The mention of commercial product trade names in this report does not constitute endorsement or r... more The mention of commercial product trade names in this report does not constitute endorsement or recommendation for use by the Fish and Wildlife Service, U.S. Department of the Interior. The ecology of regularly flooded salt marshes of
The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United St... more The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United States managed as a National Wildlife Refuge and a National Wilderness Area. Wild- fires frequently occur, modifying vegetation structure and creating the swamp landscape mosaic. Following extensive wildfires in 1954- 1955, the Suwannee River was impounded by a dam (Suwannee River Sill) built outside the Wilderness Area but within the Refuge to exclude fire reoccurrence. By the late 1980s indications were that fire was not being excluded, although the swamp hydrology and vegetation suggested changes due to extended hydroperiod. The dam's effects were delineated with a spatial hydrology model and studies of species' hydrological sensitivities, and an Environmental Assessment considered the multiple uses and management goals to determine the best sill management alternative. The Okefenokee Swamp is a 200,000 ha palustrine, fresh- water wetland in southeast Georgia and northeast Flori...
The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just ... more The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just downstream of the Savannah National Wildlife Refuge (SNWR), which is one of the nation’s largest freshwater tidal marshes. The Lower Savannah River estuary has been studied for years by governmental agencies, water users, universities, and consultants having an interest in controlling water quality and predicting the potential impacts of a proposed harbor deepening. Consequently, many different databases have been created that describe the natural system’s complexity and behaviors. Variables having particular relevance include those describing bathymetry, meteorology, water level, and specific conductance. To evaluate the environmental impacts of the deepening, a three-dimensional hydrodynamic model (3DM) and a “marsh succession model” (MSM) were developed by different scientific teams. The 3DM predicts changes in riverine water levels and salinity in the system in response to potential ...
Invasive exotic species are spreading rapidly throughout the planet. These species can have wides... more Invasive exotic species are spreading rapidly throughout the planet. These species can have widespread impacts on biodiversity, yet the ability for native species, particularly long-lived vertebrates, to respond rapidly to invasions remains mostly unknown. Here we provide evidence of rapid morphological change in the endangered snail kite (Rostrhamus sociabilis) across its North American range with the invasion of a novel prey, the island apple snail (Pomacea maculata), a much larger congener of the kite's native prey. In less than one decade since invasion, snail kite bill size and body mass increased substantially. Larger bills should be better suited to extracting meat from the larger snail shells, and we detected strong selection on increased size through juvenile survival. Using pedigree data, we found evidence of both genetic and environmental influences on trait expression and discovered that additive genetic variation in bill size increased with invasion. However, trends...
While variation in age structure over time and space has long been considered important for popul... more While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997-2013). We find that in the southern region of the snail kite-a region known to be critical for the long-term persistence of the spec...
Understanding the spatial scale of population structure is fundamental to long-standing tenets of... more Understanding the spatial scale of population structure is fundamental to long-standing tenets of population biology, landscape ecology and conservation. Nonetheless, identifying such scales has been challenging because a key factor that influences scaling - movement among patches or local populations - is a multicausal process with substantial phenotypic and temporal variation. We resolve this problem via a novel application of network modularity. When applied to movements, modularity provides a formal description of the functional aggregation of populations and identifies potentially critical scales for ecological and evolutionary dynamics. We first test for modularity using several different types of biologically relevant movements across the entire geographic range of an endangered bird, the snail kite (Rostrhamus sociabilis plumbeus). We then ask whether variation in movement based on (i) age, (ii) sex and (iii) time (annual, seasonal and within-season movements) influences spa...
The mention of commercial product trade names in this report does not constitute endorsement or r... more The mention of commercial product trade names in this report does not constitute endorsement or recommendation for use by the Fish and Wildlife Service, U.S. Department of the Interior. The ecology of regularly flooded salt marshes of
The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United St... more The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United States managed as a National Wildlife Refuge and a National Wilderness Area. Wild- fires frequently occur, modifying vegetation structure and creating the swamp landscape mosaic. Following extensive wildfires in 1954- 1955, the Suwannee River was impounded by a dam (Suwannee River Sill) built outside the Wilderness Area but within the Refuge to exclude fire reoccurrence. By the late 1980s indications were that fire was not being excluded, although the swamp hydrology and vegetation suggested changes due to extended hydroperiod. The dam's effects were delineated with a spatial hydrology model and studies of species' hydrological sensitivities, and an Environmental Assessment considered the multiple uses and management goals to determine the best sill management alternative. The Okefenokee Swamp is a 200,000 ha palustrine, fresh- water wetland in southeast Georgia and northeast Flori...
The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just ... more The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just downstream of the Savannah National Wildlife Refuge (SNWR), which is one of the nation’s largest freshwater tidal marshes. The Lower Savannah River estuary has been studied for years by governmental agencies, water users, universities, and consultants having an interest in controlling water quality and predicting the potential impacts of a proposed harbor deepening. Consequently, many different databases have been created that describe the natural system’s complexity and behaviors. Variables having particular relevance include those describing bathymetry, meteorology, water level, and specific conductance. To evaluate the environmental impacts of the deepening, a three-dimensional hydrodynamic model (3DM) and a “marsh succession model” (MSM) were developed by different scientific teams. The 3DM predicts changes in riverine water levels and salinity in the system in response to potential ...
Invasive exotic species are spreading rapidly throughout the planet. These species can have wides... more Invasive exotic species are spreading rapidly throughout the planet. These species can have widespread impacts on biodiversity, yet the ability for native species, particularly long-lived vertebrates, to respond rapidly to invasions remains mostly unknown. Here we provide evidence of rapid morphological change in the endangered snail kite (Rostrhamus sociabilis) across its North American range with the invasion of a novel prey, the island apple snail (Pomacea maculata), a much larger congener of the kite's native prey. In less than one decade since invasion, snail kite bill size and body mass increased substantially. Larger bills should be better suited to extracting meat from the larger snail shells, and we detected strong selection on increased size through juvenile survival. Using pedigree data, we found evidence of both genetic and environmental influences on trait expression and discovered that additive genetic variation in bill size increased with invasion. However, trends...
While variation in age structure over time and space has long been considered important for popul... more While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997-2013). We find that in the southern region of the snail kite-a region known to be critical for the long-term persistence of the spec...
Understanding the spatial scale of population structure is fundamental to long-standing tenets of... more Understanding the spatial scale of population structure is fundamental to long-standing tenets of population biology, landscape ecology and conservation. Nonetheless, identifying such scales has been challenging because a key factor that influences scaling - movement among patches or local populations - is a multicausal process with substantial phenotypic and temporal variation. We resolve this problem via a novel application of network modularity. When applied to movements, modularity provides a formal description of the functional aggregation of populations and identifies potentially critical scales for ecological and evolutionary dynamics. We first test for modularity using several different types of biologically relevant movements across the entire geographic range of an endangered bird, the snail kite (Rostrhamus sociabilis plumbeus). We then ask whether variation in movement based on (i) age, (ii) sex and (iii) time (annual, seasonal and within-season movements) influences spa...
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