Purple-spined Hedgehog Cactus
Echinocereus relictus
NatureServe conservation status
Global (G-rank): G5T1?Q
State (S-rank): S1
Utah Wildlife Action Plan status
- SGCN
External links
General information
Echinocereus relictus has a complicated taxonomic history that has only recently resulted in its recognition as an independent species. Originally considered a variety of E. engelmannii, this cactus was listed as endangered under the name E. engelmannii var. purpureus by the USFWS in 1979, only to be later removed in 1989 as taxonomists considered it to be synonymous with E. engelmannii var. chryocentrus. However, recent studies of the cytology and morphological characteristics of this plant have elevated it to species once again, now thought to be an ancestor to E. engelmannii. It is found in the low elevation regions southwest Utah and northwest Arizona, and can be found occurring with E. engelmannii across a portion of its range.
Description
This species of hedgehog cactus develops into compact to somewhat-open clumps, with cylindric or tapering stems reaching 10-30 cm tall and an average of 5.2 cm at their base. Stems show between 11-14 ribs with slightly undulating crests, and an average distance between ribs of 10.5 mm. Areoles (the light, bumpy structures on a cactus from which stems emerge) contain 16-22 spines that may appear straight or curved/twisted. The color of the spines ranges significantly; individuals may show yellow, reddish-brown, blackish-purple, or white-gray spines. Flowers may be rosy-pink to magenta and are 5-9 cm long, borne laterally below the stem’s apex. Echinocereus bears fleshy, spiny fruit; in this species the fruit is 20-40 mm long and wide, ovoid-spherical, red-orange in color with a white-reddish pulp.
Phenology
Flowering times of this species vary largely based on environmental factors such as elevation, temperature, and precipitation. However, typically flowering occurs from late March to mid-May. Fruit matures 6-8 weeks later in June and July.
Diagnostic characteristics
A greater number of ribs on the stem, as well as a shorter spacing between those ribs, help distinguish E. relictus from E. engelmanni. E. relictus also tends to have shorter/smaller spines, as well as a narrower stem diameter. Though impossible to measure in the field, E. relictus was identified as a species largely because it is diploid, that is, it contains 2 copies of each chromosome within its cells. This differs from E. engelmanni, which is tetraploid. These two species are both readily distinguishable from two other species in the region, E. coccineus and E. mojavensis, based on their flower color, and size.
Species range
E. relictus is thought to range across 1300 square km in Mohave County, Arizona, and Washington County, Utah. However, estimates of its actual occupancy are much lower, with only 22 occurrences known from Washington County. The biogeography of this species suggests that it first reached the St. George area ~21,000 years ago, when the region was colder and wetter and contained woodland habitat.
Habitat
E. relictus occurs at lower elevations among desert shrub, black brush, and pinyon/juniper plant communities. It can be found in rock outcrops as well as open plains, hills, and dry mountain slopes; at higher elevations in its range it may be found in woodland habitats. May occur in rocky or sandy soils derived from limestones or sandstones.
Threats or limiting factors
The primary threat is habitat loss and degradation due to urbanization of area surrounding St. George, Utah. Additional threats include impacts from recreational activities, collection of cacti, grazing, and drought.
Taxonomy
No, this species does not have taxonomic discrepancies