贵州特有植物贵州槭的种群结构及动态研究

贵州槭(Acer guizhouense)属常绿阔叶乔木,仅分布于贵州省黄平县新州镇海拔770~1 000 m有山峰屏障的常绿阔叶落叶混交林中,颇具科研和经济价值,研究其种群结构特征和数量动态变化对于探索特有植物保护生物学具有重要意义。该研究对贵州槭疑似分布区开展普查,并在密集分布区设置样地进行详查,分析其种群结构与数量动态的变化规律。结果表明:(1)贵州槭的自然分布区极为狭窄,雷坪分布区约0.3 km~2,总计约2 600株,其中密集分布区0.03 km~2,平均种群密度78 800株/km~2,稀疏分布区0.27 km~2,平均种群密度≤1 500株/km~2;在东坡村飞云崖风景区有约0.05 km~2的稀疏分布,且在雷坪至东坡两分布区之间没有发现自然分布;采用SAFE指数和IUCN的标准评价,贵州槭属于濒危物种(EN)。(2)贵州槭幼树占种群的比重达63.23%,种群密度大小为幼树中龄树成年树,种群结构为增长型;种群死亡率曲线和消失率曲线分别在Ⅰ龄期和Ⅸ龄期出现2个高峰,在Ⅲ-Ⅷ龄期间和Ⅹ-Ⅺ龄期间出现2个低谷,种群存活曲线趋于Deevey-Ⅲ型特征;(3)人为采伐和生境遭破坏造成的植株死亡或者丧失增加是导致贵州槭种群数量稀少的主要原因,在加强就地保护的同时,开展人工育苗迁地应用栽培是现实而有效的合理保护措施。     

Molecular phylogeny of the endemic Philippine rodent Apomys (Muridae) and the dynamics of diversification in an oceanic archipelago

We analysed the phylogenetic relationships of ten of the 13 known species of the genus Apomys using DNA sequences from cytochrome b . Apomys, endemic to oceanic portions of the Philippine archipelago, diversified during the Pliocene as these oceanic islands arose de novo . Several of the speciation events probably took place on Luzon or Mindanao, the two largest, oldest, and most topographically complex islands. Only one speciation event is associated with vicariance due to Pleistocene sea-level fluctuation, and a Pleistocene diversification model in which isolation is driven by sea-level changes is inconsistent with the data. Tectonic vicariance is nearly absent from the Philippines, in which tectonic coalescence plays a significant role. Most speciation events (about two-thirds) are associated with dispersal to newly developed oceanic islands. The data imply that the species have persisted for long periods, measured in millions of years after their origins; further implications therefore are that faunal turnover is very slow, and persistence over geological time spans is more prominent than repeated colonization and extinction. Neither the equilibrium nor the vicariance model of biogeography adequately encompasses these results; a model incorporating colonization, extinction, and speciation is necessary and must incorporate long-term persistence to accommodate our observations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80 , 699–715.     

Population genomics reveals differences in genetic structure between two endemic arboreal rodent species in threatened cloud forest habitat

Mammal Research - Genomic tools are now commonly used to assess the genetic diversity and genetic structure of species and populations, and they provide the ability to describe and address the...     

On the dynamics of rodent social groups

A prevailing view is that animal social groups are largely determined by natal philopatry. However, other processes can influence the dynamics of social groups, including emigration of individuals that join pre-existing groups. Given that fitness consequences of living in a group may vary depending on how groups changes, the extent to which alternative mechanisms drive social dynamics is an important theme to the evolution of sociality. We considered the available literature on social rodents to examine (i) whether the available evidence supports single versus multiple mechanisms, (ii) how strongly evidence supports a major importance of natal philopatry, and (iii) whether mechanisms of group formation are linked to the reproductive strategy across species. While natal philopatry is considered the major process behind group dynamics in 26% of species examined, studies on 74% of species indicate two or more mechanisms take place simultaneously. Natal philopatry is considered a primary mechanism in communal (56%) and singular breeders (70%), but less so in solitary breeders (18%). Thus, the tenet that natal philopatry is the main process driving group dynamics in rodents may be premature, and studies aimed at examining the importance of alternative mechanisms are justified.     

Population structure and dynamics of a neotropical palm in fire-impacted fragments of the Brazilian Atlantic Forest

The demography of the acaulescent palm Attalea humilis was studied from 1996 to 1999 in three forest fragments (1.6, 6.4, and 9.9ha) in southeastern Brazil (22°30–22°33 S, 42°15–42°19 W). A human-induced fire damaged the populations in August–September 1997. Palm density was higher in the medium-sized fragment, where it was concentrated in a single disturbed sector. Population ontogenetic stage structure was dependent on fragment and year, but in general later stages were more abundant than initial ones. Population finite growth rates projected from linear, stage-structured demographic models indicated that the populations were increasing before fire. Population growth rate in the smallest fragment was larger due to a single recruitment event, being most sensitive to changes in survival and growth of seedlings, virgins and the immature, and relatively insensitive to changes in shrinkage and fecundity. Observed growth rates for the entire study period showed that populations remained in equilibrium after fire, but the population in the medium-sized fragment showed a declining tendency. Population structure was resilient to fire, which caused a transitory concentration of individuals in the medium-sized stage. The self-sustainability of the population in the largest, most preserved fragment suggests that habitat-protection measures may suffice to ensure the persistence of populations in small fragments. However, population fluctuations and exclusion from hyper-disturbed sectors in the smallest fragment suggest that reduced fragment area, habitat degradation and human-induced fires can interact to threaten the persistence of even abundant, preadapted to fire, species like A. humilis.     

Population dynamics of a generalist rodent in relation to variability in pulsed food resources in a fragmented landscape

1. Pulsed food resources are often considered equivalent in their potential impact on the reproduction and population dynamics of consumers, but differences in the attributes of food pulses and their distribution in the landscape may cause differences in their effects. 2. We tested whether a perishable pulsed resource (periodical cicadas, Magicicada spp.) had similar effects on the population dynamics of a generalist forest rodent, Peromyscus leucopus, as have been reported for a cacheable pulsed resource (acorn mast). 3. Because the availability of periodical cicadas may vary between edge and interior habitat, we also tested whether habitat type (edge vs. interior) and fragment size affected the abundance of cicadas and P. leucopus. 4. Nearly 90% of the variation in the relative population densities of P. leucopus was explained by the variation in the relative densities of periodical cicadas, and fragments with more cicadas tended to have more reproductive female mice and litters. 5. We found more cicadas and more P. leucopus in edge than interior habitat, but no differences in the relative densities of either in relation to fragment size. 6. Data from a non-emergence year revealed no differences other than the presence of periodical cicadas that could explain the 50% higher relative densities of P. leucopus in the emergence year. 7. At the beginning of the emergence of periodical cicadas, the three fragments with the highest numbers of emergence holes had three times more mice than the fragments with the lowest numbers of emergence holes, suggesting that P. leucopus is able to anticipate the emergence of periodical cicadas and increase reproduction prior to the pulse. 8. Hence, despite differences in perishability, seasonal timing and nutritional quality of pulsed food resources in a fragmented landscape, they appear to have similar positive effects on the population dynamics of the generalist rodent, P. leucopus and, in fact, P. leucopus may be able to anticipate resource pulses.     

Population dynamics and production of Jesogammarus annandalei, an endemic amphipod, in Lake Biwa, Japan

SUMMARY 1. Population dynamics and production of Jesogammarus annandalei , an endemic amphipod in Lake Biwa, were examined from April 1997 to June 1998. The life cycle of this species was 1 year with the new generation beginning in early autumn. They preferred low temperature (<12 °C) and their spatial distribution varied seasonally and accordingly.
2. In deep water, the abundance of J. annandalei ranged from 200 to 63 000 m⁻² and decreased towards summer and the biomass (0.01∼3.6 g C m⁻²) was on average comparable that of zooplankton. The density was much higher than that recorded by a study conducted 35 years ago.
3. Individual growth rate of this amphipod was high in winter and spring but decreased in summer. Annual production of J. annandalei (6.2 g C m⁻² year⁻¹) was only 2% of primary production but was at the higher end of the range reported for amphipods in oligo- and mesotrophic lakes.
4. These results are consistent with the view that Lake Biwa is becoming more eutrophic, with a consequent decrease in the abundance of predatory fish in the profundal zone.     

中国特有植物巴山榧树的种群结构与动态

为了掌握中国特有裸子植物巴山榧树的种群现状,预测种群数量动态趋势,以分布于重庆、四川、陕西、湖北、安徽、河南和甘肃等省市的15个地点的残存巴山榧树种群为对象,建立巴山榧树种群径级结构和高度级结构图,编制种群静态生命表,绘制种群存活曲线、死亡率和消失率曲线,同时结合谱分析方法分析种群数量动态变化。结果表明:巴山榧树种群密度较低,平均为5.33株/100m~2,其中神农架种群(SN)密度最高,为9.58株/100m~2,城口种群(CK)密度最低,为2.75株/100m~2。径级结构中低龄级个体占有较高的比例,种群表现为增长型年龄结构;不同局域种群的径级结构差异明显,除宝兴种群(BX)外,其余种群的径级分布不完整。高度级结构中低于6m的个体占88.74%,绝大多数个体处于群落灌木层。种群的生命期望在不同龄级间波动明显,第3、7龄级的生命期望较低。巴山榧树种群存活曲线趋于Deevey-Ⅲ型;死亡率曲线和消失率曲线变化趋势一致,均在第3、7龄级出现峰值。巴山榧树种群的数量动态除受基波的影响外,在3、5、7龄级还显示出明显的小周期波动。巴山榧树为长寿命孑遗植物,呈岛屿化斑块分布,种群规模小,自然更新能力差,面临灭绝的危险,应及时加以保护。     

Population dynamics of small mammals in semi-arid regions: a comparative study of demographic variability in two rodent species

The seasonally determined demographic structure of two semi-arid rodents, both agricultural pest species (the leaf-eared mouse (Phyllotis darwini) in Chile and the multimammate mouse (Mastomys natalensis) in Tanzania), is analysed using capture-mark-recapture (CMR) statistical models and measures for elasticity (the relative change in the growth rate due to a relative unit change in the parameter of concern) derived from projection linear matrix models. We demonstrate that reproduction and survival during the breeding season contribute approximately equally to population growth in the leaf-eared mouse, whereas the multimammate mouse is characterized by a more clearly defined seasonal structure into breeding and non-breeding seasons and that reproduction contributes far more than survival during the breeding season. On this basis, we discuss evolutionary and applied (pest control) issues. Regarding the evolution of life histories (leading to a maximization of the overall net annual growth rate), we suggest that for the leaf-eared mouse, features favouring survival throughout the year will provide selective value, but that during the main breeding season, features favouring reproduction and survival are about equally favourable. For the multimammate mouse, features favouring survival are particularly important outside the breeding season, whereas during the breeding season features favouring reproduction are more important. Regarding pest control (aiming at reducing the overall net annual growth rate), we suggest that (ignoring economic considerations) affecting survival outside the main breeding season is particularly effective for the leaf-eared mouse, a feature that is even more the case for the multimammate mouse. In sum, we demonstrate through this comparative study that much is to be learnt from studying the dynamics of fluctuating small rodents-a focal issue within much of population ecology.     

Population dynamics of a diverse rodent assemblage in mixed grass-shrub habitat, southeastern Colorado, 1995-2000

We followed seasonal and year-to-year population dynamics for a diverse rodent assemblage in a short-grass prairie ecosystem in southeastern Colorado (USA) for 6 yr. We captured 2,798 individual rodents (range, one to 812 individuals per species) belonging to 19 species. The two most common species, deer mice (Peromyscus maniculatus) and western harvest mice (Reithrodontomys megalotis), generally had population peaks in winter and nadirs in summer; several other murid species demonstrated autumn peaks and spring nadirs; heteromyids were infrequently captured in winter, and populations generally peaked in summer or autumn. Inter-annual trends indicated an interactive effect between temperature and precipitation. Conditions associated with low rodent populations or population declines were high precipitation during cold periods (autumn and winter) and low precipitation during warm periods (spring and summer). Severity of adverse effects varied by species. Heteromyids, for example, were apparently not negatively affected by the hot, dry spring and summer of 2000. Cross-correlations for the temporal series of relative population abundances between species pairs (which are affected by both seasonal and interannual population dynamics) revealed positive associations among most murids and among most heteromyids, but there were negative associations between murids and heteromyids. These results have important implications for those attempting to model population dynamics of rodent populations for purposes of predicting disease risk.     

Ethiopian Population Dermatoglyphic Study Reveals Linguistic Stratification of Diversity

The manifestation of ethnic, blood type, & gender-wise population variations regarding Dermatoglyphic manifestations are of interest to assess intra-group diversity and differentiation. The present study reports on the analysis of qualitaive and quantitative finger Dermatoglyphic traits of 382 individuals cross-sectionally sampled from an administrative region of Ethiopia, consisting of five ethnic cohorts from the Afro-Asiatic & Nilo-Saharan affiliations. These Dermatoglyphic parameters were then applied in the assessment of diversity & differentiation, including Heterozygosity, Fixation, Panmixia, Wahlund’s variance, Nei’s measure of genetic diversity, and thumb & finger pattern genotypes, which were inturn used in homology inferences as summarized by a Neighbour-Joining tree constructed from Nei’s standard genetic distance. Results revealed significant correlation between Dermatoglyphics & population parameters that were further found to be in concordance with the historical accounts of the ethnic groups. Such inductions as the ancient north-eastern presence and subsequent admixure events of the Oromos (PII= 15.01), the high diversity of the Amharas (H= 0.1978, F= 0.6453, and P= 0.4144), and the Nilo-Saharan origin of the Berta group (PII= 10.66) are evidences to this. The study has further tested the possibility of applying Dermatoglyphics in population genetic & anthropologic research, highlighting on the prospect of developing a method to trace back population origins & ancient movement patterns. Additionally, linguistic clustering was deemed significant for the Ethiopian population, coinciding with recent genome wide studies that have ascertained that linguistic clustering as to being more crucial than the geographical patterning in the Ethiopian context. Finally, Dermatoglyphic markers have been proven to be endowed with a strong potential as non-invasive preliminary tools applicable prior to genetic studies to analyze ethnically sub-divided populations and also to reveal the stratification mechanism in play.     

特有珍稀植物宝华玉兰种群分布格局和群落特征

采用相邻格子样方法和典型样地法研究镇江宝华山国家森林公园珍稀植物宝华玉兰的种群分布格局和群落物种多样性。从分布格局看,宝华玉兰种群在半自然样地Q1中为聚集分布,但聚集强度不高,而在另外3个样地中均为随机分布。从群落特征看,4个样地共有维管植物89种,隶属于43科74属;群落分层明显,但宝华玉兰为亚优势种;半自然林中各层次的物种多样性Shannon-Wiener指数为草本层>灌木层>乔木层,而在自然样地中,则为草本层>乔木层>灌木层。     

The ecology of Hypogeomys antimena, an endemic Madagascan rodent

The subfamily Nesomyinae comprises 11 species of rodents endemic to the island of Madagascar. They show considerable ecological and anatomical diversity but little is known of their biology and they have not been studied to any extent in the wild. We present here the results of a nine-week field study of Hypogeomys antimena , the largest of the Nesomyinae, found only in a restricted area of dry deciduous forest in western Madagascar. Radiotracking data gave a mean home range estimate of 3.5+0.71 ha for 10 animals (five males, five females). Individuals from the same burrow had highly overlapping ranges but ranges of animals from neighbouring burrows showed minimal overlap. We suggest that H. antimena lives in social units, probably consisting of a pair plus their offspring, which occupy exclusive territories. A mark/recapture study gave a minimum population estimate of 48 animals/km² in the study site. The conservation of the species is discussed with reference to its limited distribution and current habitat degradation in the area.     

Forest dynamics in Hawaii

The land surfaces of the Hawaiian islands represent an age sequence from very recent on the island of Hawaii to over 5 million years old on the island of Kauai. Development of indigenous forest on the new basaltic lava flows of Hawaii begins with Metrosideros polymorpha forming mono-dominant canopy stands within 400 years in lowland rain forest environments. In seasonal environments, M. polymorpha is displaced during succession by species such as Acacia koa and Sophora chrysophylla. In the montane rain forest, M. polymorpha has persisted as the dominant canopy species over millions of years. The mechanism of longterm persistence in the latter biome is explained as resulting from two processes: periodic canopy breakdown or stand-level dieback and the appearance or evolution of successional varieties in M. polymorpha.     

Breeding seasonality and population dynamics of three rodent species in the Magamba Forest Reserve, Western Usambara Mountains, north-east Tanzania

We investigated breeding seasonality and population dynamics of three rodent species, Lophuromys flavopuncatus, Grammomys dolichurus and Praomys delectorum, in the Magamba Forest, Western Usambara Mountains, north‐east Tanzania. Capture–mark–recapture studies were conducted in 2002–2004. Reproductive conditions of males and females showed temporal variations, an indication of breeding seasonality. Animals were reproductively active between February and May. Rainfall in November–January was instrumental for the onset of breeding and continued throughout the wet season. The recruitment of new individuals born during the season led to highest population densities between end of May and August. Populations declined progressively towards the end of the dry season (September–October). Only P. delectorum showed a marked density increase during January–February, indicating greater survival and/or recruitment during the November–January rains. The study shows that despite a relatively stable environment of the forest reserve, rainfall has strong influence on reproduction and population dynamics, probably because of its effect on primary food resources.