Effects Of Resource Limitation Research Articles

The effect of resource limitation on the temperature dependence of mosquito population fitness.

Laboratory-derived temperature dependencies of life-history traits are increasingly being used to make mechanistic predictions for how climatic warming will affect vector-borne disease dynamics, partially by affecting abundance dynamics of the vector population. These temperature-trait relationships are typically estimated from juvenile populations reared on optimal resource supply, even though natural populations of vectors are expected to experience variation in resource supply, including intermittent resource limitation. Using laboratory experiments on the mosquito Aedes aegypti, a principal arbovirus vector, combined with stage-structured population modelling, we show that low-resource supply in the juvenile life stages significantly depresses the vector's maximal population growth rate across the entire temperature range (22-32°C) and causes it to peak at a lower temperature than at high-resource supply. This effect is primarily driven by an increase in juvenile mortality and development time, combined with a decrease in adult size with temperature at low-resource supply. Our study suggests that most projections of temperature-dependent vector abundance and disease transmission are likely to be biased because they are based on traits measured under optimal resource supply. Our results provide compelling evidence for future studies to consider resource supply when predicting the effects of climate and habitat change on vector-borne disease transmission, disease vectors and other arthropods.

Detecting Resource Limitation in a Large Herbivore Population Is Enhanced With Measures of Nutritional Condition

Resource limitation at the population level is a function of forage quality and its abundance relative to its per capita availability, which in turn, determines nutritional condition of individuals. Effects of resource limitation on population dynamics in ungulates often occur through predictable and sequential changes in vital rates, which can enable assessments of how resource limitation influences population growth. We tested theoretical predictions of bottom-up (i.e., resource limitation) forcing on moose (Alces alces) through the lens of vital rates by quantifying the relative influence of intrinsic measures of nutritional condition and extrinsic measures of remotely sensed environmental data on demographic rates. We measured rates of pregnancy, parturition, juvenile, and adult survival for 82 adult females in a population where predators largely were absent. Life stage simulation analyses (LSAs) indicated that interannual fluctuations in adult survival contributed to most of the variability in λ. We then extended the LSA to estimate vital rates as a function of bottom-up covariates to evaluate their influence on λ. We detected weak signatures of effects from environmental covariates that were remotely sensed and spatially explicit to each seasonal range. Instead, nutritional condition strongly influenced rates of pregnancy, parturition, and overwinter survival of adults, clearly implicating resource limitation on λ. Our findings depart from the classic life-history paradigm of population dynamics in ungulates in that adult survival was highly variable and generated most of the variability in population growth rates. At the surface, lack of variation explained by environmental covariates may suggest weak evidence of resource limitation in the population, when nutritional condition actually underpinned most demographics. We suggest that variability in vital rates and effects of resource limitation may depend on context more than previously appreciated, and density dependence can obfuscate the relationships between remotely sensed data and demographic rates.

The effects of resource limitation and consensual incentives on cooperation

Exploring the evolution of cooperation has been one of the most challenging topics and attracted increasing attention in various realms. Hereby, we institute an analytic model where the relationship between the common benefits and contributions is the typical saturation nonlinearity. We investigate the evolutionary dynamics of cooperation with and without consensual incentives respectively. The population always evolves to full defection when the incentives are absent. Cooperation, however, can be promoted by consensual incentives when the degree of cooperators' preferences for incentives is great. There exists an intermediate amount of resources at which the positive effect of consensual incentives on cooperation is minimized. Furthermore, there is a U-shape relationship between the degree of cooperators' preference for an incentive and the evolution of cooperation. A greater basin of full cooperation can be induced when the cooperators' preference for reward is more pronounced than that for punishment.

Pollen limitation and resource limitation affect the reproductive success of Medicago sativa L.

BackgroundA large proportion of the flowers and ovules of plants do not develop into fruits and seeds. Plant reproduction may be limited because of pollen limitation and resource limitation. Medicago sativa L. is an ecologically important species in northwest China. We conducted a pollen supplementation experiment to determine the degree of pollen limitation in this species and detect the possible effects of resource allocation on pollen supplementation. We crossed two factors, pollen level (natural condition and hand pollinated) and resource level (control, water added, and fertilizer added), to estimate the effects of pollen addition and resource limitation on the opening of flowers and seed set. We also analyzed the floral characters, visitation frequency of pollinators and pollinator activity to estimate the effect of pollinators on the reproduction of M. sativa.ResultsOur results indicated that addition of pollen to some flowers did not divert resources from other flowers and that the addition of pollen boosted the seed set per flower, with no effect on flower number. The primary effect of resource limitation was on the number of flowers produced; however, there was no significant effect on seed set per flower. These findings showed that pollen limitation was an important limiting factor for seed set. In addition, Andrena lebedevi Popov was identified as the most effective pollinator, and pollinator visiting and activity affected reproduction success in M. sativa.ConclusionsWe found outcrossing was dominant in the breeding system and insect pollination played an important role in outcrossing. These findings have identified the dominant factor influencing seed set of M. sativa. This study aspires to contribute to a better understanding of pollen limitation, resource limitation and reproductive success.

The Effects of Resource Limitation on a Predator-Prey Model with Control Measures as Nonlinear Pulses

The dynamical behavior of a Holling II predator-prey model with control measures as nonlinear pulses is proposed and analyzed theoretically and numerically to understand how resource limitation affects pest population outbreaks. The threshold conditions for the stability of the pest-free periodic solution are given. Latin hypercube sampling/partial rank correlation coefficients are used to perform sensitivity analysis for the threshold concerning pest extinction to determine the significance of each parameter. Comparing this threshold value with that without resource limitation, our results indicate that it is essential to increase the pesticide’s efficacy against the pest and reduce its effectiveness against the natural enemy, while enhancing the efficiency of the natural enemies. Once the threshold value exceeds a critical level, both pest and its natural enemies populations can oscillate periodically. Further-more, when the pulse period and constant stocking number as a bifurcation parameter, the predator-prey model reveals complex dynamics. In addition, numerical results are presented to illustrate the feasibility of our main results.

Effects of resource limitation on habitat usage by the browser guild in Hluhluwe-iMfolozi Park, South Africa

Abstract:Resource depletion and associated increases in interspecific competition are likely to influence differential habitat usage amongst a guild. We tested some prominent theoretical concepts using observed differences in seasonal habitat use amongst the savanna browser guild (elephant, giraffe, impala, kudu and nyala) in Hluhluwe-iMfolozi Park, South Africa. Herbivore locations (n = 3108) were recorded over 2 y using repeated road transects and, for elephant, GPS collars (187 254 downloads). Densities were calculated using a novel GIS approach designed to be a cost-effective method for annual censuses, but also able to cope with abrupt changes in visibility. Selectivity for (Manly's α) vegetation types, and overlap (Schoener's index) in vegetation type usage were calculated. Resource depletion in the dry season resulted in all members of the guild increasing selectivity for vegetation types (sum of absolute values away from the neutral value for Manly's alpha for the guild: dry seasons 3.97, 5.16; corresponding wet seasons 3.12, 3.68), but decreasing interspecific overlap (80% of Schoener's indices lower in dry season versus wet season). These effects were more marked over the second, more severe, dry season. We found support for the niche overlap hypothesis and the niche compression hypothesis. The Jarman–Bell principle was generally supported, although unexpectedly during the severe dry season elephant showed the most selectivity for vegetation type. The greater the resource depletion, the more relevant interspecific differences in habitat usage become in relation to the differential impacts of guild members.

Provisioning habitat with custom‐designed nest‐boxes increases reproductive success in an endangered finch

AbstractManipulating resource availability to assess the strength and effects of resource limitation on an animal population is relatively straightforward, and thus, common in the scientific literature. Resource quality, however, is rarely manipulated, as this requiresa prioriknowledge of a relationship between some measurable variation in the resource and individual preference and/or fitness. Recent research on nest‐site selection was used to inform the design of custom‐built nest‐boxes for an endangered hollow‐nester, the Gouldian finch (Erythrura gouldiae). By provisioning breeding populations with these ‘high quality’ artificial nest sites over 3 years, we experimentally investigated the strength and effects of nest‐site limitation in this species. Breeding pairs using nest‐boxes initiated nesting earlier, produced larger clutches and fledged more offspring per season than those in natural hollows. Total and mean reproductive output also increased in nest‐box provisioned sites over the duration of the study. All of these effects were predominantly driven by pairs initiating clutches earlier, potentially because of the reduced intra‐ and interspecific competition for nest sites at optimal breeding times. Our findings suggest that reproduction in wild Gouldian finch populations may be limited by the availability of high quality nest sites in the landscape, and that nest‐boxes could be used as a tool for enhancing reproduction in recovering populations. Furthermore, we conclude that resource quality is equally, if not more important than quantity when supplementing resource‐limited habitats.

How the ladybird got its spots: effects of resource limitation on the honesty of aposematic signals

Summary1. Prey species often possess defences (e.g. toxins) coupled with warning signals (i.e. aposematism). There is growing evidence that the expression of aposematic signals often varies within species and correlates with the strength of chemical defences. This has led to the speculation that such signals may be ‘honest’, with signal reliability ensured by the costliness of producing or maintaining aposematic traits.2. We reared larval seven‐spot ladybirds (Coccinella septempunctata) on a Low or High aphid diet and measured the effects on warning signal expression (elytral carotenoid pigmentation, conspicuousness, spot size), levels of defensive alkaloids (precoccinelline, coccinelline), and relationships between these traits.3. High‐diet individuals had greater total precoccinelline levels, and elytra carotenoid concentrations at adulthood which was detectable to a typical avian predator. However, larval diet did not significantly affect adult body mass or size, spot size or coccinelline levels.4. Elytra carotenoid concentrations correlated positively with total precoccinelline levels in both diet groups and sexes. However, the relationship between elytra carotenoid concentrations and total levels of coccinelline depended on sex: in both diet groups, elytra carotenoids and coccinelline levels were positively correlated in females, but negatively correlated in males. Spot size and coccinelline levels correlated positively in Low‐diet individuals, but negatively in High‐diet individuals.5. These results point to physiological linkages between components of aposematism, which are modulated by resource (i.e. food) availability and affect the honesty of signals. Developmental diet, but also sex, influenced the relationships between signals and toxin levels. Ladybirds are sexually size dimorphic, and thus in comparison with males, females may be more susceptible to resource limitation and more likely to be honest signallers.

Mysid population responses to resource limitation differ from those predicted by cohort studies

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 432:115-123 (2011) - DOI: https://doi.org/10.3354/meps09158 Mysid population responses to resource limitation differ from those predicted by cohort studies Jason S. Grear*, Doranne Borsay Horowitz, Ruth Gutjahr-Gobell Atlantic Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Narragansett, Rhode Island 02882, USA *Email: grear.jason@epa.gov ABSTRACT: Effects of anthropogenic stressors on animal populations are often evaluated by assembling vital rate responses from isolated cohort studies into a single demographic model. However, these models are difficult to translate into ecological predictions because stressor effects observed in isolated cohorts may differ from those occurring in populations with overlapping generations. This problem is evident in many areas of stressor–response research, including the burgeoning work on ocean acidification. To address this problem, we compared vital rates in experimental cohorts and populations of the mysid Americamysis bahia at 4 levels of resource limitation. This required development of a novel observational scheme that allows inverse estimation of stage-specific vital rates in mixed-age populations without the use of cohort isolation or marking. Using digitally imaged time series observations of stage abundances, the most strongly supported inverse models indicated opposing (i.e. compensatory) effects of resource limitation on adult survival and juvenile maturation. The model with adult survival response only (i.e. no compensation) was also strongly supported. This contrasts with cohort results, where feeding effects on fecundity were strongest. These results suggest that emphasis in stressor–response studies on early life stages and cohorts of uniformly aged individuals may miss important demographic responses and should be augmented by observations of intact populations, especially as methods such as ours become more available. KEY WORDS: Inverse demography · Zooplankton · Population model · Cohort · Survival · ­Americamysis bahia Full text in pdf format PreviousNextCite this article as: Grear JS, Borsay Horowitz D, Gutjahr-Gobell R (2011) Mysid population responses to resource limitation differ from those predicted by cohort studies. Mar Ecol Prog Ser 432:115-123. https://doi.org/10.3354/meps09158 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 432. Online publication date: June 27, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Using vector analysis to understand temporal changes in understorey-tree competition in agroforestry systems

Techniques to determine the respective effects of resource limitation or over supply on tree productivity are important for developing effective forestry and agroforestry management strategies. There is a need for a simple integrative measure of the understorey effect on soil nutrient and moisture competition on tree productivity in agroforestry systems during the time period before trees dominate understorey vegetation. For the first time, the little used, but potentially valuable tool of vector analysis was evaluated over 5 years by investigating nutrient and water competition in a Pinus radiata silvopastoral experiment which had 5 pastures and a nil-understorey control. The study, from ages 2 to 6 years, was on fertile arable soils in a temperate, sub-humid climate. Establishing permanent crops on this arable site increased soil pH, C, N, organic-P and C:N ratio. Vector analysis, an analysis based on fascicle nutrient concentrations, dry weights and nutrient contents, predicted nutrient and moisture competition until the trees dominated the site after year 5. Foliar critical nutrient levels were helpful where one of the vectors was unable to distinguish between nutrient and moisture stresses. While moisture and N were found to be the main competitive factors, vector analysis also detected foliar nutrient accumulation, particularly for P and Mg. Lucerne and phalaris understoreys were the most competitive pastures, followed by cocksfoot and the two ryegrass treatments. Foliage vector analysis enabled the relative competitive effects of soil nutrients and moisture on tree productivity to be determined. Soil nutrient concentrations and soil moisture measurements and the effects of competition on tree growth were consistent with predictions from vector analysis.

Carbon source for reproduction in a spring ephemeral herb, Corydalis ambigua (Papaveraceae)

Summary 1. The carbon source for reproduction in plants may differ between flowering and fruiting stages. To clarify how spring ephemerals use current photosynthetic products for reproduction, the allocation patterns of photosynthate at flowering and fruiting and the effects of resource limitation on reproductive performance in Corydalis ambigua were assessed. 2. A 13C tracing experiment revealed that about 20% of the current photosynthetic carbon was used for reproduction at both flowering and fruiting. The proportion of 13C allocated to fruits was constant irrespective of the light level. In contrast, 13C translocation to tubers increased at fruiting, and this trend was accelerated when plants were shaded. 3. Defoliation treatment significantly reduced nectar production and tuber mass, while seed production was not affected. Therefore, when carbon assimilation was limited, carbon was preferentially allocated to current reproduction (seeds) rather than to pollinator attraction (nectar) or storage (tuber). 4. If seed production is partly supported by carbohydrate reserved in the old tissue of tubers, nectar and seed production may not compete strongly for carbon sources. In contrast to the ability of high seed production, the susceptibility of nectar production to current photosynthesis indicates that seed production of this species is basically limited by pollen capture. 5. Therefore, temporal separation of resource pool for reproduction may mitigate the joint limitation of seed production between pollinator attraction and resource availability. Temporal variation of the sink–source balance of storage organ is crucial to understand the cost of reproduction in perennial plants.

Automaticity, Attention, and Executive Control, and their relation to Mismatch Negativity

Event Abstract Back to Event Automaticity, Attention, and Executive Control, and their relation to Mismatch Negativity Leon Y. Deouell1* 1 Department of psychology,interdisciplinary center for neural computation,The Hebrew University, Israel The terms ‘pre-attentive’ and ‘automatic’ are ubiquitously associated with the mismatch negativity (MMN). Moreover, MMN is frequently used as a primary test measure for pre-attentive or automatic processing. However, there are apparently mixed results concerning the sensitivity of MMN to variation in the attentional load in the primary task. We measured the robustness of the MMN in a series of studies using especially the ‘attentional blink’ paradigm. In this task, two targets (T1 and T2) embedded in a rapid (11 Hz) sequence of distracters (rapid serial visual presentation) had to be reported. Load was manipulated by varying the contrast of the stimuli and manipulating their duration. We tested both the overall task effects and the trial-by-trial correlation between task performance and the MMN, both before T1 (to assess top-down attention to the task) and post-T1, during the ‘attentional blink’ period. The attentional blink is a reduction in T2 detection rate when it appears between ~100 to ~400 ms after T1. We find that while MMN remains robust despite highly demanding task loads, and in that sense it is automatic, it is not impenetrable: although the effects were small, the MMN amplitude significantly reflected momentary attentional fluctuations as manifested in the primary task performance. This requires some qualification of the term ‘automatic’. Moreover, we found that during a visual ‘attentional blink’, when the subjects missed T2, the MMN was augmented relative to trials when T2 was detected. This suggests the possible involvement of executive inhibitory control over MMN generation, which is reduced during the blink. Thus, whereas the generation of MMN seems to be the default response of the auditory system to deviations outside the scope of the present task, this response is susceptible to various effects of resource limitation and inhibition. Supported by the National Institute for Psychobiology in Israel Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009. Presentation Type: Oral Presentation Topic: Symposium 6: Attention and consciousness Citation: Deouell LY (2009). Automaticity, Attention, and Executive Control, and their relation to Mismatch Negativity. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.085 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Mar 2009; Published Online: 25 Mar 2009. * Correspondence: Leon Y Deouell, Department of psychology,interdisciplinary center for neural computation,The Hebrew University, Jerusalem, Israel, msleon@huji.ac.il Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Leon Y Deouell Google Leon Y Deouell Google Scholar Leon Y Deouell PubMed Leon Y Deouell Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Long-term effects of resource limitation on stream invertebrate drift

Long-term effects of resource limitation on stream invertebrate drift

Density-independent resource limitation and the transmission of an insect pathogen.

The effects of resource limitation on the transmission of a pathogen were explored. Resource limitation was achieved by replacing part of the host's diet with an indigestible bulking agent. Populations of the pyrallid moth, Plodia interpunctella, raised on high- and low-quality food regimes were exposed to a granulosis virus. Moths subjected to a lower food quality were more likely to become infected, despite the fact that in previous studies, individuals showed no increased susceptibility when exposed individually to the virus. This effect is suggested to be due to a higher exposure to the pathogen due to a faster feeding rate and longer developmental period. The implications of resource levels to the population dynamics of host-pathogen interactions are discussed.

Growth and Survival of Postmetamorphic Toads: Interactions among Larval History, Density, and Parasitism

I examined growth and survival of the European toad, Bufo bufo, from hatching to the approximate time of first hibernation. I varied tadpole density in experimental ponds such that individuals from low—density ponds emerged 48.5% larger than those from high—density ponds. In the laboratory, metamorphs from both pond densities were maintained in containers at densities of one or six. Nine weeks after metamorphosis they were exposed to 0 or 80 larvae of the lungworm, Rhabdias bufonis. A factorial experiment aimed to determine (1) the extent to which conditions experienced by larvae carried over to the terrestrial stage (2) the effects of resource limitation and past history on a host's response to a potential pathogen. The density of metamorphs had the strongest effect on growth and survival: 18 wk after metamorphosis, those raised alone were °80% heavier than those in groups and they had 31% higher survival. However, larval history also affected growth and survival and affected how metamorphs responded to density. First, single toads emerging from low—density ponds were 14.5% larger at the time of hibernation than those from high—density ponds. The mechanism for this growth advantage probably lies in the consistently higher growth rates of single toads from low—density ponds, especially during the first 3 wk after metamorphosis. Second, survival in group containers was higher for toads from low—density ponds, especially during the first few weeks after metamorphosis when most deaths involved toads from high—density ponds. These results support a carry—over effect between larval history and subsequent performance in an organism with a complex life cycle. Infection with lungworms had no detectable effect on metamorph growth or survival. This result contrasts earlier studies on this system, possibly due to the relatively low worm burdens or low statistical power. Yet, the results may also indicate that the predicted impact of infection on hosts, especially those limited by resources, is not as straightforward as theoretical studies suggest.

Resource limitation and the lethal and sublethal effects of a viral pathogen in the Indian meal moth, Plodia interpunctella

Abstract. The effects of resource limitation and the lethal and sublethal effects of a granulosis virus on a lepidopteran host, the Indian meal moth, Plodia interpunctella, were examined. The food quality was manipulated by the addition of an inert bulking agent (methyl cellulose) which caused the size, development rate and fecundity of the moths to be reduced. The resource quality had no effect on the mortality due to the virus. In contrast, sublethal effects of the virus on pupal weight were more apparent under conditions of resource limitation. Considerable variation between the sublethal effects after challenge with different doses of the virus was found. The balance between deleterious sublethal effects of the virus and the selection of more robust individuals by the bioassays is proposed as a mechanism to explain this variation. Implications for the dynamics of insect hosts and their pathogens are discussed.

Behavior and Phenology of a Specialist Bee (Dieunomia) and Sunflower (Helianthus) Pollen Availability

The phenological relationships between nesting behavior of a specialist, solitary bee, Dieunomia triangulifera, and the flowering of its primary pollen source, Helianthus annuus, were studied for 3 yr at a site in northeastern Kansas, which contained between 50 000 and >150 000 nests. Activity patterns of D. triangulifera are closely synchronized with pollen availability on nearby sunflower plants in three ways: (1) each year, D. triangulifera became active within days of the beginning of the local sunflower bloom, and the emergence schedule of the entire population at the nest site was timed such that all females had constructed nests and were collecting pollen at peak bloom; (2) over a season the greatest numbers of provisioning females were active at peak bloom, when pollen was most abundant; and (3) over the day, females made more trips, each of which took less time when pollen was most abundant on nearby flowers than when it was scarce. Between seasons, female reproductive success varied positively with the availability of H. annuus pollen. When pollen was abundant, and the population at the nest site was low, °3 times more cells were provisioned than the following year when the bee population was high and pollen abundance declined. Furthermore, 20 pollen—collecting bee species (10 specialists and 10 generalists), besides D. triangulifera, used an estimated 68% of the available sunflower pollen at this site. These data suggest that resource limitation is important in shaping patterns of provisioning behavior in D. triangulifera. Other behaviors presumably related to reproductive success were variable and suggest resources were not limiting: (1) all females did not forage on each day, even at peak bloom; (2) variance in both trip durations and the numbers of trips made per day was large; and (3) females produced far fewer eggs in their lifetime than apparently possible. We suggest that the apparently conflicting evidence for resource limitation may be explained by a physiological limit on the rate of egg production; in such a case, the effects of resource limitation, while clearly important, might not be the primary factor limiting reproductive output. Female D. triangulifera benefit by being synchronized with their resource. Daily and seasonal synchrony enable females to collect a greater amount of pollen during shorter foraging trips. The translates into higher mean reproductive success and, at the population level, allows more females to be supported by the pollen produced from nearby plants. In short, those females that are synchronized with the sunflower bloom effectively increase their own resource availability. This phenomenon may be general, especially in short—lived organisms, i.e ., the evolution of specialization may be associated with fitness benefits based on synchrony with a preferred food source.

A study of the interaction of virulence, resistance and resource limitation in a model of myxomatosis mediated by the European rabbit flea Spilopsyllus cuniculi (Dale)

In Great Britain, as opposed to Australia and much of the rest of Europe, the principal vector for myxomatosis has been the rabbit flea, Spilopsyllus cuniculi. A four-dimensional, quasi-epidemiological model of the disease is constructed which incorporates the role of this vector. The effect of resource limitation on rabbit fecundity is also modelled, and data of Mead-Briggs and Vaughan are used to model transmissibility properties of the disease. An essentially complete (local) analysis of the model is given, and conclusions drawn concerning the interaction of disease virulence, rabbit resistance and the resource capacity of the local environment in influencing properties of the disease. It is indicated how the model extends to a five-dimensional system when rabbit recovery is taken into account, and an analysis of attenuation of virulence due to Anderson and May is reworked in this context. Other factors involved in attenuation of virulence and increase in resistance are discussed.