Aeginetia acaulis (Roxb.) Walpers (1844: 481)

Nuraliev, Maxim S., Pham, Van The, Nguyen, Van Canh & Parnell, John A. N., 2023, Sorting out Aeginetia (Orobanchaceae) in Indochina: A. sessilis is a synonym of A. acaulis, Phytotaxa 597 (4), pp. 269-279 : 270-276

Aeginetia acaulis (Roxb.) Walpers (1844: 481)

( Fig. 1–4 )

Literature: — Reuter (1847: 43), Thwaites (1864: 221), Zhang & Tzvelev (1998: 241), Vu (2005: 246), Kumar et al. (2020a: 239).

Basionym: — Orobanche acaulis Roxburgh (1820: 89 , Plate 292). Roxburgh (1832: 28).

Homotypic synonym: — Aeginetia pedunculata var. acaulis (Roxb.) Beck-Mannagetta (1930: 21) .

LECTOTYPE (designated here):—Plate 292 in Plants of the coast of Coromandel Vol. 3 by Roxburgh (1820: Plate 292) .

Heterotypic synonyms:

Orobanche acaulis Roxburgh (1814: 45) , nom. nud.

Orobanche pedunculata Roxburgh (1814: 45) , nom. nud. Roxburgh (1832: 29).

Aeginetia pedunculata Wallich (1831: 13 , t. 219). Walpers (1844: 481), Reuter (1847: 43), Wight (1850: 5, Plate 1421), Hooker (1885: 320), Forbes & Hemsley (1890: 221), Trimen (1895: 261), Prain (1905: 365), Ridley (1923: 488, Fig. 120), Pellegrin (1927: 463, Fig. 51 4–6), Beck-Mannagetta (1930: 20), Kanjilal et al. (1939: 385), Craib (1962: 196), Jafri (1976), Philcox (1997: 372), Ho (2000: 11; drawing depicts not A. acaulis but A. indica ), Parnell (2001: 75, 2008: 144, Fig. 1B ), Kress et al. (2003: 367), Cho et al. (2016: 156), Kumar et al. (2020a: 239), Kiew (2021: 294, Fig. 1 , Plate 60B, C). LECTOTYPE (designated by Parnell 2001: 75):—Tab. 219 in Plantae Asiaticae rariores Vol. 3 by Wallich (1831: t. 219).

Aeginetia abbreviata Buch. -Ham. ex Bentham (1835: 55). Walpers (1843: 400, 1844: 481), Reuter (1847: 43). ≡ Phelypaea abbreviata (Buch.-Ham. ex Benth.) Steudel (1841: 318) . ≡ Aeginetia pedunculata var. abbreviata (Buch.-Ham. ex Benth.) Beck-Mannagetta (1930: 20) . LECTOTYPE (designated here):—[ MYANMAR. Bago Region:] Prome [Pyay], 10 September 1826, N. Wallich s.n., Cat. No. 3965E (K: K001117749 http://specimens.kew.org/herbarium/K001117749 photo!).

Aeginetia sessilis Shivamurthy & Rajanna (1994: 133) . TYPE: — INDIA. Karnataka state: Chikmagalur district, Kerekatte, 26 September 1992, G.R. Shivamurthy 114 (holotype: CAL: CAL0000019099 photo!, isotype: Mahatma Gandhi Memorial College Herbarium [as MGM]).

In addition, Aeginetia mairei H.Léveillé (1916: 199) described from Yunnan, China, is possibly conspecific with either A. acaulis ( Zhang & Tzvelev 1998) or A. indica ( Govaerts 1995) . Aeginetia saccharicola Bakhuizen van den Brink (1933: 87) described from Java, Indonesia, is indicated as a synonym of A. pedunculata by Govaerts (1995). Aeginetia trimenii Livera (1927: 155) described from Sri Lanka is indicated as a synonym of A. pedunculata by Govaerts (1995) and Philcox (1997). The identities of A. mairei , A. saccharicola and A. trimenii still remain to be verified.

Aeginetia acaulis has priority over Aeginetia pedunculata ; despite this, these species were frequently united under the latter name (see Kumar et al. 2020b). For example, most recently, Kiew (2021) cited the species as “ Aeginetia pedunculata (Roxb.) Wall. ”, since she assumed that the basionym of Aeginetia pedunculata is Orobanche pedunculata Roxburgh nom. nud. However, a combination based on a nomen nudum cannot be made, as, according to the ICN ( Turland et al. 2018: Art. 11.4), only a legitimate name can be used as a basionym of a combination. Therefore, the description by Wallich (1831) introduced a new species rather than a new combination; Wallich’s work, and not the Roxburgh’s (1814) one, provides the basionym of Aeginetia pedunculata . At the same time, Orobanche acaulis Roxburgh (1820: 89) , contrary to the view of Kiew (2021), is a validly published name thus acting as the protologue of Aeginetia acaulis .

Additional specimens examined:— VIETNAM. Dak Nong Province: Cu Jut District, Tam Thang commune, Dipterocarpus forests, in bamboo thickets, around point 12°35’06.6’’N 107°55’02.5’’E, elev. ca. 400 m, 14 October 2020, Van The Pham, Van Canh Nguyen PVT1032 (MW:herbarium sheet MW0758398https://depo.msu.ru/open/public/ en/item/MW0758398 and spirit material; photo LE: LE01093257 https://en.herbariumle.ru/?t=occ&id=136423).

Other field records examined:— VIETNAM. Dak Lak Province: Buon Don District, Krong Na commune, Dipterocarpus forests, in bamboo thickets,around point 12°57’15.3’’N 107°49’13.8’’E,elev.ca. 300m, 20 October2020, Van The Pham, Van Canh Nguyen PVT1031 (photo LE: LE01093256 https://en.herbariumle.ru/?t=occ&id=136422); Buon Don District, Krong Na commune, Yok Don National Park, Dipterocarpus forests, in bamboo thickets, around point 12°54’58.9’’N 107°45’08.4’’E, elev. ca. 300 m, 11 October 2019, Van The Pham, Xuan Thien Tran PVT1029 (photo LE: LE01093254 https://en.herbariumle.ru/?t=occ&id=136420); Buon Don District, Krong Na commune, Yok Don National Park, Dipterocarpus forests, in bamboo thickets, around point 12°51’40.2’’N 107°44’57.2’’E, elev. ca. 300 m, 15 December 2019, Van The Pham, Quang Diep Dinh PVT1030 (photo LE: LE01093255 https://en.herbariumle. ru/?t=occ&id=136421); Buon Don District, Yok Don National Park, 19 August 2017, Van Canh Nguyen s.n. (photo LE: LE01089900 https://en.herbariumle.ru/?t=occ&id=75673).

Distribution: — Pakistan, India, Sri Lanka, Myanmar, southern China, Thailand, Laos, Cambodia, Vietnam, Peninsular Malaysia, Indonesia (Java, Sumatra), Philippines.

Ridley (1923) indicated the presence of this species in Borneo, but it has not been confirmed by any specimens or other studies.

The mention of Singapore as a locality for A. acaulis by Hooker (1885) likely refers to a location within the borders of the former British India, because Singapore is listed by him under Indian distribution. Towns and settlements with similar names are known in several Indian states. Philcox (1997) apparently misinterpreted Hooker’s indication with respect to this location. The absence of the species in the Republic of Singapore is confirmed by Lindsay et al. (2022).

Habitat and phenology: —Various forests (including dipterocarp forests and bamboo thickets), grasslands, plantations, at 50–1500 m a.s.l. Flowering and fruiting from April to November.

Notes on typification of Aeginetia acaulis

The protologue of Orobanche acaulis , the basionym of Aeginetia acaulis , does not cite any specimens and contains the following information on studied plants: “Found growing on the root of the China sugar cane, in the Botanic Garden at Calcutta, and in full blossom in September”.

We were unable to find any specimens of this species that could be studied by Roxburgh during preparation of the protologue. Therefore, we designate the colour drawing included in the protologue ( Roxburgh 1820: Plate 292) as the lectotype following Arts. 9.3 and 9.11 of ICN ( Turland et al. 2018).

Notes on typification of Aeginetia abbreviata

The protologue of Aeginetia abbreviata published in “Scrophularineae Indicae...” ( Bentham 1835) contains a morphological description along with the following information: (1) Wallich’s catalogue number 3965; (2) locations as “Peninsula” referring to Peninsular India, “Sillet” currently known as Sylhet city in Bangladesh located in a district and a division holding the same name, “ Rangoon ” currently known as Yangon city in Myanmar being the capital of Yangon region, and “Prome” currently known as Pyay township in Myanmar; (3) Wallich as a specimen collector. With help of http://wallich.rbge.info/ online resource, we have found six gatherings corresponding to subdivisions of Wallich’s catalogue number 3965 ( Wallich 1829):

3965A from “Patnitola” (now Patnitala, a region in Bangladesh far away from Sylhet), received from Buchanan-Hamilton’s herbarium, collected on 28 January 1808, housed at K (K001117744);

3965B received from Wight’s herbarium, housed at K (K001117746);

3965C from Courtallam (a town in Peninsular India, Tamil Nadu state), received from Madras herbarium, collected in September 1818, housed at K (K001117747);

3965D from “Sillet” (now Sylhet), collected by “FD” (F. De Silva, known as Wallich’s collector), № 1408, in April 1824, housed at E (E00116070) and K (K001117748);

3965E from “Prome” (now Pyay), collected on 10 September 1826, housed at K (K001117749), the herbarium sheet bears a label that states “Wall.” which is apparently Wallich as a collector;

3965F received from Heyne’s herbarium, housed at K (K001117745).

In addition, a sheet at K (K000999883) is labeled as belonging to Wallich’s catalogue number 3965, and bears no original label or gathering details.

We select the specimen labeled as 3965E (K, barcode K001117749) as the lectotype following Arts. 9.3 and 9.11 of ICN ( Turland et al. 2018), because it is the only specimen under the catalogue number 3965 undoubtedly collected by Wallich. The location of this specimen also matches the protologue. The other specimens listed above are possible syntypes; all of them most likely belong to other collectors, and besides 3965A originates from a location not indicated in the protologue. The citation of Wallich 3695 by Parnell (2001) is a typographic error.

It should be noted that Kumar et al. (2020a) apparently erroneously listed Aeginetia abbreviata as a synonym of two species accepted by them, A. acaulis and A. pedunculata .

Notes on the identity of Aeginetia sessilis

Aeginetia sessilis is structurally very close to the widely distributed A. acaulis . Both species are known to occur in the Western Ghats ( Vijay et al. 2017). The protologue ( Shivamurthy & Rajanna 1994) states that A. sessilis differs from A. acaulis in the smaller size of the plant, absence of peduncle, 1–3-flowered inflorescences, absence of pedicel (flowers are sessile), brown to brick-red calyx with obtuse apex (without a beak), and fewer and larger seeds. Shivamurthy & Rajanna (1994) have not provided the states of these characters for A. acaulis , which complicates any direct comparison. As follows from the available descriptions of A. acaulis (e.g. Beck-Mannagetta 1930, Philcox 1997, Zhang & Tzvelev 1998, Parnell 2001, 2008), most of the indicated characters actually do not allow distinction of these species. The potentially informative characters are only the absence/presence of a pedicel and the seed size.

The pedicel length is known to be highly variable in A. acaulis and ranges at least between 1.5–10(14.5) cm ( Pellegrin 1927, Beck-Mannagetta 1930, Jafri 1976, Philcox 1997, Zhang & Tzvelev 1998, Kiew 2021). Despite the considerable variation, which is additionally evident from the available photographic records (e.g. Chan 2009, Ray & Dasgupta 2009, Vijay et al. 2017, Kiew 2021), the flowers of A. acaulis are apparently constantly pedicellate, with the pedicels readily discernible in specimens and images. The holotype of A. sessilis ( Fig. 4 ) is mounted in such a way that the bases of flowers are largely obscured by the host plant, which prevents precise measurement of the pedicels in this specimen. However, for two of the flowers it is evident that they are not strictly sessile, but rather possess pedicels at least 5 mm long. Thus, it appears more accurate to describe the flowers of A. sessilis as shortly pedicellate to possibly sessile; such flowers are only characteristic of A. sessilis (and not of A. acaulis ).

The seeds of A. sessilis are described as “60–90 microns” in its protologue ( Shivamurthy & Rajanna 1994), which is apparently a mistake, since it is much smaller than the known seed size in the entire genus Aeginetia ( Bakhuizen van den Brink 1921, Sharma & Uniyal 2009, Parnell 2012, Vijay et al. 2017, Dwari et al. 2019), and the diagnosis (both Latin and English) states that the seeds are larger than those of A. acaulis . The indications that the seed size (not substantiated by any illustrations) is “ 0.04 mm ” for A. indica and A. sinensis Beck-Mannagetta (1930: 19) by Zhang & Tzvelev (1998) are likely also erroneous; they possibly should be read as 0.4 mm. This issue was re-examined by Vijay et al. (2017) based on the material of A. acaulis , A. indica and A. sessilis collected by them in Kerekatte (Karnataka state), the type location area of A. sessilis . The authors do not comment on the sampling they utilised, nor the number of specimens, individuals, fruits and seeds sampled. Vijay et al. (2017) reported the seeds of A. acaulis as 274–356 μm long, whereas those of A. sessilis were 247–298 μm long. The authors therefore appear to have shown that the seeds of A. sessilis are not larger, but smaller than those of A. acaulis . We argue that this result is inconclusive with respect to the distinctness of the two species. (1) Although the size ranges are quite different, they overlap significantly. The ranges could possibly be consistent with the idea of two distinct species, but it is probable that the overlap would increase if more representative and wider sampling were to be employed. In particular, it is important to include data for other geographical locations of the widespread A. acaulis . (2) The example of the most well-studied species of Aeginetia , A. indica , suggests significant intraspecific variation of seed size in the genus. Aeginetia indica is reported to have seeds 232–279 μm long by Vijay et al. (2017) and 166–180 μm long by Dwari et al. (2019). Thus, the ranges currently known for A. acaulis and A. sessilis are likely to be underestimated.

Given the current state of knowledge, it does not seem worthwhile to accept A. sessilis as a distinct species, because the shortly pedicellate to possibly sessile flowers (i.e. flowers with pedicels not obvious without special observations) appear to be its only diagnostic feature. Further clarification of its status is required but should be combined with investigation of the entire genus across its entire distribution range by means of gross morphology, statistical analysis of seed size, and molecular phylogenetic reconstructions.

The specimen Pham, Nguyen PVT1032 from Dak Nong Province of Vietnam fits closely the concept of A. acaulis s.s. differing only in subsessile flowers, which are characteristic of A. sessilis . In Pham, Nguyen PVT1032, the pedicels are 4–7 mm long; in the fresh and liquid material, the flowers have a sessile appearance because the pedicels are thick, fleshy and gradually become thicker towards calyx base (see Fig. 1 ). Although the flowers are stated to be sessile in the protologue of A. sessilis , its original material (the holotype, and see also Shivamurthy & Rajanna 1994: Fig. 1 ) shows the same overall plant appearance as the Vietnamese specimen Pham, Nguyen PVT1032. Furthermore, investigation of the holotype of A. sessilis revealed presence of pedicels of the same length as in Pham, Nguyen PVT1032. The location of the specimen Pham, Nguyen PVT1032 is within the known distribution range of A. acaulis and far away from the Western Ghats of India from where A. sessilis was reported. It is noteworthy that populations of A. acaulis with typical morphology (i.e. with evidently pedicellate flowers; see Fig. 3 ) were observed in the neighboring Dak Lak Province, ca. 40 km air distance from the Dak Nong population. A similar situation is found in the type gathering of A. sessilis : the holotype contains a field note stating that the plant was associated with A. pedunculata (currently considered to be a synonym of A. acaulis ). Thus, the Vietnamese specimens in combination with the available information on the type of A. sessilis support the idea of a highly variable A. acaulis s.l. (i.e. including A. sessilis ) with its shortly pedicellate (to epedicellate) morph representing extreme cases of variation of the pedicel length.

Figures

FIGURE 1. Aeginetia acaulis. A, B. Anthetic plants in natural habitats. C. Same plant as in B, side view. D. Flower, side view (calyx removed). E–G. Plants, side view (to scale). Pham, Nguyen PVT1032. Photos by V.C. Nguyen (A–C) and V.T. Pham (D–G); design by M. Nuraliev.

FIGURE 2. Aeginetia acaulis, floral structure. A-C. Side, abaxial and oblique views of flower (calyx and distal portion of corolla removed). D. Adaxial stamen. E. Abaxial stamen. F. Flower, abaxial view (abaxial half of corolla distally removed). G. Flower, abaxial view (abaxial half of corolla with abaxial stamens removed). H. Abaxial stamens, adaxial view. I. Distal portion of abaxial half of corolla, adaxial view. Pham, Nguyen PVT1032. Photos by V.T. Pham (A–E) and V.C. Nguyen (F–I); design by M. Nuraliev.

FIGURE 3. Aeginetia acaulis. A. Habitat. B. Flowers, front view. C. Plant with long pedicels. Photos by V.C. Nguyen from Nguyen s.n. (A), V.C. Nguyen from Pham, Nguyen PVT1031 (B), X.T. Tran from Pham, Tran PVT1029 (C); design by M. Nuraliev.

FIGURE 4. Holotype of Aeginetia sessilis (CAL: CAL0000019099). Reproduced with permission of the Director, Botanical Survey of India. Inset: enlarged plant of A. sessilis; arrow denotes pedicel.