Influence of dispersal, natal environment, and variance in reproductive success on the genetic relationships within a population of freshwater fish

reproductive success;paternity;smallmouth bass;dispersal;molecular ecology;microsatellite DNA;parentage assignments

Barthel, Brandon L.

关键词: reproductive success;    paternity;    smallmouth bass;    dispersal;    molecular ecology;    microsatellite DNA;    parentage assignments;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/16761/Barthel_Brandon.pdf?sequence=2&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

There must be genetic change both through time and over space for organisms to adapt to local environmental conditions. Gene flow inhibits genetic differences from accumulating over space, while the magnitude of the variance in reproductive success among adults sets the upper limit on the rate of change through time. The chapters included in this dissertation present a series of investigations into the factors and processes that influenced the magnitude of gene flow among the smallmouth bass that inhabited a small-scale connected river-lake system. In Chapter Two, I determined the distance that smallmouth bass had dispersed from their natal sites during the first year of life and where adult males nested relative to the location of their own natal sites. More than three-quarters of the offspring were captured within 1 km of their natal sites. Nearly a third of the males that hatched in the river habitat were found to have spawned within the same pool in which they hatched and 12% of the males that hatched in the lake habitat nested within 150 m of their natal sites. The fact that many offspring reproduced in close proximity to their natal sites suggests that there would be restricted gene flow over space and strong potential for spatial structure to exist between smallmouth bass at fine spatial scales. Chapter Three examined how the traits of individual parental male smallmouth bass influenced the number of offspring that they contributed to the next generation. Male body size was positively related to reproductive success during the parental care period (i.e., mating success and the number of fry raised to independence) in both the lake and river habitats and to the number of adult male offspring that were found to have been sired by the males that reproduced in the lake. In the river the number of adult male offspring that a male had sired was negatively related to the day of the reproductive period on which it had spawned and unrelated to male body size. These results indicate that different male traits were under selection in the two habitats. In Chapter Four, I evaluated how the ages at which male smallmouth bass spawned for the first time influenced their reproductive lifespans (i.e., the number of reproductive seasons in which they spawned) and the number of offspring they produced during their lifetimes. The males that first spawned at age-6 (i.e., that had delayed first reproduction three years beyond the first age that reproduction was possible, age-3) were found to have had the greatest lifetime reproductive success in the lake, however, males that first spawned at ages 4-6 had very similar success in the river. Reproductive lifespan was found to be positively related to lifetime reproductive success in both habitats. There relationship between parental male age and fertility was stronger among the males that reproduced in the lake than those that spawned in the river. This resulted in there being greater fitness benefits for the males that delayed reproduction beyond the first age possible in the lake than in the river. In Chapter Five, I investigated whether the restricted natal dispersal patterns documented in Chapter Two and the variance in reproductive success reported in Chapters Three and Four were associated with population structure among the male smallmouth bass. Males that nested near each other tended to be more closely related than males on more distant nests in the river, but there was no relationship in the lake. There was consistent genetic differentiation between the males that spawned in the lake versus the river over a number of years and year-classes. There were differences in the gene frequencies of groups of males that spawned in the same habitat in different years, however, they were small relative to the differences between the groups of males that spawned in different habitats in the same year. Chapter Six reported a case of interspecific hybridization between a male smallmouth bass and female largemouth bass that occurred in one reproductive season. Taken as a whole, these studies indicate that restricted natal dispersal is capable of producing genetic differentiation at very fine spatial scales and can be linked to life history divergence when the traits under selection vary over space.