Behind the Cover: New Phytologist 219:2, July 2018

High up in the Cordillera Blanca of the Peruvian Andes, the grey of the barren rock is broken by the delicate purple flowers of Lupinus huaronensis. Hunkering in its unusual acaulescent (stem-less) growth form at an elevation of 4,550 metres, the plant is well adapted to the diurnal freeze-thaw conditions found in the high elevation Andean grassland (Paramo, Puna, Jalca) habitats, close to the upper limits for plant growth anywhere on the planet.

Image: Lupinus huaronensis, a large acaulescent rosette lupin growing at 4550 m in the Peruvian Andes. Courtesy of Colin Hughes.
Lupinus huaronensis, a large acaulescent rosette lupin growing at 4550 m in the Peruvian Andes. Courtesy of Colin Hughes.

Bruno Nevado and a team of researchers from the UK, Colombia and Switzerland are trying to understand the underlying genetic and adaptive reasons for very rapid recent plant speciation. Lupins are an excellent system for studying this phenomenon: the high elevation Andean evolutionary radiation of around 85 lupin species has arisen in just the last 2.5 million years, and shows one of the highest rates of species diversification for plants.

The rapid diversification of Andean lupins is still accelerating, which suggests that they are still in the early stages of an explosive radiation. The driver is thought to be linked to the emergence of isolated habitats at high elevations, following the uplift of the Andes, but the exact mechanisms and processes remain unclear.

Image: Lupinus weberbaueri. Courtesy of Colin Hughes.
Lupinus weberbaueri. Courtesy of Colin Hughes.

In their New Phytologist paper, Nevado and colleagues focus on the possible impacts of Pleistocene glaciations on plant speciation in the Andes. As Pleistocene glaciations forced the high elevation grassland biome down-slope, they imposed repeated cycles of range expansion, contraction, connectivity and fragmentation. The researchers are aiming to understand how glacial cycles could have acted as a kind of ‘species pump’, contributing to rapid diversification, by investigating how post-speciation geneflow was distributed across the genomes of recently diverged sister species of Andean lupins.

Image: Lupinus pulvinaris. Courtesy of Colin Hughes.
Lupinus pulvinaris. Courtesy of Colin Hughes.

The study required extensive fieldwork: the researchers worked across the Andes, from Venezuela to Argentina, to collect more than 700 accessions of around 85 lupin species, and assemble a large photographic library. Working at 5,000 metres above sea level demanded altitude acclimatisation and strong lungs, particularly since many of the species – such as L. huaronensis, pictured on the cover – are rare and grow only on steep, inaccessible rocky screes.

Image: Lupinus tauris. Courtesy of Colin Hughes.
Lupinus tauris. Courtesy of Colin Hughes.

Photography provides one way to document the enormous variety of growth forms and life history strategies in the lupins: ranging from annual herbs to dwarf prostrate perennials, large perennial shrubs and even small treelets. The acaulescent rosette growth form shown on the cover illustrates the idea that ecological adaptations play an important role in the diversification of high elevation lupins.

Image: Lupinus semperflorens. Courtesy of Colin Hughes.
Lupinus semperflorens. Courtesy of Colin Hughes.

Read the paper: Nevado, B. , Contreras‐Ortiz, N. , Hughes, C. and Filatov, D. A. (2018) Pleistocene glacial cycles drive isolation, gene flow and speciation in the high‐elevation Andes. New Phytologist 219:2, 779-793. doi:10.1111/nph.15243

Mike Whitfield (@mgwhitfield)
Development Coordinator
New Phytologist Trust