Hybridization between native and invasive alien plants: an overlooked threat to the biodiversity of Sri Lanka

Abstract

Conservation of native biological diversity is one of the major challenges of this century. Invasive alien species (IAS) are a part of this challenge because a small but a significant fraction of IAS contribute to the demise of native species. The present paper reviews current literature on the phenomenon of hybridization in plants supporting the evolution of invasiveness, which is identified as a major threat to the extinction of native species. Further, the phenomenon of hybridization is been reviewed on a Sri Lankan context by citing evidence from a preliminary study between the native Nymphaea nouchali and an introduced violet flowered water-lily that has got established in water-bodies of Sri Lanka. This violet flowered water-lily has been incorrectly identified as the native Nymphaea nouchali, the National flower of Sri Lanka ('Nil Manel'). Revealing the flawed identity of the violet flowered Nymphaea, its hybrid origin and the hybridization with the native N. nouchali, provides an excellent opportunity for initiating studies on a novel area in hybridization between natives and invasive alien species of plants in Sri Lanka.

The identity of the violet flowered water lily (Nymphaeaceae) and its hybrid origin in the wetland ecosystems of Sri Lanka

“…The other speculated parent was either N. capensis, N. cyanea or N. caerulea (Yakandawala & Yakandawala, 2011). The molecular evidence supports this identification where N. caerulea has high similarity scores (100 %, 99 % and 98 %) with the matK gene region for the three populations.…”

“…According to Subashini et al (2014), the violet water lily has a high demand as a cut flower in Sri Lanka and is the second aquatic cut flower species in demand of Buddhist religious places after white lotus. Initially the plant would have been restricted to controlled landscapes, but now it has escaped from the controlled environments and is naturalised and occurrs in all parts of the island except at higher elevations (Yakandawala & Yakandawala, 2011). Further, due to its ornamental value, ornamental plant growers would have been involved in importing and distributing this exotic plant in the past.…”

“…Therefore, it is probable that many successive introductions occurred where they got naturalised. Compared to the native N. nouchali, the exotic violet Nymphaea has a rapid mode of vegetative reproduction, where it is capable of producing proliferous leaves (Yakandawala & Yakandawala, 2011). The mature leaves of this violet Nymphaea are capable of developing a young plantlet at the leaf base where the petiole meets the lamina.…”

“…Among these, a large violet flowered water lily, 'Dam-manel' (S) has got extensively established in natural water bodies. This plant has been erroneously identified as N. nouchali, the native water lily, in literature both locally and internationally (Yakandawala & Yakandawala, 2011 and reference therein). There are no records of the era when this violet water lily was introduced to the country, but according to the prevailing evidence, its initial introduction would have been well over 50 years.…”

Identifying safe cultivars of invasive plants: six questions for risk assessment, management, and communication

“…For example, infra-specific entities can vary in the bioclimatic niches they occupy in their invasive ranges (Thompson et al 2011;Gotelli and Stanton-Geddes 2015), their host-specificity (Goolsby et al 2006), and the impacts they cause . Likewise, invasions by inter-specific taxa are also very important: hybridisation is one of the major impacts caused by biological invasions (Huxel 1999;Yakandawala and Yakandawala 2011). Therefore, it is vital that policy and regulation can adequately address invasion risk at levels other than the species.…”