Ramenta morphology and its variations in Rafflesia (Rafflesiaceae)

Abstract

Ramentae are hair-like structures found on the perigone tube and diaphragm in species of Rafflesia (Rafflesiaceae). Although ramenta morphology provides an important taxonomic character, a consistent terminology has not been used in species descriptions. As such, morphological comparisons among species as well as among populations within a species are difficult. We used a variety of resources to document the morphology including the location and density of ramenta among 18 species of Rafflesia and between populations and/or sexes of two species. We identified five types of ramenta: tuberculate, filiform, swollen apex, toadstool, and fence-like and recognized several variations within each type. Ramenta types characterize four species complexes: R. patma (tuberculate), R. arnoldii (filiform), R. pricei (mostly swollen apex), and R. hasseltii (mostly toadstool). Our classification of ramenta offers a tool for using consistent terminology to re-evaluate previously described species and to define new species of Rafflesia.

Rafflesia kemumu (Rafflesiaceae), a new species from Northern Bengkulu, Sumatra, Indonesia

“…Our interpretation is matched by the illustration in Mahyuni et al (2015) showing branched ramenta, not toadstool, on the upper part of the perigone tube. Susatya et al (2017) also found compound toadstool ramenta only in the lower part of the diaphragm. As a consequence, we conclude that toadstool ramenta are not found on the upper perigone tube of R. gadutensis (FIG.…”

“…Key differences between R. kemumu and R. gadutensis are color of the perigone lobes; pattern, size, number, and color of warts on the upper surface of the perigone lobes; color and wart presence/absence on the upper surface of the diaphragm; blot arrangement of the two concentric rings of the windows closest to the diaphragm opening; types and distribution of ramenta; number and shapes of processes; and number of anthers (Table 1). Meijer (1984Meijer ( , 1997, Mahyuni et al (2015), and Susatya et al (2017) or obtained from photos by the late Prof.…”

“…Meijer (1997) described the ramenta on the lower surface of the diaphragm close to the perigone tube of R. gadutensis as "toadstool-like protuberances" with "only 1-2 mm long stalks." Susatya et al (2017) categorized this type of ramenta as compound toadstool. Although Meijer (1997) did not clearly indicate the location of these toadstool ramenta, he states that the "Perigone tube … covered at the inside with … ramenta which … have swollen heads [= swollen apex ramenta of Susatya et al (2017)] … a few branched or lobed ones near the diaphragm.…”

“…Susatya et al (2017) categorized this type of ramenta as compound toadstool. Although Meijer (1997) did not clearly indicate the location of these toadstool ramenta, he states that the "Perigone tube … covered at the inside with … ramenta which … have swollen heads [= swollen apex ramenta of Susatya et al (2017)] … a few branched or lobed ones near the diaphragm. Between the ramenta on the inner side of the perigone tube some … toadstool-like protuberances close to the inside of the diaphragm …."…”

“…The other Sumatran Rafflesia closely resemble each other and have been misidentified as R. arnoldii in the past; a few of these entities have been named as new species (Meijer 1997, Susatya et al 2005, Mat-Salleh et al 2010. Another taxon, R. atjehensis, was treated as a variant of R. arnoldii (Meijer 1997), but was considered distinct by Susatya et al (2017) because of differences in the type of ramenta.…”