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

Proximate vs. Ultimate Causation

• 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

Sea-run threespine stickleback

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

Threespine Stickleback Adaptive Radiation

Meet the ancestor

Benthic-Planktivore Ecological Dichotomy

Sea-Run Ancestor

*

The Model

Shallow Lake

structurally complex

benthic invertebrates

Deep Lake

structurally simple

plankton

Show videos of lakes

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

PAUSE

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:

(Walker 1997; Aguirre et al. 2009)

Body Shape

(33.85%)

(17

.02

% )

(Park & Aguirre unpub. data)

Body Shape

Allopatric Populations – divergent ecotypes occur in different lakes

BENTHICS

PLANKTIVORES

• Sympatric Populations – divergent ecotypes occur in the same lake

BENTHICS

BENTHICS

PLANKTIVORES

THE BIG PICTURE?

Dorsal Fin

Anal Fin

Pelvic Fin

Tail Fin

Scales

Jaw

Pectoral Fin

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