Shaping up? A direct comparison between 2D and low-cost 3D shape analysis using African cichlid mandibles

Shape is a complex trait which can be investigated through a variety of methods that have been developed over the past century. Currently, ecologists and evolutionary biologists employ the use of geometric morphometrics on 2D images as their standard approach. Recently, there has been increased interest in the use of 3D methods. However, while low-cost 3D methods of data collection are becoming available their potential benefits are often more implied rather than quantified. Using the mandibles from two species of African cichlids (Maylandia zebra and Tropheops Red Cheek), this study aimed to evaluate the use of a low-cost 3D method of shape capture versus a range of 2D data sets (termed standard', even', and extended'). Our findings indicated that while both 2D and 3D methods could discriminate differences in species and sexes there was only a slight improvement using 3D when landmark datasets were held even. Further, the standard approaches to data collection that would be taken by most researchers clearly outperformed our 3D approach. Therefore, as 3D methods become more accessible researchers should consider a cost/benefit ratio in terms of the time required to obtain 3D data versus shape information gained.