Mikania micrantha Kunth, a climbing perennial weed of the family Asteraceae, is native to Latin America and is highly invasive in the tropical belt of Asia, Oceania and Australia. Achyut Kumar Banerjee and colleagues investigated the population structure of M. micrantha at a large spatial scale in Asia to identify how introduction history, evolutionary forces and landscape features influenced the genetic pattern of the species in this region.
The team found high genetic diversity of M. micrantha in this region, as compared with the genetic diversity parameters of other invasive species. The spatial and non-spatial clustering algorithms identified the presence of multiple genetic clusters and admixture between populations. Most of the populations showed heterozygote deficiency, primarily due to inbreeding, and the founder populations showed evidence of a genetic bottleneck. Persistent gene flow throughout the invasive range caused low genetic differentiation among populations and provided beneficial genetic variation to the marginal populations in a heterogeneous environment. Environmental suitability was found to buffer the detrimental effects of inbreeding at the leading edge of range expansion. Both linear and nonlinear regression models demonstrated a weak relationship between genetic distance and geographic distance, as well as bioclimatic variables and environmental resistance surfaces.
“Genetic diversity in the introduced range has been found as an important factor for invasion success of many invasive species, e.g. Lantana camara, Ambrosia artemisiifolia,” write Banerjee and colleagues. “Comparing the genetic diversity parameters with other invasive species, our study found higher expected and observed heterozygosity in M. micrantha, although with lower allelic richness. These estimates are comparable to regional studies of M. micrantha in its invasive range, and higher than those reported from its native range. However, drawing a comparative inference of genetic diversity between native and invasive ranges of this species is difficult since the sampled populations were collected from the northernmost limit of its native range that may not represent the source locations of our studied populations.
“To the best of our knowledge, this is the first study that investigated the population structure of M. micrantha at a large spatial scale in Asia,” the team add. “Given the species’ ability of long-distance dispersal primarily through human-mediated transfer of broken fragments and the extent of anthropogenic activities in this region [e.g. the proposed Belt and Road Initiative], further spread of the species in novel regions can be anticipated. In this context, the findings of our study emphasized continuous surveillance of anthropogenic activities to prevent new introductions and further spread of M. micrantha in this region.”The paper is available on one of the authors’ ResearchGate pages.