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SOIL BIOTA FACILITATE EXOTIC ACER INVASIONS IN EUROPE AND NORTH AMERICA
Author(s) -
Reinhart Kurt O.,
Callaway Ragan M.
Publication year - 2004
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/03-5204
Subject(s) - biota , introduced species , biomass (ecology) , biology , invasive species , ecology , soil biology , population , native plant , botany , soil water , demography , sociology
The primary hypothesis for successful exotic plant invasions is that the invaders have escaped the specialist consumers that control them (Enemy Release Hypothesis). However, few studies have rigorously tested this assertion with biogeographical experiments or considered the effects of soil organisms. We tested the Enemy Release Hypothesis and the enhanced role of mutualisms by comparing density patterns of the North American Acer negundo and European A. platanoides trees in their native and nonnative ranges. Invaders that have escaped their natural enemies are predicted to attain greater densities in nonnative than native ranges. To determine whether interactions with soil biota could explain the population distributions observed in the field, we compared the effects of sterilized and nonsterilized soil associated with Acer and non‐ Acer trees in native and nonnative ranges on the growth of seedlings in the greenhouse. In the field study, distances from focal trees to the nearest Acer conspecifics were 56– 77% less in their nonnative ranges than in their native ranges. In the greenhouse experiment, the effect of soil biota also differed between native and nonnative ranges of Acers . Relative to sterilized controls, soil associated with conspecifics and heterospecifics from the native ranges decreased the total biomass and relative change in height of Acer seedlings by 35% and 40%, respectively. Soil associated with conspecifics in the nonnative ranges decreased the biomass and relative change in height of Acer seedlings by 112% and 64%, respectively; but the soil associated with heterospecifics in the nonnative ranges increased biomass and relative change in height of Acer seedlings by 13% and 37%, respectively. Our results suggest that invasion of Acer s is enhanced by soil biota associated with dominant native species and that the soil biota effect becomes more inhibitory as the Acer s establish. The relative difference in soil biota effects between ranges supports the Enemy Release Hypothesis but also suggests that mutualists are relatively more beneficial to Acer s in their nonnative ranges than in their native ranges. Mutualisms may be relatively more beneficial in nonnative ranges because the invader has escaped from the negative effect of natural enemies that may attenuate the positive effect of mutualists.