Thesis Abstract
Members of the annual killifish genus Austrolebias live in temporary ponds across South
America and possess a remarkable life cycle. These fish live in small ponds that dry out
completely; killing the adults but not before they have laid eggs in the substrate of their pond.
The desiccation-resistant eggs develop during the dry season, going through multiple stages
of diapause until the next wet season rains trigger hatching and the cycle is repeated. There is
considerable variation in size in Austrolebias, the largest species can reach up to 150mm in
length while the typical size is just 40mm. Phylogenetic trees and species distribution models
were built and used together to identify the factors that influence patterns of co-occurrence
within this genus. Differences in growth and morphology among Austrolebias species were
examined to quantify how differences in growth pattern can lead to the large variation in size
and shape seen within the genus. Genomic data was generated for hybrid offspring of two
species of Austrolebias using double-digest RAD sequencing. These data were then used to
build linkage maps that were in turn used to identify any regions associated with sex
determination and potential chromosomal rearrangements. At a broader scale, a generic-level
tree for the order Cyprinodontiformes was constructed. Austrolebias is a member of this
order, as well as many model fish genera such as Fundulus, Nothobranchius and Poecilia.
Two extraordinary reproductive life-history adaptations have evolved in this order; viviparity
and annualism. The new tree was used to determine whether the evolution of viviparity or
annualism lead to increased rates of diversification. Finally this generic-level tree was used to
examine patterns of positive selection in the low-light vision gene, rhodopsin and whether
sites under selection were linked to functional changes
