A novelty in Ceratozamia (Zamiaceae, Cycadales) from the Sierra Madre del Sur, Mexico: biogeographic and morphological patterns, DNA barcoding and phenology

Abstract

Ceratozamia is a genus of cycads occurring in eastern Mexico and Central America. In this study, we describe a new species from the Pacific region of Mexico in Guerrero state. This locality represents the most northwestern Mexico distribution for the genus. We focus the comparison of this species with the most geographically proximate and phenotypically relevant lineages for this taxon. We followed an integrative taxonomy approach to evaluate the classification of these species, including geographic location, morphology, DNA barcoding and phenology as primary sources of systematic data. Within the morphological dataset, reproductive structures are described in detail and new characters are proposed for microsporophylls. The comparative morphology of these structures facilitated the elucidation of differences in forms and species for identification. The two chosen DNA barcoding markers – namely, the chloroplast genome coding region matK and the nuclear ribosomal internal transcribed spacer (ITS) region – had low divergence, allowing only 61% of species identification, suggesting slow molecular evolutionary rates. Besides employing these three basic sources of evidence, we introduced phenology as additional information for species circumscription. In addition, this work includes a brief review of the genus at the species-level. This is therefore the most recent review for Ceratozamia across its full geographic range (latitudinal and elevational). Overall, this work further contributes to a comprehensive framework for systematic studies in Mexican cycads.

Ceratozamia aurantiaca (Zamiaceae): A New Cycad Species from the Northern Rainforests of Oaxaca, Mexico

“…Qualitative traits were also observed to identify differences among the three species (Table 2). Ceratozamia leptoceras has been suggested by some workers to be closely related to C. robusta [9], and it was compared to the other three species using qualitative data from its original description. Seven vegetative traits were measured in adult plants (Table 3).…”

“…in the states of Chiapas, Oaxaca, and Veracruz (Mexico), as well as in Guatemala and Belize (Figure 1). Although all populations from these regions share the aforementioned suite of morphological characteristics, a high level of variation among populations of C. robusta sensu lato was previously noted [5] and has only been carefully examined in recent years [7,9,10].…”

“…in the states of Chiapas, Oaxaca, and Veracruz (Mexico), as well as in Guatemala and Belize (Figure 1). Although all populations from these regions share the aforementioned suite of morphological characteristics, a high level of variation among populations of C. robusta sensu lato was previously noted [5] and has only been carefully examined in recent years [7,9,10]. Martínez-Domínguez et al [7] (2016) demonstrated that populations from the Los Tuxtlas region of Veracruz, historically recognized as Ceratozamia robusta, were significantly differentiated from other populations of C. robusta.…”

“…& Lorea-Hern. [9]. Close inspection of morphological variation among populations in Chiapas (Mexico) and Belize revealed that the populations from the Chiapas Highlands (Los Altos de Chiapas), historically recognized as C. robusta, represented yet another different species, C. sanchezae Pérez-Farr., Gut.Ortega & Vovides [10], which has a closer morphological resemblance to the C. miqueliana species complex than to C. robusta.…”

“…Dyer, or C. robusta (according to determinations on herbarium specimens deposited in MEXU, SERO, and HEM), was discovered near the hydroelectric dam "Presa Miguel Alemán" in the Sierra Norte region of Oaxaca (Mexico). [9]. Close inspection of morphological variation among populations in Chiapas (Mexico) and Belize revealed that the populations from the Chiapas Highlands (Los Altos de Chiapas), historically recognized as C. robusta, represented yet another different species, C. sanchezae Pérez-Farr., Gut.Ortega & Vovides [10], which has a closer morphological resemblance to the C. miqueliana species complex than to C. robusta.…”