Testing species boundaries in the Antrodiaetus unicolor complex (Araneae: Mygalomorphae: Antrodiaetidae): “Paraphyly” and cryptic diversity

The inability to correctly identify species has far reaching implications in nearly all areas of biology, yet few studies investigate methods for delineating species boundaries. Moreover, once these boundaries have been hypothesized, little thought has been given to how these constructs can be further evaluated. We employ a molecular phylogenetic approach using nuclear 28S rRNA and mitochondrial cytochrome c oxidase subunit I genes to test the general efficacy of species boundaries in the Antrodiaetus unicolor spider species complex. Our analyses provide evidence that An. unicolor is “paraphyletic” with respect to An. microunicolor, indicating that morphological criteria used to delineate species boundaries undersplits actual species-level diversity in this group of spiders. These analyses also demonstrate that individuals from geographically proximate populations sometimes exhibit considerable molecular divergence, strongly suggesting that An. unicolor is a cryptic species complex. Finally, this molecular approach has provided the phylogenetic framework that is necessary to begin interpreting the vast amount of morphological variation observed in these spiders based upon findings from previous studies. Our approach using multiple genes appears to be a rigorous method to critically examine species boundaries originally based on traditional morphological approaches to spider taxonomy.