From Plant Press Vol. 17 no. 2, April 2014.
By Ashley N. Egan
Plants can eat things – large things! Well – figuratively anyway. One of the hungriest plants in the United States is kudzu (Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & Almeida), a large leguminous vine that can grow up to 60 feet in a growing season, and is often seen engulfing whole structures and damaging forest margins. I first became interested in kudzu while working as a postdoctoral fellow at Cornell University studying the phylogenetics and systematics of Phaseoloid legumes, a group of nearly 2,000 species mostly comprised of vines. During a phylogenetic investigation of subtribe Glycininae, we confirmed massive polyphyly within Pueraria. It was then that I determined to study the genus.
Kudzu was introduced into the United States in the late 1800s and touted by the U.S. government as an excellent forage crop and soil erosion solution. However, after escaping cultivation, efforts soon turned from advocacy to eradication, but with little success. Even today, kudzu continues to make headway across the American landscape, now occupying more than 15,000 square miles, costing the U.S. government hundreds of millions of dollars annually in control measures.
This invasive species, along with 20 or so congeners, is native to Southeast Asia where it grows from sea level to around 2000 m in elevation in temperate and (sub)tropical climes. To investigate the introduction history and genetic diversity of kudzu in the U.S. as compared to native ranges, and to decipher the extent of polyphyly in the genus, I set out on my second Asian expedition to collect Pueraria.
On 1 September 2013, just two weeks after starting as an Assistant Curator at the Smithsonian Institution, I and my Ph.D. student, Matthew Hansen, flew to Beijing, China – the first stop on a three month expedition that would cover three countries. In Beijing, we met up with Liu Luxian, a first-year Ph.D. student from Zhejiang University studying in Chengxian Fu’s lab. After two days of preparations, we boarded a train towards Anshan, Liaoning Province, one of the most industrial cities of China, at the northern edge of kudzu’s native range. There, we collected our first kudzu population of the season in the Qianshan Mountains. After returning to Beijing by train and preparing our specimens for travel, we flew to Xi’an, Shaanxi province for the second leg of the expedition.