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Begonia is one of the largest angiosperm genera, containing over 1500 species. Some aspects of the distribution of biodiversity in the genus, such as the geographical restrictions of monophyletic groups, the rarity and morphological variability of widespread species, and a preponderance of narrow endemics, suggest that restricted gene flow may have been a factor in the formation of so many species. In order to investigate whether this inference based on large-scale patterns is supported by data at the population level, we examined the distribution of genetic variation within Begonia sutherlandii in the indigenous forests of Kwazulu-Natal, South Africa, using microsatellite markers. Despite the species being predominantly outbreeding, we found high and significant levels of population structure (standardized  = 0.896). Even within individual populations, there was evidence for clear differentiation of subpopulations. There is thus congruence in evolutionary patterns ranging from interspecific phylogeny, the distribution of individual species, to the levels of population differentiation. Despite this species-rich genus showing a pan-tropical distribution, these combined observations suggest that differentiation occurs over very local scales. Although strongly selected allelic variants can maintain species cohesion with only low levels of gene flow, we hypothesize that in Begonia, gene flow levels are often so low, that divergence in allopatry is likely to be a frequent occurrence, and the lack of widespread species may in part be attributable to a lack of a mechanism for holding them together. [ABSTRACT FROM AUTHOR] more...

The genus Euphrasia in Britain comprises a taxonomically complex group of self-compatible, morphologically similar, hemi-parasitic, annual plant species of high conservation importance. The 19 diploid and tetraploid taxa currently recognised show striking variation in flower size. The objective of this paper is to determine whether a relationship exists between flower size and breeding system within Euphrasia. Following a survey of flower size variation among the 19 taxa, seven diploid populations, encompassing a broad range of flower sizes, were selected for detailed study. Four nuclear microsatellite loci were used to estimate the inbreeding coefficient Fis within each population. Fis values varied from to 0.17-0.77 and showed a significant, negative correlation with flower size. These results are best explained as the consequence of variation in selfing rate among the Euphrasia populations, with selfing rate increasing as flower size decreases. The potential factors influencing breeding system evolution in Euphrasia are discussed, together with the role of autogamy in generating taxonomic complexity and facilitating lineage differentiation within the genus.Heredity (2005) 94, 44-51. doi:10.1038/sj.hdy.6800553 Published online 18 August 2004 [ABSTRACT FROM AUTHOR] more...

Abstract The attributes of codominance, reproducibility and high resolution have all contributed towards the current popularity of nuclear microsatellites as genetic markers in molecular ecological studies. One of their major drawbacks, however, is the development phase required to obtain working primers for a given study species. To facilitate project planning, we have reviewed the literature to quantify the workload involved in isolating nuclear microsatellites from plants. We highlight the attrition of loci at each stage in the process, and the average effort required to obtain 10 working microsatellite primer pairs. [ABSTRACT FROM AUTHOR] more...

Seven polymorphic microsatellite loci have been characterized for investigating population structure in the patchily distributed herb Begonia sutherlandii. Two loci (BSU3 and BSU4) exhibited population specific null alleles; primer redesign and allele sequencing for one of these loci showed two transition mutations in the original primer site. Two loci exhibited imperfect repeat polymorphisms due to single base pair indels in the flanking region (locus BSU6) and in the microsatellite region itself (BSU7). Transversion mutations were also found in the microsatellite region of locus BSU7. The remaining three loci amplified in all individuals tested and appeared to conform to a simple stepwise mutation pattern. [ABSTRACT FROM AUTHOR] more...

Six polymorphic microsatellite markers have been developed to examine population structure and outcrossing rates in the narrow-range endemic Begonia socotrana. Only two of the markers amplify products in its recently discovered sister species B. samhaensis. All of the loci amplify in winter-flowering Begonia hybrids derived from B. socotrana, revealing little polymorphism and demonstrating the narrow genetic base of the material used in their production. [ABSTRACT FROM AUTHOR] more...