Molecular characterization of the invasive aquatic macrophyte Hydrilla verticillata (Hydrocharitaceae) in Brazil

Abstract

Invasive populations of macrophytes are widely distributed and have been successfully introduced and established in freshwater habitats. Hydrilla verticillata was first recorded in 2005 in the Upper Paraná River floodplain and in 2007 at the Itaipu Reservoir (Brazil-Paraguay border, ca. 300 km downstream from its first record). However, its genetic variability within different sites in South America is unknown. We used nucleotide sequences corresponding to the trnL-trnF fragment cpDNA to genetically characterize populations of H. verticillata in different ecosystems of the Upper Paraná River basin. The results indicated an absence of genetic differentiation within and between populations of the basin, and even individuals collected 600 km apart belonged to the same haplotype. Moreover, H. verticillata populations of the Upper Paraná River basin also matched the dioecious biotype haplotype of the Southern United States and Asia. The identification of this single haplotype suggests that one founder genotype was introduced and established successfully in the Upper Paraná River basin, then, as a consequence of vegetative reproduction and the dispersal of propagules, spread to different habitats. However, firm conclusions about this inference can only be obtained with markers of biparental inheritance.

Low genetic diversity in an African invasive Poaceae in Brazil

“…As noted in previous studies, it is common for introduced populations to show lower genetic diversity in the introduced area when they do not experience environmental pressures (Lucio et Our results point out that propagule dispersal is a likely means of reproduction of this species and this could explain the high frequency of a unique haplotype for both markers. In cases where the pattern of low variability occurs, besides being indicative of the presence of a single founder genotype, it may also indicate that the maintenance of the population occurs through vegetative reproduction and dispersal of propagules to different locations (Lucio et al 2019). In addition to clonal reproduction, we speculate that the introduction of a small number of individuals may also help to explain the low genetic variability found within a given population.…”

“…The correct identi cation of invasive aquatic plant species and information on their genetic variability are fundamental to understanding the mechanism of invasion (Naugzemyz et al 2021) and implementing management strategies, as well as research into potential control agents, including biological ones (Pitelli et al 2008). Molecular tools have been useful for the correct identi cation and analysis of genetic variability in macrophyte populations, including Urochloa in the Upper Paraná River basin (Machado et al 2016;Lucio et al 2019;Diamante et al 2020) and in other watersheds (Collevatti et al 2003;Cloutier et al 2005;Azevedo et al 2008). A previous study with U. arrecta in Itaipu reservoir (Brazil) showed a high degree of genetic homogeneity among populations in this ecosystem (Diamante et al 2020).…”