BODY SIZE AND SEXUAL SIZE DIMORPHISM IN MARINE IGUANAS FLUCTUATE AS A RESULT OF OPPOSING NATURAL AND SEXUAL SELECTION: AN ISLAND COMPARISON

Body size is often assumed to represent the outcome of conflicting selection pressures of natural and sexual selection. Marine iguana (Amblyrhynchus cristatus) populations in the Galápagos exhibit 10-fold differences in body mass between island populations. There is also strong sexual size dimorphism, with males being about twice as heavy as females. To understand the evolutionary processes shaping body size in marine iguanas, we analyzed the selection differentials on body size in two island populations (max. male mass 900 g in Genovesa, 3500 g in Santa Fé). Factors that usually confound any evolutionary analysis of body sizes—predation, interspecific food competition, reproductive role division—are ruled out for marine iguanas. We show that, above hatchlings, mortality rates increased with body size in both sexes to the same extent. This effect was independent of individual age. The largest animals (males) of each island were the first to die once environmental conditions deteriorated (e.g., during El Niños). This sex-biased mortality was the result of sexual size dimorphism, but at the same time caused sexual size dimorphism to fluctuate. Mortality differed between seasons (selection differentials as low as –1.4) and acted on different absolute body sizes between islands. Both males and females did not cease growth when an optimal body size for survival was reached, as demonstrated by the fact that individual adult body size phenotypically increased in each population under favorable environmental conditions beyond naturally selected limits. But why did marine iguanas grow “too large” for survival? Due to lek mating, sexual selection constantly favored large body size in males (selection differentials up to +0.77). Females only need to reach a body size sufficient to produce surviving offspring. Thereafter, large body size of females was less favored by fertility selection than large size in males. Resulting from these different selection pressures on male and female size, sexual size dimorphism was mechanistically caused by the fact that females matured at an earlier age and size than males, whereafter they constantly allocated resources into eggs, which slowed growth. The observed allometric increase in sexual size dimorphism is explained by the fact that the difference between these selective processes becomes larger as energy abundance in the environment increases. Because body size is generally highly heritable, these selective processes are expected to lead to genetic differences in body size between islands. We propose a common-garden experiment to determine the influence of genetic factors and phenotypic reaction norms of final body size.     

Sexual dimorphism of body and relative head sizes in neonatal common garter snakes

Morphological and behavioral differences between sexes are commonplace throughout the animal kingdom. Body size is one of the most obvious sex differences frequently found in snakes. However, the developmental origins of size differences in many species, including snakes, are not well known. We examined post-natal variation in sexual size dimorphism in garter snakes Thamnophis sirtalis . The weights, body and tail lengths, and head sizes of male and female neonates born to mothers collected from ecologically dissimilar habitats on Beaver Island, Lake Michigan were compared. Sexual size dimorphism was prominent. Overall, males had significantly longer bodies and tails than females. Females were significantly heavier and had larger heads than male snakes. Maternal site affected head but not body measurements, perhaps due to differences in prey availability. The body condition of maternal females predicted neonatal body length. Significant litter variation suggests heritable variation in morphological traits possibly correlated with feeding success and survival.     

Genetic constraints on floral evolution in a sexually dimorphic plant revealed by artificial selection

Sexual dimorphism is one of the most widespread and recognizable patterns of phenotypic variation in the biotic world. Sexual dimorphism in floral display is striking in the dioecious plant Silene latifolia, with males making many, small flowers compared to females. We investigated this dimorphism via artificial selection on two populations to determine whether genetic variation exists within populations for flower size and the extent of the between-sex correlation, whether a flower size and number trade-off exists within each sex, and whether pollen and ovule production vary with flower size. We selected for decreased flower size (calyx width) in females and increased flower size in males and measured the response to selection in size and correlated responses in flower dry mass, flower number, and pollen or ovule number per flower. Four bouts of selection in each of two selection programs were performed, for a total of three selection lines to decrease size, three to increase it, and two control lines. Flower size always significantly responded to selection and we always found a significant correlated response in the sex not under selection. Selection decreased but did not eliminate the sexual dimorphism in flower dry mass and number. A negative relationship between flower size and number within each sex was revealed. Whereas ovule number showed a significant correlated response to selection on flower size, pollen number did not. Our results indicate that although substantial additive genetic variation for flower size exists, the high between-sex genetic correlation would likely constrain flower size from becoming more sexually dimorphic. Furthermore, floral display within each sex is constrained by a flower size and number trade-off. Given this trade-off and lack of variation in pollen production with flower size, we suggest that sexual dimorphism evolved via sexual selection to increase flower number in males but not females.     

Sexual antagonism for resistance and tolerance to infection in Drosophila melanogaster

A critical task in evolutionary genetics is to explain the persistence of heritable variation in fitness-related traits such as immunity. Ecological factors can maintain genetic variation in immunity, but less is known about the role of other factors, such as antagonistic pleiotropy, on immunity. Sexually dimorphic immunity—with females often being more immune-competent—may maintain variation in immunity in dioecious populations. Most eco-immunological studies assess host resistance to parasites rather than the host''s ability to maintain fitness during infection (tolerance). Distinguishing between resistance and tolerance is important as they are thought to have markedly different evolutionary and epidemiological outcomes. Few studies have investigated tolerance in animals, and the extent of sexual dimorphism in tolerance is unknown. Using males and females from 50 Drosophila melanogaster genotypes, we investigated possible sources of genetic variation for immunity by assessing both resistance and tolerance to the common bacterial pathogen Pseudomonas aeruginosa. We found evidence of sexual dimorphism and sexual antagonism for resistance and tolerance, and a trade-off between the two traits. Our findings suggest that antagonistic pleiotropy may be a major contributor to variation in immunity, with implications for host–parasite coevolution.     

昆虫体型及性体型二型性的地理变异

体型是昆虫基本的形态特性,它会影响到昆虫几乎所有的生理和生活史特性。同种昆虫不同地理种群在体型上常表现出明显的渐变,导致这些渐变的环境因素包括温度、湿度、光照、寄主植物、种群密度等,并且多种环境因素也会对昆虫种群内个体体型产生影响。雌雄个体的体型存在差异,称性体型二型性。性体型二型性也显示了地理差异。这些差异形成的途径已经得到详细的分析,其形成机制导致多个假说的提出,这些假说又在多种昆虫中得到验证。本文从同一种昆虫不同种群间、同一种群内、雌雄虫个体间3个水平,对种内昆虫体型变异的方式,影响昆虫种群间体型变异和种群内昆虫体型的变异的环境因素,以及昆虫性体型二型性及其地理变异的现象等方面的研究进行了综述,并对未来的相关研究提供了建议。     

Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas (Gorilla gorilla)

Investigating sexual dimorphism is important for our understanding of its influence on reproductive strategies including male-male competition, mate choice, and sexual conflict. Measuring physical traits in wild animals can be logistically challenging and disruptive for the animals. Therefore body size and ornament variation in wild primates have rarely been quantified. Gorillas are amongst the most sexually dimorphic and dichromatic primates. Adult males (silverbacks) possess a prominent sagittal crest, a pad of fibrous and fatty tissue on top of the head, have red crest coloration, their saddle appears silver, and they possess a silverline along their stomach. Here we measure levels of sexual dimorphism and within-male variation of body length, head size, and sexual dichromatism in a population of wild western gorillas using photogrammetry. Digital photogrammetry is a useful and precise method to measure sexual dimorphism in physical traits yielding sexual dimorphism indices (ISD), similar to those derived from traditional measurements of skeletal remains. Silverbacks were on an average 1.23 times longer in body length than adult females. Sexual dimorphism of head size was highest in measures of crest size (max ISD: 60.4) compared with measures of facial height (max ISD: 24.7). The most sexually dimorphic head size measures also showed the highest within-sex variation. We found no clear sex differences in crest coloration but there was large sexual dichromatism with high within-male variation in saddle coloration and silverline size. Further studies should examine if these sexually dimorphic traits are honest signals of competitive ability and confer an advantage in reproductive success.     

Condition dependence and the maintenance of genetic variance in a sexually dimorphic black scavenger fly

The maintenance of genetic variation in traits under strong sexual selection is a longstanding problem in evolutionary biology. The genic capture model proposes that this problem can be explained by the evolution of condition dependence in exaggerated male traits. We tested the predictions that condition dependence should be more pronounced in male sexual traits and that genetic variance in expression of these traits should increase under stress as among‐genotype variation in overall condition is exposed. Genetic variance in female and nonsexual traits should, by contrast, be similar across environments as a result of stabilizing selection on trait expression. The relationship between the degree of sexual dimorphism, condition dependence and additive genetic variance (V_a) was assessed for two morphological traits (body size and relative fore femur width) affecting male mating success in the black scavenger fly Sepsis punctum (Diptera: Sepsidae) and for development time (a nonsexual trait often correlated with body size). We compared trait expression between the sexes for two cross‐continental populations that differ in degree of sexual dimorphism (Ottawa and Zurich). Condition dependence was indeed most pronounced in males of the strongly dimorphic Zurich population (males larger), and V_a was similar for males and females unless the trait was strongly sex specific and condition dependent. Contrary to prediction, however, V_a primarily increased under food limitation in both sexes, and genetic variance in fore femur width was low to nil, perhaps depleted by putatively strong sexual selection. Solely for body size of Zurich males, V_a increased more in males than females at limited food, in accordance with the predictions of the genic capture model. Overall therefore, quantitative genetic evidence in support of the model was inconsistent and weak at best.     

Body size variation and sexual size dimorphism across climatic gradients in the widespread treefrog Scinax fuscovarius (Anura,Hylidae)

Variation in body size represents one of the crucial raw materials for evolution. However, at present, it is still being debated what is the main factor affecting body size or if the final body size is the consequence of several factors acting synergistically. To evaluate this, widespread species seem to be suitable models because the different populations occur along a geographical gradient and under contrasted climatic and environmental conditions. Here we describe the spatial pattern of variation in body size and sexual size dimorphism in the snouted treefrog Scinax fuscovarius (Anura, Hylidae) along a 10° range in latitude, 25° longitude, and 2000 m in altitude from Argentina, Brazil and Paraguay using an information‐theoretic approach to evaluate the support of the data for eight a priori hypotheses proposed in the literature to account for geographical body size, and three hypotheses for sexual size dimorphism variation. Body size of S. fuscovarius varied most dramatically with longitude and less so with latitude; frogs were largest in the northwestern populations. Body size was positively related with precipitation seasonality, and negatively with annual precipitation. Furthermore, the degree of sexual size dimorphism was greatest in the western populations with less annual precipitation, as the increase in body size was stronger for females. Our results on body size variation are consistent with two ecogeographical hypotheses, the starvation resistance and the water availability hypotheses, while our results on sexual size dimorphism in S. fuscovarius supports the differential‐plasticity hypothesis but the inverse to Rensch's rule and the parental investment hypothesis. Due to the weak association between environmental variables and body size and sexual size dimorphism variation, we stress that there are other factors, mainly those related to the life history, driving the geographical variation of S. fuscovarius.     

Convergent evolution of sexual shape dimorphism in Diptera

Several patterns of sexual shape dimorphism, such as male body elongation, eye stalks, or extensions of the exoskeleton, have evolved repeatedly in the true flies (Diptera). Although these dimorphisms may have evolved in response to sexual selection on male body shape, conserved genetic factors may have contributed to this convergent evolution, resulting in stronger phenotypic convergence than might be expected from functional requirements alone. I compared phenotypic variation in body shape in two distantly related species exhibiting sexually dimorphic body elongation: Prochyliza xanthostoma (Piophilidae) and Telostylinus angusticollis (Neriidae). Although sexual selection appears to act differently on male body shape in these species, they exhibited strikingly similar patterns of sexual dimorphism. Likewise, patterns of within-sex shape variation were similar in the two species, particularly in males: relative elongation of the male head capsule, antenna, and legs was associated with reduced head capsule width and wing length, but was nearly independent of variation in thorax length. However, the two species presented contrasting patterns of static allometry: male sexual traits exhibited elevated allometric slopes in T. angusticollis, but not in P. xanthostoma. These results suggest that a shared pattern of covariation among traits may have channeled the evolution of sexually dimorphic body elongation in these species. Nonetheless, static allometries may have been shaped by species-specific selection pressures or genetic architectures.     

Sexual shape dimorphism accelerated by male–male competition,but not prevented by sex-indiscriminate parental care in dung beetles (Scarabaeidae)

Dimorphic sexual differences in shape and body size are called sexual dimorphism and sexual size dimorphism, respectively. The degrees of both dimorphisms are considered to increase with sexual selection, represented by male–male competition. However, the degrees of the two dimorphisms often differ within a species. In some dung beetles, typical sexual shape dimorphisms are seen in male horns and other exaggerated traits, although sexual size dimorphism looks rare. We hypothesized that the evolution of this sexual shape dimorphism without sexual size dimorphism is caused by male–male competition and their crucial and sex-indiscriminate provisioning behaviors, in which parents provide the equivalent size of brood ball with each of both sons and daughters indiscriminately. As a result of individual-based model simulations, we show that parents evolve to provide each of sons and daughters with the optimal amount of resource for a son when parents do not distinguish the sex of offspring and males compete for mates. This result explains why crucial and sex-indiscriminate parental provisioning does not prevent the evolution of sexual shape dimorphism. The model result was supported by empirical data of Scarabaeidae beetles. In some dung beetles, sexual size dimorphism is absent, compared with significant sexual size dimorphism in other horned beetles, although both groups exhibit similar degrees of sexual shape dimorphism in male horns and other exaggerated traits.     

Ontogenetically stable dimorphism in a lacertid lizard (Acanthodactylus boskianus) with tests of methodology and comments on life-history

Recent arguments in the literature prompted us to compare methods for assessing sexual dimorphism in body proportions of lacertid lizards, using Acanthodactylus boskianus . Although expressing body-part measurements as proportional to head length was the most effective method, we recommend using trunk length for the baseline as a general method for lizards. We also argue that, when aiming to assess sexual dimorphism in body proportions of lizards, if the context is ecological, all available adults should be included. However, for morphology and taxonomy, small sub-samples of the largest individuals that maximally express their genetic morphological potential should be used. In A. boskianus , the sexual dimorphism of mensural characters in adults was typical: males were larger, with relatively larger head and appendages. However, the ontogeny of this dimorphism was unusual in that the differences existed already in youth and thereafter persisted isometrically. The sexual dimorphism of meristic characters was male-biased in numbers of femoral pores and of caudal vertebrae, and female-biased in numbers of ventral plates along the trunk and of precaudal vertebrae. Size dimorphism may conceivably play a role in sex recognition because two potential visual cues (i.e. size dimorphism and dichromatism) appear to complement each other.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society 2009, 97 , 275–288.     

Sexual dimorphism of head morphology in three‐spined stickleback Gasterosteus aculeatus

This study examined sexual dimorphism of head morphology in the ecologically diverse three‐spined stickleback Gasterosteus aculeatus. Male G. aculeatus had longer heads than female G. aculeatus in all 10 anadromous, stream and lake populations examined, and head length growth rates were significantly higher in males in half of the populations sampled, indicating that differences in head size increased with body size in many populations. Despite consistently larger heads in males, there was significant variation in size‐adjusted head length among populations, suggesting that the relationship between head length and body length was flexible. Inter‐population differences in head length were correlated between sexes, thus population‐level factors influenced head length in both sexes despite the sexual dimorphism present. Head shape variation between lake and anadromous populations was greater than that between sexes. The common divergence in head shape between sexes across populations was about twice as important as the sexual dimorphism unique to each population. Finally, much of the sexual dimorphism in head length was due to divergence in the anterior region of the head, where the primary trophic structures were found. It is unclear whether the sexual dimorphism was due to natural selection for niche divergence between sexes or sexual selection. This study improves knowledge of the magnitude, growth rate divergence, inter‐population variation and location of sexual dimorphism in G. aculeatus head morphology.     

The evolution of condition-dependent sexual dimorphism

Theory suggests that the net benefit of allocating resources to a sexual trait depends both on the strength of sexual selection on that trait and on individual condition. This predicts a tight coevolution between sexual dimorphism and condition dependence and suggests that these patterns of within-sex and between-sex variation may share a common genetic and developmental basis. Although condition-dependent expression of sexual traits is widely documented, the extent of covariation between condition dependence and sexual dimorphism remains poorly known. I investigated the effects of condition (larval diet quality) on multivariate sexual dimorphism in the fly Telostylinus angusticollis (Neriidae). Condition determined the direction of sexual size dimorphism and modulated sexual shape dimorphism by affecting allometric slopes and/or intercepts of sexually homologous traits in both sexes. Although the greatest responses to condition manipulation were observed in male sexual traits, both sexual and nonsexual traits exhibited substantial variation in the nature and magnitude of condition effects. Nonetheless, condition dependence and sexual dimorphism were remarkably congruent: variation in the strength of condition effects on male traits explained more than 90% of the variation in the magnitude of sexual dimorphism, whether quantified in terms of trait size or allometric slope. The genetic mechanisms that give rise to multivariate sexual dimorphism in body shape thus function in a strongly condition-dependent manner in this species, suggesting a common genetic basis for body shape variation within and between sexes.     

SEXUAL SIZE DIMORPHISM AS A CORRELATED RESPONSE TO SELECTION ON BODY SIZE: AN EMPIRICAL TEST OF THE QUANTITATIVE GENETIC MODEL

We artificially selected for body size in Drosophila melanogaster to test Lande's quantitative genetic model for the evolution of sexual size dimorphism. Thorax width was used as an estimator of body size. Selection was maintained for 21 generations in both directions on males only, females only, or both sexes simultaneously. The correlated response of sexual size dimorphism in each selection regime was compared to the response predicted by four variants of the model, each of which differed only in assumptions about input parameters. Body size responded well to selection, but the correlated response of sexual size dimorphism was weaker than that predicted by any of the variants. Dimorphism decreased in most selection lines, contrary to the model predictions. We suggest that selection on body size acts primarily on growth trajectories. Changes in dimorphism are caused by the fact that male and female growth trajectories are not parallel and termination of growth at different points along the curves results in dimorphism levels that are difficult to predict without detailed knowledge of growth parameters. This may also explain many of the inconsistent results in dimorphism changes seen in earlier selection experiments.     

Phylogenetic analyses of dimorphism in primates: evidence for stronger selection on canine size than on body size

Phylogenetic comparative methods were used to analyze the consequences of sexual selection on canine size and canine size dimorphism in primates. Our analyses of previously published body mass and canine size data revealed that the degree of sexual selection is correlated with canine size dimorphism, as well as with canine size in both sexes, in haplorhine but not in strepsirrhine primates. Consistent with these results, male and female canine size was found to be highly correlated in all primates. Since canine dimorphism and canine size in both sexes in haplorhines were found to be not only related to mating system but also to body size and body size dimorphism (characters which are also subject to or the result of sexual selection), it was not apparent whether the degree of canine dimorphism is the result of sexual selection on canine size itself, or whether canine dimorphism is instead a consequence of selection on body size, or vice versa. To distinguish among these possibilities, we conducted matched-pairs analyses on canine size after correcting for the effects of body size. These tests revealed significant effects of sexual selection on relative canine size, indicating that canine size is more important in haplorhine male-male competition than body size. Further analyses showed, however, that it was not possible to detect any evolutionary lag between canine size and body size, or between canine size dimorphism and body size dimorphism. Additional support for the notion of special selection on canine size consisted of allometric relationships in haplorhines between canine size and canine size dimorphism in males, as well as between canine size dimorphism and body size dimorphism. In conclusion, these analyses revealed that the effects of sexual selection on canine size are stronger than those on body size, perhaps indicating that canines are more important than body size in haplorhine male-male competition.     

Development of intraspecific size variation in black coucals,white-browed coucals and ruffs from hatching to fledging

Most studies on sexual size dimorphism address proximate and functional questions related to adults, but sexual size dimorphism usually develops during ontogeny and developmental trajectories of sexual size dimorphism are poorly understood. We studied three bird species with variation in adult sexual size dimorphism: black coucals (females 69% heavier than males), white-browed coucals (females 13% heavier than males) and ruffs (males 70% heavier than females). Using a flexible Bayesian generalized additive model framework (GAMM), we examined when and how sexual size dimorphism developed in body mass, tarsus length and bill length from hatching until fledging. In ruffs, we additionally examined the development of intrasexual size variation among three morphs (Independents, Satellites and Faeders), which creates another level of variation in adult size of males and females. We found that 27–100% of the adult inter- and intrasexual size variation developed until fledging although none of the species completed growth during the observational period. In general, the larger sex/morph grew more quickly and reached its maximal absolute growth rate later than the smaller sex/morph. However, when the daily increase in body mass was modelled as a proportion, growth patterns were synchronized between and within sexes. Growth broadly followed sigmoidal asymptotic models, however only with the flexible GAMM approach, residual distributions were homogeneous over the entire observation periods. These results provide a platform for future studies to relate variation in growth to selective pressures and proximate mechanisms in these three species, and they highlight the advantage of using a flexible model approach for examining growth variation during ontogeny.     

Sexual selection on skeletal shape in Carnivora

Lifetime reproductive success of males is often dependent upon the ability to physically compete for mates. However, species variation in social structure leads to differences in the relative importance of intraspecific aggression. Here, we present a large comparative dataset on sexual dimorphism in skeletal shape in Carnivora to test the hypotheses that carnivorans exhibit sexual dimorphism in skeletal anatomy that is reflective of greater specialization for physical aggression in males relative to females and that this dimorphism is associated with the intensity of sexual selection. We tested these hypotheses using a set of functional indices predicted to improve aggressive performance. Our results indicate that skeletal shape dimorphism is widespread within our sample. Functional traits thought to enhance aggressive performance are more pronounced in males. Phylogenetic model selection suggests that the evolution of this dimorphism is driven by sexual selection, with the best‐fitting model indicating greater dimorphism in polygynous versus nonpolygynous species. Skeletal shape dimorphism is correlated with body size dimorphism, a common indicator of the intensity of male–male competition, but not with mean body size. These results represent the first evidence of sexual dimorphism in the primary locomotor system of a large sample of mammals.     

Intrasexual competition and body weight dimorphism in anthropoid primates

Body weight dimorphism in anthropoid primates has been thought to be a consequence of sexual selection resulting from male-male competition for access to mates. However, while monogamous anthropoids show low degrees of weight dimorphism, as predicted by the sexual selection hypothesis, polygynous anthropoids show high variation in weight dimorphism that is not associated with measures of mating system or sex ratio. This observation has led many to debate the role of other factors such as dietary constraints, predation pressure, substrate constraints, allometric effects, and phylogeny in the evolution of anthropoid weight dimorphism. Here, we re-evaluate variation in adult body weight dimorphism in anthropoids, testing the sexual selection hypothesis using categorical estimates of the degree of male-male intrasexual competition (“competition levels”). We also test the hypotheses that interspecific variation in body weight dimorphism is associated with female body weight and categorical estimates of diet, substrate use, and phylogeny. Weight dimorphism is strongly associated with competition levels, corroborating the sexual selection hypothesis. Weight dimorphism is positively correlated with increasing female body weight, but evidence suggests that the correlation reflects an interaction between overall size and behavior. Arboreal species are, on average, less dimorphic than terrestrial species, while more frugivorous species tend to be more dimorphic than folivorous or insectivorous species. Several alternative hypotheses can explain these latter results. Weight dimorphism is correlated with taxonomy, but so too are competition levels. We suggest that most taxonomic correlations of weight dimorphism represent “phylogenetic niche conservatism”; however, colobines show consistently low degrees of weight dimorphism for reasons that are not clear. Am J Phys Anthropol 103:37–68, 1997. © 1997 Wiley-Liss, Inc.     

Sex-specific trait architecture in a spider with sexual size dimorphism

Sexual dimorphism, or sex-specific trait expression, may evolve when selection favours different optima for the same trait between sexes, that is, under antagonistic selection. Intra-locus sexual conflict exists when the sexually dimorphic trait under antagonistic selection is based on genes shared between sexes. A common assumption is that the presence of sexual-size dimorphism (SSD) indicates that sexual conflict has been, at least partly, resolved via decoupling of the trait architecture between sexes. However, whether and how decoupling of the trait architecture between sexes has been realized often remains unknown. We tested for differences in architecture of adult body size between sexes in a species with extreme SSD, the African hermit spider (Nephilingis cruentata), where adult female body size greatly exceeds that of males. Specifically, we estimated the sex-specific importance of genetic and maternal effects on adult body size among individuals that we laboratory-reared for up to eight generations. Quantitative genetic model estimates indicated that size variation in females is to a larger extent explained by direct genetic effects than by maternal effects, but in males to a larger extent by maternal than by genetic effects. We conclude that this sex-specific body-size architecture enables body-size evolution to proceed much more independently than under a common architecture to both sexes.     

中国现代人群两性身高差异分布及其影响因素

本文对中国现代人群的两性身高差异分布状况及其影响因素进行了分析。选用152处中国现代人群（含69处汉族人群和83处少数民族人群）的男、女性身高数据,计算两性身高差异指数,并对比该指数在南、北方汉族和少数民族人群间的分布差异,同时分析纬度、气候、体格大小与城乡环境因素对两性身高差异程度的影响。结果表明,中国男性的平均身高比女性高出约7.16%(4.72%~9.26%）;南、北方汉族和少数民族之间的两性身高差异程度相似,北方汉族和南方汉族两性身高差异程度相似,但北方少数民族的两性身高差异明显大于南方少数民族。此外,两性身高差异程度与纬度、气温年较差和年均风速呈低度线性正相关,与年均气温、年均降水量和年均相对湿度呈低度线性负相关,而与体格大小和城乡环境并无显著关联。这提示遗传和自然环境因素在中国现代人群两性身高差异的区域化演变中更趋主导性,而社会环境因素的影响程度相对较低。