Hidden island endemic species and their implications for cryptic speciation within soil arthropods

Specialisation to the soil environment is expected to constrain the spatial scale of diversification within animal lineages. In this context, flightless arthropod lineages, adapted to soil environments, but with broad geographical ranges, rep-resent something of an anomaly. Here we investigate the diversification process within one such ‘anomalous’ soil specialist, an eyeless and flightless beetle species strongly adapted to the endogean environment but distributed across several oce-anic islands.We would like to thank Pedro Oromí, Rafael García, Irene Santos, Eduardo Jiménez, David Hernández and Antonia Salces-Castellano for their help in the fieldwork and/or sample processing. Rafael García also provides us specimens of Geomitopsis from La Palma. We thank Jesús Arribas for drawing the habitus of Geomitopsis. This work was supported by projects CGL2015-74178-JIN (funded by MCIN/AEI/10.13039/501100011033, Spain and EDRF, EU) awarded to CA, CGL2017-85718-P (funded by MCIN/AEI/10.13039/501100011033, Spain and EDRF, EU) awarded to BCE, PID2020-116788GB-I00 (funded by MCIN/AEI/10.13039/501100011033, Spain) awarded to BCE, and with funds from FundaciónCaja Canarias and Fundacion Bancaria ‘La Caixa’ (project 2017RCE03). We extend our gratitude to the regional governments of the Canary Islands and the local councils (Cabildos) of Tenerife (Expte. AFF 144/18 N° Sigma 2018-01976, La Palma (Code A/EST-034/16 DAG/dag N. 201019378, Gran Canaria (SCQ/tsh/sbn N° Expte.: 110/18), La Gomera (Medio ambiente 5059-23-10-2020), El Hierro (N/Ref: MRR/gmq) and Fuerteventura (Medio Ambiente ACE/PRV/prs) for providing the required permits of collection.Peer reviewe