桑蓟马在桑树中空间分布的研究

桑蓟马Pseudodendrothrips mori是桑树的一种主要害虫。它的寄生直接影响供桑叶的质量和产量。我们通过泰勒幂法则和Morisita的散度指标对桑树蓟马在植株和桑园内的空间分布进行检验,结果显示:P.mori种群在植株内和桑园里的分布都存在局部化。桑树中蓟马的分布在树内显示出幼虫蓟马位于低层(从上面叶子起5-10层),但成虫更喜欢上层(从上面叶子起1-5层)。同一植株叶子的不同方向上蓟马密度没有出现明显变化。桑园内蓟马主要分布在桑园东部、南部和北部的植株上,中部,西部植株上的蓟马密度较低。P.mori的成虫和幼虫在叶子上的分布呈现明显聚集化。     

Responses of squirrel monkeys to seasonal changes in food availability in an eastern Amazonian forest

Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal shifts in fruit availability. In this study, I examined seasonal changes in diet and foraging behaviors of two groups of squirrel monkeys (Saimiri sciureus), studied for 12 months in Eastern Brazilian Amazonia, an area characterized by seasonal rainfall. Squirrel monkeys were primarily insectivorous (79% of feeding and foraging time), with fruit consumption highest during the rainy season. Although monkeys fed from 68 plant species, fruit of Attalea maripa palms accounted for 28% of annual fruit-feeding records. Dietary shifts in the dry season were correlated with a decline in ripe A. maripa fruits. Despite pronounced seasonal variation in rainfall and fruit abundance, foraging efficiency, travel time, and distance traveled remained stable between seasons. Instead, squirrel monkeys at this Eastern Amazonian site primarily dealt with the seasonal decline in fruit by showing dietary flexibility. Consumption of insects, flowers, and exudates increased during the dry season. In particular, their foraging behavior at this time strongly resembled that of tamarins (Saguinus sp.) and consisted of heavy use of seed-pod exudates and specialized foraging on large-bodied orthopterans near the forest floor. Comparisons with squirrel monkeys at other locations indicate that, across their geographic range, Saimiri use a variety of behavioral tactics during reduced periods of fruit availability.     

Why Folkbiology Matters: Resource Conflict Despite Shared Goals and Knowledge

There is a continuing controversy over Native American fishing and hunting rights. We show that Native American (Menominee) and European American fish experts have a common knowledge base and share values and attitudes associated with fishing practices (though organized around different ethical principles). Nonetheless, perceived group differences are dramatic (especially European American perceptions of Native Americans). Cultural differences in models of nature and associated inference processes appear to mediate these stereotypes and may hold the key to reducing intergroup conflict over resources.

Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean

• 1 Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of ≥8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings.
• 2 Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.
• 3 Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.
• 4 Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.
• 5 Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
• 6 South‐east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.
• 7 Antarctic blue whales numbered 1700 (95% Bayesian interval 860–2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4–11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.

     

Large clones on cliff faces: expanding by rhizomes through crevices

BACKGROUND AND AIMS: Large clones of rhizomatous plants are found in many habitats, but little is known about whether such clones also occur on cliff faces where environmental conditions are extremely harsh and heterogeneous. METHODS: Using molecular (intersimple sequence repeat, ISSR) markers, the genotypic composition of a cliff-face population of Oxyria sinensis in Sichuan, China, was investigated. KEY RESULTS: The 98 O. sinensis ramets sampled belonged to 12 different genotypes (clones). The three most frequent clones were represented with 45, 22 and 12 ramets, respectively; the remaining nine were represented with only one to five ramets. The three largest clones spanned at least 2.7 m in the vertical direction and 4.6-6.9 m in the horizontal direction on the cliff face. CONCLUSIONS: On the cliff face, large clones of O. sinensis are formed by rhizomes growing along the crevices. Expansion by rhizomes may help O. sinensis to exploit the patchy resources and support establishment and growth of new ramets. Moreover, rooted ramets connected by rhizomes may effectively reduce the susceptibility of O. sinensis to rock fall and erosion and thus greatly improve the chances for long-term survival. The multi-clone structure indicates that sexual reproduction is also important for the long-term persistence of O. sinensis populations on cliffs.     

A nonparametric procedure for the two-factor mixed model with missing data

We develop a nonparametric imputation technique to test for the treatment effects in a nonparametric two-factor mixed model with incomplete data. Within each block, an arbitrary covariance structure of the repeated measurements is assumed without the explicit parametrization of the joint multivariate distribution. The number of repeated measurements is uniformly bounded whereas the number of blocks tends to infinity. The essential idea of the nonparametric imputation is to replace the unknown indicator functions of pairwise comparisons by the corresponding empirical distribution functions. The proposed nonparametric imputation method holds valid under the missing completely at random (MCAR) mechanism. We apply the nonparametric imputation on Brunner and Dette's method for the nonparametric two-factor mixed model and this extension results in a weighted partial rank transform statistic. Asymptotic relative efficiency of the nonparametric imputation method with the complete data versus the incomplete data is derived to quantify the efficiency loss due to the missing data. Monte Carlo simulation studies are conducted to demonstrate the validity and power of the proposed method in comparison with other existing methods. A migraine severity score data set is analyzed to demonstrate the application of the proposed method in the analysis of missing data.     

Movements of undersized spotted grunter (<Emphasis Type="Italic">Pomadasys commersonnii</Emphasis>) in the Great Fish Estuary,South Africa: implications for fisheries management

The purpose of this study was to test the hypothesis that an estuarine species as the spotted grunter Pomadasys commersonnii is evenly distributed within the estuary and uniformly exploited by different groups of fishers. This was done by investigating the movements and area use of spotted grunter in relation to the fisheries. The position of 20 acoustically tagged fish was recorded during 36 days in February and March 2003, by manual tracking and automated data logging receivers. Information on the fisheries in the estuary was collected through visual registration of fishing effort and interviews. The spotted grunter moved on average 1.0 km (SD ± 0.7) between positional fixes. Most of the fish were positioned in the lower part of the 12 km long estuary, as 70% of the positional fixes were within the first 3 km, and 89% within the first 6 km. Approximately half (49%) of all the fixes were between 1.0 and 1.5 km from the estuary mouth. The spotted grunter used on average 4.9 km (SD ± 4.9) of the length of the estuary, and there was no significant relationship between the length of the estuary used and the body length of the fish (26–39 cm TL). Subsistence fishers accounted for 73% of fishing lines in the water, while recreational fishers accounted for the rest. Ninety-three percent of the lines were recorded within the first 6 km from the estuary mouth, of which 80% were recorded within the first 3 km. Almost 1/3 of the fishing effort was recorded between 1.0 and 1.5 km from the mouth. The hypothesis that the estuarine dependent species spotted grunter was evenly distributed within the estuary was rejected. However, there was a significant relationship between the distribution of the fishing effort of the subsistence fishers and the fish, indicating that the spotted grunter was uniformly exploited within the estuary by this group of fishers. In contrast, there was no relationship between the distribution of fish and recreational anglers.     

Habitat choice in rotifera communities of three shallow lakes: impact of macrophyte substratum and season

The distribution of rotifer communities between emergent (Typha angustifolia) and submerged (Chara tomentosa) vegetation and a comparatively open water zone were compared during the spring, summer and autumn seasons at three macrophyte-dominated lakes. This survey identified 107 rotifera species of which 58% of the taxonomical structure was common for the three examined lakes. Stoneworts with a more complicated spatial and morphological structure (having a much longer stem length than the narrow leaf cattail), supported higher rotifer densities. The stem length appeared to be the best predictor of all the macrophyte parameters and pH and chlorophyll a for the chemical variables, for explaining the variation of rotifer densities using the stepwise multiple forward regressions. The distribution of pelagic species did not differ between particular sites, which may have reflected the behavioural requirements of those rotifers. Some of them remained in the open water zone while others seeking an anti-predator refuge, gathered within macrophyte stands during the daytime. Moreover, there were nine Chara-associated species recorded and only one Typha-associated species was noted. The similarity of rotifer communities was most strongly influenced by particular habitat and season. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research     

At-sea distribution and scale-dependent foraging behaviour of petrels and albatrosses: a comparative study

1. In order to study and predict population distribution, it is crucial to identify and understand factors affecting individual movement decisions at different scales. Movements of foraging animals should be adjusted to the hierarchical spatial distribution of resources in the environment and this scale-dependent response to environmental heterogeneity should differ according to the forager's characteristics and exploited habitats. 2. Using First-Passage Time analysis, we studied scales of search effort and habitat used by individuals of seven sympatric Indian Ocean Procellariiform species fitted with satellite transmitters. We characterized their search effort distribution and examined whether species differ in scale-dependent adjustments of their movements according to the marine environment exploited. 3. All species and almost all individuals (91% of 122 individuals) exhibited an Area-Restricted Search (ARS) during foraging. At a regional scale (1000s km), foraging ranges showed a large spatial overlap between species. At a smaller scale (100s km, at which an increase in search effort occurred), a segregation in environmental characteristics of ARS zones (where search effort is high) was found between species. 4. Spatial scales at which individuals increased their search effort differed between species and also between exploited habitats, indicating a similar movement adjustment for predators foraging in the same habitat. ARS zones of the two populations of wandering albatross Diomedea exulans (Crozet and Kerguelen) were similar in their adjustments (i.e. same ARS scale) as well as in their environmental characteristics. These two populations showed a weak spatial overlap in their foraging distribution, with males foraging in more southerly waters than females in both populations. 5. This study demonstrates that predators of several species adjust their foraging behaviour to the heterogeneous environment and these scale-dependent movement adjustments depend on both forager and environment characteristics.