An official website of the United States government
Abstract The enemy release hypothesis (ERH) attributes the success of some exotic plant species to reduced top‐down effects of natural enemies in the non‐native range relative to the native range. Many studies have tested this idea, but very few have considered the simultaneous effects of multiple kinds of enemies on more than one invasive species in both the native and non‐native ranges. Here, we examined the effects of two important groups of natural enemies–insect herbivores and soil biota–on the performance ofTanacetum vulgare(native to Europe but invasive in the USA) andSolidago canadensis(native to the USA but invasive in Europe) in their native and non‐native ranges, and in the presence and absence of competition.In the field, we replicated full‐factorial experiments that crossed insecticide,T. vulgare–S. canadensiscompetition, and biogeographic range (Europe vs. USA) treatments. In greenhouses, we replicated full‐factorial experiments that crossed soil sterilization, plant–soil feedback, and biogeographic range treatments. We evaluated the effects of experimental treatments onT. vulgareandS. canadensisbiomass.The effects of natural enemies were idiosyncratic. In the non‐native range and relative to populations in the native range,T. vulgareescaped the negative effects of insect herbivores but not soil biota, depending upon the presence ofS. canadensis; andS. canadensisescaped the negative effects of soil biota but not insect herbivores, regardless of competition. Thus, biogeographic escape from natural enemies depended upon the enemies, the invader, and competition. Synthesis:By explicitly testing the ERH in terms of more than one kind of enemy, more than one invader, and more than one continent, this study enhances our nuanced perspective of how natural enemies can influence the performance of invasive species in their native and non‐native ranges.
more »
« less
Soil origin corresponds with variation in growth of an invasive Centaurea , but not of non‐invasive congeners
Abstract Why only a small proportion of exotic species become invasive is an unresolved question. Escape from the negative effects of soil biota in the native range can be important for the success of many invasives, but comparative effects of soil biota on less successful exotic species are poorly understood. Studies of other mechanisms suggest that such comparisons might be fruitful. Seeds of three closely relatedCentaureaspecies with overlapping distributions in both their native range of Spain and their nonnative range of California were grown to maturity in pots to obtain an F1 generation of full sibling seeds with reduced maternal effects. Full sibling F1 seeds from both ranges were subsequently grown in pots with inoculations of soil from either the native or nonnative ranges in a fully orthogonal factorial design. We then compared plant biomass among species, regions, and soil sources. Our results indicate that escape from soil pathogens may unleash the highly invasiveCentaurea solstitialis, which was suppressed by native Spanish soils but not by soils from California. In contrast, the two non‐invasiveCentaureaspecies grew the same on all soils. These results add unprecedented phylogenetically controlled insight into why some species invade and others do not.
more »
« less
- Award ID(s):
- 1757351
- PAR ID:
- 10454574
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 101
- Issue:
- 10
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Understanding the mechanisms governing biological invasions has implications for population dynamics, biodiversity, and community assembly. The enemy escape hypothesis posits that escape from enemies such as herbivores and predators that were limiting in the native range helps explain rapid spread in the introduced range. While the enemy escape hypothesis has been widely tested aboveground, data limitations have prevented comparisons of below- ground mechanisms for invasive and noninvasive introduced species, which limits our understanding of why only some introduced species become invasive. We assessed the role of soil biota in driving plant invasions in a phylogenetic meta−analysis, incorpo- rating phylogeny in the error structure of the models, and comparing live and sterilized conditioned soils. We found 29 studies and 396 effect size estimates across 103 species that compared live and sterilized soils. We found general positive effects of soil biota for plants (0.099, 95% CI 0.0266, 0.1714), consistent with a role of soil mutualists. The effect size of soil biota among invaders was 3.2× higher than for natives, the strength of effects was weaker for older conditioning species with a longer introduced history, and enemy escape was stronger for distant relatives. In addition, invasive species had a weaker allocation tradeoff than natives. By demonstrating that the net effect of soil biota is more positive for invasive than native and noninvasive introduced species, weakens over time since introduction, and strengthens as phy- logenetic distance increasing, we provide mechanistic insights into the considerable role of soil biota in bio- logical invasions, consistent with the predictions of the enemy escape hypothesis.more » « less
-
Understanding the mechanisms governing biological invasions has implications for population dynamics, biodiversity, and community assembly. The enemy escape hypothesis posits that escape from enemies such as herbivores and predators that were limiting in the native range helps explain rapid spread in the introduced range. While the enemy escape hypothesis has been widely tested aboveground, data limitations have prevented comparisons of belowground mechanisms for invasive and noninvasive introduced species, which limits our understanding of why only some introduced species become invasive. We assessed the role of soil biota in driving plant invasions in a phylogenetic meta−analysis, incorporating phylogeny in the error structure of the models, and comparing live and sterilized conditioned soils. We found 29 studies and 396 effect size estimates across 103 species that compared live and sterilized soils. We found general positive effects of soil biota for plants (0.099, 95% CI = 0.0266, 0.1714), consistent with a role of soil mutualists. The effect size of soil biota among invaders was 3.2× higher than for natives, the strength of effects was weaker for older conditioning species with a longer introduced history, and enemy escape was stronger for distant relatives. In addition, invasive species had a weaker allocation tradeoff than natives. By demonstrating that the net effect of soil biota is more positive for invasive than native and noninvasive introduced species, weakens over time since introduction, and strengthens as phylogenetic distance increasing, we provide mechanistic insights into the considerable role of soil biota in biological invasions, consistent with the predictions of the enemy escape hypothesis.more » « less
-
Abstract Some invasive plant species rapidly evolve greater size and/or competitive ability in their nonnative ranges. However, it is not well known whether these traits transfer back to the native range, or instead represent genotype‐by‐environment interactions where traits are context specific to communities in the new range where the evolution occurred. Insight into transferability vs. context specificity can be tested using experiments performed with individuals from populations from the native and nonnative ranges of exotic invasive species. Using a widespread invasive plant species in Europe,Solidago gigantea, we established reciprocal common garden experiments in the native range (Montana, North America;n = 4) and the nonnative range (Hungary, Europe;n = 4) to assess differences in size, vegetative shoot number, and herbivory between populations from the native and nonnative ranges. In a greenhouse experiment, we also tested whether the inherent competitive ability of genotypes from 15 native and 15 invasive populations differed when pitted against 11 common native North American competitors. In common gardens, plants from both ranges considered together produced five times more biomass, grew four times taller, and developed five times more rhizomes in the nonnative range garden compared to the native range garden. The interaction between plant origin and the common garden location was highly significant, with plants from Hungary performing better than plants from Montana when grown in Hungary, and plants from Montana performing better than plants from Hungary when grown in Montana. In the greenhouse, there were no differences in the competitive effects and responses ofS. giganteaplants from the two ranges when grown with North American natives. Our results suggest thatS. giganteamight have undergone rapid evolution for greater performance abroad, but if so, this response does not translate to greater performance at home.more » « less
-
Abstract The size and frequency of resource pulses can affect plant interactions and increase the abundance of invasive species relative to native species. We examined resource pulses generated during the desiccation and rehydration of communities of native biological soil crust (biocrust)‐forming mosses, in the context of positive associations between biocrusts and the invasive forb,Centaurea stoebe.We surveyedCentaureaand biocrust cover and evaluated how interactions amongCentaurea, biocrusts and water pulses influenced plant biomass and soil nitrogen in a field experiment.Centaureaseedling and biocrust interactions were also compared in a greenhouse experiment to evaluate differences related to life stage.In field surveys,Centaureaand biocrusts were positively associated. Across water pulse treatments, biocrust biomass decreased whenCentaureawas removed, indicating thatCentaureafacilitated biocrusts. Biocrusts did not affect adultCentaureain the field, butCentaureaseedling biomass was greater when grown with biocrusts in the greenhouse. Water pulses did not affect plant biomass, but interactions betweenCentaureaand biocrusts corresponded with variation in the effect of water pulses on soil nitrogen which were not evident whenCentaureaor biocrusts were grown alone. Twenty‐four hours after large water pulses were added, soilwas nine times higher in plots where biocrusts andCentaureaco‐occurred compared with small water pulse plots. In these same plots, soiltended to be lower at the end of the experiment.These results highlight positive interactions between an invasive exotic forb and native moss biocrust. Water pulses influenced soil nitrogen availability when both plants co‐occurred, but did not affect plant biomass, suggesting that resource pulses and species interactions can interact to affect ecosystem processes. A freePlain Language Summarycan be found within the Supporting Information of this article.more » « less
