Polypleurum wallichii, (R.Br. ex Griff.) Warm

Kato, Masahiro, Werukamkul, Petcharat, Won, Hyosig & Koi, Satoshi, 2019, Paraphyletic Species of Podostemaceae: Cladopus fallax and Polypleurum wallichii, Phytotaxa 401 (1), pp. 33-48 : 38-40

Polypleurum wallichii

In the Polypleurum wallichii group, P. stylosum differs from P. wallichii in the root habit, the length and width of the root and the length of the pedicel and stalk of the capsule, although the ranges of variation in the characters are similar ( Table 3 ; Fig. 4 ). Polypleurum elongatum (Gardner) J.B.Hall differs from the two species by the root being long, adhering only at the base and floating nearly its full length. Polypleurum schmidtianum differs from P. wallichii in one stamen (versus 2) and indistinctly in the root being relatively short and narrow and adhered to the rock for its full length, the pedicel short, in which the ranges of variations overlap to some extents.

In the matK phylogenetic tree ( Fig. 1 ), Polypleurum wallichii , P. stylosum , P. elongatum and P. schmidtianum were monophyletic and sister to P. munnarense Nagendran & Arekal , although the relationships within the clade were not well resolved. Polypleurum wallichii was divided into three subgroups. Polypleurum wallichii -1 and P. wallichii - 3 with P. stylosum KI-109 each were robustly monophyletic, whereas P. wallichii -2 was an unresolved subgroup. Polypleurum wallichii -2 was defined by its distribution in Laos and Thailand (while P. wallichii -1 and 3 occur in Cambodia and India, respectively). The three subgroups were morphologically variable and inseparable ( Table 3 ).

Polypleurum wallichii -1 (from one site in Cambodia [Koh Kong Province]) was sister to P. schmidtianum ( Fig. 1 ). Geographically, the P. wallichii -1 plants (CAM-03, CAM-11) were sympatric with CAM-05 and CAM-12 of P. schmidtianum , and they grew in adjacent subpopulations in the same habitat. Polypleurum wallichii -2 comprised specimens from eastern and central Thailand and northern central Laos. Polypleurum wallichii -3 comprised specimens from Meghalaya, northeastern India, and had the same sequences as southern Indian KI-109. Polypleurum stylosum (specimens of which were collected from southern India and Sri Lanka) was also not monophyletic and divided into several subclades, of which Cu-90003, IND-1401 and IND-1413 were monophyletic, with low support, with P. wallichii -3 and KI-109 of P. stylosum , and as well as P. elongatum .

The relationships deduced from the ITS sequences,like the matK tree, showed that P.wallichii -1 and P.schmidtianum were monophyletic ( Fig. 2 ). This P. wallichii -1 clade, P. wallichii -2 and P. wallichii -3 were separated from each other. As a whole, P. schmidtianum , P. stylosum and P. wallichii , together with P. munnarense and Hydrobryopsis sessilis (Willis) Engl. , formed an unresolved complex.

In the combined matK and ITS tree, P. wallichii -1 and P. schmidtianum were monophyletic ( Fig. 3 ). The clade was sister to P. wallichii -2 and both were sister to P. wallichii -3.

Figures

FIGURE 1. Bayes phylogenetic consensus tree deduced from matK sequences.Numbers above and below branches are Bayesian posterior probabilities (≥0.80) and bootstrap values (≥50 %) of ML (left) and MP (right), respectively. Single asterisk (*) indicates that specimen JK- Manose is followed by additional specimens with the same sequence, JK-02, JK-Yamazaki, JK-Anraku, JP-127, JK-Mawatari, and CH-02. Double asterisk (**) indicates that specimen CP-07 is followed by additional specimens with the same sequence, CP-22, 24, 27, and 29. For simplicity, species of Hanseniella, Hydrobryum, Hydrodiscus and Thawatchaia examined are united as a single clade (for materials see Appendix). The tree is rooted on a branch between a clade of Cladopus, Hanseniella, Hydrobryum, Hydrodiscus, Paracladopus and Thawatchaia, and a clade of Polypleurum, Griffithella, Hydrobryopsis, Willisia and Zeylanidium.

FIGURE 2. Bayes phylogenetic consensus tree deduced from ITS sequences. Numbers above and below branches are Bayesian posterior probabilities (≥0.80) and bootstrap values (≥50 %) of ML (left) and MP (right), respectively. For simplicity, species of Hydrobryum examined are united as ‘Hydrobryum species’ (see Appendix). The tree is rooted on a branch between a clade of Cladopus, Hanseniella and Hydrobryum and a clade of Polypleurum, Griffithella, Hydrobryopsis, Willisia and Zeylanidium.

FIGURE 3. Bayes phylogenetic consensus tree deduced from concatenated matK and ITS sequences. Numbers above and below branches are Bayesian posterior probabilities (≥0.80) and bootstrap values (≥50 %) of ML (left) and MP (right), respectively. For simplicity, the species of Hydrobryum, both matK and ITS sequences of which were examined, are united as ‘Hydrobryum species’ (Appendix). C. fallax CAM-13a = LC380594 + LC380635; C. fallax CAM-13b = LC380594 + LC380636; C. fallax CAM-13c = LC380594 + LC380637; C. fallax CAM-19a = LC380595 + LC380638; C. fallax CAM-19b = LC380595 + LC380639; C. taiensis CAM-14a = LC380602 + LC380643; C. fallax CAM-14b = LC380602 + LC380644. The tree is rooted on a branch between a clade of Cladopus, Hanseniella and Hydrobryum, and Polypleurum.

FIGURE 4. Root habits of Polypleurum. Roots are reproductive (with flowers or fruits borne on flanks, indicating root habit; vegetative in A) and exposed in the dry season.A, B, E, F, adhering roots (W type); C, D, floating roots (S type).A−C. P. wallichii (A = P. wallichii-2, Khao Yai National Park, Thailand; B = P. wallichii-3, Meghalaya, India; C = P. wallichii-1, Koh Kong, Cambodia). D, E. P. stylosum (D, E, Kerala, India). F. Dried-up root remains of P. schmidtianum (at top, light brown) with those of Cladopus fallax (at bottom and right, white gray) in Koh Kong, Cambodia.