Crown shyness

[6][7] There exist many hypotheses as to why crown shyness is an adaptive behavior, and research suggests that it might inhibit spread of leaf-eating insect larvae.

[9] The variety of hypotheses and experimental results might suggest that there are multiple mechanisms across different species, an example of convergent evolution.

[citation needed] Some hypotheses contend that the interdigitation of canopy branches leads to "reciprocal pruning" of adjacent trees: trees in windy areas suffer physical damage as they collide with each other during winds; the abrasions and collisions induce a crown shyness response.

Studies suggest that lateral branch growth is largely uninfluenced by neighbours until disturbed by mechanical abrasion.

Jacobs, who studied the crown shyness patterns in eucalyptus in 1955, believed that the trees' growing tips were sensitive to abrasion, resulting in canopy gaps.

[13] Miguel Franco (1986) observed that the branches of Picea sitchensis (Sitka spruce) and Larix kaempferi (Japanese larch) suffered physical damage due to abrasion, which killed the leading shoots.