Computer code for a model describing the emergence of a long transient regular spatial pattern from interaction of competing aquatic macrophytes and a biocontrol agent
Data files
Nov 13, 2024 version files 42.66 KB
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CAmodeltest_Switch_Biocontrol_15September2024.m
20.28 KB
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README.md
2.08 KB
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Xu_and_DeAngelis_Tables_of_Input_Data_31October2024.docx
20.31 KB
Abstract
A spatially explicit simulation model was developed for competition between floating (FAV) and submersed (SAV) aquatic vegetation in which an insect biocontrol agent (weevil) consumes FAV biomass. In all simulations, a dynamic regular striped pattern of rock-scissors-paper (weevil-FAV-SAV) eventually forms and persists for thousands of days despite stochastic disturbances in the form of added adult weevils. At some point in the simulation, depending on the random number initiator, an apparently insignificant spatial deviation in small set of pixels triggers an instability that grows rapidly until the striped pattern has been replaced by a chaotic-appearing pattern. Investigation shows that the time lags involved in the weevil life cycle and assumptions on spatial movement lead to the instability and end of long transient. This research reveals the detailed mechanisms by which a long transient striped pattern transitions to an irregular pattern, offering insights into how spatial pattern form and change.
https://doi.org/10.5061/dryad.ht76hdrrp
Description of the data and file structure
There are two tables of parameter values that were used as input for the simulation model code “CAmodeltest_Switch_Biocontrol_15September2024”.
Files and variables
No data files or variables were uploaded.
Code/software
The Matlab code consists of the script “CAmodeltest_Switch_Biocontrol_15September2024”.
The script CAmodeltest_diffuseN_07April2023_Biocontrol simulates the interaction of two competing aquatic macrophytes, on a 50 x 50 spatial lattice of patches. The variables are
‘WH(i,j)’ = floating aquatic vegetation (FAV) biomass, water hyacinth
‘S(i,j)’ = submersed aquatic vegetation (FAV) biomass
An insect biocontrol agent feeds on the FAV. The variables for the adult are
‘Adult(i,j)’ = adult biocontrol insect numbers.
A fourth variable is the limiting nutrient concentration
‘nwh(i,j)’ = nutrient concentration.
The interaction of WH and S is described by equations. All three biotic variables can move in space and the nutrient nwh diffuses.
The script code calls the function UpdateEachPatch_15September2024). The function describes the life cycle of sub-adults of the biocontrol insect. It consists, for each of the 50 x 50 = 2500 patches, the variables
“Eggs(k)” = eggs, in day-age classes k =1,12
“L1(k)” = first stage larvae in day-age classes k = 1:29
“L2(k)” = second stage larvae in age classes k = 1:14
“Pupae(k)” = pupae in day-age classes k = 1:20
The function describes the feeding interaction of L2 larvae on the WH. The functional also describes density-dependence limitation of L1 larvae as a function of the ration of density of larvae to FAV biomass.
The simulation can be run over X number of days and the spatial pattern of vegetation and insect life cycles are displayed for any selected days and the total numbers over space of each variable are plotted through time.
No raw data were generated by this research. All of the data used in the model simulations as parameter values are from published papers. McCann (2016) parameterized the model of competition between SAV and FAV based on the submersed plant Nuttall’s waterweed (Elodea nuttallii) and the floating duckweed Lemna gibba. We used the parameters of those species, and used the parameters of N. eichhorniae, as the biocontrol agent, from van Schalkwyk (2016) although that is only hypothetical for the present situation, as we do not know parameters for a relevant herbivore of L. gibba. All these parameters are shown in Tables that have been uploaded. The parameter values are also in Xu and DeAngelis (2024). Hyperlinks for these papers have been uploaded.