Evaluating the targets of selection during character displacement

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Ecological character displacement (ECD) is driven by interspecific competition, leading to trait divergence.
• Typically, ECD is assumed to involve selection on a single, continuously varying trait.
• However, selection may target multiple traits, and these targets can differ between interacting species.

Purpose of the Study:

• To investigate the specific traits targeted by selection in Spadefoot toad (Spea multiplicata) during experimentally imposed competition with a congener (S. bombifrons).
• To understand the role of trait correlations and plasticity in the process of character displacement.

Main Methods:

• Experimental manipulation of interspecific competition between Spea multiplicata and Spea bombifrons.
• Analysis of selection acting on multiple resource-acquisition traits.
• Use of multiple regression to disentangle direct and indirect selection.
• Assessment of phenotypic plasticity in response to competition.

Main Results:

• Significant selection was detected on multiple resource-acquisition traits when examined individually.
• Controlling for trait correlations indicated that direct selection on one trait could indirectly affect others.
• Competition primarily imposed selection on morphology, with less impact on plasticity.
• Evidence suggests that selective targets may differ between the competing species.

Conclusions:

• Character displacement involves complex selection pressures acting on multiple, potentially correlated traits.
• Understanding the specific targets of selection is critical for predicting the evolutionary trajectory of competing species.
• The targets of selection may not be symmetrical between interacting species during character displacement.