Phylogenetic and morphological analyses of Pilosocereus leucocephalus group s.s. (Cactaceae) reveal new taxonomical implications

Abstract

Pilosocereus is one of the Cactaceae family’s most relevant genera in terms of the number of species and its wide geographical range in the Americas. Within Pilosocereus, five informal taxonomic groups have been recognized, one of which is P. leucocephalus group s.s., whose phylogenetic relationships remain unresolved. Therefore, our objectives are to recognize the circumscriptions of the species in P. leucocephalus group s.s. and to corroborate the monophyly and phylogenetic relationships of this group through a set of morphological and molecular characters. This study is based on representative sampling along the broad distribution of this group in Mexico and Central America using multivariate and phylogenetic analyses. The morphological characters identified to contribute to species recognition and group formation are branch diameter, areole length, the areole length-width ratio, the distance between areoles, the length of the longest radial spine, and branch and spines colors. The chloroplast markers rpl16, trnL-trnF, and petL-psbE and the nuclear marker AT1G18270 support the monophyly of the P. leucocephalus group s.s., and two probable synapomorphies are suggested, including one transversion in rpl16 and another in petL-psbE. Together, our results demonstrate that sampled species of P. leucocephalus group s.s. encompass six species distributed in Mexico and Central America: P. alensis and P. purpusii in the western region, P. chrysacanthus and P. collinsii in the central region, and P. gaumeri and P. leucocephalus in the eastern region. A taxonomic key to recognized species is provided.

Revisiting phylogeny, systematics, and biogeography of a Pleistocene radiation

“…Molecular phylogenetic studies within this clade have suggested the statement of P . leucocephalus s.s. group, although the relationships within this group remain unknown (Franco‐Estrada et al, 2022). Previous phylogenies inferred a closer relationship among non‐Brazilian species and a clade with several northeastern Brazil taxa ( P. glaucochrous , P. pachycladus subsp.…”

“…These non-Brazilian species are distributed in North and Central America (P. leucocephalus and P. purpusii), the Antilles (P. polygonus and P. royenii), and the northern Andes (P. lanuginosus) (Figure 3). Molecular phylogenetic studies within this clade have suggested the statement of P. leucocephalus s.s. group, although the relationships within this group remain unknown (Franco-Estrada et al, 2022). Previous phylogenies inferred a closer relationship among non-Brazilian species and a clade with several northeastern Brazil taxa (P. glaucochrous, P. pachycladus subsp.…”

“…The Pilosocereus species have been arranged into five informal groups (P. ARRABIDAE, P. AURISETUS, P. LEUCOCE-PHALUS, P. PENTAEDROPHORUS, and P. PIAUHYENSIS; hereafter capitalized according to their original description), which are defined by habit, variations in floral morphology, spine morphology, and patterns of ribs (Figure 1; Zappi, 1994;Hunt et al, 2006). However, this informal grouping has been challenged by recent molecular phylogenetic inferences, though the alternative relationships proposed generally show low phylogenetic support (Calvente et al, 2017;Lavor et al, 2019Lavor et al, , 2020Franco-Estrada et al, 2022). Many factors may have contributed to the taxonomic challenges in Pilosocereus, such as recent radiation (Lavor et al, 2019), multi-episodic population isolation and admixture (Bonatelli et al, 2014;Perez et al, 2016a), traits varying independently according to precipitation and latitude (Menezes et al, 2015), and pronounced local morphological differentiation of disjunct populations (Zappi, 1994).…”

Lista anotada de cactus nativos y naturalizados de Cuba

“…brooksianus se ajustan a la descripción de P. polygonus. El reciente estudio de Franco-Estrada et al (2022) no pudo discriminar los límites entre las especies de Pilosocereus cubanos muestreados, por lo que siguen siendo necesarios estudios adicionales, tanto filogenéticos como morfológicos.…”

“…Dichos tratamientos o inventarios varían entre 29 y 50 taxones nativos, incluidos en 15 -17 géneros (Tabla 1). Pese a que la última década ha sido prolífera en estudios filogenéticos en cactáceas con base en caracteres moleculares donde se han incluido especies cubanas (Hernández-Hernández et al 2011, Majure et al 2013, Franck et al 2013, Korotkova et al 2017, Franco-Estrada et al 2022, Sánchez et al 2022, no siempre los inventarios han considerado las implicaciones taxonómicas y nomenclaturales que dichos estudios han aportortado. También en este periodo han aparecido varios estudios morfológicos que han contribuido a resolver la delimitación entre especies de cactáceas cubanas (Barrios & GonzálezTorres 2015, Franck et al 2019, Lemus-Barrios et al 2021, Barrios et al 2022a.…”