Studies in the Neotropical Apocynaceae LI : a new species of Laubertia ( Apocynaceae ) from Brazil

A new species of Laubertia from Brazil supported by morphological characters and molecular data is described and illustrated. Laubertia brasiliensis sp. nov. is closely related to L. contorta from northern Mesoamerica and Mexico, but differs by its straight corolla tube, whereas L. contorta has a spirally contorted corolla tube. A key to the species of Laubertia is also provided. Resumen. Se describe e ilustra una nueva especie de Laubertia de Brasil de acuerdo con caracteres morfológicos y datos moleculares. Laubertia brasiliensis sp. nov. está estrechamente relacionada con L. contorta del norte de Mesoamérica y México, pero tiene el tubo de la corola recto, a diferencia de L. contorta, que lo tiene retorcido en espiral. Se incluye también una clave para las especies de Laubertia. Morales F.J. 2017. Studies in the Neotropical Apocynaceae LI: a new species of Laubertia (Apocynaceae) from Brazil. Anales Jard. Bot. Madrid 74 (2): e063. https://doi.org/10.3989/ajbm.2484 Title in Spanish: Estudios sobre Apocynaceae neotropicales LI: una nueva especie de Laubertia (Apocynaceae) de Brasil. Received: 17‒VII‒2017; accepted: 15‒IX‒2017; published online: 01‒XII‒2017; Associate Editor: J.M. Cardiel.


INTRODUCTION
Laubertia A.DC. -Apocynaceae Juss.-grows in tropical and subtropical regions of Mexico, Guatemala, and Belize, and from Colombia to Bolivia.It is composed of woody vines with milky sap, cymose inflorescences with scarious bracts, sepals without colleters at the base of the adaxial surface, corolla with an annular corona around the mouth, the tube without free corona lobes within, corolla lobes totally reflexed towards the tube during the anthesis, moniliform follicles and truncate seeds, comose at the micropylar end (Morales 2002(Morales , 2009)).The first revision of Laubertia was conducted by Woodson (1936), who accepted four species, three of them restricted endemisms: L. peninsularis Woodson, L. pringlei (Greenm.)Woodson, and L. sanctae-martae (Rusby) Woodson, whereas L. boissieri A.DC. was known only from four collections from Ecuador and Peru.Shortly after, Woodson (1938) proposed L. contorta (M.Martens & Galeotti) Woodson, and reduced L. pringlei into the synonymy of that species.The most recent study (Morales 2002), accepted three species: L. boissieri -including L. sanctae-martae-, L. contorta, and L. peninsularis.
The research of phylogenetic relationships of tribe Echiteae Bartl.(Morales & al. 2017), and the revision of specimens for the Flora of Brazil (Morales in prep.)revealed a new species endemic to the Amazon basin supported by molecular data and morphological characters, which represents the first record of Laubertia for the country.This paper aims to describe this new species, including an illustration and a key to the currently accepted species of Laubertia.
Distribution and habitat.-Endemic to Brazil to the states of Para and Amazonas, growing in river margins and igarapó forest, from 100 to 200 m a.s.l.
Phenology.-Floweringoccurs in February and July and fruiting in July.

DISCUSSION
Laubertia was placed in the subtribe Prestoniinae Pichon ex M.E.Endress (Endress 2014), together with Hylaea J.F.Morales, Prestonia R.Br., and Rhodocalyx Müll.Arg., which have in common annular coronas around the corolla mouth or free corona lobes opposite to the anthers (Woodson 1936;Morales 1997Morales , 1999;;Morales & Liede-Schumann 2016).Based on the presence of an annular corona around the mouth, Laubertia had been considered as sister of Prestonia (Woodson 1936;Morales 2002), but the evidence provided by molecular data (Morales & al. 2017) showed that these genera are not even closely related and both are nested in different subtribes -Laubertinae J.F.Morales, M.E.Endress & Liede and Prestoniinae.
Laubertinae comprises Hylaea and Laubertia.The latter can be recognized from the former by its sepals without colleters on the base of the adaxial surface -vs.sepals with one colleter at the base of the adaxial surface-, corolla with an annular corona around the mouth -vs.annular corona absent-and corolla tube without free corona lobes within -vs.tube with free corona lobes.Morales & al. (2017) published a phylogenetic study of the tribe Echiteae based on plastid -trnLF, matKintron K, rpl16-and nuclear data -ITS-, in which L. brasiliensis sp.nov.was treated as Laubertia sp.nov.According to that study, L. brasiliensis sp.nov. is closely related to L. contorta from Mexico and northern Central America but differs by its tube corolla, not twisted, and disjunct geographical distribution.Laubertia brasiliensis sp.nov.may be distinguished from L. boissieri by its shorter inflorescences, smaller corolla lobes -lobes 8-9 mm vs. 10-18 mm-, and seeds with a smaller apical comma -0-9 mm vs. 2.5-4.8cm.