The mating system and genetic structure in a perennial grass, Cynosurus cristatus L.

The genetic control and small scale spatial distributions of three conspicuous genetic polymorphisms-presence or absence of corolla spotting, yellow or white corolla colour, and presence or absence of stem waxiness-were studied in populations of the plant species Impati ens pallida and I. capensis occurring in Québec, Canada. The corolla spotting and colour morphs in I. pallida each appear to be determined by different pairs of unlinked loci. Dominant alleles at each locus pair are required for the expression of corolla spotting or yellow corolla colouration. Stem waxiness in I. capensis is also shown to be under genetic control. Significant clustering of identical flower and stem phenotypes at small interplant distances was observed in most population samples, suggesting substructuring of genotypes in space. The sizes of patches where morph frequencies occurred in excess of random expectations were found to be consistent among populations and polymorphisms within the species, lending support to the interpretation that substructuring of genetic variation in these populations is due to restricted gene dispersal. The population genetical consequences of limited gene flow in these species is discussed.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatial autocorrelation of genotypes in populations of Impatiens pallida and Impatiens capensis

Schoen

Latta

1989

“…Interactions between population structure and the mating system have been investigated in several experimental (Ennos andClegg, 1982, 1985;Ellstrand and Foster, 1983) and natural plant populations (Brown eta!., 1975;Linhart et al, 1981;Shaw and Allard, 1981;Neale and Adams, 1985;Ritland and Ganders, 1985;Shea, 1987).…”

Section: Introductionmentioning

confidence: 99%

The mating system and population genetic structure in a bird-pollinated mallee, Eucalyptus rhodantha

Sampson

Hopper²,

James

1989

The mating system and spatial genetic structure of the rare and endangered bird-pollinated mallee Eucalyptus rhodantha were investigated in a remnant stand, using progeny arrays and pollen assayed at four polymorphic allozyme loci. Comparisons of the genetic diversity within and between the pollen pools and maternal parents of two arbitrary subpopulations indicated the presence of spatial genetic heterogeneity which was not broken down by pollen flow. It was suggested that this is the result of a high level if inbreeding and limited pollen dispersal by birds. Estimates of outcrossing rate ranged between I = 0-59 and I = 0-67 and were at the low end of the range reported for other eucalypts. It was concluded that E. rhodantha has a mixed mating system with a significant proportion of selfpollination. Biparental inbreeding within small neighbourhoods probably also contributed to the high level of inbreeding. The low level of outcrossing observed in E.rhodantha was not consistent with the hypothesis that bird pollination leads to high levels of outcrossing in the Australian flora. However, the level of outcrossing achieved through bird pollination together with high levels of gene flow between populations contribute to the maintenance of the relatively high levels of diversity which characterise the dissected populations of this species.

“…Most measurements come from crop populations (e.g., Handel, 1982Handel, , 1983Levin, 1984;Levin and Kerster, 1974), some from natural species or situations (e.g., Schaal, 1975Schaal, , 1980Levin, 1981;Ennos and Clegg, 1982;Bos et a!., 1985;Ennos, 1985). The genetic variability of plant characters which influence the amount of gene flow between populations within a species, and which therefore may be of importance for the speed of evolution, is not well documented.…”

Section: Introductionmentioning

confidence: 99%

Gene flow in Plantago. II. Gene flow pattern and population structure. A simulation study

Bos

Vanderharing

1988

The relative effects of the pattern of pollen flow, pattern of seed dispersal, presence or absence of a selfincompatibility system and annual versus perennial life cycle on hoiuozygosity and the evolution of population structure in a plant species were studied using computer simulation. Starting with a random distribution of genotypes at a diallelic marker locus in populations of 2500 individuals, simulations were run for the equivalent of 100 or 400 years. Sixteen different situations were investigated, one of which corresponded to a species like Plantago lanceolata: a perennial herb with restricted seed dispersal, a gametophytic self-incompatibility system and a protogyny-growth syndrome. Regression analysis of fixation index values (F) showed that the presence of the protogyny-growth syndrome or self-incompatibility lowered the increase of homozygosity, while restricted seed dispersal and perenniality promoted inbreeding. Analysis of population structure demonstrated that the "patchiness" of a population after 100 generations was higher in a perennial species than in an annual, while the pollen flow pattern caused by the presence of the protogyny syndrome reduced the development of population structure.It appears that genetic structure within populations of a species like P. lanceolata can still be explained by restricted gene flow, in spite of the presence of outcrossing mechanisms like self-incompatibility and protogyny.