Fossil calibrated molecular phylogenies of Southern cave weta

Aim: The biota of continents and islands are commonly considered to have a
source-sink relationship, but small islands can harbour distinctive taxa.
The distribution of four monotypic genera within the southern subfamily
Macropathinae on young oceanic islands indicates a role for long-distance
dispersal and extinction. We used molecular dating to estimate the timing
of the southern radiation and infer potential processes involved.
Location: Subantarctic islands, South Africa, South America, Australia,
Aotearoa/New Zealand. Taxon: Southern hemisphere camel crickets subfamily
Macropathinae within the Orthopteran family Rhaphidophoridae (Cave
crickets/camel crickets/cave weta/tokoriro). Methods: Phylogenetic
relationships were inferred from whole mtDNA genomes and nuclear sequences
(45S cassette; four histones). We used a fossil and one palaeogeographic
event to calibrate a molecular clock analysis. Results: We confirm that
neither the Australian nor Aotearoa/New Zealand Rhaphidophoridae fauna are
monophyletic. The Macropathinae radiation may have begun in the late
Jurassic but trans-oceanic dispersal is required to explain the
distribution of some lineages within the subfamily Macropathinae. Dating
the most recent common ancestor of seven island endemic species with their
nearest mainland relative suggests that each existed long before land
surface on their island home was available. Main conclusions: If our
molecular clock analysis is a good time estimate, then our data from the
island endemic species suggest a failure to sample mainland species (New
Zealand, Australia, or elsewhere) due to either extinction or lack of
investment into taxonomy and species discovery.