Principal components of the abiotic environment.

<p>Means (+/− s.e.) for the first two principal components describing variation in the eight environmental variables used to build ecological niche models. Different letters indicate significantly different means; each group (<i>S. multiplicata</i> in allopatry, <i>S. bombifrons</i> in allopatry, and sympatry), is significantly different from the other two.</p

Loadings on the first two principal components for the eight environmental variables used in the Maxent model.

<p>Loadings near 0 (i.e., −0.1 to 0.1) are denoted with an “*”.</p

Range maps of predicted sympatry.

<p>Range maps of predicted sympatry between <i>Spea multiplicata</i> and <i>S. bombifrons</i>. The value for each 1 km sq pixel was calculated by multiplying the logistic value of both species, and values range from 0 (white) to 1 (dark green). Sites used in the environmental analysis are indicated by points. Specifically, blue squares represented collection locations for <i>S. bombifrons</i> that occurred in areas predicted to be allopatric for that species; orange circles represent collection locations for <i>S. multiplicata</i> records that were predicted to be allopatric for that species, whereas gray triangles represent collection locations for either species in areas predicted to be sympatric.</p

Range maps for <i>Spea multiplicata</i>

<p><b>and </b><b><i>S. bombifrons</i></b><b>.</b> Range map showing the total range of both <i>S. multiplicata</i> and <i>S. bombifrons</i>.</p

Maxent response curves for the Biotic Model.

<p>The response curves of the Biotic Model for (a) <i>S. bombifrons</i> and (b) <i>S. multiplicata</i>. These curves show how the logistic output changes along an ‘environmental gradient’. Here, the environmental gradient is the predicted output of the other species used to create the Biotic Model. The red line shows the average of the 10 replicate runs, while the blue bands shows +/− one standard deviation. At low logistic values for one species, the other species has a low logistic value as well. Both species thus show a similar response to the environment (i.e. environments good for one species tend to be good for the other).</p

Alternative hypotheses for abiotic conditions underlying species distributions.

<p>A representation of three alternative patterns of environmental variation underlying sympatric and allopatric populations of two species across an environmental gradient. (a) Under hypothesis 1, species co-occur at intermediate environmental conditions where niches of the two species overlap. (b) Under hypothesis 2, biotic factors mediate co-occurrence such that species co-occur most commonly under extreme conditions. (c) Under hypothesis 3, sympatry and allopatry are governed primarily by dispersal ability, resulting in no environmental differences between sympatric and allopatric populations.</p

Environmental variation between sympatry and allopatry.

<p>Box-and-whisker plots showing environmental space occupied by predicted allopatric populations of <i>S. bombifrons</i> (abbreviated “<i>Sb</i> allopatry”), predicted allopatric populations of <i>S. multiplicata</i> (abbreviated “<i>Sm</i> allopatry”), and predicted sympatric populations of both species for each environmental variable used in the Maxent models. Non-overlapping notches are roughly equivalent to 95% confidence intervals, and therefore provide strong evidence that the medians differ <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032748#pone.0032748-R1" target="_blank">[48]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032748#pone.0032748-Chambers1" target="_blank">[58]</a>. An “*” above the sympatry box indicates variables for which sympatric sites are significantly hotter or drier than both allopatric sites.</p

Appendix B. Calculating likelihoods, number of parameters, and marginal costs for butterfly dispersal models.

Calculating likelihoods, number of parameters, and marginal costs for butterfly dispersal models

Appendix A. Comparison of movement behaviors among butterfly species.

Comparison of movement behaviors among butterfly species