Robert N. Coulson

AN ARTIFICIAL INTELLIGENCE MODELLING APPROACH TO SIMULATING ANIMAL/HABITAT INTERACTIONS

Ecological modellers have begun to recognize the potential of object-oriented programming techniques in structuring models. However, little has been done to take advantage of artificial intelligences (AI) symbolic representations to model the decision-making processes of animals. Here, a generic model of animal-habitat interaction and a specific model of moose-, Alces alces L., forest interactions in Finland are described that are event-driven and behavior-based. Individual level simulation is accomplished through an object-oriented knowledge representation scheme and AI techniques to implement a hierarchical decision-making model of behavior. The habitat is likewise represented in an object-oriented scheme, allowing the simulation of a heterogeneous environment. Other AI techniques for modelling behavior, memory, and actions are discussed including LISP methods, rule-based reasoning, and several search algorithms. Simulations of the moose-forest system show the power of this approach but are not intended to advance the theory of large-herbivore behavior and foraging. AI techniques are found to be most beneficial in (a) studying population processes based on individual level models of behavior, (b) modelling spatial heterogeneity, (c) building event-driven models, (d) providing a conceptual clarity to model construction, and (e) providing a structure equally well suited to simulating resource management.

Impacts of silvicultural practices on soil and litter arthropod diversity in a Texas pine plantation

Abstract In this study we used the diversity of soil and litter arthropods as a metric for evaluating the ecological effects of silvicultural practices of various intensities in a loblolly pine ( Pinus taeda L.) forest ecosystem. The treatments included low and high intensity harvesting, soil bedding, chemical herbicide application, and nitrogen and phosphorus fertilization. Soil and litter cores were used to sample arthropods after harvesting. In the first year following removal of trees, species diversity was higher in hand-fell, bole-only harvested plots than in mechanical, whole-tree harvested plots and higher in non-bedded plots than in bedded plots. However, these differences did not persist into the second year following harvesting. The recovery of undergrowth vegetation in the second year and the development of a rudimentary litter layer may have increased diversity in the more intensively treated plots. Arthropod species richness increased following nitrogen and phosphorus fertilization, but Shannon diversity did not. This indicates that the arthropod community had responded to fertilization with a shift in community composition. The rapid recovery of arthropod diversity in the second year following tree removal suggests that the silvicultural treatments used at this site did not put long-term productivity at risk. Comparisons with other similar studies suggest that when aiming for sustainable forest management, the particular silvicultural practices that allow for ecosystem recovery may depend on local and regional conditions.

Disturbance propagation by bark beetles as an episodic landscape phenomenon

Landscapes are the resultant of ecological processes and events operating on many different space-time scales. Large scale disturbance is recognized as a major influence on landscape patterns, but the impact of small scale events is often overlooked. We develop an hierarchical framework to relate lightning and bark beetle population dynamics to the southern pine forest landscape using the concepts of disturbance propagation and amplification. The low level lightning disturbance can be propagated to the landscape level when weather and forest stand structure facilitate bark beetle epidemics. We identify epidemics as biotically-driven episodes that alter landscape structure. The concept of the landscape as the spatial dimension of these episodes is represented in a conceptual model linking insect-host and landscape mosaic interactions.

Heterogeneity of forest landscapes and the distribution and abundance of the southern pine beetle.

A fundamental and unanswered research question in landscape ecology centers on how the spatial arrangement of ecosystems influences the distribution and abundance of organisms across complex landscape mosaics. In this study our goal was to examine how the southern pine beetle (SPB) perceives and responds to heterogeneity in forest landscape mosaics. The study was based on the use of extant knowledge of SPBs natural history and a spatially referenced database that included explicit information on landscape structure as well as distribution and abundance of the insect. Both the content and context of the spatial elements forming the forest landscape were considered, as human-caused fragmentation and natural disturbances create mosaic patterns where the specific arrangement of components can enhance or inhibit herbivory by the SPB. To examine how heterogeneity influences epidemiology of the SPB, we identified the elements of landscape structure that serve as targets for SPB. The principal targets include three types or arrangements of host trees: acceptable species, susceptible habitat patches, and lightning-struck hosts. Using a spatial database and a statistical approach we evaluated the number and arrangement of these targets in the context of existing population centers. The product was a functional heterogeneity map that portrayed how the spatial arrangement of landscape elements (habitat targets) influences the distribution and abundance of the SPB across complex mosaics of ecosystems.

The allocation process and between-tree survival probabilities inDendroctonus frontalis infestations

We have presented two transfer functions for allocating populations ofD. frontals adults in spots: a fixed probabilityTF and a time-temperature dependentTF. Both procedures produced essentially equivalent results when applied to actual population measurements taken from spots. The time-temperatureTF was more realistic than the constant probabilityTF, but introduced an added source of variation into the transfer. Temperature was demonstrated to have a significant effect on adult longevity. The time-temperature dependentTF provides a means of incorporating this important variable. TheF1 andF2 values obtained from this time-temperature dependentTF were also judged to be superior to the values obtained from the constant probabilityTF. Survival of reemerged and emerged beetles were shown to be cyclic and compensatory.

Temporal pattern of africanization in a feral honeybee population from Texas inferred from mitochondrial DNA

Abstract The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11‐year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11‐year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin.

Bark beetle olfaction—II. Antennal morphology of sixteen species of Scolytidae (Coleoptera)

Abstract A SEM study was carried out on the antennae of several species of the scolytid genera Dendroctonus, Ips, Pseudohylesinus, Scolytus and Trypodendron . Although some genera have the same number of antennal segments, the shape of the antennal club was distinct for each genus. For all species the majority of sensilla occurred on the club and consisted of sensilla basiconica, sensilla chaetica and sensilla trichodea. The sensilla were arranged in sensory fields or bands on the club. Speculation is presented on the possible function of some of the sensilla.

A biophysical model of southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), development☆

Abstract Predicting the population dynamics of the southern pine beetle, Dendroctonus frontalis Zimmermann, in forests of the U.S.A. requires predictive models of cohort development. The cryptic nature of the insect, however, prevents direct observations of its development, and undefined host requirements of early stage larvae prevent rearing it in the laboratory. Consequently, obtaining the information needed to formulate predictive models is difficult. This study describes experimental, analytical, and modeling techniques used to obtain information on beetle development times, the distribution of those times, and percent mortality over a full range of constant temperatures. Our data indicate that D. frontalis is highly sensitive to temperature. Cohort development occurs over extended intervals of time with the durations of development influenced by temperature in a nonlinear fashion. Information on development rates and the distributions of development times were used to formulate biophysical models of life stage development and development from eggs to adult emergence. Tests of the latter model here and elsewhere (Feldman et al., 1981a) showed good agreement with data from several field populations. These tests provided a basis for incorporating the model into a larger population dynamics model for this insect (Feldman et al., 1981b).

Simulating the reciprocal interaction of forest landscape structure and southern pine beetle herbivory using LANDIS

The reciprocal interaction of landscape structure and ecological processes is a cornerstone of modern landscape ecology. We use a simulation model to show how landscape structure and herbivory interact to influence outbreaks of southern pine beetle (Dendroctonus frontalis Zimmermann) in a landscape representative of the southern Appalachian Mountains, USA. We use LANDIS and its biological disturbance agent module to simulate the effects of landscape composition (proportion of landscape in host area) and host aggregation on the size and severity of insect outbreaks and the persistence of the host species, Table Mountain Pine (Pinus pungens Lamb.). We find that landscape composition is less important in the modeled landscapes than host aggregation in structuring the severity of insect outbreaks. Also, simulated southern pine beetle outbreaks over time tend to decrease the aggregation of host species on the landscape by fragmenting large patches into smaller ones, thereby reducing the severity of future outbreaks. Persistence of Table Mountain pine decreases throughout all simulations regardless of landscape structure. The results of this study indicate that when considering alternative restoration strategies for insect-affected landscapes, it is necessary to consider the patterns of hosts on the landscape as well as the landscape composition.

Spatial and Temporal Distribution and Nest Site Characteristics of Feral Honey Bee (Hymenoptera: Apidae) Colonies in a Coastal Prairie Landscape

Abstract We evaluated the distribution and abundance of feral honey bee, Apis mellifera L., colonies in a coastal prairie landscape by examining nest site characteristics, population trends, and spatial and temporal patterns in cavity use. The colony densities of up to 12.5 colonies per km2 were the highest reported in the literature for an area including both suitable and unsuitable patches of nesting habitat. The measured cavity attributes were similar to those reported from other areas. The time occupied and turnover indices provided useful information about cavity quality, although none of the measured cavity attributes were correlated with these indices. Unmeasurable cavity characteristics, such as cavity volume, may provide a better estimate of cavity quality. Spatial patterns existed in cavity use by the feral colonies, with the colonies showing an aggregated pattern of distribution throughout the study. Colony aggregations probably resulted from the distribution of resources, especially cavities. Two years after the arrival of Africanized honey bees, cavities used by Africanized and European colonies were aggregated in distribution. During what seemed to be a transition period, both Africanized and European colonies were randomly distributed. After that time, European colonies remained randomly distributed, whereas Africanized colonies were aggregated. Therefore, the invasion of Africanized honey bees seemed to fragment the existing European population, corresponding to a decrease in the overall number of European colonies in the study area.