ECR feature: Yongsheng Chen on the impact of invertebrate dispersal on plant distributions

Yongsheng Chen is a post-doctoral researcher at Peking University. He is an evolutionary biologist interested in unveiling the temporal and spatial processes shaping the diversity of East Asian plants. Here, Yongsheng shares his recent work on the role of invertebrate-mediated dispersal in plant species distributions.

Yongsheng Chen during a field trip in Laos.

Personal links. Research Gate

Institute. Peking University

Academic life stage. Postdoc

Major research themes. Botany, biogeography, ecology, phylogeny

Current study system. My major research focus is on the phylogeny and biogeography of East Asian seed plants. Eastern Asia has the most outstanding plant species diversity with many Cenozoic relict seed plants, including Tetracentron, Cercidiphyllum, Davidia, Trochodendron, Euptelea, Ginkgo, Cathaya and Metasequoia. For this reason, many botanists and biogeographers consider East Asia to be a key biodiversity hotspot for understanding the origin and evolution of Northern Hemisphere floras. To better understand how the East Asian flora was assembled over time, my ultimate goal is to reconstruct the temporal and spatial evolution of some representative plants of East Asia, using molecular phylogenetic data, fossil information and environmental evidence.

Stemona mairei in the Yangtze River valley with flowers (left) and fruits (right; Photos credit: Yi Yang).

Recent paper in JBI. Chen, Y. S., Zeng, C. X., Muellner-Riehl, A. N, Wang, Z. H., Sun, L., Schinner, J.,  Kongkiatpaiboon, S.,  Kadota, Y., Cai, X. H., & Chen, G. (2021). Invertebrate-mediated dispersal plays an important role in shaping the current distribution of a herbaceous monocot. Journal of Biogeography, 48(5), 1101–1111.

Motivation behind this paper. As the most common means for range expansion across space and time, dispersal is invoked as an important explanation for many plant taxa’s current distribution. Although previous studies have investigated the dispersal of plant taxa by vectors such as wind, ocean currents and vertebrate animals, little is known about the specific impact of invertebrate-mediated dispersal on the biogeography and current distribution of plants. Among the few examples, Stemonaceae (c. 37 species) is a typical invertebrate dispersed family that can attract both ants and hornets to transport diaspores. Interestingly, almost all the myrmecochorous (i.e., seeds dispersed by ants) lineages of Stemonaceae are narrow endemics and restricted to continental areas. In contrast, the vespicochorous (i.e., seeds dispersed by hornets) species occupy not only continental areas but are also isolated in oceanic islands. The distributional differences imply that the dispersal modes may impact the biogeographical processes in Stemonaceae. We tested this hypothesis under a phylogenetic context.

Key methodologies. To better understand the mechanisms responsible for the current distribution of Stemonaceae species and test whether dispersal mediated by invertebrate vectors played a significant role in shaping the present distribution of the species, we first constructed the phylogenetic relationship of this family using three plastid gene regions. With it, we were able to estimate divergence times and reconstruct the biogeographical history of Stemonaceae. Based on the distribution data, we then calculated the range size of each species and tested the relationship between dispersal modes and geographic distributions using phylogenetic logistic regression analyses.

Ant transporting the diaspore of Stemona (Photo credit: Gao Chen).

Unexpected challenges. One major challenge in this study was to obtain adequate sampling, given the difficulty of obtaining material across many countries. Because most species of Stemonaceae are narrow endemics, multiple field trips across China and SE Asian countries were needed to collect specimens and DNA material. For those species with a distributional range in difficult to access areas, we asked botanists around the world to provide us with specimens or dried materials. Fortunately, we finally sampled ca. 75% of the species diversity in Stemonaceae, covering the entire distribution range of the family.

Major results. Our current research suggests that invertebrate-mediated dispersal may have played an important role in shaping the current distribution of plants, probably due to limited dispersal promoting local adaption and narrow endemism. In Stemonaceae, species’ distributions are strongly correlated with its dispersal modes. Despite the long evolutionary history of Stemonaceae (from the Late Cretaceous to the present), most myrmecochorous species failed to disperse across oceanic barriers, with their ranges confined to continental areas due to the low dispersal ability. In contrast, vespicochorous species were able to cross oceanic barriers and occupy large and remote areas, including continents and oceanic islands.

Hornet transporting the diaspore of Stemona tuberosa (Photo credit: Gao Chen).

Next steps for this research. Due to limited sampling and molecular markers, the evolutionary history of some genera (e.g., Stemona, Stichoneuron) from this family is still not fully resolved. We are working to reconstruct their relationships in the future by extending the sampling scheme and applying Next-Generation-Sequencing techniques. Also, in order to better understand the origin and evolution of East Asian flora, I am interested in studying and reconstructing the evolutionary history of other East Asian plant families.  

If you could study any organism on Earth, what would it be? In my opinion, the most interesting organisms are plants from East Asia. As a key biodiversity hotspot, East Asia has the highest species diversity (more than 3,000 genera) in the Northern Hemisphere, presenting high plant endemism, including paleoendemic and neoendemic genera. It harbors nearly 75% of all gymnosperm families and a large number of angiosperms (~60% of APG recognized families). It is a key region for us to understand the origin and evolution of the Northern Hemisphere flora.

Published by jbiogeography

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