Table 1 A combination of landscape fragmentation and elevation best explain the distribution of wingless queens along ecological gradients. Based on previous studies, we generated 12 models (M01 to M12) representing alternative hypotheses to explain the variation in frequency of wingless queens along the ecological gradient of each Sky Islands. The 12 models were ranked using the method of [121] implemented in R (Additional file 1: Table S2) and model probabilities (Prob) are reported, with m06 scoring as the highest ranking model

Flightlessness in insects has been reported to increase with altitude [47, 127].

Elevation influences a wide range of ecological factors and may account for their joint effects.

Atmospheric pressure is lower at higher altitude and efficient flight may require costly adaptations [128].

Insects will experience a decrease in annual thermal budget for growth and development. Critical temperature thresholds for growth, development and activity will be exceeded less frequently [128].

Temperature seasonality, the variability in temperature over the year, is indicative a less stable environment. Flightless insects are known to be found in higher frequencies in more stable habitats [47].

Flying insects will have a tendency to be blown away from patchy habitats, thus only wingless forms remain [46, 47]. The probability of finding a suitable habitat is decreased when habitats are patchy, thus dispersal risk is increased [129].

The need for dispersal in high productivity habitats is reduced because the conditions for survival are met and the relative risk of long distance dispersal becomes too high [130]

Both fragmentation and elevation influence the distribution of wingless queens.

The effect of fragmentation depends on elevation: fragmentation may only be affecting the distribution of wingless queens at certain altitudes.

Both fragmentation and temperature may influence the distribution of wingless queens.

The effect of fragmentation depends on temperature: fragmentation may only be affecting the distribution of wingless queens at certaine temperature. Habitat fragmentation and temperature are know to be potentially interrelated [131].

Both fragmentation and productivity can influence the distribution of wingless queens.

Habitat fragmentation can affect productivity. Fragmentation may affect wingless queen distribution in habitats with a certain productivity level only. Habitat fragmentation and biomass growth are know to be potentially interrelated [131].

Structure-rich model, including the effects of elevation, temperature, productivity, fragmentation and seasonality. Interactions were omitted.