横断山区干旱河谷川滇蔷薇种子休眠与萌发的地理空间差异

通过测定横断山区干旱河谷18个川滇蔷薇种群新采集种子以及低温层积8周种子的发芽率和发芽速度,分析发芽率和发芽速度与种子特征以及环境因子之间的关系,阐明川滇蔷薇种子休眠与萌发的地理空间差异及其影响因素。结果表明,18个川滇蔷薇种群种子具有不同程度的休眠,新采集种子发芽率变化幅度大,为15.8%±5.0%至82.7%±2.3%,发芽速度指数范围：2.3%±0.2%至5.3%±0.5%。不同种群种子发芽率和发芽速度差异显著。新采集种子的发芽率在流域间存在显著差异,表现为金沙江流域 > 雅砻江流域 > 大渡河流域和岷江流域。新采集种子的发芽率和发芽速度随着采集地点海拔的升高而显著增加,即种子休眠程度随着海拔的升高呈现降低趋势。低温层积8周显著提高了种子发芽率和发芽速度,但减弱了种子发芽率和发芽速度在流域以及海拔间的差异。偏相关分析表明：瘦果皮厚度与新采集种子萌发速度成显著负相关关系;环境因子中年蒸发量与发芽率以及发芽速度之间关系最为密切,成极显著正相关关系;其次为年降水量,与发芽率和发芽速度之间具有显著的负相关关系。综合分析表明,川滇蔷薇种子休眠与萌发在横断山区干旱河谷存在较强地理空间差异。环境因子中年蒸发量和年降水量以及植物自身特征瘦果皮厚度是引起种子休眠与萌发地理空间差异的主要因素。     

不同水系松潘裸鲤的形态特征分析

为了解岷江、大渡河、雅砻江和金沙江水系松潘裸鲤Gymnocypris potanini的形态差异,采用常规形态学和多变量形态度量学方法比较分析了采自这4个水系206尾样本的形态特征。结果显示,各水系间松潘裸鲤的第一鳃弓外侧鳃耙数和背鳍、胸鳍、腹鳍及臀鳍鳍条数之间的差异无统计学意义;主成分分析显示,头部(吻端至胸鳍起点/体长、吻端至头背部末端/体长、头长/体长)和尾部特征值(尾鳍背部起点至臀鳍起点/体长、臀鳍起点至尾鳍腹部起点/体长)对形态影响最大;判别分析发现,岷江和雅砻江安宁河种群与其他种群明显分开;聚类分析显示,岷江水系种群聚为一支,金沙江、大渡河、雅砻江水系种群聚为另一支,金沙江水系种群聚在一起,大渡河和雅砻江水系种群未按水系聚在一起,而其聚类关系与种群间的地理距离基本一致;形态差异系数分析显示,可根据臀鳞行列长进行亚种的区分。大渡河和雅砻江水系的松潘裸鲤为硬刺松潘裸鲤亚种。     

岷江干旱河谷多苞蔷薇生长与繁殖特征

通过大面积野外踏查和样方调查,分析了岷江干旱河谷乡土灌木多苞蔷薇种群的分布、生长繁殖特征及其空间差异性.结果表明,多苞蔷薇广泛分布于岷江干旱河谷汶川绵褫至松潘镇江关约170 km长、海拔1 200～2 600 m的空间范围内,其株高、基径、年龄、冠幅、萌蘖株数和结实量的平均值分别为(123.33±3.13) cm、(12.49±0.40) mm、(3.34±0.16) a、(1.30±0.13) m²、(5.07±0.39)株/丛和(171.47±25.90)果/丛.随着海拔高度和纬度增加,其株高、基径、冠幅和结实量增加,而萌蘖株数没有显著变化.多苞蔷薇有性结实和无性萌蘖能力随环境空间变化的不匹配性与其生长密切相关,可能与多变环境下资源分配利用的平衡机制有关;以丛进行年龄统计,多苞蔷薇缺少幼龄个体,种群发展并不稳定,但随海拔高度升高,萌蘖株年龄结构均呈“金字塔”型,且较大龄级的萌株比例略增,显示出良好的种群持续性.综合分析发现,多苞蔷薇生长与繁殖的空间差异性是对干旱河谷长期适应的结果,既为种群持续提供了保证,也为种群扩大奠定了基础.     

岷江干旱河谷黄蔷薇和川滇蔷薇更新能力及其限制因素

植物种子、种子库和幼苗库的研究是种群更新和植被恢复的重要内容.研究了岷江干旱河谷两种乡土灌木(黄蔷薇和川滇蔷薇)的种子、种子库和幼苗库特征.黄蔷薇和川滇蔷薇种子产量较高, 分别为(627±216)和(7832±4347)果/丛,但种子质量较差,饱满率分别为(49.62±1.03)%和(73.83±3.42)%,活力为(32.25±0.67)%和(55.38±2.5)%.黄蔷薇种子产量和活力低于川滇蔷薇,但其种子重量和休眠程度却远高于川滇蔷薇.两种蔷薇土壤种子库的水平和垂直分布格局相似:在水平分布上,离植株基部越近,种子密度越高;在垂直分布上,种子主要分布在地表层.黄蔷薇和川滇蔷薇种子库密度均较高,分别为(560±90)粒m2和(1955±235)粒/m2,但活力种子数量较少,分别为(26±4)粒/m2和(152±18)粒/m2, 处于休眠状态的种子,黄蔷薇(60.6%)较川滇蔷薇(18.4%)高,可萌发的种子,两者分别为(10±1)粒/m2和(124±14)粒/m2.黄蔷薇(65.3%)的种子库中被啮齿动物取食的比例较川滇蔷薇(0.5%)高.两种蔷薇的幼苗密度差异不大,黄薇幼苗密度((4.28±0.49)株/m2)略小于川滇蔷薇((5.24±1.28)株/m2).幼苗组成的总体趋势是高度级低的幼苗所占的比例相对较高,且Ⅰ级幼苗数显著高于较其他级幼苗数.研究表明,两种蔷薇种子存在休眠,能形成持久种子库,种子特征对种子库和幼苗库具有深刻影响.两种蔷薇更新状况不佳,比较而言,黄蔷薇更新较川滇蔷薇好.黄蔷薇更新的主要限制因素是动物对种子的破坏,而川滇蔷薇更新的主要限制因素是幼苗存活定居.     

文冠果种群繁殖方式及其在种群更新中的作用

以黄土高原丘陵区文冠果天然种群为研究对象,通过样地调查,分析了不同生境文冠果种群的有性和无性繁殖方式及其在种群更新中的地位.结果表明：不同坡向文冠果种群均能进行有性繁殖和无性繁殖,在阳坡、半阴坡生境,文冠果以有性繁殖为主,实生苗数量和占据空间的能力均大于萌生苗,有性繁殖在这2个生境中对种群的更新贡献较大;在半阳坡生境,文冠果以无性繁殖为主,萌生苗数量和占据空间的能力均大于实生苗,无性繁殖对种群更新的贡献较大.在相同生境条件下,文冠果幼苗生长状况均表现为萌生苗＞实生苗.同一起源的文冠果幼苗生长状况均表现为阳坡＞半阳坡＞半阴坡.2种繁殖的瓶颈期在实生苗的种子-幼苗阶段和萌生苗的幼树-成株阶段.黄土丘陵区文冠果种群在新生境定居下来的过程中,首先以实生苗入侵,当水分、光照、养分条件较好时,文冠果又以无性繁殖方式迅速占领空间,繁衍后代.     

岷江柏天然种群种实表型变异特征

运用巢式方差分析、变异系数、表型分化系数和聚类分析等多种分析方法,研究了11个岷江柏种群的13个种实表型性状在种群内和种群间的变异及其与环境因子间的关系,并对其进行了类群划分.结果表明: 岷江柏种实表型性状在种群间和种群内均存在显著差异,种群内的变异(49.7%)大于种群间的变异(28.6%),种间平均分化系数为43.4%,分化程度相对较大.球果质量的平均变异系数最高(37.2%),其次是单个球果种子质量,球果长的平均变异系数最小(8.0%),是最稳定的种实性状.康定县的表型多样性最丰富,武都县的最小.在岷江柏的研究区内,最热月的平均气温和生长季的水分条件是其种实表型的主要限制因子.依据13个种实表型性状将11个岷江柏天然种群分为2类3亚类,基本上代表了3个流域的种群分布情况.大渡河流域种群种实表型性状最佳,岷江流域最差.     

川西三大干流水电开发影响区种子植物区系研究

在对川西雅砻江、大渡河和岷江三大干流水电开发影响区种子植物进行调查的基础上,对其区系特征进行了统计分析和比较研究,结果表明:(1)岷江和大渡河影响区裸子植物科、属、种数量多于雅砻江,被子植物属、种数量远少于雅砻江.(2)在科水平上均具有明显热带区系性质;在属水平上显示出热带和暖温带性质,雅砻江影响区热带属的比例高于温带属,岷江和大渡河则相反.(3)中国种子植物属15大分布区类型在岷江影响区均有分布,在雅砻江、大渡河各有1项没有出现.(4)大渡河和岷江影响区优势科属较雅砻江明显.(5)大渡河影响区属的系数"相对最低,区系丰富度较大.(6)岷江影响区特有属最多,雅砻江最少.(7)雅砻江和岷江影响区珍稀濒危及保护物种较大渡河多.     

岷江干旱河谷黄蔷薇(Rosa hugonis)生长与繁殖特征及其空间差异

对乡土植物生长繁殖特征的认识是制定合理的植被恢复及管理措施的基础和依据.通过大面积的野外踏查和样方调查,分析了岷江干旱河谷乡土灌木-黄蔷薇(Rosa hugonis)的分布、生长繁殖特征及空间差异.发现:(1)黄蔷薇主要分布于岷江干旱河谷的茂县段,其植株株高、基径、年龄、丛冠幅、丛的萌生数、丛干重、丛生物量和密度等生长特征存在明显空间差异,除丛萌生数和密度之外海拔对其他各参数都有较大的影响,这些参数的值在高海拔地段大于低海拔地段;(2)黄蔷薇在干旱河谷丛平均萌生数为6.48±0.97株/丛,丛的萌生能力较强,且其受砍伐后具有很强的再生能力;萌生株年龄结构大致为金字塔型,最大植株年龄为25a;(3)干旱河谷黄蔷薇的结实量较大,平均值为(404.96±106.91)果/丛,结实特征表现出明显的空间差异性;(4)各生长与结实参数关系密切,影响结实量的最主要的生长因素是冠幅和丛干重.研究结果表明:黄蔷薇适应干旱河谷的环境条件,具有较广泛的分布,生长和和繁殖状况良好,是可供选择的干旱河谷恢复物种.     

藏东南川滇高山栎种群不同生长阶段的空间格局与关联性

运用点格局分析方法中Ripley L函数,对藏东南川滇高山栎种群不同生长阶段的空间格局及其关联性进行分析.结果表明： 藏东南川滇高山栎种群径级结构呈单峰型,小树与中树的数量在整个种群中占绝对优势,整个种群自然更新状况良好,属增长型种群.川滇高山栎种群在从小树发育到大树的过程中,小树、中树在小尺度上均呈明显的聚集分布,而大树在整个尺度上基本上呈随机分布.小树与中树、大树间在小尺度上有显著的相关性,而中树与大树不相关.川滇高山栎种群在从小树、中树发育到大树的过程中,其空间格局由聚集分布到随机分布.川滇高山栎种群的自然更新受种间竞争的影响,也受种内竞争的影响.在自然环境条件相似下,影响川滇高山栎种群分布格局的最主要因素是其自身的生物、生态学特性.     

雅砻江和大渡河干旱河谷植被物种多样性比较:气候、地形与空间的影响

干旱河谷植被是我国西南横断山区的一类特殊的隐域性生态系统, 影响不同河谷之间植物群落差异的因素与作用大小尚不清楚。本研究调查了四川省雅砻江和大渡河流域干旱河谷段植被组成, 并比较了两个地区在植物多样性上的差别。结果表明: (1)影响两个地区植被类型的主要因素不同, 雅砻江干旱河谷植被主要受海拔和地形(坡度和坡向)影响, 大渡河干旱河谷植被主要受年平均降水量影响。(2)雅砻江和大渡河干旱河谷植物物种丰富度均随着年均温升高而降低。(3)坡向由北至南, 雅砻江干旱河谷灌木、草本物种丰富度减小, 而大渡河干旱河谷灌木、草本丰富度增加。(4)坡度越大, 雅砻江和大渡河干旱河谷灌木的丰富度越高。(5)雅砻江、大渡河干旱河谷植物β多样性受环境距离影响大, 受地理距离影响小。两条江植被间地理隔离效应约为地理距离产生差异的5倍。本研究弥补了干旱河谷研究中对于雅砻江和大渡河干旱河谷植物多样性研究的空白, 为相关区域植被保护提供了参考信息, 同时还为定量估计地理隔离效应对区域间生物多样性差异的影响提供了可行方法。     

Phylogeographic structure of <Emphasis Type="Italic">Terminalia franchetii</Emphasis> (Combretaceae) in southwest China and its implications for drainage geological history

Following the rapid uplift of the Qinghai-Tibetan Plateau, the reorganization of the major river drainages in southwest China was primarily caused by river capture events. However, the impact of these past changes in drainage patterns on the current distribution and genetic structure of the endemic flora of this region remains largely unknown. Here we report a survey of amplified fragment length polymorphism (AFLP) in Terminalia franchetii, an endemic shrub or small tree of the deep and dry-hot river valleys of this region. We surveyed AFLP variation within and among 21 populations (251 individuals) of T. franchetii, distributed disjunctively between northern and southern drainage systems. Using STRUCTURE, principal coordinates analysis, and genetic distance methods, we identified two main population genetic groups (I and II) and four subgroups within the species, as follows: (I) the Upper Jinshajiang Valley (subgroup I_(north)) and the Honghe drainage area (subgroup I_(south)); (II) the Middle and Lower Jinshajiang and Yalongjiang Valleys (subgroup II_(north)) and the Nanpanjiang drainage area (subgroup II_(south)). Genetic diversity was lower in group I than in group II. According to the genetic diversity and genetic structure results, we suggest that the modern disjunctive distribution and associated patterns of genetic structure of T. franchetii result from vicariance caused by several historical drainage capture events, involving the separation of the Upper Jinshajiang, Yalongjiang and Daduhe from the Honghe or Nanpanjiang in southwest China.     

Chloroplast DNA variation and phylogeography of Ligularia tongolensis (Asteraceae), a species endemic to the Hengduan Mountains region of China

In this research, we aimed to study the genetic variation and phylogeographic pattern of Ligularia tongolensis, a perennial herb endemic to the Hengduan Mountains region of China. We sequenced two chloroplast DNA (cpDNA) intergenic spacers (trnQ-5 rps16, trnL-rpl32) in 140 individuals from 14 populations of three groups (Jinshajiang vs. Yalongjiang vs. Wumeng) within this species range. High levels of haplotype diversity (Hd = 0.814) and total genetic diversity (Ht = 0.862) were detected at the species leve...     

Differences in morphological growth trajectories between greenside darter Etheostoma blennioides populations from two distinct drainages

The greenside darter Etheostoma blennioides is a small-bodied benthic stream fish that occurs in multiple drainages of the eastern USA. Previous studies have revealed some morphological differentiations among greensides from isolated drainage systems but growth relationships among functional morphological characteristics have not been examined within and between populations. Specifically, we tested for differences in functional morphology and allometric distinctions in morphological growth trajectories between greenside populations from two drainages, the Osage River and White River. Morphological differences between individuals of the two drainages included more dorso-ventrally compressed bodies, longer snouts and larger jaw features in White River darters. Furthermore, body depth, snout length and jaw width grow at significantly different trajectories in individuals of the two drainages. Individuals of the White River drainage (generally a higher gradient stream system) become comparatively more streamlined and develop proportionately larger feeding related traits during growth. These results suggest that individuals of both drainages share a similar morphology during early life but deviate during continued development and this may be partially due to environmentally induced plastic response. This study represents a novel approach for comparing morphological development among fish populations and presents environmental factors (e.g., stream gradient and elevation) that potentially influence functional characteristics.     

Variation and covariation among life-history traits in Rumex acetosella from a successional old-field gradient

In this study morphological variation and the potential for competition to affect biomass and seedling selection of the families of five populations of Rumex acetosella L. sampled along a successional old-field gradient have been investigated. Seeds from 25 families were submitted to four competitive regimes: no competition (one plant per pot), medium competition (two plants/ pot taking plants from the same population), high within-population competition (four individuals from the same population in a pot) and high between-population competition (four individuals from two different populations in a pot). Eight traits were analysed after 3 months of growth for variation among families within populations. A significant difference among families within the two older populations was recorded for sexual biomass and related components. High sensitivity of these traits to density was observed in all populations except the youngest, suggesting specialization to particular environmental conditions in late successional populations, and a good adaptive capacity to buffer environmental variation in the pioneer population. Little significant interaction between competitive regimes and families within populations was found, i.e. genotypes within each population showed little variation in their response to environmental variation. Genotypic variance decreased with increasing competitive conditions for the majority of the traits. However, the percentage of variance in sexual reproduction explained by family was stable among treatments. Tradeoffs between vegetative reproduction and sexual reproduction were recorded at the population level along the successional gradient, with increasing competitive conditions. As succession proceeds, we observed a decrease in sexual reproduction and an increase in vegetative reproduction. At the family level, correlation among traits were similar when plants were grown in the absence of competition and at high density, with a significant negative correlation between sexual reproduction and vegetative reproduction. For both sprout number and sexual biomass, the performance of families grown under all the treatments was positively correlated. Together these results indicate allocational constraints on the reproductive biology of R. acetosella that may be favoured by natural selection and have influenced population differentiation along the successional gradient. However, they also revealed that the potential exists for evolutionary specialization through plasticity, in response to variation in environmental conditions.     

Sex allocation under simulated herbivory in the generalist perennial herb Paeonia broteroi (Paeoniaceae)

Theories of optimal resource allocation in flowering plants postulate that allocation to sexual functions are balanced. While many studies have found such evidence in hermaphroditic species among flowers, plants or populations, or at different phenological stages, it has not been supported by other studies. This has been explained by differences among genotypes in ability to acquire resources, resource partitioning among traits unrelated to reproduction or strong selection to maintain positive genetic correlation among traits. I studied how herbivory affected resource allocation to sexual functions in the perennial herb Paeonia broteroi (Paeoniaceae) by measuring a number of floral traits in control plants and in experimental plants under simulated herbivory. The species shows very little plasticity in resource allocation between sexual structures and functions, and appears to be highly sensitive to alterations in the balance of resource acquisition and allocation, with an immediate outcome in terms of seed production and a mid-term response in terms of sprouting and flowering. Plants' ability to collect resources for growth and reproduction before their senescence at the end of the reproductive season, are compromised. This may limit their reproductive potential, the maintenance and growth of their populations, and may influence their demographic state and the plants' ability to respond to selective pressures by external biotic agents.     

云南高山姬鼠头骨的几何形态学研究

表型可塑性是指同一基因型在不同环境条件下而产生多种不同表现型的反应能力。哺乳动物头骨形态的变化是在进化过程中出现的重要表型特征之一。云南省地势西高东低、海拔变化剧烈、是古北界寒带物种南迁,中南半岛热带物种北移的交汇地,自然环境的地带性和非地带性变化明显,栖息在该地区的动物为了适应多样的环境,可能出现不同的表型分化。高山姬鼠(Apodemus chevrieri)为我国特有种,主要分布在中国西南的横断山及其附近地区,是研究表型与生态适应之间关系的理想物种。为研究在云南特殊生态环境下物种的微进化,采用几何形态学的方法测量云南不同地区高山姬鼠头骨形态的变异,采用线粒体细胞色素b(Cytochrome b,Cyt b)基因和线粒体控制区(Mitochondrial control region,D-loop)探讨基因型的变化。结果显示:昆明种群与横断山种群(中甸、剑川、丽江)间发生了明显的形态变异和遗传分化,高山姬鼠头骨背面和腹面,横断山种群和滇中昆明种群很少重叠,这两个种群变异较大;但头骨的侧面和下颌侧面变异不明显。因此,分布于云南地区的高山姬鼠可能正处于生态物种形成的早期阶段。     

Allozyme variation and population differentiation of the Aconitum delavayi complex (Ranunculaceae) in the Hengduan Mountains of China

The Aconitum delavayi complex is a group of four climbing species with trisect-leaves occurring in the Hengduan Mountains. The species of this complex are highly localized on very narrow regions with quite small population sizes. Because of rapid environmental changes recently in the Hengduan Mountains, this complex shows complicated morphological variability, which makes it difficult to delimit species. In the present study, 10 enzyme systems coding for 14 putative loci were employed to detect the interspecific and intraspecific genetic variation of the complex. In addition to low genetic diversity within all eight populations surveyed, the results indicate that A. episcopale is a distinct species because of high genetic identities among its three populations. Very low genetic divergence among populations of A. stapfianum and A. delavayi suggests that the two species should be treated as a single one.     

Reproductive investment and somatic growth rates in longear sunfish

Synopsis Allocation of energy to current reproduction at the expense of other functions, such as growth, can limit future reproductive potential. This cost of reproduction is a central concept of life history theory but has been difficult to verify in comparative field studies. Three levels of comparison of growth rates and reproductive investments were evaluated within and among populations of longear sunfish,Lepomis megalotis. All three demonstrated high levels of reproductive investment associated with reduced somatic growth. Within populations of central longear sunfish there are precociously mature sneaker makes and later maturing parental makes; sneakers have greater gonadosomatic index (GSI) values and slower somatic growth rates than parental makes. Between subspecies of longear sunfish grown under common conditions, there are differences in age at maturity and in the level of physiological reproductive investment that are associated with distinct differences in growth rates. Between populations of central longear sunfish inhabiting different sites, there are differences in the level of reproductive investment that are also associated with differences in somatic growth. Each comparison produced evidence that trade-offs occur between these life history traits, supporting the hypothesis that there is a cost of reproduction among male sunfish and suggesting that differences in strategies of reproductive investment contribute to variation in somatic growth.     

Population genetic structure of the tropical moss Acanthorrhynchium papillatum as measured with microsatellite markers

Mosses and other bryophytes are vital components of forests, because they sustain a tremendous diversity of invertebrates and influence significant ecological functions. There have been few studies on moss population diversity in Southeast Asia, despite the escalating deforestation in this region of rich biodiversity. The genetic diversity of the tropical moss Acanthorrhynchium papillatum (Harv.) Fleisch., collected from forested areas in Singapore and Peninsular Malaysia, was elucidated using eight microsatellite markers developed for this species. Significant levels of allelic and haplotypic diversity were observed among clumps of the moss. Differences in allelic richness and genotypic diversity among the populations were higher in less disturbed forests compared to the more disturbed areas, suggesting that genetic diversity is affected by habitat quality. Genetic diversity levels within the clumps studied were low, indicating that vegetative reproduction was more important within clumps than sexual reproduction. However, multilocus genotypes of samples within the clumps studied were not all alike, providing evidence of microsatellite mutation or of occasional sexuality. Despite the isolation of populations, A. papillatum can introduce genetic variability by mutation among vegetatively propagated individuals. This study provides baseline information on the genetic diversity of A. papillatum tropical rain forests.