Integrating evolution into ecological modelling: accommodating phenotypic changes in agent based models.

PMCID: PMC3733718This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Evolutionary change is a characteristic of living organisms and forms one of the ways in which species adapt to changed conditions. However, most ecological models do not incorporate this ubiquitous phenomenon. We have developed a model that takes a 'phenotypic gambit' approach and focuses on changes in the frequency of phenotypes (which differ in timing of breeding and fecundity) within a population, using, as an example, seasonal breeding. Fitness per phenotype calculated as the individual's contribution to population growth on an annual basis coincide with the population dynamics per phenotype. Simplified model variants were explored to examine whether the complexity included in the model is justified. Outputs from the spatially implicit model underestimated the number of individuals across all phenotypes. When no phenotype transitions are included (i.e. offspring always inherit their parent's phenotype) numbers of all individuals are always underestimated. We conclude that by using a phenotypic gambit approach evolutionary dynamics can be incorporated into individual based models, and that all that is required is an understanding of the probability of offspring inheriting the parental phenotype

Coupling models of cattle and farms with models of badgers for predicting the dynamics of bovine tuberculosis (TB)

Bovine TB is a major problem for the agricultural industry in several countries. TB can be contracted and spread by species other than cattle and this can cause a problem for disease control. In the UK and Ireland, badgers are a recognised reservoir of infection and there has been substantial discussion about potential control strategies. We present a coupling of individual based models of bovine TB in badgers and cattle, which aims to capture the key details of the natural history of the disease and of both species at approximately county scale. The model is spatially explicit it follows a very large number of cattle and badgers on a different grid size for each species and includes also winter housing. We show that the model can replicate the reported dynamics of both cattle and badger populations as well as the increasing prevalence of the disease in cattle. Parameter space used as input in simulations was swept out using Latin hypercube sampling and sensitivity analysis to model outputs was conducted using mixed effect models. By exploring a large and computationally intensive parameter space we show that of the available control strategies it is the frequency of TB testing and whether or not winter housing is practised that have the most significant effects on the number of infected cattle, with the effect of winter housing becoming stronger as farm size increases. Whether badgers were culled or not explained about 5%, while the accuracy of the test employed to detect infected cattle explained less than 3% of the variance in the number of infected cattle

Ecological Community’s “Trophic Level Extreme” from Vulnerability Link Distributions & Energetic Pathways

Complexity of complete ancient and modern food webs assumed to capture essential forests network trophic topology scales similarly to that of ancient and modern lake webs and communities from variable environments. Reasona- bly these groupings and patterns are not exclusively driven by environmental fluctuating conditions. Unexpectedly, dispar- ate aquatic and terrestrial communities can belong to the same connectional trend with network size whose nodes represent the number of trophic species. Although some aquatic communities can host apex predators at higher Trophic Levels than terrestrial ones, it is not clear if this relates to different connectance or hierarchical structure. OBJECTIVES In this study we analyzed, reviewing literature trophic webs, Extreme number of Trophic Levels data and their relationship with trophic link distributions (vulnerability and surrogate energetic parameters). Furthermore, we report about a gap on the number of energetic pathways at a threshold modal Trophic Level. General differences, among aquatic and terrestrial communities, in primary consumers fractions or percentages were tested. METHODS A new network approach to food webs was presented to interpret maximum chain length or extreme Trophic Levels from matrix information and few assumptions. Two opposite logarithmic trends were analyzed, and sigmoid models were utilized to predict missing predatory links in large cumulative food networks. RESULTS The main results are the presentation of two opposite trends of link density vs topological connectance in log log correlation analysis where communities belonging to different eco regions of the richest lake in terms of trophic species ( i.e., Lake Malawy Nya sa Niassa) were submitted to further scrutiny for the interpretation of their maximum chain length. Herbivore’s Fraction 1 equal the number of Trophic Levels in newly defined size ambivalent communities that are characterized by relatively small number of species but displaying the same complexity pattern of species rich ones. CONCLUSION Maximum number of Trophic Levels of ecological communities from different habitats could be associated with extrapolated link density obtained by the trends of vulnerability link and surrogate energetic link distributions. Top down and bottom up control w ere discussed under this new perspective where ubiquitous anti predatory strategies, inferred by reduction in trophic links, were also estimated. This wide new perspective could be preparatory for the interpretation of the effects of changing scenarios or contexts and habitat/species safeguar

Urinary excretion of endothelin-1 in children with absorptive idiopathic hypercalciuria

Urinary excretion of endothelin-1 (ET-1) and plasma ET-1 were measured in 21 children with absorptive idiopathic hypercalciuria (AIH) and 22 controls. The absorptive type of idiopathic hypercalciuria was determined by a calcium loading test. Daily urinary excretion of ET-1 and urinary ET-1/creatinine ratio were significantly increased (P=0.005 and P=0.007, respectively) in patients with AIH (9,274+/-6,444 pg/24 h and 14.04+/-9.52 pg/mg, respectively) compared with controls (4,699+/-2,120 pg/24 h and 7.36+/-4.71 pg/mg, respectively). Plasma ET-1 levels were significantly lower in patients with AIH (0.84+/-0.64 pg/ml) than in controls (1.54+/-0.54 pg/ml, P=0.0001). In conclusion, patients with AIH had increased urinary ET-1 excretion and decreased plasma ET-1 levels. This is most likely due to the decreased reabsorption of ET-1 in the renal tubule and increased renal production

Calcium and vitamin D metabolism in hypocalcemic vitamin D-resistant rickets carriers

Background/Aims: Hypocalcemic vitamin D-resistant rickets (HVDRR) is a rare monogenic autosomal recessive disorder associated with mutations in the gene of the vitamin D receptor (VDR), the mediator of 1,25(OH)(2)D-3 action. Although many investigations have discussed the clinical manifestations and molecular etiology of this disease, only a few have investigated the biochemical and hormonal status of heterozygous HVDRR. The aim of the current work was to investigate the profile of selected biochemical and hormonal parameters related to the vitamin D endocrine system in a large number of HVDRR heterozygotes. Methods: 67 relatives of 2 HVDRR patients, all members of an extended Greek kindred of five generations with a common ancestor, were included in the study. Direct sequencing was used to identify VDR gene mutations. Serum Ca, P, 25(OH)D, iPTH, and 1,25(OH)(2)D levels were determined in all members of the kindred. Results: DNA analysis of the participants led to the design of two study groups: the HVDRR carriers (24) and the control subjects (43). Our results showed elevated circulating serum levels of 1,25(OH)(2)D-3 and lower levels of PTH than their age- and sex-matched controls. No hypocalcemia or hypophosphatemia were detected in HVDRR carriers. Conclusions: Our findings suggest that HVDRR carriers may have compensatory elevated serum levels of 1,25(OH)(2)D-3 through which they restrain PTH secretion. The study of HVDRR carriers could be a useful tool for the investigation of the vitamin D endocrine system. Copyright (c) 2006 S. Karger AG, Basel

Modeling future range expansion and management strategies for an invasive squirrel species

Successful management of an invasive species requires in depth knowledge of the invader, the invaded ecosystem, and their interactions. The complexity of the species-system interactions can be reduced and represented in ecological models for better comprehension. In this study, a spatially explicit population model was created using the RAMAS software package to simulate the past and future invasion dynamics of the eastern grey squirrel (Sciurus carolinensis) in the fragmented habitat in case study areas in Ireland. This invasive squirrel species causes economic damage by bark stripping forest crops and is associated with the decline of its native congener (S. vulgaris). Three combinations of demographic and dispersal parameters, which best matched the distribution of the species shortly after introduction, were used to simulate invasion dynamics. Future population expansion was modeled under scenarios of no control and two different management strategies: fatal culls and immunocontraceptive vaccination programmes. In the absence of control, the grey squirrel range is predicted to expand to the south and southwest of Ireland endangering internationally important habitats, vulnerable forest crops, and the native red squirrel. The model revealed that region-wide intensive and coordinated culls would have the greatest impact on grey squirrel populations. Control strategies consisting solely of immunocontraceptive vaccines, often preferred by public interest groups, are predicted to be less effective. Complete eradication of the grey squirrel from Ireland is not economically feasible and strategic evidence-based management is required to limit further range expansion. Ecological models can be used to choose between informed management strategies based on predicted outcomes.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]