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Why Is the Bark of Common Temperate Betula and Populus Species White?

S. Lev-Yadun

Published 2019 in INTERNATIONAL JOURNAL PLANT SCIENCES

ABSTRACT

Premise of research. The bark of several Betula and Populus species common in temperate/boreal North America and Eurasia is conspicuously white, and such bark coloration is uncommon in warmer ecologies and in parallel high latitudes in South America. Reflecting light to avoid cambial heating during winter and avoiding the consequent cambial scalding is the century-old, accepted adaptive explanation for this character, but it does not seem to fully explain the evolution of white bark. Methodology. I studied the ontogeny and geography of white bark and nonwhite bark in various ecologies of the temperate region. Pivotal results. I propose that both the limited distribution of strictly white bark in middle-high latitudes, but still within the winter-frozen temperate regions, and the fact that many thin branches in these white-barked taxa are not white clearly indicate that the defense against cambial heating during winter cannot be the exclusive or even the major explanation for this phenomenon. Conclusions. I propose five additional nonexclusive functional explanations for this character: (1) undermining herbivorous insect camouflage when the insects move on white bark; (2) camouflaging trees against extinct Tertiary and Pleistocene megafauna and current mammals that consume trunk and bark during snowy winters, possibly also by countershading; (3) being a visual aposematic signal when combined with chemical defense or low palatability; (4) reducing bark heating in spring, summer, and autumn in order to prevent herbivorous arthropods from warming, and thus reducing their activity, especially in the morning; and (5) helping predators spot insects’ movements because of the darker horizontal lenticels common in white bark.

PUBLICATION RECORD

  • Publication year

    2019

  • Venue

    INTERNATIONAL JOURNAL PLANT SCIENCES

  • Publication date

    2019-05-30

  • Fields of study

    Biology, Environmental Science

  • Identifiers
    DOI 10.1086/702760
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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