Adaptation (Biology)

Urbanization and land development, climate change, pollution, the spread of invasive species, and sea level rise are unprecedented challenges that have led to 25% of avian species worldwide facing an elevated risk of extinction. Under rapidly changing environmental conditions, traditional population models are not ideal because they typically assume that demographic parameters are static in order to estimate the probability of species extinction over a chosen timeframe. This assumption disregards species’ potential to adapt to environmental change; adaptations which could alter not only a species’ extinction outlook but also its legal protection status. The goal of my PhD research is to re-evaluate the risk of extinction of one threatened species, the Wood Stork (Mycteria americana), by accounting for potential adaptation in the context of planned and predicted changes in the southeastern United States. Since the 1970s, Wood Storks have shifted the timing of their breeding season, expanded their range northward and into novel habitats in urban areas, and begun consuming non-native fishes. I investigate these observations by comparing the physiology and diet of Wood Storks nesting in the historical core of their U.S. range (tree islands in the flooded Everglades marsh) with storks occupying novel habitats in urban and temperate locations. Faster growth rate, improved body condition, and increased survival by nestlings in urban areas would be evidence that colonies on the leading edge of the species’ range may be capable of sustaining growth of the whole population. In a third and final chapter, I forecast nest abundance and distribution patterns in the entirety of the U.S. range given various hydrological scenarios. Increased Wood Stork population size and stability are recovery criteria which must be met before the species can qualify for removal from the federal Endangered Species List. More broadly, understanding Wood Stork response to human development in the Everglades illuminates general patterns in avian species response to extreme changes in landscape, and could serve as a framework for proactively incorporating evolutionary potential into the framework of Endangered Species Act recovery in other species which have a high adaptive capacity.

Loggerhead and green turtle neonates migrate from Florida's coast during a 24-36
h frenzy. Post-frenzy loggerheads are often found in flotsam (Sargassum), while postfrenzy
green turtles "disappear." This study compared the frenzy and post-frenzy activity
of each species, their response to flotsam (in the laboratory and field), and the role of
experience in habitat selection. Both species were most active during day I; activity
thereafter declined (especially in loggerheads). Inactive loggerheads occupied Sargassum
and open water (day or night) whereas inactive green turtles occupied Sargassum by day
and both habitats at night. Exposure to Sargassum had no effect on the later habitat
choices ofloggerheads, while exposed green turtles preferred Sargassum over plastic
plants. In the field, both species preferred flotsam to open water, but occupied distinct
microhabitats. Loggerheads preferred the mat surface while green turtles hid within the
mat. Differences in activity and habitat selection likely reflect species-specific migratory
and anti-predator strategies.

Elasmobranchs (sharks, skates, and rays) migrate across a wide range of
spatiotemporal scales, display philopatry, seasonal residency, and maintain
home ranges. Many animals use the Earth’s magnetic field to orient and navigate
between habitats. The geomagnetic field provides a variety of sensory cues to
magnetically sensitive species, which could potentially use the polarity, or
intensity and inclination angle of the field, to derive a sense of direction, or
location, during migration. Magnetoreception has never been unequivocally
demonstrated in any elasmobranch species and the cognitive abilities of these
fishes are poorly studied. This project used behavioral conditioning assays that
paired magnetic and reinforcement stimuli in order to elicit behavioral responses.
The specific goals were to determine if the yellow stingray, Urobatis jamaicensis,
could detect magnetic fields, to quantify the nature of the magnetic stimuli it could
detect, and to quantify the learning and memory capabilities of this species. The results supported the original hypotheses and demonstrated that the yellow
stingray could: discriminate between magnetic and non-magnetic objects; detect
and discriminate between changes in geomagnetic field strength and inclination
angle; and use geomagnetic field polarity to solve a navigational task. The yellow
stingray learned behavioral tasks faster and retained the memories of learned
associations longer than any batoid (skate or ray) to date. The data also suggest
that this species can classify magnetic field stimuli into categories and learn
similar behavioral tasks with increased efficiency, which indicate behavioral
flexibility. These data support the idea that cartilaginous fishes use the
geomagnetic field as an environmental cue to derive a sense of location and
direction during migrations. Future studies should investigate the mechanism,
physiological threshold, and sensitivity range of the elasmobranch magnetic
sense in order to understand the effects of anthropogenic activities and
environmental change on the migratory ability of these fishes.

The channelized Kissimmee River experiences seasonally low dissolved oxygen levels
which have changed the ecosystem to favor air-breathing species, while gamefish
populations have declined greatly. In 2001 , the central portion of the river (Pool C) was
physically restored.
To evaluate the usefulness of various stress markers and assess the success of the partial
restoration, the stress responses were analyzed (brain monoamines, heat shock proteins,
and plasma cortisol) of air-breathing fish (bowfin, Florida gar), versus gamefish
(largemouth bass and bluegill sunfish). Fish were collected from hypoxic and normoxic
water at three sites in the Kissimmee River. Statistical analysis (MANOV A) showed
overall significantly higher stress response in hypoxic gamefish than those in normoxia,
with higher hsp72 levels, DOPAC, and Dopamine turnover (DOPAC:DA). Hsp60 and
cortisol was significantly higher only in hypoxic bass while serotonin and 5-HIAA were
significantly higher in hypoxic bluegill sunfish. Air-breathers did not show higher stress
levels during hypoxia.

Larval release by adult fiddler crabs occurs during the ebbing tides, but its timing
relative to the day-night and tidal amplitude cycles depends upon tidal form (e.g., shows
phenotypical plasticity). Crabs (Uca thayeri) from Florida's East Coast are exposed to
semidiurnal tides and release their larvae at night, whereas crabs from Florida's West
Coast exposed to mixed tides release their larvae during the afternoon. The purpose of
this study was to determine whether the larvae could hatch at times other than those
correlated with the tidal form at their location. Clusters of eggs at similar stages of
development, 24-72 h in advance of release, were reciprocally transferred between
females from each coast. Release ofboth the transferred larvae and maternal clutch
occurred synchronously, and at the time dictated by the female's tidal regime. These
results suggest that larvae are phenotypically plastic with respect to hatching time and
can either delay (West coast) or advance (East coast) their response to release signals
from females.

Sharks possess an electrosensory system which allows the detection of
electric fields . How this system varies among related taxa and among species
inhabiting different environments remains unexplored. Electroreceptor number
was quantified for representative species of related taxa (genera, families, orders)
from different environments (pelagic, coastal, deepwater) and taxa from similar
environments to determine potential phylogenetic constraint or evolutionary
convergence. Coastal open water sharks possess the greatest number of
electroreceptors; deepwater sharks the least. Pelagic and coastal benthic sharks
retain comparable electrosensory pore numbers despite inhabiting vastly different
environments. Electrosensory pores were primarily located in ventral
distributions, except among coastal open water sharks which possess roughly
even distributions around the head. Among related species and genera, pore
numbers and distribution are comparable, with greater variation among higher
taxa. Results implicate evolutionary convergence as the primary influence in
electroreceptor development, while phylogenetic constraint establishes similar
base values for number and distribution.

Crude oil causes both lethal and sublethal effects on marine organisms, but the
impact upon sensory function remains unexplored. Elasmobranchs rely upon the effective
functioning of their sensory systems for use in feeding, mating, and predator avoidance.
The objective of this study was to test the effect of crude oil upon the olfactory and
electroreceptive sensitivity of the Atlantic stingray, Dasyatis sabina. The magnitudes of
the electro-olfactogram (EOG) responses were significantly depressed by 26% (Glutamic
Acid) to 157% (Cysteine) for all amino acids when stingrays were exposed to crude oil.
The shapes of the EOG responses when exposed to oil were also significantly different,
exhibiting a more protracted response compared to un-exposed stingrays. Oil exposed
stingrays exhibited a significant decrease in orientation distance to prey-simulating
electric fields. This study is the first to quantify the effects of crude oil on olfactory and
electrosensory sensitivity of marine predators.

Mesophotic reefs represent biodiverse ecosystems that may act as a refuge for
depth-generalist coral species threatened in shallow habitats. Despite the importance of
coral-algal symbioses, few studies focus on mesophotic zooxanthellae assemblages and
their influence on connectivity. This study compared zooxanthellae in Montastraea
cavernosa at shallow and mesophotic depths at Flower Garden Banks National Marine
Sanctuary and McGrail Bank. Mesophotic corals contained more zooxanthellae and more
chlorophyll a and c2 per unit area coral. Increased zooxanthellae within mesophotic
corals may represent an adaptive strategy to optimize light capture in low-light
environments. Genetic profiles for zooxanthellae assemblages from shallow and
mesophotic corals showed similar diversity across banks and between depths. The
dominant sequence making up assemblages was identified as Symbiodinium type C1.
Similar assemblage diversity suggests that zooxanthellae assemblages will not limit
connectivity potential between shallow and mesophotic corals at these reefs.

The Roatan Spiny-tailed Iguana (Ctenosaura oedirhina) is endemic to the 146-km2 island of Roatn, Honduras. Harvesting for consumption, fragmentation of habitat, and predation by domestic animals threaten this lizard. It is currently listed as Endangered by the International Union for Conservation of Nature (IUCN), as threatened by the Honduran government, and is on Appendix II of the Convention on International Trade in Endangered Species (CITES). This species has been geographically fragmented and genetically isolated into small subpopulations that are declining in density. With data gathered from use/availability surveys, resource selection functions were used to identify habitats and environmental variables associated with their presence. Results indicate that protection from harvesting is the most important factor in determining their distribution. These high-density populations are currently restricted to ~0.6 km2. Organisms living in small, isolated populations with very restricted ranges are at higher risk of extirpation due to various direct and indirect forces. Mark-recapture-resight surveys and distance sampling have been used to monitor the populations since 2010 and 2012 respectively. The data show that the high-density populations are declining. The current population size is estimated to be 4130-4860 individuals in 2015. A population viability analysis (PVA) was conducted to identify the most pressing threats and specific life history traits that are affecting this decline. The analysis estimates that if current trends persist, the species will be extinct in the wild in less than ten years. Adult mortality is a main factor and female mortality specifically characterizes this decline. In order for this species to persist over the next fifty years, adult mortality needs to be reduced by more than 50%. A lack of enforcement of the current laws results in the persistence of the main threat, poaching for consumption, thus altering the species distribution and causing high adult mortality. This is complicated by social customs and a lack of post primary education. Management changes could mitigate this threat and slow the population decline. Recommendations include an education campaign on the island, increased enforcement of the current laws, and breeding of C. oedirhina in situ and ex situ for release into the wild.

The spread of nonnative invasive species has become the second greatest threat to global biodiversity, making management of invasive species a critical component of the conservation of biodiversity worldwide. Managers and conservation biologists often lack basic life history data, as well as quantitative and theoretical models to predict risk of invasion or other negative effects. I contribute information to both categories by providing life history information (diet and morphology) of the Purple Swamphen (Porphyrio porphyrio) and by characterizing the invasion pathways that nonnative avian species in Florida follow. I found Purple Swamphens are predominantly eating and selecting for Eleocharis cellulosa. Additionally, there is a large amount of variation in nonnative avian species’ propensity to colonize natural habitat and the time it takes to do so. Nine out of 15 species investigated colonized natural habitat and the time it took them to do so ranged from 8 to 41 years. It is through a combination of various techniques that ecologists will begin to fully understand the importance of studying nonnative species as well as reducing the impact that nonnatives have on native ecosystems.