricted to a single dominant female, but it is unclear why subordinate females tolerate delayed reproduction. The presence of two breeding females in free-ranging groups of common marmosets (Callithrix jacchus) presented a unique opportunity to examine differences in the reproductive strategies of dominant and subordinate females. Three groups were monitored for 12–18 months at a forest reserve in northeastern Brazil. Data on infant care were collected during two consecutive all-day follows every 10 days until the infants were 2 months old. Carrying patterns for infants born to dominant females were similar to those observed in groups containing a single breeding female. All group members over 5 months of age participated in infant care, and dominant females allowed some group members to carry their infants from the 1 st day of life. In contrast, subordinate females were protective of their offspring and were their sole caretakers for at least a week following birth. One infant born to a subordinate was killed in an attack involving the dominant female. Overall, dominant females gave birth to more infants and had higher infant survival than did subordinate breeding females. subordinate females were successful in rearing young only when the timing of births was such that they did not overlap with the dependency period of infants born to the dominant female. These patterns suggest that subordinate females may face resource competition, especially over access to helpers. In times of severe competition, subordinate females that delay reproduction may be avoiding a wasted reproductive effort.     

村级养殖种植园区碳素物质流分析——以北京市平谷区西柏店村为例

将西柏店村畜禽养殖规模折合为1.5万头猪场当量污染负荷,并将整个园区生产工艺分为养殖、废弃物处理和种植3个阶段,不考虑隐藏流的情况下,以1年为系统边界,通过数据调查、已有资料研究和小区种植试验,采用物质流分析方法分析了西柏店村养殖种植园区在整个生产工艺的碳素流动,以期为村级养殖种植园区大力发展低碳经济提供新的方法和视角,为村级区域循环经济及可持续发展提供减少环境压力解决方案的科学依据。通过园区养殖种植过程的C素分析表明,养殖阶段年输入C素总量为112.52×10^4 kg,其中猪身总固碳量为40.04×10^4 kg,粪碳和尿碳总量为49.29×10^4 kg,以CO2形式代谢排出的C为23.19×10^4 kg。废弃物处理阶段输入的碳主要为粪碳和尿碳,其总量为49.29×10^4 kg,其中9.79×10^4 kg尿碳直接进入种植阶段,39.50×10^4 kg粪碳进入沼气站处理,沼气转化出的碳为11.02×10^4 kg,其中CH4为8.43×10^4 kg,CO2为2.59×10^4 kg,养殖污水中通过CH4排放再加上其他途径释放的碳约有23.66×10^4 kg,占粪碳量的59.89%。进入种植阶段的碳素主要为尿碳、沼渣和沼液的碳素,合计为14.61×10^4 kg,假设该村43 hm^2耕地能全部施用沼肥,不计其他作物种植,1季玉米种植土壤可库存有机碳为60.50×10^4 kg,为进入种植阶段碳素14.61×10^4 kg的4倍,还可增加植物有机碳27.31×10^4 kg。由C素流动分析可知,西柏店村具有可容纳该村养殖废弃物的环境容量,有较好实现养殖废弃物循环利用的条件,但需大力加强畜禽废弃物的管理和处理,提高园区养殖废弃物循环利用效率。     

The impact of behavioral and physiological maternal effects on offspring sex ratio in the common snapping turtle,<Emphasis Type="Italic"> Chelydra serpentina</Emphasis>

Theory suggests that maternal effects are especially important in organisms with environmentally-sensitive sex-determining mechanisms. However, there is no substantive body of empirical evidence to confirm this conjecture. We integrated field and laboratory studies to jointly evaluate the significance of behavioral (nest-site choice) and physiological (yolk hormone allocation) maternal effects on offspring sex ratio in the common snapping turtle (Chelydra serpentina), a species with temperature-dependent sex determination (TSD). Of the 16 microhabitat variables measured, only three (south, east, and total overstory vegetation cover) were significantly correlated with nest temperature: cooler nests were located under more vegetation cover. In turn, these microhabitat predictors of nest temperature, and nest temperature itself, may influence nest sex ratio: shadier, cooler nests were more likely to produce a higher proportion of male offspring than less shady, warmer nests. Analysis of eggs from these same nests incubated in a common garden design in the laboratory revealed that clutch sex ratio was unaffected by levels of yolk estradiol, yolk testosterone, or their interaction. Examination of both behavioral and physiological maternal effects revealed no concordant impact on offspring sex ratio. However, eggs from nests that produced male-biased sex ratios in the field yielded higher proportions of males under constant-temperature conditions in the laboratory. Our study confirms the importance of behavioral maternal effects in nature on offspring sex ratios in species with TSD, while also revealing the potential presence of a predisposition for sex-ratio production underlying TSD in this system.Communicated by S. Krackow