Medical genetic study of the population of Turkmenia. VI. An analysis of the genetic component of fertility dispersion in the population of Nokhor

The index of the total opportunity for selection (the Crow index) and the genetic part of total variance in progeny size was studied in small Turkmenian isolated population "Nochur". The average number of children per family in families that had completed their reproductive period was 6.84, the variance being 12.31. The index of total opportunity for selection was computed by the standard method of J. Crow: Jm = 0.313, Jf = 0.454, Jtot = 0.909. Some correlation coefficients of the progeny size were calculated. The sister-sister correlation coefficient was significantly distinguished from 0 and was equal to +0.22. Thus, the genetic part of total variance of the progeny size is 0.4-0.5. It is essential for understanding of the Jf estimation.     

Population genetics of the inhabitants of Northern European USSR. I. Data on the structure of 6 villages in Archangel Oblast]

The paper deals with two demographic characteristics of 6 villages in the Archangelsk Region of the RSFSR (river Peosa region) significant from the genetical standpoint. These data were obtained by means of the examination of 843 persons (75,07% of the total number of inhabitants) and of the analysis of complete list of inhabitants permanently living in the villages studied. The proportion of the reproductivity age class was 28.94%, the numbers of men and woman among them being about equal. The average number of children per family in families that have already completed their reproductive period was 3.87, the variance being 4.51 (the data obtained on the basis of examination of over 90 families). The average age of marriage was established to be about 24 years, the duration of each generation being about 32 years. The average index of endogamy per village was observed to be 58.40%, the contribution of the gametes of the preceding generation per village being 72.86%. The migrational influx of gametes from other localities per total of 6 villages was 2.52%. It was shown by the comparison of the character of migrations with mathematical models that the matrix migrational model is the most adequate one.     

Genetic analysis of the predisposition to uterine myoma. Prevalence and morbidity

Prevalence of uterine myoma (MU) was estimated in several Moscow districts. The overall average estimate of the MU prevalence is 2.45% among women of all groups. The prevalence MU estimates increase with the age, its maximum value reaching 8.31% at the age of 50 years. The morbidity risk estimates increased with the age as well, the maximum value being 2.98% at the age of 40-44 years. The value of "cumulative" morbidity risks, i. e. the probability to be affected, is 9.74% for a population living long enough, this value being based on the age-specific estimates of morbidity risks. Taking into consideration the autopsy data, indicating that frequency of MU, including small myomatous nodes, is 20%, the conclusion is made that MU is manifested by clinically expressed disturbances (urging a woman to address to a doctor) in 50% of cases only. Epidemiological data obtained are to be used later for genetic analysis of familial data on MU.     

Study of preantral follicle population in situ and after mechanical isolation from caprine ovaries at different reproductive stages.

The purposes of this study were to estimate the population of caprine preantral follicles, and to evaluate quantitatively and qualitatively the efficiency of a specific mechanical method for the isolation of preantral follicles from mixed breed goats at different reproductive stages. On average, 37,646+/-4277 preantral follicles were present in goat ovaries, and 13,631+/-2399 preantral follicles were obtained after isolation. The number of preantral follicles isolated or in situ was not significantly affected by the reproductive stage. The mean recovery rate per ovary ([number of isolated follicles/number of in situ follicles] x 100) of isolated follicles was 36.2%. The distribution of follicles in situ was 67.8% primordial, 25.8% primary and 6.4% secondary; the respective distribution after isolation was 93.8%, 5.2% and 1.0%. In this study, many polyovular follicles were also observed, mainly in prepubertal goat ovaries. Histological analysis showed that few preantral follicles were atretic in situ (4.83%+/-0.35) or after the isolation procedure (4.67%+/-0.65) in the three reproductive stages. The percentage of atretic follicles was not affected either by the mechanical method or by the reproductive stage. It is concluded that a large number of preantral follicles can be successfully isolated mechanically, with a high recovery rate and a low rate of follicular atresia, irrespective of the reproductive stage of the caprine female.     

不同年龄段大连群体菲律宾蛤仔EST-SSR多样性

为查明年龄结构对菲律宾蛤仔同一群体内遗传多样的影响,采用14个SSR分子标记对大连石河不同年龄段的野生蛤仔进行了检测。结果表明:不同年龄段(1龄-Age1、2龄-Age2、3龄-Age3)蛤仔均维持着较高的遗传多样性。根据POPGENE 1.31和SPSS16.0统计分析显示,位点Rp-11、Rp-12、Rp-19对3个年龄段蛤仔的等位基因数差异极显著(P<0.01);位点Rp-20、Rp-24、Rp-27、Rp-30对其差异显著(P<0.05);剩余7个位点表现为差异不显著(P>0.05)。在平均水平上,每位点等位基因数目Na为4.3095,有效等位基因数目Ne为2.3729,多态位点百分数P(%)为14。观察杂合度和期望杂合度都比较高,观察杂合度平均为Ho=0.2335,期望杂合度平均为He=0.5140。而且,Ne和He随年龄的变化表现出Age2>Age3>Age1的趋势。各年龄段蛤仔——Age1、Age2、Age3的平均观察杂合度(Ho)和平均期望杂合度(He)分别为0.2357、0.2546、0.2159和0.4951、0.5286、0.5184。Age2的遗传多样性指数高于Age1及Age3,遗传分化相对较低。其中,Age1与Age3蛤仔遗传距离最小,D为0.0195,即变异很小;而Age1与Age2遗传距离较大,D为0.0437,变化范围不大(0.0195—0.0437)。从遗传一致度的数值上看了3个年龄段蛤仔的遗传相似程度很大,平均为0.9655。Age1与Age3遗传相似程度高达0.9807,而Age1与Age2相似程度较小为0.9572。说明不同年龄段蛤仔相似程度非常高。根据不同年龄段蛤仔的遗传距离,采用UPGMA平均聚类方法对其进行聚类可知,Age3与Age1蛤仔间遗传距离较小,与Age2蛤仔差异较大。通过对等位基因频率进行卡方检验发现,随着年龄结构的变化,部分基因基因频率减小;同时随着年龄的增长,有部分等位基因得到了纯化。大连群体蛤仔总的遗传分化较低,其遗传分化指数Fst为0.0248(Fst<0.05),遗传分化系数为0.02,说明总的遗传变异中有2%来自于不同年龄段的蛤仔之间。遗传距离和遗传一致度均值分别为0.035和0.9655,基因流(Nm=9.8238)相对流畅,进一步表明年龄结构对蛤仔种群内遗传分化的影响较小。     

Estimation of effective population size for the long-lived darkblotched rockfish Sebastes crameri

We report the variance effective population size (Ne) in darkblotched rockfish (Sebastes crameri) utilizing the temporal method for overlapping generations, which requires a combination of age-specific demography and genetic information from cohorts. Following calculations of age-specific survival and reproductive success from fishery data, we genotyped a sample (n = 1087) comprised by 6 cohorts (from 1995 to 2000) across 7 microsatellite loci. Our Ne estimate (Ne) plus 95% confidence interval was (Ne) = 9157 [6495-12 215], showing that the breeding population number could be 3-4 orders of magnitude smaller than the census population size (N) = 24 376 210). Our estimates resemble closely those found for fishes with similar life history, suggesting that the small (Ne)/(N) ratio for S. crameri is most likely explained by a combination of high variance in reproductive success among individuals, genetic structure, and demographic perturbations such as historical fishing. Because small (Ne)/(N) ratios have been commonly associated with potential loss of genetic variation, our estimates need careful consideration in rockfish management and conservation.     

Evolutionary, behavioural and molecular ecology must meet to achieve long-term conservation goals

Founder populations in reintroduction programmes can experience a genetic bottleneck simply because of their small size. The influence of reproductive skew brought on by polygynous or polyandrous mating systems in these populations can exacerbate already difficult conservation genetic problems, such as inbreeding depression and loss of adaptive potential. Without an understanding of reproductive skew in a target species, and the effect it can have on genetic diversity retained over generations, long‐term conservation goals will be compromised. In this issue of Molecular Ecology, Miller et al. (2009a) test how founder group size and variance in male reproductive success influence the maintenance of genetic diversity following reintroduction on a long‐term scale. They evaluated genetic diversity in two wild populations of the iconic New Zealand tuatara ( Fig. 1 ), which differ greatly in population size and genetic diversity, and compared this to genetic diversity in multiple founder populations sourced from both populations. Population viability analysis on the maintenance of genetic diversity over 400 years (10 generations) demonstrated that while the loss of heterozygosity was low when compared with both source populations (1–14%), the greater the male reproductive skew, the greater the predicted losses of genetic diversity. Importantly however, the loss of genetic diversity was ameliorated after population size exceeded 250 animals, regardless of the level of reproductive skew. This study demonstrates that highly informed conservation decisions could be made when you build on a solid foundation of demographic, natural history and behavioural ecology data. These data, when informed by modern population and genetic analysis, mean that fundamental applied conservation questions (how many animals should make up a founder population?) can be answered accurately and with an eye to the long‐term consequences of management decisions.

Figure 1 Open in figure viewer PowerPoint Large adult male tuatara attacking a smaller male. Photo by Jeanine Refsnider.     

松嫩平原杂类草草甸阿尔泰狗哇花无性系种群构件年龄结构

阿尔泰狗哇花为根蘖型菊科多年生无性系草本植物.采用主根芽区的繁殖世代数划分分株和芽龄级的方法,研究了松嫩平原杂类草草甸阿尔泰狗哇花无性系种群不同构件的年龄结构.结果表明:分株构件和芽构件均由4个龄级组成.在孕蕾期,分株构件中1龄级占22.6%、2龄级44.8%、3龄级28.8%、4龄级3.8%,呈稳定型年龄结构.在乳熟期,生殖分株构件以2龄级比重最大,占45.6%,4龄级最小,占0.8%,为稳定型年龄结构;而营养分株构件以1龄级比重最大,占47.5%,4龄级最小,占1.1%,为增长型年龄结构.分株主根的生活年限最多为5年.不同生育期分株构件的生产力均以2龄级最高.在乳熟期,1龄级分株具有较大的生产潜力,4龄级分株的生产力已普遍减弱.芽库中潜在种群呈增长型年龄结构.     

Effective population size of steelhead trout: influence of variance in reproductive success, hatchery programs, and genetic compensation between life-history forms

The effective population size is influenced by many biological factors in natural populations. To evaluate their relative importance, we estimated the effective number of breeders per year (Nb) and effective population size per generation (Ne) in anadromous steelhead trout (Oncorhynchus mykiss) in the Hood River, Oregon (USA). Using demographic data and genetic parentage analysis on an almost complete sample of all adults that returned to the river over 15 years (>15,000 individuals), we estimated Nb for 13 run years and Ne for three entire generations. The results are as follows: (i) the ratio of Ne to the estimated census population size (N) was 0.17-0.40, with large variance in reproductive success among individuals being the primary cause of the reduction in Ne/N; (ii) fish from a traditional hatchery program (Htrad: nonlocal, multiple generations in a hatchery) had negative effects on Nb, not only by reducing mean reproductive success but also by increasing variance in reproductive success among breeding parents, whereas no sign of such effects was found in fish from supplementation hatchery programs (Hsupp: local, single generation in a hatchery); and (iii) Nb was relatively stable among run years, despite the widely fluctuating annual run sizes of anadromous adults. We found high levels of reproductive contribution of nonanadromous parents to anadromous offspring when anadromous run size is small, suggesting a genetic compensation between life-history forms (anadromous and nonanadromous). This is the first study showing that reproductive interaction between different life-history forms can buffer the genetic impact of fluctuating census size on Ne.     

Medico-genetical study of the Uzbekistan population. IX. Variability of hereditary pathology, territorial distribution of hereditary diseases and hereditary disease load in the population of the Urgut district of the Samarkand region

Medical-genetic study was carried out in the population of Samarkand province (the population size about 150 000). Hereditary pathology was ascertained among families with two or more affected members with chronic diseases. 110 families with 210 patients were registered. The most frequent were autosomal-recessive disorders (42 nozological forms). 15 nozological forms are probably "new" conditions in this province, because they were absent in our previous medical-genetic study of this province. A tendency to local accumulation of families with the same disorder in small populations was observed. The load of autosomal-recessive disorders comprised 2.2 X 10(-3) affected, that of autosomal-dominant disorders being 0.51 X 10(-3) and of X-linked disorders being 0.25 X 10(-3) males. The importance of assortative maitings in manifestation of rare autosomal-recessive genes in Uzbek population is discussed.     

The main trends in the palaeodemography of the 7th-18th century population of Latvia

The study represents palaeodemographic research of osteological material of 3304 individuals from the funds of the Anthropological Laboratory of the Institute of History of the University of Latvia in Riga, dating from the 7th to the 18th century AD. Compensated life expectancy at birth is varying between 20.3 and 22.2 years during the research period. Crude mortality has changed between 49.3 and 45% per hundred. In the early period (7th-13th century) there is a significant male prevalence (2.2-1.4); female life expectancy at the age of 20 is on average 6.6 years less than for males. This difference decreases to 5.4 years in the 13th-18th century. According to historical demography, female life span exceeded male only in the 2nd half of 19th century. The palaeodemographic data indicate that in the 7th-18th century, women in Latvia gave birth to a mean of 4-5 children (the figure includes childless women), of whom half, at most 2-2.5, reached reproductive age, on account of high child mortality. The net reproductive rate R0 (the number of descendants per individual of the parents' generation) varies between 1 and 1.25 in the study period. Concerning the completely excavated cemeteries of Lejasbiteni (7th-10h century) and Daudziesi (16th-17th century), it was possible to calculate the size and structure of the populations that had used these cemeteries. They were similar, having 45.3-49.9% of children up to an age of 14 and 24-28% individuals over the age of 30. According to historical demography, radical improvement of the demographic situation in Latvia began in the second half of the 19th century, when the process of demographic transition in Latvia started.     

Role of migration processes in shaping the marriage structure of the Moscow population. I. The age, place of birth and nationality of those entering marriage

A genetic-demographic study of the dynamics of the Moscow population marriage structure, with respect to the age of marriage, birthplace and nationality of newlyweds has been carried out by means of sample analysis of 1955 and 1980 marriage records; some other demographic and statistic data obtained during several years were also used. The mean age of marriage being practically constant, the proportion of newlyweds younger than 20 in the reproductive part of the Moscow population was shown to be considerably higher at the beginning of the XX century than at present. The number of couples married at the postreproductive age increased in 1980, as compared with 1955. The process of migration contributing to the genetic structure of subsequent Moscow generations has been characterized quantitatively and from the spatio-geographical point of view. High values (0.57 less than m less than 0.86) of the coefficient of migration to Moscow correspond to the period of non-controlled city population growth. As a result of administrative measures for regulation of the city population growth, the value of the coefficient of migration to Moscow decreased considerably by 1980, though still remained at a rather high level (m=0.40). The mean migration distance increased from 230 km, in the beginning of XIX century to 560 km in 1955 and 1100 in 1980. Especially great was the increase of genetic contribution from Eastern and Southern regions of the USSR. The variability of the national composition also increased. These changes in the geography of migration will cause the increasing reproduction of the entire country gene pool in Moscow as a panmixia center that may result in genetic originality of the Moscow population.     

Effects of inbreeding and other systematic effects on fertility of Black Forest Draught horses in Germany

Background

The Black Forest Draught horse (BFDH) is an endangered German coldblood breed with its origin in the area of the Black Forest in South Germany. In this retrospective study, the influence of the inbreeding coefficient on foaling rates was investigated using records from ten breeding seasons. Due to the small population size of BFDH, the level of inbreeding is increasing and may have an effect on foaling rates.The data of the present study included all coverings reported for 1024 BFDH mares in the years 2001–2009. These mares were covered by 32 BFDH stallions from the State Stud Marbach. Data from 4534 estrus cycles was used to calculate per cycle foaling rate (CFR). Pedigree data contained all studbook data up to the foundation of the breed as early as 1836. The level of inbreeding of the mare, stallion and expected foal along with other systematic effects on CFR were analysed using a generalized linear mixed model approach. Stallion was employed as a random effect. Systematic fixed effects were month of mating, mating type, age of the mare and stallion, reproductive status of the mare and stallion line of the mare. Inbreeding coefficients of the stallion, mare and expected foal were modelled as linear covariates.

Results

The average CFR was 40.9%. The mean inbreeding coefficients of the mares, stallions and expected foals were 7.46, 7.70 and 9.66%. Mating type, age of the mare, reproductive status of the mare and stallion line of the mare had a significant effect.

Conclusions

The results showed that the mating type, stallion line of the mare, sire, age and reproductive status of the mare exerted the largest influences on CFR in BFDH. Inbreeding coefficients of the stallion, mare and expected foal were not significantly related with CFR.

     

Hereditary diseases of nervous system in the population of Vladimir province

The first population genetic study of hereditary disorders of the nervous system (HDNS) in Vladimir oblast was carried out. A total of 1,622,900 subjects, including 1,306,200 from the urban and 316,700 from the rural population, were tested. The population examined was characterized by virtually homogenous ethnic structure, with Russians constituting 95.76%. Pooled prevalence of HDNS in Vladimir oblast corresponded to the average prevalence for other Russian populations. Substantial differences between urban and rural populations in respect of the population load of HDNS and its nosological structure were not observed. A total of 22 nosological forms of HDNS were revealed, including thirteen autosomal dominant (193 families with 272 affected individuals), seven autosomal recessive (59 families with 66 affected individuals), and two X-linked (15 families with 17 affected individuals) diseases. The composition of the HDNS spectrum "nucleus" in Vladimir oblast displayed a number of differences from that in the majority of other populations examined. The HDNS in different regions of the area tested were characterized by different prevalence and spectrum. The data obtained may constitute a basis for regional registration of HDNS in Vladimir oblast.     

Population genetics of Japanese monkeys: II. Blood protein polymorphisms and population structure

Genetic variability in individual troops of the Japanese macaque (Macaca fuscata fuscata) was quantified by the proportion of polymorphic loci and the average heterozygosity per individual from the results of starch-gel electrophoreses of blood proteins controlled by 32 independent genetic loci. The former averaged 9.2% and the latter 1.3%, the values being remarkably lower than those estimated for other animal populations. Geographical distribution of the genetic variations was not uniform in the whole species but the variants occurred only in limited areas. Assuming the selective neutrality of segregating alleles and the two-dimensional stepping-stone model of population structure, the genetic migration rate between the local demes per generation could be estimated to average less than inverse of average effective deme size. Here, the local deme is not a troop itself, but it consists of several troops tightly connected with each other by frequent exchanges of reproductive males. Analyses of correlation between geographic and genetic distances between troops revealed that the gene constitutions of two troops apart more than 100 km on an island could be regarded as practically independent of each other. These results suggest that the population structure of the Japanese macaque species has a tendency to split into a number of local subpopulations in which the effect of random genetic drift is prevailing.     

Genetic and phenotypic variation in reproductive traits of AI boars

The primary objective of this paper is to review our current understanding of phenotypic variation in reproductive traits of AI boars. The proportion of boars that cannot be trained for collection in commercial studs is low and differences among genetic lines are small. In contrast, there is a considerable variation in sperm production and significant differences are present among genotypes. The general pattern is for sperm numbers to increase rapidly between 9 and 13 months of age and then gradually reach a plateau. This initial period of enhanced production occurs over a longer period in some genetic lines, resulting in differences of 30 x 10(9) sperm cells or more per ejaculate. There also are genetic lines of boars that seem to have a high "heat tolerance". Decreases in sperm production during periods of high environmental temperatures average 5-7% in these lines, compared with 15-20% in others. Finally, there are boars currently being used in the industry that are capable of producing exceptional fertility results with low numbers of sperm. Unfortunately, several breeding practices common to swine AI make their routine identification difficult. Based on the phenotypic variation observed in modern terminal sire lines of AI boars, current prospects for influencing sperm production, boar fertility, and mounting behaviours through genetic selection are viewed as being good, moderate to low, and poor, respectively.     

The delineation of fertility strategies in a tribal population of India: the Koyas of Koraput District,Orissa

Demographic data collected for a tribal population of India, the Koyas of Koraput District, Orissa, were examined in light of 2 models of reproductive behavior associated with the economic value of children: the replacement effect and son survivorship motivation. Both models are united in the concept that infant/child mortality affects subsequent fertility. The database consists of retrospective fertility histories of Koya women who had completed their reproductive period. The total number was 260, with the total offspring numbering 1407. 2 distinct cohorts of women were formed for the purpose of analysis, separated only by the criterion of offspring survival: women who had experienced infant child mortality (129 women with 739 children); and women who completed their reproductive period without suffering offspring loss of this nature (132 women with 668 children). The cohort without child loss had a mean parity of 5.10, lower than the average parity of 5.73 recorded for the cohort whose reproductive histories included at least 1 infant/child death. Age specific marital fertility and birth interval analyses indicated that this differential was because of biological, not behavioral, factors. The age pattern of fertility of females suffering offspring mortality failed to demonstrate a high rate of childbearing in the later age intervals of the reproductive period, a characteristic pattern of couples attempting to "replace" lost offspring. Birth interval analysis pointed to biological "interval effect," whereby infant/child mortality caused a cessation of lactation and hence a shortening of postpartum amenorrhea. Computer simulation further indicated that the higher fertility differential of the cohort experiencing offspring loss still did not result in high son survivorship values. The findings agree with earlier studies indicating that for predemographic transitional populations, economically motivated fertility strategies are ineffectual.     

Intensive genetic assessment of the mating system and reproductive success in a semi-closed population of the mottled sculpin,Cottus bairdi

Most genetic surveys of parentage in nature sample only a small fraction of the breeding population. Here we apply microsatellite markers to deduce the genetic mating system and assess the reproductive success of females and males in an extensively collected, semi-closed stream population of the mottled sculpin fish, Cottus bairdi. In this species, males guard nest rocks where females deposit the eggs for fertilization. The potential exists for both males and females to mate with multiple partners and for males to provide parental care to genetically unrelated offspring. Four hundred and fifty-five adults and subadults, as well as 1,259 offspring from 23 nests, were genotyped at five polymorphic microsatellite loci. Multilocus maternal genotypes, deduced via genetic analyses of embryos, were reconstructed for more than 90% of the analysed nests, thus allowing both male and female reproductive success to be estimated accurately. There was no genetic evidence for cuckoldry, but one nest probably represents a takeover event. Successful males spawned with a mean of 2.8 partners, whereas each female apparently deposited her entire clutch of eggs in a single nest (mean fecundity = 66 eggs/female). On average, genetically deduced sires and dams were captured 1.6 and 9.3 metres from their respective nests, indicating little movement by breeders during the spawning season. Based on a 'genetic mark-recapture' estimate, the total number of potentially breeding adults (c. 570) was an order-of-magnitude larger than genetically based estimates of the effective number of breeders (c. 54). In addition, significantly fewer eggs per female were deposited in single than in multidam nests. Not only were perceived high-quality males spawning with multiple partners, but they were receiving more eggs from each female.     

Estimation of population fecundity of the bitterling,Rhodeus ocellatus,and ecological significance of its spawning habit into bivalves

Fluctuations of the population abundance of the rose bitterling,Rhodeus ocellatus (Kner) in a small pond, Shimizu-ike (700 m²), Osaka Prefecture, Japan, were estimated by the Petersen method from 1973 to 1977. The number of fish fluctuated between 12,600 and 46,700 during that period. In 1974, a large reproductive peak in May contributed mainly by 2- and 3-year-old spawners and a small peak in late July contributed by 1–2-year-old fish were observed. Average number of eggs laid in a bivalve,Anodonta woodiana Lea, in each month was estimated with field experiments from March to November, 1974. In total, 93,400 eggs were laid during the first reproductive peak, and 13,100 eggs during the second reproductive peak. The mortality of eggs and larvae incubated in the bivalve was less than 30%, and approximately 70 % of the larvae that had swum out from the host died in the following six months. Thus, it is estimated that approximately 20% of the eggs laid in the bivalves can survive and grow up to reach the first maturity. The high survival rate ofR. ocellatus among cyprinid fishes might be due to the fact that the eggs and larvae are protected from predation by being embedded in a bivalve, and to the fact that the larvae at the earliest free swimming stage have a good opportunity of surviving because they are much larger in size and more developed morphologically than those of other cyprinid fishes.     

Heterozygosity and fitness in a California population of the labyrinth spider Metepeira ventura (Araneae, Araneidae)

Abstract. The relationship between individual heterozygosity and characteristics likely to be associated with fitness was investigated in the labyrinth spider Metepeira ventura . Adult females and their egg sacs were collected at a coastal site in southern California, and three measures of bodily condition (carapace width, weight, residual index) and six measures of reproductive output (number of egg sacs, variation in egg number among sacs [coefficient of variation], total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were determined for each spider. The sample was polymorphic at three allozyme loci that were in Hardy–Weinberg equilibrium, and individual females were heterozygous at up to two of the three loci, forming three heterozygosity classes (0, 1, and 2). None of the bodily condition measures were significantly related to the number of heterozygous loci, while four of the reproductive output estimators (total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were significantly influenced by heterozygosity. In each significant case, values for class 2 females were less than those for class 0 and 1 females, whose values were usually more similar. Thus, while female bodily condition was comparable among classes, the most heterozygous females produced fewer total eggs and eggs per sac than their less heterozygous peers. The fact that females of M. ventura engage in a reproductive investment-number trade-off suggests that high-variability and low-variability females may be pursuing distinct reproductive strategies in the wild, with more heterozygous females being K -selected (smaller clutches, heavier eggs) and more homozygous females being r -selected (larger clutches, lighter eggs). Further investigation will be needed to assess more fully the fitness value of heterozygosity in M. ventura .