Surasinghe Baldwin Seec2012
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Surasinghe Baldwin Seec2012

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• Surasinghe, T. D. and Baldwin, R. F. (2012). Microhabitat association of Plethodontid salamanders in stream ecosystems along a riparian land-cover gradient. Southeastern Ecology and Evolution ...

• Surasinghe, T. D. and Baldwin, R. F. (2012). Microhabitat association of Plethodontid salamanders in stream ecosystems along a riparian land-cover gradient. Southeastern Ecology and Evolution Conference, Clemson University, Clemson, SC.

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Surasinghe Baldwin Seec2012 Surasinghe Baldwin Seec2012 Presentation Transcript

  • 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
  • IntroductionWhat 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 Are Black-bellied salamanders competitively dominant over Northern dusky salamanders in forested streams? Do human induced disturbances in the riparian zone provide competitive advantage for certain species of stream salamanders?
  • 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 samplingPercent occurrence of a species at a givenmicrohabitat type in a certain phase
  • Results & Conclusion – Forested streams 120 Forested Riparian Land-Use 100 BB with ND ND with BB 80 Percentage Occurrence BB only ND only 60 40 20 0 Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface Microhabitat Types 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
  • Results & Conclusion – Agricultural streams 100 Agricultural Riparian Land-Use 90 BB with ND 80 ND with BB 70 BB only Percentage Occurrence 60 ND only 50 40 30 20 10 0 Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface Microhabitat Types 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
  • Results & Conclusion – Residential streams 100 Residential Riparain Land-Use Type 90 80 BB with ND 70 ND with BB Percentage Occurrence 60 BB only 50 ND only 40 30 20 10 0 Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface Microhabitat Types 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
  • Results & Conclusion – Urban streams 100 Urban Riparian Land-Use BB with ND 90 80 ND with BB 70 BB only Percentage Occurrence 60 ND only 50 40 30 20 10 0 Bank Crevices Channel Bottom Channel-Bank Interface Bank Surface Microhabitat Types 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
  • General Conclusions 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 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
  • General Conclusions 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
  • Acknowledgement 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