Sida glutinosa, Comm. ex Cavanilles, 1785

Baracho, George Sidney & Agra, Maria De Fátima, 2016, A new record of Sida glutinosa (Malvaceae), a rare species of the Caatinga in northeastern Brazil, with lectotypifications and taxonomic notes on the allied Sida glabra, Phytotaxa 282 (1), pp. 37-45 : 41

Notes on Sida glutinosa and Sida glabra

Sida glutinosa was formally described and illustrated by Cavanilles (1785: 16) based on vegetative and floral characters, in particular by the presence of viscid hairs. The type specimens were imprecisely dated, but were collected in the late 18th century from two localities: 1) “ Isle de France ” (now the island of Mauritius, in the Indian Ocean); and 2) “ Saint-Domingue ”, in the Caribbean island of Hispaniola (including modern Haiti and the Dominican Republic). Of these, the voucher specimen from “ Isle de France ”, collected by the botanist Philibert Commerson, was chosen by Borssum-Waalkes (1966: 190) as the lectotype. More recently, Krapovickas (2006: 20) formally re-typify the name S. glutinosa based on another specimen collected by Commerson from “ Isle de France, au reduit” (at MPU, Herb. Thouin in Herb. Cambessèdes). The author claimed that the specimen previously chosen by Borssum-Waalkes (P-JU 12278 A) is a mixed collection, and that the specimen P-JU 12278 B! is assigned to Mazure (“ herb. D. Mazure ”). However, Borssum-Waalkes’s choice may be interpreted as the correct decision, since only the part corresponding to the original description is assigned as lectotype, in accordance to Article 9.14 of the current International Code of Nomenclature for Algae, Fungi and Plants (McNeill et al. 2012).

S. glabra Miller (1768 : without pagination), on the other hand, is a species closely allied to S. glutinosa that was described based on a specimen collected between 1729 and 1733 by the botanist William Houstoun, from an unknown locality, but probably Jamaica, Cuba or in the state of Veracruz, in Mexico ( Howard 1975: 370). The author provided a short Latin and English diagnosis, mentioned as a synonym the polynomial Malvinda abutili folio acuminato, floribus parvis luteis, ex alis foliorum, semine bidente, applied in Houstoun’s manuscript (“Houst. MSS.”), and added morphological descriptions based on vegetative and reproductive characters: “… pointed, yellow, … leaf, and small yellow flowers at the wings of the leaves, and seeds with two teeth”. The type specimen of S. glabra is preserved in the Herbarium of the Natural History Museum (Houstoun s.n., BM, photo BH-5077, examined on-line at the Natural History Museum, 2014).

Sida glutinosa and S. glabra have long been considered synonyms. This view had been adopted by Fryxell (1985, 1988, 1992, 1993) and followed by e-floras and databases since (see The Plant List 2013, Tropicos 2015, Wunderlin et al. 2016). The synonymization was based on the inconsistency of the presence or absence of glandular hairs on the stems, pedicels, and calyces in both species ( Fryxell 1988). On the other hand, Monteiro-Filho (1936, 1949), Kearney (1954, 1958), Borssum-Waalkes (1966), Fuertes Aguilar (1995), and Krapovickas (2006) recognized S. glabra as a morphologically distinct species from S. glutinosa , although their taxonomic boundaries aren’t sufficiently clear ( Fuertes Aguilar 1995).

The view of these authors was later confirmed by ITS molecular data and provides strong support that both S. glabra and S. glutinosa are genuine species with independent taxonomic status ( Fuertes Aguilar et al. 2003). In fact, according to the authors, ITS actually shows that S. glutinosa is closest to S. jussiaeana , and closer to S. urens than to S. glabra , which is in turn closest to S. martiana . Thus, we believe that Fryxell’s conclusion that there is only a single variable species, S. glabra , was probably due to a need for more refined studies of living specimens in the field, and that such confusion is only possible with herbarium specimens. So, based on the presence or absence of glandular hairs on the stems, pedicels, and calyces, in addition to the morphology of inflorescence and sepals, as observed by Fuertes Aguilar (op. cit.), we conclude that these two species can be easily distinguished from each other ( Table 1).

Sida glutinosa occurs in parts of the Old World ( Borssum-Waalkes 1966), but the geographic distribution of this species is primarily restricted to the New World tropics, from northwest Mexico to the Caribbean, Venezuela to Equador, and Bolivia to Argentina, Paraguay and Brazil ( Fuertes Aguilar 1995, Krapovickas 2006). In Brazil, the species is found from the Northeast to Central-West and Southeast Regions. In the Northeast of Brazil, for example, only a single record was previously reported by Monteiro-Filho (1949) and re-collected in 1996 after a gap of 50 years (Brandão et al., in review). On the other hand, some specimens of Sida from IPA (see Albuquerque 35AJ, Andrade-Lima 8989, Andrade-Lima et al. 9303, Lima et al. 734, and Pereira et al. 874) have been incorrectly assigned to S. glutinosa , but there is no doubt that all such collections refer to S. ulei Ulbr. (in Ule 1909: 225). On the other hand, S. glabra is restricted to the New World ( Fuertes Aguilar 1995), from Mexico and the Caribbean to Colombia, Venezuela and Guyana, but occurs in different areas within these regions when compared with those of S. glutinosa . Futhermore, it is highly likely that S. glabra also occurs in parts of Brazil. On the other hand, some herbarium specimens of S. luschnathiana Steudel (1841: 578) from central Brazil have been previously identified as S. glabra (under the Fryxell’s viewpoint), because of the similarities of the general aspect of the plant and due to the presence of glandular hairs and solitary flowers axillary.

The collect of S. glutinosa in a remnant of caatinga in the state of Paraíba is important because it helps to increase knowledge of the species, and may indicate the possible presence of other rare species of Malvaceae (or indeed other Angiosperms) in the State. Furthermore, the new record highlight the importance of floristic studies in determining the geographical distribution of rare species, as well as the importance of protecting remote caatinga fragments containing species in danger of extinction. Based on the IUCN Red List Categories and Criteria ( IUCN 2001), S. glutinosa has the conservation status of Critically Endangered (CR), justified by its very restricted distribution, and based on estimates of decline of local populations due to human activities, e.g. fire and farming.