Lepechinia hastata

This species was first described as Sphacele hastata by Asa Gray in 1862, from plants collected by the United States Exploring Expedition led by Charles Wilkes. The type locality is Mouna Haleakala on Maui, at high elevations.[8]

In 1940, botanist Carl Epling, who was the major authority on the Lamiaceae, renamed S. hastata into Lepechinia hastata, and based on collections by Gentry, noted their presence in the oak-pine forests of the Sierra de La Laguna of the Cape region of Baja California Sur.[9]

Detail of the leaves

The plants on Socorro Island were discovered by Ivan M. Johnston in 1931 and placed as L. hastata proper, with Lepechinia expert Carl Epling concurring with the identification, but later examination of flowering plants on Socorro in 1989 led to Reid Moran separating the Socorro plants as their own subspecies due to morphological differences.[6]

Epling placed L. hastata in the section Thyrsiflorae, which only has one other species, L. nelsonii, from Jalisco and Guerrero, Mexico. The section is distinguished by the open paniculate structure of the inflorescence with is 2 to 3 times cymosely branched. The two species are most similar in their flowers and inflorescences, but differ in their foliage, as L. nelsonii has elliptic or lanceolate leaves that are sessile.[7] Section Thyrsiflorae is most closely allied to the section Speciosae, with L. hastata being most similar in some aspects to that section's L. salviae.[5]

• Lepechinia hastata subsp. hastata — The autonymic subspecies. Found in Baja California Sur and the Hawaiian Islands.[3]
• Lepechinia hastata subsp. socorrensis Moran — Endemic to Socorro Island. This species is distinguished by its white-colored flowers, more densely tomentose and conspicuously grayer foliage, and smaller size in terms of its leaves, inflorescence, and floral parts.[6]

In Baja California Sur, subspecies hastata is distributed in the Cape region at the tip of the peninsula, at high elevations in the Sierra de La Laguna. It is found growing in shaded canyons and the Sierra de la Laguna pine–oak forests.[3][4]

Detail of the flower, in habitat in Baja California Sur

On Socorro Island, subspecies socorrensis is found growing on the upper half of the southern slope of the island, typically in rocky places with low vegetation, where it is often the dominant shrub. The abundance of the plant in spite of the existence of introduced grazing sheep indicates that it may be distasteful to them.[6]

Fruiting in habitat, Baja California Sur

In the Hawaiian Islands, subspecies hastata is only found on Maui in an "uninterrupted belt" around Haleakala, at an elevation of about 2,000 to 3,000 ft (610 to 910 m) above sea level.[5] Compared with the plants of the Cape region and Socorro Island, the plants of Maui vary in the amount and color of their hairs, with some having a similar amount of pubescence to those on Socorro, and others having less pubescence.[6]

The disjunct distribution between Hawaiian plants and the other plants of subsp. hastata in the Baja California Cape suggests that either this species has been introduced by humans to Hawaii, or that a biogeographic problem must be resolved to explain the distribution. The majority of Lepechinia species are only found in North and South America,[5] and one of the only other outliers, Lepechinia stellata (now a synonym of L. chilensis[10]), was only known from a fragmentary herbarium record from Réunion Island, as the original type specimen was lost.[7] A taxonomic study of the genus conducted in 2011 suggests that the occurrences from Réunion and Hawaii are probably human introductions.[11]