Early life history of a landlocked amphidromous fish: migration, critical traits and ontogeny

Life-history plays a key role in determining species distributions and population structuring. Many studies evaluate the role of adult characteristics when predicting species distribution and population structuring, but very few evaluate the role of early life-history which is often the most vulnerable, and therefore limiting, phase of life-history. This thesis examines the role of early life-history in distribution and population structuring leading to divergence, and potentially speciation, by evaluating short and long term population structuring mechanisms, and the role of early life-history alteration in a facultatively amphidromous fish. Landlocked populations of Galaxias brevipinnis were found to be genetically divergent from diadromous populations, despite no obvious physical barriers to population connectivity. On shorter timescales, catchment level meta-populations were formed within lakes and along coasts. Larvae were found to be highly rheotactic through lab trials, and the majority of larvae were found to be retained within river plumes through larval trawling and otolith microchemistry, suggesting a simple behavioural mechanism responsible for both the long term isolation leading to divergence and short term meta-population structuring patterns seen here. Egg and larval size was larger in diadromous populations than in landlocked populations suggesting a potential pathway for the formation of landlocked populations and adaptation to local conditions. Despite size differences, responses to behavioural cues were similar in both diadromous and landlocked populations likely due to retaining a bipartite fluvial-pelagic life-history pattern. A review of amphidromous fish shows landlocking and life-history plasticity is common both within species and families, suggesting patterns seen here may be applicable across many amphidromous fish taxa. Further, the consistent use of pelagic rearing environments highlights amphidromy as an obligate benthic-pelagic migration where the various life-history patterns are a response to landscape centered on rapidly moving larvae to a pelagic environment. This thesis shows landlocked populations of an amphidromous fish diverging from their diadromous counterparts, due to a simple behavioural response, resulting in adaptation of early life-history in a novel environment, allowing fecundity optimization and providing the potential for context dependent isolation, adaptation, divergence and speciation

Are Land-use Changes Reflected in Diets of Mourning Doves (Zenaida macroura) in Eastern South Dakota

Food habits of the mourning dove (Zenaida macroura) have been extensively studied in the southern United States (McClure 1943, Korschgen 1958, Carpenter 1971) and consist primarily of vegetable matter throughout their range (Beckwith 1959). Diet studies in several states have indicated agricultural crops, specifically corn and wheat, were the most readily consumed plant seeds (Korshgen 1958, Carpenter 1971). Similarities observed in diets of doves were dependent on the agricultural crops available within the area. For example, in Missouri, some seasonal variability was documented suggesting doves forage based on food availability as much as by food preference (Korschgen 1958). However, in the agriculturally dominated landscape of east central South Dakota (SD), the two most important food items for doves were green (Setaria viridis) and yellow foxtail (S. glauca; Van’t Hul and Jenks 1992)

NOTES: ARE LAND-USE CHANGES REFLECTED IN DIETS OF MOURNING DOVES (ZENAIDA MACROURA) IN EASTERN SOUTH DAKOTA

Food habits of the mourning dove (Zenaida macroura) have been extensively studied in the southern United States (McClure 1943, Korschgen 1958, Carpenter 1971) and consist primarily of vegetable matter throughout their range (Beckwith 1959). Diet studies in several states have indicated agricultural crops, specifically corn and wheat, were the most readily consumed plant seeds (Korshgen 1958, Carpenter 1971). Similarities observed in diets of doves were dependent on the agricultural crops available within the area. For example, in Missouri, some seasonal variability was documented suggesting doves forage based on food availability as much as by food preference (Korschgen 1958). However, in the agriculturally- dominated landscape of east central South Dakota (SD), the two most important food items for doves were green (Setaria viridis) and yellow foxtail (S. glauca; Van’t Hul and Jenks 1992). Large-scale land use changes have occurred in eastern South Dakota in the past few decades and several factors have contributed to increased grassland to cropland conversion (Wright and Wimberly 2013). Conversion of grasslands to agricultural crops has increased as demand for biofuels and commodity prices increased (Secchi and Babcock 2007, Searchinger et al. 2008, Fargione et al. 2009, Wright and Wimberly 2013). In east central South Dakota, corn and soybean plantings have increased from 2,400,000 ha in 1991 to 4,400,000 ha in 2013 (United States Department of Agriculture 2014). These significant land-use changes that have occurred in the intervening 20 years may influence mourning dove feeding habits. We compared mourning dove diet composition in Minnehaha County, South Dakota, USA, to those published 20 years earlier from a study conducted approximately 60 km north (Van’t Hul and Jenks 1992)

NOTES: ARE LAND-USE CHANGES REFLECTED IN DIETS OF MOURNING DOVES (ZENAIDA MACROURA) IN EASTERN SOUTH DAKOTA

Food habits of the mourning dove (Zenaida macroura) have been extensively studied in the southern United States (McClure 1943, Korschgen 1958, Carpenter 1971) and consist primarily of vegetable matter throughout their range (Beckwith 1959). Diet studies in several states have indicated agricultural crops, specifically corn and wheat, were the most readily consumed plant seeds (Korshgen 1958, Carpenter 1971). Similarities observed in diets of doves were dependent on the agricultural crops available within the area. For example, in Missouri, some seasonal variability was documented suggesting doves forage based on food availability as much as by food preference (Korschgen 1958). However, in the agriculturally- dominated landscape of east central South Dakota (SD), the two most important food items for doves were green (Setaria viridis) and yellow foxtail (S. glauca; Van’t Hul and Jenks 1992). Large-scale land use changes have occurred in eastern South Dakota in the past few decades and several factors have contributed to increased grassland to cropland conversion (Wright and Wimberly 2013). Conversion of grasslands to agricultural crops has increased as demand for biofuels and commodity prices increased (Secchi and Babcock 2007, Searchinger et al. 2008, Fargione et al. 2009, Wright and Wimberly 2013). In east central South Dakota, corn and soybean plantings have increased from 2,400,000 ha in 1991 to 4,400,000 ha in 2013 (United States Department of Agriculture 2014). These significant land-use changes that have occurred in the intervening 20 years may influence mourning dove feeding habits. We compared mourning dove diet composition in Minnehaha County, South Dakota, USA, to those published 20 years earlier from a study conducted approximately 60 km north (Van’t Hul and Jenks 1992)

Predictors of Pesticide Concentrations in Freshwater Trout – The Role of Life History.

Concentrations of halogenated pesticides in freshwater fish can be affected by age, size, trophic position, and exposure history. Exposure history may vary for individual fish caught at a single location due to different life histories, e.g. they may have hatched in different tributaries before migrating to a specific lake. We evaluated correlations of pesticide concentrations in freshwater brown trout (Salmo trutta) from the Clutha River, New Zealand, with potential predictors including capture site, age, length, trophic level, and life history. Life history was determined from otolith (fish ear bone) strontium isotope signatures, which vary among tributaries in the region of our study. Variability in pesticide concentrations between individual fish was not well explained by capture site, age, length, or trophic level. However, hexachlorobenzene (HCB) and chlorpyrifos concentrations were distinct in lake-based trout with different life histories. Additionally, one of the riverine life histories was associated with relatively high concentrations of total endosulfans. Linear models that included all potential predictor variables were evaluated and the resulting best models for HCB, chlorpyrifos, and total endosulfans included life history. These findings show that in cases where otolith isotope signatures vary geographically, they can be used to help explain contaminant concentration variations in fish caught from a single location