Mario Vázquez-Torres

Utility of AFLP markers for the assessment of molecular relationships in Ceratozamia Brongn. (Zamiaceae)

Abstract The genus Ceratozamia has a distribution from Mexico to Central America. Molecular relationships were explored among Mexican Ceratozamia species using variable molecular markers, namely Amplified Fragment Length Polymorphisms (AFLP). Three AFLP primer-combinations generated 77 loci for a total of 1,684 fragments. Molecular variation was 75.72% among species and 24.28% within species, and a low correlation was present between genetic and geographical distances. Cluster analysis produced a phenogram in which two distinct clusters are clearly recognizable, one including C. alvarezii, C. sabatoi, C. zaragozae, C. kuesteriana, C. mexicana and C. robusta, and another one with C. zoquorum, C. miqueliana, C. latifolia, C. microstrobila, C. hildae and C. morettii. The AFLP proved to be suitable to study the relationships among species of Ceratozamia, and the results corroborated those from previous morphology-based studies.

Plastid DNA sequencing and nuclear SNP genotyping help resolve the puzzle of central American Platanus.

BACKGROUND AND AIMS Recent research on the history of Platanus reveals that hybridization phenomena occurred in the central American species. This study has two goals: to help resolve the evolutive puzzle of central American Platanus, and to test the potential of real-time polymerase chain reaction (PCR) for detecting ancient hybridization. METHODS Sequencing of a uniparental plastid DNA marker [psbA-trnH((GUG)) intergenic spacer] and qualitative and quantitative single nucleotide polymorphism (SNP) genotyping of biparental nuclear ribosomal DNA (nrDNA) markers [LEAFY intron 2 (LFY-i2) and internal transcribed spacer 2 (ITS2)] were used. KEY RESULTS Based on the SNP genotyping results, several Platanus accessions show the presence of hybridization/introgression, including some accessions of P. rzedowskii and of P. mexicana var. interior and one of P. mexicana var. mexicana from Oaxaca (= P. oaxacana). Based on haplotype analyses of the psbA-trnH spacer, five haplotypes were detected. The most common of these is present in taxa belonging to P. orientalis, P. racemosa sensu lato, some accessions of P. occidentalis sensu stricto (s.s.) from Texas, P. occidentalis var. palmeri, P. mexicana s.s. and P. rzedowskii. This is highly relevant to genetic relationships with the haplotypes present in P. occidentalis s.s. and P. mexicana var. interior. CONCLUSIONS Hybridization and introgression events between lineages ancestral to modern central and eastern North American Platanus species occurred. Plastid haplotypes and qualitative and quantitative SNP genotyping provide information critical for understanding the complex history of Mexican Platanus. Compared with the usual molecular techniques of sub-cloning, sequencing and genotyping, real-time PCR assay is a quick and sensitive technique for analysing complex evolutionary patterns.

Cyanobacterial mats from the Carrizal, a geothermal spring pool in Mexico

Cyanobacterial microflora is very diverse in different habitats over the world and closely connected with the ecology of the habitat. In particular, extreme habitats are colonised by numerous specialised morpho- and ecotypes which are unique to these ecologically specialised environments. A variety of methods are needed to characterize cyanobacterial assemblages in thermal water environments. We report here on the community structure of the cyanobaterial mats at the hot spring of the alkaline ad low sulphide artificial pool of “Carrizal” (Villa Emiliano Zapata, Mexico). The most common organisms were Anabaena sp., Phormidium sp. and Pseudoanabaena sp. Some filamentous cyanobacteria showed a 98%-95% 16S rDNA gene similarity with Oscillatoria sp. and cluster together with other filamentous cyanobacteria from the thermal environments.