Investigating the genetic footprints of historical temperature selection can get insights to local adaptation and potential influences of climate change on long-term population dynamics. Chicken is a significative species to study genetic adaptation on account of its similar domestication track related to human activity with the most diversified varieties. Yet, few studies have demonstrated the genetic signatures of its adaptation to naturally tropical and frigid environments. Here, we generated whole genome resequencing of 119 domesticated chickens in China including the following breeds which are in order of breeding environmental temperature from more tropical to more frigid: Wenchang chicken (WCC), green-shell chicken (GSC), Tibetan chicken (TBC), and Lindian chicken (LDC). Our results showed WCC branched off earlier than LDC with an evident genetic admixture between WCC and LDC, suggesting their closer genetic relationship. Further comparative genomic analyses SLC33A1 and TSHR genes exhibited stronger signatures for positive selection in the genome of the more tropical WCC. Furthermore, genotype data from about 3,000 African local ecotypes confirmed that allele frequencies of SNPs in these two genes appeared strongly associated with tropical environment adaptation. In addition, the NDUFS4 gene exhibited a strong signature for positive selection in the LDC genome, and SNPs with marked allele frequency differences indicated a significant relationship with frigid environment adaptation. Our findings partially unravel how selection footprints from environmental temperature stress can lead to advantageous genomic adaptions to tropical and frigid environments in poultry and provides a valuable resource for selective breeding of chickens and other domestic animals.

The evolutionary direction of gonochorism and hermaphroditism is an intriguing mystery to be solved. The special transient hermaphroditic stage makes the little yellow croaker (Larimichthys polyactis, L. polyactis) an appealing model for studying the formation of hermaphrodites. On the other hand, as the most famous commercial fish species in East Asia, the origin and evolutionary relationship of L. polyactis and Larimichthys crocea remain unclear. Here, we report the genome sequence of L. polyactis, with a size of ~706 Mb (contig N50 = 1.21 Mb and scaffold N50 = 4.52 Mb) and 25,233 protein-coding genes. Phylogenomic analysis suggests that L. polyactis diverged from the common ancestor of Larimichthys crocea ~25.4 million years ago. Our high-quality genome assembly enabled comparative genomic analysis, which revealed a number of within-chromosome rearrangements and translocations without major chromosome fission or fusion events between the two species. The dmrt1 gene was identified as the candidate sex determination gene in L. polyactis. The expression of dmrt1 and its upstream regulatory gene rnf183 were both sexually dimorphic in the transcriptome analysis. Rnf183, unlike its two paralogues rnf223 and rnf225, is only present in Larimichthys but not in other teleost species, suggesting that it originated from a lineage-specific duplication or was lost in other teleosts. Phylogenetic analysis shows that the hermaphrodite stage in male L. polyactis may be explained by the sequence evolution of dmrt1. Decoding the L. polyactis genome not only provides insight into the genetic underpinnings of hermaphrodite evolution but also provides valuable information for enhancing fish aquaculture.