DOI: 10.5061/dryad.c32hr
title: Data from: Ecological history of a long-lived conifer in a disjunct population

description: 1. In northern Idaho (USA), more than 100 vascular plant species are
 disjunct &lt;200 km from their main distribution along the Pacific
 Northwest coast. It remains unclear whether most species within this
 interior forest disjunction, including Tsuga mertensiana, survived the
 last glacial period in a north-Idaho refugium or whether these species
 colonized the region via long-distance dispersal during the Holocene. 2.
 Sediment cores were extracted from three mid- to high-elevation lakes
 within T. mertensiana dominated forests in the Northern Rocky Mountains of
 Idaho. Pollen and macrofossils were used to reconstruct forest
 composition, determine the timing of T. mertensiana establishment, examine
 the hypothesis that the region was a glacial refugium, and contrast how
 climate, competition and/or dispersal limitation has influenced its modern
 distribution. 3. The modern distribution of T. mertensiana was analyzed by
 constructing a range map and modeling the potential species distribution.
 The presence of outlier populations surrounding the Idaho disjunction
 along with broad areas of unoccupied suitable habitat indicates the range
 of T. mertensiana is currently expanding. To assess the accuracy of T.
 mertensiana pollen at detecting its range limit, a network of pollen
 surface samples was used to analyze the probability of detecting T.
 mertensiana pollen as a function of distance from its geographic range
 limit. Consistent T. mertensiana pollen occurrence at ≥1% abundance is
 likely only within 42 km of its range limit. 4. T. mertensiana first
 appears in the pollen and macrofossil record at the highest elevation site
 at ca. 4100 cal yr BP, then at the next-highest-elevation site at ca. 1600
 cal yr BP, and last at the mid-elevation site at 800 cal yr BP. T.
 mertensiana pollen occurs continuously at ≥1% at all three sites by ca.
 300 cal yr BP suggesting regional presence. The timing of arrival suggests
 that T. mertensiana is a recent component of the forests of Idaho, having
 arrived during the Holocene via long-distance dispersal from coastal
 populations over 200 km away. 5. Synthesis. Comparison with palaeoclimate
 reconstructions from the broader region suggest that climate was a greater
 limiting factor than dispersal in the Holocene establishment in the
 interior, indicating little difficulty overcoming a large dispersal
 barrier. However, T. mertensiana remained at low abundances for millennia
 until Little Ice Age climates promoted its recent increase in abundance.
 Unoccupied areas of suitable habitat suggest that competition, rather than
 climate or dispersal, is limiting range-infilling in the interior mesic
 forests today.
description: Tsuga mertensiana point
 locations/observations data setPoint locations (7480
 unique) of Tsuga mertensiana obtained from various databases and
 references. Meta data including the data base source, collector, date of
 collection, location, latitude, longitude, and elevations are
 provided.Tsuga mertensiana Locations
 Data Sheet.csvDismal Lake
 DataThis file contains the
 meta data (site location, elevation, and radiocarbon dates), pollen
 (percentages and raw counts), macrofossils (identified and abundance), and
 charcoal counts from a sediment core taken from Dismal Lake,
 Idaho.Herring et al_JEcology_Dismal
 Lake Data.xlsxHorseshoe Lake
 DataThis file contains the
 meta data (site location, elevation, and radiocarbon dates), pollen
 (percentages and raw counts), macrofossils (identified and abundance), and
 charcoal counts from a sediment core taken from Horseshoe Lake,
 Idaho.Herring et
 al_JEcology_Horseshoe Lake
 Data.xlsxRocky Ridge Lake
 DataThis file contains the
 meta data (site location, elevation, and radiocarbon dates), pollen
 (percentages and raw counts), macrofossils (identified and abundance), and
 charcoal counts from a sediment core taken from Rocky Ridge Lake,
 Idaho.Herring et al_JEcology_Rocky
 Ridge Lake Data.xlsxTsuga mertensiana
 distributionShape file used for
 construction of the distribution map of Tsuga mertensiana Figure 1. The
 Tsuga mertensiana distribution was developed by merging an ecoregion
 classification in British Columbia with a 6-km buffer around 7480
 georeferenced observations (Tsuga mertensiana Locations Data
 Sheet.csv).tsme_range.zip