|Institution:||University of New South Wales|
|Department:||Biological, Earth & Environmental Sciences|
|Keywords:||Adaptation; Life history; Fish; Land; Colonisation; Plasticity|
|Full text PDF:||http://handle.unsw.edu.au/1959.4/54130|
My thesis addressed two questions: whether survival was inferred to have improved for fish that moved onto land, and what the relative role of predation and density were for determining life history variation among populations within one of these land species. For the first question I used life history theory to examine whether survival was inferred to have improved in two fish families which have independently made the transition onto land: Gobiidae and Blenniidae. I examined growth and various aspects of reproductive investment among terrestrial and aquatic species, finding that differences varied according to the level of independence from water. This was consistent with improved survival for certain age classes on land. Nevertheless, the details of life history change differed in each family, with the greatest increases in survival implied for early age classes in Blenniidae, but older age classes in Gobiidae. This suggests fundamental differences in the way the colonization of land occurred in each family. For the second question I investigated the consequences of predation and density on life history variation among five populations of the Pacific leaping blenny Alticus arnoldorum. This fish lives out of the water on rocks in the splash zone of Guam, where it is vulnerable to predation and likely sensitive to changes in population density which impact resource availability. I found the extent to which populations invested in reproduction was inversely related to predation rate, while growth rate appeared to vary largely in response to population density. The differences in life history among populations were also likely to be plastic in the Pacific leaping blenny. My results revealed the interaction between predation and density can lead to complex outcomes in life history, and inferred that plastic life history traits could allow populations to persist in new environments. For example, plasticity in life history may have been an important facilitator for these fish to make the transition onto land in the first place. As a whole, my thesis demonstrates how life history theory, by identifying differences in survival between species and populations respectively, provides a window into the ecological conditions impacting an organism.