Imagine that you want to catalogue all of the biodiversity (all of the living organisms) from a particular location; how many trained experts would that require? How many person hours would it take to collect and identify all of the rare, well-disguised, and microscopic organisms? How many of these organisms would have to be removed from the environment and taken back to a lab for taxonomic analysis.
Although there is no substitute for human expertise, we have begun using the traces of DNA that organisms leave behind (e.g. excretions, skin and hair cells) in the environment to catalogue biodiversity. These traces of DNA, referred to as environmental DNA, can persist in the environment for minutes or can persist for centuries depending on where they end up. This field of environmental DNA (eDNA) is rapidly becoming an effective tool to complement surveys of biodiversity, both past and present.
The source of occurrence data: fossil collections (photo by Konstantin Frisch).
To find out about changes in ancient ecosystems we need to analyse fossil databases that register the taxonomy and stratigraphic (temporal) positions of fossils. These data can be used to detect changes of taxonomic diversity and to draft time series of originations and extinctions.
The story would be so simple if it wasn’t the effects of heterogeneous and incomplete sampling: the white spots in our understanding of where and when species lived exactly. This phenomenon decreases the fidelity of face-value patterns extracted from the fossil record, making them less reliable. It must be considered if we want to get a glimpse into the biology or the distribution of life in space and time. Naturally, several metrics have been proposed to overcome this problem, each claiming to accurately depict the patterns of ancient life. Continue reading →