Post on 20-Feb-2016
description
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?