Can internal range structure predict range shifts?

Area of Science:

• Ecology
• Climate Change Biology
• Conservation Biology

Background:

• Species are shifting their geographic ranges in response to climate change, but predicting these shifts remains challenging.
• Functional traits have limited ability to predict range shifts, necessitating exploration of other range characteristics.

Purpose of the Study:

• To test the hypothesis that range edge hardness, defined by relative abundance at range edges, can predict population trends at range limits.
• To investigate the inertia and limitation hypotheses regarding range edge hardness and range shifts.

Main Methods:

• Utilized a long-term avian monitoring dataset from northern Minnesota, USA.
• Estimated population trends for 35 trailing-edge and 18 leading-edge species.
• Modeled population trends as a function of range edge hardness derived from eBird data.

Main Results:

• Found limited evidence for associations between range edge hardness and population trends at range limits.
• Trailing-edge species with harder edges showed a slight tendency towards decline (weak support for limitation hypothesis).
• Leading-edge species with harder edges showed a slight tendency towards increase (weak support for inertia hypothesis).

Conclusions:

• Opposing results for leading and trailing edges suggest distinct mechanisms govern range expansions and contractions.
• Range edge hardness shows weak predictive power for population trends, indicating complexity in range shift dynamics.
• Future advancements in data and modeling may improve predictions of range shifts using within-range abundance patterns.