Generation and Maintenance of Diversity in an Island: A History of Fragmentation, Secondary Contact and Admixture

Brown, RP ORCID: 0000-0003-2401-6077 and Jin, Y (2026) Generation and Maintenance of Diversity in an Island: A History of Fragmentation, Secondary Contact and Admixture. Journal of Biogeography, 53 (2). ISSN 0305-0270

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Abstract

Aim: To gain detailed insights into how vertebrate intraspecific diversity can be generated and maintained within volcanic islands, using genomic data.

Location: The Canary Islands of Tenerife and La Palma.

Time Period: Tissue samples were obtained in 2003. Genomic analyses were performed in 2023–25.

Taxon: The endemic gecko, Tarentola delalandii.

Methods: Genotyping-by-sequencing of DNA from 109 Tarentola delalandii from the islands of Tenerife (31 sites) and La Palma. SNPs and sequence tags were analysed to identify genomic groups from ancestry coefficients. Bayesian multicoalescent and other phylogenetic approaches allowed determination of relationships among individuals and groups, times of divergence and secondary contact. Levels of admixture were evaluated using hybrid indices, multicoalescent approaches and ancestry coefficients.

Results: Six genomic clusters were detected within Tenerife (plus one from La Palma). Within-island population divergence events beginning some 1.3–2.7 Ma ago explain diversification. Divergence time estimates were more recent than previous mtDNA-based estimates but aligned closely with estimates for other Tenerife species. Population fragmentation on the east coast appears to have been mediated by the Güímar valley mega-landslide some 0.8 Ma ago. Despite strong spatial associations, divergence of lineages to the NW (Teno) and NE (Anaga) of the Teide stratovolcano post-dated the appearance of respective Miocene and Pliocene shield volcanoes. Instead, these long-term geologically stable regions likely provided refugia during eruptions on the central shield. Multiple secondary contact of divergent populations likely occurred in the late Pleistocene. Limited introgression across contact zones has potentially maintained ancient genomic structuring. La Palma was colonized 0.3–0.8 Ma ago from a Tenerife north coast lineage.

Main Conclusions: We outline how present-day spatial genomic structuring might be created and maintained within a small island. Mega-landslides and volcanic eruptions initially fragmented populations during the Pleistocene while limited introgression following secondary contact has maintained stable associations of lineages with geographical areas.

Item Type:	Article
Uncontrolled Keywords:	admixture; biodiversity; divergence time; evolution; gecko; genomics; introgression; volcanic island; 31 Biological Sciences; 3104 Evolutionary Biology; 3105 Genetics; Biodefense; Genetics; Health Disparities and Racial or Ethnic Minority Health Research; Biotechnology; Minority Health; Human Genome; 15 Life on Land; 04 Earth Sciences; 05 Environmental Sciences; 06 Biological Sciences; Ecology; 31 Biological sciences; 37 Earth sciences; 41 Environmental sciences
Subjects:	Q Science > QH Natural history > QH426 Genetics Q Science > QL Zoology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Wiley
Date of acceptance:	4 February 2026
Date of first compliant Open Access:	7 May 2026
Date Deposited:	07 May 2026 11:53
Last Modified:	07 May 2026 11:53
DOI or ID number:	10.1111/jbi.70178
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28534

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