Dealing with Uncertainty in Spatially Explicit Population Models

It has been argued that spatially explicit population models (SEPMs) cannot provide reliable guidance for conservation biology because of the difficulty of obtaining direct estimates for their demographic and dispersal parameters and because of error propagation. We argue that appropriate model calibration procedures can access additional sources of information, compensating the lack of direct parameter estimates. Our objective is to show how model calibration using population-level data can facilitate the construction of SEPMs that produce reliable predictions for conservation even when direct parameter estimates are inadequate. We constructed a spatially explicit and individual-based population model for the dynamics of brown bears (Ursus arctos) after a reintroduction program in Austria. To calibrate the model we developed a procedure that compared the simulated population dynamics with distinct features of the known population dynamics (=patterns). This procedure detected model parameterizations that did not reproduce the known dynamics. Global sensitivity analysis of the uncalibrated model revealed high uncertainty in most model predictions due to large parameter uncertainties (coefficients of variation CV 0.8). However, the calibrated model yielded predictions with considerably reduced uncertainty (CV 0.2). A pattern or a combination of various patterns that embed information on the entire model dynamics can reduce the uncertainty in model predictions, and the application of different patterns with high information content yields the same model predictions. In contrast, a pattern that does not embed information on the entire population dynamics (e.g., bear observations taken from sub-areas of the study area) does not reduce uncertainty in model predictions. Because population-level data for defining (multiple) patterns are often available, our approach could be applied widely.     

居群（population）概念和方法在植物分类学中的应用

本文依据我们近几年来对水生维管束植物的研究成果,讨论了居群概念和方法对植物分类学的理论和实际的意义与价值,同时对我国今后展开植物学研究提出了若干建议。     

Individual admixture estimates: disease associations and individual risk of diabetes and gallbladder disease among Mexican-Americans in Starr County, Texas

The ethnic and geographic distributions of several common chronic diseases show distinct patterns that are consistent with the distribution of genes and genetic admixture. For example, diabetes and gallbladder disease occur most frequently among Amerindians, while those genetically admixed with them (such as Mexican-Americans) have intermediate rates, and lowest rates are found among Whites and Blacks. Because there will be heterogeneity from individual to individual in ancestral affinity within an admixed population, a method is developed for estimating each person's admixture probability. Results confirm that there is substantial heterogeneity of individual admixture among Mexican-Americans in Starr County, Texas, with a mean value indicating that 65% of genes in this population are Caucasian derived and 35% Amerindian derived. The individual estimates are shown to be unrelated to the probability of being diabetic and only marginally related to gallbladder disease, with those having the most Amerindian affinity being at increased risk. These results are a consequence of the independent assortment of loci and indicate that unless the markers employed are related (including linkage) to the disease of interest, the method will have limited utility. Individual admixture estimates will be useful, however, for examining aspects of population structure and will find increased utility for predicting disease and examining disease associations as more and more of the genome is represented by markers, a very probable prospect with the abundance of DNA polymorphism being identified by restriction enzymes.     

进展期胃癌p53表达与微血管密度及生物学行为的关系

目的探讨进展期胃癌生长过程中p53基因表达与微血管密度和生物学行为之间的关系。方法搜集有随访资料的胃癌标本107例,用免疫组化对突变型p53和CD34作了标记,用原位杂交对野生型p53作了检测。结果突变型p53在肿瘤不同侵犯深度、不同生长方式、不同淋巴结转移状态以及预后方面,存在显著差异(P<0.05),突变型p53与微血管密度显著相关(P<0.05),而野生型p53则与突变型p53相反。结论突变型和野生型p53在肿瘤生长过程中的表达不同,说明p53的不同功能状态在肿瘤的发展过程中发挥重要作用。     

甘肃东大山自然保护区岩羊生态行为的初步观察

2004年7月和8月,通过样线调查、野外直接跟踪观察和瞬间取样的方法,对东大山自然保护区岩羊(Pseudois nayaur)的种群结构和生态行为进行了初步研究。在观察到的720只岩羊中,719只组成了50个群,最大的群82只,最小的群2只,平均群大小(14.38±15.83)只(n=50)。雌雄性比为1∶0.63,成年雌体、亚成体和幼体之比是1∶0.4∶0.24。岩羊的昼间活动中,上午和下午各有一个瞬间觅食高峰,分别在6:30时和15:30时,中午有一段较长时间的休息期。通过对一个46只岩羊群连续12 d的野外跟踪观察,发现该岩羊群昼间的活动范围基本上在1.47 km2内。对152个自然死亡的雄性岩羊头骨的分析表明,东大山雄性岩羊的自然死亡年龄在7.5~11.5龄,其中9.5龄是其自然死亡的高峰。     

Plasma Adiponectin Levels and Metabolic Factors in Nondiabetic Adolescents

Objectives: The relationship of plasma adiponectin levels with various anthropometric and metabolic factors has been surveyed extensively in adults. However, how plasma adiponectin levels are related to various anthropometric indices and cardiovascular risk factors in adolescents is not as vigorously studied. In this study, we investigated this among healthy nondiabetic adolescents. Research Methods and Procedures: Two hundred thirty nondiabetic subjects (125 boys and 105 girls, ～10 to 19 years old) were included. The plasma adiponectin, fasting plasma glucose, insulin, lipids and anthropometric indices including body height, weight, waist circumference, and hip circumference were examined. Body fat mass (FM) and percentage were obtained from DXA scan. The homeostasis model assessment was applied to estimate the degree of insulin resistance. Results: The plasma adiponectin levels were significantly higher in girls (30.79 ± 14.48 μg/mL) than boys (22.87 ± 11.41 μg/mL). The plasma adiponectin levels were negatively related to BMI, FM, FM percentage, waist circumference, waist‐to‐hip ratio, insulin resistance, plasma insulin, triglycerides, and uric acid levels, but positively with high‐density lipoprotein cholesterol (HDL‐C) with the adjustment for age and gender. Using different multivariate linear regression models, only age and HDL‐C were consistently related to the plasma adiponectin levels after adjustment for the other variables. Discussion: The relationship between plasma adiponectin and various anthropometric indices and metabolic factors, especially HDL‐C, previously reported in adults was present in the healthy nondiabetic adolescents. Whether variation of plasma adiponectin levels in healthy nondiabetic adolescents may influence their future coronary artery disease risk warrants further investigation.     

The regeneration niche of the grey mangrove (Avicennia marina): effects of salinity,light and sediment factors on establishment,growth and survival in the field

Field observations of seedlings and saplings of Avicennia marina showed patterns that correlated with salinity, light and sediment. Models that account for these observations were subsequently tested in a series of field experiments. Establishment varied within an estuary under controlled conditions but was not related to salinity or sediment type. Seedling survival was uniform over 3 years regardless of position in estuary and sediment type. Seedling densities and survival under canopies or in canopy gaps were not significantly different. However, seedling growth and density of saplings were greater in canopy gaps. Experiments involving manipulations of canopies showed no differences in seedling survival under canopies or in light gaps, but addition of slow-release fertilizer enhanced growth and survival in canopy gaps and under canopies. Long-term comparison of areas denuded of a canopy and with sediment disturbance showed enhanced establishment and survival when compared with areas with canopy gaps but with undisturbed sediments. Overall there appears to be no restriction to establishment of propagules within mangrove stands other than the supply of propagules and tidal or wave action. In contrast, recruitment to the sapling stage appears to be restricted by light and sediment resources. We suggest that propagules need to establish in a regeneration niche for seedling recruitment to the sapling stage. This differs from the view that seedlings in the under-storey are analogous to a seed pool in the soil.     

Crossing to safety: dispersal,colonization and mate choice in evolutionarily distinct populations of Steller sea lions,Eumetopias jubatus

Population growth typically involves range expansion and establishment of new breeding sites, while the opposite occurs during declines. Although density dependence is widely invoked in theoretical studies of emigration and colonization in expanding populations, few empirical studies have documented the mechanisms. Still fewer have documented the direction and mechanisms of individual transfer in declining populations. Here, we screen large numbers of pups sampled on their natal rookeries for variation in mtDNA (n = 1106) and 16 microsatellite loci (n = 588) and show that new Steller sea lion breeding sites did not follow the typical paradigm and were instead colonized by sea lions from both a declining (Endangered) population and an increasing population. Dispersing individuals colonized rookeries in the distributional hiatus between two evolutionarily distinct ( = 0.222,  = 0.053, K = 2) metapopulations recently described as separate subspecies. Hardy–Weinberg, mixed‐stock and relatedness analysis revealed levels of interbreeding on the new rookeries that exclude (i) assortative mating among eastern and western forms, and (ii) inbreeding avoidance as primary motivations for dispersal. Positive and negative density dependence is implicated in both cases of individual transfer. Migration distance limits, and conspecific attraction and performance likely influenced the sequence of rookery colonizations. This study demonstrates that resource limitation may trigger an exodus of breeding animals from declining populations, with substantial impacts on distribution and patterns of genetic variation. It also revealed that this event is rare because colonists dispersed across an evolutionary boundary, suggesting that the causative factors behind recent declines are unusual or of larger magnitude than normally occur.