Pisonia calafia (Nyctaginaceae) species nova from the Baja California Peninsula, Mexico

 

Pisonia calafia (Nyctaginaceae) especie nueva de la Península de Baja California, México

 

José Luis León de la Luz^1,3 and Rachel A. Levin²

 

¹Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Herbario HCIB, Apdo. postal 128, 23000 La Paz, Baja California Sur, México.

²Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA.

³Author for correspondence: jlleon04@cibnor.mx

 

Recibido en agosto de 2011.
Aceptado en marzo de 2012.

 

ABSTRACT

Pisonia is a primarily American genus, distributed mainly in subtropical to tropical regions. In this paper a new species, Pisonia calafia, is described and documented. This species occurs as a small population on a coastal strand in the Cape Region of the Baja California Peninsula. The main characteristics that differentiate P. calafia from the rest of Pisonia is the lack of sulci and glands in the fruit. In addition to the new species description, we discuss the evolutionary affinities of this new taxon based on phylogenetic analysis of nrITS sequence data. The known population is limited to a few dozen individuals, now seriously endangered by the ongoing development of tourism projects.

Key words: East Cape Region, Nyctaginaceae, Pisonia, phylogeny.

 

RESUMEN

El género Pisonia es primordialmente americano, se distribuye principalmente en regiones subtropicales y tropicales. En este trabajo se describe y documenta la nueva especie Pisonia calafia. Este taxon consiste de una relativamente pequeña población en la costa de la región de Los Cabos en la península de Baja California. La principal característica que diferencia a P. calafia del resto de las especies de este género es la carencia de sulcos y glándulas en el fruto. En adición a la descripción morfológica, se documenta la afinidad evolutiva del nuevo taxon con base en el análisis filogenético de la secuencia de nrITS. Las poblaciones conocidas consisten de unas pocas docenas de individuos, seriamente amenazados por el desarrollo de proyectos turísticos en la zona.

Palabras clave: Cabo del Este, filogenia, Nyctaginaceae, Pisonia.

 

Personnel of the herbarium at CIBNORhave been collecting plants in several areas of the Baja California Peninsula as part of their mission to compile a catalogue of the coastal flora. In 1997, an isolated vegetative specimen of a shrub (M. Domínguez 1694,1771) was found and identified tentatively as Pisonia sp., since the leaves were somewhat similar to plants of this genus; however, they did not match the two species of Pisonia that are known from Baja California: P. flavescens Brandegee and P. capitata (S. Wats.) Standl.

In the summer of 2009, a population of 30-40 plants of this still unknown species was located. This population was visited regularly until flowers and fruits were available for collecting and complete identification. Close morphological study revealed that both flower perianths, staminate (campanulate) and pistillate (urce-ollate), as well the inflorescences in headlike cymes, show affinity with Pisonia. However, compared to other described Pisonia species, the anthocarp anatomy is somewhat different, as the fruits are not ribbed (slightly sulcate when immature) and lack glands or warts. Another notable difference is that the fruit-supporting structures (peduncle and pedicels) are shorter than the same structures in the other peninsular species of Pisonia. Given these distinctive characteristics, the authors believe that this population should be considered a new species.

 

Pisonia calafia León de la Luz et Levin sp. nova (Fig. 1).

Frutex dioecius, confertus, spinescens, foliis ellipticis. Flores staminati 6-lobulati; flores pistillati in inflorescentiis densibus dispositi, 4-lobulati. Fructus dense velutinus, non glandularis, indehiscens, 1-seminatus, interne cotyledonibus plicatis.

Dense dioecious shrubs, erect, up to 4 m high, developing some stems from rootstocks, stems and branchlets grayish, secondary branchlets spreading in an opposite pattern at right angle; strong and straight spines 10 mm long, almost opposite in the new branchlets, absent in old stems. Leaves elliptic to broadly elliptic, 14 * 20 mm long, some cuneate at base, petioles 4-7 mm long in mature leaves, indumentum short velutinous when young, pubescent with age. Staminate inflorescences capitate, 10-12 flowered in a single raceme, peduncle to 10 mm long, pedicels up to 1 mm long; perianth campanulate, 6 mm long, 6-lobed, each lobe 1 mm long; stamens 6 alternate with perianth lobes, anthers bilocular, dorsifixed, elliptic < 1 mm diameter, extrorse, generally 1 or 2 reduced to staminodes; the fine filaments connate basally, borne at the base of a pistillode 3 mm long; lower part of the perianth reduced to 2 or 3 small involucral bracts; indumentum densely short velutinous. Pistillate inflorescences capitate, arranged in 2-5 racemes, each with 4-7 flowers, peduncles to 20 mm long, congested in anthesis, expanded after fertilization, pedicels short < 1mm long; involucre well differentiated 1-2 mm long, sacciform to urceolate in shape, very thick, with 4-5 lanceolated lobes < 1 mm long, bicolor, the basal half darker than the upper; stigma somewhat exserted, lobed and decurrent; lower part of the perianth consists of 4 lanceolate involucral bracts 1 mm long; indumentum densely short velutinous; no staminodes are present. Anthocarp, diclesium, or fruit elliptic, 10-12 x 7-8 mm, rounded at base, finely velutinous, coriaceous, indehiscent, with several parallel longitudinal lines, suggesting ancestral ribs; each fruit one-seeded, seed pisiform, 6-7 mm in diameter, black. In the plantlets, cotyledons unfold from a conduplicate position.

Type: México. Baja California Sur: delegación La Ribera, Laguna Grande, Las Lagunas, municipio de Los Cabos. 2.7 km al W del faro de Punta Arena, por la carretera costera de terracería, km 11 entre La Ribera y Cabo Pulmo, 23°32'01.72" N, 109°29'40.88" W, 2 June 2011, J. L. León de la Luz 11167 (holotype: HCIB 26596 (male), 26597 (female), isotypes to be distributed, CAS, ENCB, IEB, MEXU, RSA, SD, UC) .

Eponymy. The species epithet calafia was selected in honor of the beauty queen of the mythic California island, according to the book "Las sergas de Esplandián" written ca. 1510 by Garci Rodríguez de Montalvo, that supposedly inspired the conqueror Hernán Cortés to use the same name for the then recently discovered land (ca. 1535).

Related species. The mainly tropical genus Pisonia includes approximately 40 species, with the greatest species-richness in the Americas (Mab-berley, 1997). Only two species of Pisonia are previously known to inhabit the Baja California Peninsula: P. capitata and P. flavescens. The former occurs in the Sierra de la Giganta, a hundred kilometers from the type location of this new taxon. However, this species is more common in the dry tropical forest of Sonora, mainland northwestern México (Spellenberg, 2003). By contrast, P. flavescens is endemic to the tropical dry forest in the Cape Region of Baja California Sur. Table 1 shows the characteristics that can be used to differentiate between the Baja California Pisonia species, including this new taxon. Images of P. calafia are shown in Fig. 2.

 

Evolutionary affinities. To understand the evolutionary affinities of Pisonia calafia, we used the internal transcribed spacer region of nuclear ribosomal DNA, composed of ITS1, the 5.8S gene, and ITS2 (Baldwin, 1992; Baldwin et al., 1995). ITS is commonly employed in fine-scale studies of angiosperm relationships, and this region has been used for understanding relationships among closely-related species within Nyctaginaceae (Levin, 2000; Douglas and Manos, 2007). This region was amplified for one accession of Pisonia calafia (J. L. León-de la Luz 11167, type location), as well as an accession of P. flavescens, (León de la Luz s/n., Sierra Cacachilas).

Amplification was done using primers ITSleu1 (5-GTC CAC TGA ACC TTA TCA TTT AG-3'; Bohs and Olmstead, 2001) and ITSc26a (5'- GTT TCT TTT CCT CCG CT-3'; Wen and Zimmer, 1996). Twenty-five microliter reactions contained 1X buffer, 3.0 mM MgCl₂, 0.20 mM dNTPs, 0.40 µm of each primer, 1X Qiagen Q-solution (Qiagen, Valencia, CA), 0.625 units Taq polymerase, and 1µm DNA. Thermal cycler conditions included an initial denaturation at 94 °C for 3 min; 8 cycles at 94 °C for 30 s, 58 °C down to 52°C (decreasing 2 °C every two cycles) for 1 min, 72 °C for 1 min; 25 cycles at 94 °C for 30 s, 50 °C for 1 min, 72 °C for 1 min; ending with an extension at 72 °C for 10 min. PCR products were cleaned and sequenced following Levin et al. (2011) with the same primers used for amplification.

The two new sequences (Pisonia calafia and P. flavescens) were cleaned using Sequencher 4.7/4.8 (Gene Codes, 1991-2007). Consensus sequences from each of these species were manually aligned (SeAl v2.0a11 (Rambaut, 1996-2002)) to a larger data set of 18 taxa from within Pisonia and across Nyctaginaceae. The family-wide phylogenetic study of Douglas and Manos (2007) guided the choice of taxa to include. ITS sequences for these additional taxa were available from GenBank (accessions: EF079454-5, EF079463, EF079475-6, EF079484-6, EF079489-90, EF079493, EF079495-6, EF079498, EF079502, EF079505, DQ317077, AF212015).

The ITS dataset was analyzed using maximum likelihood, with substitution model parameters estimated using the Akaike Information Criterion in Modeltest 3.7 (Posada and Crandall, 1998). Maximum likelihood nonparametric bootstrap analysis was conducted using the estimated model parameters, 500 full heuristic bootstrap replicates, each with 10 random-addition sequence replicates and TBR branch-swapping; the MulTrees option was disabled. Maximum likelihood bootstrap analyses were conducted using PAUP* 4.0b10 for UNIX (Swofford, 2002) on the Condor (Anonymous, 2005) computer cluster at Amherst College. Bootstrap replicates were parsed for processing using RepMaker (Wilgenbusch, 2003). Given the results of Douglas and Manos (2007), Salpianthus arenarius was defined as the outgroup.

As shown in Fig. 3, our analysis strongly suggests that the new taxon belongs within Pisonia. The genus Pisonia (excluding P. rotundata) is well supported as monophyletic (Bootstrap (BS) = 99) . Within this clade, the pantropical P. aculeata + P. capitata + P. calafia are strongly supported as monophyletic (BS = 99), and P. calafia appears sister (BS = 70) to P. capitata. Although the new taxon is clearly within Pisonia, increased sampling of Pisonia species is needed to conclusively determine the closest relatives of P. calafia.

 

Ecology. From our field observations, some plants begin to develop flowers in June, usually the driest month, but most of the plants begin blooming just after the first heavy rain in August or September. Mature fruits were collected in November-January. At the location where 30-40 specimens were identified, no plantlet recruitment was observed. This location is at the end of a micro-basin; because there is no drainage to the sea, the micro-basin is temporarily inundated after heavy rains. A second population was found in the La Ribera arroyo, a few kilometers NW of the other site and has fewer plants than the first site. Both sites are at an elevation of 2-4 m above sea level on sandy and saline soil.

The type population grows in a coastal thorn scrubland; this vegetation type has not been previously documented in the Baja California Peninsula. Common species at the site were: Phaulotamnus spinescens A. Gray (Achatocarpaceae), Lycium brevipes Benth. (Solanaceae), Condalia globosa I.M. Jhtn. var. globosa (Rhamnaceae), Parkinsonia florida (Benth. ex A. Gray) S. Watson (Fabaceae), Randia capitata DC. (Rubiaceae), Stenocereus gummosus (Engelm.) A. Gibson et K.E. Horak (Cactaceae), and Ximenia parviflora Benth. var. glauca de Filipps (Ximeniaceae).

The Baja California flora (Wiggins, 1980) has almost 3000 species, subspecies, and varieties of vascular plants. The level of endemism is difficult to determine, given recent unpublished accounts (Rebman, pers. comm.). However, there are an estimated 800 endemic plant species on the Baja California Peninsula. Riemann and Ezcurra (2004), in an analysis of the spatial distribution of the peninsular endemics, stated that there are some "hot spots" of endemics in this region, and one of them is the Cape Region. It contains several plant communities, each with high endemism at generic, specific, and infraspecific levels (León de la Luz et. al., 1999). Peninsular endemism is attributed to historical vicariance events during its geological separation from the Mexican mainland and recurrent glacial-postglacial colonizations (Nason et al., 2002).

Given the limited number of individuals, low apparent level of recruitment, and restricted geographic range, the outlook for the continued persistence of P. calafia is not good. As numerous tourism projects are also under development in this area, this new taxon should be considered for IUCN and Mexican enviromental law in critically endangered status.

 

ACKNOWLEDGMENTS

We are grateful to Fernando Chiang Cabrera (MEXU) for the Latin translation, Danira León Coria prepared the illustrations, and Ira Fogel of CIBNOR made editorial improvements. We appreciate the courtesies extended by the herbarium curators of MEXU and RSA. We also greatly appreciate the participation of HCIB colleagues Raymundo Domínguez, Miguel Domínguez, and Alfonso Medel. We thank the anonymous reviewers of Acta Botanica Mexicana and CONABIO project HJ-007 for funding.

 

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