10.5061/DRYAD.FTTDZ08PG
Linck, Ethan
0000-0002-9055-6664
University of Tennessee at Knoxville
Celi, Jorge
Universidad Regional Amazónica IKIAM
Sheldon, Kimberly
University of Tennessee at Knoxville
Panmixia across elevation in thermally sensitive Andean dung beetles
Dryad
dataset
2020
National Science Foundation
https://ror.org/021nxhr62
IOS-1930829
2020-08-14T00:00:00Z
2020-08-14T00:00:00Z
en
https://github.com/elinck/scarab_migration/
71343262 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Janzen’s seasonality hypothesis predicts that organisms inhabiting
environments with limited climatic variability will evolve a reduced
thermal tolerance breadth compared with organisms experiencing greater
climatic variability. In turn, narrow tolerance breadth may select against
dispersal across strong temperature gradients, such as those found across
elevation. This can result in narrow elevational ranges and generate a
pattern of isolation-by-environment, or neutral genetic differentiation
correlated with environmental variables that is independent of geographic
distance. We tested for signatures of isolation-by-environment across
elevation using genome-wide SNP data from five species of Andean dung
beetles (subfamily Scarabaeinae) with well-characterized, narrow thermal
physiologies and narrow elevational distributions. Contrary to our
expectations, we found no evidence of population genetic structure
associated with elevation and little signal of isolation-by-environment.
Further, elevational ranges for four of five species appear to be at
equilibrium and show no evidence of demographic constraints at range
limits. Taken together, these results suggest physiological constraints on
dispersal may primarily operate outside of a stable realized niche, and
point to a lower bound on the spatial scale of local adaptation.
We sampled populations of our five focal species (Deltochilum
speciosissimum, Deltochilum tesselatum, Dichotomius podalirius,
Dichotomius satanas, Eurysternus affin. flocossus) along two elevational
and two horizontal transects on the eastern slope of the Andes Mountains
in Napo Province, Ecuador. Our two elevational transects spanned 730 to
1175 m and 1500 to 1950 m in largely undisturbed humid forest, with four
sampling localities spaced as close to 125 m apart as possible given local
constraints of soil and topography. Our two horizontal transects were each
approximately 2 km long, with one transect having four points and the
other having two points. Both horizontal transects were located in
replicate corridors of montane forest at 2150 m asl separated by a natural
barrier, the Cosanga River. No species were shared between the two
elevational transects. We extracted genomic DNA from all samples using
Qiagen DNeasy kits and the manufacturer’s recommended protocol for
insects. To prepare libraries for reduced representation high throughput
sequencing, we used a double restriction enzyme digest approach adapted
from Gompert et al., 2014. After initially demultiplexing our libraries
using our unique barcodes and a Python script implemented in the first
step of ipyrad (Eaton, 2014), we assembled sequencing reads and called and
filtered variants for each species independently using the dDocent
pipeline (v. 2.7.8), a set of bash wrapper scripts optimized for
population genomics of nonmodel organisms requiring de novo assemblies
(Puritz, Hollenbeck, & Gold, 2014). We then used VCFtools,
vcffilter (1.0.0) (https://github.com/vcflib/vcflib), and the dDocent
script dDocent_filters to filter this file to high quality SNPs alone.
Uploaded data can be used in conjunction with scripts in the
publication's GitHub repository
(https://github.com/elinck/scarab_migration) to recreate all figures and
results. data.zip: zipped archive of all intermediate (processed) data
files, including locality information, PCA results, ABC results, BEDASSLE
output, and data frames for plotting. vcfs.zip: zipped archive of .vcf
files for each species (with MAF filter) abc_vcfs.zip: zipped archive of
.vcf files for each species for ABC (without MAF filter)