Habitat suitability for tsessebe Damaliscus lunatus lunatus

The distribution and numbers of tsessebe (Damaliscus lunatus lunatus) have declined considerably in South Africa, partly due to deteriorating habitat conditions. Identifying important habitat variables will assist in managing the species. The objective of this study was to identify habitat variables important for tsessebe and to develop a predictive model of habitat selection for this species in a savanna biome. The study was conducted in the Nylsvley Nature Reserve over a 2‐year period. A total of eighteen habitat variables were measured in ten plant communities at 200 sites. Logistic regression analyses were used to identify predictor variables and to construct a habitat model. Tsessebe were found <2 km from the nearest source of water, in flat areas with slopes of <3° and with <10% rockiness. Their distribution was not influenced by the woody component. Sites where tsessebe were present had significantly lower grass heights and tuft heights, with a higher grass density compared with areas not utilized by tsessebe. Nitrogen and sodium levels were also higher at present sites. Habitat type and grass height were the most significant predictors of tsessebe presence. The selected model had an overall percentage prediction of 85.0%. The model was subdivided into five vegetation‐specific models and each model was tested with independent data.     

Habitat stability and the larval mosquito community in treeholes and other containers on a temperate Island

The temporal fluctuation of water levels and the presence of mosquito larvae were investigated for four types of small container habitats (treeholes, bamboo stumps, cemetery stone vases, and cemetery stone vessels) on Kabeshima Island in Kyushu, southwestern Japan. The probability that containers held water was positively correlated with the quantity of the preceding rainfall and with the depth and volume of the containers. It was estimated that dehydration occurred more regularly in autumn and winter than in summer. The probability that mosquito larvae were present in each type of container was positively correlated with habitat stability in terms of the probability of the existence of standing water and the coefficient of variation of the water level. Twelve species of mosquito larvae, including two rare predators, were found. Species composition differed between the different types of container. Although 4 to 10 species used each type of container, the median number of species per container was two for treeholes and bamboo stumps, and one for the others. The dominant species wasTripteroides bambusa in treeholes and bamboo stumps,Aedes albopictus in stone vases, andA. japonicus in stone vessels. The larval mosquito community, which lacked major predators, possessed the following features that may facilitate the coexistence of many species: (1) niche segregation amongst species in terms of their selection of container types; (2) an aggregated distribution of the individual species among containers of the same type; (3) high intraspecific mean crowding (and hence probably intense intraspecific competition) in the dominant species in each type of container; (4) independent species associations within the same type of container; and (5) low interspecific mean crowding (and hence probablynot intense interspecific competition) between species in the same type of container.     

Influence of tree thinning on the abundance of mammals in a Japanese larch Larix kaempferi plantation

We examined the influence of tree thinning on the abundance of mammals in a Japanese larch Larix kaempferi plantation in Mt Gariwang, Pyeongchang, South Korea. In 2014 and 2015, from April to October, we recorded the presence of tracks as a proxy for abundance, for the following seven mammalian species: Korean hare Lepus coreanus, raccoon dog Nyctereutes procyonoides, Siberian weasel Mustela sibirica, Eurasian badger Meles meles, water deer Hydropotes inermis, roe deer Capreolus pygargus, and wild boar Sus scrofa. We also assessed how the intensity of tree thinning affected vegetation cover; there were significant differences in number of standing trees, basal area, coverage of vegetation layers, and number and volume of downed trees among the control, moderately thinned, and intensively thinned stands. We found significant differences in the abundance of tracks among the stands for three mammal species. In four mammal species, the abundance of track was significantly correlated with volume of downed trees, coverage of ground vegetation, number of downed trees, and number of standing trees, according to stepwise analysis. The presence and abundance of mammals is linked to habitat variables and forest managers should consider how habitat modifications will affect wildlife.     

Larval growth dynamics ofHemipyrellia ligurriens (Calliphoridae) andBoettcherisca formosensis (Sarcophagidae) in crowded and uncrowded cultures

Larval growth patterns of Hemipyrellia ligurriens (Calliphoridae) and Boettcherisca formosensis (Sacophagidae) in crowded and uncrowded cultures were compared. Growth of the larvae followed a sigmoid curve. The highest larval growth rates were 0.33 and 0.36 mg h⁻¹ for uncrowded and crowded H. ligurriens respectively. The corresponding figures were 2.38 and 1.23 mg h⁻¹ for B. formosensis. Larvae of both species attained maximum weight earlier in crowded cultures than in uncrowded cultures, although the final weights attained in crowded cultures were less. The earlier period of most rapid growth in both species was interpreted as a result of intraspecific facilitation at higher larval densities. Uncrowded B. formosensis had a shorter larval to pupal development and an earlier period of most rapid growth than uncrowded H. ligurriens, suggesting the former may be superior in exploiting carcasses with limiting food.     

Recent relaxation of purifying selection on the tandem-repetitive early-stage histone H3 gene in brooding sea stars

Patterns of nucleotide substitution differ between marine species that have a pelagic feeding (planktotrophic) larval stage and related species that lack such a stage, for both adaptive and non-adaptive reasons. Here, patterns of nucleotide and inferred amino acid substitution are analyzed for the tandem-repetitive early-stage histone H3 gene in 36 sea star species of the order Forcipulatida with documented larval habitat. The relative rate of nonsynonymous substitution (expressed as ω = d_N/d_S) was significantly higher in lineages with a brooded non-feeding (lecithotrophic) larval form than in lineages with a planktotrophic larval form. There was also a significant excess of conservative over radical substitutions. The increase in ω for brooders as compared to non-brooders was much greater than for previously analyzed mitochondrial sequences in echinoderms. These data are consistent with the hypothesis that purifying selection on this gene has been relaxed in brooding lineages compared to non-brooding lineages. The hypotheses of adaptive or neutral evolution are less plausible, although recent pseudogenization following a period of relaxed purifying selection could also explain the results.     

Modeling the spread of invasive nutrias (Myocastor coypus) over Iran

Nutria (Myocastor coypus) is a native aquatic rodent to South America, and was introduced to Europe, Asia, Africa and North America for fur farming. The South American nutria or coypu is now considered a pest in the area of introduction, because of its negative impact on biological diversity and ecological relationships. Having information on the invasion range of exotic species is crucial for understanding the ecology of invasive spread and for making good conservation and management planning to address this problem. At the beginning of the 20th century, nutria was introduced into Asia. Nutria was recorded for the first time in Iran in 1995. In the present study we proposed a multiple spatial scale approach to predict the invasion trends of the nutria in Iran, and to define up the “suitable scale” for predicting the invasion trends of this species. Our results highlighted the importance of environmental variables including vegetation density (for food and nesting) and water resource (streams, rivers, and lakes) in distribution of the nutria. Potential areas for the presence of the nutria are located near the Caspian Sea, west and central Iran which receive more precipitation than other parts of the country. Therefore, these parts of Iran may face a much greater risk of invasion risk in the future. Moreover, these results can show the possible risk of nutria invasion to the northern and western neighbors of Iran.     

The spatial structure of the physical environment

There is substantial environmental variance at small spatial scales (1 m or less) in both natural and disturbed environments. We have investigated the spatial structure of physical variables at larger scales (up to 10⁶ m). We analysed surveys of edaphic properties of Wisconsin forest soils, of the water chemistry of lakes in Ontario and Labrador, and of temperature and precipitation in northeastern North America. We found no clear indication that the variance among sites approaches some maximal value as the distance between them increases. We suggest instead that the variance of the physical environment tends to increase continually with distance. The slope of the log-log regression of variance on distance provides a means of comparing the heterogeneity of different environments with respect to a given factor, or of comparing different factors within a given environment. This slope provides a useful measure of environmental structure that can be related to the biodiversity or plasticity of native organisms.     

A comparison of reproduction in co-occurring chthamalid barnacles, Chthamalus stellatus (Poli) and Chthamalus montagui Southward

Reproduction in Chthamalus montagui Southward and Chthamalus stellatus (Poli) has been compared along gradients of wave exposure and tidal height. The proportion of barnacles carrying egg masses was greatest at low shore levels in both species, although the difference between levels was more pronounced in C. stellatus. Both species were found to breed between the beginning of May and the end of September. The mean number of broods released per season in both species ranged from 1.0 to 2.1 at high shore levels, from 2.2 to 3.2 at mid shore levels, and from 2.6 to 4.4 at low shore levels. C. stellatus predominated low on the shore at an intermediately exposed site and on the mid and low shore at the most exposed site. At these places it produced more broods per year than C. montagui. Development of the embryos of the two species was complete after 3 wk in vivo at 15°C. Eggs containing embryos of C. stellatus were larger than those of C. montagui, and within each species, larger barnacles produced larger eggs. Egg masses of C. stellanus included more eggs than those of C. montagui. Brood size in both species was greatest in shelter and least in exposure. Egg production was, however, similar in the two species when adjusted for differences in body mass. Egg production per unit body mass was greatest at an intermediately exposed site.     

罗氏沼虾育苗期浮游细菌群落演替模式、驱动因素及其生物标志物

为了探究罗氏沼虾(Macrobrachium rosenbergii)育苗期浮游细菌群落的时间动态和组装机制, 对3个苗种厂的全育苗周期进行持续追踪, 利用16S rRNA扩增子测序评估了罗氏沼虾幼苗发育过程中浮游细菌群落的动态演替、环境驱动因素、微生物标志物和共现网络。细菌群落的α-多样性在育苗期呈U型分布规律, 群落相似性遵循时间衰减模式, 群落周转率为0.011。随着虾苗的发育, 微杆菌科(Microbacteriaceae)(放线菌门: Actinobacteria)和冷形菌科(Cryomorphaceae)(拟杆菌门: Bacteroidetes)的相对丰度显著增加(P<0.05), 而拟杆菌门中的黄杆菌科(Flavobacteriaceae)和藏红花黄色线菌科(Crocinitomicaceae)的比重下降。pH是影响浮游细菌群落多样性和组成的最主要的环境驱动因素。利用随机森林分析, 鉴定了12个幼苗发育相关的微生物标志物, 其中伯克氏菌科(Burkholderiaceae)和圆杆菌科(Cyclobacteriaceae)分别是育苗早期(1—2d)和中期(8—10d)的指示性类群, 而腐螺旋菌科(Saprospiraceae)和分枝杆菌科(Mycobacteriaceae)作为标志物类群出现在中后期(16—21d)。育苗系统中菌群以正相关关系为主的共现模式随幼苗发育而减弱, 而负相互作用增加。研究结果揭示了罗氏沼虾育苗期浮游细菌群落的演替动态和群落聚集模式, 将为微生态调节和病害防控提供新见解。     

Impact of post-European stream change on frog habitat: southeastern Australia

Stream geomorphology and fluvial processes in Australia have generallybeen modified substantially since European settlement. In the case of theSouthern Tablelands of New South Wales, in southeastern Australia, detailednotes of early explorers and settlers and early survey maps have providedinsight into the nature of these changes. Early explorers described most streamsin this area as 'chains-of-ponds'. These are ponds connected byshort lengths of channel or divided by grassy intervals. Many of these systemswere converted to incised channels after Europeans arrived. An examination ofthe life history characteristics of frogs and their physiological limitationsprovides insight into how these changes are likely to have affected froghabitat. Chains-of-ponds provided permanent breeding ponds for frog species withextended larval stages. The environment surrounding these ponds floodedregularly, providing breeding habitat for species that can exploit ephemeralwaterbodies. Flood waters and saturated soil also created moist, well-vegetatedenvironments for adult frogs during the non-breeding season. Human impacts andlandscape modification led to channel incision of chain-of-pond systems andresulted in many physical changes in pond characteristics, includingavailability, permanency, structural complexity and flow dynamics. Theimplications of these changes are discussed in this paper. Hypotheses aredeveloped on frog species susceptibility to landscape change associated withchannel incision of chain-of-pond systems.     

Effects of maternal stress coping style on offspring characteristics in rainbow trout (Oncorhynchus mykiss)

Maternal size, age, and allostatic load influence offspring size, development, and survival. Some of these effects have been attributed to the release of glucocorticoids, and individual variation in these stress hormones is related to a number of traits. Correlated traits are often clustered and used to define the proactive and reactive stress coping styles. Although stress coping styles have been identified in a number of animal groups, little is known about the coupling between stress coping style and offspring characteristics. In the present study, plasma cortisol levels in ovulated mothers and cortisol levels in non-fertilized eggs from two rainbow trout (Oncorhynchus mykiss) strains selected for high (HR) and low (LR) post-stress plasma cortisol levels were compared. Offspring characteristics such as egg size, larval growth, and energy reserves also were compared between the two strains. Maternal plasma and egg cortisol levels were correlated, but no difference between the HR and LR strains was detected in either parameter. LR females produced larger eggs, and larvae with larger yolk sacs compared to HR females, however no differences in larval body size (excluding the yolk) was detected between strains. Considering that the HR and LR strains have a number of correlated behavioral and physiological traits that resemble the reactive and proactive stress coping styles, respectively, the results suggest that proactive mothers invest more energy into their offspring, producing larvae with larger energy reserves. It is possible that larger energy reserves in proactive larvae support the energy requirement for establishing and defending territory in salmonid fish. Furthermore, in the present study we found a positive relationship between mother plasma cortisol and egg cortisol; however neither mother plasma cortisol nor egg cortisol differed between strains. These results indicate that cortisol endowment from the mother to the offspring plays a minor role in the transfer of the behavioral and physiological traits which separates these strains.     

Environmental variables for modeling wheat yields in the southwest pampa region of Argentina

Two types of time scales – 10-day intervals (D) and phenological phases (P) – were applied to environmental variables for the development of statistical regression models relating to the southwest pampa region of Argentina, with the aim of detecting the effects of weather on wheat yields for the period 1977–1999. The parameters were grouped as meteorological and processed variables and indices. The processed variables used were total soil water availability (SWA) and the ratio of actual evapotranspiration to potential evapotranspiration (), obtained from a water-balance model in which the moisture anomaly index (Z) and the Palmer drought severity index (PDSI) were calculated according to Palmers model. For these parameters it was possible to establish the times of year and the phenological phases with the best correlation to grain yield. The regression equation for meteorological variables on a 10-day scale provides one of the best fits. Using mixed parameters, the two models, D and P, give rise to a standard error of estimate of approximately 200 kg ha^–1. Truncated models perform better on a P scale than on a D scale. The use of phenological stages improved yield assessment, particularly for those years with extreme meteorological conditions. The optimum models were tested and root-mean-square errors (RMSE) of 440 kg ha^–1 and 470 kg ha^–1 were obtained for P and D scales respectively.     

Environmental controls of diatom species in northeast Pacific sediments

Non-linear, unimodal techniques are suitable for estimation of environmental properties in the northeast (NE) Pacific based on fossil diatom taxa (species and/or species groups) found in modern (core-top) sediments. Canonical Correspondence Analysis (CCA), a constrained ordination technique, discerned best-fit relationships among two multivariate datasets (the floral and the environmental) and thus yielded insight into the environmental variables that best explain the species variance within diatom populations. Based on these insights, we developed predictive functions for annual Primary Productivity (PP) and seasonal range of sea Sea-Surface Temperature using unimodal models and cross validation techniques. Estimates of annual PP (r²_jack = 0.92; RMSEP = 91.94 gC/m²/y) explained the highest percentage of variance in the core-top diatom record (22.1%).