Since Darwin put forward his opposing hypotheses to explain the successful establishment of species in areas outside their native ranges, the preadaptation and competition-relatedness hypotheses, known as Darwin’s naturalisation conundrum, numerous studies have sought to understand the relative importance of each. Here we take advantage of well-characterised beetle communities across laurel forests of the Canary Islands for a first evaluation of the relative support for Darwin’s two hypotheses within arthropods. We generated a mitogenome backbone tree comprising nearly half of the beetle genera recorded within the Canary Islands for the phylogenetic placement of native and introduced species sampled in laurel forests, using cytochrome c oxidase I (COI) sequences. For comparative purposes, we also assembled and phylogenetically placed a data set of COI sequences for introduced beetle species that were not sampled within laurel forests. Our results suggest a stronger effect of species preadaptation over resource competition, while also revealing an underappreciated shortfall in arthropod biodiversity data – knowledge of endemic species. We name this the Humboldtean shortfall, and suggest that similar studies using arthropods should incorporate DNA barcode sequencing to mitigate this problem.

Coleoptera sampling by active and passive methods

Extraction and amplification of DNA using Jerry-Spat (COI-3P) and folmer (COI-5P) primers to obtain COI sequences of each species sampled in the laurel forest. Completion of the species dataset with GenBank and/or BOLD Systems sequences of records of species introduced to the Canary Islands but not sampled by us in the laurel forest.

Generation of mitogenomes using the TruSeq Nano DNA kit and Illumina sequencing. Mitogenomes assembled with IDBA, celera, ray, and SPAdes methods.  Mitogenome species list completed with mitogenomes available in GenBank.

Generation of the Mitogenome backbone tree using Phylobayes

Phylogenetic placement of COI sequences into the mitogenome backbone tree using CIPRES Science Gateway.