Western Aleutian Plant Distribution:

Buldir Island as a Dispersal FilterMonte Daniel Garroutte and Stefanie M. Ickert-Bond

University of Alaska Museum of the North & Department of Biology and Wildlife

Near Islands

Rat Islands

Western Aleutian Islands

Buldir Island

Buldir Island, AK• 26 breeding species of seabirds• 3 million + individual birds• Aleutian Cackling Goose

Nutrient subsidy

Ocean Island

Nutrients

Seabird Islands are nutrient subsidized;When compared to fox-infested islands:• ~3-fold increase in graminoid biomass• ~10-fold decrease in low-lying shrub biomass (Croll

et. al., 2005)

Questions• What is driving the vegetation composition

on Buldir Island? – How does the vegetation differ in surface

nesting and burrowing seabird colonies?

Seabird Vegetation Disturbance

BurrowingSurface Nesting

ErosionSoil compaction

Root damageSeedling trampling

Increased soil litter Decreased soil litter

Seabird Vegetation Disturbance

Increasing homogenization: Decline of native woody and

herbaceous perennials

Introduction and expansion of annuals and colonizing plants

BurrowingSurface Nesting

Increased density

Surface nester plotsGlaucous-winged Gull:

“Loafing areas”5-7 plant species per plot- Changes with elevationAnnual Callitriche sp. collected in 2007, in loafing area

246m elev.

55m elev.

196m elev.

Burrow nester plotsLeach’s Storm PetrelsFork-tailed Storm PetrelsCassin’s AukletsAncient Murrelets~5 plant species in each plot -changes with slope, nest density

High Burrow Density Lesser Burrow Density

Aleutian Plant Dispersal“Two Way Filter Bridge” (Carlquist, 1965)

Near Is. (US)

Rat Is. (US)

Commander Is. (Russia)

Buldir Is.

Commander Is. Rat IslandsNear Islands

Amphi-Pacific Amphi-PacificAmphi-Pacific

N.A.

N.A.

AsianAsianAsianN.A.

Aleutian Plant Dispersal

Near Is. (US)

Rat Is. (US)

Commander Is. (Russia)

Buldir Is.

Proposed ConstraintsTime constraint:• Deglaciation • Eruptions

Distance barrier

Biotic Constraint:Seabirds as dispersal filters

71 Species not found in Rat Islands (25%)

Rat IslandsNear Islands

Amphi-PacificAmphi-Pacific

N.A.

N.A. Asian

91 Species not found on Near Islands (29%)

Asian

Near Islands

Rat Islands

Hypothesis- Buldir Island acts as a dispersal filter between the Near and Rat Islands.

• Species that survive Buldir’s constraints will be dispersed• Near Islands Rat Islands dispersal is rare

Sorbus sambucifolia

Antennaria monocephala

Buldir Island

Methods: Phylogenetic Analyses

Phylogenetic approaches utilize the relatedness among species to infer assembly processes. Requires:• Knowledge of floral composition• A phylogenetic “supertree” built from floral composition and a

phylogenetic database• The identification of constraints

Phylogenetic analyses have been used to infer the distance barriers driving community composition in the Ryukyu Archipelago (Kubota et. al., 2011)

* Amchitka graminoids added

Western Aleutian Islands by Plant # and Island Size

0 100 200 300 400 500 600 700 800 900 10000

50

100

150

200

250

300

Attu

Agattu

Buldir

Amchitka

Kiska*

Island Size (km 2)

Plan

t Spe

cies # Near Islands

Rat Islands

Conclusions• The Western Aleutians are important for East-

West and West-East dispersal• The Rat islands and Near Islands are

floristically dissimilar• Buldir Island community assemblage is highly

constrained by seabird colonies

Future Work• Complete Buldir seabird colony survey &

island flora (August 2011)• Complete phylogenetic analyses• More collecting in the Western Aleutians

Near Islands

Rat Islands

Western Aleutian Islands

24

194

205

145

142270

2010 Survey• First collection of Saxifraga

unlaschensis• 226 collections (138 taxa)

Population samples• Therorhodion camtschaticum• Saxifraga foliolosa

There are still several incomplete floras in the Western Aleutians

Semisopochnoi Island: • 60th largest Island in the United

States• 25 collections in ARCTOS, totaling 24

species

Attu Island 194 collected species

Kiska Island: Only ~6 graminoid species have been collected & reported (largest families in the Aleutians)

Acknowledgements• Jeff Williams & Dr. Vernon Byrd of AMNWR• Herbarium – Jordan, Zach, Carolyn, Dave, Kelsey, Stephanie J.• Dr. Christa Mulder• Melody Durrett• Tiglax Crew• Ian Jones• Scott Freeman• 2010 Buldir FWS personnel

Funding• Acknowledgement to Alaska EPSCoR NSF award #EPS-0701898 and the

state of Alaska• Acknowledgement to FWS via AMNWR for travel and logistical support

Questions?