Saribus Blume, Rumphia 2: 48 (1838)

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Number of Taxa

  • 9 species

Discussion

  • Recent analysis of molecular data uncovered the startling fact that Livistona, as currently recognized, is not a natural, coherent genus and that eight of its species, including the widely cultivated Livistona rotundifolia, along with the rare Pritchardiopsis jeanneneyi constitute a distinct genus, for which the earliest name is Saribus.

    Molecular data indicates that the majority of genera were indeed monophyletic. Livistona, however, was not found to be monophyletic, but was divided among two different groups that were not each other's closest relative. One group comprised three Livistona species (L. merrillii, L. rotundifolia and L. woodfordii) and two samples of the monotypic Pritchardiopsis jeanneneyi. The second group included 19 Livistona species from eastern Asia, south-east Asia, Australia and Africa. The grouping of the three Livistona species and Pritchardiopsis was highly supported and was more closely related to Pholidocarpus, Licuala and Johannesteijsmannia than to the remaining species of Livistona. Thus, to render all Trachycarpeae genera monophyletic, this group requires recognition at the genus level. A generic name, Saribus (Blume 1838) typified on Saribus rotundifolius (Lam.) Blume (syn. Livistona rotundifolia (Lam.) Mart.), is already available for this group. It takes priority over the other generic name in the group, Pritchardiopsis (Beccari 1910), which must be placed as a synonym of Saribus because of its later publication date.

    Saribus includes a Philippines endemic species (S. merrillii), a group of Papuasian species (S. brevifolius, S. chocolatinus, S. papuanus, S. rotundifolius, S. surru, S. tothur and S. woodfordii), an outlier species in New Caledonia (S. jeanneneyi) and one species widespread in Malesia (S. rotundifolius). The removal of Saribus reveals a new disjunction in the distribution of true Livistona between Australia and southern New Guinea (L. alfredii, L. australis, L. benthamii, L. concinna, L. decora, L. drudei, L. eastonii, L. fulva, L. humilis, L. inermis, L. lanuginosa, L. lorophylla, L. mariae, L. muelleri, L. nasmophila, L. nitida, L. rigida and L. victoriae) and tropical Asia west of Wallace's Line (L. boninensis, L. chinensis, L. endauensis, L. exigua, L. halongensis, L. jenkinsiana, L. saribus, L. speciosa and L. tahanensis), in addition to the known disjunction in Arabia and the Horn of Africa (L. carinensis).

    Saribus is readily distinguished from Livistona in the field, in cultivation and in the herbarium. The morphological characters that enable identification of Saribus include trifurcate inflorescences, consisting of three main axes (sometimes two) that join at their base within a single prophyll, whereas Livistona produces inflorescences comprising a single main axis only (Dowe 2009). Saribus has orange, orange-brown, or red mature fruit color, whereas the fruits of Livistona are green, blue, purple, brown or black (Dowe 2009, Dransfield et al. 2008). It should be noted that this group had already been highlighted by Dowe (2009) as a distinctive element within Livistona in its former sense. Because of these clear, consistent characters, we have been able to place several species in Saribus that we were not able to sample for our phylogenetic research.

    From an anatomical perspective, Saribus and the rest of the Livistoninae excluding Livistona have intercostal cells of the adaxial epidermis that are differentiated into long and short cells within the same cell file. Livistona has adaxial epidermal cells uniformly of the long cell type, like all genera of Trachycarpeae outside of Livistoninae (Tomlinson 1961b, Tomlinson et al. 2010). A similar character distribution occurs for the presence of fibers that are associated with surface layers and also depart from the sheath of transverse veins of the lamina ramifying in the mesophyll (Tomlinson 1961b, Tomlinson et al., 2011). These character states, though not unique to Saribus, further distinguish Saribus from Livistona.

    The reduction of the monotypic Pritchardopsis into synonymy as Saribus jeanneneyi is a notable outcome of this research, given the rarity and conservation significance of this species, which persists as one adult and a few juveniles in the far south of New Caledonia. This taxonomic change is strongly supported by both the molecular and morphological data described above. Saribus jeanneneyi deviates slightly in some respects from other members of the genus. Its fruit are reported to be purplish (Hodel & Pintaud 1998), although a near-ripe fruit figured in this reference is in fact yellow-orange. The fruit are also large (ca. 4 cm diam.; Hodel & Pintaud 1998) with seeds surrounded by a keeled, woody endocarp (Dransfield et al. 2008). However, fruits of similar or larger size are found in some species of Saribus (S. surru, S. tothur) and at least one other has an equally woody, thickened endocarp (S. papuanus; Fig. 5). The loss of charismatic genera through nomenclatural change can be controversial, but it in no way reduces the conservation importance of this critically endangered New Caledonian endemic. In fact, by knowing its evolutionary relationships more clearly, we may be better placed to understand its biology and to make appropriate, informed conservation decisions as a result. (C.D.Bacon and W.J. Baker. 2011)

Bibliography

  • C.D.Bacon & W.J. Baker. 2011. Saribus Resurrected.