Panmixia across elevation in thermally sensitive Andean dung beetles

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Janzen's seasonality hypothesis posits that limited environmental variability leads to reduced thermal tolerance breadth.
• Narrow thermal tolerance may restrict dispersal across environmental gradients, potentially causing isolation by environment.

Purpose of the Study:

• To investigate isolation by environment across elevational gradients in Andean dung beetles.
• To test if narrow thermal physiologies correlate with genetic structure in species with limited elevational ranges.

Main Methods:

• Analysis of genome-wide SNP data from five species of Andean dung beetles (Scarabaeinae).
• Assessment of population genetic structure in relation to elevational gradients and environmental variables.
• Evaluation of elevational range limits for genetic diversity patterns.

Main Results:

• No significant evidence of population genetic structure associated with elevation was found.
• Little signal of isolation by environment was detected across the studied species.
• Elevational ranges for most species appeared stable, with no decay in genetic diversity at range limits.

Conclusions:

• Physiological constraints on dispersal may be more influential outside of stable realized niches.
• The findings suggest a lower bound on the spatial scale of local adaptation in these species.
• Results challenge the direct link between narrow thermal tolerance and isolation by environment in high-gradient ecosystems.