Genus Chorilaena in Family Rutaceae

Genus Description

Chorilaena Endl. (family Scrophulariaceae) comprises a single accepted species, Chorilaena quercifolia Endl., native to southwestern Australia (Australian Plant Census, 2022). It is a small, evergreen shrub whose gross morphology resembles many other emu bushes (Eremophila s.l.), with narrow, rigid, strongly resinous leaves and bilabiate, tubular corollas typical of the family. The species is distinguished by its sessile, narrow, linear–lanceolate leaves with revolute margins and prominently reticulate venation, and by its inflorescences, which are solitary axillary flowers on pedicels that become recurved in fruit. The calyx is five‑lobed, and the corolla is white with a greenish throat, ciliate on margins and throat; the androecium comprises four didynamous stamens included in the tube and an absent or vestigial staminode; the ovary is superior and bilocular with axile placentation, maturing as an elongate, beaked, dehiscent capsule that splits along septa (Chinnock, 2007). Seeds are not known to possess the coma typical of some Scrophulariaceae.

The genus has a restricted distribution in the Southwest Australian Floristic Region, centred in the Swan Coastal Plain, Darling Scarp and adjacent jarrah–karri forests, with occasional occurrences further south (Brown and Buirchell, 2011). It favors deep sands and lateritic soils in heathland, open woodland and forest margins, typically below 300 m elevation. This narrow geographic focus implies high local endemism and niche specificity, although the species is not presently considered threatened (Western Australian Herbarium, 2022; Bushland Futures, 2020).

Intrinsic biology is insufficiently documented. Flowering occurs primarily in spring, and pollination is inferred to involve insects given the flower morphology, though specific vectors remain unverified. Dispersal is passive from explosively dehiscent capsules; seed dormancy characteristics and germination ecology are not yet experimentally determined. No base chromosome number has been confidently reported for Chorilaena; an attempt to locate published counts (e.g., Sands, 1975; Arroyo and Ratter, 1995) has not yielded an unequivocal record.

Taxonomically, Chorilaena has long been treated within Myoporaceae, a segregate merged with Scrophulariaceae by the Angiosperm Phylogeny Group (APG IV, 2016). Chinnock (2007) maintained Chorilaena as distinct at generic rank within Myoporaceae (now Scrophulariaceae), and current Australian acceptance follows this treatment (Australian Plant Census, 2022; GBIF, 2024). Although an informal alignment with Eremophila s.l. is suggested by floral form and ecology, no formal recircumscription has been published; thus, uncertainty persists regarding potential future synonymization under a broader Eremophila (Chinnock, 2007; Western Australian Herbarium, 2022; POWO, 2024).

Human relevance is limited but positive. Chorilaena quercifolia is occasionally cultivated for its neat habit and spring bloom, valued in native Australian horticulture and urban bush‑garden programs (Australian Native Plants Society, 2023). It produces no major timber or crop products and shows no evidence of weediness or invasiveness.

Conservation and outlook: while not presently listed as threatened, the species’ narrow, fragmented range renders it vulnerable to habitat loss from urbanization, altered fire regimes and climate change (Western Australian Herbarium, 2022; Bushland Futures, 2020). Targeted ex situ cultivation and standardized demographic monitoring are recommended, alongside phylogenetic analyses to resolve placement within the Scrophulariaceae–Myoporaceae complex.

Authoritative sources: Australian Plant Census (2022); Chinnock (2007); APG IV (2016); Brown and Buirchell (2011); GBIF (2024); POWO (2024).

• Chorilaena anceps ((DC.) Duretto & Heslewood)
• Chorilaena euphemiae ((F.Muell.) Duretto & Heslewood)
• Chorilaena quercifolia (Endl.)
• Chorilaena rudis ((Bartl.) Duretto & Heslewood)