Toward understanding insect species introduction and establishment: a community-level barcoding approach using island beetles

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.