Gastrolobium is a genus of more than 100 species of shrubs and small trees in the legume family Fabaceae (order Fabales). The genus was described by the Scottish botanist Robert Brown and belongs to the tribe Bossiaeeae within the broad pea-flower subfamily Papilionoideae.
The genus is remarkably concentrated geographically: all but two of its species are endemic to the South West Botanical Province of Western Australia, one of the world's recognised biodiversity hotspots. This tight endemism makes Gastrolobium one of the most regionally confined large genera in the Australian flora.
Gastrolobium species are perhaps best known for their accumulation of monofluoroacetate — the compound more widely known as sodium fluoroacetate or "1080" — in their foliage and seeds. Native Australian fauna that co-evolved with these plants have developed tolerance to the toxin, but introduced livestock, foxes, and rabbits are highly susceptible. From the 1840s onwards, unexplained deaths of sheep and cattle in Western Australia were traced to these plants; botanist James Drummond conducted early investigations and identified York Road poison (G. calycinum) and Champion Bay poison (G. oxylobioides) as primary culprits. Research continued through the 1930s and 1940s under C.A. Gardner and H.W. Bennetts, culminating in the landmark publication The Toxic Plants of Western Australia (1956). Today, 1080 bait made from sodium fluoroacetate is used as a conservation tool in Australia precisely because native wildlife is resistant while introduced predators are not.
Many species in the genus carry common names that reflect this toxicity — Scaleleaf Poison, Cluster Poison, Rock Poison, Heart Leaf Poison — and they are treated with caution in pastoral areas of south-west Western Australia. The base chromosome number of the genus is 2n = 16.
Etymology
The name Gastrolobium derives from the Greek gastēr (stomach, belly) and lobos (pod or lobe), alluding to the swollen or belly-shaped seed pods characteristic of many species in the genus. The genus was established by Robert Brown in his Prodromus Florae Novae Hollandiae et Insulae Van Diemen (1810).
Distribution
Almost all species of Gastrolobium are endemic to the South West Botanical Province of Western Australia; only two species occur outside this region. This extreme concentration in a single biogeographic province reflects the high endemism characteristic of the south-west Australian floristic region, a recognised global biodiversity hotspot.
Ecology
Many Gastrolobium species accumulate monofluoroacetate (1080) in their tissues. Native Australian herbivores and marsupials that evolved alongside these plants have developed physiological tolerance to the toxin, whereas introduced species — including sheep, cattle, rabbits, and foxes — are acutely susceptible. This differential tolerance has made sodium fluoroacetate derived from these plants a tool in invasive-predator and rabbit-control programs in Australia.
Taxonomy Notes
Gastrolobium (authority R.Br.) is placed in the family Fabaceae, order Fabales. GBIF records 86 accepted descendants. The genus was historically separated from related genera such as Oxylobium, and several former Oxylobium species were subsumed into Gastrolobium following revisions by Chandler and Crisp in the late twentieth century. No synonyms are currently listed under the accepted concept in GBIF.
