Abstract
Polyploidy roles on adaptive evolution and ecological novelty have been extensively studied in plants but remained unclear in vertebrates owing to the rare polyploidy incidences. Here, a huge number of 3105 specimens in Carassius species complex including 2211 hexaploids and 894 tetraploids were sampled from 34 locations through mainland China. And hexaploids had wider geographic distribution than tetraploids especially in the areas with high altitude, high latitude and low annual precipitation. Then, an approximate 1050 bp transferrin (tf) fragments were amplified from all the samples, and 526 tf alleles were identified from a total of 37260 sequences at last. Intriguingly, higher nucleotide diversity of tf alleles in hexaploids than in tetraploids was revealed. Moreover, via phylogenetic analysis of tf alleles, potential origin center of Carassius species complex was deduced to be Yangtze River basin and hexaploids should undergo multiple independent polyploidy origins from sympatric tetraploids. These findings indicate that the hexaploids might possess stronger environmental adaptation and ecological novelty than the tetraploids, which provide an association paradigm of recurrent polyploidy and ecological context in polyploid vertebrates.
Highlights
Polyploidy has been revealed to have significant potentials and evolutionary consequences for increasing allelic diversity, altering genomic complexity, introducing novel traits, and driving ecological transfiguration in plants[1], because it has been found to be ubiquitous and to benefit from both physiological and genetic buffering to provide the raw materials for evolution and adaptation of diverse plants[3,4,5]
Species complex of the genus Carassius that widely distribute across the Eurasian continent[12,13,14], Carassius auratus with 100 chromosomes have been demonstrated as ancestral tetraploids that reproduce by bisexual reproduction[15, 16], whereas Carassius gibelio with 156 or 162 chromosomes[17] have been recognized as hexaploids that are able to reproduce by dual modes of unisexual gynogenesis and bisexual reproduction[3, 18]
Through evolutionary history analyses of two divergent Dmrt[1] genes, tetraploids were proposed to be formed via an early polyploidy event, and hexaploids were suggested to be resulted from ancestral tetraploids via recurrent polyploidy[11, 19] the rare extant case of ancestral tetraploids and recurrent hexaploids from the same evolutionary lineage makes the Carassius species complex as an ideal model to investigate adaptive evolution and ecological novelty of recurrent polyploidy in vertebrates
Summary
Polyploidy has been revealed to have significant potentials and evolutionary consequences for increasing allelic diversity, altering genomic complexity, introducing novel traits, and driving ecological transfiguration in plants[1], because it has been found to be ubiquitous and to benefit from both physiological and genetic buffering to provide the raw materials for evolution and adaptation of diverse plants[3,4,5]. Phylogenetic analysis and genetic diversity were performed by using transferrin (tf) alleles, because tf allele marker had been demonstrated to be valuable for elucidating origin and evolutionary history of the polyploidy Carassius species complex[13, 20] due to its polymorphisms especially in wild populations. Based on these data, we further explored the evolutionary implication for environmental adaptation and ecological novelty of repeated polyploidy from the ancestral tetraploid and recurrent hexaploid complex
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