The study of ecological niche evolution is fundamental for understanding how the environment influences species’ geographical distributions and their adaptation to divergent environments. Here we present a study of the ecological niche, demographic history and thermal performance (locomotor activity, developmental time and fertility/viability) of the temperate species Drosophila americana and its two chromosomal forms. Temperature is the environmental factor that contributes most to the species’ and chromosomal forms’ ecological niches, although precipitation is also important in the model of the southern populations. The past distribution model of the species predicts a drastic reduction in the suitable area for the distribution of the species during the Last Glacial Maximum (LGM), suggesting a strong bottleneck. However, DNA analyses did not detect a bottleneck signature during the LGM. These contrasting results could indicate that D. americana niche preference evolves with environmental change and, thus, there is no evidence to support niche conservatism in this species. Thermal performance experiments show no difference in the locomotor activity across a temperature range of 15 to 38oC between flies from the north and the south of its distribution. However, we found significant differences in developmental time and fertility/viability between the two chromosomal forms at the model’s optimal temperatures for the two forms. However, results do not indicate that they perform better for the traits studied here in their respective optimal niche temperatures. This suggests that behaviour plays an important role in thermoregulation, supporting the capacity of this species to adapt to different climatic conditions across its latitudinal distribution.

sequence alignmentsNexus alignments of the 16 genes used in the studysequences.zipchrom2-3 final runThis folder contains the xml file used as input in BEAST analysis plus the trees and csv files from the runsLogCombined run filesThis folder contains the xml, trees, csv and log files resulting from combining the two independent BEAST runs with LogCombinerLogCombined_final_runs.zipchrom2-3 final run 2This folder contains the xml file used as input in the second BEAST run plus the trees and csv output filesD_americana average ENMThis folder contains the results from Maxent analysis for the whole species; average from 10 replicatesD_americana average cold ENMThis folder contains mxd, csv and plots resulting from te maxent analysis using cold-related variablesD_a_americana cold ENMMaxent results for the D. a. americana chromosomal form using the cold-related variablesD_a_americana ENMMaxent modelling results for the D. a. americana chromosomal form.D_a_texana cold ENMMaxent modelling results for the D. a. texana chromosomal form using cold-realted variables.D_a_texana ENMMaxent results for D. a. texana chromosomal form.