The species of Mentzelia (Loasaceae) in Mexico, part 2: Mentzelia section Bartonia

keywords: Chihuahuan Desert, desert flora, plant taxonomy, Sonora Desert


Background: Mentzelia (Loasaceae) is primarily distributed in western North America. The genus is classified into six monophyletic sections, among which species of section Bartonia are particularly poorly understood.

Questions: What species of Mentzelia section Bartonia occur in Mexico? What are the species distribution ranges and what are their defining attributes?

Study species: Mentzelia section Bartonia.

Methods: Field, herbarium, distribution, and scanning electron microscopy studies were conducted to assess species diversity. Seed coat microsculpture patterns were evaluated to confirm species identities and understand their distributions throughout Mexico.

Results: Six species from section Bartonia were recognized, with taxa distributed into either the Chihuahuan or Sonoran deserts. Mentzelia longiloba var. pinacatensis is the only Mexican endemic.

Conclusions: Although this work comprehensively addressed the species of section Bartonia in Mexico, two groups will continue to present identification challenges: the M. longiloba and M. mexicana-M. saxicola complexes. Overlapping and variable characters will continue to complicate species identification in the M. longiloba complex, while the late-season loss of primary leaves will obscure species identification between M. mexicana and M. saxicola.


Download data is not yet available.
The species of <em>Mentzelia</em> (Loasaceae) in Mexico, part 2: <em>Mentzelia</em> section <em>Bartonia</em>


Brokaw J, Schenk JJ, Prigge BA. 2012. Mentzelia. In: Baldwin BG, Goldman DH, Vorobik LA, eds. The Jepson Manual: Vascular Plants of California. Berkeley, Calif: University of California Press. ISBN: 0520253124 9780520253124

Felger RS. 2000. Flora of the Gran Desierto and Río Colorado of Northwestern Mexico. Tucson, Arizona: University of Arizona Press. ISBN: 0816520445

Holmgren NH, Holmgren PK. 2002. New mentzelias (Loasaceae) from the Intermountain Region of western United States. Systematic Botany 27: 747-762. DOI:

Holmgren NH, Holmgren PK, Cronquist AR. 2005. Intermountain Flora, vascular plants of the Intermountain West, USA. New York: New York Botanical Gardens Press. ISBN: 9780893274696

Hufford L, McMahon MM, Sherwood AM, Reeves G, Chase MW. 2003. The major clades of Loasaceae: Phylogenetic analysis using the plastid matK and trnL-trnF regions. American Journal of Botany 90: 1215-1228. DOI:

Hufford L, Schenk JJ, Brokaw J. 2016. Mentzelia. In: Flora of North America Editorial Committee. Flora of North America North of Mexico. New York and Oxford: Flora of North America Association, p. 496-498. ISBN: 0190643722

Prigge BA. 1993. Mentzelia. In: Hickman JC, editor. The Jepson Manual: Vascular Plants of California. Berkeley, Calif.: University of California Press. ISBN: 0520253124 9780520253124

Rios N, Bart H. 2010. GEOLocate (Version 3.22). Belle Chasse, LA: Tulane University Museum of Natural History. (accessed June 8, 2019).

Schenk JJ, Granados Mendoza C, Estrada-Castillón AE. 2021. The species of Mentzelia (Loasaceae) in Mexico, part 1: Sectional diversity. Botanical Sciences 91: in press.

Schenk JJ, Hufford L. 2011a. Taxonomic novelties from Western North America in Mentzelia section Bartonia (Loasaceae). Madroño 57: 246-260. DOI:

Schenk JJ, Hufford L. 2011b. Phylogeny and taxonomy of Mentzelia section Bartonia (Loasaceae). Systematic Botany 36: 711-720. DOI:

Schenk JJ, Hufford L. 2020. A phylogenetic monograph of Mentzelia section Bartonia (Loasaceae). Systematic Botany Monographs 110: 1-239. ISBN: 1943751102, 9781943751105

Schenk JJ, Sullivan MT, Washburn GA, Chambers ML. 2016. Allometric relationships better explain seed coat microsculpture traits in Mentzelia section Bartonia (Loasaceae) than ecology or dispersal. International Journal of Plant Sciences 177: 263-276. DOI:

Sosa V, De-Nova JA, Vásquez-Cruz M. 2018. Evolutionary history of the flora of Mexico: Dry forests cradles and museums of endemism. Journal of Systematics and Evolution 56: 523-536. DOI:

Thiers B. 2020. Index Herbariorum: A global directory of public herbaria and associated staff. <> (accessed May 18, 2019).

Thompson HJ, Powell AM. 1981. Loasaceae of the Chihuahuan Desert region. Phytologia 49: 16-33.

Thompson HJ, Zavortink JE. 1968. Two new species of Mentzelia in Texas. Wrightia 4: 21-24.

Turner B, Hempel A. 1995. A new species of Mentzelia (Loasaceae) from Nuevo León, Mexico. Phytologia 79: 298-300.

Villaseñor JL. 2016. Checklist of the native vascular plants of Mexico. Revista Mexicana de Biodiversidad 87: 559-902. DOI:

How to Cite
Schenk, J., Granados Mendoza, C., & Estrada-Castillón, A. E. (2021). The species of Mentzelia (Loasaceae) in Mexico, part 2: Mentzelia section Bartonia. Botanical Sciences, 99(4), 897-909.