Dam Invaders: Impoundments Facilitate Biological Invasions into Freshwaters
Author(s): Pieter T. J. Johnson, Julian D. Olden and M. Jake Vander Zanden
Source: Frontiers in Ecology and the Environment, Vol. 6, No. 7 (Sep., 2008), pp. 357-363
Published by: Ecological Society of America
Stable URL: http://www.jstor.org/stable/20440936 .
Accessed: 08/10/2014 16:50
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .
http://www.jstor.org/page/info/about/policies/terms.jsp
.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of
content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms
of scholarship. For more information about JSTOR, please contact support@jstor.org.
.
Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Frontiers
in Ecology and the Environment.
http://www.jstor.org
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
RESEARCH COMMUNICATIONS
Dam
invaders:
biological
RESEARCH COMMUNICATIONS_
impoundments
invasions
into
facilitate
freshwaters
PieterTJ Johnsonl*,JulianD Olden2, andM JakeVander Zanden3
of theglobal biodiversitycrisis,with more declining and extinct
Freshwaterecosystemsare at the forefront
in
or
marine
environments.
Hydrologic alterationsand biological invasions repre
terrestrial
species than
sent twoof thegreatestthreatsto freshwater
biota, yet the importanceof linkagesbetween thesedriversof
environmentalchange remainsuncertain.Here,we quantitativelytestthehypothesisthat impoundments
facilitatethe introductionand establishmentof aquatic invasivespecies in lake ecosystems.By combining
and geographical distributionof fivenuisance
data on boating activity,water body physicochemistry,
invaders in theLaurentianGreat Lakes region,we show thatnon-indigenousspecies are 2.4 to 300 times
more likelyto occur in impoundmentsthan in natural lakes,and that impoundmentsfrequentlysupport
comparisonsof thecontemporaryand historical landscapes revealed that
multiple invaders.Furthermore,
impoundmentsenhance the invasion riskof natural lakesby increasingtheirproximityto invadedwater
bodies, highlightingthe role of human-alteredecosystemsas "stepping-stone"habitats for the continued
spreadof freshwaterinvaders.
Front Ecol Environ 2008; 6(7): 357-363, doi:10.1890/070156
expandingglobalnetworkof dams and impound Shea andChesson 2002;Havel etal. 2005). In additionto
habitats,
ments has dramaticallychanged thedistribution
of increasingthe abundance of standing-water
largerandmore accessible
are frequently
freshwateracross the landscape.Broad-scale physical impoundments
impactsof suchhydrologicalalterationsincluderiverine tohumans thanarenatural lakes;theyarebuilton river
with hydrologicconnectionsto neighboring
sedimentretention,enhanced evapora
ine systems
fragmentation,
tion,and increasedgreenhouse-gas
production(Nilssonet lakes,and are youngerin age and experiencegreaterdis
turbancethando naturalsystems(Thorntonet al. 1990;
al. 2005;Dudgeon etal. 2006; Poffetal. 2007). Less under
arehypothesized
interact Havel etal. 2005).All of theseinfluences
stood,however,ishow dams or impoundments
with otherlarge-scale
agentsofglobalchange,suchas bio
to enhance species colonization and establishment.If
fornon
also providegreateropportunities
logicalinvasions.In theUS alone,more than80 000 large impoundments
speciestospreadacrossthe landscape,identifi
damsand 2.5million smallerimpoundments
populatethe indigenous
landscape(Graf1999; Smith et al. 2002), while close to cation of these alteredenvironmentsas invasionhubs
and preventingfuture
1000 introducedfreshwater
species contributeto the could aid efforts
aimedat predicting
invasions(MuirheadandMacIsaac 2005;Hulme 2006).
ofnativebiodiversity
endangerment
(Rahel 2002;USGS
on human behavior (ie boat
By coupling information
2007). Together,dam constructionand biological inva
and the
characteristics,
sions aremajor contributorsto the currentbiodiversity ing),waterbodyphysicochemical
we
of fivenuisance invaders,
crisisin freshwater
which exhibithigherrates geographicaldistributions
ecosystems,
and quantitativelyevaluated the hypothesisthat impound
of extinctionand a greaterproportionof threatened
ormarine environ ments facilitatebiological invasions into freshwaters.
endangeredspeciesthan in terrestrial
we addressedthefollowing
questions:
ments (Ricciardiand Rasmussen 1999; Dudgeon et al. Specifically,
2006). Despite the increasing
ubiquityofboth impound
ments and invasivespecies in freshwater
(1) Are impoundmentsmore frequentlyinvaded
ecosystems,a
pressing,
yetunansweredquestion remains:do impound
comparedtonatural lakes?
offactors
relatedtocolonization
ments enhance invasionriskbypromotingtheestablish
(2)What combination
ment and spreadofnon-indigenousspecies?
potential(ie propagulepressure)and establishment
Creation of impoundments
mightbe expected to pro
suitability
(ie species'ecologicalniche) accountfor
observed differencesin invader occurrences
mote invasionsby increasingcolonizationopportunities
waterbodies?
betweennaturaland impounded
fornon-indigenoustaxa and by enhancing theirsub
sequent establishmentsuccess (Kolar and Lodge 2000;
(3) Has thewidespread creation of impoundments
ecosys
facilitatedspecies invasionsin freshwater
'Ecologyand EvolutionaryBiology,UniversityofColorado, Boulder,
tems?
An
CO *(pieter.johnson(colorado.edu);2SchoolofAquatic and Fishery
Sciences, University of Washington, Seattle, WA; 'Center for
Limnology,UniversityofWisconsin,Madison, WI
Our studyexamined fivewidespreadnuisance invaders
associated with substantial ecological or economic
C)
The
Ecological
Society
of
America
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
a rntersai
PT) Johnsonetal.
invasions
and freshwater
Impoundments
N
/
0 30 60 km
Li.S / .LJLake
Myriophyllum
I
I
I
Eurasianwatermilfoil
88"W
90>W
92tW
_
Superior
m.
Zebra mussel
~~~~~~~~~~Dreissena
polymorpha
A
4
46"N
spicatum
x
N
-
A
Af
^_
*
waterflea
~~~~~~~~~~~~~~~~Spiny
longimanus
X
ww
wBythotrephes
2&s
A A~~
*A
A
t
j
Wisconsin
A
AAf
AAA
~AA
A
A
A
44?N
6
A A
Rainbow smelt
AOsmerusmordax
MinnesotaA
A*
|
lowi l \*1s
A00-J
4wiQ Rusty crayfish
Iowa
A AA A
Water
42*N
rusticus
~~~~~~~~~Orconectes
body type
* Natural lake
A Impoundment
Illinois
species
forwhichat leastonenon-indigenous
and impoundments
(redtriangles)
ofnaturallakes(bluecircles)
Figure1. Distribution
Eurasianwatermilfoil,
zebra
Michigan(n = 1080). Invasivespeciesincluded:
inWisconsinandUpperPeninsula
isestablished
crayfish.
andrusty
smelt,
waterfleas,rainbow
mussels,spiny
spicatum), hydropower,paper mills, and recreation,creating a
impacts:Eurasianwatermilfoil(Myriophyllum
waterbodies (Graf
spiny
water
fleas diversemosaic ofnaturaland artificial
polymorpha),
mussels
(Dreissena
zebra
mor
1999).Moreover,byvirtueof theircloseproximityto the
rainbowsmelt(Osmerus
longimanus),
(Bythotrephes
rusticus;
Figure1). By highlyinvadedGreat Lakes, inland lakes in this region
(Orconectes
crayfish
dax), and rusty
of non-indige
includinginvasivespeciesthatvarywidely in taxonomy, have been colonizedby a broad diversity
introductionpathway, life history,and physiological nous species(Holeck etal. 2004).
we providea robusttestof theaforemen
requirements,
tioned questions and reduce the likelihood that our * Methods
results are idiosyncraticto a single species. The
differ
how naturallakesand impoundments
LaurentianGreat Lakes regionoffersan ideal testing To determine
and
invader
introduction
affect
likely
to
in
inva
attributes
biological
between
groundto evaluate interactions
for
data
physicochemical
compiled
in
we
establishment,
rich
Already
impoundments.
sions and hydrologic
1081
impoundments)
and
(4200
lakes
bodies
5281
water
has
undergone
lakes,
this
region
natural
glacially-formed
acrossWisconsin and theupperpeninsulaof
extensivedammingin the20th century,foragriculture, distributed
_wwwvfonflersinecology-org
of
America.
0 TheEcological
Society
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
PTJJohnsonetal.
Impoundments
and freshwater
invasions
Michigan.We focusedon environmentalcharacteristics ments ("historical"environment).
We focusedthisanaly
as these
potentiallyimportantforaquatic invadercolonization sis on zebra mussels
and Eurasian
watermilfoil,
and establishment, including surface area (km2), species are among themost likelyto be transported
by
upstreamwatershed area (km2),maximum depth (m), boating activity,and because theycontrast a recent
mean summer
water clarity(Secchi depth inm), specific invasion (eg zebramussels; firstrecordedinWisconsin
conductance ([Lmhos cm-,), hydrologic connectivity in 1994) with a well-establishedinvasion (egwatermil
(seepage versusdrainage),human accessibility(defined foil; firstrecorded inWisconsin in 1965). For each
by thepresenceof a boat landingornavigablewaterway), uninvadednatural lake,we calculated thechange indis
and straight-line
distance to thenearestGreat Lake (as a tance to the nearest invadedwater body between the
sourcepopulationofnon-indigenousspecies,particularly historical and contemporaryscenarios.We compared
forspinywater fleas,zebramussels,and rainbowsmelt). observed changes in distance to the average distance
Boatermovementamongwaterbodies isone of thedom
traveledby90% of registered
boaters inWisconsin using
inanttransport
vectorsforthespreadofmany freshwater trailers(48 km;Buchan and Padilla 1999), and consid
non-indigenousspecies, so we followedLeung et al. ereduninvaded lakeswithin 48 km of an invadedwater
(2006) in using thenumberof boat landingsperwater body highly vulnerable to a potential introduction
bodyas a proxyforinvaderpropagulepressure.In support event. Importantly,
because not all lakesand impound
of thismetric,we founda strongpositive relationship ments inWisconsin were surveyed,calculated changes
between thenumberof boat landingsand human visita
indistancebetween invadedand uninvadedwater bod
tionsfor937waterbodies,accordingtoboatermovement iesare consideredestimates.This analysiscapitalizeson
data froma randomizedsurveyof >50 000 registered the observation that inter-lakedistance is negatively
Wisconsin boaters(WebPanel 1).
correlated to invasion risk and assumes that, in the
on water body physico absence of impoundments,
We combined information
thenumberof invadednat
and boatingbehaviorwith themost recentdis
chemistry
ural lakeswould not have increased(eg due to increased
tributional
data forEurasianwatermilfoil(n = 682 sam visitationratesbyboaters).
pledwaterbodies), zebramussels (n = 353), rusty
crayfish
(n = 567), spinywater fleas(n = 341), and rainbowsmelt M Results
(n = 83; Figure1). Only data thatmet strictcriteria
were
used; includeddata (1) pertainedonly toaquatic invaders Among the1080 sampledwaterbodies, the invasionlike
reasonablyclassifiedas "nuisance"species; (2) contained lihoodof impoundments
exceeded thatof natural lakes.
presenceand absencedocumentation;(3) were collected For each of thefiveinvaders,impoundments
were signifi
validatedsamplingprotocols;and (4) cantlymore likelythannaturallakesto be invaded(two
usingstandardized,
were recordedby trainedbiologistsor fromvouchered tailedPearson chi-squaredanalysis,df = 1, P < 0.05;
when theypertainedto invaderoccurrences. Figure2a). The associationbetween impoundments
specimens,
and
Surveyedwater bodies (n = 1080) were broadlydistrib invaderoccurrencesvaried among the species:Eurasian
utedacrossthestudyregion(Figure1) andwere similarto watermilfoil(logisticregression
odds ratio = 2.4), rusty
accessiblewater bodies in the comprehensivedatabase. crayfish
(2.5), zebramussel (2.7), rainbowsmelt(3.0), and
Sampling protocols,data sources,and an evaluation of spinywater flea (7.8). Among the 189 water bodies sur
potentialsystematic
biasesarepresentedinWebPanel 1.
most commonnon-indigenousspecies
veyedforthe three
We used two-tailedchi-squaredtestsof independence (zebramussels,Eurasianwatermilfoil,
and rustycrayfish),
to compare the invasionlikelihoodof natural lakesand impoundments
were also significantly
more likelythan
impoundments
foreach invader,and assessed the effect naturallakesto support
multiple invaders(Figure2b).
sizeof significant
using theodds ratio.The
relationships
Physicaland biological differences
between lakesand
odds ratioestimatesthe increaseinodds ofbeing inone
contributedto theobserveddifferences
in
impoundments
outcomecategory(eg invaded)when thevalue of a pre
invasionprevalence. In comparisonwith natural lakes,
dictorchanges (eg fromnatural lake to impoundment). impoundments
were 1.4 times lower in averagewater
We subsequentlyused logistic regressionto develop clarity,
2.1 timeshigherinconductivity,
4.3 timeshigher
species-specific
models thatpredictedtheprobabilityof in numberof boat landings,8.7 times largerin surface
invaderoccurrenceas amultivariatefunction
ofvariables area,and 44.6 timeslargerinwatershedarea (WebTable
related to invader colonization and establishment, 1). Impoundments
were also 68% more likelythannat
includingimpoundment
statusand thephysicochemical ural lakes to be accessible by humans and 54% more
variablesdescribedabove (seeWebPanel 1).
likelyto have hydrologicconnectionsvia streamnet
Finally,we estimatedthepotential forimpoundments works (WebTable 1). Nevertheless,among thebest-sup
to increasetheriskof invasionintonaturallakesbycom ported logistic regression
models (based on Akaike's
paring the straight-line
distances between each unin
information
criterion[AIC] values and associateddiag
vaded natural lakeand thatlake'snearestinvadedneigh nostics), impoundmentstatus remained a significant
borunder twoscenarios:a landscapewith impoundments explanatory
variableforpredictingtheoccurrenceof four
(present-dayenvironment)and one without impound out of fiveinvaders(odds ratiorangingfrom2.1 to300),
C The EcologicalSocietyofAmerica
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
Impoundments
and freshwater
invasions
(a)
100
(b)
Natural
lakes
-ge2(
m
Impoundments
50n
T
TI
0
60|
inyIwatur las
-
Impoundments
80
V
PTJJohnsonetal.
v~~~~~~~
0 ~~~~~~~~~~~~~40
I
(~60
30
0
0
40
20
20
T
10
0
0
0
,~~ ~~o
Ole e~~~
C"
0
1
2
3
Number of invaders
Figure 2. (a) Percentage of surveyed lakes and impoundmentsthatsupported spinywater fleas (n = 341 sampledwater bodies),
zebra mussels (n = 353), rainbow smelt (n = 83), rustycrayfish(n = 567), and Eurasian watermilfoil (n = 682). Error bars
represent 95% confidence intervals,for a proportion. According to two-tailed Pearson chi-squared tests of independence,
**
= P <
over-invaded relative tonatural lakes for each invader (C= P < 0.05, **= P < 0005,
impoundmentswere significantly
0.0005). (b) Comparison of thenumber of invaders in lakesand impoundmentsfor the 189 water bodies sampled for the threemost
common invaders (two-tailedPearson0~31 = 15.219, P = 0.002).
ofotherenviron ered vulnerableto boatermovement froman invaded
even afteraccountingforthe influence
mental and anthropogenicfactorslikelyto affectintro waterbodyfrom45 lakesto67 lakes(-50% increase).For
Eurasianwatermilfoil,
impoundments
themore established
ductionand establishment
(Table 1).Overall ratesofcor
distanceby23.9% from
rectclassification
based on n-foldcrossvalidationwere reducednearestinvaded-neighbor
94% forspinywater fleas(Cohen's K = 0.6, P < 0.001), 17.6 km to 13.4 km (meanchange ? SE = 4.2 ? 1.2 km;
86% forrainbowsmelt (K = 0.655, P < 0.001), 86% for t95= 3.4; P = 0.001; Figure3b) and increasedthenumber
zebramussels (K = 0.418, P < 0.05), 81% forEurasian ofvulnerablelakesfrom87 to95 (a 9.2% increase).
watermilfoil(K = 0.603, P < 0.001), and 65% forrusty
crayfish(K = 0.302, P < 0.05). Models for individual
Discussion
invadersincludedexplanatoryvariablesbroadlyconsis
tentwith previousresearchon thesespeciesor aquatic A centralchallengeof invasionbiology is tounderstand
how invasive species interactwith other large-scale
invaders
generally(Table 1;WebPanel 1). For zebramus
orwatershed agentsofenvironmental
change (Didham etal. 2007). Of
sels alone, inclusionof eitherconductivity
sta paramountimportanceto thistask is learninghow these
area as predictorvariableseliminatedimpoundment
driversare likelytochangeand interactin
tusfromthebest-fit
model (Table 1). Conductivity,
par environmental
Our find
as itpredictstheconcentration
ticularly
of calcium ions, shapingfutureratesand patternsof invasions.
constructionand theconver
ingssuggestthatreservoir
can limitzebramussel shellformation
and, therefore
pop
riversto standingwatersmay ulti
For water bodieswith dissolved sion of free-flowing
ulation establishment.
calciumconcentrations
and conductivity
measurements, mately facilitatethespreadof invasivespeciesacross the
thesevariableswere strongly
landscape.Although aquatic invasionshave previously
positivelycorrelated(r =
been linkedto impoundments
(egMoyle andLight 1996;
0.80; n = 168; P < 0.001).
and historicalland Kolar and Lodge 2000), the driversof thisassociation
Comparisonsbetweenpresent-day
and
Most studiesof reservoirs
scape scenarios (ie with and without impoundments,have remainedambiguous.
have occurredin areaswith fewnatural
respectively)
revealedthat,forzebramussels,thepresence aquatic invaders
of impoundments
reducedmean distance to thenearest lakes,have focusedon lotic (runningwater) environ
introduced
game
invadedwater body by 45%, from84.2 km to 46.4 km ments,or have examined intentionally
(mean change ? SE = 37.7 ? 3.1 km; tI,4= 12.1, species, leaving open the possibilitythat any lentic
P < 0.0001; Figure3a). Based on thedistancetraveledby (standing
per
water)habitat- ratherthanimpoundments
90% of registered
Wisconsin boatersusing trailers,this se - would have producedan identicalincreasein inva
increasedthenumberof uninvadednaturallakesconsid sion risk.Here, we overcome previous limitationsby
? The EcologicalSocietyofAmerica
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
PTJJohnsonetal.
and freshwater
invasions
Impoundments
Table 1. Best-fIt logistic regression models
Model variables
foreach freshwater Invasive species, as determined by AIC
Eurasianwaterrnilfoil Zebra mussel
fN= O.52
,N-=0.58
n = 578
n = 306
Impoundmentstatus
0.73 i 0.29*
(2.07)
Number of boat landings
0.29 ? 0.09"
(1.342)
0.20 ? 0.08*
(1.218)
-1.37 ? 0.59*
Distance toGreat Lakes
(0.255)
Watershed area
Maximum depth
4.36 ? 0.40*
(78.1)
Surfacearea
Rustycayfish
N.= 0.19
n 408
5.70 i 2.57
2.58 ? 0.96'
0.74
(298.9)
(13.21)
1.54 ? 0.55w
(0.012)
(0.826)
-5.23 ? 3.22
(0.005)
12.73 ? 6.04*
1.73? 0.65
(21.39)
(336614)
(5.617)
2.23 ? 0.87
-6.52 ? 3.92
(0.001)
11.93? 3.03w
(151669)
5.50 ? 0.94**
(244.92)
-1.07 ? 0.28
-2.76 ? 0.927
(0.003)
-1.16 ? 0.34*
-6.45 ?
I.0'*
(0.002)
(6.295)
(1.637)
0.49 ? 0.22*
(0.315)
Constant
1.84 ? 0.5r
0.49 ? 0.22
(0.345)
Hydrology
-0.19 ? 0.06w
(4.644)
-4.39 ? 1.55*
00.26"
(2.1)
(2.307)
(9.314)
Conductance
Rainbowsmelt
rN= 0.16
n = 82
0.84 ? 0.28
3.06 ? 1.27
Secchi depth
water flea
Spiny
0N= 0.78
n = 120
(1.637)
- 15.81? 4.38w
(0.00001)
6.44 ? 6.94
(624)
10.21 ? 16.0
- 11.75? 3.0#
(27121)
(.0001)
Notes: Listed in the firstrow are each invader;theNagelkerke r value for the best model, and the total sample size ofwater bodies. In the firstcolumn are the indepe
variables included ineach analysis;all continuous variableswere logd-ransfofmed.Provided in each subsequent column are themaximum likelihoodparameter estimates
? I SE and the odds ratio (inparent
) foreach independentvariable in the finalmodel. A blank cell indicates thata given variablewas not selected in the finalmodel.
=Wald chi-squared P < 0.05;
Wald chi-squaredP < 0.005.
quantitatively
analyzingspatialpatternsof invasionsfora were weighted towardaccessiblewater bodies, notably
diverseassemblageof species in a region underrepresenting
taxonomically
thethousands
of lessaccessiblenatural
richwith impoundments
and naturallakes.
lakesin thisregion,
we expect thatthereportedinvasion
Consistentwith the hypothesisthat impoundments bias in favorof impoundments
isa considerableunderes
facilitatefreshwater
statuswas a
invasions,impoundment
timate;inaccessiblelakesare less likelyto be visitedby
strongpredictorof non-indigenousspecies'occurrences. humansand, therefore,
tobe invaded.
For each of the fiveinvaders,impoundments
were 2.5 to
Despite inclusionofnumerousanthropogenic
and envi
7.8 timesmore likelythannatural lakes to have estab
ronmental
variableshypothesizedtoaffecttheprobability
lishedpopulations,and thesepatterns
were robusttovari of invader introductionand establishment,impound
ation in thedefinition
of impoundment
(seeWebPanel 1). ment statusremaineda significant
predictorof occur
Among thesubsetofwaterbodies surveyedforthe three rence forfourof the five invaders(Table 1). In several
most common invaders(zebramussels,Eurasianwater cases, inclusion of additional explanatory variables
milfoil,and rustycrayfish),impoundments
were also sig enhanced the strengthof the impoundmenteffect,as
nificantly
more likelythannaturallakestosupport
multi estimatedby theodds ratio(up to300 timesovernatural
ple invaders.
Considering thatcurrentsamplingefforts lakes).Models forindividualinvadersincludeda variety
? TheEcological
Society
America
of
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
www.frontiersinecology.org
Impoundments
and freshwater
invasions
PTJJohnsonetal.
(a) Zebra mussel
Present
40
0
0
0
L
Historical
Historical
8
landscape(laes o~n
landscape
~~~~~~~~~~Prsn-Paday
-
20
0(A
.0
1
(takesesenmpoundments
0
0
50
150
100
200
(b)Eurasian watermilfoil
50
Present Historical
Historical
landscape wakes only)
ladcape
Prsnt-day
nearest
invadelatebodyunderthe
eakes
+ impoundments)
40
.0
0 30
o 20
0
theyoungage, increasedniche availabil
ity,and high disturbanceregimecharac
Natural
teristicofmost impoundments.
lakesin theGreat Lakes regionareat least
10 000 yearsold and formed
duringglacial
retreatin the Pleistocene,whereas the
oldest impoundmentin our datasetwas
161 yearsold (median= 68 years),indi
have had
cating that thesecommunities
lesstimetoassemble.
substantially
Newly
assemblednative communities in im
poundments
may exhibitcorrespondingly
lowerbiotic resistance,thereby
making
themparticularly
vulnerable to species
invasions(Levine and D'Antonio 1999;
Kolar andLodge 2000;Shea andChesson
2002;Havel et al. 2005). Impoundments
arealsomoredisturbedthannaturallakes,
oftenexhibiting
marked fluctuationsin
water levels,temperature,
fishstocking,
and nutrientcontent (Thornton et al.
1990) - conditionsthatshould increase
invasibility
(egDavis etal. 2000). Broadly
invasivespeciesmay alsohave
distributed
become adapted to impoundmentsin
otherpartsof theirnativeor non-native
theirsuccessin
ranges,further
facilitating
North American impoundments.
0
120
40
60
80
Distance to nearest infested
water bodly (kin)
Figure 3. Comparison of the distance between uninvaded natural lakes and the
nearestwater body invadedby (a) zebramussels and (b) Eurasian waternilfoil under
two scenarios: present-day landscapewith lakesand impoundments(top stackedbars)
and historical landscape with lakes and no impoundments(bottom stacked bars).
Dashed lines indicate themean distance between uninvaded natural lakes and the
nearest invadedwater body under thetwo scenarios; shaded regionreflectstheaverage
inter-lakedistance traveledby boaters in thestudyregion.
However,we cannotexcludethepossibil
differin
itythatlakesand impoundments
invaderpropagulepressurebeyondwhat
we showed in our analysis.Despite the
ofwaterbodyareaand
combinedstrength
numberof boat landingsin predicting
waterbodypopularity(seeWebPanel 1),
additional differencesin boat landing
quality,visitationrates,or typeof boater
could generatedifferencesin invasion
risk.
An additionalchallengebeyondunder
standingthefactors
drivingthe impound
its
ment-invasion linkage is identifying
lake
consequencesfornatural
ecosystems.
to increase
on We estimatedthepotentialforimpoundments
ofpredictors
broadlyconsistent
with previousresearch
these species.The numberof boat landingsand/orthe the invasionriskof natural lakesby comparingthe dis
proximity
of awaterbody to thenearestGreat Lake posi
tancesbetweeneach uninvadednaturallakeand itsnearest
tivelypredicted the occurrenceof spinywater fleas, invadedneighborunder two scenarios:a contemporary
with impoundments
and a historicallandscape
Eurasianwatermilfoil,
rainbowsmelt,and zebramussels, landscape
highlightingthe importance
of human boatingactivity devoid of impoundments.
We foundthat impoundments
and distanceto invadersourcepopulation(egMacdsaac et reducedthemean distancebetweenan uninvadedlakeand
al. 2004; Leung etal. 2006). The importance
neighborbyhalf,increas
ofwatershed itsnearestzebramussel-invaded
area forboth zebramussels and rustycrayfish
highlyvulnera
probably ingthenumberofnaturallakesconsidered
reflectedincreasedcolonizationopportunitiesthrough ble to invasionby almost50%. For themore established
increasedthenum
impoundments
upstreamlakeor riverconnections(eg Puth andAllen Eurasianwatermilfoil,
2005;Havel andMedley 2006).
berofhighlyvulnerablelakesbyabout 10%.This finding
We suggest that the strong association between suggeststhat the facilitativerole of impoundmentsin
impoundments
and non-indigenousspecies resultsfrom invasionmay attenuateas the landscapebecomes satu
www.frontiersinecology.org
a
The Ecological
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
Society of America
and freshwater
invasions
Impoundments
PTJJohnsonetal.
effects of habitat
modification
invasion
and
on native
species
rated
with invadedwaterbodies.These resultsalso suggest
speciesdecline. TrendsEcol Evol 22: 489-96. Ijlj
increasetheriskof invasionintonat
thatimpoundments
Downing JA,PrairieYT, Cole JJ,etal 2006 The global abundance
HB
distanceand by
ural lakesby both decreasinginter-lake
size distribution
and
of lakes, ponds,
and
impoundments.
LimnolOceanogr 51: 2388-97.
increasingthe totalnumberof invadedwater bodies on
et al 2006. Freshwater
D, Arthington
AH, Gessner MO,
Dudgeon
the landscape.
chal
threats, status and conservation
importance,
biodiversity:
which ecosystems
arevulnerableto invasions
Predicting
lenges. Biol Rev 81: 163-82.
isan important
goal of invasionbiology,and identificationGraf WL. 1999. Dam nation: a geographic census of American dams
thatwill notonlybecome invadedbutwill
ofenvironments
and their large-scale hydrologie
impacts. Water Resour Res 35:
1305-11.
contribute
to secondaryspreadof inva
disproportionately
and cost-effectiveHavel JE, Lee CE, and Vander Zanden MJ. 2005. Do reservoirs
sivespeciesoffers
thepromiseof targeted
invasions
into landscapes?
BioScience
facilitate
55: 518-25.
management(Hulme2006).We arguethatimpoundmentsHavel
KA.
invasions across spatial
2006. Biological
JE and Medley
invaders
may functionas invasion"hubs" forfreshwater
scales:
of clado
intercontinental,
regional and local dispersal
ceran Zooplankton.
theirsubse
(MuirheadandMacIsaac 2005), facilitating
Biol Invasions 8: 459-73.
intonaturalwaterbodies. Holeck KT, Mills EL, Maclsaac HJ, et al 2004. Bridging troubled
quent spreadand establishment
waters:
links between
invasions,
biological
understanding
are now a ubiquitousfeature
of theglobal
Impoundments
in the
transoceanic
and
other
entry vectors
shipping,
hydrologic
system(Smithetal. 2002;Downing etal. 2006),
Laurentian
Great Lakes. BioScience
54: 919-29.
and vast regions
where lakeswere formerly
rareare now Hulme PE. 2006. Beyond control: wider implications for the man
while otherregions
home to hundredsof impoundments,
agementof biological invasions.JAppl Ecol 43: 835-47.
dominatedby natural lakesnow also include Kolar CS and Lodge DM. 2000. Freshwater nonindigenous
historically
species:
interactions with other global changes.
In: Mooney
HA
and
numerous impoundments.
climate-induced
Furthermore,
in a changing
Invasive
Hobbs
world.
(Eds).
RJ
species
and increasing
humandemand
changestowateravailability
DC:
Island Press.
Washington,
ofnew reser Leung B, Bossenbroek JM, and Lodge DM. 2006. Boats, pathways,
for
waterare likelytoprompttheconstruction
voirsto increase
water suppliesinmany regions(Palmeret
invasions: estimating dispersal potential
and aquatic biological
of contemporary with gravity models. Biol Invasions 8: 241-54.
al. 2008). The widespreaddistribution
impoundments
and theongoingcreationofnew impound Levine JM and D'Antonio CM. 1999. Elton revisited: a review of
evidence
linking diversity and invasibility. Oikos 87: 15-26.
ments could provideenhancedopportunities
forinvasive Maclsaac
PA. 2004.
HJ, Borberly JVM, Muirhead
JR, and Graniero
speciesto establishinnaturallakesand spreadacrossthe
invasions
and forecasting
of inland
Backcasting
biological
landscape.
lakes.Ecol Appl 14: 773-83.
1996. Biological invasions of freshwater:
Moyle PB and LightT
0 Acknowledgements
rules and assembly
empirical
theory. Biol Conserv
78:
149-61.
Muirhead JRandMaclsaac HJ. 2005. Development of inland lakes
The authorsgratefully
acknowledgethe data contribu
tionsof JMaxted, K Webster,P Soranno,L Herman,R
Martin, T Mojo, D Balsiger,K Grande, T Asplund, D
Olson, JFilbert,L Joppa,and S Knight.The following
Wisconsin
agencies generously shared information:
DepartmentofNatural Resources (WDNR), Michigan
Department of Environmental Quality, the North
and
TemperateLakes LTER andBiocomplexityprograms,
theGreat Lakes Indian Fish andWildlife Commission.
S Carpenter, JHavel, D Strayer,H MacIsaac, and E
Stanleyprovidedfeedbackhelpfulin shapingthemanu
script.This project was funded by grants from the
WDNR, theWisconsin Coastal Management Program,
and theNational Science Foundation (DEB-0411760,
DEB-0217533, andDEB-0083545).
in an invasion
as hubs
Nilsson
C,
Reidy
Fragmentation
systems. Science
network.
] Appl
CA,
M,
Dynesius
and flow regulation
308:
80-90.
Ecol 42:
and
Revenga
of the world's
change
Front Ecol Environ
options.
of regional
Homogenization
river
2008.
Climate
management
6: 81-89.
JD, Merritt DM,
Poff NL, Olden
2005.
405-08.
CA, Nilsson
C, et al
Reidy Liermann
river basins: anticipating
and the world's
Palmer MA,
C.
large
and Pepin DM.
river dynamics
by dams
2007.
and global
biodiversityimplications.P Nati Acad SeiUSA 104: 5732-37.
LM and Allen
TFH.
2005. Potential
corridors for the rusty
USA
lakes:
rusticus, in northern Wisconsin
crayfish, Orconectes
lessons for exotic invasions. Landscape
Ecol 20: 567-77.
Rahel
of freshwater faunas. Ann Rev
FJ. 2002. Homogenization
Puth
Ecol Syst33: 291-315.
A
Ricciardi
and Rasmussen
American
K
Shea
freshwater
and Chesson
framework
JB. 1999.
fauna. Conserv
P. 2002.
for biological
Extinction
Biol
13:
rates of North
1220-22.
theory
Community
ecology
invasions.
Trends
Evol
Ecol
as a
17:
170-76.
M References
Buchan LAJ and Padilla DK.
long-distance
Davis
overland
Ecol Appl 9: 254-65.
Grime
MA,
resources
in plant
1999. Estimating the probabilityof
dispersal
of
invading
aquatic
species.
K.
2000.
JP, and Thompson
Fluctuating
a general theory of invasibility.
communities:
] Ecol 88: 528-34.
Didham RK, Tylianakis JM,Gemmell NJ, et al 2001. Interactive
Smith SV, RenwickWH, Bartley JD, and Buddemeir RD. 2002.
of small, artificial water bodies
significance
States landscape.
Sei Tot Environ 299: 21-36.
Thornton KW, Kimmel BL, and Payne FE. 1990. Reservoir
limnology:
and Sons.
ecological perspectives. New York, NY: JohnWiley
Distribution
across
USGS
and
the United
(US Geological Survey). 2007. Nonindigenous Aquatic
Database.
Gainesville,
Viewed
http://nas.er.usgs.gov.
Species
FL:
18 Dec
C The EcologicalSocietyofAmerica
This content downloaded from 158.135.136.72 on Wed, 8 Oct 2014 16:50:55 PM
All use subject to JSTOR Terms and Conditions
US
2007.
Geological
Survey.
Hfl