Helonias (Tanaka, 1998)

Tanaka, Noriyuki, 2019, Taxonomy, evolution and phylogeography of the genus Helonias (Melanthiaceae) revisited, Phytotaxa 390 (1), pp. 448-450 : 448-450

2. Helonias as a genus including Heloniopsis and Ypsilandra

The members of Helonias , including Heloniopsis and Ypsilandra , are basically similar not only in habit but also in various characters such as the shape of the vegetative organs, floral structure ( Utech 1978, Utech & Kawano 1981, Tanaka 1997a, b), pollen ultrastructure ( Takahashi & Kawano 1989), capsular structure and dehiscence, seed morphology ( Tanaka 1997c), and chromosome number ( Utech 1980). Besides these features, they also share an ecological preference basically similar to one another. For instance, both the Asian and North American members inhabit mostly temperate regions at similar latitudes ( Fig. 31 ) with moderate precipitation and temperature and prefer swampy or moist habitats. Their life history or seasonal growth patterns are also alike. As stated earlier, plastid DNA sequence data also support the monophyly of Helonias (s.lat.) ( Fuse & Tamura 2000, 2016, Fuse et al. 2004, Givnish et al. 2016, Kim et al. 2016). Further, the data from cladistics analyses of phenotypic characters indicate paraphyly for both Helonias (s.str.) and Ypsilandra ( Tanaka 1997e) .

It is true that Helonias here circumscribed is not a little diversified, but considering the similarity in various characters of the members, the genus as a whole appears fairly uniform and is monophyletic ( Fig. 30 ; Tanaka 1997e, Fuse & Tamura 2000, 2016, Fuse et al. 2004, Givnish et al. 2016, Kim et al. 2016). The degree of infrageneric diversity within Helonias appears much smaller than the intergeneric difference between Helonias and closely allied Chamaelirium s.lat. (including Chionographis Maxim., Tanaka 2017b ). The generic delimitation of Helonias incorporating Ypsilandra and Heloniopsis proposed previously by Tanaka (1998a) is therefore followed in this paper.

3. Conspectus of a new infrageneric system for Helonias

From the results of this study a new classification system for Helonias is proposed ( Table 3). More concrete, detailed taxonomic treatments are given in the following section (4).

4. Taxonomic treatment

Melanthiaceae , tribe Heloniadeae Reichenbach (1828: 63 , as Helonieae).

Figures

FIGURE 30. Phylogram of 12 species of Helonias constructed from analyses of phenotypical characters. Each lineage is numbered 1 to 24. Infrageneric categories, A to C, are shown as vertical lines on right corner. Character states regarded as apomorphies acquired by respective lineages are enumerated in List 2.

FIGURE 31. Geographic ranges of two sections Helonias and Heloniopsis. Ancestral plants of Helonias are presumed to have been in northern high latitudes approximate area of which is encircled with broken line.They are supposed to have been separated into two groups, and eventually one group reached eastern N. America and the other eastern Asia as consequence of their southward migrations (A). ① Sect. Helonias. ②–④ Sect. Heloniopsis. ② Subsect. Ypsilandra. ③ Subsect. Heloniopsis ser. Umbellatae. ④ Subsect. Heloniopsis ser. Heloniopsis. For historical aspect of range extension, see also Figs. 32, 33 and text (Part III).