Migration pattern suggested by terrestrial proximity as possible origin of wild annual Helianthus populations in central Argentina

Abstract

There is a high interest to understand and recreate the invasive process of successful non-native plant invaders. The genetic tools provide scanty information when the invasion is recent and there is gene flow among the invader and its crop relative. The concern about the government and private companies' responsibilities in the diffusion process and the risk of occupancy of new areas motivated the interest in two wild annual Helianthus species naturalized in the central agricultural lands of Argentina. We used multivariate techniques and random tests to estimate the successive steps accomplished by the plant invaders across transportation routes, following an environmental and ecological gradient. A minimum connection tree through road distances was created considering dispersal from a unique dispersal point for each species. The proposed tree minimized, at the same time, the environmental and the ecological distances calculated by Euclidean and Gower indexes with abiotic and biotic habitat variables, being significantly different from random (P ≤ 0.05). Our methodology allowed the development of an approach for the best estimation of the invasion route. This could be used to clarify the role of different agents involved in the diffusion process and to develop management strategies to prevent the plant invasion. The migration pattern suggests that after their historical introduction, both wild species moved in successive steps across a biotic and abiotic gradient, aided by anthropogenic activity along the road connection infrastructure. There were no evidences of escapes from sunflower breeding stations.