Osmoregulatory ability predicts geographical range size in marine amniotes

Area of Science:

• Comparative physiology
• Ecology
• Evolutionary biology

Background:

• Species with wider geographical ranges often face diverse environmental conditions.
• A correlation is expected between range size and physiological tolerance to abiotic factors.
• Marine invasion by amniotes (mammals, birds, reptiles) offers a model to study this correlation due to salt excretion adaptations.

Purpose of the Study:

• To test the correlation between geographical range size and physiological tolerances in marine amniotes.
• To investigate if physiological capacity influences species' distribution and environmental adaptability.

Main Methods:

• Analysis of data from 62 species (19 mammals, 18 birds, 24 reptiles).
• Examined the relationship between range size, encountered salinity levels, and osmoregulatory ability (sodium excretion).
• Statistical models incorporated metabolic mode, body size, and diet as explanatory variables.

Main Results:

• Species with wider distributions encounter a broader range of salinities.
• Widely distributed marine amniotes exhibit superior osmoregulatory ability, indicated by lower sodium concentrations in excretory fluids.
• The correlation remained significant after accounting for other ecological factors.

Conclusions:

• Physiological tolerance, specifically osmoregulation, is linked to geographical range size in marine amniotes.
• These findings suggest physiological data can predict species' potential distribution and susceptibility to environmental changes.
• Understanding physiological limits is crucial for assessing species' vulnerability to anthropogenic disturbances.