Benthic vs. Planktivorous Threespine Stickleback Fish
(Gasterosteus aculeatus)
Peter J. Park
Dept. of Biology and Chemistry
Nyack College
June 22, 2012
Learning Objectives
1. To introduce a “supermodel”2. To turn shapes into numbers3. To provide and instructional walk-through of
shape analysis software (free software!)4. To minimize the math (but not without
providing references)5. To teach concepts in ecology and evolution
using a single species6. To encourage fun applications
• 3 forms: marine, sea-run, freshwater.
• freshwater populations were founded by sea-run stickleback.
• occur along coastal waters of the northern hemisphere.
• Sea-run stickleback colonized a vast array postglacial lakes. (In southcentral Alaska, lakes are less than 20,000 years old. )
• derived lake populations: natural, replicated recently derived experiments
•contemporary sea-run populations: can be used to infer ancestral condition
Gasterosteus aculeatus
species complex
The Model
Ecology
Independently-derived freshwater populations
Living representatives of sea run fish are analogs of the ancestor
Evolution
Ultimate (past) mechanisms
Proximate (present) mechanisms
Stickleback: at the interface of ecology then and now
• Migratory, breeding sea-run fish can get into lakes.• If lake then becomes land-locked, then a derived
freshwater population is borne, founded by these sea-run fish.
• Along opposite ends of a continuum of lake types are shallow lakes and deep lakes.
• In these lakes, anatomical changes in fish from derived freshwater populations is driven by what they eat.
• Shallow lakes are dominated by large benthic invertebrates benthic stickleback
• Deep lakes do not have benthic invertebrates, making smaller plankton the predominant food source planktivore stickleback
Benthic-Planktivore Ecological Dichotomy
Sea-Run Ancestor
*
The Model
Shallow Lake
structurally complex
benthic invertebrates
Deep Lake
structurally simple
plankton
Protocol
• subjects: field-caught 1-year-old juveniles • motivation: food deprivation for 24-36hrs • 2 trials per day• 50 trial maximum
Collection of subjects
collection method: Gee minnow traps set overnight
Planktivores (Limnetics)
Benthics
(Lavin and McPhail 1985, 1986; Walker 1997; Aguirre 2007 )
Benthic invertebrates
Small Eyes
Short Snout
Deep-bodied
Forages on benthos
Plankton
Large Eyes
Long Snout
Streamlined
Forages in open water
The ModelAdaptation is driven by prey
specialization
Specialize on:
Detecting prey:
Handling prey:
Maneuvering:
Foraging behavior:
Pelagic Fish
- elongate, slender
- poor at turning
- ram or filter feeding
Bottom-dwelling Fish
- stout, deep-bodied
- highly maneuverable
- suction feeding, grazing
Sheepshead
Rockfish
Sheephead
Barracuda
Mackerel
Swordfish
ACKNOWLEDGEMENTSMichael A. BellWindsor E. AguirreJoan M. MiyazakiDeborah A. SpikesMichael P. KroessigMarvin H. O’Neal IIIKathleen NolanDarrel R. Falk
ABLE Nyack College Stony Brook University