虎斑夜鳽分布与亚群态势研究

本世纪以来对虎斑夜鳽分布地点的新发现,表明该种从滨海到内陆漫布于中国长江以南广大地区,并向北渗透直逼东洋界北限秦岭-淮河一线;作者据此将各地的虎斑夜鳽初划为11个亚群,提出目前该种存有3个相对健康而稳定的亚群,即黄山-天目山亚群、南岭亚群和广西亚群,且每个亚群的分布范围均至少不会小于5000km2,其中以黄山-天目山亚群的记录由历史至现今相对最为长久而完整,进而提出今后在上述诸亚群范围之外还会有新的发现.文中指出,尽管近期对虎斑夜鳽分布状况有了新认识,目前仍可视该种的受胁等级为濒危.     

Surface sediment diatom assemblages and epilimnetic total phosphorus in large, shallow lakes of the Yangtze floodplain: their relationships and implications for assessing long-term eutrophication

1. The Yangtze floodplain (SE China) is characterized by a number of large shallow lakes, many of which have undergone eutrophication due to the intensification of agriculture and urban growth over recent decades. As monitoring data are limited and in order to determine lake baseline nutrient concentrations, 49 lakes were sampled, covering a total phosphorus (TP) gradient (c. 30–550 μg L⁻¹) to develop a diatom-based inference model. 2. There are three dominant diatom assemblages in these shallow lakes with a marked change in assemblage structure near the boundary between eutrophic and hypereutrophic nutrient levels (as indicated by their TP value). Canonical correspondence analysis indicated that TP was the most important and significant variable in explaining the diatom distributions, independently accounting for 9.5% variance of diatoms. 3. Forty-three lakes were used to generate a transfer function using weighted averaging (WA) with inverse deshrinking. This model had low predictive error (root mean squared error of prediction; RMSEP_jack = 0.12) and a high coefficient of prediction (R²_jack = 0.82), comparable with regional TP models elsewhere. The good performance of this TP model may reflect the low abundance of benthic diatom species which are commonly regarded as the main error source in European shallow lake WA models. 4. The WA model was used to reconstruct the past-TP concentrations for Taibai Lake, a shallow hypereutrophic lake in Hubei province. The results showed that TP concentration varied slightly (43–62 μg L⁻¹) prior to the 1920s, indicating an eutrophic state since the 1800s. A period of sustained eutrophication occurred after 1950, because of the development of agriculture, reflecting by maximum values of Aulacoseira alpigena and increased abundance of Cyclotella meneghiniana, C. atomus and Cyclostephanos dubius. The steep increase in nutrient concentration after 1970 was related to the overuse of chemical fertilizer and fish farming in the catchment. 5. The shift in fossil diatoms from epiphytic to planktonic forms in the lake sediment core during 1950–70 provides useful information on the transformation from macrophyte-dominated to alga-dominated states. It is plausible that the TP concentration of 80–110 μg L⁻¹ observed in this study is the critical range for switching between the two stable states in the lake. 6. The regional diatom-TP model developed in this study allows, therefore, the possibility of reconstructing historical background nutrient concentrations in lakes. It will provide an indication of the onset and development of eutrophication at any site. This is particularly important for the many lakes in the Yangtze floodplain where information about historical changes in water quality is lacking.     

Life cycles and food habits of mayflies and stoneflies from temporary streams in western Oregon

1. Field data and results from laboratory rearing are combined to describe life cycles and food habits of the mayflies Paraleptophlebia gregalis and Ameletus n. sp., and the stoneflies Soyedina interrupts, Ostrocerca foersteri, Sweltsa fidelis and Calliperla luctuosa. 2. P. gregalis, A. n. sp., S. interrupts and O. foersteri have univoltine life cycles which are characterized by a high degree of plasticity. S. fidelis and C. luctuosa have semivoltine life cycles which are more tightly synchronized. 3. Laboratory feeding trials and field observations characterize P. gregalis as a collector, A. n. sp. as a scraper, O. foersteri and S. interrupta as shredders and C. luctuosa as a predator mainly of midge larvae. Late-instar larvae of S. fidelis are believed to be scavengers. 4. Laboratory rearing yielded a negative correlation between growth rates (Y) and larval size in autumn (X) for S. interrupta. This indicates compensatory growth by small larvae in order to achieve synchronized emergence. The correlation can be described by the equation: Y = 0.0053–0.0036X (R²= 0.82; P < 0.01; n = 22) 5. The field and laboratory data indicate that photoperiod mainly determines the rate of development and size of emerging subimagos in P. gregalis.     

Characterization of microsatellite loci isolated in midget faded rattlesnake (Crotalus viridis concolor)

Primers for five polymorphic microsatellite loci were developed for the midget faded rattlesnake (Crotalus viridis concolor), a rare subspecies of western rattlesnake (Crotalus viridus) found only in parts of Wyoming, Colorado, and Utah. Five polymorphic microsatellites were isolated, four of which had relatively high levels of diversity (eight to nine alleles). We found only two departures from Hardy–Weinberg equilibrium and they occurred in different loci, so null alleles are likely not a problem. Moreover, we found that no two loci were linked. These loci will be applicable for population genetic analysis and perhaps analysis of paternity and mating systems.     

Genetic variation in the blood of llamas, Llama glama, and alpacas, Llama pacos

Blood samples of llamas and alpacas were typed using haemolytic, electrophoretic and isoelectric focusing procedures to assay polymorphism at 13 loci. Blood group variation was assessed using six antibody specificities produced by allo- and heteroimmunizations. Two red cell factors (A and B) behave as autosomal, codominant alleles at a closed A locus. The other four factors (C, D, E and F) behave as autosomal, dominant traits. Biochemical variation was found for red cell enzymes catalase, phosphogluconate dehydrogenase, glucose phosphate isomerase and for plasma proteins transferrin and post-albumin. No variants were found for haemoglobin, phosphoglucomutase and albumin. Estimates of probability of exclusion were 0.883 for llamas and 0.681 for alpacas, which are adequate initial levels of efficacy for purposes of parentage verification. Preliminary estimate of Nei's genetic distance measure (D) suggests that llamas and alpacas are more likely related as subspecies than as separate species.     

Isopycnometric Serology: a New Technique based on Buoyant Density Changes in Latex Beads

WE wish to describe new serological techniques based on changes in buoyant density occurring when antibodies, or antigens, or both, are attached to latex beads. For the density change to be observed, the mass of the attached particles must be an appreciable fraction of the total mass. Using very small carrier beads less than one hundred antibody molecules or one virus particle per bead can be detected. The speed and sensitivity of the method make it directly applicable to the clinically important problem of rapid identification of infectious agents.     

Phylogenetic relationships and speciation patterns in an African savanna dwelling bird genus (Myrmecocichla)

Phylogenetic relationships among eight of nine Myrmecocichla chat species were inferred from DNA data. Bayesian posterior probabilities and maximum‐likelihood bootstrap percentages strongly supported most branches in the phylogeny. Based on these results, Myrmecocichla, as currently defined, is not monophyletic. The results indicated that Myrmecocichla albifrons is part of a Cercomela + Oenanthe clade, whereas Oenanthe monticola is shown to be a Myrmecocichla. In addition, Myrmecocichla arnotti is shown to be polyphyletic. Phylogenetic analyses support three Southern versus Eastern or Northern speciation events. The dating of these speciation events suggests that they correspond to periods when the Afrotropical forests were expanded to coastal Kenya, 3–5 Mya. This forest expansion thus served as a vicariant driver of speciation in the genus, a result consistent with speciation patterns in other arid‐adapted African bird genera. Our haplotype analysis within one of the most widespread and habitat diverse Myrmecocichla species (formicivora, a southern African endemic) showed little genetic variation. Along with speciation patterns shown for Myrmecocichla and other avian genera, this lack of standing variation would appear to support large, inter‐regional drivers of speciation as having the largest effect on the diversification of arid‐adapted Africa bird species, which is in stark contrast to other vertebrate lineages whose genetic structure often shows strong intra‐regional effects. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 180–190.