Dietary database visualisation
The Australian Antarctic Division is in the process of assembling a database of dietary data for the Southern Ocean. In order to assist in populating this database, we generated the above visualisation of the taxonomic coverage of the data. The circular tree structure represents the taxonomy of the Southern Ocean (from the Register of Antarctic Marine Species (RAMS), provided by SCAR-MarBIN.
The tree shows taxonomic levels down to order. Taxa that appear in our trophic database are shown as blue nodes.
The background "pie slices" indicate the coverage by taxonomic class — the larger the pie slice, the greater the proportion of that class that is represented in our trophic database. The green part of each slice indicates the proportion of taxa in that class for which we have predator information, the blue indicates the proportion for which we have prey information, and the pink the proportion of taxa for which we have both predator and prey information.
Discussion
The results show some interesting (albeit not unexpected) patterns. Much of our collection of predator data has been focused on higher trophic levels such as birds, fish, and seals. See the "pie slice" for cephalopoda (the long, thin one in the top-right quadrant). The length of this slice indicates that we have pretty good taxonomic coverage for cephalopods (in fact we have data for all five of the cephalopod classes). However, the slice is almost entirely blue, meaning that our data tell us much more about what eats cephalopods that about what they eat.
Some of these inbalances in the database represent biases in the data entry. Almost all of the data that has been captured in this database to date has been drawn from direct studies of diet composition (e.g. by examining gut content of predators). This naturally introduces a bias toward predators at higher trophic levels. It also introduces biases against prey that are not well represented in such studies — for example, gelatinous prey can be very difficult to identify in gut contents.
The data entered thus far has also been predominately from East Antarctica, where Australia has concentrated its research efforts. We are now looking to supplement the taxonomic coverage of the database with data from other regions of the Antarctic.
