Science

• Current Initiatives
  • Biodiversity of the Hengduan Mountain region, China
  • Botanical diversity and biogeography of peninsular Thailand
  • Center for Tropical Forest Science-Arnold Arboretum Asia Program
  • Hemlock Hill management and research
  • Molecular biology and evolution of phytochrome systems
  • Phylogeny and biogeography of woody plants
  • Plant hydraulics - Zwieniecki lab
  • Tree of Life
• Fellowships
  • Mercer Research Fellowships in plant biology
  • Putnam Fellowships in plant science
  • Curatorial Fellowship
  • Deland Award for Student research
• Staff
• Herbaria

Botanical Diversity and Biogeography of Peninsular Thailand

Introduction

Thailand is one of the most botanically diverse countries in the world with an estimated 12,000 vascular plant species. The southern peninsula of Thailand spans nearly eight degrees of latitude (about 5 degrees N to 13 degrees N) and includes the transition zone between the Indo-Burmese and Sundaland floristic regions, two of the six most diverse and threatened biodiversity hotspots in the world. It has been estimated that over 500 genera of plants have their northern or southern distributional limits within the transition between these floristic regions.

Several explanations for why these floras became and remain distinct have been proposed, including the role of great variations in length of dry season that occurs within the peninsula. However, analyses of species distributional patterns have not been possible due to a dearth of plant collections from the peninsula. Thailand’s average of only 50 herbarium specimens per100 km2 pales in comparison to countries such as the United Kingdom (1,720 specimens per100 km2) and is even low compared to other areas of Southeast Asia (e.g., Java and the Malay Peninsula each average nearly 200 specimens per 100 km2).

The principal objective of this new project is to create an inventory of the plants of peninsular Thailand through intensive field collection and collation of existing records. In addition to testing biogeographic hypotheses on this flora, the inventory will be used to create an interactive, computerized, web-accessible key to the families and to selected genera of the peninsula. It is expected that numerous new country and regional distributional records will be made, as well as the discovery of many taxa new to science. Plant inventory data derived from this project will also be used for the broader Flora of Thailand project and will form an important resource for critical conservation initiatives in the peninsula.

Peninsular Thailand

The southern peninsula of Thailand stretches over 1,000 km in length, from the Malaysian border in the south (5 degrees 40 minutes N) to Ratchaburi in the north (about 13 degrees N, near Bangkok). The climate is tropical, with daytime temperatures of 25 to 33 degrees C (80 to 90 degrees F) year-round. The east coast borders the South China Sea and Gulf of Siam. T he upper half of the peninsula is shared with southern Myanmar (Burma) to the west, while the southern half borders the Andaman sea. A nearly continuous ridge of mountains runs the length of the peninsula, which allows for a diversity of climate along a very narrow east-to-west gradient (that is, dryer to the west, wetter to the east). An extraordinary array of habitats exists in the peninsula due to large variations in climate, elevation, soils, and latitude. The most extensive karst limestone forests in Thailand are in the peninsula.

Why Peninsular Thailand?

• The peninsula stretches over 1,000 km (600 mi) in length and contains over 50 percent of the plants of Thailand (>6000 species) yet covers only 16 percent of the land area of the country.
• Despite the high level of biodiversity, the peninsula has one of the lowest collecting densities in Thailand.
• Peninsular Thailand is the meeting point of the Indo-Burmese and Sundaland floristic regions, two of the six most diverse and threatened biodiversity “hotspots'” in the world (Myers et al., 2000).
• Approximately 500 genera of flowering plants have their northernmost or southernmost distributional limit along the peninsula.
• The climate shifts from strongly seasonal (a greater than four-month dry season) at the northern end of the peninsula to essentially aseasonal (less than one-month dry season) at the Malaysian border. This is one of the more dramatic climactic transitions in tropical Asia and is the most probable explanation for the high level of species turnover.
• The extraordinary diversity of habitats in the peninsula is of great interest to researchers. Some of the habitats to be found in the peninsula include lowland, evergreen Dipterocarp forest, lower montane forest, dry deciduous forest, mangrove forest, peat swamp forest, beach forest, and karst limestone forest.

Project Objectives

• Significantly increase the number of plant collections from peninsular Thailand.
• Examine the distribution of species, genera, and families along the peninsula.
• Search for regions of particularly high species turnover.
• Contribute data and taxonomic treatments to the Flora of Thailand project.
• Distribute specimens and DNA material to numerous herbaria and botanists in order to improve collections and foster collaborative research.
• Create a database of collections from peninsular Thailand to be shared with interested researchers around the world.
• Strengthen collaborative ties between botanists in the USA and Thailand.
• Provide an important botanical resource for critical conservation initiatives in Thailand.
• Create an interactive, computerized, identification key to the plant families of peninsular Thailand. Make additional identification keys to genera and species in selected families (e.g., Zingiberaceae).

Methodology

• Conduct two to three joint Harvard-Thai collecting expeditions (one to two months each) in Thailand per year for the next three years. We estimate collecting 1,500-plus specimens per year.
• Collect all types of land plants, including angiosperms, gymnosperms, ferns, and bryophytes.
• Distribute duplicate collections to experts on various plant groups in order to obtain the most reliable identifications possible. Project researchers will identify groups lacking experts.
• Collect DNA material on silica gel of plant groups that researchers have expressed interest in receiving.
• Survey major herbarium collections (e.g., Harvard, Kew, Leiden, and those in Thailand) for collections from the peninsula. This survey will focus on families and genera with numerous representatives in the peninsula for which accurate identifications are available.
• Use data from relevant molecular phylogenetic studies of plant groups to see if distributional patterns have phylogenetic (i.e., evolutionary) structure. This pattern has already been found within the genus Globba (Zingiberaceae).
• Sample as much diversity as possible in selected sites on multiple occasions at different times of year.

Project details

• Project length: Three years, from November 2003 to November 2006.
• Funding: National Science Foundation Systematic Biology and Biodiversity Inventories grant DEB-0315985.
• Project area: Peninsular Thailand, from the Thai-Malay border in the south to the northern border of Phetchaburi province in the north.
• Primary investigators: Stuart Davies & David Middleton (Harvard University, Co-PI's), Kyle Williams (Harvard University, post-doctoral fellow), Kongkanda Chayamarit (Forest Herbarium Bangkok), Rachun Pooma (Forest Herbarium Bangkok), and Somran Suddee (Forest Herbarium Bangkok).
• Primary goal: To increase scientific knowledge of the biodiversity, distribution, and habitat preferences of the plants of peninsular Thailand through field collection and herbarium study.