Relationships between temperature responses and bacterial community structure along seasonal and altitudinal gradients

In this study, soil bacterial communities and the temperature responses (Q10) of substrate-induced respiration were compared between an alpine dry meadow and a subalpine forest in the Colorado Rocky Mountains. Bacterial communities in three seasons from each environment were described with 16S rRNA gene clone libraries. The main goal of this comparison was to relate phylogenetic differences among bacterial communities with variation in soil respiratory temperature sensitivities along seasonal and altitudinal gradients. The warmer, lower elevation, subalpine forest soil exhibited large seasonal variations in Q10. Subalpine Q10 values were highest in summer, and were higher than alpine values in all seasons except winter. Q10 in alpine soils were consistently low throughout the year. Alpine and subalpine bacterial communities both varied seasonally, and were markedly distinct from each other. Based on Fst analysis, subalpine communities from colder times of year were more similar to the alpine communities than were subalpine summer communities. Principle component analysis of the pairwise genetic distances (Fst) between communities produced two factors that accounted for 69% and 22% of the total variance in the data set. These factors demonstrated a significant relationship between bacterial community structure and temperature response when regressed on log-transformed Q10 data.     

Floral size variation in Campanula rotundifolia (Campanulaceae) along altitudinal gradients: patterns and possible selective mechanisms

We investigated patterns of flower‐size variation along altitudinal gradients in the bee‐pollinated perennial Campanula rotundifolia (Campanulaceae) by examining 22 Norwegian populations at altitudes between 240 and 1100 m a.s.l. We explored potential mechanisms for the underlying pattern by quantifying pollinator–faunal composition, pollinator‐visitation rates and pollen limitation of seed set in subsets of the study populations. Despite a decrease in plant size, several measures of flower size increased with elevation. Bumble bees were the main pollinators at both alpine and lowland sites in the study area. However, species composition of the pollinator fauna differed, and pollinators were larger in higher‐elevation than in lower‐elevation sites. Pollinator visitation rates were lower at higher‐elevations than at lower elevations. Pollen limitation of seed set did not vary significantly with altitude. Our results are consistent with differences in bumble‐bee size and visitation rates as causal mechanisms for the relatively larger flowers at higher elevations, in three non‐mutually exclusive ways: 1) Larger flowers reflect selection for increased attractiveness where pollinators are rare. 2) Larger and fewer flowers represent a risk avoidance strategy where the probability of pollination is low on any given day. 3) Flower size variation reflects selection to improve the fit of pollinators with fertile structures by matching flower size to pollinator size across sites.     

Avian life history variation along altitudinal gradients: an example with cardueline finches

Elevation has long been considered a major influence on the evolution of life-history traits. Most elevation-induced variation in life history traits has been attributed to changes in climate, duration of breeding season, predation, and food limitation. I use a phylogenetic approach to show that life histories are closely associated with breeding elevation in extant cardueline finches. Finches at high elevations had smaller clutches, fewer broods, and longer incubation periods. Neither food limitation nor nest predation appear to readily account for this strong elevational variation in cardueline life histories. However, juvenile survival may be greater at higher elevations as a result of prolonged parental care and shorter natal dispersal and can potentially compensate for reduced fecundity in high-elevation finches. Received: 28 September 1996 / Accepted: 24 March 1997     

中华山蓼不同海拔居群的繁殖分配研究

研究了具有克隆繁殖和雌雄异株繁育特性的中华山蓼Oxyria sinensis Hemsl.在5个不同海拔居群的繁殖分配.结果表明:(1)雄株高度和茎叶总生物量仪在海拔2780 m的居群显著高于雌株,在另外4个居群与雌株高度和茎叶总生物量均不存在显著差异:雄株地上部分总生物量在海拔较高的3个届群显著高于雌株的地上部分总生物量;雄株的花生物量和繁殖分配在海拔1978 m的居群与雌株没有显著差异,但在另外4个居群均显著高于雌株,表明在海拔较高的地区,中华山蓼增加了对雄性植株的资源配置,可能是对海拔较高地区不可预见性降雨和降低昆虫访花频率的适应.(2)雌雄株高度、地上部分总生物量和茎叶生物量以及雌株的花生物量和繁殖分配随海拔升高表现出降低的趋势,但雄花的生物量和繁殖分配随海拔升高显著增加,进一步证明中华山蓼在海拔较高地区的居群增加了对雄性资源的投资.(3)雄雌株繁殖分配受个体大小制约(个体大小依赖性),但并不支持"植物开始繁殖必须达到一定的大小(阈值)"的观点.这可能因为中华山蓼具有较强的无性繁殖能力,而同一植株上不同分株间能通过地下根状茎达到资源共享,因此中华山蓼分株的开花繁殖不需要达到一定的大小.     

Variation among populations of Clarkia Unguiculata (Onagraceae) along altitudinal and latitudinal gradients

We investigated phenotypic variation in 15 traits in greenhouse-grown plants from 16 populations of Clarkia unguiculata from three elevational habitats and six latitudinal transects. Populations from the lowest and highest elevations were geographically and ecologically marginal within the species' range. We (1) describe patterns of trait variation with elevation and latitude; (2) compare latitutidinal variation between marginal and central areas of the species' range; and (3) compare patterns of variation within C. unguiculata to interspecific patterns within the genus. Although there was some evidence that traits varied clinally (i.e., increased/decreased monotonically) along environmental gradients, interaction effects between altitude and latitude dominated patterns of variation. For most traits, latitudinal trends at the low-elevation margin of the species' range differed from trends at mid- and high-elevation areas. Based on interspecific comparisons, populations at the hotter, more arid ends of both environmental gradients were expected to have rapid development, small flowers and vegetative size, low levels of herkogamy and protandry, and high rates of gas exchange. Instead, we found that while some traits were correlated with one gradient in the expected way (e.g., development time with elevation, gas-exchange physiology with latitude), all traits were not consistently associated with each other along both gradients, and intraspecific patterns of variation differed from interspecific patterns.     

Evidence of neutral and adaptive genetic divergence between European trout populations sampled along altitudinal gradients

Species with a wide geographical distribution are often composed of distinct subgroups which may be adapted to their local environment. European trout (Salmo trutta species complex) provide an example of such a complex consisting of several genetically and ecologically distinct forms. However, trout populations are strongly influenced by human activities, and it is unclear to what extent neutral and adaptive genetic differences have persisted. We sampled 30 Swiss trout populations from heterogeneous environments along replicated altitudinal gradients in three major European drainages. More than 850 individuals were genotyped at 18 microsatellite loci which included loci diagnostic for evolutionary lineages and candidate markers associated with temperature tolerance, reproductive timing and immune defence. We find that the phylogeographic structure of Swiss trout populations has not been completely erased by stocking. Distinct genetic clusters corresponding to the different drainages could be identified, although nonindigenous alleles were clearly present, especially in the two Mediterranean drainages. We also still detected neutral genetic differentiation within rivers which was often associated with the geographical distance between populations. Five loci showed evidence of divergent selection between populations with several drainage-specific patterns. Lineage-diagnostic markers, a marker linked to a quantitative trait locus for upper temperature tolerance in other salmonids and a marker linked to the major histocompatibility class I gene were implicated in local adaptation and some patterns were associated with altitude. In contrast, tentative evidence suggests a signal of balancing selection at a second immune relevant gene (TAP2). Our results confirm the persistence of both neutral and potentially adaptive genetic differences between trout populations in the face of massive human-mediated dispersal.     

Homogeneous genetic structure and variation in tree architecture of <Emphasis Type="Italic">Larix kaempferi</Emphasis> along altitudinal gradients on Mt. Fuji

Variations in tree architecture and in the genetic structure of Larix kaempferi on Mt. Fuji were surveyed along altitudinal gradients using 11 nSSR loci. In total, 249 individuals from six populations along three trails at altitudes ranging from approximately 1,300 to 2,700 m were investigated. Gradual changes in tree architecture with increasing elevation, from erect trees to flag trees and krummholz mats, were observed in the high-altitude populations (>2,000 m) on all trails. These findings suggest that tree architecture is correlated with the severe environmental conditions associated with increasing elevation, such as strong winds. In contrast to obvious variations in tree architecture, the genetic diversity of populations along the trails was almost uniform (H _E = 0.717–0.762) across the altitudinal range. The results of the AMOVA and STRUCTURE analyses, and the analysis for isolation by distance pattern, suggest homogeneous genetic structuring across all populations on Mt. Fuji, while the pairwise F _ST showed barriers to gene flow between altitudinal populations that were demarcated as high- or low-altitude populations by Abies-Tsuga forest. Although the evergreen coniferous forests on the mountainside may hinder gene flow, this may be explained by the long-distance seed dispersal of the Japanese larch and/or a short population history resulting from eruptions or slush avalanches, although evergreen coniferous forests on the mountainside may hinder gene flow.     

Size and reproduction of Thelypteris limbosperma and Athyrium distentifolium along environmental gradients in Western Norway

The performance of the ferns Thelypteris limbospgrma and Athyrium distentifolium , as expressed by number of son on pinnules and frond size, has been related to environmental gradients. Data have been collected from homogenous fern-dominated stands from different geographical areas in Western Norway. Number of sori produced, which was assumed to indicate fern fertility, was highly variable. There were significant correlations between frond size and fertility, but only 35–46 % of the variation in fertility could be explained by differences in frond size. The highest number of sori was found on plants of medium size, and for A. distentifolium there was a statistically significant reduction in sori number on fronds taller than 125 cm. For the linear relationships between fertility and size, it is suggested that the small X-intercept and slope defines the high competitive ability of A. distentifolium in sites with a long-lasting snow cover. The ferns may dominate in large stands even though their fertility is low or zero, which indicates that they under certain ecological conditions mainly reproduce vegetatively. Both ferns show decreased fertility both toward their altitudinal and lowland distribution limits, but their fertility optima were different. The performances of the two fern species showed highly different responses to geographical and climatical variables. The fertility of T. limbosperma could be predicted by mean July- and January temperatures, humidity and canopy cover, while the fertility of A. distentifolium could not be predicted by any of the site environmental variables investigated.     

Patterns of seasonal activity in a Mediterranean lizard along a 2200 m altitudinal gradient

Ectothermy in reptiles involves strong environmental temperature dependence to maintain body temperature. High mountains are extreme habitats which, because of their marked temperature decrease with altitude, impose difficulties for reptile thermoregulation, as the number of optimum-temperature days diminish in altitude. We studied the activity patterns of the lizard Psammodromus algirus, which has a wide altitudinal distribution, at six sampling stations that spanned an altitudinal range from 300 to 2500 m asl in Sierra Nevada (SE Iberian Peninsula). We performed censuses of the species during the seasonal and daily activity period, and measured lizard body temperature and environmental temperature in the six sampling plots along the altitude gradient. The body temperature of the lizards remained closely the same even though environmental temperature decreased around 9°C along that gradient. Seasonal activity peaked at the beginning of the activity period in highlands, but in the middle of the season in middle and lowland regions. However, newborns appeared in the field almost at the same time along the altitude gradient. We suggest that the thermoregulatory strategies of the lizards must vary along this altitudinal gradient, permitting lizards to keep their body temperature close to a very similar optimum and thus, develop very similar circa-annual activity patterns.     

Vascular plant species richness along latitudinal and altitudinal gradients: a contribution from New Zealand temperate rainforests

Vascular plant species richness is known to often decrease with both increasing latitude and increasing altitude. However, a number of studies have shown the reverse trend and the primary cause of these gradients remains unknown. In the present work, generalized linear models were used to assess the relative importance of latitude and altitude as well as of a number of other factors (mean annual precipita-tion, slope, substrate and forest type) on species richness in temperate rainforests of New Zealand. The effect of Southern beech ( Nothofagus spp.) as dominant canopy species on total species richness was shown to be much smaller than postulated in most previous studies. Within the region studied, altitude had by far the strongest effect on species richness. This effect was independent of latitude and was significant for woody but not for herbaceous vegetation.     

Clinal differentiation during invasion: <Emphasis Type="Italic">Senecio inaequidens</Emphasis> (Asteraceae) along altitudinal gradients in Europe

The dynamics of plant population differentiation may be integral in predicting aspects of introduced species invasion. In the present study, we tested the hypothesis that European populations of Senecio inaequidens (Asteraceae), an invasive species with South African origins, differentiated during migration from two independent introduction sites into divergent altitudinal and climatic zones. We carried out 2 years of common garden experiments with eight populations sampled from Belgian and ten populations from French altitudinal transects. The Belgian transect followed a temperature and precipitation gradient. A temperature and summer drought gradient characterized the French transect. We evaluated differentiation and clinal variation in plants germinated from field-collected seed using the following traits: days to germination, days to flowering, height at maturity, final plant height and aboveground biomass. Results showed that S. inaequidens populations differentiated in growth traits during invasion. During the 1st year of sampling, the results indicated clinal variation for growth traits along both the Belgium and French altitudinal transects. Data from the 2nd year of study demonstrated that with increasing altitude, a reduction in three growth traits, including plant height at maturity, final plant height and aboveground biomass, was detected along the French transect, but no longer along the Belgian one. Phenological traits did not exhibit a clear clinal variation along altitudinal transects. The possible evolutionary causes for the observed differentiation are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Relationships between below-ground biomass and foliar N:P stoichiometry along climatic and altitudinal gradients of the Chinese grassland transect

N and P concentrations and their ratios were determined for 132 foliar and 120 below-ground biomass (BGB) samples obtained at 132 sites along the 4500 km Chinese Grassland Transect (CGT) across the Inner Mongolian and Qinghai–Tibet Plateaus. Patterns of foliar and BGB N, P and their ratio (N/P) at the community level were related to altitude, temperature, and precipitation gradients. Also, patterns of relative N and P foliar and BGB concentrations were determined (N_F/B, foliar N/BGB N; P_F/B, foliar P/BGB P). The relationship between foliar N concentrations and mean annual temperature (MAT) was negative, agreeing with the Temperature-Plant Physiological hypothesis, whereas BGB N decreased with decreasing MAT, supporting the Biogeochemical hypothesis. Patterns of BGB N varying with altitude, MAP and MAT differed from the patterns for leaf N, which may indicate differences in nutrient allocation and utilization by leaves and BGB. N_F/B and P_F/B may reflect trade-offs by plants for N and P in leaves and BGB. For the entire CGT, N_F/B and P_F/B increased as altitude increased. N_F/B was positively related with MAP but negatively related with MAT, while P_F/B showed no correlations with MAP and MAT. Results suggest that ecological stoichiometry at the community level is similar to that at the species level. Strategies of nutrient utilization by leaves and BGB are indicated to be different, and abiotic environmental conditions could influence the stoichiometric characteristics and nutrient allocation to leaves and BGB.     

Phenotypic divergence of the common toad (Bufo bufo) along an altitudinal gradient: evidence for local adaptation

Variation in the environment can induce different patterns of genetic and phenotypic differentiation among populations. Both neutral processes and selection can influence phenotypic differentiation. Altitudinal phenotypic variation is of particular interest in disentangling the interplay between neutral processes and selection in the dynamics of local adaptation processes but remains little explored. We conducted a common garden experiment to study the phenotypic divergence in larval life-history traits among nine populations of the common toad (Bufo bufo) along an altitudinal gradient in France. We further used correlation among population pairwise estimates of quantitative trait (Q_ST) and neutral genetic divergence (F_ST from neutral microsatellite markers), as well as altitudinal difference, to estimate the relative role of divergent selection and neutral genetic processes in phenotypic divergence. We provided evidence for a neutral genetic differentiation resulting from both isolation by distance and difference in altitude. We found evidence for phenotypic divergence along the altitudinal gradient (faster development, lower growth rate and smaller metamorphic size). The correlation between pairwise Q_STs–F_STs and altitude differences suggested that this phenotypic differentiation was most likely driven by altitude-mediated selection rather than by neutral genetic processes. Moreover, we found different divergence patterns for larval traits, suggesting that different selective agents may act on these traits and/or selection on one trait may constrain the evolution on another through genetic correlation. Our study highlighted the need to design more integrative studies on the common toad to unravel the underlying processes of phenotypic divergence and its selective agents in the context of environmental clines.     

Biomass and diversity of dry alpine plant communities along altitudinal gradients in the Himalayas

A non-linear relationship between phytodiversity and altitude has widely been reported, but the relationship between phytomass and altitude remains little understood. We examined the phytomass and diversity of vascular plants along altitudinal gradients on the dry alpine rangelands of Ladakh, western Himalaya. We used generalized linear and generalized additive models to assess the relationship between these vegetation parameters and altitude. We found a hump-shaped relationship between aboveground phytomass and altitude. We suspect that this is engendered by low rainfall and trampling/excessive grazing at lower slopes by domestic livestock, and low temperature and low nutrient levels at higher slopes. We also found a unimodal relationship between plant species-richness and altitude at a single mountain as well as at the scale of entire Ladakh. The species-richness at the single mountain peaked between 5,000 and 5,200 m, while it peaked between 3,500 and 4,000 m at entire Ladakh level. Perhaps biotic factors such as grazing and precipitation are, respectively, important in generating this pattern at the single mountain and entire Ladakh.     

<Emphasis Type="Italic">Athyrium sessilipinnum</Emphasis>: A new lady fern (Athyriaceae) from southern China

A new species of Athyrium from southern China is described and illustrated as Athyrium sessilipinnum. Morphological comparisons among this new species and similar ones (e.g., A. arisanense, A. gedeanum, A. epirachis, and A. otophorum) are provided. Molecular evidence reveals a sister relationship between the new species and A. arisanense. The most distinctive characters of A. sessilipinnum are the sessile, non-pinnatifid and non-shortened pinnae.     

Patterns of variation in cultivated common bean (Phaseolus vulgaris,Fabaceae)

More than 18,000 accessions of common bean (Thaseolus vulgaris, Fabaceae) from the Centro Internacional de Agricultura Tropical (CIAT) germplasm bank were examined at two locations in Colombia. A large variation in cultivated dry bean was found among accessions from primary centers of domestication in Middle and South America. For some bean types, such as medium- and large-seeded white, variation was greater among germplasm from western Asia (Turkey) and Europe (Portugal, Spain, Greece, France, Italy, and Bulgaria). Based on growth habit, on seed, pod, and leaf characteristics, and on ecological regions of adaptation, dry-bean germplasm was divided into a total of six gene pools from Middle American and four gene pools from South American centers of domestication. Most of the variation in the snap or stringless bean appears to be of relatively recent origin; it was greatest among cultivars from China, Europe, and the United States. These could be grouped into two additional gene pools. A strategy for breeding and transfer of genes across gene pools is also discussed.     

Phenological and growth responses of Papaver radicatum along altitudinal gradients in the Canadian High Arctic

Phenology and growth of Papaver radicatum Rottb. was monitored over four summers (1990–1993) at 12 sites, along a dolomitic and a granitic altitudinal gradient (330 m a.s.l.–770 m a.s.l.) at Sverdrup Pass, central Ellesmere Island, Canada. The gradients provided substantial differences in environmental characteristics. Three of the four seasons (1990, 1991 and 1993) had more than 400 thawing degree-days (TDD) in the valley, while the 1992 season had less than 300. The granitic sites had consistently higher temperatures than the dolomitic sites, despite their northerly aspect. Increasing elevation reduced total degree-day accumulation ( c . 40 degree-days/100 m) and length of potential growing season. The proportion of the population producing flower buds was similar at all sites in any given year, but there were differences among years. Production of flowers and fruits per site, decreased with altitude along the dolomitic gradient in 1991 and 1992. There was no difference in the number of buds or flowers produced per plant with increasing altitude, although larger plants with multiple flowers were found only on low elevation granitic sites. Plants from the dolomitic sites were smaller and flowered, on average, after the site accumulated 150 degree-days, while plants on the granitic sites were larger and bloomed after 200 degree-days. Papaver is able to grow and reproduce over a wide range of environmental conditions and moderate climate warming would likely promote its growth and establishment, unless other factors, especially snow-free periods and water availability, become limiting.