Paper short abstract:

Genetic research suggests that a non-domesticated lineage of taro has hybridised with other Colocasia species in North Vietnam. There is no evidence yet of hybridisation with cultivated taro. This implies a relatively recent arrival of cultivated taro, or constraints on breeding by cultivated taro.

Paper long abstract:

During recent surveys in northern Vietnam, we found breeding populations of wild taro (Colocasia esculenta) in and around human settlements (commensal wild taro) and also in apparently natural habitats. From lower to higher altitudes, and across diverse ecological zones, we encountered at least five different Colocasia species, and diverse pollinating flies in the genus Colocasiomyia.

Previous genetic research suggests that C. esculenta has hybridised with other Colocasia species multiple times. It is likely that human introduction of cultivated taro, and human creation of open habitats suitable for wild and cultivated taro, has led to greater sympatry between taro and other Colocasia species, and among their associated insect pollinators. However, introgressed lineages of the taro chloroplast genome belong to a wild superclade that is not known to have been domesticated. There is no evidence yet of hybridisation between cultivated taro and the other wild Colocasia species.

Our findings imply a relatively recent spread of cultivated taro into the region, or biological constraints on cross-breeding, despite sympatry. The biological limits on cross-breeding between Colocasia species are not yet known. If hybridisation and introgression were natural processes that predated human introduction of taro, they may reflect long-term changes in climate and plant distributions, over millions of years.

If breeding by naturalised forms of cultivated taro is widespread, it may have helped generate diversity among cultivated taros in Vietnam. Cross-breeding among cultivars is inherently more likely to generate new cultivars than cross-breeding with natural wild populations of taro or with other Colocasia species.