Habitat degradation modifies spider diets and carbon flux
in riparian environments
Jamie-Lee Hunt
Co-authors: Neil Pettit, Harriet Paterson & Paul Close
Outline
Honours research thesis (2018)
Southwest WA, in the region surrounding Albany
Biodiversity hotspot
Multiple land use types:• Primary production• Tourism• Remnant bushland • National parks
ALBANY
Riparian Spiders
Abundant terrestrial predators
Important prey source
Understudied in Australia
Inform ecosystem function
Important link between aquatic and terrestrial food
webs
? ? ?
Research Questions
? ? ?
1. Are spider community dynamics affected by loss of habitat in the riparian zone?
2. Do riparian spiders feed more from aquatic or terrestrial food webs?
Orb Weavers • Orb Weavers (Araneidae)• Long-jawed Orb Weavers
(Tetragnathidae)
Ambush Hunters• Crab Spiders (Thomisidae)• Sac Spiders (Clubionidae)
Cursorial Hunters• Fishing Spiders (Pisauridae)• Wolf Spiders (Lycosidae)
Space Weavers• House Spiders (Desidae)
• Comb-footed Spiders (Theridiidae)
• Money Spiders (Linyphiididae)*
Family Guild No. Morphospecies
No. spiders surveyed
% spiders surveyed
Araneidae Orb Weaver 20 160 38.65
Tetragnathidae Orb Weaver 3 183 44.20
Desidae Space Weaver 1 1 0.24
Linyphiidae Space Weaver 1 2 0.48
Theriididae Space Weaver 3 23 5.56
Clubionidiae Ambush Hunter 3 7 1.69
Thomisidae Ambush Hunter 3 4 0.97
Lycosidae Cursorial Hunter 7 13 3.14
Pisauridae Cursorial Hunter 4 21 5.07
Totals - 45 414 100
Summary of spider survey results
-0.5 0.0 0.5 1.0 1.5 2.0
-0.5
0.0
0.5
1.0
MDS1
MD
S2 GD1
GD2GD3
GD4
GD5
GD6
KA1
KA2
KA3KA4
KI1
KI2
KI3
KI4
KI5MA1
MA2YA1
YA2
YA3
YA4
A - Pristine
B - Slightly Disturbed
C - Some canopy, liimited erosion
D - No canopy, severe erosion
Spider community data mMDS
Riparian condition does not affect spider abundance
A B C D
510
15
20
25
30
35
ORB WEAVERS
Penn-Scott condition grade
Orb
weaver
abundance
A B C D
0.0
0.5
1.0
1.5
2.0
AMBUSH HUNTERS
Penn-Scott condition grade
Am
bush h
unte
r abundance
A B C D
01
23
4
CURSIORIAL HUNTERS
Penn-Scott condition grade
Curs
orial h
unte
r abundance
A B C D
01
23
45
SPACE WEAVERS
Penn-Scott condition grade
Space w
eaver
abundance
Morphospecies richness (p=0.72) and Shannon-Weiner diversity (p=0.67) were also unaffected by condition.
ORB WEAVERS (n=343) AMBUSH HUNTERS (n=11) CURSORIAL HUNTERS (n=34) SPACE WEAVERS (n=26)
Penn-Scott condition grade Penn-Scott condition gradePenn-Scott condition gradePenn-Scott condition grade
Orb
wea
ver
abu
nd
ance
Spac
e w
eave
r ab
un
dan
ce
Cu
rso
rial
hu
nte
r ab
un
dan
ce
Am
bu
sh h
un
ter
abu
nd
ance
Exploring ‘C’ grade habitats
A B C D
51
01
52
02
53
03
5
ORB WEAVERS
Penn-Scott condition grade
Orb
we
ave
r a
bu
nd
an
ce
p<0.01Low Cover (<9%) Mid Cover (10-49%) Dense Cover (>50%)
51
01
52
02
53
03
5
Understorey Coverage
Orb
We
ave
r a
bu
nd
an
ce
Sparse Canopy (<9%) Mid Canopy (10-49%) Dense Canopy (>50%)
51
01
52
02
53
03
5Canopy Coverage
Orb
We
ave
r a
bu
nd
an
ce
Understorey: test results
ANOVA p<0.01Mid v Dense (p<0.01)Low v Dense (p=0.12)
Mid v Low (p=0.26)
ORB WEAVERS (n=343)
Penn-Scott condition grade
Orb
wea
ver
abu
nd
ance
Canopy:marginal p-value
ANOVA p=0.07
Orb
wea
ver
abu
nd
ance
Orb
wea
ver
abu
nd
ance
Canopy Coverage
Understorey Coverage
Sparse(>10%) Mid(10-49%) Dense(>49%)
Sparse(>10%) Mid(10-49%) Dense(>49%)
? ? ?
Research Questions
? ? ?
1. Are spider community dynamics affected by the condition of the riparian zone?
2. Do riparian spiders feed more from aquatic or terrestrial food webs?
Spiders in degraded habitat ate more terrestrially derived prey
Pristine Degraded
-34-33-32-31-30-29-28-27-26-25
δ13C [‰ VPDB]
Degraded
Pristine
Orb weavers
Cursorial hunters
Orb weavers
Cursorial hunters
? ? ?
Research Questions
? ? ?
1. Are spider community dynamics affected by the condition of the riparian zone?
2. Do riparian spiders feed more from aquatic or terrestrial food webs?
Sure is!Yum!
Conclusions
• Spider communities are not affected by riparian condition
• Diet becomes more terrestrial in degraded sites
• Habitat loss impairs ecological processes of carbon flow & nutrient cycling
• Foundation for future research into spider communities
Implications for
management
• Informs structural aspects of stream restoration
• Results provide another line of evidence to support riparian restoration & revegetation projects
• Spiders are not a useful indicator species to show riparian condition
Acknowledgements:
Ben Ford
Steve Janicke
Maddi Howard
Kyle Townsend
Kahree Garnaut
Susie Cramp
Sharon Rost
Ela Skrzypek
Greg Skrzypek
Kate Bowler
Doug Ford
Edith Easthope Scholarship
GSDC NRM Sustainability Research Scholarship
Property OwnersSonja Johnson ~ Graeme Pile
Peter Gilmour ~ Rebecca
Conclusions &
Implications
• Spider communities are not affected by riparian condition
• Diet becomes more terrestrial in degraded sites
• Implications for stream restoration
• Foundation for future research into spider communities
Degraded habitats diversify diet
Araneidae
Lycosidae
Pisauridae
Tetragnathids
BiofilmAlgae
Kikuyu
Fish
2nd Order Aq. Inverts
1st Order Aq. Inverts
1st Order Terr. Inverts
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
-47.00 -42.00 -37.00 -32.00 -27.00 -22.00 -17.00 -12.00
δ1
5N
[‰ A
IR]
δ13C [‰ VPDB]
Pristine Sites (Penn-Scott Grade = A)
Degraded habitats diversify diet
Araneidae
Fish
AlgaeBiofilm
Kikuyu
1st Order Aq. Inverts
2nd Order Aq. Inverts
1st Order Terr. Inverts
Lycosidae
Pisauridae
Tetragnathids
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
-47.00 -42.00 -37.00 -32.00 -27.00 -22.00 -17.00 -12.00
δ1
5N
[‰ A
IR]
δ13C [‰ VPDB]
Degraded Sites(Penn-Scott Grade = C & D)