From where, how and how many times? History of the invasion of Senecio madagascariensis (Asteraceae) in South America.

COULLERI, JUAN PABLO; BREM, MARTA CAROLINA; MAYER, JOAQUÍN; ROBLEDO DOBLADEZ, GERMÁN A.

Puerto Iguazú

Simposio; XVI International Symposium on Biological Control of Weeds; 2023

ISBCW

Senecio madagascariensis commonly named fireweed, is a southern Africa native species, recognized as invasive in Australia, south-east Asia, South America and the Hawaiian Islands. This species occurs in roadsides, fallows, wastelands and anthropized areas. Anindividual of S. madagascariensis can produce up to 18.000 seeds that are dispersed by wind. Unfortunately, these plants contain pyrrolizidine alkaloids that cause cumulative chronic liver damage and fatality, especially in monogastric livestock. Phylogeographic and population genetic analyses can provide important insights into the dynamics of biological invasions by elucidating geographical source(s), dispersal route(s), spread and the roles of evolutionary processes in invasion success. Thus, in order to have a more comprehensive understanding of the invasion of S. madagascariensis in southern South America, we aimed a) to clarify the origin of introduced genotypes and b) determine the genetic diversity and the structure of the invasive populations. To achieve our goals, we used a genetic characterization with internal transcribed spacer (ITS) from 57 populations belonging to Argentina and Brazil and 26 others populations? available in Gene bank belonging to different parts of the world of both native and invasive range. We analyzed the haplotype and nucleotide diversity and an AMOVA among collection sites. The evolutionary relationships among the sequences were performed, sequences of S. inaequidens from GenBank were used as outgroup. In addition, we used 8 microsatellite markers in 342 individuals for the 57 populations through which the genetic diversity was estimated using the parameters: number of alleles, allelic richness, expected and observed heterozygosity, deviations of the genotype frequencies Hardy-Weinberg equilibrium and the inbreeding coefficient (FIS). Moreover, the relationships between geographic and genetic (FST) distances among populations were tested at the structure and scale of geographic differentiation among populations. The phylogeographic results indicate that the Argentinian populations are originating from South Africa, while the Brazilian one represent diverse provenances. These results become more relevant with the evidence from population genetic studies from which Argentinian populations are represented by only one deme, whereas the populations that are present in Brazil are split into 2 demes represented by populations that occurred in the center of the distribution area and the other deme is represented in the coastal area of the country.