Monographs Details: Amphidasya
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Family:Rubiaceae
Scientific Name:Amphidasya
Discussion:

Pittierothamnus Steyermark, Bol. Soc. Ven. Ci. Nat. 23(101): 92. fig. 11. 1962.

Type. Amphidasya ambigua (Standi.) Standl.

This genus has had a strange and remarkable history. The original species was at first described by Standley as Sabicea ambigua (Field Mus. Publ. Bot. 7: 49. 1930), who placed it under Sabicea at the time because of its resemblance to another species, S. umbrosa Wernh., possessing prominent multifid stipules. A year later, Standley transferred Sabicea ambigua and S. umbrosa, together with a third species, to his new genus, Amphidasya, which he segregated mainly on the basis of its prominent stipules.

Standley also described two species which he placed doubtfully under the genus Deppea, namely, Deppea (?) venezuelensis (Field Mus. Publ. Bot. 8: 52. 1930) and D. (?) colombiana (Field Mus. Publ. Bot. 11: 201. 1936), the former from Venezuela with entire persistent stipules, the latter from Colombia with laciniate stipules. He believed, although he had no definite proof, that the fruit was capsular, and for that reason did not place these two taxa in Sabicea or Amphidasya, both of which have fleshy fruits. Instead, he left both taxa unsatisfactorily placed in a genus which he confidently stated as one to which they did not pertain. At the time, he expressed the opinion that these two species probably belonged to a distinct undescribed genus which must await the availability of flowering material.

In 1962 the present author described the genus Pittierothamnus, based upon material originating from the Parque Nacional Pittier of Estado Aragua, in the Coastal Cordillera of Venezuela, with one species, P. elineolatus Steyerm. [Bol. Soc. Ven. Ci. Nat. 23(101): 92-95. fig. 11]. This genus was described as having entire persistent stipules combined with persistent foliaceous calyx lobes and a fleshy fruit. A comparative study of Pittierothamnus elineolatus and Standley's Deppea (?) venezuelensis, based on Funcke 793, without definite locality in Venezuela, shows that the two taxa are conspecific.

The question now arises as to whether Amphidasya and Pittier othamnus are congeneric. So far as the hypanthium and fruiting structures are concerned, they cannot be separated. Both have indehiscent, subfleshy fruits with numerous sphaeroid, foveolate seeds. Both have foliaceous, persistent, calyx lobes, and both possess non-lineolate, non-striolate leaves, a character which distinguishes them from both Tammsia and Sommera. However, a study of their floral morphology brings out the following differences, based upon those taxa with known flowers: (1) in Amphidasya the anthers have a short to elongate terminal appendage which is not present in Pittier othamnus] (2) in Amphidasya the corolla tube is greatly elongated and narrowly salverform, equaling or exceeding the calyx segments, whereas in Pittierothamnus the corolla is only short-cylindric and merely slightly exceeds the calyx lobes; (3) in Amphidasya the interior of the corolla lobes has conspicuous verrucose-papillate cells over the surface, these being absent in Pittierothamnus.

The situation, however, is complicated by the consideration of placing two undescribed species, one from Brazil in the region of Serra da Neblina, the other from the lowlands of Department Santander, Colombia. Both these undescribed taxa have the foliaceous, persistent calyx lobes and similarly fleshy fruits, and both have the stipules reduced in size with the subulate segments reduced also in size and number. In their persistent foliaceous calyx lobes they resemble Pittierothamnus, but the multifid type of stipule, although greatly reduced, more closely resembles that known in Amphidasya. Nevertheless, the enlarged type of multifid stipule, known in A. ambigua and A. umbrosa, breaks down in A. bullata Standi., which has a short, reduced few-cleft stipule, thus aligning it to the two undescribed taxa mentioned above from Serra da Neblina and Department Santander, Colombia. In the absence of flowers in these last two taxa, it is difficult to assign them definitely to Amphidasya, on the one hand, or to Pittier othamnus, on the other hand. The same enigma arises with respect to Standley's Deppea (?) colombiana. It is probable that this taxon falls into Amphidasya with reduced length of stipular awns (7-10 mm long), although the awns are as numerous as in other species of known Amphidasya. However, no flowering material of Deppea (?) colombiana is known at present.

In view of the uncertainty in distinguishing the two genera in the absence of flowering material of some of the taxa, and judging by a basic similarity of fruiting and persistent calyx lobe morphology, it is my considerate judgment at this time that Pittier othamnus be merged with Amphidasya. Although there are floral differences between the two genera, as given above, based upon available flowering material, it is probable that none of these differences will stand up when flowering material becomes available for the species now known only in fruit. Just as the prominence and degree of lobing of the stipule varies, ranging from completely entire stipules to prominently lobed ones, it is probable that the floral differences which stand out at present between Amphidasya and Pittierothamnus will eventually be bridged over.