The Araceae in Ceará, Brazil: humid forest plants in a semi-arid region

The family Araceae Juss. currently consists of 126 genera and 3305 species (Boyce & Croat 2012). It is sub-cosmopolitan in distribution and most species and genera occur in the tropics (Mayo et al. 1997). The family is very diverse in life form, morphology and anatomy (Grayum 1990), ranging from massive arborescent or epiphytic herbs to minute floating aquatics (Bogner 1987; Croat 1990; Mayo et al. 1997). The duckweeds, formerly known as Lemnaceae S.F. Gray, are now subfamily Lemnoideae, a near-basal clade within Araceae (Cabrera et al. 2008; Cusimano et al. 2011). Armstrong (2012) is an excellent illustrated reference for duckweeds. The Araceae form the basal clade in the order Alismatales (Stevens 2001 onwards; APGIII 2009). Braga’s (1960) checklist, based on information from Ceará, includes many cultivated taxa and remains a useful source although the nomenclature is often out of date. Coelho et al. (2010, 2012) is currently the most complete checklist for Brazil. Andrade et al. (2006) published a checklist for Brazil’s semi-arid region. Papers dealing with one or several species, mostly reports of new discoveries or records, have been published by Gonçalves & Temponi (2004) and Bogner (1980). Population genetics and biogeography of Anthurium Schott and Monstera Adans. in the upland humid forests of Ceará have been studied by Andrade et al. (2007, 2009), who also studied leaf morphometrics in the same taxa (Andrade & Mayo 2010; Andrade et al. 2008, 2010). Some Ceará species are included in more general revisions: Philodendron Schott: Sakuragui et al. (2006); Scaphispatha Brongn. ex Schott: Gonçalves (2005); tribe Spathicarpeae: Gonçalves (2002); Spathiphyllum Schott: Bunting (1960); Syngonium Schott: Croat (1981) and Zomicarpa Schott: Gonçalves (2012).

The state of Ceará lies within the semi-arid region of Northeast Brazil and is almost entirely covered with caatinga vegetation, a deciduous thorn forest (Figueiredo 1997). During the rainy season, temporary lakes and ponds with aquatic species are found throughout the landscape. Montane forests (“brejo forests”) occur naturally where higher rainfall is caused by suitable combinations of humid winds, altitude, scarps and position (usually facing to the east and northeast). These areas are classified as remnants of formerly more extensive areas of Brazilian Atlantic Forest (Figueiredo 1997: “Floresta subperenifolia tropical pluvionebular”). Higher rainfall and lower temperatures allow the development of large evergreen trees and epiphytic and hemi-epiphytic flora in uplands on granitic geology at Baturité, Maranguape, Meruoca, Uruburetama, Pacatuba, and along the leading edge and scarp of sedimentary outcrops in northern Ibiapaba and the Chapada do Araripe (Oliveira & Araújo 2007).
The aim of this study is to provide the first published taxonomic treatment for the State of Ceará of the family Araceae, plants which in this mostly semi-arid region are confined largely to relictual humid montane forest fragments (Andrade & Mayo 2010).