Abstract
Analyses of living and fossil taxa are crucial for understanding biodiversity through time. The total evidence method allows living and fossil taxa to be combined in phylogenies, using molecular data for living taxa and morphological data for living and fossil taxa. With this method, substantial overlap of coded anatomical characters among living and fossil taxa is vital for accurately inferring topology. However, although molecular data for living species are widely available, scientists generating morphological data mainly focus on fossils. Therefore, there are fewer coded anatomical characters in living taxa, even in well-studied groups such as mammals. We investigated the number of coded anatomical characters available in phylogenetic matrices for living mammals and how these were phylogenetically distributed across orders. Eleven of 28 mammalian orders have less than 25% species with available characters; this has implications for the accurate placement of fossils, although the issue is less pronounced at higher taxonomic levels. In most orders, species with available characters are randomly distributed across the phylogeny, which may reduce the impact of the problem. We suggest that increased morphological data collection efforts for living taxa are needed to produce accurate total evidence phylogenies.
Highlights
There is an increasing consensus among biologists that studying both living and fossil taxa is essential for fully understanding macroevolutionary patterns and processes [1,2]
The total evidence method [3], combines molecular data from living taxa and morphological data from both living and fossil taxa in a supermatrix that can be used with the tip-dating method [1,3,4,5,6], producing a chronogram with living and fossil taxa at the tips
A downside of this method is that it requires molecular data for living taxa and discrete morphological/anatomical data shared among both living and fossil taxa
Summary
There is an increasing consensus among biologists that studying both living and fossil taxa is essential for fully understanding macroevolutionary patterns and processes [1,2]. A downside of this method is that it requires molecular data for living taxa and discrete morphological/anatomical data shared among both living and fossil taxa (i.e. hard tissue characters such as skeletal features). The above-mentioned issues highlight that it is crucial to have sufficient coded anatomical characters available for living taxa in a clade before using the total evidence approach. Most people assume that these data have already been collected, but empirical analyses suggest otherwise (e.g. in [3,6,7]) To investigate this further, we assess the number of available coded anatomical characters for living mammals to determine whether enough data exist to build reliable total evidence phylogenies.
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