Kanab ambersnail and other terrestrial snails in south central Utah

Surveys for succineid snails were conducted to improve genetic and geographical information for the endangered Kanab ambersnail ( Oxyloma haydeni kanabensis Pilsbry) and related taxa within the Succineidae. Surveys were carried out in the Bureau of Land Management Kanab District, at the Grand Staircase Escalante National Monument, on 3 private holdings, and along Highways 89, 12, and 14, all in south central Utah. A population of Kanab ambersnails was known to exist in the region; other populations of Oxyloma were discovered in primarily seep-fed wetlands in Kanab Creek and in tributaries of and wetlands along the Virgin, Sevier, and Escalante rivers in Kane, Garfield, and Piute counties. None of the newly discovered populations was identified as Kanab ambersnail on the basis of anatomical evidence, although one was at the type locale for that species. We list other snail species encountered and discuss the status of the Kanab ambersnail in light of recent genetic research.     

Experimental manipulations of fertile islands and nurse plant effects in the Mojave Desert, USA

In a mixed desert shrub community we removed and added shrub canopies to examine above- and belowground influences of 3 species of shrubs on islands of soil fertility and the survival of transplanted Ambrosia dumosa seedlings. Soils sampled under shrubs in the wet season had higher pH, water content, organic matter, and both total and mineralizable nitrogen than soils in adjacent open areas, confirming a widely established pattern in arid lands. However, we also found species differences in soil parameters. Soils under Coleogyne ramosissima had highest pH, soils under A. dumosa had highest water content and nitrogen mineralization rates, and soils under Larrea tridentata had lowest water content. Soils sampled under shrubs in the dry season, 7 months after experimental shrub removal, maintained higher organic matter and total and mineralizable nitrogen content than adjacent open soils, but pH and water were altered by shrub manipulations. Species differences persisted only in soil water levels ( A. dumosa soils were driest). Over a 1-year period, transplanted A. dumosa seedlings had highest survivorship in shrub removal and open treatments and died most rapidly under control shrubs of all 3 species, suggesting that shrubs had a strong negative effect on seedling survival, even in the presence of higher organic matter, nutrients, and (initially) higher water content of fertile islands. Our results suggest that nurse plants and islands of soil fertility have the potential to facilitate growth of other species by nutrient additions, but that the net effect of nurse plants can be negative due to shading and/or root competition.     

Melanoma genome sequencing reveals frequent PREX2 mutations

Melanoma is notable for its metastatic propensity, lethality in the advanced setting and association with ultraviolet exposure early in life. To obtain a comprehensive genomic view of melanoma in humans, we sequenced the genomes of 25 metastatic melanomas and matched germline DNA. A wide range of point mutation rates was observed: lowest in melanomas whose primaries arose on non-ultraviolet-exposed hairless skin of the extremities (3 and 14 per megabase (Mb) of genome), intermediate in those originating from hair-bearing skin of the trunk (5-55 per Mb), and highest in a patient with a documented history of chronic sun exposure (111 per Mb). Analysis of whole-genome sequence data identified PREX2 (phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 2)--a PTEN-interacting protein and negative regulator of PTEN in breast cancer--as a significantly mutated gene with a mutation frequency of approximately 14% in an independent extension cohort of 107 human melanomas. PREX2 mutations are biologically relevant, as ectopic expression of mutant PREX2 accelerated tumour formation of immortalized human melanocytes in vivo. Thus, whole-genome sequencing of human melanoma tumours revealed genomic evidence of ultraviolet pathogenesis and discovered a new recurrently mutated gene in melanoma.     

香港蒲苔群岛植物物种多样性与植被的研究

通过实地调查,对香港蒲苔群岛的植物物种多样性进行了研究.据统计蒲苔群岛共有维管束植物245种,隶属于93科203属,其中有国家及香港政府保护植物5种.植被类型主要有灌丛、次生性季风常绿阔叶林、红树林和海边沙滩植物群落等.蒲苔群岛植物区系以热带亚热带区系成分占优势.报导了蒲苔群岛各岛植物名录,并初步分析了各岛植物物种多样性的特点,同时对蒲苔群岛野生植物保育及旅游开发提出了建议.     

鲁克沁构造带稠油成藏机制研究

吐哈盆地台南凹陷鲁克沁构造带中的北西走向断层受挤压强烈 ,封闭性好 ;而北东走向断层封闭性差 ,常成为油气运移的良好通道。由于本区断块圈闭的有效性差 ,故不具备大规模聚集稀油的条件 ,但对稠变到一定程度的稠油能起较好的封堵作用。鲁克沁构造带高粘重质油的形成是原油运移和成藏阶段双重稠变作用的结果 ,并且油气的聚集是一个动态的过程。随着原油的逐渐稠变 ,所需要的封堵条件逐渐降低 ,油气的聚集过程才趋于稳定。鲁克沁构造带构造后期变革主要表现在构造幅度的增大 ,而未发生强烈的断裂作用 ,因此 ,前侏罗系油藏得以完好地保存