UC specimens and range limits for Dictyoneurum californicum

• Blue markers: specimen records
• Yellow marker: type locality, if present
• Red markers: endpoints of range from literature

View map from the Consortium of Pacific Northwest Herbaria

Notes: Ranging from southern Vancouver Island, British Columbia, Canada to Jalama Beach, Santa Barbara Co., Calif. (just north of Point Conception)

Status: Recent molecular and developmental studies have shown that there are indeed two species in the genus (H. Kawai, pers. comm.). There is a continuum of forms so that it is sometimes difficult to distinguish the two species in the field.

Habitat: Low intertidal to shallow subtida, in exposed habitats

Life History: Alternation of heteromorphic phases (large diploid sporophyte and microscopic haploid dioecious gametophytes)

Search Sequences in GenBank

Illustration from DeCew's Guide to the Seaweeds of British Columbia, Washington, Oregon, and Northern California

Dictyoneurum Ruprecht 1852

Sporangial thalli perennial, gregarious. Stipe markedly flattened, prostrate, with forked haptera along lateral margins. Stipes rarely with more than 2 or 3 dichotomies, owing to progressive death and decay at lower end. Ultimate dichotomies of stipe upwardly bent, dividing dichotomously, each continued in a single blade, this splitting longitudinally from base to apex into 2 blades, 1 borne on each arm of new dichotomy. Blades linear, without midrib, both flattened surfaces covered with irregular reticulum of narrow ridges. Sporangia in irregularly shaped, inconspicuous sori, these produced on both flattened surfaces of blade.

Dictyoneurum californicum Rupr.

Ruprecht 1852: 80; Setchell & Gardner 1925: 622; Smith 1944: 139.

Sporangial thalli 0.5-2(4) m tall, light to dark yellowish-brown, in gregarious clumps, 25-100 per clump; blades 4-8 cm broad, linear, gradually tapering at both upper and lower ends, with or without marginal denticulations; reticulations on surface of blade more or less rectangular and in longitudinal series; upward splitting of blade into 2 blades frequent; sporangial areas first appearing during midsummer, darker in color than vegetative areas.

Locally frequent, saxicolous, low intertidal (where more or less directly exposed to surf) to subtidal (10 m), Vancouver I., Br. Columbia, to Pt. Conception and Channel Is., Calif; common on Monterey Peninsula, less frequent elsewhere in Calif. Type locality: Fort Ross (Sonoma Co.), Calif.

Excerpt from Abbott, I. A., & Hollenberg, G. J. (1976). Marine algae of California. Stanford University Press, Stanford, California. xii [xiii] + 827 pp., 701 figs.

Notes: No collections from the Channel Islands can be found in herbaria. The documented southern limit is Jalama Beach, just north of Point Conception.