Premise Recent phylogeographic work suggests the existence of latitudinal gradients in genetic diversity in northern Mexican plants, but very few studies have examined plants of the Chihuahuan Desert. Tidestromia lanuginosa is a morphologically variable annual species whose distribution includes the Chihuahuan Desert Region. Here we undertook phylogeographic analyses of chloroplast loci in this species to test whether genetic diversity and differentiation of Mexican populations of T. lanuginosa change along a latitudinal gradient and whether diversity is higher in Coahuila, consistent with ideas of lower plant community turnover during the Pleistocene. Methods Haplotype network, maximum likelihood tree, and Bayesian phylogenetic haplotype were reconstructed, and genetic diversity was assessed among 26 populations. Barrier analysis was used to explore barriers to gene flow. Results Four major population groups were identified, corresponding with physiographic provinces in Mexico. Each population group displayed high levels of genetic structure, haplotype, and nucleotide diversity. Diversity was highest in southern populations across the species as a whole and among the Chihuahuan Desert populations. Conclusions Tidestromia lanuginosa provides an important example of high phylogeographic and genetic diversity in plants of northern Mexico. Barriers to gene flow among the major population groups have most likely been due to a combination of orographic, climatic, and edaphic variables. The high genetic diversity of T. lanuginosa in southern and central Coahuila is consistent with the hypothesis of full‐glacial refugia for arid‐adapted plants in this area, and highlights the importance of this region as a center of diversity for the Chihuahuan Desert flora.
Antecedentes y Objetivos: El amaranto es de interés mundial por su valor nutricional como verdura y grano. Las especies cultivadas de mayor importancia comercial por su producción de grano son Amaranthus caudatus, A. cruentus y A. hypochondriacus. Dos hipótesis aceptadas sobre el origen de A. cruentus consideran a A. hybridus como su ancestro. Los objetivos del presente estudio son 1) reportar la distribución actualizada y frecuencia de A. cruentus y A. hybridus en el sureste de México, Guatemala y Honduras y 2) evaluar su diversidad morfológica mediante caracteres florales y del fruto de ambas especies en México y Guatemala.Métodos: La información proveniente de 147 ejemplares de herbario fue empleada para actualizar la distribución y frecuencia de A. cruentus y A. hybridus en la zona de estudio, posible área de domesticación. La diversidad a nivel morfológico se determinó del análisis de 22 caracteres relacionados a estructuras de flores pistiladas y del fruto, usando un análisis multivariado de componentes principales y evaluando para ello 15 ejemplares de A. cruentus y 31 de A. hybridus procedentes de Guatemala y el sureste de México.Resultados clave: La mayor distribución de A. cruentus se presentó en Guatemala y, en el caso de A. hybridus en México. La variación acumulada en los tres primeros componentes principales fue de 58% para ambas especies. La variación morfológica para las dos especies se asoció principalmente con caracteres relacionados a los sépalos internos y externos. El gráfico del análisis de componentes principales permite observar una amplia variación morfológica en A. cruentus y A. hybridus, independiente de su distribución geográfica en ambos casos.Conclusiones: La distribución geográfica de A. cruentus en México es más amplia con respecto a reportes previos. Se describe la diversidad morfológica de estructuras de flores pistiladas y frutos en A. cruentus y A. hybridus.
Renzaglia is recorded for the first time in Mexico, North America, extending its distribution range considerably to the North. Recording distribution ranges could aid to better understand ecological and biogeographical patterns, and detailed population level descriptions of wide-range distributing hornworts could be helpful in determining intraspecific variation, which in turn would aid to define species limits, nowadays poorly understood in Anthocerotophyta Stotler & Crandall-Stotler. Anatomical and morphological characters of collected plants are described in details and illustrations in light microscopy and SEM are provided. P. fimbriatus can be distinguished from other Mexican hornwort species by spore ornamentation, antheridial number per chamber, number of layers of spore tissue in the sporophyte and presence of band-like thickenings in cells of gametophyte thallus. Mexican plants of P. fimbriatus presented smaller spores (28-36 µm in diameter, average 34 µm) than those previously reported (32-43 µm in diameter) for this species, which extends the species variation range of this character and might be pointing out geographical variation.
In a recent trip to southern Mexico, Anthoceros subtilis and A. telaganus were recorded for the first time in Mexico and the American continent. Several previous records of A. subtilis were from Asia and one from Africa, and A. telaganus is known only from Indonesia. The new range extension of these two species is reported and the species are described and illustrated. Mexican populations of A. subtilis are characterized by small brown spores (26–42 μm), similar ornamentation on proximal and distal spore surfaces with papillate to tuberculate projections. Anthoceros telaganus is characterized by larger black spores (32–53 μm) with a smooth strip along the trilete mark on the proximal surface. Molecular genetic sequencing is needed to test whether Asian and American populations of these morphologically similar but geographically disjunct taxa are conspecific.
Notothylas flabellata is reported for the first time in Mexico and North America, previously known only from Argentina in the American continent. This species was originally described from Africa. This species is characterized by absence of columella, dark brown to black tuberculate spores with distal hump-like globular projections and sub-quadrate to rectangular pseudoelaters with brown spiral-annular bands. In North America, this species might be confused with N. breutelii, but it can be differentiated by the presence of a columella in N. breutelii, and spore and pseudoelater ornamentation. Light microscopy photographs of N. flabellata and N. breutelii are provided. The new record increases the species number of Notothylas in North America to four.
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