CONCLUSIONS AND FUTURE PERSPECTIVES
The combination of genome-wide data with the use of coalescent models of
demographic history has enabled us to reject both extreme morphological
polymorphism and hybridisation to explain mitochondrial discordance and
lack of nuclear sorting in nominal species of Hogna spiders in
the Madeiran Archipelago. Instead, our results identified a third
independent evolutionary lineage, for which the name Hogna
biscoitoi is available, on the small and highly disturbed island of
Porto Santo. With this species, the number of endemic Hogna species in Madeira rises to eight.
Our study constitutes a further example of the perils of inferring
evolutionary processes based on the evidence provided by the results of
population structure analyses. With the introduction of genomics and
genome-wide markers, many studies have claimed the existence of hybrid
populations or introgressive hybridisation, without further evaluating
alternative scenarios compatible with the recovered patterns. We
encourage future studies to consider alternative evolutionary scenarios
to distinguish between ILS and gene flow and resolve challenging
taxonomic situations. In this study, we implemented a straightforward
protocol to fully disentangle between genetic signals in recently
diverged species, which will contribute to improving the correct
assessment of biodiversity in similar situations across biogeographic
regions. Although our data have greatly helped to elucidate one of the
major challenges in the current taxonomy of an island lineage of
spiders, some of which are of conservation concern, we encourage further
research to increase both the number of markers and, mainly, the
individuals and population sample size to test more specific
evolutionary events, such as bottlenecks associated with the
colonisation of new islands. Equally important, reconciling the genetic
evidence with a quantitative assessment of morphological data will allow
for the future identification of the drivers of speciation in this
exceptional island model.