Genetic (RAPD) diversity in Peromyscus maniculatus populations in a naturally fragmented landscape

We assessed the effects of long-term habitat fragmentation on genetic (random amplified polymorphic DNA) diversity in 11 Peromyscus maniculatus populations in the Lake Superior watershed. We analysed genetic structure at two spatial scales and the effect of island size and isolation on genetic diversity. At the regional scale, island populations differed from mainland populations (FST = 0.36), but mainland populations did not differ from each other (FST = 0.01). At the local scale, populations of the main island of Isle Royale differed from adjacent islet populations (P < 0.001; Monte Carlo approximation of Fisher's exact test), but not from each other (combined P = 0.63). Although geographical distance and genetic distance were positively correlated (P < 0.01; Mantel test), cluster analysis revealed some inconsistencies. Finally, genetic diversity was inversely related to isolation (P = 0.01), but had an unexpectedly negative relationship with island area (P = 0.03). The genetic structure of P. maniculatus populations in portions of the Lake Superior watershed appears to have been affected by long-term habitat fragmentation.     

Cross-scale drivers of plant trait distributions in a fragmented forest landscape

During community assembly, plant functional traits are under selective pressure from processes operating at multiple spatial scales. However, in fragmented landscapes, there is little understanding of the relative importance of local-, patch- and landscape-scale processes in shaping trait distributions. Here, we investigate cross-scale influences of landscape change on traits that dictate plant life history strategies in re-assembling plant communities in a fragmented landscape in eastern China. Using forest dynamics plots (FDPs) on 29 land-bridge islands in which all woody plants have been georeferenced and identified to species, we characterized and derived two composite measures of trait variation, representing variation across the leaf economics spectrum and plant size. We then tested for trait shifts in response to local-, patch- and landscape-scale factors, and their potential cross-scale interactions. We found substantial community-wide trait changes along local-scale gradients (i.e. forest edge to interior): more acquisitive leaf economic traits and larger sized species occurred at edges, with a significant increase in trait means and trait range. Moreover, there were significant cross-scale interaction effects of patch and landscape variables on local-scale edge effects. Altered spatial arrangement of habitat in the surrounding landscape (i.e. declining habitat amount and increasing patch density), as well as decreasing area at the patch level, exacerbated edge effects on traits distributions. We suggest that synergistic interactions of landscape- and patch-scale processes, such as dispersal limitation, on local-scale environmental filtering at edges, together shape the spatial distributions of plant life history strategies in fragmented plant communities.     

Arthropods on plants in a fragmented Neotropical dry forest: A functional analysis of area loss and edge effects

Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of arthropods associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators, and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of family richness with the reduction of forest fragment area was observed for the three functional groups, with similar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Family composition of herbivore, predator, and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of arthropods taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity.     

天坑森林植物群落叶功能性状、物种多样性和功能多样性特征

以天坑内部-边缘-外部森林植物群落为研究对象,通过调查植物的群落结构、叶功能性状,探究天坑内外森林植物群落叶功能性状、物种多样性和功能多样性变化特征及其内在关联,为深入了解负地形森林生态系统的功能和恢复退化喀斯特地区的植被提供一定参考。研究结果如下：（1）比叶面积（SLA: 198.75 cm2/g)）、叶面积（LA: 42.70 cm2）、叶磷含量（LPC: 1.70 g/kg）和叶钾含量（LKC: 10.27 g/kg）在天坑内部最高,叶组织密度（LTD: 0.32 g/cm3）和叶干物质含量（LDMC: 0.41 g/g）在天坑外部最高,天坑内外森林均易受到磷限制,表明随天坑内部-边缘-外部生境变化,植物对环境的适应机制和生存策略发生了部分调整,物种的防御策略增强,生长投入策略减弱。（2）Shannon-Wiener指数（2.82）、Simpson指数（0.92）和Pielou’s均匀度指数（0.87）均以天坑外部最高,功能丰富度（1.05）、功能离散度（1.88）和Rao’s二次熵（4.52）以天坑内部最高,表明随天坑内部-边缘-外部生境的变化,植物功能性状的差异减少,物种分布及其功能性状分布总体上更为均匀、物种数量增多。（3）物种多样性指数之间、功能多样性指数之间存在较强的相关性,表明物种多样性指数之间、功能多样性指数之间存在不同的制约关系。（4）叶功能性状与物种多样性、功能多样性的相关性强,物种多样性和功能多样性之间相关性较弱,表明叶性状对生态学过程的变化较为敏感,叶功能性状与物种多样性之间存在较强的耦合关系。     

Habitat amount drives the functional diversity and nestedness of anuran communities in an Atlantic Forest fragmented landscape

Natural environments disturbed by human activities can suffer from species extinctions, but some can still harbor high taxonomic diversity. However, disturbances may have impacts beyond the species level, if the species lost represent unique functions in the ecosystem. In this study, we evaluated to what extent the amount of habitat can determine the functional diversity and nestedness of amphibian communities in an Atlantic Forest fragmented landscape in Brazil, and if there is a threshold of habitat amount beyond which there is severe loss of functional diversity. As species responses may depend on their habitat type, we performed the analyses for three different sets of species: all species, forest‐dependent species, and generalist species. We also evaluated the relative importance of turnover and nestedness components to total functional dissimilarity among sites. Habitat amount affected functional diversity of frogs, especially for forest‐dependent species where a linear reduction was detected. The functional dissimilarity among sites was mostly explained by the nestedness component. The reduction of functional diversity was mediated by an ordered loss of traits, leading to a functionally nested metacommunity. These sensitive traits were closely related to habits and reproductive modes that depend on rivers and streams. The maintenance of functional diversity of frogs in fragmented landscapes must rely on the conservation of both terrestrial and aquatic environments, as some species and their traits can disappear from remnants of native vegetation lacking some specific habitats (e.g. streams). Abstract in Portuguese is available with online material.     

Landscape patterns and plant species diversity of forest reserves in the Kanto region, Japan

Plant species richness of twenty old-growth forest reserves in the cool-temperate zone in the Kanto region, Japan were investigated to detect the effect of forest fragmentation. The species richness of trees and forest floor plants were analyzed by multiple regression models relating to nine variables on the characteristics of landscape, local habitat and forest stand. The total species diversity did not have a significant correlation with any variables of landscape patterns. In this study, single large reserve in the SLOSS discussion did not seem very effective to preserve more species. However, forest reserves in large patches tend to have relatively infrequent species. Large patches of natural forests were regarded as one of the important factors to preserve infrequent species.     

亚热带次生常绿阔叶林植物功能性状及多样性对人工抚育的响应

亚热带次生常绿阔叶林普遍存在生长滞缓、固碳功能和经济价值低下等问题,迫切需要通过人工抚育提高其生态系统功能。对植物功能性状及其多样性的深入研究,能够找寻植物共存与群落稳定发展的内在机制,为提升森林生态系统功能的实践提供基础。为了探究人工抚育对亚热带次生常绿阔叶林质量提升的影响,以杭州午潮山国家森林公园内的次生常绿阔叶林为研究对象,实施了不同强度的抚育措施,通过群落植被复查,分析群落植物功能性状以及功能多样性对不同强度人工抚育的响应。结果发现:抚育2年后,群落最大潜在树高与叶片氮、磷、钾含量显著上升,而叶片干物质含量和叶片叶绿素含量均有显著下降,比叶面积有下降趋势,两种强度的抚育之间差异不显著;叶片干物质含量、叶绿素含量与叶片氮含量间的相关性由不显著变为了显著负相关,而叶片干物质含量与叶片叶绿素含量,叶片磷、钾含量与叶片氮含量,叶片磷含量与叶片钾含量间的相关性由不显著变为显著正相关;在20%强度抚育下,功能丰富度指数均值从对照的0.52显著下降为0.16,功能均匀度指数与功能分离度指数的均值则分别上升到0.61和0.67,显著高于对照组的0.51和0.56;在10%强度抚育下,功能丰富度有所下降,功能均匀度与功能分离度均有所上升,但差异不显著。研究表明,人工抚育在一定程度上改变了群落水平的植物功能性状与功能多样性,提高了群落植物利用资源的能力和效率;而适度的抚育强度更能解放资源空间,对群落产生的影响更加明显。该结果为亚热带次生常绿阔叶林的经营与管理提供依据与参考。     

Effects of habitat fragmentation on the functional diversity of insects in Thousand Island Lake,China

Due to habitat fragmentation, the loss of species diversity has been extensively studied. On the contrary, the effects of habitat fragmentation on functional diversity is still poorly understood. In the Thousand Island Lake, we conducted studies of insect functional diversity on a set of 29 isolated islands. We used 10 functional diversity indices from three aspects (functional richness, functional evenness and functional divergence) to respectively describe functional diversity of insects on sample islands. We found the following results: (i) The functional indices selected could reflect the functional diversity of sample islands and it is further proved that in general, three components of functional diversity were independent of each other; (ii) Sample islands could be divided into two categories, island JSD and the remaining islands; (iii) Functional richness increased with island area and shape index, but had no significant correlation with isolation. Likewise, both functional evenness and functional divergence had no significant correlation with island attributes. The conclusion to emphasize from our research is that: (i) habitat fragmentation reduced the biological functional diversity to some extent, further demonstrating the importance of habitat continuity in biodiversity protection; and (ii) for functional diversity protection of insects in a fragmented landscape, an island which has high approximate shape index values of at least hundred hectare magnitude order has a critical promoting effect.     

Tree and shrub diversity and abundance in fragmented littoral forest of southeastern Madagascar

In the coastal littoral forest of extreme southeastern Madagascar, westudied tree diameter at breast height (DBH) 10 cm in 20, 50× 50 m plots in each of four forest fragments, andunderstorywoody vegetation (DBH < 10 cm, 1 m tall) in60,10 × 10 m plots in three of the fragments. Oneforestfragment was located in the highly degraded Lokaro region, and three in the nearbySainte-Luce forest. Atotal of 3476 trees, representing 169 species in 55 families, were recorded inthe50 × 50 m plots, and 10282 understory stems, representing195 species in 54 families, were found in the 10 × 10m plots. For each tree, DBH was recorded. Mean tree diameter andpatterns of tree size class distribution did not differ among the four forestfragments. However, the fragments differed significantly in both tree andunderstory stem densities, species richness and diversity values, and familyrichness values, with the Lokaro fragment having the lowest values for allmeasures. Furthermore, floristic patterns, family importance values, and communitysimilarity measures revealed that the species composition at theLokaro fragment was very different from the Sainte-Luce fragments. Anthropogenicdisturbance appears most pronounced in the isolated Lokaro forest, where bioticresources are limited to this single fragment.     

千岛湖片段化景观中蜘蛛群落物种多样性和功能群结构及其影响因素

生境片段化对蜘蛛群落有着重要影响,目前这方面的研究较少,多集中于不同植被类型间蜘蛛群落的比较研究。在千岛湖片段化景观中选取16个陆桥岛屿,从2010年春季到2011年秋季,按季度(春、夏、秋季)6次采用Winkler法收集蜘蛛标本,分析其物种多度、多样性、季节动态和功能群差异,并对不同大小岛屿上蜘蛛的功能群的多度以及功能群比例差异进行单因素方差分析。结果表明:共收集到蜘蛛标本3503头,用于统计分析的成蛛1438头,归属于30科82种,其中幽灵蛛科(Spermophora)、管巢蛛科(Clubionidae)、螲蟷科(Ctenizidae)、蟹蛛科(Thomisidae)分别占总数的7.37%、6.61%、5.84%、5.29%,螲蟷科(Ctenizidae)在16个岛屿上均有分布。Shannon-Wiener指数在不同季节间差异显著(P0.05),物种丰富度在秋季最高。在功能群上,伏击型蜘蛛的多度最高,其次为游猎型蜘蛛,结圆网型蜘蛛多度最低,穴居型蜘蛛的多度与其他各功能群呈显著差异(P0.05);游猎型蜘蛛与伏击型蜘蛛的多度均显著高于结皿网型蜘蛛与结圆网型蜘蛛(P0.05);蜘蛛的各功能群数量在小岛与大岛这两种不同的岛屿类型上表现出显著差异,小岛上伏击型蜘蛛的物种数显著高于大岛上的物种数;比例上,结皿网型蜘蛛和伏击型蜘蛛在小岛上占功能群总体数目的比例显著低于大岛上的比例(P0.05),小岛上的游猎型蜘蛛占功能群总体数目的比例显著高于大岛上的比例(P0.05),结圆网型蜘蛛与穴居型蜘蛛在不同类型的岛屿间不存在显著差异。总体而言,秋季蜘蛛物种丰富度最高,蜘蛛的多样性与季节相关;生境片段化对蜘蛛功能群的分布产生了一定影响。     

功能多样性和谱系多样性对热带云雾林群落构建的影响

近年来, 功能多样性和谱系多样性为探究群落构建机制提供了新方法。为了更准确地了解海南岛高海拔热带云雾林群落构建机制, 该研究以海南岛霸王岭热带云雾林为对象, 测定7个环境因子和13个植物功能性状。利用主成分分析(PCA)筛选环境因子, 以霸王岭、尖峰岭和黎母山热带云雾林分布物种建立区域物种库, 结合模型, 分析Rao二次熵(RaoQ)和平均成对谱系距离(MPD)变化对植物群落构建的影响。结果表明: 林冠开阔度、土壤全磷含量和坡度是影响植物群落构建的关键环境因子。多数功能性状的系统发育信号很低且不显著, 说明热带云雾林群落的系统发育关系与功能性状随历史进程变化不一致。RaoQ和MPD的实际观测值都显著低于期望值, 且其标准效应值与土壤磷含量显著相关, 说明生境过滤是驱动热带云雾林群落构建的关键因子, 土壤磷含量是群落构建的关键环境筛。     

Positive interactions between herbivores and plant diversity shape forest regeneration

The effects of herbivores and diversity on plant communities have been studied separately but rarely in combination. We conducted two concurrent experiments over 3 years to examine how tree seedling diversity, density and herbivory affected forest regeneration. One experiment factorially manipulated plant diversity (one versus 15 species) and the presence/absence of deer (Odocoileus virginianus). We found that mixtures outperformed monocultures only in the presence of deer. Selective browsing on competitive dominants and associational protection from less palatable species appear responsible for this herbivore-driven diversity effect. The other experiment manipulated monospecific plant density and found little evidence for negative density dependence. Combined, these experiments suggest that the higher performance in mixture was owing to the acquisition of positive interspecific interactions rather than the loss of negative intraspecific interactions. Overall, we emphasize that realistic predictions about the consequences of changing biodiversity will require a deeper understanding of the interaction between plant diversity and higher trophic levels. If we had manipulated only plant diversity, we would have missed an important positive interaction across trophic levels: diverse seedling communities better resist herbivores, and herbivores help to maintain seedling diversity.     

Limited effect of anthropogenic habitat fragmentation on molecular diversity in a rain forest skink, Gnypetoscincus queenslandiae

To examine the effects of recent habitat fragmentation, we assayed genetic diversity in a rain forest endemic lizard, the prickly forest skink (Gnypetoscincus queenslandiae), from seven forest fragments and five sites in continuous forest on the Atherton tableland of northeastern Queensland, Australia. The rain forest in this region was fragmented by logging and clearing for dairy farms in the early 1900s and most forest fragments studied have been isolated for 50-80 years or nine to 12 skink generations. We genotyped 411 individuals at nine microsatellite DNA loci and found fewer alleles per locus in prickly forest skinks from small rain forest fragments and a lower ratio of allele number to allele size range in forest fragments than in continuous forest, indicative of a decrease in effective population size. In contrast, and as expected for populations with small neighbourhood sizes, neither heterozygosity nor variance in allele size differed between fragments and sites in continuous forests. Considering measures of among population differentiation, there was no increase in FST among fragments and a significant isolation by distance pattern was identified across all 12 sites. However, the relationship between genetic (FST) and geographical distance was significantly stronger for continuous forest sites than for fragments, consistent with disruption of gene flow among the latter. The observed changes in genetic diversity within and among populations are small, but in the direction predicted by the theory of genetic erosion in recently fragmented populations. The results also illustrate the inherent difficulty in detecting genetic consequences of recent habitat fragmentation, even in genetically variable species, and especially when effective population size and dispersal rates are low.     

广西马尾松林植物功能多样性与生产力的关系

探索植物多样性与生产力的关系可为森林经营与管理提供科学基础。本研究以广西4个地区的马尾松(Pinus massoniana)人工林群落为研究对象, 通过计算物种多样性、功能多样性和功能优势值, 运用相关分析、自动线性建模和方差划分等方法, 分析了多样性与生产力的关系。研究发现, 生产力与物种丰富度、Shannon指数、功能丰富度、功能均匀度极显著正相关(P < 0.01), 与物种均匀度、功能多样性、功能离散度、功能团个数、坡向显著正相关(P < 0.05), 与林龄极显著负相关(P < 0.01), 4个功能多样性参数和4个物种多样性参数两两之间皆为显著正相关; 未发现初始生物量制约生产力的提高; 方差划分最优模型中, 功能多样性参数效应、功能优势值效应和林龄效应分别解释生产力方差的56%、43%和33%, 功能多样性参数效应和功能优势值效应重叠部分高达27%; 生态位互补效应主要由功能丰富度和功能均匀度产生, 选择效应主要由生长型优势值产生; 生长型优势值为灌木的样地生产力较高, 次优种或过渡种对生态系统功能也有重要作用。以生产力为响应变量的自动线性建模最佳子集包括重要性由大到小的5个因素: 林龄、生长型优势值、功能丰富度、功能均匀度、功能团个数。建议维护森林功能多样性, 加强林下叶层植物保护, 用好功能重要的物种, 通过林下叶层的补偿性光合作用和生长竞争, 有效地提高生产力和生物多样性。     

喀斯特森林不同演替阶段植物群落物种多样性、功能性状、化学计量及其关联

探讨森林植物群落物种多样性、功能性状与化学计量特征及其内在关联,有助于构建结构-性状-功能的研究脉络,深入理解生态系统的过程与功能,为群落结构优化配置和调控提供科学依据。以贵州喀斯特高原峡谷区森林草灌、灌木、灌乔和乔木4个演替阶段的植物群落为对象,通过群落学调查和植物功能性状、生态化学计量测度,研究其物种多样性、功能性状和化学计量特征及其互作关系。结果表明:(1)乔木阶段的Shannon-Wiener指数与Pielou均匀度指数均为最高,依次达8.62、2.41,表明伴随着群落演替,物种分布的均匀程度增加。(2)植物群落物种多样性指数之间仅Margalef丰富度指数与Simpson优势度指数未呈显著相关(-0.644),其余均为显著或极显著相关关系,表明物种多样性指数之间存在较强的促进或抑制作用。(3)叶片厚度与其余指标,以及群落物种多样性指数与功能性状、化学计量之间均未呈显著相关,比叶面积(SLA)仅与土壤N∶P呈显著正相关(0.742),表明群落物种多样性、功能性状和生态化学计量特征之间的相关性较弱。(4)SLA为灌木阶段的272.13 cm2/g为最大,δ13C值在演替后期略高,草灌、灌木阶段倾向于受N、P共同限制,说明随演替进展,植物的适应策略和资源利用对策等均发生了一定的调整,表明植物和环境之间存在较强的协变关系。(5)该区森林培育时,应构建完整的乔木、灌木和草本层片,提高生态系统对养分矿化、转化和循环等的自调控能力。     

海南岛3个林区热带云雾林植物多样性变化

以分布在海南岛西部(霸王岭国家级自然保护区, 21个样方)、西南部(尖峰岭国家级自然保护区, 12个样方)和中部(黎母山省级自然保护区, 15个样方)的热带云雾林为研究对象, 研究α及β物种多样性、功能多样性、谱系多样性的变化, 为植物多样性的保护提供科学依据。结果表明: 尖峰岭群落树木个体多度、物种丰富度最大, 黎母山群落树木个体多度、物种丰富度最小; 黎母山群落间物种组成差异最大, 霸王岭群落间物种组成差异最小, 海南岛霸王岭(西部)、尖峰岭(西南部)和黎母山(中部) 3个林区热带云雾林物种多样性差异可能与空气温度和相对湿度有关。尖峰岭群落内功能丰富度、Rao’s二次熵最低, 功能均匀度最高, 群落间平均成对性状距离最小, 反映群落构建主要受环境筛影响; 霸王岭群落Rao’s二次熵最高, 功能均匀度最低, 群落间平均成对性状距离最大, 反映群落构建主要受限制相似性影响; 黎母山群落内功能丰富度最高, 群落间平均最近性状距离最大, 表明限制相似性在黎母山热带云雾林群落构建中的作用更重要。霸王岭群落内谱系多样性、物种间平均最近相邻谱系距离均较大, 反映物种间谱系关系趋于发散; 黎母山群落内谱系多样性、物种间平均成对谱系距离及群落间平均成对谱系距离均最小, 反映物种间谱系关系趋于聚集; 而尖峰岭群落内物种间平均成对谱系距离、群落间平均成对谱系距离最大, 但物种间平均最近相邻谱系距离最小, 反映物种间谱系关系既具有发散又具有聚集的共存格局。因此, 海南岛热带云雾林群落植物多样性变化格局与环境及物种间相互作用有关。     

Consequences of forest fragmentation in an understory plant community: extensive range expansion of native dwarf bamboo

Understory bamboo species are important and influential components of temperate forests in at least several parts of the world. Here we report a study testing the effect of forest fragmentation on the dynamics of the dwarf bamboo Sasa chartacea and on forest herb communities in the Tokachi plain of Hokkaido, Japan. We studied 16 forest fragments of different sizes and small plots established in these fragments to examine the relationship between the abundance of S. chartacea, landscape and environmental conditions, and forest herb communities. Sasa chartacea was more abundant near forest edges and in smaller fragments, suggesting that the species has expanded its local range and increased its abundance in response to forest fragmentation. Edge‐related changes in light and soil moisture might have facilitated this range expansion. The species richness of forest herbs was strongly negatively related to the density of S. chartacea. Because much larger variation in species richness was explained by S. chartacea density than distance to the nearest forest edge, the expansion of S. chartacea has likely excluded other understory species by competition. In addition, the density of S. chartacea significantly explained variation in the species composition of forest herbs across plots. Taken together, our results emphasize the key roles of dwarf bamboos in changing plant communities following forest fragmentation.     

The fragmented Atlantic rain forest of Brazil: size, shape and distribution of forest fragments

The geographical characteristics of a total of 1839 forest fragments surrounded by sugar cane fields were studied in the Brazilian Atlantic rain forest region of the northeastern state of Pernambuco. The size and shape of the fragments as well as inter-fragment distances and the effects of varying edge width were examined using a geographical information system. The analyses show that the fragments are relatively small and close to each other. Approximately 48% of the rain forest fragments are <10 hectares, while only about 7% are >100 hectares. Forest fragments are close to each other, as fragments located 50m or less apart formed groups that included ca. 50% of the total forest area. At 350m inter-fragment distance, 98% of the rain forest area was included in groups of fragments. Due to the small size and irregular shape of the fragments, the total area of edge zone exceeds that of the interior habitat when the edge width is ca. 60m. At an edge width of 300m ca. 94% of the total fragment area is edge zone. For conservation purposes, ways of establishing networks of forest fragments connected by corridors and stepping stone fragments are demonstrated using GIS. Simulations using these techniques show that reforestation of sugar cane fields between the forest fragments would considerably increase the area of interior forest habitat and connectivity between fragments.