February 2006

Secret of the 'Potted Palm' Revealed

New Case Study Contributes to Thinking on Origin of Species

A paper recently published in the prestigious journal Nature led by two senior scientists at the Royal Botanic Gardens, Kew, presents a unique case study of plant evolution in a tropical palm most familiar to us as one of our most popular houseplants. The Kentia palm (Howea forsteriana) was first made fashionable by the Victorians, but can now be found in homes, offices and restaurants throughout the world. Annual horticultural trade of this species is now valued in millions of pounds. In their native Lord Howe Island, however, the Kentia palm and its close relative the Curly palm (Howea belmoreana) have provided a tantalizing opportunity to refine theories on the origin of species, and new impetus for exploring plant and animal evolution on oceanic islands.

Howea belmoreana

Kew scientist on Lord Howe Island

Howea forsteriana

 

The origin of species diversity has challenged biologists for over two centuries. Allopatric speciation (species divergence resulting from geographical isolation) is well documented, however, sympatric speciation (divergence without geographical isolation) is highly controversial. Mathematical models have demonstrated that sympatric speciation is possible, but very few examples have been documented in the natural world. Until now no scientific study has convincingly satisfied all the requirements for a case of sympatric speciation in plants. However, the Kew study provides clear support for sympatric speciation in the two Howea palm species.

"This small window into plant evolution is a very exciting outcome from several years of extensive fieldwork," said Dr Bill Baker, co-author of the paper. Clues to the origins of the two species were found in their different flowering times observed in the wild as well as in their DNA. Their home on Lord Howe Island, an Australian territory in the South Pacific, was formed by volcanic activity over 6 million years ago. Its remoteness, small size and known age made it a perfect location for this research.

The work was funded by a grant to Kew from the Leverhulme Trust and involved the expertise of six Kew staff as well as collaborators from Australia, Denmark, France and Switzerland. The international partnership was led by Kew scientists, Bill Baker and Vincent Savolainen, who worked both on the island with living plants in-situ, and in the research facilities at the Royal Botanic Gardens. On Lord Howe Island they carefully monitored the flowering seasons and other aspects, while in the laboratories at Kew they produced one of the most comprehensive DNA-based family trees of palms. Their study shows that the two species of palm diverged from one another well after the island was formed.

About the team

WILLIAM J. BAKER, Systematist working on evolution, systematics and biogeography of palms. Research focusing on evolution and diversity in the palm family. Addressing phylogenetic relationships of palms at all taxonomic levels using a range of data sources. Building a new classification of palms for a forthcoming benchmark family monograph, Genera Palmarum Edition 2. Interpreting evolutionary process within a phylogenetic context, for example evolution of floral morphology and reproductive biology. Investigating the origins of diversity at the species level through interdisciplinary studies, for example, testing hypotheses of sympatric speciation on oceanic islands. Exploring the nature and origins of global patterns of palm diversity. Floristic interests in the Old World, especially SE Asia. Working towards a monograph of palms in New Guinea, a collaborative project integrating taxonomic research and capacity building. Developing new approaches to the delivery of taxonomic data via the web.

VINCENT SAVOLAINEN, Molecular Systematist, working on phylogenetics and evolutionary biology. Large-scale phylogeny reconstructions based on molecular data, and classification of the angiosperms, especially at family level and above, in collaboration with the Angiosperm Phylogeny Group. Methodological issues for building large phylogenies, performance of various characters and genes, super-tree reconstruction in grasses. Evolutionary processes based on phylogenetic patterns, correlates of species diversity, rates of molecular and morphological evolution, dating nodes, tree shape. Species-level phylogenies and inference of causes of speciation, such as pollinator shifts, geographical isolation, habitat preferences (e.g. currently neotropical Sinningia, South African Moraea, Australian Conostylis). Other research interests include evolutionary ecology (e.g. mimicry) and evolutionary developmental biology.

Sponsor

THE LEVERHULME TRUST are one of the largest all subjects providers of research funding in the UK, distributing funds of some £30 million every year. For further information about all the schemes the Leverhulme Trust fund please visit their website at www.leverhulme.ac.uk.