A conserved haplotype controls parallel adaptation in geographically distant salmonid populations

TLDR

Salmonid fishes exhibit extensive local adaptation driven by environmental variation and natal homing, making conservation and restoration difficult because defining clear conservation units is hard and translocation often fails due to mismatched adaptation. A better understanding of the genetic architecture of local adaptation in salmonids could provide valuable information to assist in conserving and restoring natural populations of these important species. We combined laboratory crosses and next‑generation sequencing to study the genetic architecture underlying rapid development in two geographically distant rainbow trout populations. We discovered that a conserved haplotype underlies parallel rapid development in both populations, suggesting that shared adaptive genetic variation across distant salmonid populations may be common and important for conservation.

Abstract

Abstract Salmonid fishes exhibit extensive local adaptations owing to abundant environmental variation and precise natal homing. This extensive local adaptation makes conservation and restoration of salmonids a challenge. For example, defining unambiguous units of conservation is difficult, and restoration attempts often fail owing to inadequate adaptive matching of translocated populations. A better understanding of the genetic architecture of local adaptation in salmonids could provide valuable information to assist in conserving and restoring natural populations of these important species. Here, we use a combination of laboratory crosses and next‐generation sequencing to investigate the genetic architecture of the parallel adaptation of rapid development rate in two geographically and genetically distant populations of rainbow trout ( Oncorhynchus mykiss ). Strikingly, we find that not only is a parallel genetic mechanism used but that a conserved haplotype is responsible for this intriguing adaptation. The repeated use of adaptive genetic variation across distant geographical areas could be a general theme in salmonids and have important implications for conservation and restoration.