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. 2018 May 3;9(1):1778.
doi: 10.1038/s41467-018-04218-4.

Macroecology and Macroevolution of the Latitudinal Diversity Gradient in Ants

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Free PMC article

Macroecology and Macroevolution of the Latitudinal Diversity Gradient in Ants

Evan P Economo et al. Nat Commun. .
Free PMC article

Abstract

The latitudinal diversity gradient-the tendency for more species to occur toward the equator-is the dominant pattern of life on Earth, yet the mechanisms responsible for it remain largely unexplained. Recently, the analysis of global data has led to advances in understanding, but these advances have been mostly limited to vertebrates and trees and have not provided consensus answers. Here we synthesize large-scale geographic, phylogenetic, and fossil data for an exemplar invertebrate group-ants-and investigate whether the latitudinal diversity gradient arose due to higher rates of net diversification in the tropics, or due to a longer time period to accumulate diversity due to Earth's climatic history. We find that latitudinal affinity is highly conserved, temperate clades are young and clustered within tropical clades, and diversification rate shows no systematic variation with latitude. These results indicate that diversification time-and not rate-is the main driver of the diversity gradient in ants.

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Phylogenetic position and latitudinal extent of 14,512 ant species. The all-ant ML phylogeny dated using median node ages across the posterior tree set from a Bayesian dating analysis, annotated with the latitudinal ranges of each species. Branches are colored by net diversification rate inferred by BAMM. The displayed tree was constructed using median node ages under the NC-stem dating/grafting method and was used to give typical results for visualization purposes, but the analyses were performed individually on 100 separate trees from the posterior for each method
Fig. 2
Fig. 2
Global patterns of ant diversity and evolution. Species richness by a region and b 5° latitudinal band. Phylogenetic diversity by c region and d latitudinal band, where the gray area reflects the distribution of 95% null values while the blue area reflects 95% of observed values across 100 trees in the posterior distribution. Both null and observed values were subtracted from the null mean for each tree. Mean of ln(median diversification rate across trees) for all species in each e region or f latitudinal band, with blue shading standard deviation of the variation within each band. These plots are based on trees constructed with NC-stem dating/grafting method, but corresponding results with other methods are found in Supplementary Figs. 2-3
Fig. 3
Fig. 3
Tropical and extratropical ant lineages through time. a The marginal probability each node was extratropical in the backbone trees (NC dating method) under the AIC minimizing trait evolution model. Gray dots are nodes from all 100 posterior trees, and blue dots are nodes from the mcc tree. b The number of lineages through time reconstructed with high confidence (probability >0.90) to be either tropical (red) or extratropical (blue) for each posterior tree (lighter color) and the mean across trees (darker color). Results for other trait-evolution models are presented in Supplementary Figs. 6,7

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