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  • Volume 1 Issue 3
    Research Articles
    Patrick Kuss, Andrea R. Pluess, Hafdís Hanna Ægisdóttir, Jürg Stöcklin
    2008, 1 (3): 149-159 .
    Abstract ( 207 )   PDF   Save
    Aims The effect of anthropogenic landscape fragmentation on the genetic diversity and adaptive potential of plant populations is a major issue in conservation biology. However, little is known about the partitioning of genetic diversity in alpine species, which occur in naturally fragmented habitats. Here, we investigate molecular patterns of three alpine plants (Epilobium fleischeri, Geum reptans and Campanula thyrsoides) across Switzerland and ask whether spatial isolation has led to high levels of population differentiation, increasing over distance, and a decrease of within-population variability. We further hypothesize that the contrasting potential for long-distance dispersal (LDD) of seed in these species will considerably influence and explain diversity partitioning.
    Methods For each study species, we sampled 20–23 individuals from each of 20–32 populations across entire Switzerland. We applied Random Amplified Polymorphic Dimorphism markers to assess genetic diversity within (Nei's expected heterozygosity, H e; percentage of polymorphic bands, P p) and among (analysis of molecular variance, Φ st) populations and correlated population size and altitude with within-population diversity. Spatial patterns of genetic relatedness were investigated using Mantel tests and standardized major axis regression as well as unweighted pair group method with arithmetic mean cluster analyses and Monmonier's algorithm. To avoid known biases, we standardized the numbers of populations, individuals and markers using multiple random reductions. We modelled LDD with a high alpine wind data set using the terminal velocity and height of seed release as key parameters. Additionally, we assessed a number of important life-history traits and factors that potentially influence genetic diversity partitioning (e.g. breeding system, longevity and population size).
    Important findings For all three species, we found a significant isolation-by-distance relationship but only a moderately high differentiation among populations (Φ st : 22.7, 14.8 and 16.8%, for E. fleischeri, G. reptans and C. thyrsoides, respectively). Within-population diversity (H e : 0.19–0.21, P p : 62–75%) was not reduced in comparison to known results from lowland species and even small populations with <50 reproductive individuals contained high levels of genetic diversity. We further found no indication that a high long-distance seed dispersal potential enhances genetic connectivity among populations. Gene flow seems to have a strong stochastic component causing large dissimilarity between population pairs irrespective of the spatial distance. Our results suggest that other life-history traits, especially the breeding system, may play an important role in genetic diversity partitioning. We conclude that spatial isolation in the alpine environment has a strong influence on population relatedness but that a number of factors can considerably influence the strength of this relationship.
    Markus Fischer, Eckart Winkler, Bernhard Schmid
    2008, 1 (3): 161-171 .
    Abstract ( 154 )   PDF   Save
    Aims Phenotypic optimality models neglect genetics. However, especially when heterozygous genotypes are fittest, evolving allele, genotype and phenotype frequencies may not correspond to predicted optima. This was not previously addressed for organisms with complex life histories.
    Methods Therefore, we modelled the evolution of a fitness-relevant trait of clonal plants, stolon internode length. We explored the likely case of an asymmetric unimodal fitness profile with three model types. In constant selection models (CSMs), which are gametic, but not spatially explicit, evolving allele frequencies in the one-locus and five-loci cases did not correspond to optimum stolon internode length predicted by the spatially explicit, but not gametic, phenotypic model. This deviation was due to the asymmetry of the fitness profile. Gametic, spatially explicit individual-based (SEIB) modeling allowed us relaxing the CSM assumptions of constant selection with exclusively sexual reproduction.
    Important findings For entirely vegetative or sexual reproduction, predictions of the gametic SEIB model were close to the ones of spatially explicit non-gametic phenotypic models, but for mixed modes of reproduction they approximated those of gametic, not spatially explicit CSMs. Thus, in contrast to gametic SEIB models, phenotypic models and, especially for few loci, also CSMs can be very misleading. We conclude that the evolution of traits governed by few quantitative trait loci appears hardly predictable by simple models, that genetic algorithms aiming at technical optimization may actually miss the optimum and that selection may lead to loci with smaller effects in derived compared with ancestral lines.
    Mark van Kleunen, Anna Meier, Moritz Saxenhofer, Markus Fischer
    2008, 1 (3): 173-178 .
    Abstract ( 188 )   PDF   Save
    Aims Floral traits are frequently used in traditional plant systematics because of their assumed constancy. One potential reason for the apparent constancy of flower size is that effective pollen transfer between flowers depends on the accuracy of the physical fit between the flower and pollinator. Therefore, flowers are likely to be under stronger stabilizing selection for uniform size than vegetative plant parts. Moreover, as predicted by the pollinator-mediated stabilizing selection (PMSS) hypothesis, an accurate fit between flowers and their pollinators is likely to be more important for specialized pollination systems as found in many species with bilaterally symmetric (zygomorphic) flowers than for species with radially symmetric (actinomorphic) flowers.
    Methods In a comparative study of 15 zygomorphic and 13 actinomorphic species in Switzerland, we tested whether variation in flower size, among and within individuals, is smaller than variation in leaf size and whether variation in flower size is smaller in zygomorphic compared to actinomorphic species.
    Important findings Indeed, variation in leaf length was significantly larger than variation in flower length and width. Within-individual variation in flower and leaf sizes did not differ significantly between zygomorphic and actinomorphic species. In line with the predictions of the PMSS, among-individual variation in flower length and flower width was significantly smaller for zygomorphic species than for actinomorphic species, while the two groups did not differ in leaf length variation. This suggests that plants with zygomorphic flowers have undergone stronger selection for uniform flowers than plants with actinomorphic flowers. This supports that the relative uniformity of flowers compared to vegetative structures within species, as already observed in traditional plant systematics, is, at least in part, a consequence of the requirement for effective pollination.
    Xin-Sheng Chen, Qing-Jun Li
    2008, 1 (3): 179-185 .
    Abstract ( 233 )   PDF   Save
    Aims Sexual systems influence many components of the ecology and evolution of plant populations and have rarely been documented in subtropical evergreen broad-leaved forests (SEBLF). Here we report frequency distribution and ecological correlates of plant sexual systems in SEBLF at Ailao Mountains, and compare our results with that of tropical and cool temperate forests.
    Methods We examine the sexual systems of 703 species of woody angiosperms belonging to 103 families and 296 genera based on a comprehensive survey of SEBLF at Ailao Mountains Natural Reserve. Information of plant sexual systems and ecological traits were mainly based on published literatures and specimens as well as our field observations. The associations between plant sexual system and ecological traits were assessed with chi-square tests.
    Important findings Among these species, 60.2% were hermaphroditic, 15.8% were monoecious and 24.0% were dioecious. The percentage of dioecious sexual system among tree species (22.2%) in SEBLF was comparable to those of tropical tree floras, but much higher than those of temperate forests at North America. The percentage of monoecious sexual system among tree species (30.1%) in SEBLF was higher than that of tropical tree floras, but much lower than those of temperate forests at North America. Monoecy was significantly associated with the tree growth form and was relatively common in temperate genera. Dioecy was significantly associated with fleshy fruits and monoecy was significantly associated with dry fruit type in SEBLF. The high percentage of diclinous sexual systems (monoecy and dioecy) in SEBLF may be associated with the origin of the flora and the prevalence of relatively small inconspicuous flowers of the forests in the Oriental Region.
    Erika A. Sudderth, F. A. Bazzaz
    2008, 1 (3): 187-195 .
    Abstract ( 141 )   PDF   Save
    Aims Elevated CO2 and increased N availability can alter a variety of plant physiological processes leading to changes in the nutritional quality of leaf tissue for herbivores. Numerous experiments have examined the responses of herbivores to environmental change; however the potential effects of simultaneous change in multiple factors on leaf-chewing insect herbivores are less well understood. The plant-mediated effects of elevated CO2 and high N on the performance of a generalist leaf-chewing insect herbivore, Trichoplusia ni, were investigated.
    Methods Newly hatched T. ni larvae were introduced to Amaranthus viridis and Polygonum persicaria plants grown under ambient and elevated CO2 and low and high N conditions. Insect performance was assessed by measuring larvae weight after ten days of feeding. Plant photosynthesis, biomass, leaf area and specific leaf weight were measured to determine the effects of elevated CO2, N and insect feeding on plant performance.
    Important findings Elevated CO2 did not have strong effects on plant or insect performance, only affecting a few responses under low or high N conditions, but not both. Growth under high nitrogen improved almost all measures of plant performance. Trichoplusia ni performed significantly better on Amaranthus viridis (C 4) compared to Polygonum persicaria (C 3), despite similar leaf C:N ratios in both species. The performance of T. ni caterpillars was only improved by the high nitrogen treatment when they were feeding on P. persicaria, the host they performed poorly on. The only interactions between N and CO2 affecting plant performance were seen for leaf photosynthesis of P. persicaria and leaf area of A. viridis. Contrary to the predictions, there were no significant CO2 by N interactions affecting T. ni performance.
    Ying Wang, Nianwei Qiu, Xingan Wang, Zongqi Ma, Guozhen Du
    2008, 1 (3): 197-202 .
    Abstract ( 132 )   PDF   Save
    Aims Information about how species respond to extreme environments, such as high UV-B radiation, is very useful in estimating natural ecosystem structure and functions in alpine areas. Our aim is to examine the effect of enhanced UV-B radiation on the fitness of an alpine meadow annual species on Qinghai-Tibet Plateau.
    Methods Plants of Cerastium glomeratum Thuill. were exposed to ambient (control) or ambient plus supplemental UV-B radiation (enhanced), simulating a 9% ozone depletion over Gannan, China (102°53′E, 34°55′N, 2900 m in altitude), up to leaf senescence and fruit maturation. Plant height, flower phenology, biomass allocation and reproductive parameters of the species were measured.
    Important findings Plant height in C. glomeratum was reduced by enhanced UV-B radiation at early growth stages and compensated with ongoing development. Fruit biomass, aboveground biomass, total biomass and reproductive effort (fruit dry mass/aboveground biomass) were not affected by enhanced UV-B radiation, but a significant increase in root/shoot ratio was found. Enhanced UV-B radiation delayed onset of flowering by 1 day and shortened duration of flowering by 5 days in C. glomeratum. But because of the long period of flowering time (83–88 days), this did not make any significant effect on flower number, seed number, pollination success (number of seeds per fruit) or reproductive success (fruit to flower ratio) in C. glomeratum. Enhanced UV-B radiation had no effect on seed germination and seed mass either. And the high production and low germination rate of the seed might be the strategy of C. glomeratum to survive the extreme environments on alpine meadow. All these results showed that C. glomeratum was tolerant to enhanced UV-B radiation.
    Wenfang Leng, Hong S. He, Hongjuan Liu
    2008, 1 (3): 203-205 .
    Abstract ( 133 )   PDF   Save
    Global warming has changed the distributions of forests of northeastern China. Larix are very important species in this area. Predicting the potential distributions of Larix species and their responses to climate change would attract more and more attention.This paper predicted the potential distributions of three Larix species based on 'climatic-topographic' relationships by logistic regression. The results showed that L. gmelinii is predicted to retreat northwestward by 220 km by 2050 and by 270 km more by 2100; L. olgensis var. changpaiensis is predicted to retreat northwestward by 200 km by 2050 and by 190 to 300 km more by 2100; L. principis-rupprechtii is predicted to retreat northeastward by 200 km by 2050 and by 250 to 400 km more by 2100. This indicated that L. gmelinii could have its optimum latitude moved into Russia, L. olgensis var. changpaiensis could move to the Small Xing'an Mountains and L. principis-rupprechtii would move to the middle part of the Great Xing'an Mountains.
IF: 2.7
5-year IF: 2.6
Yuanhe Yang
Bernhard Schmid
CN 10-1172/Q
ISSN 1752-9921(print)
ISSN 1752-993X(online)