Mapping rainforest biodiversity

Australian rainforests have been fragmented due to past climatic changes and more recently landscape change as a result of clearing for agriculture and urban spread. The subtropical rainforests of South Eastern Queensland are significantly more fragmented than the tropical World Heritage listed northern rainforests and are subject to much greater human population pressures. The Australian rainforest flora is relatively taxonomically rich at the family level, but less so at the species level. Current methods to assess biodiversity based on species numbers fail to adequately capture this richness at higher taxonomic levels.

Traditional methods of biodiversity inventory are time consuming and are dependent on the availability of taxonomic expertise, which is a resource in rapid decline. Furthermore, identification of plants in tropical rainforests in most cases remains a challenge even for experts. DNA Barcoding represents a possible alternative means of estimating species richness without high level expertise in field identification skills in much less time.

A new study just published in PLoS ONE now shows how DNA Barcoding can be used to map plant biodiversity in a rainforest thereby helping to set conservation goals for the studied region. 

We developed a DNA barcode library for the SE Queensland rainforest flora to support a methodology for biodiversity assessment that incorporates both taxonomic diversity and phylogenetic relationships. We placed our SE Queensland phylogeny based on a three marker DNA barcode within a larger international rainforest barcode library and used this to calculate phylogenetic diversity (PD). 

Phylogenetic diversity is a measure of biodiversity that estimates phylogenetic difference between species. It is defined and calculated as the minimum total length of all the branches required to span a given set of taxa on a phylogenetic tree. 

The concept of phylogenetic diversity has been rapidly adopted in conservation planning, with programs as it allows to not only by-pass species identification especially when dealing with cryptic diversity, but also provides predictions of general biodiversity patterns. Some authors claim that by measuring phylogenetic relationships between taxa which in turn reflect evolutionary history we would end up with a more relevant estimation of biodiversity.

Conservation of biodiversity is more politically successful when it is seen as providing benefits to humans. Several authors have suggested that conserving PD may be an efficient way to capture a diversity of attributes which may prove useful. Dan Janzen argued that DNA barcoding should be adopted into the inventory to assess and document tropical rainforest biodiversity. This study demonstrates an application for biodiversity assessment and conservation planning that has benefited from this approach. Costion et al. showed how barcodes can determine species numbers accurately and so can be used to supplement rainforest inventory data and methods. The additional data gained on phylogenetic relatedness adds value to this approach especially where taxonomy is not well defined or field identification tools limited. This study identified the areas of highest priority for biodiversity conservation and utilised phylogenetic diversity as well as species richness to ensure greater capture of biodiversity incorporating higher order phylogenetic sampling of biodiversity.