Dr Colin Hughes, from the Institute of Systematics and Evolutionary Botany, University of Zurich, gave a fascinating and highly detailed talk on the evolution of legumes - a hugely diverse and economically important family of plants. Colin’s talk illustrated how phylogenetics can help us answer how the legumes came to be such an evolutionary success story. However, being such a large family, studying the evolutionary history of this group is a challenge. The Legume Phylogeny Working Group (2017) revealed that the legume family contains several large unresolved clades, or polytomies, in which branches do not split dichotomously into separate lineages. This makes it impossible to state which lineage is ancestral relative to another. Colin detailed the work his lab has contributed to the challenge of resolving these polytomies, and “rooting”, or finding the origins of, several of the legume subfamilies.
The talk then focused on the Mimosoids, a clade of tropical legumes within the subfamily Caesalpinioideae. Biogeographic work on the group has revealed historical dispersal of these legumes into distinct biomes across the tropics. Colin highlighted that closely related lineages within the mimosoids have disjunct distributions between succulent habitats in the old and new world, suggesting a strong association between legumes and succulent biomes. As succulent biomes are characterised by low rainfall, the origins of these lineages during the Miocene is interesting as it coincides with a time of aridification events globally.
The sheer amount of information communicated Colin was extremely impressive, if not overwhelming. The work of his research group will surely continue to shed light on the systematics and evolutionary ecology of this extraordinary family of plants.
Abigail Motley, DPhil student under Professor Andrew Smith, is currently studying the evolutionary ecology of the Malagasy spiny thicket biome.