As thousands of scientists and policymakers gather in Mexico this month for the COP13 summit on biodiversity (see www.cbd.int/cop2016), we should take a moment to celebrate the earliest 'tree of life' model of biodiversity.
Charles Darwin published the idea of a tree of life in On the Origin of Species in 1859. Seven years later, German zoologist Ernst Haeckel painstakingly drew up a much more comprehensive tree (pictured). This represented Earth's wealth of species in the context of evolution — a concept he dubbed phylogeny (General Morphology of Organisms; 1866).
The root of the tree symbolizes a common primordial ancestor from which all other forms emerged. Haeckel developed his tree over almost 1,000 pages, basing it on palaeontological, embryological and systemic data — a precursor to modern biology's phylogenetic trees.
He also coined the term ecology ('oecologie'), describing it as “the whole science of the relations of the organism to the environment including, in the broad sense, all the 'conditions of existence'”.
Haeckel's ideas were harbingers for discoveries such as that by ecologist Santiago Soliveres and colleagues, who demonstrated that ecosystem multifunctionality depends on high species richness (Nature 536, 456–459; 2016).