Historic black rat invasions into Sri Lanka lead to hybridization forming two sub-lineages in the <em>Rattus rattus</em> species complex

• Main Authors: P. P. C. Hemamali, S. H. Boyagoda
• Format: Article
• Language: English
• Published: Faculty of Science, University of Peradeniya, Sri Lanka 2020-12-01
• Series: Ceylon Journal of Science
• Subjects: subspecies, mitochondrial inrogression, muroid
• Online Access: https://cjs.sljol.info/articles/7823

<p>In this work, we used two mitochondrial (16S rRNA and cytochrome-<em>b</em>) and one nuclear (Rag 1) gene fragments to analyse phylogeographic history of black rats in Sri Lanka at subspecies level. Of the five subspecies recorded in Sri Lanka three (<em>Rattus rattus kelaarti</em>, <em>R.r. rufescens</em>, <em>R. r. kandianus</em>) are believed to have invaded Sri Lanka in prehistoric times and two (<em>R.r. alexandrinus</em>, <em>R. r. rattus</em>) in the recent past through trade ships from Europe and India. All subspecies, except <em>R. r. kandianus</em>, have restricted destribution with none occuring sympatrically. <em>Rattus r. kandianus </em>is widely destributed throughout the country. In the phylogeny, all black rats from Sri Lanka fell into the <em>Rattus rattus </em>complex lineage I. But, <em>R.r. kelaarti</em>, <em>R.r. rufescens </em>most of <em>R.r. kandianus </em>and one individual of <em>R.r. alexandrinus </em>formed a unique Sri Lankan sub-lineage within the lineage I. The results suggests hybridization with mitochondrial introgression of the endemic <em>R.r. kandianus </em>with all other subspecies separately. Introgression of <em>R.r. alexandrinus </em>mitochondrial DNA into a subpopulation of <em>R.r. kandianus </em>is responsible for placing few individuals of the latter in the widespead sub-lineage in the Lineage I with <em>R.r. alexandrinus </em>and <em>R. rattus </em>from other parts of the world. The fifth subspecies, <em>R.r. rattus </em>which was reported in small numbers from ports in 1930s, has most likely been replaced by <em>R.r. alexandrinus.</em></p>