Abstract
A new species of Heteranthera (Pontederiaceae), H. yucatana, is described, discussed, and iconographically documented based on material from Yucatan state, Mexico. The species is known from a few small ponds along a narrow strip of dry forests and shrublands over limestone outcrops and derived soils along the northwestern edge of the Yucatan Peninsula. The new species is related and has been hitherto confused with H. seubertiana from eastern Brazil but is easily distinguishable by its substantially smaller habit and flowers. Furthermore, the perianth lobes are lilac with a white-greenish basal blotch with yellowish towards the apex (as opposed to yellow lobes with proximal brownish spots). Also, the two lateral filaments are conspicuously inflated obliquely, as in Heteranthera mexicana, from which it differs by its much smaller vegetative size and some floral characters. The conservation status of the new species is assessed as Endangered according to the IUCN criteria. The genus Heteranthera consists of three species in the Yucatan Peninsula: H. dubia, H. limosa, and H. yucatana. Distributional maps for all Heteranthera from the area covered are presented. Finally, we offer a key to Heteranthera of the area.
References
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<p>Bachman, S., Moat, J., Hill, A., Torre, J. & Scott, B. (2011) Supporting Red List threat assessments with GeoCAT: geospatial conservation assessment tool. <em>ZooKeys </em>150: 117–126. https://doi.org/10.3897/zookeys.150.2109</p>
<p>Bentham, G. (1840) <em>Plantas Hartwegianas</em>. Imprimis Mexicanas. G. Pamplin. London. pp. 25.</p>
<p>Carnevali, G., Ramírez-Morillo, I. & González-Iturbe, J.A. (2003) Flora y vegetación de la Península de Yucatán. <em>In</em>: Colunga-GarcíaMarín, P. & Larqué-Saavedra, A. (Eds.) <em>Naturaleza y Sociedad del Área Maya: Pasado, Presente y Futuro</em>. Centro de Investigación Científica de Yucatán, A.C. Mérida, Yucatán, México. pp. 53–68.</p>
<p>Carnevali, G., Duno, R., Tapia Muñoz, J.L. & Ramírez, I.M. (2010) Reassessment of <em>Zephyranthes</em> (Amaryllidaceae) in the Yucatán Peninsula including a new species, <em>Z. orellanae</em>. <em>Journal of the Torrey Botanical Society</em> 137 (1): 39–48. https://doi.org/10.2307/2666625</p>
<p>Carnevali, G., Trejo-Torres, J.C., Juárez-Jaimes, V., Duno, R., Tapia-muñoz, J.L., Ramírez-morillo, I.M. & Cetzal-IX, W. (2016) <em>Marsdenia calichicola</em><strong> </strong>(Apocynaceae), a narrow endemic, endangered new species from the Mexican Yucatan Peninsula. <em>Phytotaxa</em> 270 (2): 17. https://doi.org/10.11646/phytotaxa.270.2.7</p>
<p>Carnevali, G., Ramírez-Morillo, I., Pérez-Sarabia, J.E., Tapia-Muñoz, J.L., Estrada Medina, H., Cetzal-IX, W, Hernández-Aguilar, S., Can Itza, L.L., Raigoza Flores, N.E., Duno de Stefano, R. & Romero-González, G.A. (2021) Assessing the risk of extinction of vascular plants endemic to the Yucatán Peninsula Biotic Province by means of distributional data. <em>Annals of the Missouri Botanical Garden </em>106: 424–457. https://doi.org/10.3417/2021661</p>
<p>Durán, R., Campos, G., Trejo, J.C., Simá, P., May Pat, F. & Juan-Qui, M. (2000) <em>Listado florístico de la Península de Yucatán</em>. Centro de Investigación Científica de Yucatán. Mérida, Yucatán, México. 259 pp.</p>
<p>ESRI (2011) <em>ArcGIS Desktop</em>: Release 10. Redlands, CA: Environmental Systems Research Institute.</p>
<p>Fassett, N. (1955) <em>Echinodorus</em> in the American tropics. <em>Rhodora</em> 57 (677): 133–156. https://doi.org/10.1525/aa.1955.57.1.02a00180</p>
<p>Faegri, K. & van der Pijl, L. (1979) <em>The principles of Pollination Ecology</em>. Pergamon Press. New York, USA. 244 pp. https://doi.org/10.1016/B978-0-08-023160-0.50020-7</p>
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<p>Gutiérrez Báez, C. (2000) <em>Listado Florístico actualizado del estado de Campeche, México</em>. Universidad Autónoma de Campeche. Campeche. 95 pp.</p>
<p>Gutiérrez Báez, C. (2006) <em>Lista de especies de plantas acuáticas vasculares de la península de Yucatán, México</em>. <em>Polibotánica</em> 21: 75–87. [http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-27682006000100075&lng=es&tlng=es]</p>
<p>Hooker, S.D. (1887) On <em>Hydrothrix</em>, a new genus of Pontederiaceae. <em>Annals of Botany, Oxford</em> 1: 89−94. https://doi.org/10.1093/oxfordjournals.aob.a089056</p>
<p>Hooker, W.J. & Greville, R.K. (1830 [1829]) <em>Icones Filicum</em>. Vol. 2. Treuttel & Würtz, Treuttel Fil. & Richter etc., London.</p>
<p>Horn, C.N. (1985) <em>A systematic revision of the genus Heteranthera </em>(<em>sensu lato</em>; Pontederiaceae). Ph.D. thesis, University of Alabama, Tuscaloosa, USA.</p>
<p>Horn, C.N. (2002) Pontederiaceae<em> In</em>: Flora of North America Editorial Committee (Eds.) <em>Flora of North America,</em> <em>Vol. 26.</em> Oxford University Press, Oxford, New York, U.S.A. pp. 37–46. [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10722]</p>
<p>IUCN (2010) IUCN Red List of Threatened Species. Version 2010.3. (http:// www.iucnredlist.org. Downloaded on 05 April 2020)</p>
<p>Koehne, B.A.E. (1900) Lythraceae novae. <em>Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie</em> 29 (1): 154–160.</p>
<p>Kunth, K.S. (1816) <em>Nova Genera et Species Plantarum</em> (quarto ed.) vol. 1: Lutetiae Parisiorum, Sumtibus Librariae Graeco-Latino-Germanicae</p>
<p>Kunth, K.S. (1843) <em>Enumeratio Plantarum Omnium Hucusque Cognitarum</em>. Vol. 4. Stutgardiae et Tubingae. 752 pp.</p>
<p>Jacquin, N.J. von. (1768) <em>Observationum Botanicarum</em>. Vol. 3. Officina Krausiana, Viena, 22 pp.</p>
<p>JSTOR Global Plants (2021) Available from: https://plants.jstor.org (accessed 5 April 2020)</p>
<p>Linnaeus, C. (1753) <em>Species Plantarum. </em>vol. 1. Holmiae. Laurentii Salvii. 559 pp.</p>
<p>MacMillan, C. (1892) <em>The Metaspermae of the Minnesota Valley</em> 138: 1−826.</p>
<p>Martius, K.F.P. von (1823) Nova <em>Genera et Species Plantarum</em>. Munich, published by the author.</p>
<p>McVaugh, R. (1987) <em>Flora Novo-Galiciana: A Descriptive Account of the Vascular Plants of Western Mexico. Vol. 5: Leguminosae</em>. University of Michigan. 786 pp.</p>
<p>Mears, J.A. (1982) A summary of <em>Blutaparon</em> Rafinesque including species earlier known as <em>Philoxerus</em> R. Brown (Amaranthaceae). <em>Taxon</em> 31 (1): 111–117. https://doi.org/10.2307/1220598</p>
<p>Miller, P. (1768) <em>The Gardeners Dictionary: containing the best and newest methods of Cultivating and Improving the Kitchen, Fruit, and Flower Garden, and Nursery; also for Performing the Practical Parts of Agriculture: including the Management of Vineyards</em>, ... The Eighth Edition, .... Printed for the Author, London, unpaged. https://doi.org/10.5962/bhl.title.541</p>
<p>Mora-Olivo, A., Villaseñor, J.L. & Martínez, M. (2013) Las plantas vasculares acuáticas estrictas y su conservación en México. <em>Acta Botanica Mexicana</em> 103: 27–63. https://doi.org/10.21829/abm103.2013.50</p>
<p>Novelo, A. & Lot, A. (1994) 252. Pontederiaceae. <em>In</em>: Davidse, G., Sousa, M. & Chater, A.O. (Eds.) <em>Flora Mesoamericana, vol. 6, Alismataceae a Cyperaceae</em>. Universidad Nacional Autónoma de México, México. pp. 65–71.</p>
<p>Olmsted, I., Durán, R., González-Iturbe, J.A., Granados, J. & Tun, F. (1999) Vegetación. <em>In</em>: García de Fuentes, A. & Córdoba, J. (Eds.) <em>Atlas de procesos territoriales de Yucatán</em>. Facultad de Arquitectura, Universidad Autónoma de Yucatán, Mérida, Yucatán, México. 255 pp.</p>
<p>Pellegrini, M. (2016) Two new synonyms in <em>Heteranthera</em> (Pontederiaceae, Commelinales). <em>Nordic Journal of Botany</em> 35 (1): 124−128. https://doi.org/10.1111/njb.01152</p>
<p>Pellegrini, M. & Horn, C.N. (2017) Two peculiar new species of <em>Heteranthera</em> Ruiz & Pavón (Pontederiaceae) from Brazil, with notes on inflorescence architecture in the family. <em>PhytoKeys</em> 82: 35–56. https://doi.org/10.3897/phytokeys.82.13752</p>
<p>Pellegrini, M., Horn, C.N. & Almeida, R.F. (2018) Total evidence phylogeny of Pontederiaceae (Commelinales) sheds light on the necessity of its recircumscription and synopsis of <em>Pontederia</em> L. <em>PhytoKeys</em> 108: 25–83. https://doi.org/10.3897/phytokeys.108.27652</p>
<p>Presl, C.B. (1827) <em>Reliquiae Haenkeanae Pragae</em>. Vol. 1. Apud J. G. Calve bibliopolam, Pragae. 356 pp.</p>
<p>Presl, C.B. (1830) <em>Symbolae Botanicae, sive, Descriptiones et icones plantarum novarum aut minus cognitarum</em>. Vol. 1. Praga, umtibus auctoris E. Typographia J. Spurny. 30 pp. https://doi.org/10.5962/bhl.title.12413</p>
<p>Ruiz López, H. & Pavón, J.A. (1794) <em>Flora Peruviana, et Chilensis</em>. Vol. 1. Prodromus, Imprenta Gabrielis de Sancha, Madrid. 456 pp.</p>
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