Department of Environment and Genetics

The influence of population size and spatial isolation on contemporary gene flow by pollen and mating patterns in temperate forest trees are not well documented, although they are crucial factors in the life history of plant species. We analysed a small, isolated population and a large, continuous population of the insect-pollinated tree species Sorbus torminalis in two consecutive years. The species recently experienced increased habitat fragmentation due to altered forest management leading to forests with closed canopies. We estimated individual plant size, percentage of flowering trees, intensity of flowering, degree of fruiting and seed set per fruit, and we determined mating patterns, pollen flow distances and external gene flow in a genetic paternity analysis based on microsatellite markers. We found clear effects of small population size and spatial isolation in S. torminalis. Compared with the large, continuous population, the small and isolated population harboured a lower percentage of flowering trees, showed less intense flowering, lower fruiting, less developed seeds per fruit, increased selfing and received less immigrant pollen. However, the negative inbreeding coefficients (F IS ) of offspring indicated that this did not result in inbred seed at the population level. We also show that flowering, fruiting and pollen flow patterns varied among years, the latter being affected by the size of individuals. Though our study was unreplicated at the factor level (i.e. isolated vs non-isolated populations), it shows that small and spatially isolated populations of S. torminalis may also be genetically isolated, but that their progeny is not necessarily more inbred.

Distinct spatial genetic structure, as the result of various evolutionary and ecological processes, is a common feature of tree populations. The rare pioneer forest tree Sorbus torminalis occurs in scattered populations of low density and exhibits both clonal propagation and gametophytic self-incompatibility. Clonal reproduction can promote considerable spatial genetic structure and, together with a self-incompatibility system, may substantially reduce mating opportunities within S. torminalis populations, i.e. an Allee-effect owing to mate limitation. All 10 S. torminalis stands mapped in northern Switzerland and analysed with allozymes showed a considerable degree of clonal reproduction, but they were also characterised by large numbers of genotypes that occurred only once. However, spatial autocorrelation analysis revealed significant spatial genetic structure at distances between 15 and 30 m as the result of clonal reproduction. Once the effect of clonal propagation was removed from the analysis, the stands no longer exhibited significant spatial autocorrelation. This implies that seed dispersal was not locally restricted. The degree of clonal reproduction was neither correlated with population size, nor did smaller populations exhibit less genetic diversity. Because clonal patches were rather small and interspersed with other genetically unique and unrelated individuals, clonal reproduction seemed to have no negative impact on the species' sexual reproduction. It is thus likely that the combination of an effective self-incompatibility system and high interstand gene flow helps to maintain genetic diversity in S. torminalis stands, while clonal propagation preserves the genetic diversity over time even if environmental conditions become less favourable during the course of succession. #

Mating system parameters and genetic diversity were examined for ®ve populations of the endangered shrub Grevillea iaspicula (Proteaceae). Controlled pollinations show that G. iaspicula has an eective self-incompatibility system and little potential for agamospermy. This is re¯ected in uniformly high multilocus outcrossing rates (t m 0.96±1.00). However, average paternal diversity within openpollinated sibships is low (r p 0.31±0.54), suggesting that mating within populations is quite restricted. Despite the small size of most populations (four of the ®ve populations studied have fewer than 20 reproductive individuals) the species still possesses moderate to high allelic richness (A 1.6±2.5). Interpopulation genetic dierentiation is high (D 0.04±0.32), suggesting that genē ow is limited, even among populations separated by only a few kilometres.

Here we describe our research aimed at developing technologies to control sexual reproduction in the cruciferous species wild radish (Raphanus raphanistrum Linnaeus), a major weed of grain crops that is subject to recurrent evolution of herbicide resistance. By acting selectively on either wild radish's self-incompatibility mechanism or on its ability to produce and disseminate viable male gametes and set seeds, these technologies should provide alternative control methods to herbicides that will be highly selective and not affect the surrounding crop.

Here we describe our research aimed at developing control technologies that target sexual reproduction in weeds. The technologies we propose developing should differentiate between weeds and the surrounding crop by acting selectively on one of two aspects of plant reproduction: selfincompatibility and the production of viable male gametes. The cruciferous weed wild radish is the main target for our research because of its importance as a weed and because of its close taxonomic relationship to the widely used model species, Arabidopsis thaliana and Brassica oleracea.

A morphometric study of the Olearia phlogopappa species complex from throughout south-eastern Australia has confirmed species boundaries and resolved the infraspecific taxonomy of two species. It has shown O. phlogopappa (Labill.) DC., O. stellulata (Labill.) DC., O. lirata (Sims) Hutch., O. rugosa (F.Muell. ex W.Archer bis) Hutch. and O. brevipedunculata N.G.Walsh to be non-overlapping entities with unique morphological characters. O. stellulata is circumscribed to include only southern and western Tasmanian populations and those from the Otways and Wilsons Promontory in southern Victoria. O. rugosa is restricted to Victoria and a few isolated populations on Flinders Island and northern Tasmania. Four previously noted variants of O. rugosa from Victoria are here described as subspecies, along with the description of a fifth subspecies from northern Tasmania. Infraspecific boundaries of O. phlogopappa are here revised to include nine subspecies, six of which were previously included...

Small populations of self-incompatible plants are assumed to be threatened by a limitation of compatible mating partners due to low genetic diversity at the self-incompatibility (S) locus. In contrast, we show by using a PCR-RFLP approach for S-genotype identification that 15 small populations (N = 8-88) of the rare wild pear (Pyrus pyraster) displayed no mate limitation. S-allele diversity within populations was high (N = 9-21) as was mate availability (92.9-100%). Although population size and S-allele diversity were strongly related, no relationship was found between population size and mate availability, gene diversity (H e), or fixation index (F IS), based on five neutral microsatellite loci. As we determined the principal mate availability within populations based on the S-genotypes observed, the realized mate availability under natural conditions may differ from our estimates, for example, due to spatially limited pollen dispersal. We therefore urge studies on self-incompatible plants to proceed from the simple assessment of principal mate availability to the determination of realized mate availability in natural populations.

The relationship between seed size and fitness in plants may depend on offspring density, especially in cases where seed size affects the outcome of competition. We investigated the relationship between seed mass, germination, intraspecific competition and seedling height in a glasshouse experiment on three European white oak species (Quercus robur, Q. petraea, Q. pubescens). Within offspring families, seed mass showed a moderate, but statistically significant effect on seedling height, i.e. seedlings from heavier seeds were slightly taller. In contrast, competition caused pronounced inequality in seedling height in pairs of competing seedlings, but in only 55.2% of all pairs the dominant competitor arose from the heavier seed. It is thus possible that a positive effect of seed mass on seedling growth can be mediated through the density of conspecific seedlings and that heterogeneity in offspring density will contribute to the maintenance of seed mass variation in oak populations.

Many lichen species produce both sexual and asexual propagules, but, aside from being minute, these diaspores lack special adaptations for long-distance dispersal. So far, molecular studies have not directly addressed isolation and genetic differentiation of lichen populations, both being affected by gene flow, at a regional scale. We used six mycobiontspecific microsatellite loci to investigate the population genetic structure of the epiphytic lichen Lobaria pulmonaria in two regions that strongly differed with respect to anthropogenic impact. In British Columbia, L. pulmonaria grows in continuous old-growth forests, while its populations in the old cultural landscape of Switzerland are comparably small and fragmented. Populations from both British Columbia and Switzerland were genetically diverse at the loci. Geographically restricted alleles, low historical gene flow, and analyses of genetic distance (UPGMA tree) and of differentiation (AMOVA) indicated that populations from Vancouver Island and from the Canadian mainland were separated from each other, except for one, geographically intermediate population. This differentiation was attributed to different glacial and postglacial histories of coastal and inland populations in British Columbia. In contrast to expectations, the three investigated Swiss populations were genetically neither isolated nor differentiated from each other despite the long-lasting negative human impact on the lichen's range size in Central Europe. We propose that detailed studies integrating local landscape and regional scales are now needed to understand the processes of dispersal and gene flow in lichens.

Genetically controlled self-incompatibility systems represent links between genetic diversity and plant demography with the potential to directly impact on population dynamics. We use an individual-based spatial simulation to investigate the demographic and genetic consequences of different self-incompatibility systems for plants that vary in reproductive capacity and lifespan. The results support the idea that, in the absence of inbreeding effects, populations of self-incompatible species will often be smaller and less viable than self-compatible species, particularly for shorter-lived organisms or where potential fecundity is low. At high ovule production and low mortality, self-incompatible and self-compatible species are demographically similar, thus self-incompatibility does not automatically lead to reduced mate availability or population viability. Overall, sporophytic codominant self-incompatibility was more limiting than gametophytic or sporophytic dominant systems, which g...

Advances in high‐throughput, comprehensive small molecule analytical techniques have seen the development of the field of metabolomics. The coupling of mass spectrometry with high‐resolution chromatography provides extensive chemical profiles from complex biological extracts. These profiles include thousands of compounds linked to gene expression, and can be used as taxonomic characters. Studies have shown metabolite profiles to be taxon specific in a range of organisms, but few have investigated taxonomically problematic plant taxa. This study used a phenetic analysis of metabolite profiles to test taxonomic boundaries in the Olearia phlogopappa (Asteraceae) complex as delimited by morphological data. Metabolite profiles were generated from both field‐ and shade hous‐egrown material, using liquid chromatography‐mass spectrometry (LC‐MS). Aligned profiles of 51 samples from 12 taxa gave a final dataset of over 10,000 features. Multivariate analyses of field and shade house material ...

Recent molecular work on Olearia s.l. has not supported current generic or sectional concepts, instead identifying two major lineages loosely based on distribution. Further work is required to adequately circumscribe Olearia s.s. The present study aimed to determine the monophyly of Australian stellate-haired species of Olearia. Using four molecular regions (ITS, psbA–trnH, rpl32–trnL and matK) sequenced from 27 species, Australian stellate-haired taxa were confirmed as monophyletic. Accordingly, Olearia section Asterotriche is redefined here to include only Australian species. This section is one of the few confirmed natural groups in Olearia. Section Asterotriche is closely associated with, but does not include, the type species of Olearia, O. tomentosa (J.C.Wendl.) DC. Given this close association to the type, section Asterotriche should be retained within Olearia, pending further research that would justify any future changes. This manuscript concludes with a monograph of sectio...