No abstract

Ferocactus histrix is a barrel cactus that is widespread in Mexico. A population located inLlanos de Ojuelos, a semiarid zone representative of many disturbed regions in northcentral Mexico, was studied. Over a period of 10 years (1997 to 2007), the average number of individuals decreased from 21.95 to 3.53 plants per 300 m 2 . A change in population size structure was also registered over this period of time. In 2008, a plot selected on the basis of plant abundance was established within the population and a genetic analysis was conducted with ISTR and ISSR markers. This analysis revealed low levels of genetic diversity (expected heterozygosity (HE) = 0.073, Shannon index (I) = 0.113 and HE = 0.178, I = 0.271, respectively) compared with those of most studied cacti species. The genetic diversity between the different life stages was also evaluated, and a gradual decrease in levels of genetic variation was observed from adults to juveniles and seedlings ( HE = 0.130, I = 0.192 to HE = 0.103, I = 0.157). These differences, however, were not significant. Loci fixation and a decrease in the frequency of rare alleles were observed in seedling and juvenile classes. The decline in genetic variation may be associated with recent bottlenecks experienced by the population of F. histrix. If the sizes of local populations of F. histrix continue to decrease, genetic variation will be gradually lost, and the risk of extinction will increase.

No abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama, is native to Asia but has recently invaded North America. Asian citrus psyllid is a significant pest of citrus crops by its direct feeding but, more importantly, as the vector of the bacterium ‘Candidatus Liberibacter asiaticus’, which causes Huanglongbing disease. Asian citrus psyllid was first found in México in 2001 and 2002 and, since then, has spread quickly across the country, suggesting rapid adaptation to new environments. Yet, we lack information on the genetic variation and structure that could facilitate or inhibit adaptation. Using six microsatellite markers, we analyzed genetic variation and structure among six localities in México: three in western states near the Pacific coast and two in the Yucatán Peninsula near the Gulf of México. We found low genetic diversity (no more than three alleles per locus) and intermediate differentiation between all populations. Asian citrus psyllid populations clustered into two genetic groups, but, surprisingly, these clusters were present in western populations. The first group included El Arenal, and the second group included Autlán de Navarro, Colima, and Tecomán. Interestingly, both of the Yucatán populations shared variation from the two clusters, suggesting admixture. We infer that reproductive isolation, barriers to gene flow, local selection, and the possibility of multiple invasions have influenced the current genetic structure of Asian citrus psyllid in México.

A new Mexican leafhopper species, Amblysellus raygozai sp. nov., is described and illustrated from western Mexico. Specimens were collected over perennial grasses. A key for all recognized species within the country is provided.