The widespread hemiparasitic Lauraceae genus Cassytha currently contains 19 described species, one variety and four forms. This genus is controversial and has not been resolved satisfactorily. Cassytha filiformis is cosmopolitan in tropical and subtropical regions. It is currently the only species reported from China.
Accurate species delimitation has been a great challenge for biodiversity conservation practice, and many species may have already gone extinct before they were recognized and described, especially for morpho-hyperspecialized parasitic, hemiparasitic plants, where it is very difficult to grasp the species exactly.
In a study published in Journal of Systematics and Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators examined Chinese Cassytha samples currently placed into C. filiformis as well as several related members of the racemose group to investigate the phylogenetic and evolutionary history of the genus in the region.
Using integrated means such as phylogenetic analysis, morphological trait statistical analysis, and species distribution simulation, the researchers explored whether there are cryptic species of Cassytha filiformis within China and neighboring regions.
The phylogenetic analysis results showed that C. filiformis formed two well-supported monophyletic lineages, and the morphological analyses revealed that the two lineages differed significantly in both the thickness of the inflorescence stalk and the fruit type ratio. The species distribution simulations showed that different environmental factors affected their distributions. Moreover, the divergence time of the two lineages was inferred to be around the Early Miocene, and it was suggested that the divergence of hemiparasitic love vine  cryptic species may have been related to new ecological opportunities and host diversification brought by the early Miocene East Asian monsoon.
"Our study revealed the cryptic diversity of the enigmatic hemiparasitic love vine Cassytha filiformis in China and neighbouring areas. It provides new evidence for the wide spread existence of cryptic species in parasitic plants,” said LI Jie of XTBG.

Contact
LI Jie  Ph.D Principal Investigator
Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China
E-mail:  jieli@xtbg.ac.cn
First published: 31 March 2024