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Unveiling the Evolutionary Journey of Butterflies Using Phylogenomics

Radd Icenoggle

December 6, 2023

Butterflying,Evolution & Phylogenetics

Butterflies, with their vibrant colors and intricate patterns, have remained enigmatic in terms of their origin, diversification, and evolutionary interactions with plants. Recently, researchers from the University of Florida sequenced 391 genes from nearly 2,300 butterfly species, creating a robust phylogenomic tree that represents 92% of all genera. The paper was published in Nature under the title “A global phylogeny of butterflies reveals their evolutionary history, ancestral hosts and biogeographic origins” by authors Kawahara et al. The findings challenge existing classifications, proposing the reclassification of at least 36 butterfly tribes. So, be prepared for a taxonomic shake-up and your field guides to be out-of-date. but, the most fascinating bit of knowledge to come out of this paper is the timing of butterfly divergence, revealing a butterfly origin approximately 100 million years ago from moth ancestors. The biogeographic analysis suggests that butterflies originated in the Americas and later dispersed across the globe, including Antarctica for a time. The study further investigates the evolution of larval host plant use, indicating an early association with Fabaceae (the pea family) in the Americas. Most intriguingly, it highlights that while the majority of butterfly species are specialists with a single larval host, generalists tend to feed on closely related plants.

Time-calibrated tree of 2,244 butterfly species based on 391 loci and 150 amino acid partitions (Kawahara et al, 2023)
Time-calibrated tree of 2,244 butterfly species based on 391 loci and 150 amino acid partitions (Kawahara et al, 2023)

In a comprehensive exploration of butterfly phylogenetics and evolution, researchers employed advanced gene sequencing, including targeted exon capture, to analyze 2,244 species from 90 countries. The resulting phylogenomic trees challenge the existing Lepidoptera classification, recommending the revision of ~27% of butterfly tribes. Dating analyses indicated a mid-Cretaceous origin approximately 101.4 million years ago from herbivorous moth ancestors. This study not only contributes to our understanding of butterfly taxonomy but also unveils their temporal origins, highlighting the intricate patterns that have shaped the global diversity of these captivating insects.

Pale Swallowtail - Papilio eurymedon
Pale Swallowtail - Papilio eurymedon

The study uncovered the geographic origin of butterflies using a dated phylogenomic tree and a global biogeographic analysis. Analyzing 15,764 country-level distribution records, the researchers consistently traced the origin of butterflies to the Americas, specifically western North America or Central America. The diversification of butterfly families, excluding Neotropical Hedylidae, occurred approximately 10-30 million years following the Cretaceous Thermal Maximum (~90 million years ago).

During the Cretaceous period, butterflies dispersed from the Neotropics at a higher rate compared to other routes. The Neotropics fostered around 60 million years ago a massive situ butterfly speciation, with subsequent lineages dispersing to other regions. Butterfly speciation rates were notably higher in tropical zones than in temperate zones, with the tropics serving as the origin of most dispersal events.

The majority of dispersal events between the Neotropics and the Nearctic occurred after the Eocene/Oligocene boundary around 33.9 million years ago. Two lineages originating from the Eastern Palaearctic around 17 million years ago were identified as the initial colonizers of Europe, representing ancestors of the Nymphalini subclade and a clade of checkered skippers (Carcharodini). By the late Eocene, butterflies were present on all modern continental landmasses.

Bioregion shading indicates the number of butterfly lineages that were associated with that bioregion during that time period with continental drift (Kawahara et al, 2023)

In the quest to unravel the evolution of larval host plant use in butterflies, the researchers compiled an extensive dataset of 31,456 butterfly host records sourced from 186 publications and databases. This compilation revealed that the origin and diversification of butterflies significantly lagged behind the emergence of angiosperms, meaning that the flowers came first and then the butterflies. 

The analyses provided empirical support for the hypothesis that Fabaceae served as the larval host plant for the most recent common ancestor of butterflies, with a crown age estimated at approximately 98 million years ago, aligning with the emergence of butterflies.

The study’s examination of host plant specificity on the butterfly phylogeny revealed that more than two-thirds of extant butterfly species (67.7%) feed on a single plant family, while less than a third (32.3%) are generalists, feeding on two or more families. This pattern is consistent with ecological studies. Notably, butterflies feeding on grasses and legumes (Poaceae and Fabaceae) often exhibit host specificity. The geographical abundance and lack of potent defensive chemicals in these plant families may have contributed to the enduring association between butterflies and these plants for millions of years.

The research also found that the majority of generalist butterflies (94.2%) feed on plant families that are significantly closely related, supporting the idea that generalists, while capable of feeding on different host families, tend to consume closely related plants. This observation aligns with the proposed pattern by Ehrlich and Raven, where related butterflies exhibit a preference for related plants.

Common Wood-Nymph - Cercyonis pegala
Common Wood-Nymph - Cercyonis pegala

Overall, the study’s comprehensive analysis of butterfly feeding patterns, host specificity, and the evolutionary history of host plant associations provides a valuable resource for future investigations into the ecological dynamics of these captivating insects.

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Butterflying,Evolution & Phylogenetics
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