Close Relationship between Mexican and Chinese Magnolia (Subtropical Disjunct of Magnoliaceae) Inferred from Molecular and Floral Scent Analyses

Hiroshi Azuma¹, Victor Rico-Gray², Jose G. Garcia-Franco², Masao Toyota³, Yoshinori Asakawa³ and Leonard B. Thien⁴

¹ Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan; ² Departamento de Ecologia Vegetal, Instituto de Ecologia, A. C., Apdo. 63, Xalapa, Veracruz 91000, Mexico; ³ Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima 770-8514, Japan; ⁴ Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA

The floral scents of Magnolia coco (distributed in Asia) and M. mexicana (New World), plus two Mexican Magnolia taxa, M. schiedeana and M. dealbata, were analyzed using GC-MS. A molecular phylogenetic analysis was also conducted using a combined data set of plastid DNA sequences obtained from GenBank to construct a well-resolved phylogenetic tree. The analysis indicated a sister relationship between subtropical-tropical Asian and American disjunct groups (including M. coco and M. mexicana) which was not shown in previous studies. Entire flowers and floral parts (sepals, petals, and gynoecia) of Magnolia coco emitted methyl 2-methylbutanoate (83-96%), whereas entire flowers of M. mexicana emitted a-farnesene (67%) which was mainly emitted from the sepals. The petals and gynoecium of M. mexicana emitted methyl 2-methylbutanoate as the main component with relatively small amount of a-farnesene. The common presence of methyl 2-methylbutanoate in the petals and gynoecium of both taxa may represent an ancestral scent profile because subtropical-tropical disjunct groups, which include M. coco in one and M. mexicana in the other, phylogenetically show a sister relationship. The floral scent of Magnolia schiedeana was exclusively composed of monoterpenes, especially geranyl methyl ether (87%). The floral scent of Magnolia dealbata was predominantly composed of benzenoids, especially 2-phenylethanol (78%) and methyl phenylacetate (13%).

¹ Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan; ² Research Institute for Development, BP A5, Noumea, New Caledonia, France

Asarum maculatum Nakai, a perennial herb endemic to southern Korea, is unique in its variegated leaves. However, the independence of this species is doubtful because the species co-occurs with A. sieboldii Miq. var. sieboldii in the same geographical area in Korea, and no significant difference is found between the two taxa in external morphology, except for leaf variegation. We examined the genetic differentiation between A. maculatum and A. sieboldii var. sieboldii using enzyme electrophoresis. The genetic differentiation between the two taxa in the same locality was not greater than that among the intraspecific populations. Moreover, there is little genetic differentiation between the mixed populations of the two taxa and the populations composed only of A. sieboldii var. sieboldii. Consequently, A. maculatum is not differentiated genetically from A. sieboldii var. sieboldii, and the two taxa should be regarded as the same species. Hence, a new combination, A. sieboldii f. maculatum (Nakai) Yamaji (comb. et stat. nov.), is proposed.

Key words: Aristolochiaceae, Asarum maculatum, A. sieboldii var. sieboldii, enzyme electrophoresis, genetic distance, Korea, taxonomic status, variegated leaf

New localities of Canavalia rosea were found on Okinawa and in the Amami Islands of the Ryukyu Archipelago. The locality on Amami-Oshima marks the northern-most limit of the species in Asia and extends its range approximately 490 km northeastward. At its newly discovered locations, C. rosea is pollinated by female leaf cutter bees and bears fruit. We suspect that the presence of three closely related species of Canavalia with flowers morphologically similar to those of C. rosea is probably one of the main reasons for the visitation by leaf cutter bees to C. rosea in the Ryukyu Archipelago. The female bees exhibited two patterns of behavior during flower visitations and effectively pollinated the flowers of C. rosea only when collecting both pollen and nectar. Pollinators of C. rosea have been reported as being anthopholid bees elsewhere, but are leaf cutter bees in the Ryukyu Archipelago.

Key words: Canavalia rosea, leaf cutter bees, new distribution, pollinators, Ryukyu Archipelago


Short Communication

Chromosome numbers for three taxa of Saussurea DC. from the Nepal Himalaya are reported here for the first time: S. nepalensis Spreng., S. taraxacifolia (Royle) DC. var. glabrescens K. Fujikawa & H. Ohba and S. wernerioides Sch. Bip. ex Hook. f. were all found to be diploid with 2n=32. Material of S. obvallata (DC.) Edgeworth, also collected from Nepal, yielded counts of 2n=32, corroborating previous reports for the species in other parts of its range.

Keywords: chromosome number, Nepal Himalaya, Saussurea