Environmental change: Consequences for life history, morphology and behavior

Exponential growth in human populations and expanding development have and will continue to cause a variety of environmental changes. The objective of the studies presented here was to examine some of the possible consequences of change on aquatic organisms. Chapter 1 examines the impacts of habitat alteration and nutrient enrichment on the life history of an aquatic snail, Lymnaea elodes, in lakes on the North Slope of Alaska. The study focused on two traits, offspring size and number, and used a combination of comparative and experimental approaches. The main results of this study showed that snails in lakes with a predator on the adult stage (trout, Salvelinus namaycush) produced larger numbers of smaller offspring than snails in lakes that lack trout. These results support life history theory when age-specific mortality varies. Individual snails did not show significant differences in offspring number in response to variation in lake productivity or nutrient additions.; Chapter 2 examines the influence of changes in habitat availability on a semi-aquatic anuran (Acris crepitans). Other than the occasional slough or oxbow there are no natural lakes or ponds in Kansas. The construction of reservoirs and ponds has resulted in the availability of a novel habitat for cricket frogs. I examined whether there are differences in morphology and locomotor performance between frogs from streams and ponds. The results of this study show that frogs from pond sites are smaller, but have longer tibio-fibulas. Pond individuals also jump longer distances, and I hypothesized that fluctuating water levels in constructed ponds may have driven the divergence between stream and pond populations.; The final chapter takes a different approach to the issue of the effects of environmental change. Gambusia affinis, the mosquitofish, is a small poeciliid fish that has been introduced worldwide and has rapidly expanded its range. One of the goals was to examine whether there are life history differences between G. affinis and six related species that show restricted distributions. G. speciosa was one of the species included in the comparison and this report is the first description of this recently described species life history.