Fertility in South Australian commercial Merino flocks: aspects of management

Wide variation in reproductive performance of commercial Merino flocks in south central Australia is the result of genetic and environmental influences that are both amenable to change through decisions of management. Relationships of reproductive traits (estrus, ovulation, fertility, fecundity, lamb survival, and lambs weaned) with variables that graziers can change or modify (strain of Merino, day or month of exposure of ewes to rams, ram effect or teasing, length of the mating period, ram percentage, days between weaning and next mating, stocking density and flock size at lambing, ewe liveweight, and condition) are reported in this paper, the third in a series. Small differences were observed between medium and strong-wool South Australian Merino strains for reproductive traits. Choosing the time of year that ewes are exposed to rams, between late spring to autumn, may result in reduced ovulation rate during early summer (December) giving a potentially smaller net reproductive efficiency (lambs weaned). The ram effect or teasing, used by about 50% of graziers to synchronise lambing, could be effectively employed to the end of January. The technique was not reproductively advantageous when compared with flocks that were not teased. The percentage of rams mated to ewes varied widely (approximately 1-3%) and did not alter flock fertility, suggesting that a substantial proportion of graziers could safely reduce the number of rams purchased. A positive relationship between incidence of estrus during the first 14 d of the cycle and the number of days from weaning to next mating and a negative relationship of returns to service with the same variable indicates that managers should consider increasing the time allowed for recovery of liveweight and body condition by adjusting age at weaning, length of the mating period, or both. Lamb survival was curvilinearly related to flock size and not stocking intensity, with the optimum size at about 400 ewes. The number of lambs weaned per 100 ewes exposed to rams increased by 1.0 kg(-1) increase in liveweight at mating. We concluded that the major factor controlling net reproductive efficiency is nutritional in origin through its effects on ewe liveweight and condition, and is a factor that can be largely manipulated through management.     

The influence of azaperone treatment at weaning on reproductive performance of sows: altering effects of season and parity

Azaperone treatment can control aggression and decrease stress due to weaning, re-grouping and hierarchical fighting of gilts and sows. However, the effects of this butyrophenone neuroleptic and sedative administered at weaning on pig reproductive function are poorly characterized. In this year-long study, a total of 619 cross-bred sows (Polish Large White×Polish Landrace) kept on a commercial farm received an i.m. injection of azaperone (Stresnil®; 2 mg/kg BW) just before weaning and were artificially inseminated during the ensuing estrus with 3×10⁹ spermatozoa per dose of an inseminate; 1180 sows served as untreated controls. Immediately after weaning, the sows were moved to four pens of seven to nine animals each. A teaser boar was used twice daily to check for estrus and sows were bred at heat detection. Subsequently, all sows stayed in individual stalls until pregnancy testing on day 30 post-artificial insemination and were then re-grouped until farrowing. The proportion of pigs that were in estrus within 6 days post-weaning was significantly lower in azaperone-treated groups of animals than in controls (71.4% v. 84.2%). Overall, the azaperone-treated sows had a significantly longer weaning-to-estrus interval (WEI; 8.7±10.1 v. 6.3±8.1 days; mean±SD) and a significantly larger litter size (LS: 11.8±3.0 v.11.3±3.2; azaperone-treated v. control sows). Treatment of the winter-farrowing sows was associated with increased LS (12.8±2.6 and 11.3±3.1 piglets/sow, respectively; P<0.05) and longer (P<0.05) weaning-to-effective-service intervals (11.7±19.3 and 8.4±12.3 days, respectively) as well as farrowing intervals (155.7±19.7 and 152.2±16.1 days, respectively) compared with untreated controls. In the summer months, significantly longer WEIs (12.1±21.0 v. 8.4±16.9 days) were accompanied by a significant decline in LS only in azaperone-treated sows that were inseminated within 6 days post-weaning (10.8±2.9 v. 11.5±3.3 piglets/sow; azaperone-treated v. controls). Azaperone-treated second parity sows had greater LS (P<0.001) along with prolonged WEIs (P<0.05) in comparison to their respective controls, regardless of the timing of estrus. An application of azaperone at weaning increased the annual piglet productivity of winter-farrowing animals and of second parity sows but depressed it significantly in summer. The extra cost and labor due to delayed onset of estrus may cancel out any reproductive benefits of azaperone treatment.     

Genetic and phenotypic parameters of age at first mating, litter size and animal size in Finnish mink

Mink skin size in Finland, as well as in other countries, has increased considerably during last decade. However, there are signs that selection for large body size has a negative impact on litter size (LS) and also for survival of kits. Therefore, it is important to study the genetic relationships among fertility traits and animal size (AS). The variance components for age at first mating (AFM) and first three parity LS and AS were estimated using multi-trait restricted maximum likelihood animal model. Data included 82 945 animals born during 1990 to 2004, originating from nine farms. Heritability estimates for the fertility traits were from 0.10 to 0.15. For AS, heritability was estimated to be 0.18. Genetic correlation between AS and all fertility traits was estimated to be negative (varying from -0.004 to -0.38). It is important to recognize this antagonistic relationship and include the reproductive traits into breeding goals to maintain good reproductive performance when selecting for increased body size and hence larger pelts in fur animals. Genetic correlations between the traits should be accounted in breeding value evaluations by using a multi-trait model. Including AFM into breeding value estimation would also improve the accuracy of breeding value estimation for fertility, because females missing the first LS still have record on AFM.     

Factors influencing lamb survival in a high fecundity Booroola Merino x South Australian Merino flock

The effects of year of lambing, age of ewe and litter size on lamb survival and birthweight, and the effects of ewe mating weight and pregnancy wastage (ovulation rate minus litter size) on birthweight were examined in Booroola Merino x South Australian Merino ewes. Year of lambing, litter size and their interaction were significant (P<0.001) sources of variation for lamb survival. When birthweight was included as a linear and quadratic covariate for lamb survival, year of lambing and litter size and their interaction remained as statistically significant sources of variation. Year of lambing, litter size and pregnancy wastage contributed significantly (P<0.05) to variation in birthweight. Ewe liveweight at mating was not an important source of variation (P>0.05). Birthweight was significantly (P<0.05) reduced with an increase in pregnancy wastage. Improvement of birthweight of multiple birth lambs has some potential for increasing lamb survival. Other factors influencing lamb survival (year of lambing, litter size, pregnancy wastage) require further study so that strategies for reducing lamb loss in high fecundity Merino flocks can be developed.     

Seasonal reproductive cycle of the Galápagos tortoise (Geochelone nigra) in captivity

The reproductive physiology of nine Galápagos tortoises (Geochelone nigra) was studied from February 1988 to May 1989. The study encompassed the annual reproductive cycle to include complete mating and nesting sequences. Male (n = 4) and female (n = 5) seasonal reproductive changes were determined throughout the study with endocrine analysis and ultrasonographic examinations. Males displayed a prenuptial rise in serum testosterone (x― ±SE = 6.62 ± 0.92 ng/ml in August) during which gonadal maturation and spermatogenesis are thought to occur. The male reproductive cycle appears consistent with the prenuptial spermatogenic pattern exhibited by other tropical turtles. In the females, testosterone rose during the mating period (x― ± SE = 499.3 ± 124.6 pg/ml in October) prior to ovulation and is probably related to receptivity in the females. Progesterone was more variable, but also peaked during the mating period (x― ± SE = 1,017.2 ± 220.6 pg/ml in October) and appears related to ovulation. Estradiol rose several months prior to mating (x― ± SE = 75.5 ± 11.9 pg/ml in July) and was correlated with increased serum calcium levels. This increase in estradiol is thought to stimulate vitellogenesis several months prior to mating. Nesting occurred from November 1988 to April 1989, during which six clutches were laid. Clutch size ranged from eight to 17 eggs. Both male and female Galápagos tortoises display seasonal physiological changes that function to regulate annual reproductive patterns. Zoo Biol 17:505–517, 1998. © 1998 Wiley-Liss, Inc.     

Population dynamics and social organization of sambar (Rusa unicolor unicolor) in Horton Plains National Park,Sri Lanka

We estimated the population density and investigated the social organization of sambar (Rusa unicolor unicolor) in Horton Plains National Park (HPNP), Sri Lanka. Distance sampling was conducted along six strip transects every month for a period over 3 years (2018–2020) to estimate the density of the sambar population in grasslands of HPNP (9.4 km²), while the antler stage of males and the behavior of individuals were recorded to describe the population's reproductive stage and hence the social organization. Population density estimates showed relative stability over the 3 years and varied over the seasons but with consistent peaks from year to year with the highest population densities recorded in November–December (212.93 ± 25.38 animals/km² in 2018, 187.91 ± 28.51 in 2019, and 179.76 ± 31.85 in 2020). The highest percentage of males in hard antlers was observed from November through January, while the percentage of antlers cast sambar peaked from March to April each year. Hinds were observed with newborn calves throughout the year, but the highest number of newborn calves were recorded from July to August each year, while the number of calves counted each year varied from 210 to 267 individuals. The mean group size was variable throughout each year with the largest groups recorded from September to December (up to 52), the period accompanied by the most observations of mating and sparring behavior. Although on a tropical island, HPNP is situated on a rolling plateau landscape in the highlands, where sambar showed a degree of reproductive seasonality somewhat similar to temperate cervid species.     

Genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population

The genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population were estimated by applying the Average Information Restricted Maximum Likelihood method to an animal model. Data from a flock supported by the Programa de Melhoramento Genético de Caprinos e Ovinos de Corte (GENECOC) were used. The traits studied included birth weight (BW), weaning weight (WW), slaughter weight (SW), yearling weight (YW), weight gain from birth to weaning (GBW), weight gain from weaning to slaughter (GWS), weight gain from weaning to yearling (GWY), age at first lambing (AFL), lambing interval (LI), gestation length (GL), lambing date (LD - number of days between the start of breeding season and lambing), litter weight at birth (LWB) and litter weight at weaning (LWW). The direct heritabilities were 0.35, 0.81, 0.65, 0.49, 0.20, 0.15 and 0.39 for BW, WW, SW, YW, GBW, GWS and GWY, respectively, and 0.04, 0.06, 0.10, 0.05, 0.15 and 0.11 for AFL, LI, GL, LD, LWB and LWW, respectively. Positive genetic correlations were observed among body weights. In contrast, there was a negative genetic correlation between GBW and GWS (-0.49) and GBW and GWY (-0.56). Positive genetic correlations were observed between AFL and LI, LI and GL, and LWB and LWW. These results indicate a strong maternal influence in this herd and the presence of sufficient genetic variation to allow mass selection for growth traits. Additive effects were of little importance for reproductive traits, and other strategies are necessary to improve the performance of these animals.     

Effects of suckling mode on endocrine control of reproductive activity resumption in Texel ewes lambing in July or November

To study the effects of the overlapping of seasonal and lactation anestrus and the influence of the suckling mode on the resumption of reproductive activity in Texel ewes, two experiments were carried out after the July and November lambings. The frequency and the duration of suckling decreased with the age of the lambs, and the suckling intensity in the lambs that were allowed to suck unrestrictedly was three times higher than in lambs restricted to sucking three times a day. The overlapping of seasonal anestrus and lactation delayed the resumption of ovarian and estrus activity, but no difference was observed between dams suckling single lambs and twins. The resumption of ovarian and estrus activity was much earlier after the November lambing than after the July lambing. Weaning after the November lambing shortened the interval between parturition to first estrus but not to the first luteal function. The reduction of suckling intensity by suckling management had no effect on the resumption of ovarian and estrus activity. In early postpartum, suckling inhibited the luteinizing hormone (LH) pulsatile secretion and consequently the first LH discharge. However, the earlier restoration of gonadotropin stimulation in dry ewes was not immediately followed by ovarian activity. The suckling inhibition may be due to a temporary disturbance in hormonal balance, the rise in prolactin (PRL) and cortisol secretions. Plasma estradiol 17beta (E2) concentrations were higher in dry than in suckling ewes in early postpartum. Follicle stimulating hormone (FSH) secretion was not involved in the process of delaying the resumption of reproductive activity after lambing.     

Fertility in South Australian commercial Merino flocks: relationships between reproductive traits and environmental cues

High levels of reproductive loss have been reported in commercial Merino flocks (n=68) from the cereal/livestock and high rainfall zones in South Australia (Kleemann DO, Walker SK. Fertility in South Australian commercial Merino flocks: sources of reproductive wastage. Theriogenology 2005;63:2075-88). Relationships between reproductive traits (estrus, ovulation, fertility, fecundity, lamb survival) and environmental end points (liveweight, condition score, temperature at mating, chill index at lambing) are reported in this paper. They were analysed within season of mating (October to December; January to March) and age of ewe (maiden as 1.5-year-old, mature as older). Incidence of estrus was positively related (P<0.05) to condition score in the October to November interval. Return rate to service was positively (P<0.05) influenced and fertility was negatively (P<0.05) influenced by the number of days ambient temperatures were > or =32.0 degrees C during mating, indicating that high ambient temperatures may reduce embryo survival. Liveweight and, to a lesser extent, condition score, accounted for significant proportions of variation associated with ovulation rate (39.3 and 12.7%, respectively). Ovulations per 100 ewes increased by 1.8 per kg increase in liveweight over all flocks. Ovulatory response to liveweight increased (P<0.01) from the October to December to the January to March period of mating (1.5 versus 3.4 ovulations per kg, respectively). Overall, a flock's fertility and fecundity increased by 0.27 and 1.42% per kg increase in liveweight, respectively. Reproductive wastage from partial failure of multiple ovulations (PFMO) was positively related to liveweight (P<0.01) and ovulation rate (P<0.001). Survival of single lambs was positively and curvilinearly related to maternal liveweight and condition score measured in late pregnancy (P<0.05). Linear relationship of these variables for twin lamb survival was significant for condition score only. Single and twin lamb survival were also positively related to liveweight and condition score at mating (P<0.05). We concluded that nutritional cues have a major impact on reproductive traits in commercial Merino flocks in South Australia; it sets the potential number of lambs (ovulation rate) and influences survival of lambs as early as at mating. Indications are that high ambient temperatures may influence embryo survival. It is recommended that future research efforts focus on: (a) prenatal nutritional influences on the physiology of mother-offspring behaviours at birth; and (b) possible peri-conceptional dietary factors controlling embryo loss resulting from partial failure of twin ovulations, to improve reproductive efficiency in the Merino.     

Behavioral plasticity and G × E of reproductive tactics in Nicrophorus vespilloides burying beetles

Phenotypic plasticity is important in the evolution of traits and facilitates adaptation to rapid environmental changes. However, variation in plasticity at the individual level, and the heritable basis underlying this plasticity is rarely quantified for behavioral traits. Alternative behavioral reproductive tactics are key components of mating systems but are not often considered within a phenotypic plasticity framework (i.e., as reaction norms). Here, using lines artificially selected for repeated mating rate, we test for genetic (G × E) sources of variation in reproductive behavior of male Nicrophorus vespilloides burying beetles (including signaling behavior), as well as the role of individual body size, in responsiveness to changes in social environment. The results show that body size influences the response of individuals’ signaling behavior to changes in the social environment. Moreover, there was G × E underlying the responses of males to variation in the quality of social environment experienced (relative size of focal male compared to his rival). This shows that individual variation in plasticity and social sensitivity of signaling behavior can evolve in response to selection on investment in mating behavior, with males selected for high mating investment having greater social sensitivity.     

Genetic basis of variation in reproductive performance. I. Ewe lambs treated with fluorogestone acetate and PMSG in a controlled environment

This study involved records on fertility, prolificacy, multiple birth, fecundity, body weight and age at breeding of 2380 ewe lambs from 432 sires of three synthetic strains developed at the Animal Research Centre, Ottawa, Canada. Ewes were divided into two equal flocks which were bred to lamb alternately at 4-month intervals under an 8-month breeding cycle. Lambs were housed indoors, in a controlled environment, on expanded metal mesh floors in windowless barns and were bred in January, May and September at the end of a period of short days. Ewes that lambed were generally heavier and slightly older at breeding as were ewes that lambed to mating at the synchronised estrus. Though not significant, trends demonstrating seasonal differences in the heritabilities of all reproductive traits were observed. Paternal half-sib estimates showed fertility, prolificacy, multiple births and fecundity were non-heritable in ewes lambing to matings at the synchronized estrus. Heritability estimates for prolificacy and multiple birth were 0.22 and 0.13, respectively, in ewes lambing to matings at the synchronized plus follow-up estrus, suggesting that slow genetic progress can be achieved in these traits from selection. Heritability estimates ranged from 0.03 to 0.22 for body weight and from 0.28 to 0.54 for age at breeding. Ewes that lambed showed lower values than all ewes exposed. Phenotypic correlations between reproductive traits and either body weight or age at breeding were low and ranged from 0.04 to 0.09. There were higher estimates of genetic correlation of prolificacy (and multiple birth) with either body weight or age at breeding in ewes lambing to matings at the combined estruses. Indirect selection of ewe lambs based on age and body weight at breeding may be an effective alternative to direct selection for genetic improvement of prolificacy and multiple birth.     

Reproductive,behavioral, and endocrine characteristics of the Dall's sheep (Ovis dalli dalli)

Failed interspecific embryo transfer between Dall's sheep (Ovis dalli dalli) and domestic ewes (Ovis aries), and a paucity of physiological data available for the Dall's sheep, provided incentive for developing a reproductive database in Dall's sheep. Urine samples were collected on a regular basis from a captive herd of Dall's sheep during the breeding to lambing interval over a 3 year period. To provide comparative endocrine data during pregnancy, samples also were collected during a single gestation period from five Suffolk ewes. All urine samples were analyzed for pregnanediol-3-glucuronide (PdG) and estrone conjugates (EC). Behavioral observations from Dall's sheep were made each year during the rut and lambing periods to calculate estrous cycle and gestation lengths. Placentas from Dall's sheep (n = 20) and Suffolk ewes (n = 10) were collected, the total number of cotyledons counted, and the length, width, area, and weight of eight cotyledons/horn from each placenta calculated. Endocrine and behavioral results indicated that the Dall's sheep is seasonally polyestrous and monovulatory, with a mean estrous cycle length of 18.2 ± 0.3 days, a mean luteal phase of 11.8 ± 0.5 days, and an average gestation length of 171.6 ± 0.9 days. While hormonal patterns for pregnancy generally were similar between the two species, there was a pronounced difference in the magnitude of hormone concentrations, particularly PdG, and an absence of a marked preparturition EC rise in domestic sheep. Cotyledon numbers, weight, and area were smaller (P < 0.05) in the Dall's sheep, compared to Suffolk ewes. These data suggest that unsuccessful interspecies embryo transfer attempts may have been due to failed fetal/maternal communications resulting from hormonal and/or placental differences. © 1996 Wiley-Liss, Inc.     

Estimates of genetic parameters and genetic trends for growth,reproduction, milk production and milk composition traits of Awassi sheep

Genetic parameters and genetic trends for growth, reproduction, milk production and composition traits were estimated for Syrian (S) and Turkish (T) Awassi sheep and their crosses maintained at the International Center for Agricultural Research in the Dry Areas Tal Hadya station, Aleppo, Syria (now in Terbol station in Lebanon). The data were spread over 9 years. The individual breed additive effects of T were positive and significant (P<0.05) for birth weight (BW). However, the values for weaning weight (WW) and pre-weaning weight gain (WG) were negative, even though they were significant (P<0.05). These estimates were positive and significant (P<0.05) for all reproduction and milk traits, except for litter weight at birth (LWB). The additive contributions of T were 60.72±0.94 days, 1.643±0.359 kg, 13.09±0.89 days, 16.13±0.89 kg, 1.12±0.44 kg, 0.71±0.26 kg, 2.80±0.72 kg and 0.83±0.32 kg for lambing interval (LI), litter weight at weaning (LWW), lactation length, milk yield, fat yield, protein yield, total solids yield and lactose yield, respectively. The heterosis effects, both individual and maternal, were non-significant (P>0.05) for most growth traits. Crossing of T with S, however, resulted in desirable and significant (P<0.05) individual heterosis effects for all the reproduction, milk production and constituent yields. The heritability (h²) estimates, both direct and maternal, were low for BW, WW, WG and all reproductive traits indicating major influence of environmental factors, whereas milk yield and composition had medium values. Birth weight had moderate genetic correlation with WW and WG. The genetic correlation between WW and WG was high (0.724±0.951). Lambing interval had large negative genetic correlation with LWB and LWW. However, LI had medium significant correlations with all the milk production and composition traits. Larger litter weights at birth had high and negative influence on milk yield of the dam and its constituents. Genetic changes over years for all traits were non-significant. The lack of genetic change in the studied traits calls for systematic and organized selection scheme.     

Risk factors associated with lambing traits

The objective of this study was to establish the risk factors associated with both lambing difficulty and lamb mortality in the Irish sheep multibreed population. A total of 135 470 lambing events from 42 675 ewes in 839 Irish crossbred and purebred flocks were available. Risk factors associated with producer-scored ewe lambing difficulty score (scale of one (no difficulty) to four (severe difficulty)) were determined using linear mixed models. Risk factors associated with the logit of the probability of lamb mortality at birth (i.e. binary trait) were determined using generalised estimating equations. For each dependent variable, a series of simple regression models were developed as well as a multiple regression model. In the simple regression models, greater lambing difficulty was associated with quadruplet bearing, younger ewes, of terminal breed origin, lambing in February; for example, first parity ewes experienced greater (P<0.001) lambing difficulty (1.56±0.02) than older ewes. The association between lambing difficulty and all factors persisted in the multiple regression model, and the trend in fixed effects level solutions did not differ from the trend observed in the simple regression models. In the simple regression analyses, a greater odds of lamb mortality was associated with male lambs (1.31 times more likely of death than females), lambs of very light (2 to 3 kg) and very heavy (>7.0 kg) birth weights, quadruplet born lambs and lambs that experienced a more difficult lambing (predicted probability of death for lambs that required severe and veterinary assistance of 0.15 and 0.32, respectively); lambs from dual-purpose breeds and born to younger ewes were also at greater risk of mortality. In the multiple regression model, the association between ewe parity, age at first lambing, year of lambing and lamb mortality no longer persisted. The trend in solutions of the levels of each fixed effect that remained associated with lamb mortality in the multiple regression model, did not differ from the trends observed in the simple regression models although the differential in relative risk between the different lambing difficulty scores was greater in the multiple regression model. Results from this study show that many common flock- and animal-level factors are associated with both lambing difficulty and lamb mortality and management of different risk category groups (e.g. scanned litter sizes, ewe age groups) can be used to appropriately manage the flock at lambing to reduce their incidence.     

Estimation of (co)variance components,genetic parameters,and genetic trends of growth traits in community-based breeding programs of Bonga sheep

Community-based sheep breeding programs (CBBPs) have been adopted strategically to improve Bonga sheep, the most popular sheep breed in Ethiopia. The present study was undertaken to estimate genetic parameters and genetic trends for growth traits and inbreeding levels in each Bonga sheep CBBP. Data pertaining to growth traits, spanning a period of seven years (2012–2017), were collected from 14 Bonga sheep CBBPs. Data were analyzed using the General Linear Model procedure of SAS to study the performance of the breed over the years. The genetic parameters were estimated by univariate and multivariate animal model using restricted maximum likelihood method of WOMBAT software. The genetic trends were estimated by the regression of the average breeding values of the animals on the year of birth. The overall least square means ± SE of BW (kg) were 3.10 ± 0.010, 16.1 ± 0.07, 24.7 ± 0.20, 30.4 ± 0.40 and 34.0 ± 0.84 for birth weight (BWT), weaning weight (WWT), six-month weight (SMWT), nine-month weight (NMWT) and yearling weight (YWT), respectively. Direct heritability estimates from selected models were 0.56 ± 0.030, 0.36 ± 0.030, 0.22 ± 0.040, 0.17 ± 0.070 and 0.13 ± 0.150 for BWT, WWT, SMWT, NMWT and YWT, respectively. Six-month weight was the selection trait and presented positive trends for 10 CBBPs, and negative trends for four CBBPs. Moderate to high heritability estimates and positive genetic trends indicated scope for further improvement of BW. Additionally, the positive and high correlation between BW traits indicated that selection for just one trait would also improve the other traits through correlated responses.     

Estimates of phenotypic and genetic parameters for reproductive traits in Kermani sheep

Phenotypic and genetic parameter estimates for reproductive traits in Kermani sheep were estimated using reproductive records of 860 ewes. Data were collected during 1995–2007 at the experimental breeding station of Kermani sheep, south-east of Iran. Investigated traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB) and litter mean weight per lamb weaned (LMWLW) as basic traits, total litter weight at birth (TLWB) and total litter weight at weaning (TLWW) as composite traits. Quantitative genetic analyses were performed applying restricted maximum likelihood (REML) procedure under repeatability models. Ewe age had significant effect on LMWLB, LMWLW, TLWB and TLWW (P < 0.01). However, LSB and LSW were not affected by age of the ewe. All the studied traits were significantly affected by lambing year (P < 0.01). Direct heritability estimates for LSB, LSW, LMWLB, LMWLW, TLWB and TLWW were 0.01, 0.03, 0.13, 0.22, 0.06 and 0.18, respectively, while the corresponding repeatabilities were 0.08, 0.10, 0.17, 0.29, 0.09 and 0.23, respectively. Genetic correlation estimates between the investigated traits ranged from ?0.94 for LSB–LMWLB and LSW–LMWLW to 0.99 for LSB–TLWW. Phenotypic and environmental correlations were generally lower than those of genetic correlations. Phenotypic correlations ranged from ?0.34 for LSB–LMWLB to 0.58 for TLWB-TLWW. Environmental correlations ranged from ?0.33 for LSB–LMWLB and LSW–LMWLB to 0.33 for LMWLB–LMWLW. The results suggested that selection based on TLWW could be more effective than the other traits on improvement of reproductive performance in Kermani ewes.     

Seasonal reproductive costs contribute to reduced survival of female greater sage‐grouse

Tradeoffs among demographic traits are a central component of life history theory. We investigated tradeoffs between reproductive effort and survival in female greater sage‐grouse breeding in the American Great Basin, while also considering reproductive heterogeneity by examining covariance among current and future reproductive success. We analyzed survival and reproductive histories from 328 individual female greater sage‐grouse captured between 2003 and 2011, and examined the effect of reproductive effort on survival and future reproduction. Monthly survival of females was variable within years, and this within‐year variation was associated with distinct biological seasons. Monthly survival was greatest during the winter (November–March; Φ_W= 0.99 ± 0.001 SE), and summer (June–July; Φ_S= 0.98 ± 0.01 SE), and lower during nesting (April–May; Φ_N= 0.93 ± 0.02 SE) and fall (August–October; Φ_F= 0.92 ± 0.02 SE). Successful reproduction was associated with reduced monthly survival during summer and fall, and this effect was greatest during fall. Females that successfully fledged chicks had lower annual survival (0.47 ± 0.05 SE) than females who were not successful (0.64 ± 0.04 SE). Annual survival did not vary across years, consistent with a slow‐paced life history strategy in greater sage‐grouse. In contrast, reproductive success varied widely, and was positively correlated with annual rainfall. We found evidence for heterogeneity among females with respect to reproductive success; compared with unsuccessful females, females that raised a brood successfully in year t were more than twice as likely to be successful in year t+ 1. Female greater sage‐grouse incur costs to survival associated with reproduction, however, variation in quality among females may override costs to subsequent reproductive output.     

Geographical variation in reproductive traits and trade‐offs between size and number of eggs in the king ratsnake,Elaphe carinata

We collected gravid king ratsnakes (Elaphe carinata) from three geographically separated populations in Chenzhou (CZ), Lishui (LS) and Dinghai (DH) of China to study the geographical variation in female reproductive traits and trade‐offs between the size and number of eggs. Not all reproductive traits varied among the three populations. Of the traits examined, five (egg‐laying date, post‐oviposition body mass, clutch size, egg mass and egg width) differed among the three populations. The egg‐laying date, ranging from late June to early August, varied among populations in a geographically continuous trend, with females at the most northern latitude (DH) laying eggs latest, and females at the most southern latitude (CZ) laying eggs earliest. Such a trend was less evident or even absent in the other traits that differed among the three populations. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar to each other in most traits examined. LS females were distinguished from CZ and DH females by the fact that they laid a greater number of eggs, but these were smaller. The egg size–number trade‐off was evident in each of the three populations and, at a given level of relative fecundity, egg mass was significantly greater in the DH population than in the LS population. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 701–709.     

Effects of multiple mating on the fecundity of an invasive pest (Octodonta nipae): the existence of an intermediate optimal female mating rate

Multiple mating is found in many insect taxa where both of the sexes can mate more than once. For males, this leads to the advantage of increasing their paternity by fertilizing more females. However, there is a trade‐off of resource allocation between reproduction and other life‐history characters. In the present study, the impact of increased mating rate on reproductive fitness of the invasive nipa palm hispid beetle Octodonta nipae Maulik (Coleoptera: Chrysomelidae) is investigated. A series of mating frequencies (i.e. 1, 5, 10, 15, 20 times) is selected from video frame playback, ranking from the minimum to maximum mating rate observed under laboratory conditions over a given time period. Fecundity parameters such as lifetime egg production, egg‐hatching rate, effective oviposition period and longevity are investigated for the evaluation of reproductive efficiency. For female O. nipae, increased fecundity is correlated with the mating frequency. Females mating 15 times lay the largest number of eggs (138.82 ± 6.87) and have a hatching rate of 47.43 ± 4.08%. After mating 20 times, females suffer significant declines in oviposition (90.31 ± 8.38 eggs) and egg‐hatching rate (34.16 ± 4.93%). Moreover, the population growth rate reaches a maximum in the females that mate 15 times. The results show that multiple matings in O. nipae have an intermediate optimal range within which female reproductive success is enhanced, providing empirical evidence for the existence of a trade‐off between costs and benefits during copulation based on resource allocation.     

Evolutionary consequences of ecological factors: pollinator reliability predicts mating‐system traits of a perennial plant

The reproductive‐assurance hypothesis predicts that mating‐system traits will evolve towards increased autonomous self‐pollination in plant populations experiencing unreliable pollinator service. We tested this long‐standing hypothesis by assessing geographic covariation among pollinator reliability, outcrossing rates, heterozygosity and relevant floral traits across populations of Dalechampia scandens in Costa Rica. Mean outcrossing rates ranged from 0.16 to 0.49 across four populations, and covaried with the average rates of pollen arrival on stigmas, a measure of pollinator reliability. Across populations, genetically based differences in herkogamy (anther–stigma distance) were associated with variation in stigmatic pollen loads, outcrossing rates and heterozygosity. These observations are consistent with the hypothesis that, when pollinators are unreliable, floral traits promoting autonomous selfing evolve as a mechanism of reproductive assurance. Extensive covariation between floral traits and mating system among closely related populations further suggests that floral traits influencing mating systems track variation in adaptive optima generated by variation in pollinator reliability.