Austinixa aidae Righi, 1967 and A. hardyi Heard and Manning, 1997 (Decapoda: Brachyura: Pinnnotheridae) synonymized, with comments on molecular and morphometric methods in crustacean taxonomy

While conducting a systematic study of Austinixa Heard and Manning, 1997, we encountered difficulties in distinguishing A. hardyi Heard and Manning, 1997 from A. aidae Righi, 1967, based on characters discussed in the current literature. We re-examined morphological characters previously reported as diagnostic, and assessed their variation within and between these putative species. We expanded the analysis to include three independent types of data: discrete morphological characters, morphometric characters, and mitochondrial DNA sequence data. Partial sequences of the mitochondrial 16s rDNA and cytochrome oxidase I (COI) genes were almost identical between A. aidae and A. hardyi, raising questions about the validity of A. hardyi as a distinct species. Analysis of morphometric characters using multivariate (principal components analysis) and univariate allometric adjustment methods, support the mitochondrial DNA data in suggesting A. aidae and A. hardyi are a single species. Finally, we provide a brief review of the morphometric and molecular methods used in this study and comment on the usefulness of these methods in crustacean taxonomy.