Echinocereus arizonicus

Name and scope of the description

POWO accepts Echinocereus arizonicus as a distinct species. The former combinations Echinocereus coccineus var. arizonicus and Echinocereus triglochidiatus var. arizonicus are synonyms. The database gives a range from Arizona to New Mexico and the Mexican state of Chihuahua and recognises four subspecies. The pollination account concerns material from the Superstition Mountains in central Arizona, investigated over a much narrower area. [2-WWW] [Aslan 2015]

Clare Aslan described the studied plants as multistemmed cacti generally reaching about half a metre in height. Stem number increased with age. The five wild study sites lay in chaparral vegetation on predominantly granite substrate. Flowering observations took place in April and May 2013. [Aslan 2015]

Birds and insects at the flowers

The flowers were visited by native bees, predominantly Halictidae, honeybees and hummingbirds. Hummingbirds moved rapidly between flowers and plants. Bees were frequent visitors, and their potential to transfer pollen was assessed through contact with stamens and stigmas. Animal presence in a flower was considered alongside experiments measuring seed production. [Aslan 2015]

The experiments included 156 flowers on 13 plants at wild sites. Comparisons involved flowers accessible to all visitors, flowers enclosed against all pollinators, flowers accessible to insects but enclosed against hummingbirds, and flowers supplemented with pollen from other plants. Enclosures remained until flowering ended, after which fruits and seeds were assessed. This design helped distinguish visitation frequency from reproductive importance. [Aslan 2015]

Seed production

Flowers isolated from visitors produced no seeds. Allowing insect access enabled seed production, while full access by insects and birds resulted in greater production than insect access alone. The result supports contributions from both groups and an additional contribution from hummingbirds. Pollen supplementation of flowers accessible to pollinators did not significantly increase seed number under the study conditions. [Aslan 2015]

The author interprets the results as strong self incompatibility and adequate pollen delivery during the study season. The identities of the plants donating pollen and effective contact with the stigma are relevant to reproduction. Seed production following pollination with another individual’s pollen concerns the studied population. The paper establishes neither a universal visitation frequency nor continuing pollinator availability in subsequent years. [Aslan 2015]

Plants relocated to the arboretum

Plants relocated to Boyce Thompson Arboretum continued to attract insects and hummingbirds. Following open pollination, their seed production was comparable to that of wild material. The arboretum was at a lower elevation and surrounded by a richer assemblage of flowering plants. Visitation and open fruiting were observed there, whereas enclosure treatments were performed at wild sites. The study documents persistence of an important interaction following relocation. [Aslan 2015]

Related articles