ion tests for heterogeneity of total diversity (observed plus
unobserved) across multiple sites. It can account or test for fixed effects
that may explain diversity. It returns the significance of the covariates in
explaining diversity and a hypothesis test for heterogeneity.</p>
    </div>

    <pre class="usage"><span class='fu'>betta</span><span class='op'>(</span>
  chats <span class='op'>=</span> <span class='cn'>NULL</span>,
  <span class='va'>ses</span>,
  X <span class='op'>=</span> <span class='cn'