Long-read sequencing reveals hidden structural diversity in Guam's invasive brown tree snakes

A new study using long-read DNA sequencing has uncovered unexpectedly high levels of structural genetic variation in brown tree snakes (Boiga irregularis) on Guam, an island the species colonised after accidental introduction in the late 1940s. Despite being descended from a small founder population — a scenario typically associated with severe inbreeding depression and reduced adaptive potential — the snakes carry more than 19,000 large structural variants across the genome. A disproportionate share of these variants cluster in genomic regions associated with immune function and olfactory sensing.

The research, reported by ScienceDaily on 26 July 2026, suggests that hidden structural diversity — not captured by conventional short-read sequencing approaches — may have buffered the population against the genetic costs of its bottleneck origin, and potentially facilitated its explosive expansion across Guam and the near-total collapse of the island's native bird fauna.

The findings have broader implications for conservation genomics and invasion biology. Standard short-read population-genomic surveys may systematically underestimate functional diversity in invasive or historically bottlenecked populations, with consequences for assessing adaptive potential. For conservation geneticists, the result also raises the question of whether analogous cryptic variation exists in endangered species long assumed to carry dangerously depleted gene pools. The primary journal source was not named in the feed item; readers are directed to the original ScienceDaily report for citation details.