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Bottom‐up control of consumers leads to top‐down indirect facilitation of invasive annual herbs in semiarid Chile
Author(s) -
Madrigal Jaime,
Kelt Douglas A.,
Meserve Peter L.,
Gutierrez Julio R.,
Squeo Francisco A.
Publication year - 2011
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/10-0643.1
Subject(s) - generalist and specialist species , herbivore , introduced species , invasive species , native plant , ecology , mediterranean climate , biology , competition (biology) , population , abundance (ecology) , agroforestry , habitat , demography , sociology
The abundance of exotic plants is thought to be limited by competition with resident species (including plants and generalist herbivores). In contrast, observations in semiarid Chile suggest that a native generalist rodent, the degu ( Octodon degus ), may be facilitating the expansion of exotic annual plants. We tested this hypothesis with a 20‐year data set from a World Biosphere Reserve in mediterranean Chile. In this semiarid environment, rainfall varies annually and dramatically influences cover by both native and exotic annual plants; degu population density affects the composition and cover of exotic and native annual plants. In low‐rainfall years, cover of both native and exotic herbs is extremely low. Higher levels of precipitation result in proportional increases in cover of all annual plants (exotic and native species), leading in turn to increases in degu population densities, at which point they impact native herbs in proportion to their greater cover, indirectly favoring the expansion of exotic plants. We propose that bottom‐up control of consumers at our site results in top‐down indirect facilitation of invasive annual herbs, and that this pattern may be general to other semiarid ecosystems.