A palynological study and molecular analysis of the Desmodium procumbens group (Leguminosae-Papilionoideae) in Mexico

Abstract

Desmodium diversity has been mainly classified using fruit characters, and because of variability in these and other characters, the taxonomy has sometimes been problematic and thus, there is a need for clarification and taxonomic reassessments. This is the case for the Desmodium procumbens group, where several infraspecific taxa have been named. The phylogenetic relationships among taxa referred to this group is unknown, and the taxonomic status has been recently revised only for some of the taxa. In this study, pollen morphology and ultrastructure of D. neomexicanum, D. procumbens var. procumbens, D. procumbens var. exiguum, D. procumbens var. longipes and D. procumbens var. transversum, belonging to the Mexican Desmodium procumbens group, were examined using light, phase-contrast, scanning electron and transmission electron microscopy, in order to establish palynological characters that might contribute to a better taxonomic resolution. Pollen grains are tricolporate, radiosymmetric, oblate spheroidal to prolate spheroidal shape, with lalongate endoapertures and rugulate exine with foveolae between rugulae. The exine is tectate with a columellate and/or granulate structure. The absence of a fastigium, features of exine sculpture, a colpus membrane and infrastructure mainly dominated by granules differentiate the pollen grains of the varieties exiguum and transversum from the other taxa studied. Pollen traits and sequence data provide evidence for separating D. neomexicanum from species D. procumbens. In general, the result from the pollen analysis is congruent with results obtained from a preliminary molecular analysis of this group.

Keywords:

• Desmodium
• Fabaceae
• Mexico
• taxonomy
• pollen morphology

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Erratum

Acknowledgements

This study was supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT) under the Project 168383 and a scholarship to RG-V. The authors are grateful to two anonymous reviewers that greatly improved the manuscript and to D. Piñero, J. S. Sotuyo and M. Pérez, UNAM, for tutoring and guidance. Special thanks to the staff of the Laboratorio de Palinología, Instituto de Geología, UNAM, and the Laboratorio de Microscopía Electrónica, Facultad de Ciencias, UNAM, to Berenit Mendoza from the Laboratorio de Microscopía Electrónica y Fotografía de la Biodiversidad, Instituto de Biología, UNAM, for technical advice; also to S. H. Ponce Wainer, Mexico City, Mexico, for revising and proofreading the final English version. This paper is based largely on the MSc thesis completed by RG-V as a student of the Posgrado en Ciencias Biológicas, UNAM.

Disclosure statement

No potential conflict of interest was reported by the authors.

Specimens investigated

Pollen samples

Desmodium procumbens (Mill.) Hitchc. Mexico: Morelos, Jojutla. R. González V. 806, 29 September 2011 (MEXU); Morelos, Jojutla. R. González V. 829, 30 September 2011 (MEXU); Veracruz, Xalapa. R. Cruz Durán & C. Ramos 5393, 2 November 2001 (MEXU).

Desmodium procumbens var. exiguum (A.Gray) B.G.Schub. Mexico: Morelos, Jojutla. R. GonzálezV. 826a, 30 September 2011 (MEXU); Morelos, Jojutla. R. González V. 827, 30 September 2011 (MEXU); Morelos, Jojutla. R. González V. 860b, 30 September 2011 (MEXU).

Desmodium procumbens var. longipes (Schindl.) B.G.Schub. Mexico: Guerrero, Acapulco. S. D. Koch, P. A. Fryxell & T. Went 79218, 31 October 1979 (MEXU); Jalisco, Estipac. M. Sousa & B. G. Schubert 1962a, 27 September 1963 (MEXU); Michoacán, José Sixto Verduzco. E. Pérez & E. García 1825, 19 September 1990 (MEXU).

Desmodium procumbens var. transversum (B.L.Rob. et Greenm.) B.G.Schub. Mexico: Morelos, Jojutla. R. González V. 818d, 29 September 2011 (MEXU); Morelos, Jojutla. R. González V. 824, 30 September 2011 (MEXU); Morelos, Jojutla. R. González V. 829, 30 September 2011 (MEXU).

Desmodium neomexicanum A.Gray. Mexico: Jalisco, Arandas. R. Mc.Vaugh 13260, 29 September 1952 (MEXU); Nuevo León, Iturbide. A. Eduardo Estrada 1513, 15 June 1989 (MEXU); Sonora, Yecora. T.R. Van Devender 2003-1127, 30 September 2003 (MEXU).

Molecular samples

Desmodium heterocarpon (L.) DC. GQ413942.1 TNM S138550

Desmodium procumbens (Mill.) Hitchc. Mexico: Jalisco, Autlán. R. González V. 874, 26 October 2012 (MEXU); Jalisco, Chamela. R. González V. 903, 27 October 2012 (MEXU); Michoacán. JC. Soto 16755 (MEXU); Querétaro, Cadereyta. A. Delgado S. 2804, 24 November 2012 (MEXU).

Desmodium procumbens var. exiguum (A.Gray) B.G.Schub. Mexico: Jalisco, Estipac. R. González V. 870, 25 October 2012 (MEXU); Jalisco, Autlán. R. González V. 877, 26 October 2012 (MEXU); Jalisco, Chamela. R. González V. 901, 27 October 2012 (MEXU); Jalisco, Chamela. R. González. V. 902, 27 October 2012 (MEXU); Morelos, Jojutla. R. González V. 833, 29 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 838, 29 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 855, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 860, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 862, 30 September 2011 (MEXU).

Desmodium procumbens var. longipes (Schindl.) B.G.Schub. Mexico: Jalisco, Autlán. R. McVaugh 19775 (MEXU); Jalisco, Autlán. R. González V. 893, 26 October 2012 (MEXU); Morelos, Jojutla. R. González V. 837, 29 September 2011 (MEXU).

Desmodium procumbens var. transversum (B.L.Rob. et Greenm.) B.G.Schub. Mexico: Jalisco, Chamela. R. González V. 905, 27 October, 2012 (MEXU); Morelos, Jojutla. R. González. V. 831, 29 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 844, 29 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 850, 29 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 858, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 859, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 865, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 866, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 867, 30 September 2011 (MEXU); Morelos, Jojutla. R. González. V. 868, 30 September 2011 (MEXU).

Desmodium neomexicanum A.Gray. Mexico: Durango. A. Benítez 2788 (MEXU); Querétaro, Cadereyta. C. Orozco 10358 (MEXU).

Desmodium triflorum (L.) DC. Mexico: Puebla. Tlatlaquitepec. J. L. Contreras 5973 7 October 1998 (MEXU).

Hylodesmum podocarpum (DC.) H.Ohashi et R.R.Mill GU572166.1 B.H. Choi 9810.