Invasive species can threaten the con- servation of biodiversity and natural resources and incur considerable eco- nomic losses. Invasive species man- agement programs therefore aim to reverse or mitigate the impacts of inva-
sion, but these programs can have severe
negative impacts on native species and
ecosystems (1, 2), because invasive species
integrate into their new ecosystems and
can assume ecological functions previously
carried out by native species. Indirect ef-
fects of management are likely to become
more common as existing invaders form
new interactions and new species continue
to be introduced. On page 1028 of this is-
sue, Lampert et al. report an optimal man-
agement model that shows how invasive
species control can be combined with other
ecosystem goals (3).
Rapid removal of an invasive plant is important for reducing its population, preventing further spread, and helping to ultimately
attain eradication. However, rapid removal
can lead to problems if native species use
the invader as a resource. The program aiming to eradicate an invasive cordgrass species (a hybrid between the invasive Spartina
alterniflora and the native S. foliosa) in San
Francisco Bay was proceeding quickly and
effectively (see the figure) when scientists
noticed declines in an endangered bird, the
California clapper rail, which nests in invasive hybrid Spartina. The control program
for invasive hybrid Spartina was temporarily
halted, leaving 8% of the originally infested
area still containing the invader. The bird
also nests in native Spartina, but the native
Managing the side effects
of invasion control
By Yvonne M. Buckley1,2 and Yi Han2
Efforts to control invasive species must be adapted to avoid
unintended damage to native species and ecosystems
Different perceptions. The California clapper rail, an endangered bird species, sees no difference between a patch
of invasive Spartina and a patch of native Spartina, laying eggs in either habitat. However, ecosystem managers view
them very differently, aiming to eradicate the invasive grass and to encourage regrowth of the native one. Lampert et
al. now report a model that takes undesired side effects of invader removal into account.
rable to the sulfur cycling under alkaline
conditions reported by Flynn et al.
In alkaline environments such as groundwater aquifers, iron(III)-reducing microorganisms apparently have an ecological
advantage when equipped with the ability for
sulfur reduction. Flynn et al. argue that both
traits could have coevolved in one microorganism in the alkaline ocean cradle of
early Earth. However, these early oceans
might have been acidic (8, 9). Moreover,
iron reduction would not have evolved in
a solely alkaline world, where the reaction
is unfavorable. The presence of multiple
respiratory pathways in one microorganism provides flexibility to changing environmental conditions. The maintenance of
both iron and sulfur reduction pathways
implies that iron-reducing microorganisms
are exposed to fluctuations in electron acceptor availability.
The work of Flynn et al. provides an
intriguing explanation for how iron-reducing bacteria can thrive in alkaline environments. Some iron reducers have, in
addition, the capability to use sulfur disproportionation, the fermentation of sulfur to
sulfide and sulfate (10). In fact, sulfur disproportionation also becomes more favorable with alkaline pH and has been shown
to occur at pH 10 in cultures isolated from
a soda lake (11). Sulfur-reducing and sul-fur-disproportionating bacteria are, thus,
likely to compete for sulfur as a common
substrate, especially in carbon-poor aquifers, because sulfur disproportionation is
independent of organic carbon substrates.
In the future, it will be important to dissect
the quantitative role of these intertwined
reactions of the sulfur and iron cycle and
the bacteria involved in the environment. ■
REFERENCES AND NOTES
1. T. M. Flynn, E. J. O’Loughlin, B. Mishra, T. DiChristina, K. M.
Kemner, Science 344, 1039 (2014).
2. D. R. Lovley, S. Goodwin, Geochim.Cosmochim.Acta
52, 2993 (1988).
3. J. K. Fredrickson et al ., Nat. Rev. Microbiol. 6, 592
4. T. M. Flynn et al., BMC Microbiol.13, 146 (2013).
5. D. E. Canfield et al ., Science 330, 1375 (2010).
6. L.Holmkvist, T.G.Ferdelman, B.B.Jorgensen, Geochim.
Cosmochim. Acta 75, 3581 (2011).
7. L. Holmkvist et al., Deep Sea Res. Part I Oceanogr.
Res. Pap. 58, 493 (2011).
8. D. L. Pini, in Lectures in Astrobiology Vol. I , M.
Gargaud et al., Eds. (Springer, Berlin/Heidelberg, 2005),
9. M. J. Russell et al ., Astrobiol. 14, 308 (2014).
10. D. E. Holmes, D. R. Bond, D. R. Lovley, Appl. Environ.
Microbiol. 70, 1234 (2004).
11. A.Poser et al., Extremophiles 17, 1003(2013).
We thank C. Fischer, R. S. Arvidson, and A. LÜttke
(University of Bremen) for providing the high-resolution field emission scanning electron microscopy
image of Shewanella oneidensis MR-1.