background as number of species varies with volume (taylor, 1997, and others), how is assemblage...
TRANSCRIPT
Background• As number of species varies with volume
(Taylor, 1997, and others), how is assemblage stability affected when isolated pools shrink during summer?
• Across years and seasons, extinction rates of fish assemblages are related positively to flow variation; immigration rates are greatest downstream (Taylor and Warren, 2001). Are patterns of extinction and immigration rates within a season (i.e., at smaller scales) similar to those at larger scales?
Lak e W ino na
Alu m Fo rk
Mid dl e F or k
Bre ad C re ekNo rth A lum F or k
So uth A lum F or k
Ouachita Highlands, Alum Fork of Saline River
Stream Flow data for Alum Fork Saline River
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Str
eam
flow
(ft3
/s)
-50
0
50
100
150
200
250R
ainfall (mm
)
80
90
100
110
120
130
140
150
Stream flow (1990 - 2000) Rainfall (1931 - 1995) Stream flow (2002)
#
#
#
#
#
#
#
##
#
#
#
#
#
Bread Creek
North Alum Fork
South Alum Fork
Changes in Volumedark shade = greater changes
Objectives
• Characterize changes in stability of fish and aquatic insect assemblages from intermittent streams during summer dry-down
• Estimate site-specific immigration and extinction rates to investigate why these processes differ across sites
Methods• Fishes sampled for 48 hours with metal Gee minnow traps and a plastic floating minnow trap; once a month, June – Sept
Methods• Aquatic invertebrates: Hester-Dendy traps and a d-frame sweep net (6, 10 second passes along edge of pools); once a month, July - Sept
Environmental variables recorded between 10 am and 2 pm (pool size, temperature, DO, chlorophyll a, conductivity, pH, turbidity)
Stability of Fish AssemblagesJaccard’s measure of stability from presence-absenceR2 = 0.744; P < 0.01Variable Std. Coef. t-value P-valueDistance Upstream -0.61 -3.82 < 0.01Volume (c.v.) -0.46 -2.89 0.01
Bray-Curtis measure of stability from relative abundancesR2 = 0.906; P < 0.01Variable Std. Coef. t-value P-valueVolume (c.v.) 0.64 4.30 <0.01Dissolved Oxygen -0.48 -4.07 <0.01Chlorophyll -0.39 -3.20 0.01Temperature -0.51 -3.91 <0.01Specific Conductivity 0.36 2.13 0.07
coefficient of variation for volume
0 1
Sta
bilit
y
0.0
0.2
0.4
0.6
0.8Bray-Curtis; unbroken; r2 = 0.44; P = 0.01
Jaccard's; broken; r2 = 0.44; P = 0.02
Stability of Fish Assemblages
Distance Upstream (m)
0 2000 4000 6000 8000 10000 12000 14000 16000
Ass
embl
age
Sta
bilit
y
0.0
0.2
0.4
0.6
0.8
r2 = 0.66P < 0.05
Stability of Fish Assemblages
#
#
#
#
#
#
#
##
#
#
#
#
#
Bread Creek
North Alum Fork
South Alum Fork
dark shade = higher stability
Stability of Fish Assemblages
Stability of Aquatic Insect Assemblages
Bray-Curtis measure of stability from relative abundancesR2 = 0.927; P < 0.01Variable Std. Coef. t-value P-valueSpecific Conductivity (c.v.) 0.91 -10.22 <0.01Turbidity 0.75 8.27 <0.01Chlorophyll (c.v.) -0.98 6.83 <0.01
Jaccard’s measure of stability from presence-absence
Variables n.s.
Stability of Aquatic Insect Assemblages
coefficient of variation for specific conductivity
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
Ass
em
blag
e S
tab
ility
0.0
0.1
0.2
0.3
0.4
0.5
0.6
r2 = 0.39P < 0.05
Immigration-Extinction Rates
Fishes(p = 0.02)
Aquatic Insects(p = 0.06)
Immigration Rate Extinction Rate
Average probabilities of immigration and extinction calculated for each site following Taylor and Warren (2001)
0.44a 0.34b
0.40a 0.56b
Immigration-Extinction Rates:Fishes
Immigration R2 = 0.56; P = 0.01Variable Std. Coef. t-value P-valueDistance Upstream 0.44 2.19 0.05Chlorophyll 0.54 2.66 0.02
Extinction R2 = 0.58; P = 0.01Variable Std. Coef. t-value P-valueVolume (c.v.) 0.53 2.68 0.03Chlorophyll (c.v.) -0.48 -2.42 0.02
Distance upstream (m)
0 2000 4000 6000 8000 10000 12000 14000 16000
Pro
babi
lity
of im
mig
ratio
n (f
ishe
s)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Immigration-Extinction Rates: Fishes
Immigration-Extinction Rates: Fishes
coefficient of variation for volume
0 1
Pro
babi
lity
of e
xtin
ctio
n (f
ishe
s)
0.2
0.4
0.6
0.8
1.0
1.2
Immigration-Extinction Rates: Insects
Immigration
Variables n.s.; related mainly to life history?
Extinction R2 = 0.69; P = 0.01Variable Std. Coef. t-value P-valueDistance Upstream -0.54 -3.01 0.01Chlorophyll (c.v.) -0.72 -3.86 <0.01pH (c.v.) -0.34 -1.84 0.10
Paraleptophelibia spp.Jy
4A
u4S
e4 Jy5
Au5
Se5 Jy6
Au6
Se6 Jy9
Au9
Se9
Jy11
Au1
1S
e11
Jy12
Au1
2S
e12
Jy14
Au1
4S
e14
Jy15
Au1
5S
e15
Jy17
Au1
7S
e17
Jy18
Au1
8S
e18
Jy24
Au2
4S
e24
Log
Abu
ndan
ce
0
2
4
6
8
10
12
14
16
Immigration-Extinction Rates: Insects
Distance upstream (m)0 2000 4000 6000 8000 10000120001400016000
Pro
babi
lity
of e
xtin
ctio
n (in
sect
s)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Immigration-Extinction Rates: Insects
Summary• Fish assemblage stability is sensitive to changes in
habitat size, quality, and position • During summer, fish assemblage stability was
lowest and immigration, highest at upstream sites• Aquatic insect assemblage stability is sensitive to
changes in habitat quality, and changes in structure related to species-specific life histories
• Insect assemblage stability generally exhibited patterns different from those of fishes, and were less influenced by pool size or position
AcknowledgementsUS Forest Service
P. Raelynn DeatonMarceau RatardAndy Sanderson