Temperate lianas: Do traits predict their success in the northern temperate landscape?
Liana (woody vine) species are an understudied, but important ecological plant group. They can form dramatic infestations - completely blanketing the vegetation below them in an effort to reach the canopy, and can effectively escape competition. In contrast to warmer, tropical regions near the equator, the temperate zone has a far lower diversity of lianas, and subsequently much fewer studies that address their biology. Compared to North America, East Asia has a far greater number of liana species. The diversity of lianas in North America has been increased by the introduction of species from Asia for horticultural purposes. Some of these species have escaped from horticulture into natural areas and have proved to be aggressive invasive species, while others have not.
To further compare temperate North American and Asian lianas, biological and ecological traits were measured on stems and leaves of more than 40 closely related liana species. Leaf traits measured included leaf thickness, leaf toughness, specific leaf area, leaf dry matter content, leaf %N, leaf %C, 13C, 15N, and stem and wood specific gravity. These biological traits can provide insights into the ecology of these species. Using phylogenetically corrected methods, data were analyzed focusing on how traits of lianas vary based on both the origin of the liana (Asia vs. North America) and liana climbing mode (roots, stems, tendrils).
A total of 81 individual liana species were sampled. Overall, species from Asia and North America did not differ strongly in biological traits when only the main effects were examined. However, when climbing mode of the liana was taken into account, stem twining lianas from Asia had greater specific leaf area than North American stem twiners. High specific leaf area is an indication of greater growth rates. This greater specific leaf area could indicate an advantage for Asian stem twining lianas in North American habitats. Many invasive lianas, such as oriental bittersweet (Celastrus orbiculatus), Japanese honeysuckle (Lonicera japonica) and Asian wisterias (Wisteriaspp.) climb by means of stems.
By approaching the study of temperate lianas from a trait-based perspective, and focusing on a wide diversity of species and evolutionary lineages, we can gain a better understanding of the anatomical, morphological, physiological, and ecological traits that define the success of temperate lianas on the North American landscape.