Abstract
The discovery and characterization of informative intraspecific genetic markers is fundamental for evolutionary and conservation genetics studies. Here, we used nuclear ribosomal ITS sequences to access intraspecific genetic diversity in 23 species of the genus Passiflora L. Some degree of variation was detected in 21 of these. The Passiflora and Decaloba (DC.) Rchb. subgenera showed significant differences in the sizes of the two ITS regions and in GC content, which can be related to reproductive characteristics of species in these subgenera. Furthermore, clear geographical patterns in the spatial distribution of sequence types were identified in six species. The results indicate that ITS may be a useful tool for the evaluation of intraspecific genetic variation in Passiflora.
Highlights
Understanding the distribution of alleles throughout the geographic range of a species is fundamental for molecular evolutionists, allowing inferences about the influence of historical processes in the spatial distribution of particular lineages (Emerson et al, 2001)
As in this study we presented an overview of ITS genetic diversity in Passiflora species as a whole, rather than an exhaustive analysis of just a few species, it could be argued that the somewhat limited, and to some extent, unequal sampling of the different species may tend to bias our estimates
These results indicate that the values presented here for nucleotide diversity are independent of sampling artifacts, and may be viewed as approximations of the level of genetic diversity in these species
Summary
Understanding the distribution of alleles throughout the geographic range of a species is fundamental for molecular evolutionists, allowing inferences about the influence of historical processes in the spatial distribution of particular lineages (Emerson et al, 2001). Even though the use of ITS as a molecular marker might be problematic because of paralogy and other complex evolutionary patterns caused by its highly repetitive nature (Alvarez and Wendel, 2003), the general evolutionary mechanism for this region proposes that most intragenomic copies would share identical sequences as a result of concerted evolution, a homogenizing process that depends on unequal crossing over during meiosis and biased gene conversion (Dover, 1994; Liao, 1999). We found general differences in ITS structure between the two most speciose subgenera (Passiflora and Decaloba), besides identifying geographic associations among lineages in at least six species
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