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Ranasinghe, Herath Mudiyanselage Rashika Wijayangani

University of British Columbia

Island ecosystems serve as natural laboratories for studying evolutionary mechanisms due to their unique biodiversity and environmental conditions. In this dissertation I investigate hybridization dynamics, population divergence, and the genetic and biochemical basis of carotenoid-based coloration in island-inhabiting Asian Flameback Woodpeckers from the genera Dinopium and Chrysocolaptes. Using genomic analyses from next-generation sequencing, I examine population genetics across naturally hybridizing Dinopium flameback populations on the island of Sri Lanka. Utilizing pigment characterization via reflectance spectrometry and High-Performance Liquid Chromatography (HPLC), I investigate the molecular and biochemical mechanisms shaping flameback plumage coloration, shedding light on the independent evolution of red dorsal phenotypes across multiple lineages within the yellow-backed flambeacks. Genomic analyses reveal a complex three-way hybrid zone in Dinopium, involving two cryptic D. benghalense populations and an island-endemic D. psarodes population. Hybridization is asymmetric, with D. psarodes alleles introgressing into D. benghalense populations, while local adaptation maintains distinct phenotypic traits. Phylogenetic analyses suggest that Sri Lankan Dinopium populations originated during the late Pleistocene from an ancestor related to the present-day population of D. benghalense tehminae in southwestern India, followed by divergence driven by selection, genetic drift, and isolation by distance. The pigment analysis reveal that D. psarodes’ red plumage is dominated by 4-keto-carotenoids (predominantly astaxanthin), while D. benghalense’s yellow coloration primarily consists of dietary (lutein) and diet-derived (3-dehydro-lutein) carotenoids. Hybrids exhibit an intermediate orange hue, incorporating both types of parental pigments. A genome-wide association study (GWAS) identifies CYP2J2, a gene involved in carotenoid ketolation, as significantly associated with red plumage. Comparative biochemical analysis across five independent red-backed flameback lineages reveal shared and lineage-specific mechanisms for red coloration. While all species possessed 4-keto-carotenoids, Dinopium’s red hue is primarily driven by astaxanthin, whereas Chrysocolaptes species utilize multiple pigments including 4-keto-zeinoxanthin, α-doradexanthin, canthaxanthin, and adonirubin. Additionally, I identified novel carotenoids, including canary-xanthophylls (A and B), papilioerythrinone, phoenicopterone and 4-keto-zeinoxanthin, expanding the biochemical diversity of woodpecker pigmentation. This dissertation provides new insights into the genetic and biochemical pathways shaping carotenoid-based coloration in woodpeckers, elucidating the roles of hybridization, selection, and molecular mechanisms in the evolution of plumage coloration across independent flameback lineages.

Text

2025-06-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/91458

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/