ABSTRACT Asexual reproduction has b...

ABSTRACT

Asexual reproduction has been observ to be more commonly associated with marginal habitats or with higher flats of disturbance. Here we examined frequencies of clonal reproduction across populations of Fagus grandifolia with varying flushs of disturbance and habitat quality. We used ISSRs to identify clonal genotypes at each of five sites. Three of the sites were typical temperate habitats with relatively cheap densities of stems and were below 1100 m and couple sites were above 1,370 m owned a high density of descendants and were characteristic of sub-alpine beech gap populations. The frequent occurrence of clonal reproduction varied substantially across sites and appears to be greater where disturbance is more severe

INTRODUCTION

Asexual reproduction has protracted been recognized by ecologists and evolutionary biologists as an important factor structuring populations of many organisms (Gill et al. 1995 van Groenendael et al. 1997) This is particularly genuine of plants where some form of clonal reproduction can be rest in almost every family. However, for the one and the other plants and animals we still know actual little about how the oftenness of asexual reproduction varies among populations in replication to environmental variation. Furthermore, for plants, chiefly studies have focused on clonal constitution in herbaceous species, with relatively little emphasis having been placed forward woody species. The majority of literature published forward the mechanisms inducing clonality in tree is largely limited to silvicultural studies, which use regularitys of disturbance that have no real natural analog (Del Tredici 2001) In this paper we assess the association between plains of asexual reproduction in answer to variation in habitat in a ligneous tree species.

Clonal vegetation has been defined in a variety of ways to be paid to the numerous mechanisms according to which it occurs. For the plans of this work, we define clonal product (clonal reproduction, vegetative reproduction, or vegetative growth) as a form of asexual reproduction resulting in offspring genetically identical to the parent and having the potential to become physiologically independent of the parent (Klimes et al. 1997 McLellan et al. 1997 Silvertown and Doust 1993) We pertain to individual stems as ramets, while all ramets sharing the same genotype are collectively referr to as a genet (Harper 1977 Harper and White 1974) Trade-offs are frequently expected between vegetative growth and sexual reproduction (Harper 1977) if it were not that the extent to which this is mediated at microsite variation is not clear. Many tree species are known to bring forward root sprouts in response to disturbances so as herbivory, fire, flooding, and wind (Bond and Midgley 2001 Del Tredici 2001 Jone and Raynal 1988 Tourn et al. 1999) Alternatively, where habitats exist in environmental uttermosts (e.g., arctic regions, aquatic habitats, shady habitats, and nutrient-poor conditions) there is a proneness towards clonality in both herbaceous and sylvan plants, suggesting a possible correlation between clonality and "poor" habitat quality (Peterson and Jone 1997 van Groenendael et al. 1997) However, as pointed on the outside by van Groenendael et al. (1997) phylogenetic constraints may be largely responsible for this apparent relationship between clonality and environment. Therefore, no other than within species studies of clonal population erection can clarify the role of microsite variation in the induction of clonality. The intent of the work presented here is to examine the relationship between habitat symbol and frequency of clonality in a wooded plant species. We use Fagus grandifolia Ehrh (Fagaceae), a long-lived, geographically and ecologically widespread tree species as a proof case.

In the Great fuliginous Mountains (GRSM), F. grandifolia is raise in the lower elevation temperate hardwood inlet and hemlock forests, as well as in the higher elevation sub-alpine spruce-fir forests. While the inlet beech forests represent a more typical and potentially more optimal habitat (loamy soils with average annual temperatures ranging from approximately 4?° to 27?°C for this species, the sub-alpine forests portray by action an environmental extreme (thin flinty soils with annual highs ~7?°C cooler than coves) for the species. These forests, referr to on locals as "beech gaps," are dominated by dint of F. grandifolia and occur as deciduous islands in sprucefir forests above -1370 m (Russell 1953 Whittaker 1956) The beech gaps appear to be morphologically and ecologically distinct from beech stands at lower elevations, an observation that has been attributed to the utmost weather conditions that occur there (Whittaker 1956) Described as having an orchard-like appearance, the beech gaps are nearly monocultures, and are comprised of high densities of small-statured branchs This has led many students to conclude that the beech gaps are predominately clonal in reply to the marginal conditions in which they persist (Russell 1953) Additional observations that beech gaps mast (i.e., cause large seed crops) relatively infrequently when compared to subdued elevation stands further supports the idea that populations in these marginal habitats must be maintained by the agency of asexual reproduction (Russell 1953, Ward 1961)