Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Benefits and Constraints on Plant Defense against Herbivores: Spines Influence the Legitimate and Illegitimate Flower Visitors of Yellow Star Thistle, Centaurea solstitialis L. (Asteraceae)

Anurag A. Agrawal, Jennifer A. Rudgers, Louis W. Botsford, David Cutler, Jessica B. Gorin, Carolyn J. Lundquist, Brian W. Spitzer and Alisa L. Swann
The Southwestern Naturalist
Vol. 45, No. 1 (Mar., 2000), pp. 1-5
DOI: 10.2307/3672545
Stable URL: http://www.jstor.org/stable/3672545
Page Count: 5
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Benefits and Constraints on Plant Defense against Herbivores: Spines Influence the Legitimate and Illegitimate Flower Visitors of Yellow Star Thistle, Centaurea solstitialis L. (Asteraceae)
Preview not available

Abstract

The evolutionary ecology of plant defenses against herbivores is generally understood in a cost-benefit framework. We studied the ecological consequences of the spines of Centaurea solstitialis L. (yellow star thistle) which are typically thought of as defenses against mammalian herbivores. By experimentally removing spines, which consist of dead tissue, we show that "nectar robbing" lepidopteran visitors are deterred by naturally occurring spines (a benefit). Unlike the lepidoptera, legitimate pollinators (bees and flies) were not more likely to visit spineless flower heads, although bees and flies did spend 20% more time per visit on spineless flower heads. One potential cost of having spines is the lower time per visit of the bees. The net result of spine removal from flower heads was a 22% reduction in the percentage of filled seeds of spineless flower heads compared to spined controls. Thus, spines of yellow star thistle may not only deter mammalian herbivory, but also deter lepidoptera which are illegitimate flower visitors. Although the spines may be energetically costly (not measured in this experiment), or costly because of other ecological trade-offs, it appears that these costs are outweighed by the benefits of spines as a plant defense. /// La ecología evolutiva de las defensas de las plantas contra herbívoros es generalmente entendida bajo una estructura de costos y beneficios. Estudiamos las consecuencias ecológicas de las espinas de Centaurea solstitialis L. las cuales son típicamente consideradas como defensas contra mamíferos herbívoros. Al eliminar experimentalmente las espinas, que consisten de tejido muerto, demostramos que las especies lepidópteras que roban néctar de estas flores son repelidas cuando las espinas están naturalmente presentes (un beneficio). A diferencia de las lepidópteras, las polinizadoras legítimas (abejas y moscas) no fueron más propensas a visitar las cabezas florales sin espinas, aunque las abejas y las moscas pasaron 20% más tiempo en cada visita en las cabezas florales sin espinas. Un costo posible de tener espinas es menos tiempo por visita de abejas. El resultado neto de la eliminación de espinas de las cabezas florales fue una reducción del 22% en el porcentaje de semillas llenas en las cabezas florales sin espinas comparadas con los controles con espinas. Así, las espinas de esta planta no sólo repelen a los mamíferos herbívoros, también repelen a especies lepidópteras las cuales son visitadoras ilegítimas de flores. A pesar de ser las espinas energéticamente costosas (lo que no se midió en este experimento), o costosas por otros balances ecológicos, parece que estos beneficios que tienen las espinas como defensas para las plantas sobrepasan sus costos.

Page Thumbnails

  • Thumbnail: Page 
[1]
    [1]
  • Thumbnail: Page 
2
    2
  • Thumbnail: Page 
3
    3
  • Thumbnail: Page 
4
    4
  • Thumbnail: Page 
5
    5