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1.
Much of the world's insect and plant biodiversity is found in tropical and subtropical ‘hotspots’, which often include long elevational gradients. These gradients may function as ‘diversity pumps’ and contribute to both regional and local species richness. Climactic conditions on such gradients often change rapidly along short vertical distances and may result in local adaptation and high levels of population genetic structure in plants and insects. We investigated the population genetic structure of two species of Ficus (Moraceae) along a continuously forested elevational gradient in Papua New Guinea. This speciose plant genus is pollinated by tiny, species‐specific and highly coevolved chalcid wasps (Agaonidae) and represented by at least 73 species at our study gradient. We present results from two species of Ficus sampled from six elevations between 200 m and 2700 m a.s.l. (almost the entire elevational range of the genus) and 10 polymorphic microsatellite loci. These results show that strong barriers to gene flow exist between 1200 m and 1700 m a.s.l. Whereas lowland populations are panmictic across distances over 70 km, montane populations can be disjunct over 4 km, despite continuous forest cover. We suggest that the limited gene flow between populations of these two species of montane Ficus may be driven by environmental limitations on pollinator or seed dispersal in combination with local adaptation of Ficus populations. Such a mechanism may have wider implications for plant and pollinator speciation across long and continuously forested elevational gradients if generalist insect pollinators and vertebrate seed dispersers also form populations based on elevation.  相似文献   
2.
In the Northern Hemisphere, the surface of south-facing slopes orients toward the sun and thus receives a greater duration and intensity of solar irradiation, resulting in a relatively warmer, drier microclimate and seasonal environmental extremes. This creates potentially detrimental conditions for evergreen plants which must endure the full gamut of conditions. I hypothesize that (1) increased southerly aspect will correlate negatively with evergreen understory plant distributions; (2) derived environmental variables (summer and winter light and heat load) will predict variance in evergreen distributions as well as topographic position (aspect, slope, and elevation) and (3) winter light will best predict evergreen understory plant distributions. In order to test these hypotheses, survey data were collected characterizing 10 evergreen understory herb distributions (presence, abundance, and reproduction) as well as the corresponding topographical information across north- and south-facing slopes in the North Carolina mountains and Georgia piedmont. The best predictive models were selected using AIC, and Bayesian hierarchical generalized linear models were used to estimate the strength of the retained coefficients. As predicted, evergreen understory herbs occurred and reproduced less on south-facing than north-facing slopes, though slope and elevation also had robust predictive power, and both discriminated well between evergreen species. While the landscape variables explained where the plants occurred, winter light and heat load provided the best explanation why they were there. Evergreen plants likely are limited on south-facing slopes by low soil moisture combined with high temperatures in summer and high irradiance combined with lower temperatures in winter. The robust negative response of the understory evergreen herbs to increased winter light also suggested that the winter rather than the summer (or growing season) environment provided the best predictive power for understory evergreen distributions, which has substantive implications for predicting responses to global climate change.  相似文献   
3.
Eight novel polymorphic microsatellite loci are presented for the endangered land snail Trichia caelata, a rare species endemic to the Northwestern Jura mountains, Switzerland. The number of alleles per locus ranged from six to 17. At seven loci, the expected heterozygosity differed significantly from observed heterozygosity. No evidence for linkage disequilibrium was detected between locus pairs. We are currently using these markers to investigate the genetic population structure of T. caelata in its restricted distribution area.  相似文献   
4.
Climate change can harm many species by disrupting existing interactions or by favouring new ones. This study analyses the foreseeable consequences of climatic warming in the distribution and dynamics of a Mediterranean pest that causes severe defoliation, the pine processionary caterpillar Thaumetopoea pityocampa, and the effects upon the relict Andalusian Scots pine Pinus sylvestris nevadensis in the Sierra Nevada mountains (southeastern Spain). We correlated a set of regional data of infestation by T. pityocampa upon Scots pine, from a broad ecological gradient, with climatic data for the period 1991–2001, characterized by alternating warm and cold winters. Defoliation intensity shows a significant association with previous warm winters, implying that climatic warming will intensify the interaction between the pest and the Scots pine. The homogeneous structure of the afforested pine woodlands favours the outbreak capacity of the newcomer, promoting this new interaction between a Mediterranean caterpillar pest and a boreal tree at its southern distribution limit.  相似文献   
5.
Aim To calculate the degree to which differences between local and regional elevational species richness patterns can be accounted for by the effects of regional area. Location Five elevational transects in Costa Rica, Ecuador, La Réunion, Mexico and Tanzania. Methods We sampled ferns in standardized field plots and collated regional species lists based on herbarium and literature data. We then used the Arrhenius function S = cAz to correct regional species richness (S) for the effect of area (A) using three slightly different approaches, and compared the concordance of local and regional patterns prior to and after accounting for the effect of area on regional richness using linear regression analyses. Results We found a better concordance between local and regional elevational species richness after including the effect of area in the majority of cases. In several cases, local and regional patterns are very similar after accounting for area. In most of the cases, the maximum regional richness shifted to a higher elevation after accounting for area. Different approaches to correct for area resulted in qualitatively similar results. Main conclusions The differences between local and regional elevational richness patterns can at least partly be accounted for by area effects, suggesting that the underlying causes of elevational richness patterns might be the same at both spatial scales. Values used to account for the effect of area differ among the different study locations, showing that there is no generally applicable elevational species–area relationship.  相似文献   
6.
The members of the smut genus Microbotryum are pathogens of a wide range of host plant species from nine dicotyledonous families. Within the genus, the species sporulating in anthers of Caryophyllaceae form a monophyletic group that in recent years attracted much interest in various biological studies. The phylogenetic framework developed for species delimitation within Microbotryum revealed that high level host-specificity is a major feature of most caryophyllaceous anther smuts. However, the great number of anther smut specimens on diverse host plant species reported worldwide has still not been included in phylogenetic analyses due to the inaccessibility of recently collected specimens, and thus many species remain still undiscovered. In this study, anther smut specimens on Heliosperma pusillum originating from all main mountain ranges of the European Alpine System were examined using partial rDNA sequence and/or morphological analyses. The investigation revealed that all specimens are morphologically uniform and phylogenetically represent a monophyletic lineage, sister to Microbotryum lagerheimii complex on Atocion rupestre/Silene lacera/Silene vulgaris/Viscaria vulgaris. This lineage cannot be attributed to any of the previously described species, and therefore the smut in anthers of H. pusillum is described and illustrated here as a new species, Microbotryum heliospermae. The species is known from subalpine zone of the Alps, the Carpathians, the Dinaric Alps, and the Pyrenees, inhabiting host plants growing in open spring communities or semihumid mountain meadows.  相似文献   
7.
We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic carbon (DOC), K+, Na+, Ca2+, Mg2+, NO3 -N, NH4 +-N, PO4 3−-P, and SO4 2− were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations of NO3 -N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO4 2−, Ca2+, and Mg2+. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO3 -N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO3 -N increased four fold, and streamwater NO3 -N doubled. Significant changes also occurred in soilwater pH, DOC, SO4 2−, Ca2+, and Mg2+. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope. Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient uptake by canopy trees is a key control on NO3 -N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes significant nutrient loss to streams. Received 30 January 2001; accepted 25 July 2002.  相似文献   
8.
西藏色季拉山种子植物垂直带谱的划分与分布特点研究   总被引:4,自引:0,他引:4  
柴勇  樊国盛  李乡旺  郑维列 《广西植物》2004,24(2):107-112,106
将色季拉山种子植物分布划分为山地暖温带针阔混交林带、山地温带针叶林带、亚高山寒温带针叶林带、高山寒带疏林、灌丛、草甸带和高山荒漠带。在上述基础上 ,分析了各带谱的区系组成、性质和特有种分布特点。  相似文献   
9.
小相岭大熊栖息地干扰调查   总被引:10,自引:1,他引:9  
强烈的人类干扰是大熊猫濒危的主要原因。本于2001年6~7月对四川省小相岭大熊猫栖息地内竹子开花、火灾、滑坡3种自然干扰类型和采伐、放牧、采药、公路、偷猎、割竹采笋、耕作、开矿和旅游9种人类干扰类型进行了调查。调查样方878个,干扰发生在海拔1800~4000m。结果表明:自然干扰都不严重,干扰比例最高的竹子开花,也仅占1.14%。采伐、放牧、采药和公路是主要人类干扰类型,分别占调查总样方的34.9%,26.3%,5.1%和4.2%。干扰最严重的地段是海拔3000~3499m,采伐样方的49.67%,放牧样方的47.19%,采药样方的31.11%均发生在该段,同时有48.89%的大熊猫活动痕迹样方也在该海拔。近年来,由于国家实施“天然林保护工程”,采伐已不再是主要干扰,而放牧、采药和偷猎等活动在短时间内仍不会减少。  相似文献   
10.
以3S技术作为信息获取和处理的手段,将景观生态学原理与植被变化研究的传统方法相结合,对小相岭山系主要植被类型在近30年发生复杂相互转化的主要表现和动态变化特征进行量化分析。结果表明:(1)针阔叶混交林与针叶林的变化趋势相似,在30年中持续增长,增幅分别为17.57%、7.56%;新增斑块与原有斑块连接在一起,形成边界复杂的大斑块,景观破碎度和均匀性有所降低。(2)高山灌丛呈先减少后增加的变化趋势,在90年代面积与数量都有所回升,但新增斑块多数为尺寸较小的斑块,大量小斑块的出现导致景观破碎度和离散度有所增加。(3)高山流石滩植被在30年中不断减少,减幅为6.41%;由于减少的多是小斑块,因此破碎化程度并未加深,且分布的均匀性有所加强。研究结果不仅可以解释该山系主要植被景观格局与生态过程相互作用的机理,而且可以阐明其动态演替的方向、过程或扩展潜力。  相似文献   
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