Isolation and characterization of di‐ and tetranucleotide microsatellite loci in the yellow‐spotted night lizard Lepidophyma flavimaculatum (Squamata: Xantusiidae)

We report the development of 17 di‐ and tetranucleotide microsatellite markers in the Yellow‐Spotted Night Lizard Lepidophyma flavimaculatum. Levels of heterozygosity ranged from 0 to 100%. Several loci also amplify in other Lepidophyma species and several species of the sister genus Xantusia. High levels of variation at some loci indicate that they will be useful for parentage assessment and population genetic studies, whereas the 15 loci that amplify across multiple Lepidophyma species suggest these will be useful in determining the origin of parthenogenetic populations.     

Extreme changes to gene expression associated with homoploid hybrid speciation

Hybridization is an important cause of abrupt speciation. Hybrid speciation without a change in ploidy (homoploid hybrid speciation) is well-established in plants but has also been reported in animals and fungi. A notable example of recent homoploid hybrid speciation is Senecio squalidus (Oxford ragwort), which originated in the UK in the 18th Century following introduction of hybrid material from a hybrid zone between S. chrysanthemifolius and S. aethnensis on Mount Etna, Sicily. To investigate genetic divergence between these taxa, we used complementary DNA microarrays to compare patterns of floral gene expression. These analyses revealed major differences in gene expression between the parent species and wild and resynthesized S. squalidus . Comparisons of gene expression between S. aethnensis , S. chrysanthemifolius and natural S. squalidus identified genes potentially involved in local environmental adaptation. The analysis also revealed non-additive patterns of gene expression in the hybrid relative to its progenitors. These expression changes were more dramatic and widespread in resynthesized hybrids than in natural S. squalidus , suggesting that a unique expression pattern may have been fixed during the allopatric divergence of British S. squalidus . We speculate that hybridization-induced gene-expression change may provide an immediate source of novel phenotypic variation upon which selection can act to facilitate homoploid hybrid speciation in plants.     

基于低成本聚甲基丙烯酸甲酯(PMMA)电泳芯片的微型DNA分析仪

在低成本的聚甲基丙烯酸甲酯(PMMA)电泳芯片上,利用双通道共聚焦激光诱导荧光检测系统实现了单链DNA快速高效的分离检测．选用0.8 mm厚度的PMMA薄片加工微管道,一方面降低了检测限,另一方面提高了散热性能．通过线性聚丙烯酰胺筛分胶液以及使用纤维素衍生物对微管道表面进行动态修饰等条件的优化,芯片完成了高分辨率、高重现性的短串联重复序列(STR)等位基因的快速分型检测．两个STR位点D13S317 和CSF1PO的等位基因分型标准物(allelic ladder)和实际样本的PCR扩增产物均在3 min内达到了基线分离,表明低成本的PMMA电泳芯片在法医学及临床医学领域的基因分析方面具有良好的发展潜能．     

Ecological change in British broadleaved woodland since 1947

Over the last 60 years Britain's broadleaved woodlands have undergone a complex pattern of ecological change. The total extent has expanded from c . 676 000 ha in 1947 to c . 904 000 ha in 2002, but there has also been significant turnover, with losses of ancient woodland and a gain from new planting. Structural change has occurred due, in part, to change in management. In 1947 21% of the broadleaved resource was classed as coppice, 28% as scrub and only 51% of the area as high forest, compared with 97% high forest in 2002. This has been accompanied by changes in ground flora and the regeneration pattern of tree species, which will impact upon the character of the woodlands. Woods have also become more ecologically isolated because of the decline in semi-natural vegetation in the surrounding countryside, although the long-term impacts of this are poorly understood. Other factors driving ecological change are increased pollution, change in grazing pressures, climate change, alien species and game management. Overall woodland specialist species and those of open habitats tend to be doing less well than woodland generalists. Progress has been made in reversing some adverse impacts such as acid deposition, and action is being taken to reduce the impact of others such as over-grazing by deer. However, some drivers, notably climate change, will be more difficult to address. In the long term integrated management of woods as landscape components whilst meeting economic and societal needs will be required.     

Modelling forest response to increasing CO2 concentration under nutrient-limited conditions

The growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of essential nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO₂ concentration, but it is uncertain whether this will translate into increased growth in the longer term under nutrient-limited conditions. An analytical model to address this question was developed by Comins & McMurtrie (1993, Ecological Applications 3, 666–681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assumptions and allowed a more confident prediction of expected growth responses to CO₂ enrichment under nutrient-limited conditions. The analysis indicated that conclusions about the CO₂ sensitivity of production were strongly influenced by assumptions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration proportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing CO₂ concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growth response to changing CO₂ concentration. On the other hand, predictions were only slightly affected by: (1) assumptions about the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the effects of nitrogen status on specific leaf area or (3) leaf longevity; (4) carbon allocation between different plant parts; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification of the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO₂ sensitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single-leaf photosynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen-limited conditions can respond to increasing atmospheric CO₂ concentration with considerable increases in growth.     

Carpenter Bee (Xylocopa micans) Risk Indifference and a Review of Nectarivore Risk-sensitivity Studies

This paper presents new results of risk-sensitive foraging studiesof the carpenter bee, Xylocopa micans, and reviews the workto date on risk sensitivity in nectarivores. In the field, nectarivoreschoose among alternative food sources (flowers) that differin the variabilities of their nectar rewards. In the lab, theforaging situation for carpenter bees was experimentally simplifiedby offering the bees a choice between either "low variance"or "high variance" artificial flowers. The two flower typesdiffered in their variabilities but offered the same expectedshortterm rates of net energy gain to test the predictions ofthe short-term rate maximization mechanism. Foragers were testedunder two energy budget conditions, hungry and well-fed, totest the predictions of the z-score model. Individual carpenterbees were indifferent to variability in both nectar volume andnectar sugar concentrations, and their risk-indifference wasunaffected by energy budget. These findings of risk indifferencesupport neither the variance discounting nor the z-score modelof risk sensitivity. Since the low and high variance flowertypes are equivalent for carpenter bees in short-term rate ofenergy gain, there can be no selection on carpenter bees tobe sensitive to variability based on differences in rate ofgain. Studies of risk sensitivity in honey bees and bumble beesusing variance in nectar concentration support this contention.These findings are compared with other nectarivore risk sensitivitystudies in order to highlight the most likely mechanisms underlyingaversion to variation in nectar rewards (short-term rate maximizing,the Weber-Fechner law of perception and learning non-empty flowers)and to suggest future research in the interplay of these threemechanisms.     

Photoperiod and Reproduction in Lobsters (Homarus)

SYNOPSIS. Photoperiodic control of lobster (Homarus) ovipositionranges from none in the European species (H. gammarus) to atwo-phase requirement in some populations of H. americanus.In the inshore population from Massachusetts two to three monthsof shortday photoperiod appear necessary to condition the ovaryfor final vitellogenesis following long-day onset (LDO). Thestimulus of LDO is only effective near the time of molt. Ifmolt follows LDO within 120 days, egg extrusion follows themolt in about 80 days. If LDO follows the molt, extrusion occursin about 125 days. Extrusion delayed in this way delays thefollowing molt, which is also delayed by the retention of eggson the pleopods. In lobsters from Prince Edward Island the photoperiodic responseseen at laboratory temperatures (ca. 14°C) appears to besubordinated to a response to other cues, probably temperature,when females are held on a near-natural temperature regime withwinter minimum of 2°C characteristic of inshore environments.H. americanus from the migratory outer continental shelf populationexperience winter temperatures rarely lower than 8°C andprobably require photoperiodic control to initiate migrationas well as vitellogenesis. The photoperiodic response may haveoriginated in offshore populations during the Pleistocene andspread to more northerly inshore areas as habitat opened afterthe retreat of the continental ice sheet.     

The Young Naturalists' Society and Natural History in the Northwest

SYNOPSIS. The beginnings of professional natural history inSeattle date from 1879. In this year a group of young men whowere completely untrained in the sciences formed the Young Naturalists'Society. The society quickly grew to eventually become a majorinstitution for natural history investigations in the PugetSound area at the end of the nineteenth century. The activitiesof the Young Naturalists included collecting a large and impressivecabinet, exchanging specimens with naturalists throughout theUnited States, organizing expeditions for marine investigations,and providing educational opportunities for the public throughlectures, public exhibits, newspaper reports, and summer Chautauqua.As the society became more professional in its work, it developedstrong ties to the University of Washington. In fact, by themid-1890s it was difficult to separate the natural history worksponsored by the University from the studies under the aegisof the Young Naturalists. Eventually the society disbanded andbecame absorbed by the various natural science departments ofthe University and by the Washington State Museum. The importanceof the Young Naturalists' was through its critical role in providingthe foundation for the development of a professional naturalhistory community in Seattle.     

The Conversion of 3-Indolylmethylglucosinolate to 3-Indolylacetonitrile by Myrosinase, and its Relevance to the Clubroot Disease of the Cruciferae

[Methylene-¹⁴C]-3-indolylmethylglucosinolate (¹⁴C-IMG) was convertedin vitro to [methylene-¹⁴Cl-3-indolylacetonitrile (¹⁴C-IAN)by myrosinase over a pH range of 4.0-6.0 and this conversionwas enhanced by ferrous ions. Other products of the reactionincluded 3-indolylmethanol, 3, 3'-diindolylmethane and ascorbigenA. Trace amounts of ¹⁴C-IAN were produced non-enzymically from¹⁴C-IMG in the presence of ferrous ion over a similar _pH range.Furthermore, swede tissues (Brassica napus cv. Danestone) infectedwith Plasmodiophora brassicae Woron. could convert ¹⁴C-IMG to¹⁴C-IAN. These results were consistent with the hypothesis thatthe overgrowth symptoms of the clubroot disease are caused bythe conversion of IMG to the auxin precursor IAN.