Pathogenic selection promotes adaptive immune variations against serious bottlenecks in early invasions of bullfrogs

Jiaqi Zhang; Supen Wang; Chunxia Xu; Siqi Wang; Jiacong Du; Meiling Niu; Jiaxue Yang; Yiming Li

doi:10.1016/j.isci.2023.107316

Pathogenic selection promotes adaptive immune variations against serious bottlenecks in early invasions of bullfrogs

iScience. 2023 Jul 10;26(8):107316. doi: 10.1016/j.isci.2023.107316. eCollection 2023 Aug 18.

Authors

Jiaqi Zhang^{1

2}, Supen Wang¹, Chunxia Xu^{1

2}, Siqi Wang^{1

2}, Jiacong Du³, Meiling Niu³, Jiaxue Yang³, Yiming Li^{1

2

3}

Affiliations

¹ Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang, Beijing 100101, China.
² University of Chinese Academy of Sciences Beijing 100049, China.
³ School of Life Sciences, Institute of Life Sciences and Green Development, Hebei University, Baoding 071002, China.

Abstract

Adaptive genetic variations are key for understanding evolutionary processes influencing invasions. However, we have limited knowledge on how adaptive genetic diversity in invasive species responds to new pathogenic environments. Here, we compared variations in immune major histocompatibility complex (MHC) class-II β gene and neutral loci in relation to pathogenic chytrid fungus (Batrachochytrium dendrobatidis, Bd) infection across invasive and native populations of American bullfrog between China and United States (US). Chinese invasive populations show a 60% reduction in neutral cytb variations relative to US native populations, and there were similar MHC variation and functional diversity between them. One MHC allele private to China was under recent positive selection and associated with decreased Bd infection, partly explaining the lower Bd prevalence for Chinese populations than for native US populations. These results suggest that pathogen-mediated selection favors adaptive MHC variations and functional diversity maintenance against serious bottlenecks during the early invasions (within 15 generations) of bullfrogs.

Keywords: Evolutionary biology; Genetics; Zoology.