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Global Phylogeny Supported Little Heron as a Separate Old World Species

Little heron perched on a branch in Kruger National Park, South Africa
Research: Evolution & taxonomy, Genetics & genomics

A global analysis of Butorides herons has provided new genetic and morphological support for treating the little heron (Butorides atricapilla) as a species distinct from the South American striated heron (B. striata). The study was first published online in March 2026 in Molecular Phylogenetics and Evolution.

The researchers reconstructed relationships within the genus using thousands of ultraconserved elements, regions of the genome that can be compared across distantly related populations. They combined these data with morphological measurements from 308 live and preserved specimens drawn from across the broad distribution of Butorides.

Nuclear genomes separated Old World and New World lineages

The nuclear genomic data revealed a clear biogeographic division between Old World and New World lineages. The results supported splitting the former broadly defined striated heron complex into the South American B. striata, the Old World little heron B. atricapilla and the Galápagos lava heron B. sundevalli. All sampled lava herons grouped together as a single evolutionary lineage, which was sister to green herons rather than falling within South American striated herons.

The mitochondrial DNA did not reproduce every relationship seen in the nuclear genome, a pattern known as mito-nuclear discordance. The study therefore shows why taxonomic conclusions in this group benefit from combining different genetic datasets with morphology rather than relying on a single genetic marker.

Morphology supported the species split

Morphological comparisons added further evidence. Lava herons differed in bill dimensions from related populations, and Galápagos birds with a more striated-heron-like appearance still matched lava herons genetically and in culmen length, the length of the upper bill. Together with the broader genetic structure, this showed that the old worldwide use of the name B. striata concealed several evolutionarily distinct lineages. The results therefore support the recent taxonomic treatment in which little heron covers the Old World populations formerly included within the much broader striated heron.

Sources and image credit

  1. Mendales, E. Z., McCormack, J. E., Castañeda Cepeda, J. S., Dumbacher, J. P., & Chaves, J. A. (2026). Global phylogenetic relationships of Butorides herons (Aves: Ardeidae) reveal the evolutionary history and taxonomic status of the Galápagos Lava Heron. Molecular Phylogenetics and Evolution, 220, 108600. https://doi.org/10.1016/j.ympev.2026.108600Primary research article. Genus-level phylogeny based on thousands of ultraconserved elements, combined with morphological data from 308 live and preserved specimens; supports splitting the former broad Butorides striata complex into B. striata, B. atricapilla and B. sundevalli.
  2. PubMed. (2026). Global phylogenetic relationships of Butorides herons (Aves: Ardeidae) reveal the evolutionary history and taxonomic status of the Galápagos Lava Heron. PMID 41831543.Bibliographic record confirming the 2026 article date and DOI.

Image: Bernard Dupont / Wikimedia Commons / Flickr — little heron (Butorides atricapilla atricapilla) photographed at Lake Panic Hide, Kruger National Park, South Africa, 15 January 2019; representative image of the nominate Little Heron lineage discussed in the taxonomic study, cropped to 16:9 from the original · CC BY-SA 2.0 · Source

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