Pollen hosts of western palaearctic bees of the genus Colletes (Hymenoptera: Colletidae): the Asteraceae paradox

To assess the pollen hosts of 60 western palaearctic bee species of the genus Colletes (Colletidae), we microscopically analysed 1336 pollen loads of collected females. Twenty‐six species (43.3%) were found to be specialized at the level of plant family, subfamily or genus. Thirty‐four species (56.7%) proved to be pollen generalists to varying degrees, visiting the flowers of up to 15 different plant families. Flowers of the subfamily Asteroideae (Asteraceae) are by far the most important pollen source, contributing 23.6% to the pollen‐plant spectrum of the whole bee genus. The high significance of Asteroideae pollen is due to the large number of specialists: 14 Colletes species belonging to four different taxonomic groups harvest pollen exclusively or predominantly on flowers of the Asteroideae. By striking contrast, Asteroideae pollen plays only a marginal role in the diets of the pollen generalists: it was recorded in only 2.7% of the pollen loads and in seven out of the 34 pollen generalists. Among the few generalists exploiting Asteroideae for pollen, three closely related species have ancestors which were possibly specialized on Asteraceae. The pattern of use of Asteroideae pollen by the Colletes bees supports recent findings that this pollen possesses unfavourable or protective properties, which render its digestion difficult, and suggests that bees need physiological adaptations to successfully utilize it. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 719–733.     

利用低拷贝核基因重建菊科紫菀亚科族间系统发育关系

紫菀亚科(Asteroideae)是菊科最大的一个亚科, 包含的种数多于被子植物的绝大多数科。目前, 紫菀亚科族间的系统发育关系主要依赖于叶绿体基因信息, 但是叶绿体基因为单亲遗传, 并不能完整反映进化历史。鉴于杂交现象在菊科普遍存在, 故利用核基因可以反映更完整的紫菀亚科进化历史。该研究首次使用从转录组数据(20个新测+11个从NCBI数据库下载)中筛选出的47个直系同源低拷贝核基因来研究紫菀亚科的系统发育关系, 共选取了29个物种, 代表了紫菀亚科20个族中的13个族。用超矩阵分析方法和溯祖推测分析方法各获得了1个稳定的紫菀亚科系统树, 每个树上绝大多数分支都得到了高度支持, 且2个树之间没有明显的冲突。新的紫菀亚科族间系统发育关系揭示了千里光超族应并入紫菀超族, 春黄菊族可能是千里光族与紫菀族杂交起源的, 金鸡菊族很可能也是杂交起源的。该研究结果显示低拷贝核基因可以更好地解决科以下分类阶元的系统发育关系, 对菊科乃至被子植物其它科的系统发育研究具有重要的借鉴意义。     

Comparative plastome analysis of Blumea,with implications for genome evolution and phylogeny of Asteroideae

The genus Blumea (Asteroideae, Asteraceae) comprises about 100 species, including herbs, shrubs, and small trees. Previous studies have been unable to resolve taxonomic issues and the phylogeny of the genus Blumea due to the low polymorphism of molecular markers. Therefore, suitable polymorphic regions need to be identified. Here, we de novo assembled plastomes of the three Blumea species B. oxyodonta, B. tenella, and B. balsamifera and compared them with 26 other species of Asteroideae after correction of annotations. These species have quadripartite plastomes with similar gene content, genome organization, and inverted repeat contraction and expansion comprising 113 genes, including 80 protein‐coding, 29 transfer RNA, and 4 ribosomal RNA genes. The comparative analysis of codon usage, amino acid frequency, microsatellite repeats, oligonucleotide repeats, and transition and transversion substitutions has revealed high resemblance among the newly assembled species of Blumea. We identified 10 highly polymorphic regions with nucleotide diversity above 0.02, including rps16‐trnQ, ycf1, ndhF‐rpl32, petN‐psbM, and rpl32‐trnL, and they may be suitable for the development of robust, authentic, and cost‐effective markers for barcoding and inference of the phylogeny of the genus Blumea. Among these highly polymorphic regions, five regions also co‐occurred with oligonucleotide repeats and support use of repeats as a proxy for the identification of polymorphic loci. The phylogenetic analysis revealed a close relationship between Blumea and Pluchea within the tribe Inuleae. At tribe level, our phylogeny supports a sister relationship between Astereae and Anthemideae rooted as Gnaphalieae, Calenduleae, and Senecioneae. These results are contradictory to recent studies which reported a sister relationship between “Senecioneae and Anthemideae” and “Astereae and Gnaphalieae” or a sister relationship between Astereae and Gnaphalieae rooted as Calenduleae, Anthemideae, and then Senecioneae using nuclear genome sequences. The conflicting phylogenetic signals observed at the tribal level between plastidt and nuclear genome data require further investigation.     

Eight new species of Marasmodes (Asteraceae,Anthemideae) from South Africa

During a stay at the Kirstenbosch Research Centre in Cape Town (South Africa), several groups of Asteraceae were studied. One of these was the genus Marasmodes (tribe Anthemideae). After a careful taxonomic study of additional material, including the first species described by A. P. de Candolle, the author has concluded that eight collections should be considered as new species. These new species are described and their relationships with the most similar species of the genus are discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 330–342.