Corispermum is a genus of annual herbs in the family Amaranthaceae (order Caryophyllales), commonly known as bugseeds or tickseeds. The genus was formally described by Linnaeus in 1753 (Species Plantarum 1: 4).
Plants are erect or ascending annuals, rarely prostrate, with branched stems bearing dendroid (tree-like) or occasionally stellate hairs that sometimes disappear at maturity. Leaves are alternate and sessile, ranging from lanceolate to linear or filiform in outline, flat or convolute, with entire margins and an acute apex. The characteristic inflorescences are terminal spikes in which solitary bisexual flowers are borne in the axils of leaflike bracts. Each flower has one to three small scalelike perianth segments (or none at all), one to five stamens, and a superior ovary with two styles. The fruit is a lenticular achene with a distinctive bifid rostrum ("beak") formed by the persistent style bases; achenes may be winged or wingless and vary from ovate to orbiculate. Seeds are vertical with a horseshoe-shaped embryo and abundant perisperm. The base chromosome number is x = 9.
The genus is distributed across arid and semi-arid regions of Asia, with additional species in temperate and subarctic zones; native populations have also been documented in North America since at least 38,000 years before the present based on fossil and radiocarbon evidence. Mature fruits are essential for reliable identification within the genus, and species limits remain uncertain owing to limited experimental taxonomic and ecological research.
Etymology
The name Corispermum derives from the Greek koris (a bug or tick) and sperma (seed), alluding to the flattened, tick-like appearance of the achenes — hence the common names "bugseed" and "tickseed."
Distribution
Corispermum is most abundant in the arid regions of Central and East Asia, particularly Siberia, with species extending into temperate and subarctic zones. In North America, the genus has been present since at least 38,000 years before the present (confirmed by radiocarbon dating of fossil material in Alaska, the Yukon, Arizona, Utah, and New Mexico). Several species have also spread as introductions well beyond their native ranges.
Ecology
Species of Corispermum are characteristic plants of open, disturbed, sandy, and arid habitats, including river sandbars, dunes, steppe margins, and semi-arid scrublands. Some species tolerate subarctic conditions. Certain taxa have become naturalised as weedy introductions on disturbed ground far outside their native ranges.
Taxonomy Notes
Corispermum was long thought to be entirely introduced to North America from Eurasia, but fossil pollen and accelerator radiocarbon dating have firmly established native pre-Columbian populations. Native North American species are most closely allied to eastern Asian (especially Siberian) taxa rather than to European ones. Species boundaries within the genus remain poorly defined; a narrow species concept is followed in the Flora of North America treatment, though the authors note that precise natural boundaries and phylogenetic links await further experimental and field studies. Reliable identification requires mature fruiting material.
