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Related Experiment Videos

Diversifying coevolution between crossbills and black spruce on Newfoundland.

Thomas L Parchman1, Craig W Benkman

  • 1Department of Biology, New Mexico State University, Las Cruces 88003-8001, USA.

Evolution; International Journal of Organic Evolution
|October 2, 2002
PubMed
Summary

Coevolution between crossbills and black spruce in North America shows geographic variation. The presence of red squirrels influences this evolutionary arms race, driving adaptations in both species.

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Area of Science:

  • Evolutionary Biology
  • Ecology
  • Ornithology
  • Botany

Background:

  • Geographic variation in selection pressures is crucial for understanding population divergence.
  • Coevolutionary dynamics between species can shape biodiversity patterns.
  • Crossbills (Loxia) and conifers exhibit complex interactions, particularly in boreal forests.

Purpose of the Study:

  • To investigate the role of a geographic mosaic of coevolution in North American crossbill diversity.
  • To test if black spruce (Picea mariana) defenses against red squirrels (Tamiasciurus hudsonicus) and crossbills (Loxia curvirostra) vary geographically.
  • To examine the reciprocal adaptations between crossbills and conifers, specifically black spruce and lodgepole pine (Pinus contorta).

Main Methods:

Related Experiment Videos

  • Comparative analysis of cone morphology and bill morphology across different geographic locations.
  • Assessment of feeding performance of crossbills on black spruce cones.
  • Evaluation of indirect evidence for seed defense evolution in black spruce.

Main Results:

  • Black spruce on Newfoundland exhibits thicker cone scales, deterring crossbills, suggesting lost defenses against red squirrels.
  • Larger-billed Newfoundland crossbills show higher feeding performance on Newfoundland black spruce cones, indicating adaptation.
  • Mainland black spruce, less defended against crossbills, favors smaller-billed white-winged crossbills (Loxia leucoptera leucoptera).

Conclusions:

  • A geographic mosaic of coevolution, influenced by red squirrels, has been a significant factor in the diversification of North American crossbills.
  • Reciprocal adaptations between crossbills and conifers are evident, with coevolutionary intensity varying with geographic isolation and competitor presence.
  • The study supports the hypothesis of an evolutionary arms race between Newfoundland crossbills and black spruce over the last 9,000 years.