Going with the flow: analysis of population structure reveals high gene flow shaping invasion pattern and inducing range expansion of Mikania micrantha in Asia

Abstract

Background and Aims Mikania micrantha, 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. This study was framed to investigate the population structure of M. micrantha at a large spatial scale in Asia and to identify how introduction history, evolutionary forces and landscape features influenced the genetic pattern of the species in this region. Methods We assessed the genetic diversity and structure of 1052 individuals from 46 populations for 12 microsatellite loci. The spatial pattern of genetic variation was investigated by estimating the relationship between genetic distance and geographical, climatic and landscape resistances hypothesized to influence gene flow between populations. Key Results We found high genetic diversity of M. micrantha in this region, as compared with the genetic diversity parameters of other invasive species. 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 non-linear regression models demonstrated a weak relationship between genetic distance and geographical distance, as well as bioclimatic variables and environmental resistance surfaces. Conclusions These findings provide evidence that extensive gene flow and admixture between populations have influenced the current genetic pattern of M. micrantha in this region. High gene flow across the invaded landscape may facilitate adaptation, establishment and long-term persistence of the population, thereby indicating the range expansion ability of the species.

Population Genomics Reveals Gene Flow and Adaptive Signature in Invasive Weed Mikania micrantha

“…Consistent with this, we detected a high rate of gene flow (1.63 ≤ N m ≤ 62.25) among M. micrantha populations. Similarly, a high rate of gene flow has been found among populations within the Asian invasion range [33], indicating that M. micrantha population invasion is accompanied by a high rate of gene flow.…”

“…In this study, obvious heterozygote deficiency was detected in M. micrantha across populations and regions. This is understandable, considering that M. micrantha has experienced severe founder effect and genetic bottlenecks during rapid colonization and invasion [33,69]. Inbreeding is a genetic trait observable in some invasive species [4] that can give rise to heterozygote deficiency within populations [70].…”

“…micrantha spread rapidly throughout southern China following its introduction to the Hong Kong Zoological and Botanical Gardens in 1884 [29]. The role of genetic and epigenetic variations in the population expansion of M. micrantha in southern China has been investigated in several genetic studies, all of which used a small number of anonymous genomic markers [30][31][32][33][34][35]. Nevertheless, the available population genetic data failed to provide a comprehensive understanding of the genetic status and adaptive response of M. micrantha populations.…”

Founder effects shape linkage disequilibrium and genomic diversity of a partially clonal invader

“…LD is also important to generating genotype-phenotype correlations that help to understand the genetic basis of phenotypic evolution (Lowry et al, 2016). When a population undergoes a bottleneck, fewer genomes exist in subsequent generations resulting in high correlation between variant loci as seen in crop domestication (Ching et al, 2002;Maccaferri et al, 2005) and the invasive weed, Mikania micrantha (Banerjee et al, 2020;Wang et al, 2007). LD will be further increased if the bottleneck severely reduces population size (Wall et al, 2002).…”

Genetic Differentiation and Phylogeography of Rotifer Polyarthra Dolichoptera and P. Vulgaris Complexes Between Southern China and Eastern North America: High Intercontinental Differences

“…The IBD pattern, respecting the association between genetic and geographic distances, is common in many plants (e.g. Rhododendron spp, Mikania micrantha) and even the single-celled phytoplankton cyanobacteria (Banerjee et al, 2020 ;Ribeiro et al, 2020 ;Zhang et al, 2020). For heterotrophic protists (unicellular eukaryotes) such as Noctiluca scintillans, an intercontinental spatial barrier (the Paci c Ocean) seems to impose a limitation on gene ow and induces an increase in genetic distance (Pan et al, 2016).…”