Genome-wide screening discerns incomplete lineage sorting from
gene flow among wolf spiders from Madeira
Alba Enguídanos García1,2, Luís C.
Crespo3, Miquel Arnedo1,2, Vanina
Tonzo4
- Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals,
Universitat de Barcelona, Avinguda Diagonal 643, 08028 Barcelona,
Spain
- Institut de Recerca de la Biodiversitat (IRBio), Universitat de
Barcelona (UB), Barcelona, Spain.
- cE3c – Centre for Ecology, Evolution and Environmental
Changes/Azorean Biodiversity Group, CHANGE – Global Change and
Sustainability Institute, University of the Azores, Rua Capitão João
d´Ávila, Pico da Urze, 9700-042 Angra do Heroísmo, Azores, Portugal
- CEFE, Université Montpellier, CNRS, EPHE, IRD, Montpellier, 34293,
France.
corresponding author: albaengarcia@gmail.com
Running title: Genomic insights into Madeira wolf spiders
Genomic data offers valuable insights into
population history and species divergence, but interpreting complex
evolutionary processes remains challenging, particularly in cases of
recent divergence and ancestral polymorphism. This study addresses the
taxonomic and evolutionary complexities of two endemic Hogna spider species from Madeira, H. maderiana from Porto Santo andH. insularum from Madeira, Desertas, Bugio, and Porto Santo,
which exhibit mitochondrial gene tree discordance and ambiguous
morphological boundaries. Using ddRADseq genomic data, population
genomic analyses, and coalescent-based demographic analyses, we aim to
determine whether these two nominal species represent a case of early
divergence with unsorted molecular markers due to incomplete lineage
sorting (ILS), if they are hybridising within the contact zone on the
island of Porto Santo, or if they represent a single species exhibiting
extreme morphological polymorphism. Our genetic structure analyses
suggested three potential genetic clusters, one for each nominal species
and one compatible with hybridisation between the two species on Porto
Santo Island. However, demographic modelling and D-statistics rejected
gene flow, instead supporting the existence of a third independent
lineage in Porto Santo. The lack of genetic separation between these
lineages likely reflects short recent divergence and unsorted ancestral
polymorphisms. Our findings highlight the challenges of inferring
hybridisation solely based on population structure analyses, which may
lead to an overestimation of gene flow. This study highlights the
importance of integrating demographic modelling and genetic data to
resolve complex evolutionary histories and emphasizes the need for
careful interpretation of genomic data to avoid misattributing gene
flow.