我国草兔的聚类研究

本文用新的聚类方法, 对中国草兔进行系统聚类。     

Preparation of High Yields of Algal Protoplasts Using Buccal Juice of Sea Hare and Commercial Cellulase

Buccal juice of the sea hare Aplysia juliana was found to degrade algal polysaccharides. The optimal enzyme composition for protoplast preparation from Undaria pinnatifida was protein at 48 μg/ml buccal juice from sea hare, 10 mg/ml cellulase Onozuka-RS, 0.4 M NaCl, 0.8 M sorbitol, 2 mg/ml dextran sulfate sodium salt, and 1 μl/ml 2-mercaptoethanol in 10 mM MES buffer (pH 6.0). Protoplasts of Eisenia bicyclis, Endarachne binghamiae (Phaeophyta), and Ulva pertusa (Chlorophyta) could also be prepared in a similar manner. Yields of these protoplasts were about 10⁷ cells per gram of fresh weight alga. Received January 26, 1998; accepted September 17, 1998.     

Winter Habitat Selection by Canada Lynx in Maine: Prey Abundance or Accessibility?

Abstract: We related winter habitat selection by Canada lynx (Lynx canadensis), relative abundance of snowshoe hares (Lepus americanus), and understory stem densities to evaluate whether lynx select stands with the greatest snowshoe hare densities or the greatest prey accessibility. Lynx (3 F, 3 M) selected tall (4.4-7.3 m) regenerating clear-cuts (11-26 yr postharvest) and established partially harvested stands (11-21 yr postharvest) and selected against short (3.4-4.3 m) regenerating clear-cuts, recent partially harvested stands (1-10 yr), mature second-growth stands (>40 yr), and roads and their edges (30 m on either side of roads). Lynx selected stands that provided intermediate to high hare density and intermediate cover for hares (i.e., prey access) but exhibited lower relative preference for stand types with highest hare densities where coniferous saplings exceeded 14,000 stems/ha.     

In vitro Cultivation of the Entomogenous Nematode Filipjevimermis leipsandra

The mermithid nematode, Filipjevimermis leipsandra, was successfully cultivated to the preadult stage in Schneider''s Drosophila medium supplemented with 20% fetal bovine serum. Upon transfer to a solid substrate the preadults continued to develop into ovipositing adult females. Four molts were observed. The first molt occurred in the egg. The second occurred after 6-8 days in culture during which the very thin cuticle was shed completely. The third molt occurred after 18-20 days in culture; the cuticle was retained by the third-stage nematode. This stage was considered comparable to the preadult stage that emerges from host larva, Diabrotica spp. The fourth molt occurred within 12 days after the preadult was transferred from the liquid medium to a solid substrate. Adult females began ovipositing viable eggs 1-3 days after the final molt.     

The diel activity pattern of mountain hare (Lepus timidus) on managed heather moorland in Scotland

The research presented in this paper provides an insight into the behavioral ecology of mountain hares on heather moorland in the Lammermuir Hills of southeast Scotland. We examine the seasonal and diel activity patterns using camera traps over a period of 12 months. The rate of camera detections was calculated for the different divisions of the 24‐hr cycle (daylight, dusk, night, and dawn). During autumn and winter (October–February), the activity pattern was crepuscular with greater activity at dusk than at dawn. Daylight activity was relatively low, and there was a regular pattern of small peaks of activity during the night. In spring and summer (March–September), peaks of crepuscular activity remained evident but daylight activity was much more prevalent than during autumn and winter, and night activity was lower. We discuss the problematic definition of twilight and present an explanation for seasonal changes in the pattern of diel activity that is linked to the reproductive cycle of the mountain hare.     

The effect of establishing native woodland on habitat selection and ranging of moorland mountain hares (Lepus timidus), a flexible forager

Mountain hares Lepus timidus L. typify species that occupy a broad geographic range and have flexible foraging and nutritional strategies. Such species may show a range of responses to habitat modification. This study aimed to provide a basis for prediction of the impact of mountain hares on woodland establishment, and of woodland establishment on mountain hare distribution. The selection of and the extent of incorporation of new woodland into the home range of mountain hares was investigated in an area where Scots pine Pinus sylvestris L. woodland was establishing within their usual habitat in Britain, upland heather moorland. Seasonal home, day and night-range sizes of radio-tracked mountain hares were determined using the multinuclear probability polygon technique and analysed using residual maximum likelihood (REML). Habitat selection was analysed using compositional analysis. Three main habitat types were available to hares: heather moorland with trees, heather moorland and grassland-mire. Mean home-range size of mountain hares in summer was 10.3 ha and in winter 9.6 ha. There were no significant seasonal or sex differences in home-range size. Females selected grassland-mire habitat in summer and showed no strong selection for any habitat in winter. Males selected heather moorland in both summer and winter. Heather moorland with trees was not selected preferentially by mountain hares of either sex in summer or winter. The absence of selection for areas of newly establishing-Scots pine woodland suggests that any browsing damage to trees by hares is most likely to be a function of the local abundance of mountain hares, rather than a result of active preference of hares for the modified habitat.     

Resource partitioning by mammalian herbivores in the high Arctic

Willow (Salix arctica) and sedges (Carex stans and Eriophorum triste) were the dominant plants available as forage for herbivores in the high Arctic of Greenland. Willow leaves were of high quality as forage in early stages, of phenology, but crude protein and digestibility declined markedly by late stages whereas sedges, remained high in forage quality throughout the growing season. Densities of fecal pellets indicated that muskoxen (Ovibos moschatus) made heaviest use of sedge-dominated vegetation types in both winter and summer, although increased use of willow communities was observed in early summer. Hares (Lepus arcticus) favored willow-dominated communities in both winter and summer. Evidence of collared lemming (Dicrostonyx groenlandicus) winter use was mainly in willow-dominated communities where snow had accumulated, whereas in summer they were present in drier habitas dominated by willows, but with greater plant diversity. Analyses of plant tissues in feces indicated that graminoids composed over 60% of the diet of muskoxen in winter and over 40% in summer. Willows were of nearly equal importance in the muskox diet in summer, and forbs, Dryas integrifolia, and moss collectively composed over 20% of the diet in both summer and winter. Grass accounted for nearly 50% of the diet of hares in both summer and winter, with willows, forbs, and moss accounting for most of the remainder. Willows and graminoids dominated the diet of lemmings, with willows being somewhat more important in summer and graminoids in winter. Moss was a noteworthy dietary component of lemmings. Differences in body and digestive-tract morphology among the three mammalian herbivores account for differences in locomotive efficiency, predator avoidance, and foraging efficiency which interact with vegetation quality, density, and patchiness. The resulting patterns of use of the landscape result in minimal overlap in use of forage resources and help to explain the distribution and co-existence of high Arctic herbivores.