The role of habitat, landscape structure and residence time on plant species invasions in a neotropical landscape

Abstract

Abstract:Plant invasions in tropical agricultural landscapes have been poorly studied so far. Here, we use plot data collected in 2015 in the La Gamba valley in southern Costa Rica to analyse the spread of two invasive alien species (Hydrilla verticillata, Hedychium coronarium) on the landscape level. In total, we recorded the aquatic H. verticillata, which was locally introduced into the La Gamba valley in 2005, in 26% of all plots (size: 15 m2), while H. coronarium, which occurs along water courses, was recorded in 80% of all plots (size: 25 m2). Generalized Linear Models (GLMs) showed that the habitat type invaded and shading had no significant effect on H. verticillata presence and abundance. However, proximity to the point of local introduction and habitat diversity in the adjacent landscape did positively affect its presence. For H. coronarium, GLMs showed a significant correlation with the invaded habitat type. The probability of H. coronarium presence was highest in herbaceous vegetation and cover was higher compared with other habitats. There was no effect on native plant species richness and cover by H. verticillata, while H. coronarium exerted a negative impact on herbaceous plant species number and, in particular, cover. Hydrilla verticillata is a rather recent addition to the local alien flora, and thus dispersal limitation still restricts its local range. Compared with observed rates of spread in other regions, spread velocity within the first decade of its local presence was low. In contrast, H. coronarium has been locally present for a substantially longer time period. This species encounters suitable habitat conditions in herbaceous vegetation along water courses, where it builds up dense clonal stands which negatively affect herbaceous vegetation. Our results show that while both study species are invasive in Central American lowlands, their local abundance and impacts on native vegetation may differ profoundly.

Integrating management techniques to restore subtropical forests invaded by Hedychium coronarium J. Köenig (Zingiberaceae) in a biodiversity hotspot

“…The species was disseminated by human activities and is established in different biomes in Brazil, including the Cerrado, Caatinga, and Atlantic Forest (Zenni & Ziller 2011). Impacts include obstruction of water flow in channels, streams, and wetlands, and the displacement of native species as a consequence of fast vegetative growth (CABI 2014; Haider et al 2016). There are records of invasion for Hedychium species in pristine forests in Hawaii and the Reunion Islands, where seeds are dispersed by birds (Rejmánek 1996) that feed on the red aril.…”

“…This invasive species reproduces vegetatively by rhizomes, forming dense thickets (Kissmann & Groth 1997; Manish 2013). There is evidence that the shade originated by dense stands is a barrier to the establishment of saplings of native species (Haider et al 2016). Although information about the control of H. coronarium is available (Dechoum & Ziller 2013), studies focused on methods to restore the degraded habitat after invasion control are still missing.…”