Relative warp analysis of skull shape across the hybrid zone of the house mouse (Mus musculus) in Denmark.

The changes in skull shape that occur in the hybrid zone between the two European subspecies of the house mouse ( Mus musculus musculus and M. m. domesticus ) were studied by relative warp analyses. Landmarks observed on the ventral view of the skulls of 269 mice sampled in 18 localities in Denmark were analysed. Each population was also characterized by a hybrid index estimated from allozymic data. Although no clear pattern of within-population variability of shape could be established across the hybrid zone, the shape changes among the 18 populations were found to be correlated with the allozymic introgression but not with geographical location. Finally, the cline obtained for skull shape seems to be steeper than that corresponding to the average allozyme hybrid index which suggests that skull development could be slightly perturbed in hybrids.     

Body size and craniometry of the herb field mouse from Lithuania in the context of species range

We present morphometric and craniometric measurements of the herb field mouse (Apodemus uralensis) from Lithuania and analyze variation of body and skull size across species range. We suppose species is characterized by high size variability, not following Bergmann’s or Murphy’s rules. Preliminary, distinct size differences have been registered in the eastern and southern edges of the distribution range, with these populations having largest individuals according to average body and skull size. In terms of tail length and condylobasal length of the skull, Lithuanian mice on the north-western edge of the species range are among the largest, but in terms of body weight, body length, zygomatic skull width and the length of maxillary toothrow, adult A. uralensis from Lithuania are small and correspond to those from populations on the western edge of the range. The relative skull width (ratio of zygomatic skull width to condylobasal length) of Lithuanian A. uralensis is the smallest across the entire range. In A. uralensis from Lithuania, sex dimorphism is weakly expressed, with hind foot length and postorbital constriction larger in adult males, while the height of the mandibula and length of the mandibular diastema is larger in adult females. Juvenile and subadult A. uralensis from Lithuania differ in body weight, but not in size.     

Some aspects of intraspecific variability of the closely related species of the Dermacentor marginatus complex (Acari: Ixodidae) as demonstration of microevolutionary process

Individual and geographical variability of male conscutum pattern in five closely related species of the Dermacentor marginatus complex (D. marginatus, D. ushakovae, D. niveus, D. silvarum, D. nuttalli) has been examined. The pattern has been examined in three to six geographical samples within each specific distribution range. It was established that the pattern of the conscutum central area is subjected to individual and geographical variability on an extreme degree and gives very few intraspecific differential characters, but it shows interspecific differences in some cases. However the dark patches of marginal flank (npkappadelta and 3deltakappa respectively, see Fig. 3) show statistically significant differences in length in all geographical samples of the first four species. Characteristic features of ixodid ticks morpogenesis rule out to a considerable extent the possibility to trace geographical variability of the same characters by all stages of ontogenesis. In these cases, when it is possible, the tendencies to variability on different stages do not always coincide. There is no coordination within the species in the degree of differences of examined geographical samples by pattern and morphological characters, i. e. very complex polymorphis is observed. In the context of the evolution that kind of polymorphism of the geographical samples has provided the species with high adaptive potential for conquest of the extensive range and maintaining large numbers. The question of allopatric speciation of the closely related D. marginatus-D. silvarum with small secondary area of transgression their ranges, and sympatric speciation of the D. ushakovae-D. niveus is postulated.     

Environment and space as drivers of variation in skull shape in two widely distributed South‐American Tayassuidae,Pecari tajacu and Tayassu pecari (Mammalia: Cetartiodactyla)

The influence of the environment on the geographical variation of morphological traits has been recognized in a number of taxa. Pecari tajacu and Tayassu pecari are ideal models to investigate intraspecific geographic variation in skull because of their wide and heterogeneous geographical distribution in South America. We used geometric morphometric procedures to examine the geographical variation in skull shape of 294 adult specimens of these species from 134 localities. We quantified to what extent skull shape variation was explained by environment, skull size and geographical space using variation partitioning analysis. We detected a strong pattern of geographic variation for P. tajacu skull shape, but not for T. pecari. The environment seems to be the major selective force that drives skull shape variation in both species. Nevertheless, other spatially structured processes (e.g. genetic drift, gene flow) might also have affected variation in the skull shape of the more widespread species P. tajacu. Allometric relationships might reflect the biomechanical constraints that are thought to be strong enough to limit size‐related changes in T. pecari skull shape.     

Investigating South American biogeographic history using patterns of skull shape variation on Cerdocyon thous (Mammalia: Canidae)

Patterns of geographic variation of the canid Cerdocyon thous have historically been obscured by its remarkable intraspecific morphological variability. The observed distribution is highly associated with phytophysiognomy, a feature considered highly dynamic along geological time. In the present study, we tested whether vegetation distribution during the Holocene Glacial Maximum of South America (HGM) explains the patterns of morphological variation within Cerdocyon thous . The species was divided in groups according to paleohabitats that could support their presence during the HGM, and then tested for differences in skull morphometrics. The results obtained demonstrate that the climatic changes during the HGM influenced the population structure of this species, resulting in the establishment of geographical groups with different degrees of morphological cohesion. Higher morphological cohesion found in the Northern group might be explained by the marked discontinuity between its geographical range and the rest of the species'distribution. The Eastern and Southern morphological divergence is less striking and, although this could be related to past vegetation distribution, the disappearance of those barriers leads to a population structure that could be slowly breaking down.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 77–84.     

Environmental variability and biogeography: the relationship between bathymetric distribution and geographical range size in marine algae and gastropods

Aims Gradients of environmental variability have been proposed to explain spatial variation in patterns of geographical range size. We explore this relationship in NE Pacific algae and NW Atlantic gastropods by using the characteristics of species’ bathymetric distributions as a proxy for tolerance of environmental variability. Location NE Pacific and NW Atlantic. Methods Data on species bathymetric and geographical distributions were compiled from the literature. Results For both algae and gastropods, species that inhabit highly seasonal, shallow depth zones have broader latitudinal ranges, and occupy more biogeographical provinces, than species that live in more temporally stable, deeper zones. Furthermore, species that tolerate spatial variability along the bathymetric axis, i.e. those that occur in multiple depth zones, have broader geographical ranges than species restricted to fewer depth zones. Main conclusions Within‐range environmental variability, through both space and time, is predictive of large geographical ranges for marine algae and gastropods. Analysis of species distributions across perpendicular gradients (e.g. depth and latitude) is a powerful approach to discerning the mechanisms that govern biogeographical patterns, and provides easily obtainable broad‐brush predictions regarding the biogeographical outcomes of global change.     

样本容量和物种特征对BIOCLIM模型模拟物种分布准确度的影响——以12个中国特有落叶栎树种为例

物种分布模型被广泛应用于生态学、生物地理学及保护生物学等领域的研究。由于难于取样或标本记录不完善等原因, 真正能够用于模型预测的物种分布数据非常有限。因此, 有必要搞清楚样本容量和物种特征对模型模拟准确度的影响, 为确定以物种特征为区分条件的最小样本容量奠定基础。为了探讨应用BIOCLIM模型预测中国特有植物种的效果, 以12个落叶栎树种为例, 从不同的样本容量和生态特征两方面研究其对BIOCLIM模型模拟准确度的影响。结果表明: BIOCLIM模型模拟准确度随样本容量的增加在初期几乎呈直线增加趋势至样本容量达到25, 随后渐变平缓至样本容量为75~100时达到最大值。此外, 生态幅窄和环境特化物种比生态幅宽和对环境耐受性强的物种更容易获得较高的准确度。结果说明, BIOCLIM可有效地用于样本数量较小的狭域型物种分布预测。     

Scaling up from epidemiology to biogeography: local infection patterns predict geographical distribution in fish parasites

Aim We investigated how the spatial distribution of parasites, measured as either their geographical range size or their frequency of occurrence among localities, relates to either their average local abundance or the variance in their abundance among localities where they occur. Location We used data on the abundance of 46 metazoan parasite species in 66 populations of threespine sticklebacks, Gasterosteus aculeatus, from Europe and North America. Methods For each parasite species, frequency of occurrence was calculated as the proportion of stickleback populations in which it occurred, and geographical range size as the area within the smallest possible polygon delimited using the coordinates of the localities where it occurred. Generalized linear models were used to assess how these two measures of spatial distribution were influenced by several predictor variables: geographical region (North America or Europe), life cycle (simple or complex), average local abundance, the coefficient of variation in abundance across localities, and median prevalence (proportion of infected hosts within a locality). Results Our analyses uncovered four patterns. First, parasites in North America tend to have higher frequencies of occurrence among surveyed localities, but not broader geographical ranges, than those in Europe. Second, parasite species with simple life cycles have wider geographical ranges than those with complex cycles. Third, there was a positive relationship between average abundance of the different parasite species and their frequency of occurrence, but not between average abundance and geographical range size. Fourth, the coefficient of variation in abundance covaried positively with both the frequency of occurrence and geographical range size across the different parasite species. Thus, all else being equal, parasites showing greater site‐to‐site variability in abundance occur in a greater proportion of localities and over a broader geographical area than those with a more stable abundance among sites. Main conclusions Local infection patterns are linked with large‐scale distributional patterns in fish parasites, independently of host effects, such that local commonness translates into regional commonness. The mechanisms linking parasite success at both scales remain unclear, but may include those that maintain the continuum between specialist and generalist parasites. Regardless, the observed patterns have implications for the predicted changes in the geographical distributions of many parasites in response to climate change.     

Geographic pattern of cranial differentiation in the Asian Midday Jird Meriones meridianus (Rodentia: Muridae: Gerbillinae) and its taxonomic implications

The existence of cryptic species in the midday jird (Meriones meridianus) has been suggested in literature, although based on little empirical data to support this hypothesis. In this study, a two‐dimensional landmark‐based geometric morphometric approach was used to investigate whether patterns in intraspecific variation in skull shape and size exist, using 110 skull specimens from more than 20 different localities along the distribution range of M. meridianus. This is the first study of morphological differences on such a big sample size and geographical range, and it tries to find whether skull shape variation in this species is best described as being clinal or rather reflecting cryptic diversity. The latter seems to be the case, as a dimorphic skull phenotype was found, reflecting a geographic disparity between the Middle East and the Far East specimens both in shape and in size. Distinct cranial differences were found in the overall cranial size and, also at the level of the inflation of the bulla, the elongation of the nasal, the length of the teeth row and the incisive foramen, as well as the distance in between the latter two. It thus seems that M. meridianus from Middle East is morphologically distinct from that of the Far East. Furthermore, our results also demonstrate that clinal variation could explain variation within Middle East populations, whereas a more heterogenous pattern is found for those of the Far East. The hypothesis that the observed phenotypic variation may reflect cryptic species is discussed, with the recommendation for a thorough taxonomical revision of the genus in the region.     

Geographical variability of allozyme variation and genetic divergence between Tunisian lizards of the sand-dwelling lacertid genus Acanthodactylus

Acanthodactylus is a widespread lacertid genus including about thirthy species whose systematics remains much debated.The present study is aimed at improving the taxonomic status of the Tunisian species whose geographical distribution and ecological requirements have been studied elsewhere. Allozymic variation at 22 loci was scored in 14 populations for a total of 249 individuals. High genetic variability is confirmed in all samples; it is higher in species displaying a wide bioclimatic habitat range. No reduction of genetic variability was observed in two insular populations.Any interspecific hybrid could be detected from our genetic data, even in sympatric areas arguing in favor of specific status of four taxons in Northern, Central and Southern Tunisia.Phylogenetic relationships are discussed on the basis of UPGMA and Fitch-Margoliash procedures applied to the genetic distances matrix and centered data analysis of allozyme frequencies.     

Genetic analysis of southern African gemsbok (Oryx gazella) reveals high variability, distinct lineages and strong divergence from the East African Oryx beisa

We carried out a population genetic analysis of five southern African gemsbok (Oryx gazella) populations based on 530 bp of the mitochondrial control region and ten microsatellites in 75 individuals. Both markers show the high variability often observed in African bovids. Three of the populations which can be traced back to very small founding or current sizes do not show any signs of reduced variability compared to the remaining populations. The mitochondrial haplotypes form three distinct lineages which most likely originated in the Pleistocene when climate fluctuations led to periodical reduction and spreading of gemsbok habitat and which, today, are found throughout the distribution range. Bayesian microsatellite analyses yielded two groups, suggesting a more recent geographical differentiation following the admixture of the mtDNA lineages. Combining our sequences with available published data of the remaining oryx species allowed for a direct molecular comparison of O. gazella and O. beisa which have sometimes been considered a single species. The average genetic divergence between haplotypes from the two taxa was very high (39.9%), supporting their classification into two different species.     

No evidence of past bottlenecks in two Danish mustelids: results of craniometric and genetic studies in time and space

A craniometric and molecular genetic investigation was conducted in Danish stoat (Mustela erminea) and weasel (Mustela nivalis) populations. Specimens used were collected over a wide time span (stoat: 1864–2002; weasel: 1863–1990) and from several geographical regions (Jutland peninsula and the two islands of Funen and Zealand). The study was made with a temporal and a spatial perspective, allowing the estimation of differences in genetic diversity and craniometrical trait means between geographical regions and through time with the use of ancient DNA techniques. Univariate statistics of 11 trait lengths did not reveal geographical differentiation in size and shape among the different regions for the stoat, but a geographical differentiation in shape was found for the weasel. There was evidence for reductions in skull size with the year of collection in male stoats, but not in females, which suggests that some selective pressures or environmental factors have affected male stoats to a greater extent than female stoats and the weasel. Relatively high values of heterozygosity were found in both the stoat and weasel, using microsatellite markers. The level of genetic variability of the stoat collected recently was compared with the level of genetic variability in the historical samples, demonstrating that the stoat has not suffered severe loss of genetic variability through the investigated period. A comparison of recent and historical genetic variability of the weasel was not possible because the ancient DNA extracted from the weasels was too degraded. Pairwise F_ST values and assignment tests showed small but significant genetic differentiation between the different geographical regions for both the stoat and weasel. No genetic differentiation between the recent and historical samples of the stoat was found. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88 , 541–553.     

Craniometric variation and the settlement of the Americas: testing hypotheses by means of R-matrix and matrix correlation analyses

New archaeological findings and the incorporation of new South American skull samples have raised fundamental questions for the classical theories of the Americas' settlement. The aim of this study was to estimate craniometric variability among several Asian and Native American populations in order to test goodness of fit of the data to different models of ancient population entries and dispersions into the New World. Our data set includes Howells' variables recorded on East Asian, North American, and South American natives (except for Na-Dene speakers). Five Fuego-Patagonian samples and one Paleoamerican sample were also included. A multivariate extension of the R-matrix method for quantitative traits was used to obtain Fst values, which were considered estimations of intergroup variation. Three main models for the peopling of the New World were represented in hypothetical design matrices. Matrix permutation tests were performed to quantify the fit of the observed data with 1) geographical separation of the samples and 2) three ways of settlement, which were the Three Migration Model (TMM), the Single Wave Migration model (SWM), and the Two Components Settlement Model (TCS). R-matrix results showed high levels of heterogeneity among Native Americans. Matrix permutation analyses suggested that the model involving high Amerindian heterogeneity and two different morphological patterns or components (derived "Mongoloid" vs. generalized "non-Mongoloid") explains better the variation observed, even when the effects of geographical separation are removed. Whether these patterns arose as a result of two separate migration events or by local evolution from Paleoamericans to Amerindians remains unresolved.     

大蹄蝠头骨形态地理变化

本文采用几何形态测量法对中国大蹄蝠9个不同地理种群头骨形态变化进行研究。结果表明,不同地理种群的头骨大小及形状存在显著差异,其中云南思茅种群与海南陵水种群差异最大。回归分析表明头骨形态的地理变化与气候因素相关。随着年均温度、年均湿度的升高以及年均降水量的增多,大蹄蝠头骨变小,上颌、齿、咬肌附着部分以及耳蜗部分的形状发生变化。此外,头骨大小与海拔高度呈正相关,头骨形状变化与纬度显著相关。本研究表明对栖息地生态条件的适应是中国大蹄蝠头骨形态地理变化的重要原因。     

作物模型区域应用两种参数校准方法的比较

区域模拟的目的是利用有限的空间数据模拟出产量等作物性状的时空变异规律.然而站点作物模型应用到区域范围时涉及到数据归一化、参数简化、模型的校准和验证等问题.利用CERES-Rice模型对作物模型在我国的区域应用进行了尝试并对部分参数进行了校准.首先利用田间观测数据在各实验点上对模型进行了详细的站点校准,以验证模型在我国的模拟能力;其次,以我国水稻种植区(精确到亚区)为单位,运用平均值和标准差(RMSE)两种方法进行了区域校准和验证,即找出能反映出品种空间差异的代表性品种参数集;然后分别运用两种方法的校准结果,模拟水稻产量和成熟期,并将模拟结果与实测值进行了比较.结果表明:区域校准能反映出水稻生育期和产量的时空变化规律,其中RMSE法较平均值法效果好.目前作物模型区域应用过程中还存在大量的误差来源,有待进一步研究.     

Revisiting Fisher: range size drives the correlation between variability and abundance of British bird eggs

We evaluate the correlation between intraspecific variation in egg size and population size in breeding British birds. Using information on abundance, range occupancy, migration status and phylogenetic relationships among species, we show that a wider geographical distribution rather than larger population size per se best predicts egg size variability. A similar result applies to wing length variability. Results from a phylogenetic path analysis suggest that geographical variation is the most parsimonious causal explanation for high intraspecific variation in common species.     

A population analysis of the variability of the hooklets in the cestode Triaenophorus crassus

The paper presents data on the variability of attachment organs in the cestode Triaenophorus crassus, a parasite of freshwater fishes. The greatest range of variability of all the characters is typical of whitefish, a fish with a long life cycle, while the shortest one is characteristic of vendace and young of trout. It is suggested that the stay of the parasite in fishes, associated with host age, is accompanied by the increase in average sizes of hooks and variability range. Such an approach together with the analysis of hooks variability gives the possibility to estimate the participation of secondary intermediate hosts in the circulation of the parasite in the water body.     

Intraspecific epigenetic polymorphism of the East European vole (Microtus levis Miller, 1908) in South-eastern Europe and Turkey

This study aims to represent the first report on population variation of 20 non-metric skull characters in East European vole (Microtus levis) from the Balkan (populations from Northern Dobruja; Southern Dobruja; East part of the Danube Plain; North-east Trace; Sofia field; South-east Trace) and Anatolian peninsulas (populations from North-west Anatolia region and Central Anatolia region), on the basis of which to determine its epigenetic variability and to analyse their mutual geographical epigenetic relations through comparison of the epigenetic divergence among them. Estimation of epigenetic variation of the studied populations of M. levis showed similar pattern of variation, but it is mostly higher than the other rodent species with a similar range of distribution, such as Microtus arvalis, Mus musculus, Apodemus sylvaticus, Apodemus flavicollis and Clethrionomys glareolus. Each one of the studied traits manifested some polymorphism. Moreover, all the calculated epigenetic distances (MMD) were statistically insignificant (P < 0.05) and epigenetic cranial uniqueness (MU) of any studied population was not found. These results reveal lack of expressed geographic relationship of population epigenetic variability in East European vole. The revealed populations epigenetic polymorphism of M. levis gives an opportunity for more complete assessment of variability and biological diversity of this species, but further research is necessary to elucidate its population epigenetics, especially as the data obtained in recent investigations of cranial morphology of the sibling species from the group the M. arvalis (sensu lato) added new locations to the distribution map of the East European vole in Eurasia.     

Polymorphism and mosaicism of B chromosome number in Korean field mouse <Emphasis Type="Italic">Apodemus peninsulae</Emphasis> (Rodentia) in the Russian Far East

A karyotype analysis of the Apodemus peninsulae (n = 355) from 41 trapping points from the Russian Far East has allowed us to identify B chromosomes in 87.9% of the animals, 61.7% of which are mosaics. Different levels of variability in the B chromosome numbers have been studied, including both the inter- and intrapopulational, as well as intraindividual variability (mosaicism). It was found that the frequencies of the occurrence of individuals with B chromosomes and mosaicism between different population samples were not constant. The range of the modal B chromosome number variability and variation of the xB index (zero to four; on average, the xB amounted to 1.67) were studied for the first time in different samples and populations of this species. Individuals with the predominant numbers of B chromosome (as a rule, zero to two) were revealed in both groups of animals (with stable and mosaic karyotypes), but the frequency was different in geographical regions. The spectra of B chromosome variability were wider in mosaics (zero to seven) compared to animals with stable karyotypes (zero to four). The importance of this for species of the high frequency of individuals with B chromosomes and with mosaicism has been discussed. The adaptive role of the low number of B chromosomes (one to two), as well as the imbalance of the B chromosome system for the species as a whole is assumed.