Large-scale phytogeographical patterns in East Asia in relation to latitudinal and climatic gradients

Aim This paper aims at determining how different floristic elements (e.g. cosmopolitan, tropical, and temperate) change with latitude and major climate factors, and how latitude affects the floristic relationships between East Asia and the other parts of the world. Location East Asia from the Arctic to tropical regions, an area crossing over 50° of latitudes and covering the eastern part of China, Korea, Japan and the eastern part of Russia. Methods East Asia is divided into forty‐five geographical regions. Based on the similarity of their world‐wide distributional patterns, a total of 2808 indigenous genera of seed plants found in East Asia were grouped into fourteen geographical elements, belonging to three major categories (cosmopolitan, tropical and temperate). The 50°‐long latitudinal gradient of East Asia was divided into five latitudinal zones, each of c. 10°. Phytogeographical relationships of East Asia to latitude and climatic variables were examined based on the forty‐five regional floras. Results Among all geographical and climatic variables considered, latitude showed the strongest relationship to phytogeographical composition. Tropical genera (with pantropical, amphi‐Pacific tropical, palaeotropical, tropical Asia–tropical Australia, tropical Asia–tropical Africa and tropical Asia geographical elements combined) accounted for c. 80% of the total genera at latitude 20°N and for c. 0% at latitude 55–60°N. In contrast, temperate genera (including holarctic, eastern Asia–North America, temperate Eurasia, temperate Asia, Mediterranean, western Asia to central Asia, central Asia and eastern Asia geographical elements) accounted for 15.5% in the southernmost latitude and for 80% at 55–60°N, from where northward the percentage tended to level off. The proportion of cosmopolitan genera increased gradually with latitude from 5% at the southernmost latitude to 21% at 55–60°N, where it levelled off northward. In general, the genera present in a more northerly flora are a subset of the genera present in a more southerly flora. Main conclusions The large‐scale patterns of phytogeography in East Asia are strongly related to latitude, which covaries with several climatic variables such as temperature. Evolutionary processes such as the adaptation of plants to cold climates and current and past land connections are likely responsible for the observed latitudinal patterns.     

武陵山地区种子植物区系中的中国特有属研究

武陵山地区含有中国种子植物特有属72个,占该区种子植物总属数的7．16％,占全国同类属数的28．69％,占华中同类属数的77．42％。其基本特征为：(1)古老与孑遗的木本植物众多,并存在一定相对年轻的成分;(2)地理成分多样,具明显的亚热带性质,表现出四方汇集和东、西、南、北的过渡性质;(3)水平分布上呈现南、北两个分布中心,垂直分布上以1000m以下的中、低海拔为主;(4)武陵山地区植物区系与神农架、秦岭、湘黔桂交界地区的关系比较密切,而与南岭、武夷山、滇黔桂地区的关系比较疏远。根据武陵山地区中国种子植物特有属的数量、与鄂西～川东特有现象中心(或者三峡中心)所含属的一致性以及地理间的密切联系,可以认为该区是鄂西～川东中心(或者三峡中心)的重要组成部分甚至是核心地带,在华中植物区系中发挥着举足轻重的作用。     

Phytogeographical analysis of seed plant genera in China

BACKGROUND AND AIMS: A central goal of biogeography and ecology is to uncover and understand distributional patterns of organisms. China has long been a focus of attention because of its rich biota, especially with respect to plants. Using 290 floras from across China, this paper quantitatively characterizes the composition of floristic elements at multiple scales (i.e. national, provincial and local), and explores the extent to which climatic and geographical factors associated with each flora can jointly and independently explain the variation in floristic elements in local floras. METHODS: A study was made of 261 local floras, 28 province-level floras and one national-level flora across China. Genera of seed plants in each flora were assigned to 14 floristic elements according to their worldwide geographical distributions. The composition of floristic elements was related to climatic and geographical factors. KEY RESULTS AND CONCLUSIONS: Variations in percentages of cosmopolitan, tropical and temperate genera among local floras tend to be greater at higher latitudes than at lower latitudes. Latitude is strongly correlated with the proportions of 13 of the 14 floristic elements. Correlations of the proportions of floristic elements with longitude are much weaker than those with latitude. Climate represented by the first principal component of a principal component analysis was strongly correlated with the proportions of floristic elements in local floras (|r| = 0.75 +/- 0.18). Geographical coordinates independently explained about four times as much variation in floristic elements as did climate. Further research is necessary to examine the roles of water-energy dynamics, geology, soils, biotic interactions, and historical factors such as land connections between continents in the past and at present in creating observed floristic patterns.     

中国种子植物特有属的地理分布格局

生物特有现象的地理格局及其形成机制是生物地理学的重要研究内容.本文通过整合173个地区的中国种子植物特有属编目资料、环境和空间因子数据,运用多元回归和方差分解的方法,探索了中国种子植物特有属丰富度及其占全部种子植物属丰富度的比例(特有属比例)与环境(生境异质性和气候)和空间因子的关系.结果表明:(1)特有属丰富度及特有...     

Historical processes enhance patterns of diversity along latitudinal gradients

One of the more vexing issues in ecology is how historical processes affect contemporary patterns of biodiversity. Accordingly, few models have been presented. Two corollary models (centre of origin, time-for-speciation) can be used to make quantitative predictions characterizing the tropical niche conservatism hypothesis and describe diversification as diffusion and subsequent cladogenesis of species away from the place of origin of a higher taxon in the tropics. Predictions derived from such models are: (i) species richness declines toward the periphery of the range of a higher taxon; (ii) taxa are more derived toward the periphery than the centre; (iii) ages of taxa are lower toward the periphery than the centre; and (iv) ages and measures of derivedness are less variable toward the periphery of the range of a higher taxon. I tested these predictions to better understand the formation of one of the most ubiquitous patterns of biodiversity-the latitudinal gradient in species richness. Results indicate well-supported predictions for New World leaf-nosed bats and that diversification has had strong influences on latitudinal gradients of species richness. A better understanding of how evolutionary diversification of taxa contributes to formation of patterns of species richness along environmental gradients is necessary to fully understand spatial variation in biodiversity.     

Ecological distribution of endemic genera of Taxads and Conifers in China and neighbouring area in relation to phytogeographical significance

With highly varied ecological conditions resulted from wide latitudinal and altitudinal ranges and from adequate precipitation, China has developed a very rich flora of great diversity. As far as Taxads and Conifers is concerned, there are 158 species and 43 varieties of them in China, belonging to 6 families and 30 genera, of which 9 genera are endemic. In the present paper the ecological distribution of these endemic genera and its phytogeographical significance are discussed. 1. There are 9 endemic genera of Taxads and Conifers in China and neighbouring area. They are distributed in the mountain areas of southern, southeastern and southwestern China (fig. 1-2) at an altitude of 100-1800 meters, with a few endemic genera reaching as high as 2800 meters. 2. The mean annual temperature varies between 10℃-20℃, with an extreme minimum between -6.3℃ to-11.3℃. The soil pH is between 4.5-5.5, indicating an acidic reaction. 3. As is shown in figure 3, 24 endemic genera of Taxads and Conifers are known to occur in differant parts of the world. Among them, China and neighbouring area ranks the first in having 9 genera. Australia is the second with 5 genera, southern Chile is third (3), followed by Japan (2), western North America (2), New Caledonia (2), and southeastern Siberia, USSR (1). Of the Chinese endemic genera, the first appearence in the fossil records is in the deposits of late Cretaceous or Tertiary (table 1.). It is probable that the southern, southeastern and south-western parts of China is not only the main centre of recent distribution, but also one of the chief survival cen-ters of endemic genera of Taxads and Conifers in the world.     

Plant community patterns in Moroccan temporary ponds along latitudinal and anthropogenic disturbance gradients

Background: Temporary ponds, an abundant habitat in the Maghreb region and notably in Morocco, have a high conservation value. However, they are mainly known from the north of the country.

Aims: The aim of this work was to characterise the vegetation of Moroccan temporary ponds along a combined gradient of latitude and anthropogenic pressure.

Methods: Eighty-five ponds distributed along a north–south gradient of 750 km were sampled. For each pond, all vegetation was surveyed (flooded and dry parts) and the local abiotic characteristics were measured during two successive hydrological cycles. The prevailing anthropogenic pressures were also identified and were attributed an impact score.

Results: Eighty-one characteristic pond species (including 17 rare species) were recorded, with several new distribution data in the southern part of the latitudinal gradient. Plant communities were related to climatic and anthropogenic factors, but mostly to local factors, such as maximum water depth and soil pH. The northern ponds (wettest macroclimate) were rich in characteristic species and rare species, while the southern (driest macroclimate) ponds were more species poor.

Conclusions: In addition to the direct impact of increasing human activity, a further reduction of the floristic richness of temporary ponds is expected due to climatic changes. This is particularly the case for characteristic species which have a high conservation value.     

Spatial patterns of the Iberian and Balearic endemic vascular flora

The Iberian flora has a high degree of originality (1328 endemic species, 24% of endemism), comparable to other regions in the Mediterranean Basin. The richness of Iberian endemic species is unevenly distributed; the greatest diversity is found in the main mountain ranges although the southwestern Atlantic coast and specially the Balearic Islands are rich in range-restricted endemic species. The largest number of endemic genera is found in the northwestern mountains, which might have acted as a refugium area. The Baetic System, which includes nearly half (46%) of the total Iberian endemic species, is by far the richest region of the territory. Its endemic flora is characterized by the great richness of narrow endemics and the high species turnover rate. The k-means partitioning analysis enables us to identify 11 units, generally well defined by the natural geographic features. The clusters including the northwestern mountains, the Cantabrian Mountains, the southwestern coast and especially the Balearic Islands, the Pyrenees and the Baetic System are compact and consist of a high proportion of diagnostic species, and can therefore be considered areas of endemism on a large scale. The regionalization reflects a primary longitudinal division of Iberia between a basic eastern and an acidic western region, but also partly reveals a climatic division between Eurosiberian and Mediterranean regions. Southeastern Iberia seems to be an important center of differentiation for several typically Mediterranean genera (e.g. Centaurea, Linaria, Armeria, Teucrium and Thymus), but other large genera are also highly diversified.     

Plants show more flesh in the tropics: variation in fruit type along latitudinal and climatic gradients

Fruit type has a major impact on seed dispersal, seed predation and energy allocation, but our understanding of large‐scale patterns in fruit type variation is weak. We used a dataset of 4008 Australian species to provide the first continental‐scale tests of a series of hypotheses about the factors that might affect fruit type. We found a significant latitudinal gradient in the proportion of fleshy‐fruited species, with the percentage of fleshy‐fruited species rising from 19% at 43.75°S to 49% at 9.25°S. Species bearing fleshy fruits were more frequent on the coastal fringes of Australia, while species bearing non‐fleshy fruits became more frequent toward the arid centre. Wet, warm and stable climates favoured fleshy‐fruited species, with the two best predictors of the proportion of fleshy‐fruited species being maximum precipitation over five days (R² = 0.40), and precipitation in the wettest month (R² = 0.25). These results remained consistent after accounting for phylogenetic correlation among species. A combined model including variables of precipitation, temperature, and climatic variation explained 67% of the variation in the proportion of fleshy‐fruited species. Our results are consistent with the idea that plant reproductive strategies are more often tied to conditions during the parts of the year in which they grow than to conditions during the harsh parts of the year. Overall, our findings demonstrate strong relationships between plant reproductive traits and environmental gradients, and improve our understanding of the factors that shape large‐scale patterns in plant ecological strategies.     

Seasonal activity patterns of Ixodes pacificus nymphs in relation to climatic conditions

Abstract In western North America, the tick Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) is the primary vector to humans and domestic animals of the disease agents causing Lyme disease and granulocytic ehrlichiosis. We examined the seasonal activity patterns of I. pacificus nymphs over a 4‐year period, including the wet and cold El Niño winter/spring of 1998, in a dry oak/madrone woodland, and for one year in a cooler and moister redwood/tanoak woodland in Mendocino County, California. Linear regressions were used to estimate when nymphal densities first exceeded and then fell below 25, 50 and 75% of the recorded yearly peak densities. In oak/madrone woodland, nymphs typically were active by mid‐March, reached 50% of their yearly peak densities in early to mid‐April, peaked by early May, fell below 50% of their peak densities by early to mid‐June, and were absent by late July to mid‐August. The lengths of the periods with nymphal densities exceeding 50 and 75% of the recorded yearly peaks in oak/madrone woodland were associated positively with rainfall and negatively with maximum air temperatures during April–May. Moreover, nymphal numbers typically reached 50% of their peak 10–15 days later, remained at levels above 50% of the peak 1.3–1.5 times longer, and started declining 4–6 weeks later under cooler, moister climatic conditions (oak/madrone woodland in 1998 and redwood/tanoak woodland in 2000) relative to warmer, drier conditions (oak/madrone woodland in 2000–2001). In oak/madrone woodland, nymphal densities typically started to decline when mean maximum daily air temperatures exceeded 23°C. Nymphal densities were higher in dry oak/madrone relative to moist redwood/tanoak woodland from mid‐March to late May 2000, similar in both habitat types in early June, but higher in redwood/tanoak woodland from late June onwards. We conclude that large‐scale studies of the density of I. pacificus nymphs in California need to consider spatial variation in the length of nymphal activity periods and select temporal sampling regimens that yield representative data for all included habitat types.     

Priorities for the conservation of avian biodiversity in China based on the distribution patterns of endemic bird genera

Ten endemic Chinese bird genera are currently recognized: Nipponia, Tetraophasis, Chrysolophus, Crossoptilon, Ithaginis, Pseudopodoces, Rhopophilus, Kozlowia, Urocynchramus and Latoucheornis. Of these genera, Nipponia, Ithaginis, Pseudopodoces, Rhopophilus, Kozlowia, Urocynchramus and Latoucheornis are monotypic, while Tetraophasis, Chrysolophus and Crossoptilon are polytypic. In this paper, we first set up a database of the geographic distribution and suitable habitat requirements for each species of these endemic genera. Secondly we produced a modified habitat-based prediction of their distribution using GIS (ArcView 3.1) software overlap analysis. We then explored the spatial–temporal distribution patterns of different genera. By comparing the richness of the endemic genera in distributed areas, we identified centers of endemic avian biodiversity. These are: the northern and eastern Hengduanshan Mountains, and the Qinling, Dabashan and Minshan Mountain regions. Finally, we identified conservation hotspots with a higher priority based on these centers. These results may provide a valuable tool for identifying and conserving areas with high endemic biodiversity and methods for researching the biogeography of endemic genera, the evolutionary history of fauna and species differentiation.     

Size and shape variability in relation to species differences and climatic gradients in the African rodent Oenomys

Aim The modern African murine rodent Oenomys is a semiarboreal genus characteristic of the rain forest zone. The size and shape geographical differentiation is studied in order to discuss the possible evolutionary patterns and constraints leading to this distribution. Location Two species of Oenomys have been previously recognized, corresponding to the West African forest block on the one hand and to the main forest block on the other hand. Both species have been sampled, and forty localities permit the study of the whole geographical range of Oenomys, from Guinea to Kenya. Methods A Fourier analysis applied to the outlines of the first upper and lower molars allows a quantification of the size and shape variations across the geographical range of Oenomys. Results This morphometrical analysis defines three morphological groups of Oenomys, corresponding to the West, Central, and East African forest zone. This result suggests the existence of an additional cryptic species. The Western group is characterized by broad asymmetrical molars and a small size. The Central African group has more elongated and larger molars while the Eastern African group displays extremely constricted molars and a small size. Main conclusion The shape can be considered as charactheristic of each group and its variations appear to be mostly related to phylogeny while size exhibits variations within each group related to climatic gradients. This discrepancy could be related to different genetic determinants for both characters, the shape being strongly genetically constrained while size can vary according to a wide range of environmental factors.     

Breeding bird diversity in relation to environmental gradients in China

Geographic variation in species richness has been explained by different theories such as energy, productivity, energy–water balance, habitat heterogeneity, and freezing tolerance. This study determines which of these theories best account for gradients of breeding bird richness in China. In addition, we develop a best-fit model to account for the relationship between breeding bird richness and environment in China. Breeding bird species richness in 207 localities (3271 km² per locality on average) from across China was related to thirteen environmental variables after accounting for sampling area. The Akaike's information criterion (AIC) was used to evaluate model performance. We used Moran's I to determine the magnitude of spatial autocorrelation in model residuals, and used simultaneous autoregressive model to determine coefficients of determination and AIC of explanatory variables after accounting for residual spatial autocorrelation. Of all environmental variables examined, normalized difference vegetation index, a measure of plant productivity, is the best variable to explain the variance in breeding bird richness. We found that species richness of breeding birds at the scale examined is best predicted by a combination of plant productivity, elevation range, seasonal variation in potential evapotranspiration, and mean annual temperature. These variables explained 47.3% of the variance in breeding bird richness after accounting for sampling area; most of the explained variance in richness is attributable to the first two of the four variables.     

中国伞形科特有属的核型演化及地理分布

首次报道了我国伞形科１０个特有属９种１变种１４个居群的核型,染色体基数分别为ｎ＝６,８,１０和１１,核型类型有２Ａ,３Ａ和４Ａ三种类型。根据各属的核型演化水平并结合其花粉形态,初步确定东俄芹属（Ｔｏｎｇｏｌｏａ）、环根芹属（Ｃｙｃｌｏｒｈｉｚａ）、明党参属（Ｃｈａｎｇｉｕｍ）和川明参属（Ｃｈｕａｍｉｎｓｈｅｎ）是古特有属,其余各属则处于中等或较高的演化水平上。同时初步讨论了各特有属在伞形科分类系统中的核型演化关系并比较了各主要分布区之间核型的演化水平,发现横断山地区不仅特有属数目高,染色体基数变化大,且集中了核型较为原始和演化程度很高的类群,极可能是伞形科特有属的起源和分化中心。     

大巴山自然保护区种子植物中国特有属的初步研究

大巴山自然保护区分布中国特有属45属,占本区的种子植物总属的4.98%。本区分布的中国种子植物特有属中均为少种属或单种属,单种属22属,少种属23属,分别占本区中国特有属总属数的48.9% 和51.1%。木本属22属,草本属23属,分别占本区中国特有属总属数的48.9% 和51.1%。本区的中国特有属植物主要分布在低山和中山,其中分布在低山的有6属,占总属数的13.3%, 分布在中山的有39属,占总属数的86.7%。其特点表现为众多的古特有属、较明显的过渡性质和丰富的珍稀物种,与四川和湖北的共有成分最多,是中国特有属川东鄂西特有现象中心的重要组成部分。     

Spatial patterns and feeding of meiobenthic harpacticoid copepods in relation to resident microbial flora

Distributional and feeding relationships of harpacticoid copepods and their microbial prey were examined in a tidal channel at Great Sippewissett Marsh. A horizontal zonation of photosynthetic microorganisms was composed of: 1) a diatom area; 2) a purple sulfur bacterial (Thiocapsa sp.) area; and 3) a clear area. Four species of harpacticoid copepods were associated with given areas. Leptocaris brevicornis occurred in very high densities in the diatom area but in relatively low densities in other areas. Mesochra lilljeborgi occurred in significantly higher densities in the purple and clear areas.Feeding experiments, using resident microbial flora labelled with NaH¹⁴CO₃ and ³H-thymidine, were conducted to determine which foods are 1) ingested but simply pass through the gut and 2) ingested, and retained. These experiments indicated that L. brevicornis ingested diatoms and the heterotrophs associated with the diatoms, but only retained the heterotrophic portion. Microscopic examination indicated that diatoms were passed out intact in feces. Oscillatoria sp. (cyanobacterium) was not ingested. Mesochra lilljeborgi ingested Spirulina sp. (cyanobacterium), Thiocapsa sp., and the heterotrophs associated with Thiocapsa but only retained the Thiocapsa label.These data for harpacticoids suggest that spatial distributions of meiofauna may be closely coupled with microbial food organisms which they consume. Also, that while several microbial foods may be ingested, only certain microbes are digested and assimilated as a food resource, further indicating the complexity of feeding relationships among the meiofauna.     

Divergent selection along climatic gradients in a rare central European endemic species,Saxifraga sponhemica

Background and Aims The effects of habitat fragmentation on quantitative genetic variation in plant populations are still poorly known. Saxifraga sponhemica is a rare endemic of Central Europe with a disjunct distribution, and a stable and specialized habitat of treeless screes and cliffs. This study therefore used S. sponhemica as a model species to compare quantitative and molecular variation in order to explore (1) the relative importance of drift and selection in shaping the distribution of quantitative genetic variation along climatic gradients; (2) the relationship between plant fitness, quantitative genetic variation, molecular genetic variation and population size; and (3) the relationship between the differentiation of a trait among populations and its evolvability.Methods Genetic variation within and among 22 populations from the whole distribution area of S. sponhemica was studied using RAPD (random amplified polymorphic DNA) markers, and climatic variables were obtained for each site. Seeds were collected from each population and germinated, and seedlings were transplanted into a common garden for determination of variation in plant traits.Key Results In contrast to previous results from rare plant species, strong evidence was found for divergent selection. Most population trait means of S. sponhemica were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with geographical distance, even when neutral molecular divergence was controlled for, and Q_ST exceeded F_ST for some traits. The evolvability of traits was negatively correlated with the degree of differentiation among populations (Q_ST), i.e. traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion.Conclusions The findings suggest that studies of molecular and quantitative genetic variation may provide complementary insights important for the conservation of rare species. The strong differentiation of quantitative traits among populations shows that selection can be an important force for structuring variation in evolutionarily important traits even for rare endemic species restricted to very specific habitats.     

Peatland distibution along a north-south transect in the Mackenzie River Basin in relation to climatic and environmental gradients

Climate is a major factor affecting the development and form of peatlands, as well as the distribution of individual bryophyte species. This paper examines the climatic and ecological gradients affecting the distribution of peatland types along a north-south gradient in the Mackenzie River Basin. Based on a TWINSPAN analysis of bryophyte abundance from 82 peatlands in the Mackenzie River Basin, seven peatland types, two with southerly geographical distributions are recognized. In the Mackenzie River Basin, such local factors as surface water chemistry, pH, and solute concentration as well as height above the water table play a significant role in determinining bryophyte species distributions. Climate is secondary. Amongst the climatic variables, precipitation, length of the growing season, and annual temperature are the most signifcant. The seven peatland groups are: widespread poor fens; peat plateaus with thermokarst pools, low-Boreal bogs; bogs and peat plateus without thermokarst pools; low-Boreal dry poor fens; wet moderate-rich fens; and wet extreme-rich fens.