Philodendron carajasense sp. nov. (Araceae), a rheophyte from Carajás Mountain Range, northern Brasil

The Carajás region is localized in southeastern Pará State, Brazil, and is characterized by moderately elevated uplands and hills (up to 800 m a.s.l.), usually covered by vegetal physiognomies that are more open than the locally widespread ombrophile mixed forest (Silva et al. 1996) that dominate in the lowlands (below 200 m a.s.l.). These hills are usually characterized by moderate to intense rock outcroping, and the exposed rocks are mainly formed of iron ore (Klein and Ladeira 2002). Because of this peculiar aspect, the biota occurring on these hills have a strong tendency to be rather specialized and even endemic such that these communities can be defined as insular ecosystems.
Recent concerns about the biota occurring on these hills are justified because Carajás is one of the largest iron ore deposits in the world. Together with iron, there are also large deposits of manganese, tin, copper, bauxite and gold. Large-scale exploitation in the Carajás region is changing the landscape dramatically. Following Brazilian laws and environmental agency demands, efforts to understand the floristic diversity in this province has been carried out prior to ore exploitation and this strategy has proven to be effective. Th is article aims to present a new aroid species discovered during one of these preliminary floristic studies (Golder Associates 2011). In 2010, the senior author (EGG) was asked to identify a Philodendron (Araceae) specimen collected by the junior author (AJA) in Canaãdos Carajás, Pará State, as part of an environmental study prior to the implantation of a new iron ore mine in Carajás (Golder Associates 2011). It was recognized as belonging to the subgenus Pteromischum (Grayum 1996), but could not be assigned to any of the described species. One of the peculiar aspects of this new species was the habit described on the label, which seemed to be mostly rheophytic. The genus Philodendron is the second largest in the family Araceae (Gonçalves 2011) and present an extreme variation in habit and life forms (Mayo 1997). Although aquatic species are not rare, rheophytic habit in the genus is thus far only known from Philodendron flumineum E. G. Gonç . in central Brazil (Gonçalves 2000, 2004). Field studies confirmed the recurrent rheophytic habit and the new species is described and illustrated here.