Scaling of extinction time with habitat size across six orders of magnitude in experimental populations

Theoretical models suggest that the mean time to extinction scales with habitat size through either exponential or power-law relationships, depending on demographic and environmental stochasticity. Despite extensive theoretical work, empirical validation of these scaling relationships is limited. Here, we report a microcosm study of Daphnia magna populations in experimental chambers consisting of 1, 2, 4, 8, 16, or 32 patches, with a total of 35 populations monitored daily until extinction. We tested the scaling of extinction time with patch count using nonlinear regression models for both exponential and power-law functions, comparing model fit with AIC. Although the study’s statistical power is constrained by sample size, this level of replication remains unmatched by previous work. Our experiment provides the first empirical test of long-standing theoretical predictions and lays a foundation for future studies to expand the understanding of extinction dynamics in ecological syst..., Stock monoclonal populations of Daphnia magna were cultured on green algae (Ankistrodesmus falcatus) in sufficient amounts for the experiment.
Microcosms were constructed from cast acrylic sheet using a CNC (computer numerical control) router, which tests showed to be nontoxic to Daphnia magna. Each microcosm consisted of a linear network of cylindrical patches, each large enough to support multiple adult Daphnia magna, connected by uniform channels of sufficient width (3 mm) and depth to admit a single adult. Dead-end channels were added to the ends of each linear microcosm to hold the total volume of each patch (including connecting channels) constant.
The primary experiment consisted of a single treatment (number of patches) with six levels (1, 2, 4, 8, 16, and 32 patches), replicated four times per level for a total of (N = 24) metapopulations. In addition, because smaller metapopulations were expected to go extinct quickly and because the labor involved in censusing the smalle..., , # Scaling of extinction time with habitat size across six orders of magnitude in experimental populations

[https://doi.org/10.5061/dryad.gmsbcc2zj](https://doi.org/10.5061/dryad.gmsbcc2zj)

## Description of the data and file structure

## Data

Raw data are in the R data file 'DaphniaCounts.rds'.

Column headings are defined as follows:

* date: the date of observation
* rep: replicate number, an identifier for randomization and experimental design
* count: which census number the record is associated with (either \"1\" for first census or \"2\" for second census)
* network.length: the number of chambers in the network
* node: the specific chamber in the network associated with the observation (nodes are ordered, e.g. node 2 is connected both to node 1 and 3)
* population: count of the number of individuals in the node
* collector: the identity of the researcher making the observation

## Analysis

R code for the analysis is in the pdf file 'analysis.pdf'. An executable script is in the R...,