Incongruence among mitochondrial, chloroplast and nuclear gene trees in Pinus subgenus Strobus (Pinaceae).

Introgression has been considered to be one of main factors leading to phylogenetic incongruence among different datasets at lower taxonomic levels. In the plants of Pinaceae, the mtDNA, cpDNA, and nuclear DNA (nrDNA) may have different evolutionary histories through introgression because they are inherited maternally, paternally and biparentally, respectively. We compared mtDNA, cpDNA, and two low-copy nrDNA phylogenetic trees in the genus Pinus subgenus Strobus, in order to detect unknown past introgression events in this group. nrDNA trees were mostly congruent with the cpDNA tree, and supported the recent sectional and subsectional classification system. In contrast, mtDNA trees split the members of sect. Quinquefoliae into two groups that were not observed in the other gene trees. The factors constituting incongruence may be divided into the following two categories: the different splits within subsect. Strobus, and the non-monophyly of subsect. Gerardianae. The former was hypothesized to have been caused by the past introgression of cpDNA, mtDNA or both between Eurasian and North American species through Beringia. The latter was likely caused by the chimeric structure of the mtDNA sequence of P. bungeana, which might have originated through past hybridization, or through a horizontal transfer event and subsequent recombination.

Discovery of novel halogenated polycyclic aromatic hydrocarbons in urban particulate matters: occurrence, photostability, and AhR activity.

Halogenated aromatic compounds (HACs) in the environment have created great concern because of the associated adverse health implications. In this study we investigated the atmospheric behavior and exposure risk of brominated polycyclic aromatic hydrocarbons (BrPAHs) larger than three rings which were associated with particles in the urban air in Japan, and which were discovered as novel HACs in the air. Furthermore, the ambient levels of chlorinated polycyclic aromatic hydrocarbons (CIPAHs) and PAHs, in addition to BrPAHs, were also simultaneously investigated to emphasize the differences. Seven of 11 target BrPAHs were newly detected from the urban air samples in Japan between 2004 and 2005. Of the BrPAHs detected, 5,7-Br2BaA was most abundant (mean concentration, 8.7 pg m(-3)), followed by 7,12-Br2BaA (6.3 pg m(-3)) and 6-BrBaP (3.3 pg m(-3)). The mean concentrations of total BrPAHs, CIPAHs, and PAHs detected were 8.6 pg m(-3), 15.2 pg m(-3), and 1.2 ng m(-3), respectively, which showed that concentrations of such halogenated PAHs (Br-/Cl-PAHs) tended to be approximately 100-fold lower than PAHs. The BrPAHs had photolysis rates that were relatively faster than the corresponding CIPAHs. Comparing the ambient profiles among the PAH congeners suggested that ambient BrPAHs that came from the specific local emission sources differed from CIPAHs and PAHs, and/or could be driven by various seasonal factors, including photodecay processes. Most of the BrPAHs used showed inherent AhR-mediated activities. Toxic equivalents based on the relative potencies of each AhR activity and the ambient concentrations showed that either BrPAHs or CIPAHs accounted for a smaller proportion (approximately 1%) of the total.