Borreria apodiensis ( Rubiaceae : Spermacoceae ) , a new species from Ceará and Rio Grande do Norte , Brazil 1

A new species of Borreria (Rubiaceae) from Chapada do Apodi in northeastern Brazil is described and illustrated. A distribution map, illustrations, a conservation assessment, a key to morphologically similar taxa and images of the seeds and pollen grains are provided.


Introduction
Borreria (Rubiaceae) is the largest genus in tribe Spermacoceae sensu stricto, with about 100 species.It is distributed throughout the American continent from the southern United States to Uruguay and central Argentina.More than half of these species (69) occur in Brazil and 33 are endemic to it (Miguel & Cabral 2013;Miguel et al. 2015;Cabral & Salas 2015).For the Northeastern region, 27 species are recorded and 12 occur in Ceará state (Cabral & Salas 2015).Bacigalupo & Cabral (1996), studying American species of Borreria, recognized two subgenera (Borreria and Dasycephala), two sections (Borreria and Pseudodiodia), two subsections (Borreria and Latifoliae) and three series (Borreria, Brachystemonoides and Laeves) based on morphological data.Borreria subsect.Borreria is defi ned by the septicidal dehiscence of the fruit into two dehiscent mericarps, fl owers with exserted stamens and style, the stigma mainly bilobed and zonocolporate and pantoporate pollen grains.Within Borreria subsect.Borreria the series are defi ned only by seed morphology: Borreria ser.Borreria by reticulate seeds, Borreria ser.Brachystemonoides by seeds with an elaisome and Borreria ser.Laeves by ruminate seeds.
Th e delimitation of the genera Borreria and Spermacoce is confused and remains unclear.Some infrageneric groups of Bacigalupo & Cabral´s classifi cation (1996) seem not to be monophyletic.Th is has been made evident on phylogenetic studies for the tribe Spermacoceae, however those include a small number of species of Borreria sensu Bacigalupo & Cabral (1996) representing the American fl ora (nine species in Dessein 2003; fi ve in Kårehed et al. 2008;four in Groeninckx et al. 2009;eleven in Salas et al. 2015).Further molecular studies and a revision of the American species of Borreria are needed to assess whether these genera should be considered separate or merged into a wider, all-encompassing Spermacoce.But for the time being we follow the generic circumscription proposed by Bacigalupo & Cabral (1996).
Th e new species here described was found as result of the study of Rubiaceae for the regional fl ora of Ceará.It is only known in the Chapada do Apodi, on the border between

Materials and methods
This study is based on field observation and the study of collections from the herbaria CTES, EAC, HUEFS and HUVA (Thiers 2015).
Flower and seed samples were fixed in 70% alcohol, dried at critical-point, and sputter-coated with gold-palladium for scanning electron microscope (SEM) studies.
Pollen grains were obtained from anthers of one collection (Souza 3511).Samples for light microscopy (LM) were acetolyzed according to Erdtman (1966) and mounted in glycerin jelly.Polar axis and equatorial diameter were measured on 25 pollen grains using a Leica DM LB2 microscope.The terminology used to describe the pollen grains follows Punt et al. (2007).
Scanning Electron Microscope (SEM) images were taken from flowers, petals epidermis, stigma and acetolyzed pollen grains using a Jeol 5800 LV SEM at the Universidad Nacional del Nordeste, Corrientes, Argentina.
Phenology: All the specimens were collected from May to July with flowers and fruits.Etymology: The epithet 'apodiensis' refers to its distribution in Chapada do Apodi, where the species was collected.

Figure 1 .
Figure 1.A-C.Habitat and morphology of Borreria apodiensis. A. Calcareous rocks in Chapada do Apodi; B. Detail of a terminal glomerule and elliptic bracts; C. Detail of four cyathiform corollas.(A. by E.B. Souza; B-C. by E. Thomaz).