Chromolaena odorata has become an invasive weed in the humid tropics and subtropics. In the introduced habitats, C. odorata was observed to exhibit two biotypes, i.e. Asian/West African (AWA) biotype and the southern African (SA) biotype. Despite different attributes between the two biotypes, surprisingly little is known about their genetic variability and relatedness.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted an extensive phylogeographic study using chloroplast and nuclear DNA sequences and microsatellite DNA markers. They aimed to characterize the genetic variability and identify the likely source regions in the native distributions of the two biotypes of invasive C. odorata.
The researchers employed both chloroplast and nuclear DNA sequences and SSR analyses on C. odorata samples collected from its global distribution including both native and invasive regions.
They built a genetic dataset by sequencing 140 samples (with additional 247 samples from their previous study) for two cpDNAs (psbA-trnH and atpB-rbcL), one rDNA (ITS5p-ITS8p), and by genotyping six microsatellite loci.
The analysis of both DNA sequences and nuclear markers showed that native populations possessed high genetic diversity, while both the AWA and SA biotypes in invaded regions appeared to have low genetic diversity.
Their results, based on extensive samples coverage and various analyses, confirmed the presences of two distinguishable genotypes of C. odorata in its invaded ranges.
The results suggest that agents from Cuba and Jamaica where SA biotype are present, and from other native regions with dry and cold microenvironment similar to habitats invaded by C. odorata are needed for biocontrol of SA biotype in South Africa.
The study entitled “On the origin and genetic variability of the two invasive biotypes of Chromolaena odorata” has been published in Biological Invasions.
LI Qiaoming Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China