Miocene Climate and Habitat Change Drove Diversification in Bicyclus, Africa's Largest Radiation of Satyrine Butterflies.

Kwaku Aduse-Poku,Steve C Collins,David J Lohman,Erik Van Bergen,Rampal S Etienne,Paul M Brakefield,Niklas Wahlberg,Oskar Brattström,Szabolcs Sáfián,Leonel Herrera-Alsina

doi:10.1093/sysbio/syab066

Abstract

Compared to other regions, the drivers of diversification in Africa are poorly understood. We studied a radiation of insects with over 100 species occurring in a wide range of habitats across the Afrotropics to investigate the fundamental evolutionary processes and geological events that generate and maintain patterns of species richness on the continent. By investigating the evolutionary history of Bicyclus butterflies within a phylogenetic framework, we inferred the group’s origin at the Oligo-Miocene boundary from ancestors in the Congolian rainforests of central Africa. Abrupt climatic fluctuations during the Miocene (ca. 19–17 Ma) likely fragmented ancestral populations, resulting in at least eight early-divergent lineages. Only one of these lineages appears to have diversified during the drastic climate and biome changes of the early Miocene, radiating into the largest group of extant species. The other seven lineages diversified in forest ecosystems during the late Miocene and Pleistocene when climatic conditions were more favorable—warmer and wetter. Our results suggest changing Neogene climate, uplift of eastern African orogens, and biotic interactions have had different effects on the various subclades of Bicyclus, producing one of the most spectacular butterfly radiations in Africa. [Afrotropics; biodiversity; biome; biotic interactions; Court Jester; extinction; grasslands; paleoclimates; Red Queen; refugia forests; dependent-diversification; speciation.]

Highlights

IntroductionThe drivers of diversification in Africa are poorly understood
Compared to other regions, the drivers of diversification in Africa are poorly understood
We studied a radiation of insects with over 100 species occurring in a wide range of habitats across the Afrotropics to investigate the fundamental evolutionary processes and geological events that generate and maintain patterns of species richness on the continent

Summary

Introduction

The drivers of diversification in Africa are poorly understood. Recent advances in mechanistic modeling of macroevolution allow the relative effects of intrinsic biotic interactions and extrinsic abiotic factors on diversification to be evaluated by modeling diversification rates as a function of time, diversity, environmental changes, and character states using time-calibrated phylogenies (Stadler 2011; Etienne et al 2012; Condamine et al 2013, 2018a; Morlon et al 2016, 2020; Lewitus and Morlon 2018; HerreraAlsina et al 2019) but see Louca and Pennell (2020) Using these tools, evolutionary histories and inferred diversification mechanisms of many taxa have been identified (e.g., Claramunt and Cracraft 2015; McGuire et al 2014; Toussaint et al 2014; Lagomarsino et al 2016; Condamine 2018). Bicyclus Kirby 1871, an African-endemic butterfly genus, is an ideal taxon for evaluating the contributions of biotic and abiotic factors in the generation and SYSTEMATIC BIOLOGY

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