DOI: 10.5061/dryad.q573n5tpz
title: Data from: Two focal populations and three regional populations of Sobralia chrysostoma

description: The dispersal and colonization of plant populations allow species to
 occupy novel habitats, migrate, and undergo range shifts in response to
 changing environmental factors and, as such, are fundamental ecological
 processes for ensuring the long-term persistence of species. Natural
 landscape disturbance often generates habitats available for colonization.
 Patterns of colonization and population expansion can be inferred from the
 levels and partitioning of genetic variation of plant populations with
 known disturbance histories, such as recent volcanic eruptions. We sampled
 and mapped 496 individuals from two populations of the colonizing
 terrestrial orchid, Sobralia chrysostoma, on the 1992 lava flow of Volcán
 Arenal in central Costa Rica. We used neutral co-dominant markers to
 genotype individuals and estimate population genetic statistics.
  Both populations had high mean levels of genetic diversity (P =
 100%; AP = 3.31; He = 0.259) suggesting that the lava flow was colonized
 by numerous individuals that likely originated from multiple source
 populations. However, significant spatial genetic structure (SGS) was only
 present in one population at the smallest distance class (≤ 2 m) and was
 low (r = 0.032). That these large and genetically diverse populations had
 such low SGS and an absence of SGS respectively is contrary to
 expectations and differs significantly from the pattern in Epidendrum
 radicans (Orchidaceae), with which S. chrysostoma is growing
 sympatrically. Our results suggest that these two populations either
 consist primarily of immigrant individuals or that seeds produced in situ
 dispersed over longer distances, thereby producing larger seed shadows and
 greater overlap of seed shadows.
description: In April 2004 leaves were collected from 288 <em>S.
 chrysostoma</em> individuals at the first Arenal Slope site (AS-1;
 10.4504° N and 84.7250° W). In April 2010, leaves were collected from 208
 <em>S. chrysostoma</em> individuals at the second site (AS-2).
 The populations are separated by ~90 m and the collections were separated
 by six years. From a central point in each population, a transect line was
 placed successively in a radial pattern and a leaf was collected from
 every individual, with its distance and angle relative to the central
 point recorded. Leaf samples were also collected from a
 mean of 49 individuals (range 46 - 50) from each of three regional
 populations of <em>S. chrysostoma</em> within 0.3 to 2.9 km
 (mean = 1.9 km) of the lava flow populations. Because of challenges posed
 by the terrain, sampled individuals were not mapped. While we did not
 survey the surrounding landscape comprehensively, we collected from every
 population found in the vicinity.  Leaves were snap
 frozen in liquid nitrogen within a few hours of collection, and
 transported to the University of Georgia in an ultra-cold dry shipper. 
 Leaves were crushed in chilled mortars with a pestle, liquid nitrogen, and
 a pinch of sea sand to disrupt cellular compartmentalization.  Enzymes
 were extracted from leaf tissue with the Wendel and Parks (1982)
 extraction buffer.  The resulting slurry containing crude protein extract
 was absorbed onto 4x6 mm wicks punched from Whatman 3 mm chromatography
 paper.  Wicks were stored in microtest plates at -70°C until used for
 electrophoresis.  For electrophoresis, wicks were placed in horizontal
 starch gels (10%).  Seven enzyme stains in four buffer
 systems resolved one monomorphic and eight polymorphic loci. Enzymes
 stained and polymorphic loci (in parentheses) for each buffer system were:
 (1) system 4, malate dehydrogenase (Mdh-2, Mdh-3), and 6-phosphogluconate
 dehydrogenase (6-Pgd); (2) system 7, aspartate aminotransferase (Aat), and
 menadione reductase (Mnr); (3) system 8-, triosephosphate isomerase
 (Tpi-1); (4) system 11, isocitrate dehydrogenase (Idh), and shikimic
 dehydrogenase (Skdh). All buffer and stain recipes were adapted from
 Soltis et al. (1983) except Aat (Cheliak & Pitel, 1984). Buffer
 system 8- is a modification of buffer system 8 described by Soltis et al.
 (1983). Banding patterns were consistent with Mendelian inheritance
 patterns expected for each enzyme system (Weeden & Wendel, 1989)
 and were consistent with disomic inheritance expected for diploid
 individuals.
description: **Two Focal Populations sheet**: * Column A indicates the number of
 individuals sampled within each population * Column B indicates the
 population names and the identification of each sampled individual. The
 two lava flow populations are AS-1 and AS-2. * Columns C and D include the
 x and y coordinates of mapped individuals within the two lava flow sites *
 The remaining columns contain co-dominant genotypic data from nine
 allozyme loci, with the names of loci indicated in row 1. * Alleles range
 from 1 to 8 * Missing data are indicated as -9 **Three Regional
 Populations sheet**: * Column A indicates the number of individuals
 sampled within each of three regional populations of *Sobralia
 chrysostoma*. * Column B indicates the population names. The three
 regional populations are SC-1, SC-2 and SC-3. * The remaining columns
 contain co-dominant genotypic data from nine allozyme loci, with the names
 of loci indicated in row 1. * Alleles range from 1 to 6 * Missing data are
 indicated as -9