dc.contributor.author | Delgado Aquije, Maria Lisette | |
dc.date.accessioned | 2021-08-20T13:39:33Z | |
dc.date.available | 2021-08-20T13:39:33Z | |
dc.date.issued | 2021-08-20T13:39:33Z | |
dc.identifier.uri | http://hdl.handle.net/10222/80701 | |
dc.description.abstract | Understanding the molecular mechanisms that differentiate diadromous from freshwater
resident (non-migratory) populations can help understand how species adapt to changing
conditions. In this thesis, I first review the literature concerning diadromy in fishes. I
discuss how diadromy appears to be the product of independent evolutionary events and
how -omics approaches are answering questions regarding the genetic basis, origin, and
loss of this life history trait. Using Galaxias maculatus, an amphidromous fish from the
Southern Hemisphere, as a model and following a RADcap approach, I found that
diadromous individuals comprise mainly one large population across the species
distribution in Chile, while resident populations, particularly those in the northernmost
locations are the product of independent colonization events from a common diadromous
source. These geographically close but genetically distinguishable resident populations
can thus be considered natural replicates derived from a single diadromous population. A
reciprocal transplant experiment consisting of gradual salinity changes with estuarine and
resident individuals from two replicate populations, Toltén and Valdivia, revealed that
Valdivia residents retained the ability to survive in saltwater environments, but Toltén
residents did not. An outlier analysis identified SNPs differentiating diadromy from
residency, and the ability, or lack thereof, to survive in salt water. To further understand
how diadromous, Toltén resident and Valdivia resident individuals acclimate to salt water
and to assess their physiological stress response, I performed an acute salinity change
experiment where salinity was changed from 0 ppt to 23-25 ppt. Diadromous and
Valdivia resident individuals showed no sign of stress 48 hours post-change, while Toltén
residents could not survive the change in salinity. Gill RNAseq analyses revealed key
genes related to osmotic adaptations in G. maculatus and showed differences between
resident populations in the number of genes with retained and lost transcriptional
responses. In Toltén residents, key genes including ion transporters (e.g., CFTR) were not
upregulated in salt water, suggesting a potential mechanism for the loss of salinity
tolerance. Overall, this thesis gives support to the hypothesis that the loss of diadromy
can be achieved by several pathways and that drift likely plays an important role in the
evolution of resident populations. | en_US |
dc.language.iso | en | en_US |
dc.subject | Diadromy | en_US |
dc.subject | Genomics | en_US |
dc.subject | Transcriptomics | en_US |
dc.subject | Salinity tolerance | en_US |
dc.subject | Evolution | en_US |
dc.title | EVOLUTIONARY GENOMICS OF A PLASTIC LIFE HISTORY TRAIT: GALAXIAS MACULATUS AMPHIDROMOUS AND RESIDENT POPULATIONS | en_US |
dc.date.defence | 2021-08-06 | |
dc.contributor.department | Department of Biology | en_US |
dc.contributor.degree | Doctor of Philosophy | en_US |
dc.contributor.external-examiner | Sean Rogers | en_US |
dc.contributor.graduate-coordinator | Alastair Simpson | en_US |
dc.contributor.thesis-reader | Paul Bentzen | en_US |
dc.contributor.thesis-reader | Anne Dalziel | en_US |
dc.contributor.thesis-supervisor | Daniel Ruzzante | en_US |
dc.contributor.ethics-approval | Received | en_US |
dc.contributor.manuscripts | Yes | en_US |
dc.contributor.copyright-release | Not Applicable | en_US |