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We examined genetic differentiation among eight local populations of a metapopulation of Magnolia stellata using 10 nuclear and three chloroplast microsatellite (nSSR and cpSSR) markers and evaluated the influence of historical gene flow on population differentiation. The coefficient of genetic differentiation among populations for nSSR ([F.sub.ST] = 0.053) was less than half that for cpSSR (0.137). An isolation-by-distance pattern was detected for nSSRs, but not cpSSRs. These results suggest that pollen flow, as well as seed dispersal, has significantly reduced genetic differentiation among populations. We also examined patterns of contemporary pollen flow by paternity analysis of seeds from nine seed parents in one of the populations using the nSSR markers and found it to be greatly restricted by the distance between parents. Although most pollen flow occurred within the population, pollen flow from outside the population accounted for 2.5% of the total. When historical and contemporary pollen flows among populations were compared, the levels of pollen flow seem to have declined recently. We conclude that to conserve M. stellatta, it is important to preserve the whole population by maintaining its metapopulation structure and the gene flow among its populations. Key words: conservation: gene dispersal; genetic diversity; Japan; Magnolia tomentosa: metapopulation; simple sequence repeat; star magnolia.

Abstract: Flowering phenology is critical for reproduction in dioecious species, but selection on timing of flowering may be weakened by physiological factors such as plant size, and external factors such [...]

Genetic diversity of Taxodium in the south-eastern United States is discussed based on study of differentiation using cleaved amplified polymorphic sequences (CAPS). The two taxa, bald cypress and pond cypress, are found in the area in overlapping ranges. Habitats seem to be different. Most of the genetic variation was found within populations with 4.9% between populations and 3.2% between taxa. The two taxa apparently should be considered varietals.

SUMMARY: Standard models of plant speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality in wind‐pollinated trees with long evolutionary histories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi‐copy, potentially multi‐locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra‐genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high‐throughput sequencing (HTS) of the 5S intergenic spacers (5S‐IGS) for a lineage of wind‐pollinated subtropical to temperate trees, the Fagus crenata – F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4963 unique 5S‐IGS variants reflect a complex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra‐genomic competition between two or more paralogous‐homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years. Significance Statement: The evolution of extra‐tropical wind‐pollinated tree genera involves dynamic speciation processes. High‐throughput sequencing of the multi‐copy, potentially multi‐locus 5S rDNA reveals a complex history of hybrid origins, lineage sorting and mixing, and intra‐genomic competition between paralogous‐homeologous loci in the core group of Eurasian beech trees (genus Fagus) and their distant relative, F. japonica. The modern species are genetic mosaics and represent a striking case of at least 55 million years of ongoing reticulate evolution. [ABSTRACT FROM AUTHOR]

Sex change affects the sex ratios of plant populations and may play an essential role in the evolutionary shift of sexual systems. Sex change can be a strategy for increasing fitness over the lifetime of a plant, and plant size, environmental factors, and growth rate may affect sex change. We described frequent, repeated sex changes following various patterns in a subdioecious Eurya japonica population over five successive years. Of the individuals, 27.5% changed their sex at least once, and these changes were unidirectional or bidirectional. The sex ratio (females/males/all hermaphrodite types) did not fluctuate over the 5 years. In our study plots, although the current sex ratio among the sexes appears to be stable, the change in sex ratio may be slowly progressing toward increasing females and decreasing males. Sex was more likely to change with higher growth rates and more exposure to light throughout the year. Among individuals that changed sex, those that were less exposed to light in the leafy season and had less diameter growth tended to shift from hermaphrodite to a single sex. Therefore, sex change in E. japonica seemed to be explained by a response to the internal physiological condition of an individual mediated by intrinsic and abiotic environmental factors. [ABSTRACT FROM AUTHOR]