Reference genomes

Chromosome number remains stable for millions of years in many animal lineages. Some butterflies and moths are different. Most Heliconius species carry 21 chromosomes in the haploid set, but five species in the sapho group have up to 60 after repeated fissions.

Lepidopteran chromosomes are holocentric. During cell division, the machinery that moves them can attach along the whole chromosome instead of at one centromere. A broken fragment can therefore retain the machinery needed to move into a daughter cell. This may help chromosome fissions persist, but it does not explain why they spread through a population.

In the Heliconius sapho group, genomic studies identified three W-autosome fusion events. The W fused with chromosome 4 in their common ancestor, followed by separate fusions with chromosomes 9 and 14 in two descendant lineages.

Sources: Rueda-M et al. 2024 · Mackay-Smith et al. 2026

Parides ascanius is restricted to coastal restinga and wetlands in south-eastern Brazil. The IUCN assessed it as Vulnerable globally in 2018. Brazil’s national assessment listed it as Endangered in 2021.

Seraphim and colleagues used mitochondrial COI sequences and eight microsatellite markers to compare the surviving populations. Their 2016 study found little genetic structure, no evidence of inbreeding and high migration among most sampled sites, although one population was more isolated by the metropolitan landscape.

The 2016 result provides a baseline but does not show whether the populations remain connected today. A chromosome-scale reference and new population sampling could measure how much diversity remains and whether habitat loss, drainage or fragmentation has interrupted gene flow.

Sources: Seraphim et al. 2016 · IUCN Red List, 2018 · ICMBio, 2021

Several closely related moth species occur in Brazilian soybean fields and can be difficult to distinguish during monitoring. Reliable identification matters because movement and resistance can differ among species.

Brazilian studies have found that susceptibility to insecticidal proteins is changing, so each species needs repeated testing. Genomic data can distinguish the species, compare movement among populations and identify variants associated with resistance.

Genomes do not measure crop damage or prove that a variant causes resistance by themselves. Field trials, bioassays, agronomy and growers’ observations are still needed to choose a management response.

Sources: Horikoshi et al. 2021 · Braga et al. 2024

In 2020, Gallice and colleagues recorded 2,509 Panacea prola in 50 one-hour observations in south-eastern Peru. Only 19 flew in another direction. They presented the observation as the first evidence of an Amazonian insect migration.

The closest available genomic reference is from another member of the same subfamily, Batesia hypochlora. It cannot reveal where these butterflies came from, whether they belonged to one population or several, or whether the movement repeats each year.

Comparing samples from different places, seasons and years could estimate ancestry and connectivity. Genomes would still need to be combined with field observations, environmental data or other movement evidence.

Sources: Gallice et al. 2020 (preprint) · Pham et al. 2026