The Selection Mosaic and Diversifying Coevolution between Crossbills and Lodgepole Pine

Area of Science:

• Ecology
• Evolutionary Biology
• Plant-Animal Interactions

Background:

• Seed predators exert selective pressures on plant evolution.
• Asymmetrical competition between species can alter these selective pressures.
• Lodgepole pine (Pinus contorta ssp. latifolia) interactions with seed predators are key to understanding coevolutionary dynamics.

Purpose of the Study:

• To investigate how asymmetrical competition between seed predators influences the evolutionary trajectory of lodgepole pine cones.
• To determine the roles of red squirrels (Tamiasciurus hudsonicus) and red crossbills (Loxia curvirostra) in driving pine evolution.
• To explore the consequences of these interactions for biodiversity and speciation.

Main Methods:

• Comparative analysis of pine populations with varying predator abundances.
• Ecological modeling of competitive interactions and selective pressures.
• Phylogenetic analysis to infer coevolutionary histories.

Main Results:

• Red squirrels (Tamiasciurus hudsonicus) are dominant competitors, driving pine cone evolution in their presence.
• When squirrels are absent, red crossbills (Loxia curvirostra) become significant selective agents, leading to an evolutionary arms race.
• These interactions create a selection mosaic with coevolutionary hot spots, where divergent selection can promote speciation in crossbills.

Conclusions:

• Asymmetrical competition is a critical factor structuring plant-animal coevolutionary dynamics.
• Divergent selection, while driving adaptation and speciation, can also erode the geographic mosaic of coevolution.
• Understanding these complex interactions is vital for predicting evolutionary trajectories and biodiversity patterns.