Is tree diversity different in the Southern Hemisphere?

Questions: Is tree diversity higher in the southern hemisphere? Are latitudinal asymmetries in diversity sensitive to sampling effects? Location: 198 forested locales worldwide. Methods: I re‐analysed the Gentry database, which I augmented with an additional survey from New Zealand. Data were used to test whether latitudinal declines in tree diversity differ between the northern and southern hemispheres. Data were also used to test whether hemispheric asymmetries in diversity are sensitive to sampling effects, or geographic variation in tree densities. Results: Area‐based measurements of species diversity are higher in the southern hemisphere. However, southern forests house denser plant populations. After controlling for geographic variation in tree densities, diversity patterns reverse, indicating tree diversity is higher in the northern hemisphere. Conclusions: Latitudinal changes in tree diversity differ between hemispheres. However, the nature of hemispherical asymmetries in species diversity hinges on how diversity is defined, illustrating how different definitions of diversity can yield strikingly different solutions to common ecological problems.     

陆地植物群落物种多样性的梯度变化特征

研究陆地植物落物种多样性随环境因子及群落演替梯度的变化特征是揭示生物多样性与生态因子相互关系的重要方面,根据近期国内外的文献,综述了这方面的研究进展。随纬度的降低,通常物咱多样性随中,随不分梯度的变化,物种多样性的变化有６种趋势;随海拔高的变化,物处多样性有５种模式;随土壤养分梯度的变化,表现出不同的规律;演替过程中物种多样生的变化趋势相似。关于植物群落物种多样性梯度格局的机制有多种假说,但仍需进     

Biodiversity patterns diverge along geographic temperature gradients

Models applying space-for-time substitution, including those projecting ecological responses to climate change, generally assume an elevational and latitudinal equivalence that is rarely tested. However, a mismatch may lead to different capacities for providing climatic refuge to dispersing species. We compiled community data on zooplankton, ectothermic animals that form the consumer basis of most aquatic food webs, from over 1200 mountain lakes and ponds across western North America to assess biodiversity along geographic temperature gradients spanning nearly 3750 m elevation and 30° latitude. Species richness, phylogenetic relationships, and functional diversity all showed contrasting responses across gradients, with richness metrics plateauing at low elevations but exhibiting intermediate latitudinal maxima. The nonmonotonic/hump-shaped diversity trends with latitude emerged from geographic interactions, including weaker latitudinal relationships at higher elevations (i.e. in alpine lakes) linked to different underlying drivers. Here, divergent patterns of phylogenetic and functional trait dispersion indicate shifting roles of environmental filters and limiting similarity in the assembly of communities with increasing elevation and latitude. We further tested whether gradients showed common responses to warmer temperatures and found that mean annual (but not seasonal) temperatures predicted elevational richness patterns but failed to capture consistent trends with latitude, meaning that predictions of how climate change will influence diversity also differ between gradients. Contrasting responses to elevation- and latitude-driven warming suggest different limits on climatic refugia and likely greater barriers to northward range expansion.     

秦岭牛背梁植物物种多样性垂直分布格局

基于秦岭山脉中段牛背梁自然保护区南北坡垂直样带51个样方的调查资料,利用植被数量分析方法(TWINSPAN和DCA)对牛背梁植物群落进行了分类和排序,并分析了植物物种多样性沿海拔梯度的分布格局。结果表明,牛背梁的植被群落具有明显的海拔梯度格局,从低海拔到高海拔依次分布有：锐齿槲栎(Quercus aliena var.acuteserrata)林,桦木(Betula spp.)林．巴山冷杉(Abis Jargesii)林和亚高山灌丛。海拔梯度是牛背梁山区制约植物群落分布的主要因子,而坡向和坡度则起到次要作用。对物种多样性的分析表明,物种总数、木本植物物种多样性和草本植物物种多样性在南北坡具有不同的海拔梯度格局。物种总数在南坡呈现单峰分布格局,而在北坡分布趋势不明显;木本植物物种多样性在南北坡具有相似的分布格局：在低海拔沿海拔梯度变化不明显,而在高海拔则随海拔上升而急剧下降;草本植物物种多样性在南北坡沿海拔梯度变化的规律不明显。β多样性沿海拔梯度先减少后增加,形成两端高中间低的格局,说明中海拔地区生境条件较为均一,低海拔地区的人为活动增加了生境的异质性,而高海拔地区的生态过渡特性增加了物种的更替速率以及群落的相异性。     

Tree community structure and stem mortality along a water availability gradient in a Mexican tropical dry forest

We document spatial changes in species diversity, composition, community structure, and mortality of trees across a gradient of water availability in a tropical dry forest in western Mexico. This gradient occurs along the main stream of a small watershed of less than 1 km in length. Four 30 × 80 m plots were established systematically to include the driest (ridge top of the watershed) to the wettest sites (watershed bottom) within this watershed. All stems larger than 5 cm were identified, and measured for diameter and height. Dead stems larger than 5 cm were measured and classified as: a) found on live or dead trees, and b) standing (“snags”) or lying (“downlogs”) on the ground. The number of recorded species per plot declined from 73 to 44 species as water availability decreased. A decline in estimated total richness, and in Shannon-Wiener and Simpson diversity indices was also observed in the drier plots. Species composition strongly changed along the gradient, with the two ends of the gradient sharing only 11% of the species. Stem density and percentage of dead stems and trees increased in abundance and basal area from the wetter to the drier sites. Tree and stem size (basal area, height and stem diameter) showed the opposite trend. Nonetheless, total basal area of live trees was largest at the two end gradient locations and oscillated between 12.22 m² ha⁻¹ and 7.93 m² ha⁻¹. Proportion of snags increased towards the driest site (from 46 to 72%), while that of down logs decreased. Overall, our results suggest that small-scale gradients of water availability play a paramount role in the spatial organization of tree communities in seasonal tropical environments. This revised version was published online in June 2006 with corrections to the Cover Date.     

Latitudinal Variation in Termite Species Richness and Abundance along the Brazilian Atlantic Forest Hotspot

In this study, we investigated the termites of the Brazilian Atlantic Forest, one of the most threatened biodiversity hotspots in the world, in regularly spaced sites from 7° S to 27° S latitude. To our knowledge, this is the only report of a latitudinal survey of termites at species level performed with a standardized sampling protocol. We evaluate termite diversity and abundance, and describe patterns of species composition based on feeding groups along the latitudinal gradient. We also describe the relative contribution of environmental variables to explain diversity patterns. Termite assemblages were investigated by standardized surveys at 15 Atlantic Forest sites, on six transects divided into five sections of 10 m², with 30 sections per site (or 300 m²/site), which were investigated by one trained person for one hour. Observed species richness and abundance were negatively correlated with latitude. The influence of latitude was explained mainly by variables related to temperature, precipitation and ambient energy (potential evapotranspiration). Our results also suggest that temperature exerts a greater constraint on Atlantic Forest termites than productivity, because ambient productivity increases with latitude in this forest but termite diversity decreases. Termite species richness in the Atlantic Forest showed a different pattern than those described for other organisms, increasing in diversity where the coastal‐forest strip narrows. Overall, our results indicate comparatively high termite species richness at northeastern sites and a significant impoverishment of termite assemblages in the southeastern and southern regions of the Atlantic Forest.     

Diversity dynamics of Miocene mammals in relation to the history of tectonism and climate

Continental biodiversity gradients result not only from ecological processes, but also from evolutionary and geohistorical processes involving biotic turnover in landscape and climatic history over millions of years. Here, we investigate the evolutionary and historical contributions to the gradient of increasing species richness with topographic complexity. We analysed a dataset of 418 fossil rodent species from western North America spanning 25 to 5 Ma. We compared diversification histories between tectonically active (Intermontane West) and quiescent (Great Plains) regions. Although diversification histories differed between the two regions, species richness, origination rate and extinction rate per million years were not systematically different over the 20 Myr interval. In the tectonically active region, the greatest increase in originations coincided with a Middle Miocene episode of intensified tectonic activity and global warming. During subsequent global cooling, species richness declined in the montane region and increased on the Great Plains. These results suggest that interactions between tectonic activity and climate change stimulate diversification in mammals. The elevational diversity gradient characteristic of modern mammalian faunas was not a persistent feature over geologic time. Rather, the Miocene rodent record suggests that the elevational diversity gradient is a transient feature arising during particular episodes of Earth''s history.     

城市化对蝴蝶多样性的影响:以重庆市为例

2005年5–10月,自重庆市沙坪坝区到北碚区沿城市生境梯度选取了5个断面(沙坪公园、南溪口、回头坡、鸡公山和缙云山),进行蝴蝶取样调查。共采获蝴蝶4,802只,隶属11科41属65种。统计分析表明,东方菜粉蝶(Pieriscanidia)、菜粉蝶(P.rapae)和酢浆灰蝶(Pseudozizeeriamaha)等3种为优势种,青凤蝶(Graphiumsarpedon)、宽边黄粉蝶(Euremahecabe)、连纹黛眼蝶(Lethesyrcis)、黄钩蛱蝶(Polygoniac-aureum)、点玄灰蝶(Tongeiafilicaudis)和直纹稻弄蝶(Parnaraguttata)等9种为常见种。多样性指数变化趋势为缙云山>回头坡>鸡公山>南溪口>沙坪公园。沿城市生境梯度,从人为干扰较大的沙坪公园(城市化水平较高的代表)到人为干扰较小的缙云山(城市化水平较低的代表),蝴蝶多样性指数基本呈递增趋势,且植被种类丰富度越高、覆盖率越高、日照量越高的生境,蝴蝶种类和数量越多,蝴蝶多样性指数也越高。蝴蝶的多样性特征可以作为城市生境质量和环境变化的指标。     

Rodent species diversity in relation to altitudinal gradient in Northern Serengeti,Tanzania

Rodents are among the successful small mammals in the world. In species richness, rodents outnumber other mammalian orders owing partly to their capability to exploit many different habitats. Their diversities have been influenced by many factors including the altitude. This study assessed rodent diversity across the two altitudinal zones, that is, lowland western zone and highland eastern zone, in the Serengeti ecosystem, Tanzania. Capture‐Mark‐Recapture studies were undertaken in November 2009 and April 2010 using live traps in the ecosystem to compare variations in species diversity of rodents in the two zones of the ecosystem. Eight (8) rodent species were recorded in each zone area. However, species richness was higher in crop land and woodland areas than in grasslands in each zone. The two zones comprised of different species diversities for which Rényi Diversity profiles indicated the higher diversity in the eastern zone than the western zone although the difference was not significant (P > 0.05). Differences between the eastern and western zones could be attributed to the altitudinal gradient whereby the east was at a higher elevation than the west. Maintenance and management of wildlife corridors will assist migration of rodents between the two zones and enhance continuous gene flow.     

道路边坡坡度对植被恢复中物种多样性的影响研究

以成都平原周边的5条道路的边坡植被群落作为研究对象,采用样线法,研究坡度对道路边坡的植物群落多样性的影响。选取101个海拔在300~400 m间并且土壤质地相同的边坡样方进行坡度分析。结果显示：（1）选取的样方中,共出现142种植物,属于61个科,121属。（2）边坡坡度对阳坡和阴坡的灌木层与草本层的植物群落物种多样性具有显著的影响(P<0.05)。（3）边坡坡度对阴坡群落的均匀度指数影响显著(P<0.05);而对阳坡群落的丰富度影响相对较大,呈现先增加后降低的趋势。分析表明,边坡坡度对成都平原周边地区道路边坡的植物群落多样性具有显著影响;在坡度<35°的条件下,植被群落恢复效果较好,群落的多样性高;而对>35°的边坡来说,多样性指数呈下降趋势,不利于后期边坡恢复。     

贡嘎山东坡植物区系的垂直分布格局

为了探讨贡嘎山植物区系的垂直分化特征及其与周边地区植物区系的联系,结合样带法与样方法,对贡嘎山东坡垂直植被带进行了调查,统计得出各垂直植被带的科、属的物种数量,分析了科、属、种级区系成分的构成及其沿海拔梯度的分布格局,并对各垂直植被带区系的相似性进行了聚类分析。结果表明：1)贡嘎山植物区系在整体上具有温带性质,但在干旱河谷地带,热带和温带区系成分的比例相当：热带成分的构成和分布反映古热带和古地中海区系的残遗性影响;2)东亚(含亚型)和东亚-北美成分对贡嘎山中部森林植物区系的影响最大,这些成分以温带古老性质为主;3)北温带成分是贡嘎山植物区系的主体之一,对青藏高原隆升以来贡嘎山植物区系进化类群和特有成分的发展有主要贡献,代表区系的年轻组分;4)中国特有种类型多样,占不同垂直植被带物种数量的40％-65％,其比例随海拔上升而增大。各类型比例的垂直变化突出反映了贡嘎山及横断山脉中海拔地段的植物区系与华中地区的联系,以及高海拔地段与青藏高原及东喜马拉雅的区系之间的联系。本文还就贡嘎山在生物地理分布上的意义以及贡嘎山和横断山脉植物区系特有性的性质进行了讨论。     

The latitudinal gradient of species diversity among North American grasshoppers (Acrididae) within a single habitat: a test of the spatial heterogeneity hypothesis

Abstract. The spatial heterogeneity hypothesis predicts a positive relationship between habitat complexity and species diversity: the greater the heterogeneity of a habitat, the greater the number of species in that habitat. On a regional scale, this hypothesis has been proposed to explain the increases in species diversity from the poles to the tropics: the tropics are more diverse because they contain more habitats. On the local scale, the spatial heterogeneity hypothesis suggests that the tropics are more diverse because they contain more microhabitats. The positive relationship between habitat heterogeneity and species diversity, on the local scale, is well documented. In this paper, we test whether habitat heterogeneity on the local scale can explain the latitudinal gradient of species diversity on the regional scale. We determined the latitudinal gradient of species diversity of 305 species of North American grasshoppers using published distribution maps. We compared the slope of this multihabitat (regional-scale) gradient with the slope of a within-habitat (local-scale) gradient in the prairie grasslands. Our results show no significant difference between the slopes at the two scales. We tested the generality of our results by comparing multi- and within-habitat latitudinal gradients of species diversity for ants, scorpions and mammals using data from the literature. These results are in accordance with those from grasshoppers. We can therefore reject the local-scale spatial heterogeneity hypothesis as a mechanism explaining the regional-scale latitudinal gradient of species diversity. We discuss alternative mechanisms that produce this gradient.     

Open science and meta‐analysis allow for rapid advances in ecology: A response to Menegotto et al. (2019)

Menegotto and colleagues’ (2019) commentary on our paper (Kinlock et al., 2018) does not negate our findings, but by recategorizing and reanalysing a portion of our data set, advances our knowledge of the latitudinal diversity gradients (LDGs) in marine ecosystems, particularly emphasizing different findings for benthic LDGs as a result of the recategorization of the data. Furthermore, we see the contribution by Menegotto et al. (2019) as highlighting the importance of scientific transparency; we believe that this insight into the nature of LDGs in marine systems would have been delayed, if not unobtainable, had we not provided fully transparent methods and complete data in our paper.     

Methanotrophic diversity in an agricultural soil as evaluated by denaturing gradient gel electrophoresis profiles of pmoA, mxaF and 16S rDNA sequences

Molecular methods were used to characterize the diversity of a methanotrophic population in an agricultural soil. For this purpose we have used DGGE analysis of functional and phylogenetic markers. Functional markers utilised comprised the pmoA-gene coding for the -subunit of the particulate methane monooxygenase (pMMO) present in all known methanotrophs and the mxaF-gene coding for the -subunit of methanol dehydrogenase (MDH) present in all Gram-negative methylotrophs. In addition, we have used 16S rDNA as a phylogenetic marker. DGGE patterns of an enrichment culture, and sequencing of major DGGE bands obtained with the bacterial specific primers showed that the community structure was dominated by methanotrophic populations related to Methylobacter sp. and Methylomicrobium sp. The PCR products amplified with the functional primer sets were related to both type I and type II methanotrophs. We also designed a new pmoA-targeting primer set which could be used in a nested protocol to amplify PCR-products from DNA extracted directly from the soil.     

Influence of phylogenetic scale on the relationships of taxonomic and phylogenetic turnovers with environment for angiosperms in China

We aim to assess the influence of phylogenetic scale on the relationships of taxonomic and phylogenetic turnovers with environment for angiosperms in China. Specifically, we quantify the effects of contemporary climate on β‐diversity at different phylogenetic scales representing different evolutionary depths of angiosperms. We sampled a latitudinal gradient and a longitudinal gradient of angiosperm assemblages across China (each ≥3400 km). Species composition in each assemblage was documented. Three metrics of β‐diversity (β_sim.tax measuring taxonomic β‐diversity; β_sim.phy and D_pw measuring tip‐ and basal‐weighted phylogenetic β‐diversity, respectively) were quantified among assemblages at sequential depths in the evolutionary history of angiosperms from the tips to deeper branches. This was done by slicing the angiosperm phylogenetic tree at six evolutionary depths (0, 15, 30, 45, 60, and 75 million years ago). β‐diversity at each evolutionary depth was related to geographic and climatic distances between assemblages. In general, the relationship between β‐diversity and climatic distance decreased from shallow to deep evolutionary time slice for all the three metrics. The slopes of the decreasing trends for β_sim.tax and β_sim.phy were much steeper for the latitudinal gradient than for the longitudinal gradient. The decreasing trend of the strength of the relationship was monotonic in all cases except for D_pw across the longitudinal gradient. Geographic distance between assemblages explained little variation in β‐diversity that was not explained by climatic distance. Our study shows that the strength of the relationship between β‐diversity and climatic distance decreases conspicuously from shallow to deep evolutionary depth for the latitudinal gradient, but this decreasing trend is less steep for the longitudinal gradient than for the latitudinal gradient, which likely reflects the influence of historical processes (e.g., the collision of the Indian plate with the Eurasian plate) on β‐diversity.