Multifactorial determination of skeletal age at death: a method and blind tests of its accuracy

Traditional methods of estimating skeletal age at death have relied solely on the pubic symphyseal face or on this indicator combined with others in nonsystematic ways. A multifactorial method is presented that uses a principal components weighting of five indicators (public symphyseal face, auricular surface, radiographs of proximal femur, dental wear, and suture closure). This method has been tested by completely blind assessment of age in two samples from the Todd collection carefully screened for accuracy of stated age at death. Results show a marked superiority of the multifactorial method over any single indicator with respect to both bias and accuracy. This represents the first truly blind test of an age-at-death indicator or system, as the test populations were independent of the system(s) being tested, and the age, sex, and ethnogeographic origin of the individuals being assessed (as well as the compositions of the test samples with respect to these variables) were completely unknown until the tests were completed. Implications for paleodemography are discussed.     

生境破坏的模式对集合种群动态和续存的影响

构建了空间关联的集合种群模型,该模型不但包含了种群的空间结构信息,而且引入了破坏生境的全局密度和局部密度两个指标,它们描述了破坏生境的模式.模型揭示了破坏生境的空间分布格局复杂地影响了集合种群的动态和续存,破坏和未破坏生境斑块的均匀混合不利于集合种群的增长和续存,而生境类型聚集分布可以促进集合种群的快速增长和长期续存;对于两种斑块类型相对均匀混合的生境来说,均匀场假设可能会高估集合种群的续存,对于相对斑块类型高度聚集的生境,均匀场假设可能会低估集合种群的续存;物种的迁移范围也会影响集合种群的续存,迁移范围越大的物种越容易抵御生境的破坏而免遭灭绝.这意味着在生物保护中不能仅仅考虑生境的恢复和斑块质量的改善,生境结构的构建也是很重要的,加强生境斑块之间的连通性也有利于物种的长期续存.     

The flowering pattern of the perennial herb Lobularia maritima: an unusual case in the Mediterranean basin

In plant communities of the Mediterranean Basin most plant species reach their blooming peak in spring and have characteristically short flowering periods of two-three months. The perennial herb Lobularia maritima represents an exception to these characteristics, because it flowers for almost 10 months, and has its flowering peak in autumn. In this five-year study, we describe the flowering pattern of L. maritima at the population and community levels. Despite the unusually extended flowering period of L. maritima, the species showed characteristic low among-year variability in the length of the flowering period but large interannual variation in the distribution of flowers throughout the flowering period. The flowering pattern (unimodal or bimodal) of L. maritima individuals differed among the five years, suggesting that L. maritima plants are plastic enough to tailor their flowering to variable environmental conditions. We conclude that flowering phenology of L. maritima represents a very particular case in the plant community studied, and the influence of abiotic and biotic factors on the phenology of this species is discussed.     

Radiographic changes in the clavicle and proximal femur and their use in the determination of skeletal age at death

Visually seriated radiographs of the proximal femur, proximal humerus, clavicle, and calcaneus from 130 individuals from the Hamann-Todd collection were examined as indicators of skeletal age at death. The clavicle demonstrated the most consistent relationship to age in both sexes. The same radiographs were also seriated by size-normalized optical density as a means of establishing relative radiolucency. In this context, visual seriation proved superior. The four sites studied showed strong divergence in response to age. Since each was sampling bone response from the same individual, it is concluded that bone loss is highly site specific. This demonstrates the individual character of specific skeletal sites. Visual inspection of clavicular radiographs, seriated on a populational basis, provides age estimates that are comparable to anatomical age indicators and provides independent estimates of skeletal age when included in the summary age method (1985: Am. J. Phys. Anthropol. 68:1–14).     

Dynamics in a butterfly–plant–ant system: influence of habitat characteristics on turnover rates of the endangered lycaenid Maculinea alcon

Abstract.  1.  Maculinea alcon , a myrmecophilic, stenotopic lycaenid butterfly is restricted to wet heathlands, bogs, and nutrient-poor hay meadows. Due to intensification of agriculture and decrease of extensively grazed meadows, many suitable habitats have disappeared and the remaining ones are highly fragmented and deteriorated.
2. Historical distribution data and a comparison with the present occupation of patches show the decline of this critically endangered butterfly in north-west Germany. Most of the populations in north-west Germany are small and often geographically isolated.
3. In summer 2002, two-thirds of 77 investigated potential patches were unoccupied as a result of unsuitable habitat structure and habitat fragmentation.
4. Several habitat parameters were highly significantly correlated with the presence of M. alcon , in particular the distribution pattern of the host plant Gentiana pneumonanthe. Furthermore, butterflies were absent from many patches with an incidence probability below 50% with respect to patch size and isolation.
5. In the nature reserve Lüneburger Heide, part of the study area, M. alcon populations have been observed since 1995. Typical turnover of local populations could be detected during these years. Extinctions and re-colonisations have stabilised the presence of this species in a metapopulation in this nature reserve.
6. These data show the importance of different factors on different spatial levels influencing the presence of this endangered butterfly.     

Modelling single nucleotide effects in phosphoglucose isomerase on dispersal in the Glanville fritillary butterfly: coupling of ecological and evolutionary dynamics

Dispersal comprises a complex life-history syndrome that influences the demographic dynamics of especially those species that live in fragmented landscapes, the structure of which may in turn be expected to impose selection on dispersal. We have constructed an individual-based evolutionary sexual model of dispersal for species occurring as metapopulations in habitat patch networks. The model assumes correlated random walk dispersal with edge-mediated behaviour (habitat selection) and spatially correlated stochastic local dynamics. The model is parametrized with extensive data for the Glanville fritillary butterfly. Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile. The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency. First, at the level of local populations, the frequency of the C allele is the highest in newly established isolated populations and the lowest in old isolated populations. Second, at the level of sub-networks with dissimilar numbers and connectivities of patches, the frequency of C increases with decreasing network size and hence with decreasing average metapopulation size. The frequency of C is the highest in landscapes where local extinction risk is high and where there are abundant opportunities to establish new populations. Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa.     

The relative importance of sexual and clonal reproduction for population growth in the perennial herb Fragaria vesca

The relative importance of sexual and clonal reproduction for population growth in clonal plants is highly variable. Clonal reproduction is often more important than sexual reproduction but there is considerable interspecific variation and the importance of the two reproductive modes can change with environmental conditions. We carried out a demographic study on the woodland strawberry (Fragaria vesca), a widespread clonal herb, at 12 sites in Switzerland during 2 years. Study sites were selected in two different habitats, i.e., forest and forest edge. We used periodic matrix models to estimate annual population growth rates and carried out prospective analyses to identify life cycle components that influence population growth rates most. Retrospective analyses were applied to study how the two different habitats affected population dynamics. Furthermore, we tested whether trade-offs between sexual and clonal reproduction occurred. There were large differences in annual population growth rates between sites and large within-site differences between years. Results of the prospective analyses clearly indicate that clonal reproduction is the dominant reproductive pathway whereas sexual reproduction is rather insignificant for population growth. Compared to forest habitats, forest edge habitats had higher population growth rates in the first year but smaller growth rates in the second year. We attribute these differing habitat effects to different water availabilities during consecutive years. No trade-offs between sexual and clonal reproduction were found. In conclusion, population growth of F. vesca relies heavily on clonal reproduction. Furthermore, reproduction and survival rates of F. vesca depend highly on spatio-temporal variation of environmental conditions.     

北盘江光唇裂腹鱼年龄结构、生长特征和生活史类型

光唇裂腹鱼(Schizothorax lissolabiatus)主要分布于珠江水系南北盘江、元江、澜沧江和怒江等。以2008-2009年在北盘江采集的261尾光唇裂腹鱼为材料,研究了光唇裂腹鱼的年龄和生长特征。选用鳞片作为年龄鉴定的主要材料,并结合主鳃盖骨、匙骨、背鳍条等材料,对光唇裂腹鱼个体进行了年龄鉴定。结果表明:这4种材料年龄鉴定结果趋于一致,吻合性高。光唇裂腹鱼体长与鳞径的最佳函数关系为线性函数L=20.202R+65.726,体长与体重的最佳拟合方程呈幂函数关系W=4×10-5L2.8208。Von Bertalanffy方程、Logistic方程、Gompertz方程均为光唇裂腹鱼拟合性较好的生长方程,并以Von Bertalan-ffy方程的拟合度最高;光唇裂腹鱼Von Bertalanffy生长方程为:Lt=475.51[1-e-0.138(t+1.1397)],Wt=1424.93[1-e-0.138(t+1.1397)]2.8208;体重生长拐点为6.37龄。1~4龄为光唇裂腹鱼生长的快速阶段,而5龄以上个体的生长速度明显降低。根据r-选择和k-选择的典型特征以及渐近体长(L∞)、渐近体...     

Fine-scale genetically based differentiation of life-history traits in the perennial shrub Lupinus arboreus

Across large spatial scales, plants often exhibit genetically based differentiation in traits that allow adaptation to local sites. At smaller spatial scales, sharp boundaries between edaphic conditions also can create strong gradients in selection that counteract gene flow and result in local adaptation. Few studies, however, have examined the degree to which continuous populations of perennial plants exhibit genetically based differentiation in life-history traits over small spatial scales. We quantified the degree of genetically based differentiation in adaptive traits among bush lupine (Lupinus arboreus) from nearby dune and grassland sites (sites separated by < 0.75 km) that formed part of a larger continuous population of L. arboreus. We also investigated the spatial genetic structure of bush lupine by examining how genetic structure differed between seeds and juvenile plants that were less than two years old. We calculated F-statistics from gel electrophoresis of 10 polymorphic loci. We then used these values to infer levels of gene flow. To examine differentiation in adaptive traits, we created full-sibling/half-sibling families of lupine within each area and established reciprocal common gardens at each site. Across two years, we measured canopy volume, flowering time, seed set, and mortality of progeny planted in each garden. Spatial genetic structure among seeds was virtually nonexistent (F(ST) = 0.002), suggesting that gene flow between the three areas could be quite high. However, genetic structure increased 20-fold among juvenile plants (F(ST) = 0.041). We found strong evidence for fine-scale genetically based differentiation and local adaptation in adaptive traits such as plant size, flowering phenology, fecundity, and mortality. Thus, it is likely that strong but differing selection regimes within each area drive spatial differentiation in lupine life-history traits.     

Development and multiplexing of microsatellite markers in the polyploid perennial herb, Menyanthes trifoliata (Menyanthaceae)

• Premise of the study: We developed microsatellite primers to investigate genetic diversity and population genetic structure of the endangered herb Menyanthes trifoliata. • Methods and Results: Using the microsatellite-enriched library method, we identified 10 primer pairs in M. trifoliata. The primers amplified nine di- and one tri-nucleotide repeats with 4–13 alleles per locus in two Belgian populations. • Conclusions: The results indicate that these markers offer an appropriate amount of variation to investigate genetic diversity, pollen dispersal (through paternity inference), and other conservation issues.     

Intrabasin variations in age and growth of bullhead: the effects of temperature

The variability of growth variables and age structure in bullhead Cottus gobio was studied in a single river catchment by comparing populations inhabiting river reaches with different thermal regimes. Age and growth variables were determined by examining 540 sagittal otoliths from specimens ranging between 19 and 146 mm total length. Growth of young bullhead (0+ and 1+ years) was higher in the warmest sites, especially in relation to water temperature during the growing season (spring and summer). Growth of older bullhead (2+ to 5+ years) was negatively related to mean water temperature of the site. The growth performance of bullhead over its whole life cycle was negatively correlated with water temperature, which could be partly explained by a higher energy allocation to reproduction in the warmest sites. Life span was longer in the colder sites (7 years) than in the warmer ones (4 or 5 years), and bullhead matured earlier in the warmer sites (age 1+ or 2+ years) compared to the colder ones (age 2+ or 3+ years). These results, combined with previous data on reproductive traits, suggest the possible effects that global warming could have on bullhead population dynamics.     

Population dynamics and spatial arrangement of Ranunculus glacialis L., an alpine perennial herb,in permanent plots

In 1986 sixteen permanent plots (625 cm² each) were established in scree slopes dominated by Ranunculus glacialis at Mt. Glungezer, Austria (2600 m elevation) in order to document the population dynamics of herbaceous perennials near the upper altitudinal limits of plant existence. The abundance and sizes of individual R. glacialis shoots, their leaf numbers and reproductive status were evaluated over a 6-year period. On South-facing slopes the population sizes of adult and juvenile shoots remained constant over the years, while seedling numbers fluctuated significantly. Overall density of all developmental stages of R. glacialis was significantly lower on North-facing slopes and year-to-year fluctuations were greater, than on thermally-favorable Southern slopes. The spatial pattern of adult shoots and seedlings was clumped, while juvenile shoots had a random or clumped distribution. Fertilization had no effects on population dynamics. Proposed greenhouse effects, e.g. increases in CO₂ and temperature, should result in population growth on North-facing slopes and may increase mortality on South-facing sites.     

Population structure and gene flow reversals in Atlantic salmon (Salmo salar) over contemporary and long-term temporal scales: effects of population size and life history

Metapopulation dynamics are increasingly invoked in management and conservation of endangered species. In this context, asymmetrical gene flow patterns can be density dependent, with migration occurring mainly from larger into smaller populations, which may depend on it for their persistence. Using genetic markers, such patterns have recently been documented for various organisms including salmonids, suggesting this may be a more general pattern. However, metapopulation theory does not restrict gene flow asymmetry to 'source-sink' structures, nor need these patterns be constant over longer evolutionary timescales. In anadromous salmonids, gene flow can be expected to be shaped by various selective pressures underlying homing and dispersal ('straying') behaviours. The relative importance of these selective forces will vary spatially and for populations of different census size. Furthermore, the consequences of life-history variation among populations for dispersal and hence gene flow remain poorly quantified. We examine population structure and connectivity in Atlantic salmon (Salmo salar L.) from Newfoundland and Labrador, a region where populations of this species are relatively pristine. Using genetic variation at 13 microsatellite loci from samples (N=1346) collected from a total of 20 rivers, we examine connectivity at several regional and temporal scales and test the hypothesis that the predominant direction of gene flow is from large into small populations. We reject this hypothesis and find that the directionality of migration is affected by the temporal scale over which gene flow is assessed. Whereas large populations tend to function as sources of dispersal over contemporary timescales, such patterns are often changed and even reversed over evolutionary, coalescent-derived timescales. These patterns of population structure furthermore vary between different regions and are compatible with demographic and life-history attributes. We find no evidence for sex-biased dispersal underlying gene flow asymmetry. Our findings caution against generalizations concerning the directionality of gene flow in Atlantic salmon and emphasize the need for detailed regional study, if such information is to be meaningfully applied in conservation and management of salmonids.     

Ecophysiology of embryo development and seed germination of the European woodland herbaceous perennial Corydalis cava (L.) Schweigg. & Körte subsp. cava (Fumariaceae)

In this study we examined the germination ecology with special reference to the temperature requirements for embryo development and germination of Corydalis cava subsp. cava, under both outdoor and laboratory conditions. Corydalis cava is a spring flowering woodland tuberous geophyte widely distributed across Europe. Germination phenology, including embryo development and radicle and cotyledon emergence, was investigated in a population growing in northern Italy. Immediately after harvest, seeds of C. cava were sown both in the laboratory under simulated seasonal temperatures and naturally. Embryos, undifferentiated at the time of seed dispersal, grew during summer and autumn conditions, culminating in radicle emergence in winter, when temperatures fell to ca 5°C. Cotyledon emergence also occurred at ca 5°C, but first emergence was delayed until late winter and early spring. Laboratory experiments showed that high (summer) followed by medium (autumn) and low temperatures (winter) are needed for physiological dormancy loss, embryo development and germination respectively. Unlike seeds of C. cava that germinated in winter, in other Corydalis species radicle emergence occurred in autumn (C. flavula) or did not depend on a period of high summer temperature to break dormancy (C. solida). Our results suggest that subtle differences in dormancy and germination behavior between Corydalis species could be related to differences in their geographical distribution.