DOI: 10.5061/dryad.fr48qn7
title: Data from: The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants

description: Studies on elevation gradients in Panama and Costa Rica have shown that
 leaf-litter ants exhibit a mid-elevation peak in diversity. This diversity
 pattern has been observed in other groups and regions, but uncertainty
 remains as to just how pervasive it is and what might explain it. Here we
 examine the robustness of the mid-elevation peak in ant diversity across
 the entire Middle American corridor, from Veracruz, Mexico, to Costa Rica.
 We sampled 56 sites distributed throughout Middle America. All were in
 closed-canopy evergreen wet forest, spanning 11° latitude, from near sea
 level to 2600 m elevation. Ants were extracted from 100 litter samples
 from each site and identified to genus or species. Model selection was
 performed on richness and diversity variables to test if ant diversity
 best fits a linear model or one allowing for a mid-elevation peak. Linear
 models were also used to examine the relationships among diversity
 measures and temperature, precipitation, and seasonality. Species richness
 measures and diversity indices that incorporate relative abundance show a
 similar relationship to elevation throughout the region: a truncated bell
 curve with a mode near 400 m. A cubic relationship is statistically
 favored over quadratic or linear. Temperature is a significant correlate
 with diversity, but does not predict a bell-curve. Precipitation and
 precipitation seasonality fail to explain much of the variability, and no
 combination of environmental variables predicts a bell curve. Potential
 causes of the truncated bell curve include lowland biotic attrition,
 mid-point attractors, and ecotonal transitions from lowland to montane
 communities. Analysis of 17 subclades within ants mostly showed the same
 truncated curve but six clades were anomalous. Distinctive behavioral or
 historical features potentially explain their patterns.
description: Collection codes and
 locality data for individual miniWinkler samples from 56 sample sites in
 the Middle American corridorCollection codes and
 locality data for individual miniWinkler samples from 56 sample sites in
 the Middle American corridor. Column headers are "site" (site
 codes in Supplementary material Appendix 1 Table A1), "transect"
 (1 or 2 for sites with two transects of 50 samples, "na" for
 others), "collectioncode" (a unique collection code associated
 with each sample), "datecollected" (dd-mon-yyyy),
 "latitude" (decimal degrees), "longitude" (decimal
 degrees), "latlonerror" (potential error around the latitude and
 longitude point, in m), "elevation" (m). Header row is followed
 by 5599 data rows.TableA2.csvOccurrence matrix for ant species and genus-level taxa at 56 sample sites in the Middle American corridorTable A3. Occurrence matrix for ant species and genus-level taxa at 56 sample sites in the Middle American corridor. Column headers are the 56 site codes in Supplementary material Appendix 1 Table A1. Row headers are taxon names. Values are frequency of occurrence in 100 miniWinkler samples.TableA3.csv