Western Aleutian Plant Distribution: Buldir Island as a Dispersal Filter Monte 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 litterDecreased 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 plots Glaucous-winged Gull: Loafing areas 5-7 plant species per plot- Changes with elevation Annual Callitriche sp. collected in 2007, in loafing area 246m elev. 55m elev. 196m elev. Burrow nester plots Leachs Storm Petrels Fork-tailed Storm Petrels Cassins Auklets Ancient Murrelets ~5 plant species in each plot - changes with slope, nest density High Burrow DensityLesser Burrow Density Aleutian Plant Dispersal Two Way Filter Bridge (Carlquist, 1965) Near Is. (US) Rat Is. (US) Commander Is. (Russia) Buldir Is. Amphi-Pacific N.A. Asian N.A. Aleutian Plant Dispersal Near Is. (US) Rat Is. (US) Commander Is. (Russia) Buldir Is. Proposed Constraints Time constraint: Deglaciation Eruptions Distance barrier Biotic Constraint: Seabirds as dispersal filters 71 Species not found in Rat Islands (25%) Amphi-Pacific 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 Buldirs 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 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 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: 60 th 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 and the state of Alaska Acknowledgement to FWS via AMNWR for travel and logistical support Questions?