Bromeliad architectural complexity and vertical distribution predict spider abundance and richness

Habitat complexity is a main predictor of the distribution of arthropods on vegetation. However, it remains poorly known whether plant architecture and fine‐scale spatial distribution affect the species richness and composition of associated arthropod guilds. In this study, we extensively sampled bromeliad species with a variety of rosette architectures in a megadiversity region. The aims were to investigate whether (i) possible differences in spider species composition among bromeliad species are related to the distinct architectures of the plants, and (ii) bromeliad architectural complexity (an intrinsic feature) and vertical distribution (an extrinsic feature) are good predictors of spider abundance and richness. Contrary to our expectations, spider species composition did not vary significantly among bromeliad species with different architectures. We found a positive effect of the mean number of leaves on spider abundance and species richness, but it occurred indirectly through spider abundance; factoring out the indirect effect revealed a negative effect of leaf number on species richness. Bromeliad species with wider vertical distributions harboured more spider species. Our results suggest that the dominance of a few spider species and reduced space for orb‐web spiders to attach their webs are the main explanations for lower spider richness on bromeliad species with higher architectural complexity. Our findings highlight the importance of both intrinsic and extrinsic plant features as co‐determinants of predator arthropod diversity.     

Effects of Seasonality and Dispersal on the Ciliate Community Inhabiting Bromeliad Phytotelmata in Riparian Vegetation of a Large Tropical River

This study evaluated the influence of rainfall amount on the abundance, species richness, and species occurrence and abundance distribution of the ciliate community associated with the bromeliad Aechmea distichantha. The plants were collected from a rock wall of about 10‐km long at the left bank of Paraná River. We assessed the effects of both spatial and temporal variables on the community attributes, as well as whether plants geographically closer have a similar abundance distribution and species composition. The ciliate community was substantially distinct between both hydrological periods, with greater values of species richness and abundance in the rainy period. No spatial structuring (differences in the species occurrence and abundance distribution among strata) or geographical similarity (similarity in ciliate species composition among the plants) was found. Multiple regression analysis showed a positive relationship only between the ciliate abundances and water volumes for both periods. Although few of the formulated predictions were confirmed, our study provides valuable information on the ecological aspects of the ciliate community inhabiting bromeliad phytotelmata.     

Species richness,composition, and abundance of fish larvae and juveniles inhabiting natural and developed shorelines of a glacial Iowa lake

Synopsis Young-of-the-year fish communities in naturally vegetated sites were compared with those inhabiting nearby sites where lakeshore development (i.e., construction of homes, boat docks, and beaches) reduced nearshore macrophyte species richness and abundance. The study was conducted in a 2266 hectare, glacially formed, eutrophic lake in northwestern Iowa during the summers of 1987 and 1988. Study sites were divided into 3 depth zones, and fishes were collected by seining (0–1 m), plexiglass traps (1–2 m), and a nonclosing Tucker trawl (2–3 m). Species richness and total fish abundance were consistently greater in natural than in developed sites in both nearshore (0–1 m) and intermediate (1–2 m) depth zones, but differed little between natural and developed sites in the offshore (2–3 m) depth zone. Nearly 50% of the species sampled, including yellow perch Perca flavescens and bluegill Lepomis macrochirus, inhabited limnetic areas as larvae before migrating inshore as juveniles. Eighteen of the 20 fish species collected as juveniles were in greater abundance in natural than in developed sites. Smallmouth bass Micropterus dolomieui was the only game species consistently found in equal or greater abundance in developed sites. Within all sites, juvenile fishes were generally most abundant where macrophyte abundance and species richness were greatest. Findings from this study demonstrate the importance of nearshore aquatic vegetation to fishes during their first summer of life. If nearshore vegetation beds of lakes continue to be regarded as a nuisance and indiscriminately removed, important fish nursery habitat will be lost. The short-term result will likely be reduced year-class strength of vegetation-dependent species. More importantly, the long-term effects will be changes in fish community richness and composition which will, in turn, alter the lake's fishery.     

Impacts of an invasive willow (Salix × rubens) on riparian bird assemblages in south‐eastern Australia

We explored how a woody plant invader affected riparian bird assemblages. We surveyed 15 200‐m‐long transects in riparian zones in a much‐changed landscape of eastern Victoria, Australia. Abundance, species‐richness, foraging‐guild richness and composition of birds were compared in transects in three habitat types: (i) riparian zones dominated by the invasive willow Salix × rubens; (ii) riparian zones lined with native woody species; and (iii) riparian zones cleared of almost all woody vegetation. We also measured abundance and richness of arthropods and habitat structure to explore further the effects of food resources and habitat on the avifauna. We observed 67 bird species from 14 foraging guilds. Native riparian transects had more birds, bird species and foraging guilds than willow‐invaded or cleared transects. Habitat complexity increased from cleared to willow‐invaded to native riparian transects, as did abundance of native and woodland‐dependent birds. Native shrub and trees species had more foliage and branch‐associated arthropods than did willows, consistent with a greater abundance and variety of foraging guilds of birds dependent on this resource. Willow spread into cleared areas is unlikely to facilitate greatly native bird abundance and diversity even though habitat complexity is increased. Willow invasion into the native riparian zone, by decreasing food resources and altering habitat, is likely to reduce native bird biodiversity and further disrupt connectivity of the riparian zone.     

Aquatic invertebrate communities in tank bromeliads: how well do classic ecological patterns apply?

Tank bromeliads (Bromeliaceae) often occur in high densities in the Neotropics and represent a key freshwater habitat in montane forests, housing quite complex invertebrate communities. We tested the extent to which there are species richness–altitude, richness–environment, richness–size, richness–habitat complexity and richness–isolation relationships for the aquatic invertebrate communities from 157 bromeliads in Cusuco National Park, Honduras. We found that invertebrate species richness and abundance correlated most strongly, and positively, with habitat size, which accounted for about a third of the variance in both. Apart from bromeliad size (equivalent of the species–area relationship), we found remarkably little evidence of classic biogeographic and ecological relationships with species richness in this system. Community composition correlated with altitude, bromeliad size and position, though less than 20% of the variation was accounted for by the tested variables. The turnover component of dissimilarity between the communities correlated with altitude, while the nestedness-resultant component was related to bromeliad size. The unexplained variance could reflect a large stochastic component in the system, associated with the ephemerality of the habitat patches (both the plants themselves and the fluctuations in their water content) and stochasticity due to the dispersal dynamics in the system. We conclude that there is a small contribution of classic biogeographic factors to the diversity and community composition of aquatic invertebrates communities in bromeliads. This may be due to the highly dynamic nature of this system, with small patch sizes and high emigration rates. The patterns may mostly be driven by factors affecting colonisation success.     

三峡水库蓄水对消涨带植被的初步影响

三峡库区消涨带植被一直受到广泛关注。为了研究水库蓄水对175 m以下消涨带原有植被的潜在影响,2008年8月在三峡大坝上游长江干流从巴南到秭归12个监测点,设立68个5 m×5 m永久监测样方,比较被水淹过的156 m以下与当时尚未水淹的156～175 m地段植被物种组分、物种多样性和草本层生物量的差异。结果表明：被水淹过与尚未水淹的植被物种组分存在显著差异,DCA可以将二者明显分开,156 m以上尚未水淹的植被以灌丛为主;156 m以下被水淹过的植被以草丛为主,优势种包括多年生草本：狗牙根（Cynodon dactylon）、牛鞭草（Hemarthria altissima）和硬秆子草（Capillipedium assimile）;一年生草本：狗尾草（Setaria viridis）、毛马唐（Digitaria ciliaris）和千金子（Leptochloa chinensis）。木本植物基本死亡,只有枫杨（Pterocarya stenoptera）、牡荆（Vitex negundo）和地瓜（Ficus tikoua）存活。此外,被水淹过的植被中灌木物种数比例显著降低,而一年生草本物种数比例显著增加。被水淹过和尚未水淹植被的物种多样性也存在显著差异,被水淹过植被物种总数、灌木和多年生草本物种数显著低于尚未被水淹过的植被,但一年生草本物种数没有显著差异。被水淹过的植被草本层生物量与尚未水淹的植被没有显著差异。可见,水淹显著改变了消涨带原有植被物种组分和物种多样性,但一年生草本物种数和草本层生物量没有显著差异。未来175 m以下的植被中,草本尤其是一年生草本将占据优势。在消涨带植被恢复选择适应水淹生境物种过程中,应分别从植物的生活史、生理学和形态学等角度进行筛选,尤其应重视生活史适应策略植物的应用。被水淹过的156 m以下现有优势草本和存活的灌木可以作为三峡库区未来消涨带植被恢复的备选物种。     

三江并流地区干旱河谷植物物种多样性海拔梯度格局比较

在滇西北三江并流地区典型干旱河谷段, 在怒江、澜沧江和金沙江的东、西坡共设置了6条海拔梯度样带, 通过标准样地的植物群落调查, 分析各条样带植物的物种丰富度、物种更替率的海拔梯度格局, 并比较了地理和植被变量对分布格局的解释。干旱河谷植被带位于海拔3,000 m以下, 以灌丛和灌草丛为主, 其在各河谷的分布上限自西向东依次升高。植物物种丰富度的分布主要与海拔、流域、经纬度和植被带有关, 沿纬度和海拔梯度升高而显著增加的格局主要表现在草本层和灌木层, 灌木物种丰富度还呈现自西向东显著增加的趋势。怒江的灌木和草本种物种丰富度显著高于金沙江和澜沧江, 三条江的乔木种丰富度差异则不显著。森林带的样方草本物种丰富度显著低于灌草丛带样方, 并且还拥有后者没有的乔木种。不同样带的植物物种更替速率呈现了不一致的海拔梯度格局, 但均在样带海拔下部的灌草丛群落与海拔上部森林群落之间的交错带出现峰值。森林-灌草丛植被交错带在怒江样带处于海拔1,900-2,100 m处, 在澜沧江河谷位于海拔2,300-2,400 m, 在金沙江河谷位于海拔2,700-2,900 m。所有海拔样带的森林段或灌草丛段相对于同一样带不同植被段之间的物种更替程度为最小, 不仅小于同一流域不同样带相同植被段之间物种更替率的均值, 更小于所有样带相同植被段之间的更替率均值。在三条河流6条海拔样带的12个植被带段之间的物种更替变化中, 空间隔离因素可以解释34.2%, 而植被类型差异仅能解释不到0.5%。本研究结果显示了环境差异对不同植被类型物种丰富度的首要影响, 和各河流之间的空间隔离对植物群落构建和物种构成的主要作用。     

Altitudinal effects on habitat selection of dung beetles (Scarabaeoidea: Aphodiidae) in the northern Iberian peninsula

The effects or vegetation cover on the abundance and species richness of dung beetles (Aphodiidae) were examined in three altitudinal zones: lowland (520–600 m), mid-altitude (950–963 m) and highland (1230–1275 m). Pitfall traps baited with fresh cattle dung were placed in three vegetation types at each altitudinal zone: forest, heathland and pasture. Species richness was lower in forests than in the other vegetation types. The total abundance of beetles also varied with vegetation type, but the effect was dependent on altitude. Number of individuals was higher in pasture at highlands and in heathland and forest at mid-altitude and lowlands. An altitudinal dependence of distribution of individuals between vegetation types was also found for the more abundant species in the study area. These results could be explained if the local distribution of individuals between vegetation types was determined by microcli-matic factors, mainly temperature. Differences in altitude between sites are associated with temperature changes, determining the habitat selection of species at each altitude.     

Species Richness,Spatial Variation,and Abundance of the Soil Seed Bank of a Secondary Tropical Rain Forest1

Despite the importance of the soil seed bank in tropical forest regeneration, little is known about spatial variability in species composition and abundance of seeds stored in the soil. To develop sampling methods for comparative studies, we examined species richness, spatial variation, and abundance of germinants from the soil seed bank in a 16 year old secondary, tropical wet forest at La Selva Biological Station, Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at the intersection points of a gridded 1 ha plot (10 × 10-m grid, 121 samples) and in a nested 100 m² subplot (2 × 2-m grid, 36 samples). The 1 ha plot had a density of 4535 seeds/m² with 34 species observed. Based on a series of 100 randomized species accumulation curves, a Michaelis-Menten fit predicted a mean species richness of 36.3 species; the number of observed species was close to the predicted asymptote. A nonparametric, first-order jackknife species richness estimator predicted a species richness of 37.0 species. Eighty-five and 95 percent of the observed species richness is contained, on average, within 41 and 74 pooled samples, respectively. Within the 100 m² nested subplot, a density of 5476 seeds/m² was observed, comprising 26 species with an estimated species richness (Michaelis-Menten fit) of 29.1 species. The jackknife species richness estimator predicted a species richness of 36.7 species. For species richness and abundance of both plots, spatial autocorrelation statistics (Moran's I) were not significantly different from zero at lag distances from 2 to 100 m, indicating a random distribution at these spatial scales. For this site, accurate estimates of species composition depend upon the number of samples collected as well as the spatial distribution of sampling effort. Many small samples distributed over a large area provide greater accuracy and precision for estimating species richness of the soil seed bank.     

Avifaunal gradients in two arid zones of central Iran in relation to vegetation, climate, and topography

Aim To identify the ecological factors (related to vegetation, altitude, climate, or geomorphology) that could explain the main gradients of avifaunal richness and composition in arid environments of Central Iran. Location The study was carried out in two nearby semi‐arid protected areas of the Ispahan province: the Kolah‐Ghazi National Park (c. 50,000 ha; 1540–2535 m a.s.l.) and the Mouteh Wildlife Refuge (c. 220,000 ha; 1493–2900 m a.s.l.). Annual average precipitation and temperature range from 155–205 mm and 15–19.5 °C, respectively. Vegetation cover is sparse. Methods The two study areas were sampled with a 1 × 1 km grid design. A subset of 405 squares was randomly chosen and each was visited once during spring or summer by a team of five observers walking from one side of a square to the other and back, recording the birds encountered. Raptors and species considered to be accidental or migrating were not taken into account. We first looked for avifaunal, vegetation, and geomorphological gradients using Correspondence Analysis. As we found spatial autocorrelation within our response variables (avifaunal richness, abundance and/or composition), we first calculated an autocorrelation term, then added this autocorrelation term in anova , ancova (separate slope design) and stepwise regression to assess the relative role of spatial autocorrelation and environmental explanatory variables (vegetation, altitude, climate, or topography). We also partitioned the variance of the avifaunal matrix between several sets of co‐variables, after controlling for spatial effects, using a series of partial Canonical Correspondence Analyses. Results A main gradient, common to the two areas, distinguishes bird species characteristic of flat sedimentary areas and species dwelling in mountainous and/or rocky areas. Despite the generally low values of the correlations measured, we found that richness, abundance and composition of the avifauna were better correlated with topography, especially the altitudinal amplitude within each square, than any other variable, including vegetation. Altitudinal amplitude is related to substrate complexity. Main conclusions In arid zones of central Iran, topographic features seem to be the main factors structuring avifaunal composition and abundance. Avifaunal composition and richness are mainly correlated with the complexity of the substrate, but both avifaunal richness and abundance increase with altitude, probably in response to decreasing aridity. We did not observe any bird altitudinal zonation in a strict sense. These results contrast with those generally observed in mid‐latitude regions of the Palaearctic.     

Long-Term Effects of Forest Regrowth and Selective Logging on the Seed Bank of Tropical Forests in NE Costa Rica1.

To investigate long-term effects of land use on the soil seed bank, we compared the abundance/density, species richness, life form distribution, and species composition of seeds stored in the soil of four 15–20 yr-old second-growth stands, two old-growth stands, and two previously selectively-logged stands in the Caribbean lowlands of Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at 10 m intervals along three 120–160 m long transects in each stand (44–48 soil cores, 22–24 combined seed bank samples per site). Seed density was highest but variable in second-growth stands (8331–14535 seeds/m²), low and homogeneous in old-growth stands (2258–2659 seeds/m²), and intermediate and highly variable in selectively-logged stands (1165–6854 seeds/m²), which also had contrasting logging intensities. Species richness was strongly dependent on seed density, but showed less variation. Life form distribution did not differ statistically among or within land-use categories. In each stand, herbs-forbs, shrubs, and vines dominated the seed bank (> 75% of the species richness and abundance), whereas trees were a minor component (< 20% of the species richness and < 5% of the abundance) and were predominandy early successional. Shrubs and vines were most abundant in second-growth stands where regrowth vegetation was repeatedly cut before abandonment, whereas grasses and sedges were most abundant in the only forest stand that was completely surrounded by pastures. In terms of species composition, old-growth stands were more similar to selectively-logged stands than to second-growth stands, but across stands, selectively-logged forests were most distinct from the other two forest types. An inventory of the standing woody vegetation in each site showed little representation of the woody taxa found in the seed bank. We discuss these results in the context of the main factors that have been postulated to influence the abundance, life form, and species composition of tropical forest seed banks, and explore the role of the latter during intermediate phases of tropical forest succession and regeneration.     

Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China： （I） Seed Rain

Seed dynamics is an important part of stand dynamics in forest ecosystems. In this paper, 26 gaps were randomly selected to study the influence of gaps on the spatial and temporal patterns of seed rains in a tropical montane rainforest of Hainan Island, South China. Three zones for each gap, including outside gap zone （Non-gap）, transitional gap zone （EG-CG）, and central gap zone （CG）, were designed, and fourseed traps （each lm x lm in size） were placed in each zone. Seed rains were collected by these traps every 10 days from June 2001 to May 2002. Seed rain varied greatly with season and generally exhibited a pattern of unimodal change during the study period： seed abundance and species richness were both greater in the wet season than in the dry season. Gaps significantly influenced the temporal patterns of both species richness and density of seed rains. Gaps had no significant influences on the spatial distribution patterns of seed rain species richness, but significantly affected the spatial distribution pattern of seed rain densities. Among the three different zones of gaps, the outside gap zone generally received more seeds inputs than the two other gap zones.     

Distribution and Flowering Ecology of Bromeliads along Two Climatically Contrasting Elevational Transects in the Bolivian Andes1

We compared the diversity, taxonomic composition, and pollination syndromes of bromeliad assemblages and the diversity and abundance of hummingbirds along two climatically contrasting elevational gradients in Bolivia. Elevational patterns of bromeliad species richness differed noticeably between transects. Along the continuously wet Carrasco transect, species richness peaked at mid‐elevations, whereas at Masicurí most species were found in the hot, semiarid lowlands. Bromeliad assemblages were dominated by large epiphytic tank bromeliads at Carrasco and by small epiphytic, atmospheric tillandsias at Masicurí. In contrast to the epiphytic taxa, terrestrial bromeliads showed similar distributions across both transects. At Carrasco, hummingbird‐pollination was the most common pollination mode, whereas at Masicurí most species were entomophilous. The proportion of ornithophilous species increased with elevation on both transects, whereas entomophily showed the opposite pattern. At Carrasco, the percentage of ornithophilous bromeliad species was significantly correlated with hummingbird abundance but not with hummingbird species richness. Bat‐pollination was linked to humid, tropical conditions in accordance with the high species richness of bats in tropical lowlands. At Carrasco, mixed hummingbird/bat‐pollination was found especially at mid‐elevations, i.e., on the transition between preferential bat‐pollination in the lowlands and preferential hummingbird‐pollination in the highlands. In conclusion, both richness patterns and pollination syndromes of bromeliad assemblages varied in distinct and readily interpretable ways in relation to environmental humidity and temperature, and bromeliad pollination syndromes appear to follow the elevational gradients exhibited by their pollinators.     

Vegetation on the edge: a gradient analysis of the riparian zone, Poerua River, New Zealand

Forest vegetation patterns alongside the Poerua River, south Westland, were studied to determine whether a distinct riparian community could be defined either immediately adjacent to the river, or out to the limit of overbank flooding. Ten randomly located 100 m transects were established perpendicular to the river at each of two sites. Ground cover of alluvial sediment indicated that annual overbank flooding occurred up to 20 m into the forest (the flood zone). No significant difference in vascular plant species richness was found between the flood zone and non-flood zone at either site, however a significant difference in species richness was found between sites, and this was attributed to recent disturbance at the edge of one site. Detrended correspondence analysis separated plots by site and indicated a gradient of species change from the river’s edge to the ends of the transects. There were inconsistent differences in the densities and/or basal areas of trees and shrubs between sites and zones. No distinct band of vegetation was recognizable as a riparian zone alongside the Poerua River. Instead, there was evidence that edge processes had influenced vegetation patterns on a gradient away from the river, fluvial processes had eroded into, and influenced the vegetated edge, and historical disturbance events had had strong effects on vascular plant community composition. The riparian zone incorporates the whole floodplain and environmental management needs to take this into consideration.     

Species richness and phylogenetic diversity of seed plants across vegetation zones of Mount Kenya,East Africa

Mount Kenya is of ecological importance in tropical east Africa due to the dramatic gradient in vegetation types that can be observed from low to high elevation zones. However, species richness and phylogenetic diversity of this mountain have not been well studied. Here, we surveyed distribution patterns for a total of 1,335 seed plants of this mountain and calculated species richness and phylogenetic diversity across seven vegetation zones. We also measured phylogenetic structure using the net relatedness index (NRI) and the nearest species index (NTI). Our results show that lower montane wet forest has the highest level of species richness, density, and phylogenetic diversity of woody plants, while lower montane dry forest has the highest level of species richness, density, and phylogenetic diversity in herbaceous plants. In total plants, NRI and NTI of four forest zones were smaller than three alpine zones. In woody plants, lower montane wet forest and upper montane forest have overdispersed phylogenetic structures. In herbaceous plants, NRI of Afro‐alpine zone and nival zone are smaller than those of bamboo zone, upper montane forest, and heath zone. We suggest that compared to open dry forest, humid forest has fewer herbaceous plants because of the closed canopy of woody plants. Woody plants may have climate‐dominated niches, whereas herbaceous plants may have edaphic and microhabitat‐dominated niches. We also proposed lower and upper montane forests with high species richness or overdispersed phylogenetic structures as the priority areas in conservation of Mount Kenya and other high mountains in the Eastern Afro‐montane biodiversity hotspot regions.     

Impact of Flooding on the Species Richness, Density and Composition of Amazonian Litter-Nesting Ants

Litter-nesting ants are diverse and abundant in tropical forests, but the factors structuring their communities are poorly known. Here we present results of the first study to examine the impact of natural variation in flooding on a highly diverse (21 genera, 77 species) litter-nesting ant community in a primary Amazonian forest. Fifty-six 3 × 3 m plots experiencing strong variation in flooding and twenty-eight 3 × 3 m terra firme plots were exhaustively searched for litter-nesting ants to determine patterns of density, species richness and species composition. In each plot, flooding, litter depth, twig availability, canopy cover, plant density, percent soil nitrogen, carbon, and phosphorus were measured. Degree of flooding, measured as flood frequency and flood interval, had the strongest impact on ant density in flooded forest. Flooding caused a linear decrease in ant abundance, potentially due to a reduction of suitable nesting sites. However, its influence on species richness varied: low-disturbance habitat had species richness equal to terra firme forest after adjusting for differences in density. The composition of ant genera and species varied among flood categories; some groups known to contain specialist predators were particularly intolerant to flooding. Hypoponera STD10 appeared to be well-adapted to highly flooded habitat. Although flooding did not appear to increase species richness or abundance at the habitat scale, low-flooding habitat contained a mixture of species found in the significantly distinct ant communities of terra firme and highly flooded habitat.
     

兴隆山自然保护区种子植物的垂直分布格局研究

该研究通过对甘肃省兴隆山自然保护区进行野外实地调查和相关文献资料收集,依据海拔梯度将保护区划分为6个植被垂直带[草原带(1800~2000 m)、山地灌丛带(2000~2200 m)、亚高山针叶林带(2200~2900 m)、亚高山矮林带(2900~3000 m)、高山灌丛带(3000~3500 m)、高山草甸带(>3500 m)],在整理6个植被垂直带植物名录的基础上,以种子植物为研究对象,对各植被垂直带的种子植物丰富度、生活型、区系成分和系统发育结构进行分析,探讨植物多样性沿植被垂直带海拔升高的垂直变化规律,以揭示植物对环境的生态适应性,为山地植物多样性保护与开发利用提供理论依据。结果表明:(1)按最新的分类系统划分,兴隆山自然保护区种子植物隶属于87科387属889种,植物科、属、种丰富度随植被垂直带海拔升高呈单峰分布格局,在亚高山针叶林带达到峰值(81科304属661种);各植被垂直带间的Jaccard相似性系数呈中等不相似和极不相似水平,海拔越靠近的植被垂直带间相似性系数越高。(2)保护区内种子植物不同生活型的垂直变化格局存在差异,木本植物所占比例沿植被垂直带海拔升高呈先升后降的变化趋势,而草本植物呈相反的变化格局,且各植被垂直带中草本植物所占比例始终高于木本植物。(3)保护区植物在属水平上,热带成分所占比例随植被带海拔升高呈下降的变化趋势,而温带成分占比呈上升的变化趋势。(4)系统发育结构在中低海拔区域的亚高山针叶林带呈发散型,在高海拔区域(>2900 m)的3个植被带中呈聚集型,说明兴隆山自然保护区非随机分布格局在群落构建机制中发挥主要作用。     

Dung beetle communities as biological indicators of riparian forest widths in southern Brazil

Riparian forests provide important habitat for many wildlife species and are sensitive to landscape change. Among terrestrial invertebrates, dung beetles have been used to investigate the effects of environmental disturbances on forest structure and diversity. Since many studies demonstrated a negative response of dung beetle communities to increasing forest fragmentation, and that most dung beetle species had a more pronounced occurrence during warmest seasons, three hypotheses were tested: (1) Scarabaeinae richness, abundance, diversity and evenness are lower in thinner riparian zone widths than in wider widths during the warmest seasons; (2) Scarabaeinae richness and abundance are positively influenced by leaf litter coverage and height and canopy cover; and (3) Scarabaeinae composition varies with the reduction in riparian vegetation and among annual seasons. We selected four fragments with different riparian zone widths in three secondary streams in southern Brazil. In each fragment, four sampling periods were carried out seasonally between spring 2010 and winter 2011. We collected dung beetles using pitfall traps with two types of bait. We collected 1289 specimens distributed among 29 species. In spring and summer, dung beetle richness was higher in fragments with the widest riparian zone than in those with a thinner riparian zone, and it did not vary between fragments in fall and winter seasons. Dung beetle abundance did not differ among fragments with different riparian zone widths, but it was higher in spring and summer than fall and winter. Richness and abundance were positively influenced by leaf litter. While dung beetle diversity was higher in fragments with wider riparian zone widths than in those with thinner widths, the evenness was similar among fragments. Dung beetle composition differed between the fragments with the widest and thinnest riparian zones, and it also varied among the seasons. Our results suggest that decreased riparian zones affect negatively to dung beetle community structure in southern Brazil. Fragments with thinner riparian zones had lower beetle richness in warmest seasons and an altered community composition. In this sense, the dung beetles are potentially good indicators of riparian forest fragmentation since some species were indicators of a particular riparian zone width. From a conservation perspective, our results demonstrate that the new Brazilian Forest Code will greatly jeopardize not only the terrestrial and aquatic biodiversity of these ecosystems, but also countless other ecological functions.     

Distribution of alien vs. native plant species in roadside communities along an altitudinal gradient in Tenerife and Gran Canaria (Canary Islands)

Roadside plant communities were studied along two roads following an altitudinal gradient in Gran Canaria and Tenerife (Canary Islands). Our aim was to investigate variation in plant species richness, particularly of the alien flora, along a gradient from coastal shrubland to summit vegetation (1950 m a.s.l. in Gran Canaria, 2300 m in Tenerife) in relation to variation in habitat factors (altitude, habitat structure, roadside disturbance, distance to urban nuclei). We compared different species groups that were classified in terms of their biogeographical status, origin and life form. Altitude was the most important factor determining species richness and composition along both roadside transects. Alien plants showed a unimodal distribution pattern along the altitudinal gradient, with less species and lower abundance at low and high altitudes, and highest abundance at intermediate altitude. Alien plant species were also relatively more frequent near urban centres. The number of native and alien species was significantly positively correlated along the altitudinal gradient. Both alien and native, non-endemic species showed differences in their distribution along the altitudinal gradient according to their biogeographical affinities and climatic tolerances. Despite considerable differences in species pools these patterns were consistent among the two islands. Environmental (abiotic) stress is proposed as a primary, altitude-related factor acting as a filter against most alien plants at coastal and high-mountain altitudes. A higher frequency or intensity of disturbance at intermediate altitudes may be a further causal factor promoting alien plants in this zone. Future management efforts to control alien plants along roads should, therefore, concentrate on intermediate altitudinal zones of the higher Canary Islands.     

Nonlinear Distribution Pattern of Hibernating Bats in Caves along an Elevational Gradient in Mountain (Carpathians,Southern Poland)

Background

Thermal gradients along changes in elevation in mountainous environments are reflected by different biotas. Although there have been studies of elevation variation in bat assemblages in summer, winter changes in the same gradients remain unknown.

Methodology/Principal Findings

The objective of this study was to document changes in the species composition of bats hibernating in caves along a temperate elevational gradient. We studied 70 caves between from 300 m to 1,930 m altitude along a slope of the Carpathian Mountains in southern Poland. We recorded changes in bats, including species richness, abundance, altitudinal distribution and dominance during consecutive winters between 2003 and 2009. Similarity of dominance of faunal structure was assessed by using the Bray-Curtis similarity index. We used the generalised additive model and rarefaction to study the variation in species richness, and generalized additive mixed models to examine the effect of abiotic factors on the qualitative and quantitative structure of bat assemblages. During 351 surveys we recorded 13,856 hibernating bats from 15 species. Species richness peaked around mid-elevation (1,100–1,400 m a.s.l.) with richness declining at both higher and lower elevations. Based on the results of a cluster analysis, we could distinguish among four altitudinal zones that differed in species richness and dominance structure.

Conclusions/Significance

This is the first study documenting changes in species richness and variation of structure of bats hibernating in caves along an elevational gradient. The most surprising and key finding is the fact that changes in the structure of assemblages of hibernating bats along the altitudinal gradient occurred in jumps, forming zones similar to those observed in the vegetation zones. Moreover, species richness and dominance structure of assemblages of hibernating bats in the mountains depended not only on location above sea level, but also on local geomorphologic conditions which strongly affected the microclimate of the caves.