Is molecular evolution faster in the tropics?

Matthew G Orton,Jacqueline A May,Sarah J Adamowicz,David J Lee,Winfield Ly

doi:10.1038/s41437-018-0141-7

Matthew G Orton, Jacqueline A May + Show 3 more

Open Access

https://doi.org/10.1038/s41437-018-0141-7

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Journal: Heredity	Publication Date: Sep 10, 2018
Citations: 24	License type: open-access

Affiliation: University of Guelph, Seneca College

Abstract

The evolutionary speed hypothesis (ESH) suggests that molecular evolutionary rates are higher among species inhabiting warmer environments. Previously, the ESH has been investigated using small numbers of latitudinally-separated sister lineages; in animals, these studies typically focused on subsets of Chordata and yielded mixed support for the ESH. This study analyzed public DNA barcode sequences from the cytochrome c oxidase subunit I (COI) gene for six of the largest animal phyla (Arthropoda, Chordata, Mollusca, Annelida, Echinodermata, and Cnidaria) and paired latitudinally-separated taxa together informatically. Of 8037 lineage pairs, just over half (51.6%) displayed a higher molecular rate in the lineage inhabiting latitudes closer to the equator, while the remainder (48.4%) displayed a higher rate in the higher-latitude lineage. To date, this study represents the most comprehensive analysis of latitude-related molecular rate differences across animals. While a statistically-significant pattern was detected from our large sample size, our findings suggest that the EHS may not serve as a strong universal mechanism underlying the latitudinal diversity gradient and that COI molecular clocks may generally be applied across latitudes. This study also highlights the merits of using automation to analyze large DNA barcode datasets.

Highlights

The latitudinal diversity gradient is one of the most striking and general features of biodiversity (Hillebrand 2004)
Despite the broad appeal and apparent explanatory power of this mechanism, there remains considerable uncertainty about whether rates of molecular evolution tend to be higher in the tropics
While the overall results were dominated by the large sample size of Arthropoda, patterns were generally similar across taxa, including both endotherms and ectotherms (Table 1, Table S3)

Summary

Introduction

The latitudinal diversity gradient is one of the most striking and general features of biodiversity (Hillebrand 2004). Higher rates of molecular evolution have been detected at lower latitudes for diverse taxa, including mammals (Gillman et al 2009), birds (Gillman et al 2012), amphibians (Wright et al 2010), aquatic turtles (Lourenço et al 2013), marine fish (Wright et al 2011), angiosperms (Davies et al 2004; Wright et al 2006; Gillman et al 2010), and Foraminifera (Allen et al 2006) (differences in elevation or water depth were considered together with latitude in some studies). Latitude was not significantly associated with branch lengths in lizards and snakes (Rolland et al 2016), terrestrial turtles (Lourenço et al 2013), water beetles (Fujisawa et al 2015), or birds (Bromham and Cardillo 2003)

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