Demographic compensation does not rescue populations at a trailing range edge.

Area of Science:

• Ecology
• Climate Change Biology
• Population Dynamics

Background:

• Rapid climate change is causing mismatches between species' geographic ranges and climatic niches.
• Population performance is expected to decline from leading (north) to trailing (south) range edges if ranges and niches are out of equilibrium.
• Demographic compensation, where vital rate changes offset each other, could potentially buffer range contractions.

Purpose of the Study:

• To investigate whether range limits and contractions are caused by inadequate demographic compensation.
• To assess population dynamics and demographic compensation across the geographic range of the scarlet monkeyflower (Erythranthe cardinalis).

Main Methods:

• Collected demographic data from 32 populations of Erythranthe cardinalis across 11° of latitude.
• Utilized integral projection models to evaluate population dynamics.
• Assessed demographic compensation across the species' latitudinal range.

Main Results:

• Population growth rates decreased from north to south, consistent with leading-trailing range dynamics.
• Southern populations at the trailing edge exhibited declines in survival, growth, and recruitment.
• Despite compensatory increases in reproduction and faster life-history traits, southern populations declined.

Conclusions:

• Inadequate demographic compensation may delay, but not prevent, population collapse at trailing range edges under climate change.
• The findings suggest limited resilience for Erythranthe cardinalis without returning favorable conditions or other buffering mechanisms like evolutionary rescue.