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Increased Primary Production from an Exotic Invader Does Not Subsidize Native Rodents.

Lucero JE, Allen PS, McMillan BR - PLoS ONE (2015)

Bottom Line: Invasive plants have tremendous potential to enrich native food webs by subsidizing net primary productivity.Our experiments demonstrate that increased primary productivity associated with exotic plant invasions may not necessarily subsidize consumers at higher trophic levels.In this context, cheatgrass invasion could disrupt native food webs by providing less-preferred resources that fail to enrich higher trophic levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Wildlife Sciences, Brigham Young University, Provo, Utah, United States of America.

ABSTRACT
Invasive plants have tremendous potential to enrich native food webs by subsidizing net primary productivity. Here, we explored how a potential food subsidy, seeds produced by the aggressive invader cheatgrass (Bromus tectorum), is utilized by an important guild of native consumers--granivorous small mammals--in the Great Basin Desert, USA. In a series of field experiments we examined 1) how cheatgrass invasion affects the density and biomass of seed rain at the ecosystem-level; 2) how seed resources from cheatgrass numerically affect granivorous small mammals; and 3) how the food preferences of native granivores might mediate the trophic integration of cheatgrass seeds. Relative to native productivity, cheatgrass invasion increased the density and biomass of seed rain by over 2000% (P < 0.01) and 3500% (P < 0.01), respectively. However, granivorous small mammals in native communities showed no positive response in abundance, richness, or diversity to experimental additions of cheatgrass seeds over one year. This lack of response correlated with a distinct preference for seeds from native grasses over seeds from cheatgrass. Our experiments demonstrate that increased primary productivity associated with exotic plant invasions may not necessarily subsidize consumers at higher trophic levels. In this context, cheatgrass invasion could disrupt native food webs by providing less-preferred resources that fail to enrich higher trophic levels.

No MeSH data available.


Related in: MedlinePlus

Effects of Cheatgrass Supplementation on Small Mammal Communities.Graph a) depicts the predicted effect of cheatgrass supplementation on the abundance, species richness, and/or diversity of native consumers over time. If additional resources subsidize native consumers, supplementation should cause changes in consumer demography over time (line slope) to diverge between control (“Control”) and cheatgrass-supplemented (“Supp”) communities. Graphs b-f) depict the observed effect of cheatgrass supplementation over time (“Sampling period”) on mean ± SE b) abundance of all small mammals combined, c) abundance of all small mammals combined excluding deer mice, d) abundance of Heteromyids, e) species richness, and f) Shannon-Wiener diversity on control (non-supplemented; filled circles) and experimental (cheatgrass-supplemented; open circles) plots in a Great Basin ecosystem (n = 3). Vertical dashed lines represent the time at which cheatgrass supplementation was initiated. All P > 0.55.
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pone.0131564.g002: Effects of Cheatgrass Supplementation on Small Mammal Communities.Graph a) depicts the predicted effect of cheatgrass supplementation on the abundance, species richness, and/or diversity of native consumers over time. If additional resources subsidize native consumers, supplementation should cause changes in consumer demography over time (line slope) to diverge between control (“Control”) and cheatgrass-supplemented (“Supp”) communities. Graphs b-f) depict the observed effect of cheatgrass supplementation over time (“Sampling period”) on mean ± SE b) abundance of all small mammals combined, c) abundance of all small mammals combined excluding deer mice, d) abundance of Heteromyids, e) species richness, and f) Shannon-Wiener diversity on control (non-supplemented; filled circles) and experimental (cheatgrass-supplemented; open circles) plots in a Great Basin ecosystem (n = 3). Vertical dashed lines represent the time at which cheatgrass supplementation was initiated. All P > 0.55.

Mentions: As a whole, small mammals showed no numerical response to cheatgrass supplementation (P = 0.79; Fig 2b). This result could have been driven by deer mice, which were over three times more abundant than any other species at our study sites. To address this, we performed a separate analysis with deer mice excluded, but our results were unaffected (P = 0.76; Fig 2c). Thus, deer mice alone did not drive our results. In addition, neither Heteromyids as a whole (P = 0.78; Fig 2d) nor any individual species of Heteromyid numerically increased in response to cheatgrass supplementation (P = 0.59 for pocket mice, 0.92 for Ord’s kangaroo rats, and 0.32 for chisel-toothed kangaroo rats). Facultative (i.e., non-Heteromyid) granivores were similarly unaffected (P = 0.99). Cheatgrass supplementation did not affect the species richness (P = 0.97; Fig 2e) or diversity (P = 0.94; Fig 2f) of rodent communities.


Increased Primary Production from an Exotic Invader Does Not Subsidize Native Rodents.

Lucero JE, Allen PS, McMillan BR - PLoS ONE (2015)

Effects of Cheatgrass Supplementation on Small Mammal Communities.Graph a) depicts the predicted effect of cheatgrass supplementation on the abundance, species richness, and/or diversity of native consumers over time. If additional resources subsidize native consumers, supplementation should cause changes in consumer demography over time (line slope) to diverge between control (“Control”) and cheatgrass-supplemented (“Supp”) communities. Graphs b-f) depict the observed effect of cheatgrass supplementation over time (“Sampling period”) on mean ± SE b) abundance of all small mammals combined, c) abundance of all small mammals combined excluding deer mice, d) abundance of Heteromyids, e) species richness, and f) Shannon-Wiener diversity on control (non-supplemented; filled circles) and experimental (cheatgrass-supplemented; open circles) plots in a Great Basin ecosystem (n = 3). Vertical dashed lines represent the time at which cheatgrass supplementation was initiated. All P > 0.55.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526561&req=5

pone.0131564.g002: Effects of Cheatgrass Supplementation on Small Mammal Communities.Graph a) depicts the predicted effect of cheatgrass supplementation on the abundance, species richness, and/or diversity of native consumers over time. If additional resources subsidize native consumers, supplementation should cause changes in consumer demography over time (line slope) to diverge between control (“Control”) and cheatgrass-supplemented (“Supp”) communities. Graphs b-f) depict the observed effect of cheatgrass supplementation over time (“Sampling period”) on mean ± SE b) abundance of all small mammals combined, c) abundance of all small mammals combined excluding deer mice, d) abundance of Heteromyids, e) species richness, and f) Shannon-Wiener diversity on control (non-supplemented; filled circles) and experimental (cheatgrass-supplemented; open circles) plots in a Great Basin ecosystem (n = 3). Vertical dashed lines represent the time at which cheatgrass supplementation was initiated. All P > 0.55.
Mentions: As a whole, small mammals showed no numerical response to cheatgrass supplementation (P = 0.79; Fig 2b). This result could have been driven by deer mice, which were over three times more abundant than any other species at our study sites. To address this, we performed a separate analysis with deer mice excluded, but our results were unaffected (P = 0.76; Fig 2c). Thus, deer mice alone did not drive our results. In addition, neither Heteromyids as a whole (P = 0.78; Fig 2d) nor any individual species of Heteromyid numerically increased in response to cheatgrass supplementation (P = 0.59 for pocket mice, 0.92 for Ord’s kangaroo rats, and 0.32 for chisel-toothed kangaroo rats). Facultative (i.e., non-Heteromyid) granivores were similarly unaffected (P = 0.99). Cheatgrass supplementation did not affect the species richness (P = 0.97; Fig 2e) or diversity (P = 0.94; Fig 2f) of rodent communities.

Bottom Line: Invasive plants have tremendous potential to enrich native food webs by subsidizing net primary productivity.Our experiments demonstrate that increased primary productivity associated with exotic plant invasions may not necessarily subsidize consumers at higher trophic levels.In this context, cheatgrass invasion could disrupt native food webs by providing less-preferred resources that fail to enrich higher trophic levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Wildlife Sciences, Brigham Young University, Provo, Utah, United States of America.

ABSTRACT
Invasive plants have tremendous potential to enrich native food webs by subsidizing net primary productivity. Here, we explored how a potential food subsidy, seeds produced by the aggressive invader cheatgrass (Bromus tectorum), is utilized by an important guild of native consumers--granivorous small mammals--in the Great Basin Desert, USA. In a series of field experiments we examined 1) how cheatgrass invasion affects the density and biomass of seed rain at the ecosystem-level; 2) how seed resources from cheatgrass numerically affect granivorous small mammals; and 3) how the food preferences of native granivores might mediate the trophic integration of cheatgrass seeds. Relative to native productivity, cheatgrass invasion increased the density and biomass of seed rain by over 2000% (P < 0.01) and 3500% (P < 0.01), respectively. However, granivorous small mammals in native communities showed no positive response in abundance, richness, or diversity to experimental additions of cheatgrass seeds over one year. This lack of response correlated with a distinct preference for seeds from native grasses over seeds from cheatgrass. Our experiments demonstrate that increased primary productivity associated with exotic plant invasions may not necessarily subsidize consumers at higher trophic levels. In this context, cheatgrass invasion could disrupt native food webs by providing less-preferred resources that fail to enrich higher trophic levels.

No MeSH data available.


Related in: MedlinePlus