Comparison of Urbanization Effects on Life History Traits in Gambusia Affinis
Date
2023-05
Authors
Edgar, Emily
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Abstract
Impervious surfaces associated with urban development increase the flow of rainwater run-off entering streams that drain urban catchments and drive urban stream syndrome. Urban stream syndrome is the physical and ecological degradation of urban streams. Streams suffering from urban stream syndrome are generally more homogenous with lower levels of habitat structure due to scouring. We define environmental complexity as the degree of variation in stream habitat structure with low variability equating to low environmental complexity. More scoured streams likely have less resources and this could affect life history tradeoffs in fish. We investigated the relationship between environmental complexity and life history traits of the western mosquitofish, Gambusia affinis. Western mosquitofish are urban-tolerant and livebearing species of fish that persist in a wide range of environmental conditions. I examined the fecundity (eggs and embryo), reproductive allotment (egg and embryo mass), and reproductive tradeoff in adult female G. affinis from six different stream populations that vary from high, medium, and low environmental complexity (Pyke GH, 2005). I measured the number of unfertilized gametes and the embryos (and their varying stage of development) in relation to female size and mass. I also measured dried brood mass to explore potential energy tradeoffs in fecundity, and reproductive allotment. I predicted that there would be greater reproductive tradeoff in areas with low environmental complexity due to more predicted limited resources. Specifically, I predicted that fecundity and reproductive allotment would be lower in areas with low environmental complexity. In contrast to our predictions, the fish had higher fecundity in low complexity habitats than in medium and high. Also, the fish had the greatest reproductive allocation in low complexity habitats than in medium and high complexity habitats. I found no significant trade-off across complexity, but high environmental complexity appears to have the highest fecundity and individual propagule mass when compared to low and medium complexity. This suggests that female mosquitofish in these populations are tolerant of a variety of conditions and that might explain their widespread dispersal. But it may account for the loss of intolerant species. With a greater understanding of anthropogenic effects on aquatic vertebrates, we can better understand how to conserve the natural habitat of these ecosystems.
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Keywords
urban stream syndrome, Gambusia affinis, western mosquitofish, urbanization, life history traits
Citation
Edgar, E. (2023). Comparison of urbanization effects on life history traits in Gambusia affinis. Honors College, Texas State University.