Document Detail

Leaf drop in evergreen Ceanothus velutinus as a means of reducing herbivory.
MedLine Citation:
PMID:  18831166     Owner:  NLM     Status:  MEDLINE    
Conventional explanations for deciduousness do not include losses to herbivory. However, a recent explanation posits that deciduous leaf drop allows trees to reduce their herbivore loads and that this benefit of the deciduous habit may partly offset lost opportunities for photosynthesis. Much of the damage caused by chewing herbivores occurs early in the season when adult insects colonize as new leaves are expanding; trees without leaves from previous leaf flushes at this time are less attractive and suffer less cost of herbivory. I tested this hypothesis using Ceanothus velutinus, an evergreen shrub that shows considerable individual variation in leaf retention. Stems that held more leaves through winter experienced more chewing damage the following season. Stems with leaves experimentally removed through winter also were less likely to receive chewing damage the following season. At least some herbivores in this system make oviposition decisions before new leaves have expanded, and old leaves may provide cues about the suitability of the stem. Holding leaves through winter increased the likelihood of herbivory, and experimental protection from herbivores caused 60% greater inflorescence production compared to unprotected stems. However, the cost of leaf retention was more than offset by an overall benefit. Stems that were allowed to keep winter leaves produced larger new leaves in summer and expanded them more rapidly in the season than stems with winter leaves experimentally removed. As a result, stems with leaves through winter experienced higher survival, four times as many inflorescences, and 40 times as many fruits as shoots that were experimentally defoliated. Losses to herbivores may be an unappreciated cost of leaf retention, and cost-benefit models of deciduous and evergreen behavior should include these losses.
Richard Karban
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Ecology     Volume:  89     ISSN:  0012-9658     ISO Abbreviation:  Ecology     Publication Date:  2008 Sep 
Date Detail:
Created Date:  2008-10-03     Completed Date:  2008-10-28     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0043541     Medline TA:  Ecology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2446-52     Citation Subset:  IM    
Department of Entomology, University of California, Davis, California 95616-8584, USA.
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MeSH Terms
Ceanothus / physiology*
Feeding Behavior / physiology*
Invertebrates / physiology*
Plant Leaves / physiology*
Time Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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