Strontium isotopes in Melanopsis sp. as indicators of variation in hydrology and climate in the Upper Jordan Valley during the Early-Middle Pleistocene, and wider implications

Aquifers dominated by Pleistocene basalts and Jurassic to Cretaceous calcareous rocks feed the Hula basin which is drained by the Jordan River into Lake Kinneret. The sedimentary sequence of Lower-Middle Pleistocene Benot Ya‘akov Formation (BYF) exposed by excavations of the 0.78 Ma lake-side site of Gesher Benot Ya‘aqov (GBY) consists of six cycles representing ca. 100 ka history of the Hula basin. This study characterizes the types of water sources in the catchment, tests the use of the Strontium (Sr) isotopes in the common extant snail Melanopsis sp. as a tracer for water in its habitat, and uses this tracer in the fossil specimens from GBY to investigate the palaeohydrology of the Hula paleolake during the corresponding period.The Sr isotope composition (⁸⁷Sr/⁸⁶Sr) of extant Melanopsis shells in the Hula catchment range widely (0.7046-0.7079). These analyses define distinct groups of water sources and aquifers, while the Jordan River at the GBY site has values around 0.70685. The values for fossil Melanopsis from GBY vary along stratigraphy; they are highest around 0.70710 in Cycles 1 and 2, decrease to around 0.70685 in Cycle 3, and exhibit upward trending fluctuations in the subsequent cycles to 0.70703 in Cycle 6. This trend reveals the dominance of the Hermon Jurassic aquifer during the earlier, colder periods before the Matuyama-Brunhes Boundary (MBB) and enhanced influence of the Golan basaltic aquifers, in subsequent warmer periods, indicating that the MBB coincides with climate warming as supported by other indicators. Hence, this global geochronological indicator of 0.78 Ma is also potentially a global palaeoclimatic marker. The similarity between the Sr isotope composition of the Jordan River waters and Melanopsis and those from Cycle 3 suggests that the current climate corresponds to that of the warmest period within the record of GBY, clarifying the comparative interpretation of this 100 k.yr. climate record.     

Speciation, diversity, and Mode 1 technologies: the impact of variability selection

Over geological timescales, organisms encounter periodic shifts in selective conditions driven by environmental change. The variability selection hypothesis suggests that increases in environmental fluctuation have led to the evolution of complex, flexible behaviours able to respond to novel and unpredictable adaptive settings. This hypothesis is tested via the framework of a single locus genetic model in which an invading ‘versatilist’ allele competes with two opposed specialists in a selection regime driven by a fluctuating environment, modelled initially as a sine wave and subsequently as an empirical climate curve covering the past 5 million years. Results demonstrate that generalist alleles achieve fixation in the sine wave environment, whilst versatilist alleles do so in the empirical environment, even at a range of very low fitness advantages over the basic generalist template. Variability selection is found to be a particularly strong force between approximately 2.5 and 1.2 Ma (millions of years ago). These results are discussed in relation to the spread of Oldowan lithics and the patterns of speciation and extinction documented in the hominin fossil record. It is suggested that the flexibility required for survival in a variable climatic regime may have been a stimulus to the development of the first stone tool technologies, whilst the ecological opportunities provided by heightened variability may have been a factor in prompting the hominin adaptive radiation evidenced during this period.     

Foliar nutrient dynamics in tidal and non-tidal freshwater forested wetlands

Foliar nutrient dynamics were studied at 8 forest stands (three non-tidal and five tidal) along the lower 30 km of the Apalachicola River system in Florida, USA, during 2008. At each site, we sampled canopy foliage and litterfall from three to four trees representative of the dominant overstory species. Foliage and litterfall were analyzed for a variety of elements including N and P and these data were used to examine differences in element concentrations, nutrient ratios (C:P, C:N, and N:P), nutrient use efficiency, and nutrient proficiency. Measurements of tree diameter at basal height (DBH) at each plot were used with species allometric equations to estimate forest litterfall dry weight and N and P flux in non-tidal and tidal wetlands. Both non-tidal and tidal wetlands showed evidence of P limitation based on N:P ratios, but absolute levels of P were determined to be extremely low in tidal wetlands based on higher nutrient use efficiencies (measures of both P resorption efficiency and proficiency). Differences in P concentrations and fluxes between tidal and non-tidal wetlands are probably related to longer inundation and hydrologic export observed in tidal wetlands. Using estimations of annual litterfall dry weight and nutrient concentrations, N and P flux in non-tidal swamps were 2-4 times greater than in tidal wetlands. This study demonstrates the change in nutrient dynamics as wetlands shift from tidal to non-tidal conditions.     

On the significance of structural vegetation elements for caterpillar thermoregulation in two peat bog butterflies: Boloria eunomia and B. aquilonaris

Purpose

Temperature profoundly impacts on distribution and habitat-use of organisms. The development of ectothermous caterpillars does not depend on host plant quality only, but also on the availability of suitable thermal conditions. Selection for thermally favorable microclimates (i.e. behavioral thermoregulation) is a primary mechanism of temperature control, and caterpillars can be either (or alternately) temperature conformers (i.e. passively adopting ambient temperature conditions) or thermoregulators (i.e. able to some extent to elevate or decrease their body temperature relative to ambient temperature). Here, we addressed the functional significance of different structural vegetation elements for the behavioral thermoregulation by caterpillars of two butterfly species.

Results

Weather conditions influenced the caterpillar detection probability within host plant patches, indicating that caterpillars can hide and use suitable microclimates provided by vegetation structures to cope with weather variations. This is why we (1) evaluated the heterogeneity in temperature conditions provided by these structures, (2) quantified the influence of ambient temperature and light intensity on caterpillar body temperature, and (3) tested how position on structure, substrate color and exposition influenced caterpillar body temperature. As expected, vegetation structures provided heterogeneous temperature and sun exposition conditions, while caterpillar body temperature was dependent on ambient temperature and light intensity. But body temperature was additionally influenced by the position on vegetation structures, substrate color and exposition.

Conclusions

These results suggest that there is no unique and fixed structure in the vegetation subsuming the best thermal conditions for caterpillars. We argue that a better understanding of the thermal properties of vegetation structures is essential for correctly understanding caterpillar habitat-use and the behavioral mechanisms driving their body thermoregulation. Conceptually this means that thermal conditions should be included in the definition of a species' functional habitat. Practically this may influence the choice of appropriate habitat management for species of conservation concern.     

Asexual reproduction, habitat colonization and habitat maintenance in bryophytes

Asexual reproduction s. l. is widespread in plants and also a basic reproductive mechanism in bryophytes. Today, three types of asexual reproduction are recognized: (1) the asexual reproduction s. str. by regeneration from ± specialized caducous organs (leaves, leaf apices, shoots, branches, bulbils) and by production of specialized propagules (gemmae, protonemal brood cells, tubers), (2) fragmentation of plants, resp. part of plants into ± unspecialized fragments, and (3) clonal reproduction (cloning). The latter occurs in bryophytes by protonema decay, by disintegration of modules, resp. formation of ramets (dividuals, “daughter plants”) that leads to self-cloning or forced-cloning of parts of the gametophyte (shoots, stoloniferous and rhizomatous axes, rhizoid wicks, basiscopic innovation plants). Clonal reproduction (cloning), in former time scarcely noted, gained great interest within the last decade mainly in vascular plants showing clonal growth. This reproduction mechanism is thought to be a keystone factor for asexual reproduction, habitat colonization and habitat maintenance. Species which reproduce clonally are able to colonize and maintain habitats in an effective way by the so-called “consequent vegetative multiplication”. The review presents an overview of the current state of knowledge of asexual reproduction types in bryophytes, with a focus on fragmentation and clonal reproduction (cloning), the mechanisms of habitat colonization and habitat maintenance, which all are of important significance in the dynamic processes of development of bryophyte populations.     

四川老君山自然保护区红翅噪鹛冬季栖息地特征

摘要：2010年1月和2011年1月,在四川老君山国家级自然保护区对红翅噪鹛（Garrulax formosus）的冬季栖息地特征进行了初步研究。在研究区内,红翅噪鹛冬季多集小群活动,主要选择次生林,而回避原生林和人工林。2个冬季在野外共遇见红翅噪鹛21群78只。通过比较分析,发现红翅噪鹛喜欢在海拔较低、坡位较高、坡向...     

内蒙古赛罕乌拉自然保护区狼的数量分布和食物组成

2006年1月至2008年12月,在内蒙古赛罕乌拉国家级自然保护区运用样线法和粪便分析法,对狼(Canis lupus)的生态分布和食物组成开展了研究。研究结果:保护区狼的数量至少7只,密度为(4.18±2.88)只/100km2,主要分布于保护区的圣山和庆云山核心区。在圣山主要活动于山脊、道路和沟谷;在庆云山主要活动于山脊。草兔(Lepus capensis)和植物在狼的食物组成中出现率最高,其食物组成在年度间存在显著差异(P<0.01),冬春与夏秋季节间差异不显著(P>0.05)。     

鸟类交通致死原因的种间行为差异分析(英文)

鸟类和其他动物经常死于车撞, 每年因车撞而死亡的个体可达数百万只。为什么有的物种比其他物种更易于死于车撞的问题,迄今未研究过。该文推测物种本身所具有的冒险行为可能是这些物种的某些个体更常死于车撞的一个原因。此外,不同物种个体在公路上的行为、个体数量、栖息地偏好、繁殖社会性以及健康状况都可能是影响个体车撞风险的潜在因素。2001—2006 年,对丹麦一个农村地区进行定期统计取样, 得到该地区不同种鸟类个体被车撞死事件发生的频率,以及周边环境中 50 种鸟类的个体数量数据, 并利用这些数据来检验我们的预测。车撞频率随鸟类个体数量线性增加和位于道路上或者低空飞越道路的个体所占比例增加,这两个因素几乎无法解释鸟类车撞频率差异。在考虑到丰富度这个因素后,发现那些鸟类惊飞距离短、面对潜在危险而更具有冒险性的物种个体更易遭遇车撞而亡。另外, 独居的物种、疟原虫感染率高的物种及因体型大而拥有大法氏囊的物种个体死于车撞的频率更高。这些发现表明, 一系列反映冒险行为、视敏度和健康状况的因子导致某些鸟类物种易受到车撞影响。     

Effect of great-horned owl trapping on chick survival in piping plovers

We studied the effect of great-horned owl (Bubo virginianus) removal on piping plover (Charadrius melodus) hatchling survival on Missouri River sandbars (2008–2009). Owl removal increased daily survival of piping plover chicks in 2008 (β = 2.03, 95% CI: 0.04–4.02), but this effect decreased with increasing age of the chick (β = −0.42, 95% CI: −0.81 to −0.03). Results for 2009 were similar in direction but not significant. Survival was higher in 2008 than in 2009, regardless of owl capture, indicating that even if owl capture consistently were effective at increasing survival, overall survival resulting from trapping may vary annually. Owl trapping was a successful means to raise chick survival on the Missouri River in ≥1 year and could be used at other sites experiencing depressed chick survival due to avian predators. © 2011 The Wildlife Society.     

Estimating multiple years,tributary-specific,and overall Atlantic salmon smolt abundance in a large Canadian catchment using capture–mark–recapture experiments

Population monitoring of Atlantic salmon (Salmo salar L.) abundance is an essential element to understand annual stock variability and inform fisheries management processes. Smolts are the life stage marking the transition from the freshwater to the marine phase of anadromous Atlantic salmon. Estimating smolt abundance allows for subsequent inferences on freshwater and marine survival rates. Annual abundances of out-migrating Atlantic salmon smolts were estimated using Bayesian models and an 18-year capture–mark–recapture time series from two to five trapping locations within the Restigouche River (Canada) catchment. Some of the trapping locations were at the outlet of large upstream tributaries, and these sampled a portion of the total out-migrating population of smolts for the watershed, whereas others were located just above the head of tide of the Restigouche River and sampled the entire run of salmon smolts. Due to logistic and environmental conditions, not all trapping locations were operational each year. Additionally, recapture rates were relatively low (<5%), and the absolute number of recaptures was relatively few (most often a few dozen), leading to incoherent and highly uncertain estimates of tributary-specific and whole catchment abundance estimates when the data were modeled independently among trapping locations and years. Several models of increasing complexity were tested using simulated data, and the best-performing model in terms of bias and precision incorporated a hierarchical structure among years on the catchability parameters and included an explicit spatial structure to account for the annual variations in the number of sampled locations within the watershed. When the best model was applied to the Restigouche River catchment dataset, the annual smolt abundance estimates varied from 250,000 to 1 million smolts, and the subbasin estimates of abundance were consistent with the spatial structure of the monitoring programme. Ultimately, increasing the probabilities of capture and the absolute number of recaptures at the different traps will be required to improve the precision and reduce the bias of the estimates of smolt abundance for the entire basin and within subbasins of the watershed. The model and approach provide a significant improvement in the models used to date based on independent estimates of abundance by trapping location and year. Total abundance and relative production in discrete spawning, nesting, or rearing areas provide critical information to appropriately understand and manage the threats to species that can occur at subpopulation spatial scales.