Spatial models of metapopulations and benthic communities in patchy environments
Citable URI
https://hdl.handle.net/1912/4124Location
Gulf of MaineDOI
10.1575/1912/4124Abstract
The distribution of organisms in space has important consequences for the function
and structure of ecological systems. Such distributions are often referred to as patchy,
and a patch-based approach to modeling ecosystem dynamics has become a major
research focus. These models have been used to explore a wide range of questions
concerning population, metapopulation, community, and landscape ecology, in both
terrestrial and aquatic systems.
In this dissertation I develop and analyze a series of spatial models to study the dynamics
of metapopulations and marine benthic communities in patchy environments.
All the models have the form of a discrete-time Markov chain, and assume that the
landscape is composed of discrete patches, each of which is in one of a number of
possible states. The state of a patch is determined by the presence of an individual
of a given species, a local population, or a group of species, depending on the spatial
scale of the model.
The research is organized into two main parts as follows. In the first part, I
present an analysis of the effects of habitat destruction on metapopulation persistence.
Theoretical studies have already shown that a metapopulation goes extinct when the
fraction of suitable patches in the landscape falls below a critical threshold (the so
called extinction threshold). This result has become a paradigm in conservation
biology and several models have been developed to calculate extinction thresholds
for endangered species. These models, however, generally do not take into account
the spatial arrangement of habitat destruction, or the actual size of the landscape.
To investigate how the spatial structure of habitat destruction affects persistence,
I compare the behavior of two models: a spatially implicit patch-occupancy model
(which recreates the extinction patterns found in other models) and a spatially explicit
cellular automaton (CA) model. In the CA, I use fractal arrangements of suitable
and unsuitable patches to simulate habitat destruction and show that the extinction
threshold depends on the fractal dimension of the landscape. To investigate how
habitat destruction affects persistence in finite landscapes , I develop and analyze
a chain-binomial metapopulation (CBM) model. This model predicts the expected
extinction time of a metapopulation as a function of the number of patches in the
landscape and the number of those patches that are suitable for the population.
The CBM model shows that the expected time to extinction decreases greater than
exponentially as suitable patches are destroyed. I also describe a statistical method
for estimating parameters for the CBM model in order to evaluate metapopulation
viability in real landscapes.
In the second part, I develop and analyze a series of Markov chain models for
a rocky subtidal community in the Gulf of Maine. Data for the model comes from
ten permanent quadrats (located on Ammen Rock Pinnacle at 30 meters depth)
monitored over an 8-year period (1986-1994). I first parameterize a linear (homogenous)
Markov chain model from the data set and analyze it using an array of
novel techniques, including a compression algorithm to classify species into functional
groups, a set of measures from stochastic process theory to characterize successional
patterns, sensitivity analyses to predict how changes in various ecological processes
effect community composition, and a method for simulating species removal to identify
keystone species. I then explore the effects of time and space on successional
patterns using log-linear analysis, and show that transition probabilities vary significantly
across small spatial scales and over yearly time intervals. I examine the
implications of these findings for predicting equilibrium species abundances and for
characterizing the transient dynamics of the community. Finally, I develop a nonlinear
Markov chain for the rocky subtidal community. The model is parameterized
using maximum likelihood methods to estimate density-dependent transition probabilities.
I analyze the best fitting models to study the effects of nonlinear species
interactions on community dynamics, and to identify multiple stable states in the
subtidal system.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2000
Collections
Suggested Citation
Thesis: Hill, M. Forrest, "Spatial models of metapopulations and benthic communities in patchy environments", 2000-09, DOI:10.1575/1912/4124, https://hdl.handle.net/1912/4124Related items
Showing items related by title, author, creator and subject.
-
Mantle upwelling, melt generation, and magma transport beneath mid-ocean ridges
Magde, Laura S. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-03)The formation of new oceanic crust is the result of a complex geodynamic system in which mantle rises beneath spreading centers and undergoes decompression melting. The melt segregates from the matrix and is focused to ... -
Natural and synthetic estrogens in wastewater treatment plant effluent and the coastal ocean
Griffith, David R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-09)Steroidal estrogens are potent endocrine disrupting chemicals that are naturally excreted by vertebrates (e.g., humans and fish) and can enter natural waters through the discharge of treated and raw sewage. Because ... -
Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance
Whalen, Kristen E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2008-06)Understanding how organisms deal with potentially toxic or fitness-reducing allelochemicals is important for understanding patterns of predation and herbivory in the marine environment. The ability of marine consumers ...