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Microhabitat association of Plethodontidsalamanders in stream ecosystems along a
riparian land-cover gradient
Thilina Surasinghe & Robert Baldwin
School of Agricultural, Forest & Environmental Sciences,
Clemson University, SC
IntroductionWhat affects habitat associations?
Climate
Habitat availability & heterogeneity
Resource distribution
Natural disturbances
Anthropogenic disturbances
What about community interactions?
Predation
Intraspecific competition
Interspecific competition
• Exploitative competition
• Interference competition
• Apparent competition
Experimental Species Desmognathus quadramaculatus Black-bellied salamander (BB) Large bodied (SVL:80mm) Dominant Aquatic Disturbance sensitive
Desmognathus fuscus Northern Dusky salamander (ND) Small bodied (SVL:50mm) Subordinate Aquatic/semi-aquatic Disturbance adaptive
Objectives
Do human induced disturbances in the riparian zone provide competitive advantage for certain species of stream salamanders?
Are Black-bellied salamanders competitively dominant over Northern dusky salamanders in forested streams?
Experimental Setup
Artificial streams simulate four land-use types with replications: forested, agricultural, residential, urban + stock tanks
Artificial streams filled with stream substrate materials and water sand, sediment, rocks, gravel, and
woody debris
Substrate thickness: 4-5 cm in wetted channel; 15 cm in banks
Water depth: 8-10 cm
Air pumps maintain DO in field-equivalent conditions
Experimental Procedure
Capture animals from the wild
Acclimatize
Individuals of same SVL class (40-50 mm for D. fuscus; 80-90 mm for D. quadramaculatus)
3 phases in each replication
1. Both species introduced
2. Remove one species
3. Reintroduce removed species & remove the one retained
Each LU type replicated in the same tank, with introduction of different individuals of each species
Make observations in each phase
Making Observations
Daily, 20-min observations in every two hours (0900-0100 hrs)
Aggression
Use of microhabitats
All Animal sampling
Percent occurrence of a species at a given microhabitat type in a certain phase
Results & Conclusion – Forested streams
D. quadramaculatus microhabitat selection
Occupied bank crevices 96% and 94% of times in coexistence and isolation, respectively
D. fuscus microhabitat selection
Occupied channel bottom 100% of times in coexistence
Occupied bank crevices 65% of times under isolation
0
20
40
60
80
100
120
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
Perce
ntage
Occu
rrenc
e
Microhabitat Types
Forested Riparian Land-Use
BB with ND
ND with BB
BB only
ND only
Results & Conclusion – Agricultural streams
D. quadramaculatus microhabitat selection
Occupied bank crevices 89% and 88% of times in coexistence and isolation, respectively
D. fuscus microhabitat selection
Occupied channel bottom 95% of times in coexistence
Occupied bank crevices and interface 60% of times under isolation
0
10
20
30
40
50
60
70
80
90
100
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
Perce
ntage
Occu
rrenc
e
Microhabitat Types
Agricultural Riparian Land-Use
BB with ND
ND with BB
BB only
ND only
Results & Conclusion – Residential streams
D. quadramaculatus microhabitat selection
Occupied bank crevices 52% and 88% of times in coexistence and isolation, respectively
D. fuscus microhabitat selection
Occupied channel bottom 88% of times in coexistence
Occupied bank crevices and interface 56% of times under isolation
0
10
20
30
40
50
60
70
80
90
100
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
Perce
ntag
e Occ
urre
nce
Microhabitat Types
Residential Riparain Land-Use Type
BB with ND
ND with BB
BB only
ND only
Results & Conclusion – Urban streams
D. quadramaculatus microhabitat selection
Occupied bank crevices 25% and 88% of times in coexistence and isolation, respectively
D. fuscus microhabitat selection
Occupied bank-channel interface 70% of times in coexistence
Occupied bank crevices 76% of times under isolation
0
10
20
30
40
50
60
70
80
90
100
Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface
Perce
ntag
e Occ
urre
nce
Microhabitat Types
Urban Riparian Land-UseBB with ND
ND with BB
BB only
ND only
D. quadramaculatus
Occupied stream banks and chose rock crevices as their preferred microhabitat in each land-use simulation
Showed high site fidelity at each land-use simulation
Strong domination of microhabitat selectivity over D. fuscus in forested streams
Weak domination of microhabitat selectivity over D. fuscus in non-forested streams
Some reduction in use of bank crevices in non-forest streams
General Conclusions
General Conclusions
D. fuscus
Exclusively occupied the stream channel in the forested stream in coexistence
Marked increase in occupancy of bank crevices and interface in non-forest streams, which is prominent in the urban stream
Broad selectivity of interstitial spaces including beneath rocks and logs, leaf litter, sand and gravel
Low side fidelity
No aggression or predation was observed
D. quadramaculatus competitively displaced D. fuscus in forested
streams
D. fuscus shifted to the microhabitats previously occupied by D.
quadramaculatus once the later was experimentally removed
Marked change in the microhabitat selectivity of D. fuscus with
increasing disturbances in the riparian zone
The study is still continuing and more replications will be done
General Conclusions
Funded by….
Creative Inquiry Program
Numerous undergraduates in Dept. of Biological Sciences and School of Agricultural, Forest & Environmental Sciences
Dr. Mark Scott and SC stream bio-Assessment team, SC Dept. of Natural Resources
Dr. Bryan Brown, Dept. of Biological Sciences, Virginia Tech University
Dr. Michael Childress, Dept. of Biological Sciences, Clemson University
Acknowledgement