Abstract
Considering the divergent temperature habitats and morphological traits of four Percidae species: yellow perch (Perca flavescens), Eurasian perch (Perca fluviatilis), pike perch (Sander lucioperca), and ruffe (Gymnocephalus cernua), we stepped into the transcriptome level to discover genes and mechanisms that drive adaptation to different temperature environments and evolution in body shape. Based on 93,566 to 181,246 annotated unigenes of the four species, we identified 1,117 one-to-one orthologous genes and subsequently constructed the phylogenetic trees that are consistent with previous studies. Together with the tree, the ratios of nonsynonymous to synonymous substitutions presented decreased evolutionary rates from the D. rerio branch to the sub-branch clustered by P. flavescens and P. fluviatilis. The specific 93 fast-evolving genes and 57 positively selected genes in P. flavescens, compared with 22 shared fast-evolving genes among P. fluviatilis, G. cernua, and S. lucioperca, showed an intrinsic foundation that ensure its adaptation to the warmer Great Lakes and farther south, especially in functional terms like “Cul4-RING E3 ubiquitin ligase complex.” Meanwhile, the specific 78 fast-evolving genes and 41 positively selected genes in S. lucioperca drew a clear picture of how it evolved to a large and elongated body with camera-type eyes and muscle strength so that it could occupy the highest position in the food web. Overall, our results uncover genetic basis that support evolutionary adaptation of temperature and body shape in four Percid species, and could furthermore assist studies on environmental adaptation in fishes.
Highlights
For the five Perch-likes lineages, 36 genes of higher evolutionary rate were identified in the P. fluviatilis lineage followed by 42, 41, 47, and 91 in P. flavescens, G. cernua, S. lucioperca, and O. niloticus, respectively (141 in D. rerio)
The four Percidae fish involved in this study showed differences in adaptation to temperature environment and body shape, to some extent
The findings of this study are not able to confirm any "signature of selection", there are indications that selective processes in the transcriptome could be enacted to allow these Percidae fish to locally adapt to different ranges of temperature, and explain the evolutionary difference in body shape, to some extent
Summary
While reading the book Adaptation and Natural Selection, the preface sentence “Natural selection is the only acceptable explanation for the genesis and maintenance of adaptation,” will. “adaptive evolution” and “evolutionary adaptation” have been documented by researchers’ studies on numerous organisms; either way, natural selection is still the most critical part Both adaptation and evolution are inseparable from organisms and the environment. Most functions and gene expression are regulated by environmental factors like temperature, dissolved oxygen, and osmotic pressure Influences like this often determine the fitness of fish in diverse environments. The body could be well shaped for better swimming and occupying a unique ecological niche Such fitness should be the purposeful evolution of fish during their adaptation, and may eventually lead to the speciation. We conducted comprehensive investigations through RNAsequencing of the four species and bioinformatic analysis to explore the above assumptions and evolutionary mechanisms that support ecological adaptation of temperature and body shape among these four Percid species
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