Comparative phylogeography of red maple (Acer rubrum L.) and silver maple (Acer saccharinum L.): impacts of habitat specialization, hybridization and glacial history

Aim We analysed variation in chloroplast DNA (cpDNA) in red maple (Acer rubrum L.) and silver maple (Acer saccharinum L.) across a large part of their geographic ranges. Acer rubrum is one of the most common and morphologically variable deciduous trees of eastern North America, while its sister species A. saccharinum has a more restricted habitat distribution and displays markedly less morphological variation. Our objective was to infer the impact of biogeographic history on cpDNA diversity and phylogeographic structure in both species. Location Deciduous forests of eastern North America. Methods We sequenced 1289 to 1645 bp of non-coding cpDNA from A. rubrum (n = 258) and A. saccharinum (n = 83). Maximum parsimony networks and spatial analysis of molecular variance (SAMOVA) were used to analyse phylogeographic structure. Rarefaction analyses were used to compare genetic diversity. Results A total of 40 cpDNA haplotypes were recovered from A. rubrum (38 haplotypes) and A. saccharinum (7 haplotypes). Five of the seven A. saccharinum haplotypes were shared with nearby samples of A. rubrum. SAMOVA recovered four phylogeographic groups for A. rubrum in: (1) south-eastern USA, (2) the Gulf and south-eastern Coastal Plain, (3) the lower Mississippi River Valley, and (4) the central and northern regions of eastern North America. Acer saccharinum had significantly lower haplotype diversity than A. rubrum, and novel haplotypes in post-glaciated northern limits of its range were shared with A. rubrum. Main conclusions This is the first study of A. rubrum to report a distinct phylogeographic group centred on the lower Mississippi River, and the first to examine data comparatively with A. saccharinum. We hypothesized that A. rubrum would display stronger phylogeographic structure and greater haplotype diversity than A. saccharinum because of its greater geographic range, and ecological and morphological variation. This hypothesis was supported by the cpDNA analysis. The sharing of cpDNA and chloroplast simple sequence repeat (cpSSR) haplotypes in areas of geographic overlap provides evidence of introgression, which led to an increase in haplotype diversity in both species, and to novel phylogeographic structure in A. rubrum. We recommend that introgression be considered, along with other potential causes, as an explanation for the phylogeographic structure of cpDNA in plants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83505/1/Saeki2011maple.pdf8

Deciduous Trees and the Application of Universal DNA Barcodes: A Case Study on the Circumpolar Fraxinus

The utility of DNA barcoding for identifying representative specimens of the circumpolar tree genus Fraxinus (56 species) was investigated. We examined the genetic variability of several loci suggested in chloroplast DNA barcode protocols such as matK, rpoB, rpoC1 and trnH-psbA in a large worldwide sample of Fraxinus species. The chloroplast intergenic spacer rpl32-trnL was further assessed in search for a potentially variable and useful locus. The results of the study suggest that the proposed cpDNA loci, alone or in combination, cannot fully discriminate among species because of the generally low rates of substitution in the chloroplast genome of Fraxinus. The intergenic spacer trnH-psbA was the best performing locus, but genetic distance-based discrimination was moderately successful and only resulted in the separation of the samples at the subgenus level. Use of the BLAST approach was better than the neighbor-joining tree reconstruction method with pairwise Kimura's two-parameter rates of substitution, but allowed for the correct identification of only less than half of the species sampled. Such rates are substantially lower than the success rate required for a standardised barcoding approach. Consequently, the current cpDNA barcodes are inadequate to fully discriminate Fraxinus species. Given that a low rate of substitution is common among the plastid genomes of trees, the use of the plant cpDNA “universal” barcode may not be suitable for the safe identification of tree species below a generic or sectional level. Supplementary barcoding loci of the nuclear genome and alternative solutions are proposed and discussed

Monotropastrum humile var. humile is associated with diverse ectomycorrhizal Russulaceae fungi in Japanese forests

The original publication is available at www.springerlink.comArticleECOLOGICAL RESEARCH. 23(6):983-993(2008)journal articl

Chromosome number in Liquidambar

Volume: 74Start Page: 287End Page: 29