Analysis and understanding of butterfly community composition based on multivariate approaches and the concept of generalist/specialist strategies

We analyzed butterfly community composition using multivariate analyses. The results of principal components analysis showed that the butterfly community was composed mainly of two species groups. This species grouping was also supported by the results of the cluster analysis (unweighted pair‐group method using arithmetic average). Comparing the present results with species classification based on the generalist/specialist concept, the butterfly community was found to be composed of five species groups differing from each other in their ecological characteristics: a specialist group, two intermediate groups and two generalist groups. By comparison of their characteristics, it was suggested that, in the butterfly community, the positions of the specialist group and one of the generalist groups are the endpoints on the generalist/specialist selection spectrum, and the three other groups are positioned between these two extremes. The multivariate analyses showed that the species grouping with the generalist/specialist concept based only on voltinism and larval diet breadth was not sufficient to classify both intermediate and generalist groups, and also succeeded in extracting a typical generalist group from the butterfly community. From these results, we propose and recommend the synergetic application of the generalist/specialist concept and multivariate approaches to the detailed analysis and deeper understanding of community structure and composition.     

Patterns in the structure of grassland butterfly communities along a gradient of human disturbance: further analysis based on the generalist/specialist concept

Kitahara and Fujii, in 1994, analyzed the butterfly communities along a gradient of human disturbance by applying the generalist/specialist concept. Butterfly species were classified into generalist or specialist species based on their voltinism (seasonal time dimension) and potential larval resource breadth (food dimension). The community structure and species composition showed the systematic changes along the gradient. To verify the generality of those trends, we monitored five grassland butterfly communities with varying degrees of human disturbance twice a month during 1985 by the line transect method at the foot of Mt. Fuji, central Japan, and analyzed their structure in a manner similar to that employed by Kitahara and Fujii. Most results were consistent with the patterns recognized by Kitahara and Fujii. The route (community) order based on increasing human disturbance was strongly and negatively correlated with butterfly species richness but with neither butterfly species diversity (H′) nor evenness (J′). Also, the degree of human disturbance was significantly and negatively correlated with the number of specialist species, but not with that of generalists, in a community. Butterfly species richness was more strongly correlated with the number of specialist species than with that of generalists. Our analyses also showed that the generalist species were distributed more widely over the communities than were the specialists. However, in contrast to the trend revealed by Kitahara and Fujii, there was no significant difference in the population densities and in the spatial population variability between the two species groups. As a whole, our analyses confirmed the consistency of most community patterns detected by Kitahara and Fujii. The causes of the inconsistencies in some patterns were thought to be mainly the present habitat conditions with a relatively short growing season at high altitudes. Received: October 19, 1999 / Accepted: June 5, 2000     

人为干扰对壶瓶山国家级自然保护区蝴蝶物种多样性的影响

为了解人为干扰对壶瓶山国家级自然保护区(以下简称壶瓶山保护区)蝴蝶物种多样性的影响, 调查组于2017-2018年间采用样线法抽取5条样线对壶瓶山保护区的蝴蝶群落进行调查研究, 分析了人为干扰对蝴蝶发生规律的影响, 并比较了壶瓶山保护区中不同程度人为干扰情况下的蝴蝶发生差异。本调查共观测到蝴蝶6,711只, 隶属5科19亚科119属190种, 各样线的优势种主要有宽边黄粉蝶(Eurema hecabe)、东方菜粉蝶(Pieris canidia)、酢浆灰蝶(Pseudozizeeria maha)、宽带凤蝶(Papilio nephelus)等。轻度干扰情况下物种多样性最高, 其次为无干扰条件, 而中度干扰情况下蝴蝶物种多样性最低, 即小规模的耕作-居住环境有利于蝴蝶的聚集, 而增加现有的人为干扰程度或扩大干扰范围, 可致使群落中蝴蝶物种数减少、优势类群数量增加。     

A comparison of the diversity and structure of butterfly communities in semi-natural and human-modified grassland habitats at the foot of Mt. Fuji, central Japan

To examine the effects of human land use and disturbance on butterfly communities we compared the diversity and structure of communities in relatively undisturbed, semi-natural grassland habitats and highly disturbed, human-modified ones. Comparisons were based on transect counts conducted at 6 study sites at the foot of Mt. Fuji in the cool temperate zone of central Japan during 1995. Out of the six community parameters used in the analyses, the species richness, species diversities H and 1/, and dominance indices were significantly different between the two habitat types stated above. That is, butterfly communities in semi-natural habitats had higher species richness and diversity, and lower dominance indices than those in human-modified ones. This suggests that heavy land modification and disturbance to semi-natural habitats change greatly its butterfly community structure, which, indeed, leads to decreasing species richness and diversity mainly due to the loss of species that are confined to semi-natural habitats. Through the comparisons of various species' characteristics, it was found that the species confined to semi-natural habitats had lower population abundance, fewer generations per year, more restricted local distributions, and narrower geographic range size in Japan than the other component species. Based on our results, it is critical that the persistence of the species that are limited to semi-natural habitats be ensured in order to maintain high species richness and diversity in grassland butterfly communities. Thus, conservation plans that retain as much semi-natural habitat as possible within the process of human grassland use, development, and modification are needed.     

水淹干扰下水库水滨带植物群落谱系结构与物种多样性格局

群落谱系结构将物种系统发育信息整合到群落中,给生物多样性研究提供了全新视角。为探讨水淹干扰下水库水滨带植物群落物种多样性维持机制,以丹江口水库水滨带为研究区域,以南水北调中线一期工程运行前的原有水滨带植被为研究对象,分析不同水淹干扰强度下群落谱系结构和物种多样性及其与环境因素的关系。结果表明：(1)随着水淹干扰强度增加,群落物种丰富度、物种多样性和谱系多样性显著降低。谱系结构指数虽无显著差异,但随着水淹干扰强度增加呈现由发散到聚集的变化趋势。表明水滨带植物群落物种多样性维持机制是生境过滤和生态位分化共同驱动的结果,并且随着水淹干扰强度增加呈现生境过滤作用增加、物种间竞争排斥作用减弱的生态过程影响规律。(2)坡度、土壤质地、速效氮和全氮含量对整个水滨带植物群落物种丰富度、物种多样性和谱系多样性影响显著。此外,土层厚度和速效磷对物种丰富度和土层厚度对谱系多样性也影响显著。而仅有速效氮含量对谱系结构指数影响显著;轻度水淹干扰下坡向、速效磷含量与多样性指数显著相关;中度水淹干扰下坡度、土层厚度、土壤质地、土壤总氮含量与多样性指数显著相关,土壤pH、全氮和全磷含量与谱系结构指数显著相关;重度水淹...     

Effects of human disturbance on liana community diversity and structure in a tropical rainforest,Malaysia: implication for conservation

Aim Due to the important role of lianas in the functioning of forest ecosystem, knowledge of the factors that affect them are important in the management of forests. Currently, there are conflicting reports on the response of liana communities to disturbance, calling for more research in the area. The present study was carried out to investigate the response of liana diversity and structure to human disturbance within two major forests in the Penang National Park, Malaysia. The study also looked at the implication of the findings for conservation.Methods A total of 15 40 × 40-m 2 (or 40-m × 40-m) plots each were randomly located across a range of habitats in a primary forest and disturbed secondary forest. Trees with diameter at breast height ≥10 cm were examined for lianas with diameter ≥2 cm. Both lianas and trees were enumerated and compared between the two forests. Diversity and structural variables of lianas were compared between the two forests using the t -test analysis. Tree abundance was also compared between the two forests with t -test, while linear regression analysis was run to determine the effects of tree abundance on liana abundance.Important findings A total of 46 liana species belonging to 27 genera and 15 families were identified in the study. Human disturbance significantly reduced liana species richness and species diversity in the secondary forest. Liana abundance remained the same in both forests whereas liana basal area was significantly higher in the primary forest. Twiners and hook climbers were significantly more abundant in the primary and secondary forest, respectively. Large diameter lianas were more abundant in the primary forest compared with the secondary forest. The diameter distribution of most families in the primary forest followed the inverted J-shaped curve whereas only a few of the families in the secondary forest did so. Tree abundance was significantly higher in the primary forest. The abundance of lianas significantly depended on tree abundance in all the forests. The study has provided evidence of negative effects of human disturbance on liana diversity and structure that does not auger well for biodiversity in the forest. In view of the critical role of lianas in maintaining biodiversity in the forest ecosystem, lianas in the national park should be protected from further exploitation.     

张广才岭温带次生针阔混交林物种组成和群落结构特征

为了研究温带次生针阔混交林的树种组成和群落结构特征,于2010年在吉林省蛟河林业实验区管理局建立了面积为21.84 hm2(420 m×520 m)的固定样地。从物种组成、种-面积曲线、植物区系特征、径级分布结构和空间分布格局等方面分析了该地区针阔混交林物种组成和群落结构特征。研究结果表明该样地共有DBH≥1.0 cm的木本植物活立木个体25,908株,隶属于18科27属45种,植株密度为1186株/hm2。植物区系以北温带分布属为主体,共有37属,占总数的82.22%,属长白山植物区系。样地内稀有种18种,偶见种14种。通过对该样地物种多样性计算得出,该样地Margalef多样性指数R、ShannonWienner指数H'、Simpson多样性指数D和物种均匀度Pielou指数Jsw分别为4.31、2.48、0.89和0.65。样地中所有个体的径级分布(以2cm等级排列)呈偏倒"J"形,整体更新良好,表现出群落稳定与生长状况良好的趋势。群落中重要值3的9个物种的径级结构表现出一定的差异:胡桃楸、水曲柳呈近似正态分布,表现为中径木个体数量多,而小径木和大径木个体数量少的特点;春榆、大果榆、色木槭、白牛槭、裂叶榆等物种呈倒"J"型或偏倒"J"型,更新良好;而红松由于受到了严重的人为干扰,天然更新不良,径级结构呈现不规律型。通过g(r)双变量函数分析9个优势树种空间分布格局可知,9个优势树种均表现出聚集分布,聚集强度随着尺度的增大而降低。在r20 m的小尺度上物种聚集强度随尺度增大急剧降低,当尺度超过20 m后聚集强度趋于稳定。     

人为干扰对川西金凤山楠木次生林群落结构和物种多样性的影响

物种多样性是群落功能复杂性和稳定性的重要量度指标,人为干扰对森林群落的影响可以通过群落结构和物种多样性的变化直接表现出来,不同干扰强度下群落结构和多样性特征不同。金凤山景区主要有选择性采伐和旅游活动这两种人为干扰形式,为研究不同强度人为干扰对金凤山楠木次生林群落的多样性和稳定性的影响,在实地充分考察的基础上,将干扰强度划分为3个等级:重度干扰:紧靠核心景区0—40 m,中度干扰:距离核心景区40—80 m,轻度干扰:远离核心景区80—120 m,采用典型取样法,调查3种不同强度的人为干扰对群落不同林分层次的物种组成、群落结构和多样性的影响,采用物种丰富度指数S值、Shannon-Wienner指数H值、Simpson优势度指数D值和均匀度指数Jsw值来综合衡量群落的物种多样性水平。结果表明:(1)在总面积为3600 m2的9个样地中,共记录到维管束植物155种,隶属于69科136属;物种数随着人为干扰强度增加呈递减趋势,轻度、中度和重度干扰下群落的物种数依次为:113种,88种,77种。(2)从群落结构上看,轻度和中度干扰下乔木个体多分布在小中径级(4胸径DBH20 cm)和低中高度级(5高度H13 m);而重度干扰下乔木个体多分布在小径级(DBH8 cm)、大径级(DBH≥28 cm)和低高度级(3H7 m)、高高度级(H≥15 m),其群落结构与轻度和中度干扰下乔木层的群落结构明显不同。(3)受不同强度人为干扰的楠木次生林群落各物种多样性指数大小排序为:轻度干扰中度干扰重度干扰,S值、H值和Jsw随着人为干扰强度的增加而降低。     

Assessing the net effect of anthropogenic disturbance on aquatic communities in wetlands: community structure relative to distance from canals

Anthropogenic alterations of natural hydrology are common in wetlands and often increase water permanence, converting ephemeral habitats into permanent ones. Since aquatic organisms segregate strongly along hydroperiod gradients, added water permanence caused by canals can dramatically change the structure of aquatic communities. We examined the impact of canals on the abundance and structure of wetland communities in South Florida, USA. We sampled fishes and macroinvertebrates from marsh transects originating at canals in the central and southern Everglades. Density of all aquatic organisms sampled increased in the immediate proximity of canals, but was accompanied by few compositional changes based on analysis of relative abundance. Large fish ( >8 cm), small fish ( <8 cm) and macroinvertebrates ( >5 mm) increased in density within 5 m of canals. This pattern was most pronounced in the dry season, suggesting that canals may serve as dry-down refugia. Increases in aquatic animal density closely matched gradients of phosphorus enrichment that decreased with distance from canals. Thus, the most apparent impact of canals on adjacent marsh communities was as conduits for nutrients that stimulated local productivity; any impact of their role as sources of increased sources of predators was not apparent. The effect of predation close to canals was overcompensated by increased secondary productivity and/or immigration toward areas adjacent to canals in the dry season. Alternatively, the consumptive effect of predatory fishes using canals as dry-season refuges is very small or spread over the expanse of marshes with open access to canals. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

福建黄岗山东南坡和西北坡乔木物种多样性及群落特征的垂直变化

利用福建黄岗山东南坡30个样方和西北坡13个样方的资料,研究该地区乔木物种丰富度的垂直变化;东南坡共记录到乔木物种151种,隶属于42科73属;西北坡102种,隶属于32科54属。两坡面的乔木树种组成相差不大。物种丰富度随海拔的变化趋势是：随海拔升高,科、属、种的数量呈下降的趋势;东南坡科、属、种的数量在海拔800—1000m达到最大值,西北坡在海拔1500—1600m达到最大值。东南坡乔木物种Shannon—Wiener指数(H’)与海拔呈负相关;西北坡在海拔1200—1800m范围内H’高于东南坡;Screnson指数(IAc)在不同植被类型交替时出现上下波动,从常绿阔叶林向针阔混交林转化时,物种更替强烈,Screnson指数明显下降。乔木物种生长特征的分析表明,最大树高(Hmax)和最大胸径(DBHmax)出现在中海拔,在相同海拔范围内西北坡的Hmax和DBHmax高于东南坡;东南坡Hmax和DBHmax的峰值出现在海拔800—900m,西北坡出现在海拔1800m。东南坡立木密度在海拔1500m处达最高值,而西北坡立木密度变化不明显,仅在海拔1900m以上明显下降。将全部乔木种划分为常绿阔叶、针叶和落叶阔叶等三种生活型,分析不同生活型的生长特征发现,常绿阔叶种类的胸高断面积和(total basal area,TBA)在低海拔占比例大;针叶种类沿海拔出现两个峰值,与分布两种不同针叶林种类有关;落叶阔叶林的TBA在各海拔段均占一定比例,但在西北坡的比例要高于东南坡。两坡三种生活型的TBA沿海拔梯度变化特征基本上相似。     

富营养化对小型湖泊浮游甲壳动物群落结构及多样性的影响

2017年3月到2018年2月研究了临涣湖浮游甲壳动物群落结构的季节变化。临涣湖共记录浮游甲壳动物13种,其中枝角类8属8种,桡足类5属5种。短尾秀体溞(Diaphanosoma brachyurum)、广布中剑水蚤(Mesocyclops leuckarti)和象鼻溞(Bosmina sp.)等小型富营养种类是温暖季节的优势种,而近邻剑水蚤(Cyclops vicinus)是冬季的优势种。盔形溞(Daphnia galeata)等大型种类仅在少数月份中被观察到。临涣湖浮游甲壳动物的年平均密度和生物量分别为28.3个/L和0.33 mg/L。营养状态指数(TSI_M)的年平均值为62.6。浮游甲壳动物的Shannon指数、Pielou指数和Simpson指数的年平均值分别为0.86、0.74和0.49,且3种多样性指数均具有显著的季节差异。营养盐水平、营养状态指数和物种多样性指数均表明,临涣湖水体处于富营养化状态。冗余分析结果表明,水温、总磷浓度和叶绿素a浓度是影响临涣湖浮游甲壳动物群落结构变化的上行效应因子。鲢、鳙鱼的捕食压力是临涣湖浮游甲壳动物群落结构小型化的下...     

Patterns of liana community diversity and structure in a tropical rainforest reserve,Ghana: effects of human disturbance

Most studies have concluded that liana diversity and structure increase with disturbance. However, a contradictory pattern has emerged recently calling for more research in the area. Liana diversity and structure were investigated in three forest types that differ in disturbance intensity (nondisturbed, moderately disturbed and heavily disturbed forest: NDF, MDF and HDF, respectively) in the Atewa Range Forest Reserve, Ghana. In each forest type, 10 square plots of 0.25 ha were demarcated. Lianas with diameter ≥1 cm located on trees with diameter ≥10 cm were enumerated. A total of 429 individuals representing 40 species, 29 genera and seventeen families were identified in the study. Shannon diversity and species richness of lianas were significantly lower in the HDF (P < 0.05). Liana density and basal area differed significantly across all forest types (P < 0.0001). The importance value index (IVI) of most liana species varied greatly across the forest types. The current study has provided evidence to support the pattern of decreasing liana diversity and structure with disturbance in some tropical forests. Further studies are recommended to gain more understanding of the factors that are responsible for the divergent liana responses to disturbance in tropical forests.     

Plant community responses to nitrogen addition and increased precipitation: the importance of water availability and species traits

Global nitrogen (N) enrichment and changing precipitation regimes are likely to alter plant community structure and composition, with consequent influences on biodiversity and ecosystem functioning. Responses of plant community structure and composition to N addition and increased precipitation were examined in a temperate steppe in northern China. Increased precipitation and N addition stimulated and suppressed community species richness, respectively, across 6 years (2005–2010) of the manipulative experiment. N addition and increased precipitation significantly altered plant community structure and composition at functional groups levels. The significant relationship between species richness and soil moisture (SM) suggests that plant community structure is mediated by water under changing environmental conditions. In addition, plant height played an important role in affecting the responses of plant communities to N addition, and the effects of increased precipitation on plant community were dependent on species rooting depth. Our results highlight the importance and complexity of both abiotic (SM) and biotic factors (species traits) in structuring plant community under changing environmental scenarios. These findings indicate that knowledge of species traits can contribute to mechanistic understanding and projection of vegetation dynamics in response to future environmental change.     

Forest characteristics and population structure of a threatened palm tree Caryota obtusa in the karst forest ecosystem of Yunnan,China

中国云南石灰岩山地森林系统中受到威胁的董棕的森林特征和种群结构 别具魅力的董棕(Caryota obtusa)属于棕榈科(Arecaceae)的树种,在中国西南地区、印度、缅甸、泰国、老挝和越南有自然分布。董棕是一个具有重要经济价值且受到人为活动威胁的物种,其在云南的一些石灰岩山地乔木层占据优势。本研究的目的是阐明在云南石灰岩山地森林生态系统中董棕的群落结构、物种多样性、种群现状及其更新动态。为了全面深入的调查董棕群落,我们在云南南部10个县设置56个样方。根据样方数据,我们分析了群落的垂直结构、物种组成和种群结构,并对当地村民进行问卷采访记录了长期以来人为活动对董棕林的干扰情况。研究结果表明,董棕棕榈林分布在石灰岩山坡和沟谷,有7个群落类型。每个群落的垂直结构明显,分为乔木层、灌木层和林床。群落物种组成丰富,各群落类型的木本物种和草本物种的香农-维纳多样性指数均在2.1–3.8。董棕在胸径级上的分布为多峰型,属间歇性更新,且依赖于一定的自然干扰,董棕小树主要在无人为干扰或人为干扰小的群落中出现,重度人为干扰严重地阻碍了董棕的更新,其次的中度人为干扰也给董棕的更新带来了一定的困难。     

气候变化对冬季东海外海中下层游泳动物群落结构及重要经济种类的影响

以全球气候变暖为主要特征的全球气候变化对海洋生物和海洋生态系统造成的影响已引起国际学者的高度关注。根据中国14家国营渔业公司底拖网渔业生产和渔业资源大面定点调查获得的17种中下层渔业数据,结合1960—2011年东海北部水域海表温度的变化情况,利用Fox模型移除捕捞效应产生的趋势变化后,分析了气候变化对中、下层游泳动物群落结构及几种重要经济种类的影响。通过气候跃变检验分析发现,海表温度在整体变暖的趋势上叠加有年代际波动,研究水域分别在1982/1983年发生了从寒冷期(1960—1982年)向升温期(1983—1998)、经由1998/1999年再到温暖期(1999—2011年)的跃变。群落结构变化特征显示:相比于寒冷期,温暖期间底层类和大型捕食类资源指数降低,中层类和无脊椎类升高;暖水种资源指数升高,暖温种降低;生物多样性指数略有增加。移除捕捞效应后,对不同生态属性种类CPUE与海表温度距平进行相关分析显示:底层类、中层类和无脊椎类残差与海表温度距平均呈正相关关系,其中中层类与海表温度距平显著正相关,而大型捕食类则呈负相关关系;暖水种残差与海表温度距平呈正相关,而暖温种则呈负相关关系。中层类中的黄鲫(Setipinna taty)、银鲳(Pampus argenteus)的CPUE残差均与海表温度距平呈显著正相关关系,近底层类中的带鱼(Trichiurus japonicus)和头足类(Squid)的CPUE残差均与海表温度距平呈正相关关系,而底层类小黄鱼(Larimichthys polyactis)和对虾(Shrimp)则呈负相关关系。在气候变化的大背景下,需加强其对海洋生态系统结构和功能影响的研究,查明渔业资源对气候变化的响应机制和机理,制定科学有效的渔业管理制度,实现渔业资源的可持续发展。     

Effects of Ulva spp. and seasonal disturbances on the recovery of a temperate rocky intertidal community

The inhibitory effects of ulvoid algae and their seasonality on the recovery and succession of an intertidal algal community were investigated under field conditions using a two‐factorial design. The experiment was conducted in the mid‐low intertidal zone on the Southern coast of Korea. In spring and fall, each of the ten 50 × 50 cm plots was disturbed artificially, and Ulva spp. were continuously excluded from five plots of the seasonal plots. The succession of spring plots was nearly twice as fast as that of the fall plots (spring, 4–6 months; fall, 10–15 months), indicating that the seasonal effects contributed significantly to the speed of the succession. The inhibition by Ulva species delayed the succession; however, the strength of this delay was limited largely by the duration and persistence of Ulva mass, which was also highly seasonal. The presence of Ulva spp. did not alter the final assemblage at the climax stage; instead, it caused a delay in community resilience. This study provides a few analytical factors for community‐wise comparison during the evaluation of the status of successional stages.     

中国生物多样性核心监测指标遥感产品体系构建与思考

生物多样性的稳定维持关乎人类生存发展与地球健康。生物多样性核心监测指标(Essential Biodiversity Variables, EBVs)旨在结合地面调查与遥感技术, 为大尺度、长时间序列的生物多样性监测提供新的解决方案。然而, 目前学界仍然缺乏一套国家尺度标准化EBVs遥感监测产品数据集, 以进行生物多样性评估。本研究旨在对中国生物多样性核心监测指标遥感产品进行体系构建与思考, 首先综述了目前EBVs的遥感研究概况, 并根据EBVs研究文献的数量进行调研分析; 同时, 本文在已有遥感生物多样性产品优先标准的基础上, 添加了“可重复性”的新标准, 并据此构建了中国EBVs遥感产品体系与监测数据集的指标清单, 最终对中国EBVs遥感研究存在的问题进行思考与讨论。本研究可为中国的生物多样性遥感监测提供科学依据, 有望为中国生物多样性政策的制定提供支撑。     

坡向和坡位对四川夹金山灌丛群落结构与物种多样性特征的影响

研究不同坡向、坡位夹金山灌丛群落结构和物种多样性特征。结果表明: 在 24 个样地中,共有维管植物 186 种,隶属于 50 科 127 属。其中,灌木层有 32 种,隶属于 14 科 22 属,阴坡下坡位物种数最多;草本层有 154 种,隶属于 43 科 109 属,阴坡物种数最少。灌木层的平均高度表现为阳坡>半阳坡>阴坡,平均密度则相反;草本层平均高度表现为阴坡>半阳坡>阳坡,平均密度无显著变化。坡位仅对阳坡草本层平均高度有显著影响,灌木层物种多样性在阴坡较高,草本层物种多样性在阳坡下坡位和阴坡中坡位较高。坡向对灌木层和草本层 Shannon多样性指数、Simpson优势度指数、物种丰富度指数、Pielou均匀度指数影响显著(除草本层 Simpson 指数),坡位对灌木层和草本层物种多样性指数均无显著影响,坡向和坡位的交互作用对草本层物种多样性的影响大于灌木层。冗余分析(RDA)表明,物种多样性不仅与坡向正弦值、坡向余弦值相关,也与群落结构特征相关性较大。     

An invasive fish species within its native range: community effects and population dynamics of Gambusia affinis in the central United States

1. Management of invasive species benefits from detailed information on the biology of the invaders, both from where they have already invaded, and from within their areas of origin. Western mosquitofish, Gambusia affinis, is a widely invasive and destructive freshwater fish. However, within its native range, G. affinis co‐exists with many other fish species in a wide variety of habitats without obvious harm. 2. In this study, we used data on fish communities within the native range of G. affinis at 154 sites across a broad spatial scale to examine the effects of G. affinis on species richness and diversity of residual (species other than G. affinis) fish assemblages. We further used data based on annual samples at eight fixed river sites over 18 summers to examine temporal population dynamics of G. affinis and to test factors associated with population fluctuations. 3. Higher residual species richness occurred in the presence of G. affinis, but residual diversity did not differ. We found an inverse relationship between relative abundance of G. affinis and residual species richness (although effect size was extremely small), but no effect on residual diversity. 4. Gambusia affinis populations fluctuated markedly across summers at all eight fixed sites, but population sizes at a site over time were not autocorrelated. However, population fluctuations were highly correlated among sites across all years, suggesting that regional factors influenced population size. Regional abundance of G. affinis did not correlate with drought, rainfall or winter temperature, but varied with spring temperature. We suggest earlier onset of reproduction in warmer springs resulted in larger summer populations. 5. Overall, within its native range, G. affinis does not appear to impact negatively on the assemblages in which it occurs, possibly due to fluctuations in its density. These findings suggest that introduced Gambusia populations, and those of other invasive species, warrant careful monitoring over long periods of time where they have invaded. Long‐term monitoring of new populations can establish if they are prone to ‘boom and bust’ dynamics, in which case the invader may be less a threat than sometimes assumed. Population information from long‐term studies, either in their native ranges or at invaded sites, can thus help to form the basis of prudent, cost‐effective management strategies for invasive organisms.