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Polyploid origins in Gynostemma pentaphyllum (Cucurbitaceae) inferred from multiple gene sequences
Ling-Yan Jiang1, Zeng-Qiang Qian, Zhi-Gang Guo
1Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Northwest University, Xi'an 710069, PR China.
Molecular Phylogenetics and Evolution
|March 19, 2009
Summary
Polyploidization is key to Gynostemma evolution, particularly in G. pentaphyllum. Studies show autoploid origins for its polyploids, suggesting this mechanism drives diversification despite limited geographic range expansion.
Area of Science:
- Plant evolutionary biology
- Genetics and genomics
- Phylogenetics
Background:
- The genus Gynostemma (Cucurbitaceae) features perennial herbs where polyploidization is a significant evolutionary factor.
- Gynostemma pentaphyllum exhibits the most diverse cytotypes (2n=22, 44, 66, and 88) and is the most widespread species within the genus.
Purpose of the Study:
- To investigate the origins of polyploids in Gynostemma pentaphyllum.
- To understand the role of polyploidization in the evolutionary diversification and geographic distribution of G. pentaphyllum.
Main Methods:
- Phylogenetic analyses were conducted using sequences from plastid intergenic spacers (trnL-trnF, psbB-psbF, rpl20-rps12).
- Cloned DNA sequences from two nuclear regions (RPB2 and nrDNA ITS) were analyzed.
- Phylogenetic analyses utilized separate and combined nuclear gene datasets.
Main Results:
- Phylogenetic analyses strongly supported autoploid origins for polyploids in G. pentaphyllum.
- Three polyploid populations showed closer relationships, indicating genetic differentiation between diploid and polyploid individuals.
- Chloroplast DNA (cpDNA) variation was minimal, with only the octoploid DL 8x exhibiting a distinct haplotype.
Conclusions:
- Polyploidization appears to be a crucial mechanism driving the diversification of G. pentaphyllum.
- The distribution of cytotypes in G. pentaphyllum deviates from typical autopolyploid complexes, with polyploidization not significantly expanding its geographic range.
- The geographic distribution of diploids and polyploids may be linked to past ecological conditions, particularly during glacial periods.
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