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1.
2005年12月~2006年6月对广东海丰公平大湖保护区的紫水鸡(Porphyrio porphyrio)种群密度进行了调查。繁殖期和非繁殖期的种群密度分别为13.33只/km2和9.33只/km2。通过对大湖和东关联安围总的样线平均个体数比较,差异性显著(P<0.05);在种群密度上,发现东关联安围不同时期的种群密度均较高,分别达16.11只/km2和11.67只/km2,大湖分别为9.17只/km2和5.83只/km2。对种群影响因素分析表明,非法猎捕和栖息地质量下降是导致紫水鸡种群变化的重要原因。  相似文献   
2.
紫水鸡冬季觅食地选择   总被引:1,自引:0,他引:1  
2006年11月-2007年2月,在广东海丰鸟类自然保护区采用样方法研究了紫水鸡(Porphyrio porphyrio)的冬季觅食地选择。研究结果显示,紫水鸡在冬季对觅食地植被具有明显的选择性,偏爱水葱(Scirpus tabernaemontani)。对62个觅食地样方18个因子的主成分分析表明,草本密度、草本均高、草本盖度、灌木种类、水质和水位这6个因子是冬季觅食地选择的主要因子。判别分析结果表明,枯高、动物性食物丰富度、距大道距离、草本种类、距小道距离、距所处水面边缘距离是区别冬季觅食地和对照地样方的主要参数,判别准确率可达78.1%。紫水鸡冬季多选择在水葱或芦苇(Phragmites communis)等草本植被生长良好、具有特定水位或水质及中等程度的人为干扰的地方觅食。因此,该地区冬季觅食地的恢复和保护对紫水鸡的保护有着重要的意义。  相似文献   
3.
In nonpedigreed wild populations, inbreeding depression is often quantified through the use of heterozygosity-fitness correlations (HFCs), based on molecular estimates of relatedness. Although such correlations are typically interpreted as evidence of inbreeding depression, by assuming that the marker heterozygosity is a proxy for genome-wide heterozygosity, theory predicts that these relationships should be difficult to detect. Until now, the vast majority of empirical research in this area has been performed on generally outbred, nonbottlenecked populations, but differences in population genetic processes may limit extrapolation of results to threatened populations. Here, we present an analysis of HFCs, and their implications for the interpretation of inbreeding, in a free-ranging pedigreed population of a bottlenecked species: the endangered takahe (Porphyrio hochstetteri). Pedigree-based inbreeding depression has already been detected in this species. Using 23 microsatellite loci, we observed only weak evidence of the expected relationship between multilocus heterozygosity and fitness at individual life-history stages (such as survival to hatching and fledging), and parameter estimates were imprecise (had high error). Furthermore, our molecular data set could not accurately predict the inbreeding status of individuals (as 'inbred' or 'outbred', determined from pedigrees), nor could we show that the observed HFCs were the result of genome-wide identity disequilibrium. These results may be attributed to high variance in heterozygosity within inbreeding classes. This study is an empirical example from a free-ranging endangered species, suggesting that even relatively large numbers (>20) of microsatellites may give poor precision for estimating individual genome-wide heterozygosity. We argue that pedigree methods remain the most effective method of quantifying inbreeding in wild populations, particularly those that have gone through severe bottlenecks.  相似文献   
4.

Mite relationships were investigated in an orchard near Nelson from 1962 to 1974 in conjunction with a long‐term experiment into integrated control of apple pests. From 42% to 57% of the total winter eggs of Panonychus ulmi hatched over a period of 48–53 days from the last week of September until mid November. The main hatch—from 10% to 90%—took 19–20 days. Five generations occurred in each season, from October to March, although some females laid winter eggs from mid January if leaf condition became poor. Insect predators found were Stethorus bifidus, Sejanus albisignata, Arthrocnodax sp., and Xylapothrips sp. The mite Typhlodromus pyri (Phytoseiidae), the most important predator, had up to 5 generations from October to March; some females ceased to feed or oviposit from mid February onwards, and took on the characteristics of the overwintering diapause phase. With the integrated programme based on ryania, a favourable balance of P. ulmi and T. pyri was established after an initial outbreak of P. ulmi in the 1st or 2nd season, and was maintained until 1970–71, when P. ulmi outbreaks occurred on several cultivars in a season marked by hot, dry conditions in November and December. Natural control was restored the next year except on cy. Delicious, where P. ulmi remained in greater numbers for several years. With a complete commercial spray programme from 1962 to 1967 P. ulmi became resistant to all acaricides used; with the regular azinphos‐methyl programme and no acaricides in 1967–68 a population of T. pyri resistant to this insecticide emerged. The approximately × 10 resistance level did not increase appreciably, so the azinphos‐methyl dosage was reduced from 0.05% to 0.025% to allow greater survival. Several hot, dry summers followed, and commercial control of P. ulmi by T. pyri did not occur until 1973–74. A programme of low‐dosage carbaryl allowed T. pyri and S. albisignata to establish in fair numbers, but control of P. ulmi was not achieved. Experiments with mineral oils and cyhexatin have shown them to have some potential for inclusion against P. ulmi in future integrated programmes.  相似文献   
5.
Abstract

Autotriploidy is described in a female of the endemic New Zealand frog Leiopelma hochstetteri. This frog was found to have 3n=33 chromosomes plus 2 supernumerary chromosomes. All the chromosomes in the karyotype of this species contained C-band heterochromatin at the centromeres. A prominent C-band was found to be associated with a secondary constriction on chromosome no. 7. The supernumerary chromosomes in this species appear to be mitotically stable and contain C-band heterochromatin at the centromeres. From the limited data presently available, the triploid individual may have resulted from the fertilisation of a diploid egg produced when the second meiotic division had been suppressed.  相似文献   
6.
中国南方紫水鸡(Porphyrio porphyrio)在快速扩散,探究其生态适应十分必要。2014年3月至2015年8月在云南鹤庆草海湿地的观察,得到以下结果。紫水鸡集中分布在以开阔水域为主并有足够植被覆盖的西草海,很少见于附近干扰频繁的其他湿地,其适宜的生境开阔水域约占49.6%、水生植被覆盖水面占39.3%、陆地占11.1%;紫水鸡早间(7:00~9:00时)频繁活动在开阔水域、高草丛、岸边草地,中午后逐渐远离岸边而藏掖草丛中;白天活动的紫水鸡集群大小在1~7只之间,1~2只的集群占62.0%,大的集群中常有司职警戒、领头的个体;紫水鸡用于觅食、休息、警戒的时间分别占47.8%、23.5%、15.1%,很少互动交流,但常驱赶靠近的其他鸟类以维护个体自身的"领域";紫水鸡应对干扰威胁的警戒、避让、惊飞平均距离分别是26.4 m、20.5 m和17.6 m。在鹤庆的紫水鸡集中分布于西草海湿地并避让人为干扰,说明其以避让和逃逸方式应对人为干扰和生境胁迫,应该考虑立法给予重点保护。  相似文献   
7.
Egg strings and larvae of Hochstetter's frog (Leiopelma hochstetteri) were located at three widely separated North Island sites: in seeps at Brynderwyns in December 2004, in an open pool at Wharerino in March 2009, and in an underground pool near the Kaipawa Track, Coromandel, in late May 2009. Ten egg strings were also laid by captive frogs in water courses at Hamilton Zoo in April 2009. All egg strings held from 11 to 13 eggs. The egg strings laid in the Brynderwyns were regularly observed until metamorphosis was completed in March 2005. Twenty-four swimming larvae emerged from 25 capsules at c. 40 days after discovery, and at least 14 froglets were produced at c. 90 days. All of them developed in darkness, in a 120 ml pool <30 mm deep. The emerged froglets ranged from 9.8 to 10.8 mm snout-vent length. The detection of eggs, larvae and <11 mm froglets indicates that the egg laying period is at least from late September to May.  相似文献   
8.

Of two laboratory strains of Drosophila melanogaster used in this study, the +3 strain had slightly higher mean abdominal bristle number and estimated heritability of this character than the Oregon‐R. Their F1 hybrid exhibited 5 % heterosis. Fourteen generations of the two original strains and the F3 of the hybrid were selected for high and low numbers of abdominal bristles on the 4th and 5th sternites, at a selection intensity of 20%. A mass‐mated unselected control was maintained for each population. The +3 population responded considerably more to selection for low numbers of bristles than high, and the Oregon‐R population showed a similar, though less marked, tendency; the Crossbred population responded more strongly to selection for high numbers. Except for the Crossbred high selection line, all lines declined in response rate, phenotypic variance, and realised heritability. The average realised heritability of the Oregon‐R and +3 high and low selection lines over 14 selection generations fell short of their predicted base population heritabilities. The deviation from the predicted was particularly pronounced with selection for high bristle number in the +3 line.  相似文献   
9.
2011年1月至11月使用瞬时扫描法及焦点动物取样法对云南省大理市洱源县西湖湿地(26°00′~26°01′N,100°02′~100°03′E,平均海拔1 970 m)的紫水鸡(Porphyrio porphyrio)行为进行了观察,将行为定义为取食、寻食、休息、修饰、警戒、位移和其他共7类,扫描时将取食和寻食合并为觅食,分析非繁殖期的日节律和时间分配特点。觅食高峰出现在早晨和傍晚,低谷在秋季为下午14:30时(占所有行为类型56.56%)、冬季12:30时(55.61%)、春季11:00时(55.80%)。休息高峰秋季出现在12:30时(26.79%),冬季一日内呈上升趋势,春季呈双峰型,低谷在13:30时(14.64%)。从时间分配来看,寻食、取食、修饰等行为在不同季节间存在显著差异,寻食时间从高至低依次为冬季、春季、秋季,分别占总活动时间的19.87%、9.36%、3.03%;取食时间则相反,依次为秋季(72.54%)、春季(56.78%)及冬季(44.59%);与新西兰Pukepuke Lagoon种群相比,西湖湿地紫水鸡种群在秋季大量取食,在冬季增加寻食和休息时间,以应对高原湿地的温度和食物变化。修饰行为在繁殖期前(春季)最多(15.84%),繁殖期后(秋季)减少(11.10%)。以上结果说明,为适应气候、食物等条件的年周期变化,紫水鸡行为策略在不同时期和地点具有可塑性,这可能是该物种在滇西北地区得以繁衍及扩散的原因之一。  相似文献   
10.
The rediscovery of the Takahe Porphyrio hochstetteri in 1948 in the remote mountains of Fiordland, New Zealand, has been described as one of the greatest moments in ornithological history. The subsequent management of the population has become a model for avian recovery programmes, yet questions still remain regarding the population size at the time of, and prior to, its rediscovery. We used 20 microsatellite markers to genotype samples of the three surviving museum specimens (1849–1898) collected prior to the initial declaration of extinction to estimate levels of genetic diversity and effective population size. These estimates were compared with equivalent estimates from DNA samples of three specimens preserved at the time of rediscovery (1949) and with 20 contemporary samples. Using rarefaction simulations to account for the limited sample sizes, the results suggest that only slightly more genetic diversity (allelic diversity and numbers of polymorphic loci) existed in the earliest Takahe sampled and that levels of genetic diversity at the time of rediscovery were very similar to those today. Effective population size estimates showed a similar pattern. Contemporary samples from a widespread congener to Takahe, the Pukeko Porphyrio porphyrio, showed consistently higher levels of genetic diversity and greater effective population size, even after equivalent rarefaction to the same small sample sizes available for Takahe. It is likely that the population size of Takahe in Fiordland at the time of European arrivals in the 1800s was similar to its current size. These results provide molecular support for the hypothesis that Takahe were common throughout most coastal and eastern parts of the South Island of New Zealand before being hunted to extinction in these regions by early Maori, and persisted as a relatively small and isolated population in Fiordland where they may never have been very common. This is in marked contrast to other New Zealand endemic birds found in Fiordland, such as the Kakapo Strigops habroptilus and several forest passerines, which remained relatively numerous until the time of European arrival before undergoing rapid declines thereafter.  相似文献   
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