Survival of Breeding Pacific Common Eiders on the Yukon-Kuskokwim Delta,Alaska

ABSTRACT Populations of Pacific common eiders (Somateria mollissima v-nigrum) breeding in Alaska, USA, have declined markedly over the past 40 years. We studied survival of adult female Pacific common eiders using capture—recapture of nesting hens at 3 sites on the Yukon-Kuskokwim Delta (YKD), Alaska from 1994 to 2004. We used data consisting of 268 recapture events from 361 uniquely marked individuals to investigate temporal, geographic, and environmental variation in adult female survival. Our results suggest apparent annual survival of adult eiders from the YKD was high (0.892, SE = 0.022) and spatially and temporally invariant (σ² = 0.005), a pattern consistent with other long-lived marine birds. Moreover, our results suggest adult survival may be functionally fixed for Pacific common eiders, and at the present, adult survival may be relatively unresponsive to environmental or management perturbations. Our data did not support hypothesized variation in survival relative to mortality factors such as predation on breeding grounds, physiologic costs of reproduction, and wintering conditions. Although changes in adult survival likely have a large potential effect on prospective population growth, our results suggest viable management actions aimed at increasing survival may be extremely limited.     

Paracellular nutrient absorption in a gum-feeding new world primate, the common marmoset Callithrix jacchus

The common marmoset is one of the few callitrichid species that is not threatened or endangered in the wild, and is widely used in biomedical research, yet relatively little is understood about its digestive physiology. Dietary specialization on plant exudates has lead to relatively reduced small intestines, yet the common marmoset has exceptional dietary breadth, allowing it to successfully utilize a variety of habitats. We predicted that passive, paracellular nutrient absorption would be used by the common marmoset to a greater extent than in other non-flying mammals. We measured the bioavailability and rates of absorption of two metabolically inert carbohydrates not transported by mediated pathways (L-rhamnose and cellobiose, molecular masses of 164 and 342, respectively) to measure paracellular uptake, and of a non-metabolized D-glucose analog (3-O-methyl-D-glucose) to measure total uptake by both mediated and paracellular pathways. We found high bioavailability of 3-O-methyl-D-glucose (83+/-5%), and much higher bioavailability of the paracellular probes than in similarly sized non-flying mammals (30+/-3% and 19+/-2% for L-rhamnose and cellobiose, respectively). Passive, paracellular nutrient absorption accounts for around 30% of total glucose absorption in common marmosets and intestinal permeability is significantly higher than in humans, the only other species of primate measured to date. This may allow the common marmoset to maintain high digestive efficiency when feeding on higher quality foods (fruit, arthropods, gums with higher proportions of simple sugars), in spite of relatively reduced small intestines correlated with adaptations for fermentative digestion of plant gums. We find no evidence to support, in primates, the hypothesis that reliance on paracellular nutrient absorption should increase with body size in mammals, but suggest instead that it may be associated with small body size and/or taxon-specific adaptations to diet.     

How partnerships end in guillemots Uria aalge: chance events, adaptive change, or forced divorce?

Divorce in socially monogamous species can result from differentmechanisms, for example, chance events, active desertion ofthe partner, or the intrusion of a third individual oustingthe partner. We compared the predictions associated with suchmechanisms with data from common guillemots (Uria aalge) breedingon the Isle of May, Scotland. The data cover the years 1982–2005and show a yearly divorce rate of 10.2%. In most divorces (86%),one of the original partners moved to another breeding site,whereas the other bird stayed and bred with a new partner. Onaverage, movers had a significantly lower breeding success afterdivorce, stayers were largely unaffected, whereas the incomingbirds benefited significantly from the change. This patternfits best the predictions of the "forced-divorce" hypothesis,suggesting that many divorces were caused by incoming birdsrather than the original partners or chance events. Althoughwe are unable to document the precise behavioral sequence thatled to divorces, our interpretation is supported by observationsof frequent fights over breeding-site ownership. Our data alsoindicate within-population diversity of divorce mechanisms:some divorces were apparently accidental, others desertion ofpartners and sites if the latter were of low quality. Our studyfinally illustrates that a negative correlation between breedingsuccess and probability of divorce (which our data show) neednot indicate the adaptiveness of divorce for the original partners.Because such a connection has often been made, adaptive divorcemay in general be less common than usually assumed.     

Using sparse survey data to investigate the declining abundance of British harbour seals

This study presents an analysis of changes in the regional abundance of harbour seals Phoca vitulina based on repeated aerial surveys of haulouts, and demonstrates the use of sparse data to deliver advice about population status and management. Generalized linear models with negative binomial errors were used to represent these overdispersed data. The shape parameter of the negative binomial distribution was directly estimated from the data where this was possible. Information from time-series of counts where there were few gaps in the data was used to improve the estimation of this parameter in areas where fewer surveys had been carried out. The results show that the number of harbour seals in eastern England has not increased since the end of the 2002 phocine distemper epidemic. There is also evidence of a general decline in most of the large harbour seal colonies around Britain. The populations in the Inner Hebrides were an exception, with numbers appearing to be stable or increasing. Between 2001 and 2006, the population in Orkney and Shetland declined by 40% (95% confidence interval: 30–50%), indicating harbour seals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea.     

Climate change and range restriction of common salamanders in eastern Canada and the United States

The sensitivity of amphibian species to shifts in environmental conditions has been exhibited through long-term population studies and the projection of ecological niche models under expected conditions. Species in biodiversity hotspots have been the focus of ample predictive modeling studies, while, despite their significant ecological value, wide-ranging and common taxa have received less attention. We focused on predicting range restriction of the spotted salamander (Ambystoma maculatum), blue-spotted salamander (A. laterale), four-toed salamander (Hemidactylium scutatum), and red-backed salamander (Plethodon cinereus) under future climate scenarios. Using bias-corrected future climate data and biodiversity database records, we developed maximum entropy (MaxEnt) models under current conditions and for climate change projections in 2050 and 2070. We calculated positivity rates of species localities to represent proportions of habitat expected to remain climatically suitable with continued climate change. Models projected under future conditions predicted average positivity rates of 91% (89–93%) for the blue-spotted salamander, 23% (2–41%) for the spotted salamander, 4% (0.7–9%) for the four-toed salamander, and 61% (42–76%) for the red-backed salamander. Range restriction increased with time and greenhouse gas concentration for the spotted salamander, four-toed salamander, and red-backed salamander. Common, widespread taxa that often receive less conservation resources than other species are at risk of experiencing significant losses to their climatic ranges as climate change continues. Efforts to maintain populations of species should be focused on regions expected to experience fewer climatic shifts such as the interior and northern zones of species' distributions.     

日本海太平洋褶柔鱼生物学特征的年际变化

根据2010~2013年连续4个年度在日本海进行鱿钓生产采集的样本,利用SSPS软件统计拟合生长和Logistic曲线的方法,分析了太平样褶柔鱼(Todarodes pacificus)的胴长、体重、性别、性成熟度和摄食强度等生物学特征,以及日本海太平洋褶柔鱼群体结构和组成的年际变化。太平洋褶柔鱼总样本数量为388尾,其中雌、雄个体的平均胴长分别为231 mm和230 mm,优势胴长组为220~250 mm。各年度样本的雄雌性比均接近1︰1,总性比为0.89。胴长和体质量关系呈幂函数变化。Logistic曲线拟合个体初次性成熟胴长,其中雌性为216.04 mm,雄性为216.71 mm。样本以性成熟个体为主,成熟率(Ⅲ、Ⅳ和Ⅴ期)高达78.35%。摄食强度主要分布在Ⅰ、Ⅱ、Ⅲ等级,从胃含物组成的出现频率来看,以鱼类最高且主要是沙丁鱼类和灯笼鱼类,频率达70%以上;头足类次之,甲壳类较少。日本海太平洋褶柔鱼各年度的群落结构稍有差异,推测其生长发育与海洋环境因子有关,如温度、海流、盐度、饵料丰度等不同变化造成。     

Criteria for assessing maturity of skulls in the common dolphin,Delphinus sp., from New Zealand waters

Knowledge about the maturity status of specimens included in evolutionary, taxonomic or life history investigations is fundamentally important. This study investigated the use of the degree of cranial suture fusion, the developmental status of cranial bones, and the degree of tooth wear as indicators for cranial maturity status in Delphinus sp. from New Zealand waters. In total, 15 sutures, one joint and three nonmetric characters were assessed on 66 skulls obtained from stranded and bycaught individuals sampled between 1932 and 2011. A suture index (SI) was computed based on 10 sutures, in which degree of fusion was correlated with age and the three misclassification indices (MI), calculated for a given suture, were <50%. In addition to these, five premaxilla‐maxilla fusion and seven tooth wear categories were assessed. Results suggest that New Zealand Delphinus sp. skulls should be regarded as cranially mature if at least two of the following criteria are met: (1) individuals assessed as sexually mature, (2) aged ≥ 11 yr, (3) SI ≥ 8, and (4) premaxilla‐maxilla fusion ≥ 75% of the length of the dorsal side of the rostrum. Presence of any number of rostral teeth worn to the gum line provided further evidence for cranial maturity.     

丛枝菌根真菌对刺槐幼苗机械损伤响应机制的初步研究

通过对刺槐幼苗每隔3d剪去1片叶片造成持续机械损伤,测定了0~138h抗氧化酶活性变化及刺槐幼苗生长情况;同时使用孔径25μm尼龙网设置三室根箱隔网系统,测定了供体瞬时机械损伤后受体的抗氧化酶活性的持续变化,探讨接种丛枝菌根真菌刺槐幼苗对持续及瞬时机械损伤后的响应机制,以及菌根菌丝桥对刺槐幼苗机械损伤信号的传递特征。结果表明:在持续机械损伤胁迫下,接种丛枝菌根真菌能够促进刺槐幼苗的根系生长、提高幼苗的成活率,接种丛枝菌根真菌的刺槐幼苗成活率及根系鲜重比对照分别增加15.38%和23.52%。瞬时机械损伤后0、48、90、114、138h刺槐幼苗的苯丙氨酸解氨酶(PAL)和过氧化物酶(POD)活性都呈现先增加后降低的趋势,均在90h达到最大值,并且菌根化幼苗的PAL和POD活性显著高于未菌根化幼苗。瞬时机械损伤后,菌根菌丝桥能够介导刺槐幼苗间相关信号的传递,从而引起菌根化受体刺槐幼苗的PAL和POD活性表现出与供体机械损伤幼苗相同的变化趋势。