The Strait of Gibraltar has been proposed to be the divide between two marine biogeographical regions, the Mediterranean Sea and the Northeast Atlantic. Intraspecific studies have shown, for several of the examined species, a reduction of gene flow between the two basins. The present study examines genetic variation at nuclear and mitochondrial loci in five marine teleost species belonging to the family Sparidae. Four samples for each species were analysed spanning the Northeast Atlantic and the Mediterranean. For all individuals 17 allozyme loci were scored and a combined single strand conformation polymorphism‐sequencing approach was used to survey approximately 190 bp of the mitochondrial DNA (mtDNA) D‐loop region. All five species share similar biological features. For three species, namely Lithognathus mormyrus, Spondyliosoma cantharus, and Dentex dentex, large mtDNA divergence was observed between Atlantic and Mediterranean samples. Little or no mtDNA differentiation was found in the other two species, Pagrus pagrus and Pagellus bogaraveo. Allozyme data revealed strong differentiation when comparing Atlantic and Mediterranean samples of L. mormyrus and D. dentex, moderate for P. pagrus, and no differentiation for P. bogaraveo and S. cantharus. These results provide evidence for a sharp phylogeographical break (sensu Avise) between the Atlantic and the Mediterranean for two (or possibly three) sparid species of the five investigated. At the same time, the obtained results for the other two species raise the question on which ecological/historical factors might have caused the observed discrepancy in the geographical distribution of genetic variation among otherwise biologically similar species.
SUMMARYIn marginal lands Opuntia ficus-indica (OFI) could be used as an alternative fruit and forage crop. The plant vigour and the biomass production were evaluated in Portuguese germplasm (15 individuals from 16 ecotypes) by non-destructive methods, 2 years following planting in a marginal soil and dryland conditions. Two Italian cultivars (Gialla and Bianca) were included in the study for comparison purposes. The biomass production and the plant vigour were estimated by measuring the cladodes number and area, and the fresh (FW) and dry weight (DW) per plant. We selected linear models by using the biometric data from 60 cladodes to predict the cladode area, the FW and the DW per plant. Among ecotypes, significant differences were found in the studied biomass-related parameters and several homogeneous groups were established. Four Portuguese ecotypes had higher biomass production than the others, 3.20 Mg ha−1 on average, a value not significantly different to the improved ‘Gialla’ cultivar, which averaged 3.87 Mg ha−1. Those ecotypes could be used to start a breeding program and to deploy material for animal feeding and fruit production.
In Opuntia spp., the cladode tissues contain many polysaccharides and secondary metabolites that interfere with obtaining high-quality deoxyribonucleic acid (DNA), using currently available methods. To circumvent this problem, three commercial kits, three modified versions of the conventional cetyltrimethylammonium bromide method (CTAB) method and one combined method were tested in Opuntia ficus-indica, O. robusta, O. dillenii and O. elata species. We obtained a rapid and simple protocol that allows the extraction of DNA from all the tested species with good DNA yield and purity, namely, the combined method. With this method (DNeasy® Plant Mini Kit combined with the CTAB method), DNA yields from 13.2 ± 7.8 to 15.9 ± 11.3 µg g of fresh tissue were obtained in the four Opuntia species. The purity, evaluated by the ratio A/A ratio, ranged from 1.67 ± 0.12 to 2.01 ± 0.25, revealing low levels of problematic metabolites. The extracted DNA quality was confirmed by amplifying a set of nuclear microsatellites obtained for the genus. Reliable reproducible bands and electropherogram profiles were obtained. The combined method has potential to be universal for good-quality DNA extraction in cacti, particularly in the Opuntia genus and other difficult-to-extract species.
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