Himatanthus

Amasifuen Guerra, Carlos A., Delprete, Piero G. & Spina, Andrea P., 2016, Synopsis of Himatanthus (Apocynaceae, Rauvolfiodieae: Plumerieae) species from Peru, Phytotaxa 283 (1), pp. 65-73 : 66-67

Himatanthus in Peru

To date there has been a total of six species of Himatanthus cited for Peru ( Brako & Zarucchi 1993; Ruokolainen & Tuomisto 1998; Ulloa et al. 2004; Rodriguez et al. 2006; Tropicos, 2016): H. articulatus , H. bracteatus , H. lancifolius , H. phagedaenicus , H. sucuuba , and H. tarapotensis (K. Schumann ex Markgraf 1932: 339) Plumel (1990: 112) . Our research indicates that there are fewer species in the country. The proliferation of names, in our opinion, is because a few morphological features help differentiate the species of Himatanthus and these have been variably interpreted for species delimitation and identification of herbarium specimens.

One of the most frequently reported species of Himatanthus in Peru is H. sucuuba (e.g., Macbride 1959, Acevedo 1998, Alonso et al. 1998, Vásquez 1997, Ruokolainen & Tuomisto 1998, Vásquez & Phillips 2000, Pitman et al. 2002, 2003 a, b, Pennington et al. 2004, Tropicos 2016). However, our study indicates that this species does not occur in the country. Rather, H. sucuuba has a complex and often misinterpreted taxonomic history with many studies in the field of ethnobotany (e.g., Bourdy et al. 2000, Shanley et al. 2011, Odonne et al. 2013), leaf anatomy ( Larrosa & Duarte 2005), morphology ( Amaro et al. 2006), biochemistry (e.g., Perdue & Blomster 1978, Endo et al. 1994, Miranda et al. 2000, Wood et al. 2001, Silva et al. 2007, 2010), and ecology (e.g., Spichiger et al. 1990, Ferreira et al. 2007, 2009 a, b) reporting its presence in Peru. However, Spina (2004) and Spina et al. (2013) treated H. sucuuba as a synonym of Himatanthus articulatus , which is a species that does not occur in Peru. Therefore, as most of the above publications did not cite voucher specimens, it is impossible to know which species was/were actually studied. Following the species delimitations of Spina (2004) and Spina et al. (2013), we find that there are three species of Himatanthus occuring in Peru: H. phagedaenicus , H. revolutus ( Huber 1915: 200) Spina & Kinoshita (in Spina et al. 2013: 1307), and H. tarapotensis . For the differentiation of the three species present in Peru, most vegetative characters are of little use, taking into account the broad variation within each species ( Spina 2004). For example leaf bases are cuneate, and the apices are either acute or acuminate for all species in Peru. Similarly, the number of secondary veins can vary from 12 to 24 in all Peruvian species. On the other hand, venation type and angle of the secondary veins with respect to the midrib can provide some diagnostic characters that can be used for distinguishing the species. Himatanthus revolutus has a mixed type of brochidodromus-eucamptodromus venation, whereas H. tarapotensis and H. phagedaenicus exhibit a simple brochidodromous venation. The angle of the secondary veins with respect to the midrib is useful in distinguishing H. revolutus , with secondary veins nearly or exactly perpendicular to the midrib (80–90°), while they are at 70–80° in H. phagedaenicus and 50–70° in H. tarapotensis .

Reproductive features are a reliable source of significant diagnostic characteristics to distinguish species of Himatanthus ( Spina 2004) . For example, the corollas are 45–70 mm long in H. phagedaenicus and H. revolutus versus 35–45 mm long in H. tarapotensis . Himatanthus phagedaenicus is easily distinguished by its corolla tube and lobes of approximately the same length and style head with trichomes, whereas the corolla lobes are longer than the tube and the style heads glabrous in H. tarapotensis and H. revolutus . Finally, the follicles are 27–29 cm long in H. tarapotensis , 16–26 cm long in H. phagedaenicus , and 12.5–25.5 cm long in H. revolutus .