Long term dynamics of macro-

invertebrate biological traits with

climate change.

Alexander M. Milner, Anne E. Robertson & Lee E. Brown

Dyurgerov & Meier, 2005 - PNAS

Most regions of the world have

seen decreases in glacial mass over

the last 50-60 years

Along the Gulf of Alaska, retreat

has been particularly extensive

and rapid

Here, ice sheet/glacier retreat

dates back to ~1750 (LIA)

Glacier retreat

Over 130 km spatial scale we have a 230

year temporal scale

1892

Glacial river ecosystems

Glacier-fed rivers are cold, unstable

habitats typically dominated by

Chironomidae

But... Wolf Point Creek (Alaska) studied

annually since 1978 ice sheet has

disappeared, new stream has formed and

floodplain vegetated

Glacial stream ecosystem studies mainly

adopt space-for-time substitutes

1972

1993

Catchment glacial cover – 70-0% in 28 years

Significant water temperature increase

Significant turbidity (suspended sediment) decrease

Macroinvertebrate succession

Progressive community change linked to deglacierization

0% 100% Percent Glacierization

The identity, abundance and range of species traits appears to be considerably more important than species number in determining the effects of ‘biodiversity’ on many ecosystem functioning (Diaz & Cabido. 2001. TRENDS Ecol & Evol)

How does functional (trait) diversity change following deglacierization?

Trait dynamics and functional diversity

Trait database of Poff et al. 2006 – J. N. Am. Benthol. Soc.) -20 traits, 61 modalities - four groups of traits: life history, mobility, morphology and ecology - binary coding - mostly genus level designations

Trait dynamics and functional diversity

Trait dynamics and functional diversity

Over 130 km spatial scale we have a 230

year temporal scale

1892

0

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None

Weak

Strong

Longer-term

changes

Space for time

throughout

Glacier Bay

35 to 220 years

of development Swimming ability

Adult dispersal

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Large

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Cold/cool

Cool/warm

Warm

Body Size

Thermal preference

Concept of filters

determining

community

structure at

different degrees

of glacierization 75% glacierization

0% glacierization

SUMMARY

Significant increase in functional diversity over 30 years in

Wolf Point Creek but then a levelling off despite continued

increase in taxonomic richness – functional redundancy

although taxa richness has increased?

Significant reductions in cold stenotherms, insects with

long dispersal distance and collector gathers over time in

Wolf Point Creek. No significant change in body size over

the 30 year period.

Over the longer 200 year term some increases in body

size and increases in low dispersal distance and strong

swimming ability.

Even though the taxa in stream communities shift with

climate change, the functioning within the community

may remain the same.

Acknowledgements

Elizabeth Flory

Kieran Monaghan

Ian Phillips

Amanda Veal

Mike McDermott

US National Park

Service.