es. The default optimization method (<code>Nelder-Mead</code>) does not allow for lower or upper bounds in model parameters, so these arguments are commented out. In ecological terms, this optimization process allow for estimating the strength of both competitive and facilitative interactions, yet bounded optimization algorithms can be used to restrict the analysis to either competition or facilitation (i.e. positive or negative alpha values). We can also specify whether we want to compute standard errors 