Background: Coastal ecosystems in Mexico remain understudied in spite of their ecological, economic and conservation value and are being impacted by human activities along the coast. Knowledge on spatial patterns of plant species distribution that helps preserve these fragile ecosystems is crucial. Aims: We evaluated differences in species richness, species diversity and species dominance patterns in 16 plant communities as well as the degree to which differences were driven by climatic conditions in sandy dunes in Yucatán. We evaluated the importance of invasive species in mediating patterns of species diversity and species dominance patterns. Results: We found wide variation in plant species richness, species diversity and species dominance patterns among communities that stems from broad climatic differences along dune systems. Invasive plants represent almost one-third of total species richness and seem to be drastically changing the species dominance patterns in these communities. Conclusions: Regional climatic differences along the Yucatán north coast seems to be a major driver of plant diversity and species composition. Our findings suggest that invasive plants have successfully colonised and spread along the coast over the past 30 years. Even though invasive species do not alter spatial patterns of species diversity, they are becoming more dominant with potential detrimental consequences for native plants.

We performed a phylogenetic analysis using maximum parsimony and Bayesian inference of three plastid DNA markers and the external transcribed spacer (

Resumen. Salivazo o mosca pinta aplica a varias especies de insectos de la familia Cercopidae, que constituyen una importante plaga de la caña de azúcar (Saccharum sp.) en el trópico mexicano, las cuales suelen completar su ciclo de vida en otras plantas que se desarrollan como arvenses. El objetivo de esta investigación fue identificar las especies de mosca pinta y de arvenses hospederas de éstas, confinando 127 ninfas, de las que se colectaron 76 adultos, 51 de Aeneolamia contigua Walker, y 25 de Prosapia simulans Walker, localizadas en 13 especies de plantas arvenses. La mayor abundancia de especies de mosca pinta se encontró en Paspalum fasciculatum, Rottboellia cochinchinensis, y Pennisetum purpureum. Aeneolamia contigua se reporta por primera vez en Panicum laxum, Pennisetum setaceum y Urochloa fusca, y Prosapia simulans en U. fusca y Synedrella nodiflora, esta última es el primer registro de una planta que no es Poaceae. Spittlebug apply to more than one species of insects of the Cercopidae family, an important pest of sugarcane (Saccharum sp.) plantations in the Mexican tropics, which typically complete their life cycle in other plants that grow like weeds. The aim of this research was to identify both spittlebugs and their host weed species by confining 127 nymphs on exclusions of wire and mesh; 76 adult spittlebugs were captured, 51 Aeneolamia contigua Walker and 25 Prosapia simulans Walker, in 13 species of weeds. The most abundant species was found in Paspalum fasciculatum, Rottboellia cochinchinensis, and Pennisetum purpureum. Aeneolamia contigua is reported for the first time in Panicum laxum, Pennisetum setaceum, and Urochloa fusca and Prosapia simulans in U. fusca and Synedrella nodiflora.

Muhlenbergia torreyi occurs in the southwestern United States, northern Mexico, and northwestern Argentina. Allozyme data were used to evaluate genetic diversity within and among populations of this amphitropical disjunct species. Electrophoretic examination of 22 putative enzyme loci in 15 populations revealed high levels of genetic variation (P ranging from 64.7 to 82.4;H from 0.527 to 0.757) and high levels of genetic diversity (F ranging from −0.584 to −0.939). All populations possess high levels of heterogeneity (F _1S approaching −1, mean of −0.837) and exhibit lower levels of genetic fixation among populations (F _ST mean of 0.127). A comparison of genetic identity values among populations from North and South America indicates that the genetic variation is slightly greater (I=0.93) in North America than in South America (I=0.96). A total of 51 alleles were shared among all populations, and four unique alleles were detected: two from North American populations and two from South America. It seems likely thatMuhlenbergia torreyi has dispersed to South America recently, because the populations there are less variable. Chromosome numbers, not determined by the authors, of 2n=20, 21 forM. torreyi and 2n=80, 82 forM. arenicola are reported.Muhlenbegia arenicola is first reported from South America. Muhlenbergia torreyi habita en el suroeste de Estados Unidos, norte de México, y noreste de Argentina. Mediante el análisis de alozimas se evaluó la diversidad genética dentro y entre poblaciones de esta especie, que es disjunctiva anfitropical. El exámen electroforético de 22 loci putativos enzimáticos en 15 poblaciones, reveló altos niveles de variación genética (P varía de 64.7 a 82.4;H varía de 0.527 a 0.757) y altos niveles de diversidad genética (F varía de −0.584 a −0.939). Todas las poblaciones poseen altos niveles de heterogeneidad dentro de las mismas poblaciones (F _IS cerca −1, media de −0.837) y exhiben bajos niveles de fijación genética entre poblaciones (F _ST media de 0.127). Una comparación de valores de identidad genética entre poblaciones de Norte y Sudamérica indican que la variación genética es un poco mayor (I=0.93) en Norte América que en Sudamérica (I=0.96). Las poblaciones poseían un total de 51 alelos en común y se detectaron cuatro alelos únicos; dos en las poblaciones norteamericanas y dos en las poblaciones sudamericanas. Probablemente,Muhlenbergia torreyi ha sido dispersada recientemente hacia Sudamérica porque esta poblacion es menos variable. El número de cromosomas, no determinado por los autores, de 2n=20, 21 paraM. torreyi and 2n=80, 82 paraM. arenicola son reportados.Muhlenbergia arenicola es reportada por primera vez en Sudamérica.