The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica

ABSTRACT Coevolution between plants and their animal predators has led to diverse defensive adaptations. Multiple theories of defense propose that there are resource allocation costs associated with producing chemical defenses. One leading hypothesis, optimal defense theory (ODT), suggests that natu...

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Main Authors: Shannon J. Lencioni, Rob Massatti, Ken Keefover‐Ring, Liza M. Holeski
Format: Article
Language:English
Published: Wiley 2024-11-01
Series:Ecology and Evolution
Subjects:
Online Access:https://doi.org/10.1002/ece3.70582
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author Shannon J. Lencioni
Rob Massatti
Ken Keefover‐Ring
Liza M. Holeski
author_facet Shannon J. Lencioni
Rob Massatti
Ken Keefover‐Ring
Liza M. Holeski
author_sort Shannon J. Lencioni
collection DOAJ
description ABSTRACT Coevolution between plants and their animal predators has led to diverse defensive adaptations. Multiple theories of defense propose that there are resource allocation costs associated with producing chemical defenses. One leading hypothesis, optimal defense theory (ODT), suggests that natural selection will result in the allocation of resources to defenses that optimize the cost‐to‐benefit ratio between defense and other functional processes. The population decline of the rare subalpine wetland species, Arizona willow (Salix arizonica), has been attributed to various biotic and abiotic factors, with browsing from wild and domestic ungulates as a significant concern for at least three decades. In a field experiment using natural populations, we compare the relationship between phytochemical defense and height in Arizona willows with and without long‐term protection from browsing via browse exclosures. Consistent with the predictions of ODT, individuals with physical protection from ungulate browsing for multiple years had significantly lower phenolic glycoside (PG) concentrations and increased plant height compared to unprotected individuals. A similar pattern was found across all individuals, whereby total PG concentration and height were negatively correlated. In a short‐term experiment in natural populations, changes in levels of defense were not observed when plants received protection for only one growing season. The contrasting pattern of defense plasticity in response to long‐term versus short‐term physical protection suggests a differential plastic response in this long‐lived species. Delayed reduction in PG concentration may serve as a benefit to avoid mismatches between environmental cues and responses. Our research sheds light on the intricate dynamics between plant‐defense strategies, environmental pressures, and evolutionary adaptations in shaping plant–browser interactions.
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spelling doaj-art-891bcefbfdec4a3aa97828ea1c5cb41b2025-08-20T02:34:35ZengWileyEcology and Evolution2045-77582024-11-011411n/an/a10.1002/ece3.70582The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonicaShannon J. Lencioni0Rob Massatti1Ken Keefover‐Ring2Liza M. Holeski3Department of Biological Sciences, Center for Adaptable Western Landscapes Northern Arizona University Flagstaff Arizona USAU.S. Geological Survey, Southwest Biological Science Center Flagstaff Arizona USADepartment of Botany and Geography University of Wisconsin Madison Wisconsin USADepartment of Biological Sciences, Center for Adaptable Western Landscapes Northern Arizona University Flagstaff Arizona USAABSTRACT Coevolution between plants and their animal predators has led to diverse defensive adaptations. Multiple theories of defense propose that there are resource allocation costs associated with producing chemical defenses. One leading hypothesis, optimal defense theory (ODT), suggests that natural selection will result in the allocation of resources to defenses that optimize the cost‐to‐benefit ratio between defense and other functional processes. The population decline of the rare subalpine wetland species, Arizona willow (Salix arizonica), has been attributed to various biotic and abiotic factors, with browsing from wild and domestic ungulates as a significant concern for at least three decades. In a field experiment using natural populations, we compare the relationship between phytochemical defense and height in Arizona willows with and without long‐term protection from browsing via browse exclosures. Consistent with the predictions of ODT, individuals with physical protection from ungulate browsing for multiple years had significantly lower phenolic glycoside (PG) concentrations and increased plant height compared to unprotected individuals. A similar pattern was found across all individuals, whereby total PG concentration and height were negatively correlated. In a short‐term experiment in natural populations, changes in levels of defense were not observed when plants received protection for only one growing season. The contrasting pattern of defense plasticity in response to long‐term versus short‐term physical protection suggests a differential plastic response in this long‐lived species. Delayed reduction in PG concentration may serve as a benefit to avoid mismatches between environmental cues and responses. Our research sheds light on the intricate dynamics between plant‐defense strategies, environmental pressures, and evolutionary adaptations in shaping plant–browser interactions.https://doi.org/10.1002/ece3.70582browsingoptimal defense theoryphenolic glycosidestrade‐offswillow
spellingShingle Shannon J. Lencioni
Rob Massatti
Ken Keefover‐Ring
Liza M. Holeski
The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
Ecology and Evolution
browsing
optimal defense theory
phenolic glycosides
trade‐offs
willow
title The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
title_full The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
title_fullStr The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
title_full_unstemmed The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
title_short The Cost of Self‐Defense: Browsing Effects in the Rare Plant Species Salix arizonica
title_sort cost of self defense browsing effects in the rare plant species salix arizonica
topic browsing
optimal defense theory
phenolic glycosides
trade‐offs
willow
url https://doi.org/10.1002/ece3.70582
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