The Importance of Body Size Standardization in Functional Diversity Studies of Dung Beetles (Coleoptera: Scarabaeidae: Scarabaeinae)

Functional diversity approaches, which are based on an organism's trait pattern, are of increasing interest in ecological studies. However, there are no rules setting the number or kinds of traits that should be assessed; hence, researchers are left to make their own decisions in this regard. Moreover, in some cases, the same trait could be assessed using different procedures, making comparisons between studies potentially difficult. Such is the case of dung beetle body size. We found that it was measured by using eight different methods in the literature. Using three scarabaeine dung beetle species (Canthon quinquemaculatus Castelnau, Deltochilum komareki Balthasar, and Eurysternus parallelus Castelnau), eight methods of measuring dung beetle body size (wet weight, dry weight, wet weight x clypeal-pygidial length, clypeal-pygidial length, pronotal-pygidial length, clypeal-elytral length, pronotal-elytral length, and elytral width x pronotal-elytral length) were compared to determine if they are equivalent. Using a Spearman correlation coefficient, not all the measurement methods were found to be equivalent. Wet and dry weight were the least correlated with all other methods. Hence, to standardize measurement methods in future studies, dry body weight is suggested for use, which also has the advantage of being an easy method to use. Standardization will allow more reliable and accurate comparisons between studies.