Plastome phylogenomics and historical biogeography of aquatic plant genus Hydrocharis (Hydrocharitaceae)

Climate Change Potentially Leads to Habitat Expansion and Increases the Invasion Risk of Hydrocharis (Hydrocharitaceae)

Climate change is a crucial factor impacting the geographical distribution of plants and potentially increases the risk of invasion for certain species, especially for aquatic plants dispersed by water flow. Here, we combined six algorithms provided by the biomod2 platform to predict the changes in global climate-suitable areas for five species of Hydrocharis (Hydrocharitaceae) (H. chevalieri, H. dubia, H. laevigata, H. morsus-ranae, and H. spongia) under two current and future carbon emission scenarios. Our results show that H. dubia, H. morsus-ranae, and H. laevigata had a wide range of suitable areas and a high risk of invasion, while H. chevalieri and H. spongia had relatively narrow suitable areas. In the future climate scenario, the species of Hydrocharis may gain a wider habitat area, with Northern Hemisphere species showing a trend of migration to higher latitudes and the change in tropical species being more complex. The high-carbon-emission scenario led to greater changes in the habitat area of Hydrocharis. Therefore, we recommend strengthening the monitoring and reporting of high-risk species and taking effective measures to control the invasion of Hydrocharis species.

The dynamic history of plastome structure across aquatic subclass Alismatidae

BACKGROUND

The rapidly increasing availability of complete plastomes has revealed more structural complexity in this genome under different taxonomic levels than expected, and this complexity provides important evidence for understanding the evolutionary history of angiosperms. To explore the dynamic history of plastome structure across the subclass Alismatidae, we sampled and compared 38 complete plastomes, including 17 newly assembled, representing all 12 recognized families of Alismatidae.

RESULT

We found that plastomes size, structure, repeat elements, and gene content were highly variable across the studied species. Phylogenomic relationships among families were reconstructed and six main patterns of variation in plastome structure were revealed. Among these, the inversion from rbcL to trnV-UAC (Type I) characterized a monophyletic lineage of six families, but independently occurred also in Caldesia grandis. Three independent ndh gene loss events were uncovered across the Alismatidae. In addition, we detected a positive correlation between the number of repeat elements and the size of plastomes and IR in Alismatidae.

CONCLUSION

In our study, ndh complex loss and repeat elements likely contributed to the size of plastomes in Alismatidae. Also, the ndh loss was more likely related to IR boundary changes than the adaptation of aquatic habits. Based on existing divergence time estimation, the Type I inversion may have occurred during the Cretaceous-Paleogene in response to the extreme paleoclimate changes. Overall, our findings will not only allow exploring the evolutionary history of Alismatidae plastome, but also provide an opportunity to test if similar environmental adaptations result in convergent restructuring in plastomes.

Hydrocharis laevigata in Europe

Hydrocharis laevigata (Humb. & Bonpl. ex Willd.) Byng & Christenh. [= Limnobium laevigatum (Humb. & Bonpl. ex Willd.) Heine], Hydrocharitaceae, is a floating-leaf aquatic plant that is native to inland South America. It is an invasive species in several parts of the world. Reports of its presence in Europe have been recently published: naturalised populations occur in three locations on the Iberian Peninsula. The literature also contains records of the species in Hungary and Poland. In addition, it has been observed in Sweden, Belgium, and the Netherlands. H. laevigata is highly adaptable and can profoundly transform habitat conditions in its invasive range, causing major issues for ecosystem conservation and human activities. Until recently, H. laevigata was not to be found in natural environments in Europe. Factors explaining its spread include its use as an ornamental plant, the eutrophication of inland waters, and the effects of global warming. With a focus on Europe, this short communication provides information on the species' distribution, taxonomy, biology, habitat, and negative impacts.