Colette
M. St. Mary
Research Interests
Behavioral
and evolutionary ecology, primarily of fishes
Empirical
and theoretical studies of reproductive ecology and life-history evolution with
a focus on mating systems and sex allocation
Incorporating
behavior and evolutionary processes in fisheries management.
I am primarily a behavioral and evolutionary ecologist. My research interests are in the evolution of mating and sexual systems, the environmental variation that influences this evolution, and the population consequences of the interaction between complex life history and environmental variation. I have primarily worked in aquatic systems using fishes as my model organisms. These basic interests dovetail with current management and conservation issues such as the utilization of novel management tools (such as marine protected areas and artificial reefs) to sustain or recover fisheries. In particular, I am interested in the role of complex life history and behavior in influencing the efficacy of these approaches. Most generally, I seek to understand the interactions among selective forces acting on life history traits and the consequences of those traits for population dynamics and thus evolutionary trajectories.
The approaches I use in my work are driven by my research questions. Thus, my work typically includes field and laboratory observation and experimentation and some form of mathematical modeling (e.g. optimality, population dynamic, genetic algorithms). For specific projects I have also reconstructed phylogenies and am currently developing microsatellite markers to estimate trait heritability and to characterize population genetic structure. I have achieved this diversity in part through collaboration but also by seeking out training and other more informal learning opportunities.
I am working primarily on three projects that, although disparate in focus, are all directly related to my general interests.
The Evolution of Parental Care in the Florida flagfish (Jordanella floridae).
Sexual and natural selection likely interact to influence the
evolution of life history traits. In the case of parental care, life-history theory
tends to focus on the role of natural selection (although the effects of sexual
selection have received recent theoretical attention). When males provide care and vary in the quality
of care they provide, care represents a direct benefit to a female who chooses a
good father. Thus the evolution of
parental care is under sexual as well as natural selection. In collaboration with Kai Lindström (University of Helsinki),
I am pursuing a research program that explores the nature and effects of natural
and sexual selection for care in the Florida flagfish, Jordanella floridae. This
program will lead to new understanding of how these two classes of selection pressures
interact in the evolution of life history traits and contribute to a more general
understanding of why males provide parental care, especially in fishes.
We have a unique opportunity
with the flagfish system to manipulate the strength of natural and sexual
selection
for paternal care and to look among populations that naturally vary in male characteristics.
In particular, unlike many well-studied
parental speci
es (e.g., sticklebacks) care is non-essential in flagfish and thus,
we can quantify the effects of the environment on egg survivorship and
development with and without care. Over the last
2 years, we have found that, 1) males within a population vary in the level of care
they provide, 2) water quality (temperature, salinity, and dissolved O2)
affects egg hatching rates in the absence of care and thus the potential benefits
of care, 3) females base mating decisions, in part, on male care (i.e., nest fanning),
4) males respond by modifying patterns of care to salinity and O2, but
not to temperature or operational sex ratio, and 5) populations varying in the expression
of care. We have also developed two models (the first a dynamic state
variable model and the second a genetic algorithm) to evaluate the pattern of care
and its evolutionary dynamics under the operation of natural selection, sexual selection
or the combination. In flagfish we
have evidence of both and we have planned a series of experiments to evaluate the
relative importance of natural and sexual selection as well as their interaction.
The diversification of hermaphroditism in the genus Lythrypnus (Gobiidae)
Sex allocation theory
is among the most robust bodies of evolutionary
theory available. Nonetheless, within
the Gobiidae there is a diversity of sexual patterns that are not easily understood
with reference to this theory. As an
extension of my dissertation work I have continued to look at the factors that influence
the patterns of sex allocation in one such genus, Lythrypnus. Members of this eastern Pacific and western
Atlantic genus exhibit an unusual form of simultaneous hermaphroditism in which
members of a population vary widely in their allocation to male and female gonadal
tissue (i.e., from pure male to pure female in some species). The few species that have been examined behaviorally
show that individuals do not routinely function as both sexes but instead tend to
express only one gender. As part of
my dissertation work, I developed a dynamic optimization model to evaluate whether
such a pattern could represent an evolutionary stable strategy. Indeed, such a pattern appears to be maintained
by the flexibility in sex allocation and the associated reduction in costs of sex
change.
The genus Lythrypnus includes approximately 18 other species, which range over both temperate and tropical seas, including several species that occur in the Gulf of Mexico, the Atlantic and the Caribbean. These species certainly vary in reproductive seasonality, density and certainly other factors as well. Thus, the genus provides the unique opportunity to test the hypotheses generated from my model by mapping both sexual systems and costs of reallocation on to a phylogeny of Lythrypnus. In doing this, I hope to provide new insight into the factors that have been important in the evolution of this highly flexible sexual system and others like it. In addition, this work has more general application to the field of evolutionary ecology in that it represents an opportunity to explore how the costs of phenotypic plasticity have influenced its evolution.
My focus, since completing my dissertation has been on characterizing the diversity of sexual patterns in the genus, developing a phylogeny for the genus and using my model to explore the effects of putative selection pressures on sexual pattern. I have found a high degree of variation in the distribution of allocation types within and among species in the genus. This diversity has fueled my interest in resolving the phylogenetic relationships among these taxa so that I can more rigorously investigate the selection forces that have lead to the diversification of sexual patterns. Thus far I have found 3 distinct sexual patterns in 6 species and among population variation in sexual pattern in 1 of 2 species examined. Population density appears to explain variation in sexual pattern both among and within species. To better understand the nature of density effects on sex allocation, I have manipulated parameters in my dynamic optimization model to mimic possible effects and have compared the predictions of those models to the empirical patterns. This comparison suggests species differences in the effects of population density on the strength of male competition for mates and the degree of polygyny that I plan to examine empirically.
Complex life history and the population dynamics of harvested species
(Collaborators: Drs. Craig Osenberg and Ben Bolker, Dept. of Zoology,
UF; Dr. Bill Lindberg, Fisheries and
Aquatic Sciences; Mr. Craig
Watson, FAS and the Tropical Aquaculture Lab; and Mr. Ken Nedimyer, Sea Life Inc.)
The field of behavioral
ecology focuses on the consequences of variation in behavior for rates of reproduction,
growth and survival at all life stages of an organism. Despite the importance of behavioral ecology
to population dynamics, the coupling of behavioral ecology and the study and management
of exploited populations remains limited. While at Berkeley, I became interested in integrating fisheries
biology and reproductive behavioral ecology to evaluate how complex mating behavior
could affect population dynamics of harvested species and ultimately how this information
could be incorporated into management strategies. Since coming to UF I have been collaborating primarily with Craig
Osenberg and more recently Ben Bolker in the development of a life history-oriented
approach to reef fish population dynami
cs. The program has numerous components including the development
of population models with which to compare alternative management strategies (e.g.,
marine reserves, artificial reefs, as well as more traditional approaches), a field
component based in the Florida Keys but with comparisons to Caribbean and Pacific
systems, and a meta-analytic component focused on synthesizing the wealth of reef
fish studies in the literature. We
are currently funded to quantify patterns of settlement and movement for reef fishes
that are important to the marine ornamental industry (i.e., the aquarium trade)
as a prelude to the development of a large-scale manipulative experiment to evaluate
the efficacy of artificial reefs as a management tool for that industry. We are not simply interested in this applied
question but instead see the opportunity to evaluate the importance of habitat quality
and density dependence in regulating reef fish populations with complex life histories.
In the longer run one of my goals for this research program is
to characterize the social and behavioral mechanisms that underlie density dependence
in these systems. In particular, density-dependent
effects on rates of social interaction, aggression, and patterns of reproduction.
Ultimately we will incorporate these
processes into more mechanistic population dynamic models.
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(last edited 6/18/02)