Effect of shade on Antigonon leptopus (Corallita) growth and germination rate

MSc. thesis

An experimental research conducted in Saba (Dutch Caribbean) as a potential control method for Corallita

Non-native species can cause loss of biological diversity and threaten society’s well-being when they become invasive. One of the most problematic invasive species currently affecting the Dutch Caribbean islands is a plant called Corallita (Antigonon leptopus). This non-native species, originally from Mexico, was introduced to the Caribbean islands at the beginning of the twentieth century as an ornamental plant. But the plant quickly expanded beyond its area of introduction and, once established, it is difficult to eliminate due to the production of tuberous roots that can propagate vegetatively. 

The Caribbean islands are of great importance to the world’s biodiversity. In the Nature Policy plan for the Caribbean Netherlands invasive species, such as Corallita, are recognized as one of the biggest threats to this delicate biodiversity, thus, their management is of critical importance. 

There is an insufficient amount of background literature about control methods and management of Corallita. Therefore, further research into control, ecology, plant phenology and factors regarding growth are needed in order to find an effective solution. One of the factors that there is still no knowledge about is the effect of shade on Corallita. It has long been known that light is the most important factor influencing plant growth, morphology, flowering time and plant productivity among others. Hence, it is necessary to comprehensively understand changes that occur when switching between shade and sun exposure in this invasive species. 

For this purpose, several field experiments were conducted in the island of Saba, one of the Dutch Caribbean islands affected by the presence of this plant, to evaluate the responses of Corallita’s growth and germination under different treatments of light availability. Corallita seeds and seedlings were exposed to 4 shading treatments (noncovered, partial shade, heavy shade and total covered) during approximately one month to quantify morphological parameters, such as plant height and weight, leaf number and area as well as seed survivorship rate. Nevertheless, results showed no significant differences between groups, suggesting that shade does not play a substantial role in the growth and germination of Corallita. 

Additionally, since most of the land in Saba is privately owned, it is as well important to get an insight of what the landowners are willing to do to get rid of the plant. Thus, semi-structured interviews, together with a focus group meeting, were performed aiming to identify which control method is more appropriate for landowners, in terms of their resources and necessities. The results showed that the economic factor is the most suppressing when controlling Corallita and that a manual method is currently seen as the most appropriate for them. 

Key words: Antigonon leptopus; Corallita; Germination; Growth; Light intensity; Shading