Introduction

Over the two decades since the term biological diversity came into existence (Lovejoy 1980a, 1980b; Norse and McManus 1980; Wilson, 1980) (later biodiversity – Wilson 1988), the tree of life has been transformed dramatically. Originally two stout trunks representing plants and animals with microorganisms near their base, today the tree of life is a low spreading bush of which two tiny twigs represent plants and animals (see Fig. 2.1) The remainder of the current ‘tree’ is mostly microorganisms, many with strange metabolisms probably dating to the early history of life on earth.

Current knowledge of biological diversity consists of roughly 1.5 million described species. The estimates of the total number of species – described and undescribed – vary considerably. The current consensus (Heywood, 1995) is about 10 million species, although estimates have run as high as 30 million to 100 million As major unexplored parts of the biosphere are investigated – tropical forest canopy, soil biodiversity and marine ecosystems for example – the estimate may well change. For example, an investigation of fungal endophytes (fungi which live in healthy plant tissues) of just two understorey tree species in Panama suggests an astonishingly rich flora of a group which is essentially unknown (Arnold et al. 2000). An All Species Inventory – ‘ALL’ – is being initiated to speed the exploration of the unknown and greater part of biological diversity (Kelly 2000).