Determining the optimal movement strategies in environments with heterogeneously distributed resources and toxicants

Environmental stress forces populations to move away from oppressive regions and look for desirable environments. Different species can respond to the same spatial distributions of resource and toxicant with distinct movement strategies. However, the optimal behavioral strategy may differ when a resource and a stressor occur simultaneously or if they distribute in different patterns. We compared the total abundance of two strains of Caenorhabditis elegans with different locomotion speeds as they forage in various spatial distributions of resource and toxicant. Informed by the experimental observations, we proposed a new two-state population model, wherein nutrient up-take and reproduction are modeled separately, as driven by the spatial distribution of resource and toxicant. We found that fast movers had an advantage when either the toxicant coverage or the overlap between toxicant and resource is increased. Also, to assess the effectiveness of designing refuges to conserve species in s..., Strains. Two strains with random (e.g. with defects in directed) movement were used in this study—MIA471 tax-2(p694) I; egl-4(n478) IV and MIA472 tax-2(p694) I; pdfr-1(ok3425) III. MIA471 is a “roamer” strain that has a faster movement rate than MIA472, which is a “dweller” strain.
Heterogeneous Environments of Resources and Toxicants. We used square petri plates (100 mm x 100 mm) to design a variety of distributions of resources (E. coli) and toxicants (CuSO4·5H2O). 
Population Counting. Initially, three L4 worms were added at the center of each petri dish (between rows C and D, and columns 3 and 4). All the experimental plates were kept in a 20 °C incubator for approximately 120 hours, the amount of time it takes for the majority of the worms to reach a size easily counted under a microscope (above L3 stage) before the food is depleted. The abundance of C. elegans (stage L3 and above) within each of the twelve sections were counted and recorded (n = 280)., , # Determining the optimal movement strategies in environments with heterogeneously distributed resources and toxicants

[https://doi.org/10.5061/dryad.sxksn03d4](https://doi.org/10.5061/dryad.sxksn03d4)

## Description of the data and file structure

Population Counting. Initially, three L4 worms were added at the center of each petri dish (between rows C and D, and columns 3 and 4). All the experimental plates were kept in a 20 °C incubator for approximately 120 hours, the amount of time it takes for the majority of the worms to reach a size easily counted under a microscope (above L3 stage) before the food is depleted. After this time had passed, the experimental plates were moved into a refrigerator (4 °C) for about 30 minutes to let the low temperature slow the movements of the worms, making them easier to count. The abundance of *C. elegans* (stage L3 and above) within each of the twelve sections was counted and recorded (n = 280).

### Files and variables

#### File: FinalDatashee...