Hybridization with natives augments the threats of introduced species in Sonneratia mangroves

Hybridization between introduced and native species is highly likely as human introduction removes spatial barriers. The mangrove species Sonneratia apetala has been introduced to South China from Bangladesh and frequently planted as part of reforestation efforts over the previous three decades. Sonneratia apetala has been shown to suppress the growth of native mangrove species and has become invasive in several mangrove forests of South China. In this study, we report an additional competitive advantage of S. apetala via cross-species hybridization with the native species S. alba, using morphological and DNA polymorphism data. We further show that the native S. alba is the maternal parent in this hybridization, thus becoming even more vulnerable to the introduction on both the ecological and genetic fronts. Given that hybridization accompanies some of the most serious invasions on record, we recommend monitoring hybridization events before any wide-spread introduction.