UC specimens and range limits for Eisenia arborea

• 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: Remarkably disjunct distribution between British Columbia, Canada (Haida Gwaii [53.378333, -132.52166] and Vancouver Island) and California, where it occurs at Pescadero, San Mateo Co., Point Lobos and the deep water community of southern Monterey Co. (Spalding et al. 2003), with another apparent disjunction to south of Point Conception, where it is common in Santa Barbara, Ventura, Orange, Los Angeles, and San Diego counties through Baja California, Mexico. As Spalding et al. (2003) note: "If equatorial submergence were a general phenomenon, one would not expect E. arborea to be abundant in deep water in central California." Common at Santa Barbara, Santa Catalina, San Clemente islands; also at Anacapa, Santa Cruz, Santa Rosa, San Miguel, and San Nicolas islands.

Status: This species is easy to identify.

Habitat: Growing in the low intertidal to subtidal, often forming large aggregations on rock or tops of pinnacles. Deep water populations at 30m, genetically distinct from shallow at Santa Catalina Island (Roberson & Coyer 2004).

Life History: Alternation of heteromorphic phases (large diploid sporophyte and microscopic haploid dioecious gametophytes). Perennial. Juveniles are single blades, with teeth near the base and lateral, toothed marginal lobes.

Search Sequences in GenBank

Eisenia Areschoug 1884

Sporangial thalli with holdfast of dichotomously branched haptera. Stipe elongating and persistent, bifurcate above, the 2 apparent branches actually the thickened lower margins of the original and subsequently eroded terminal blade. Small partial blade persisting at outer extremity of each false stipe throughout life of plant, this giving rise to numerous sporophylls along lower outer margin.

Egregia menziesii (Turn.) Aresch.

Fucus menziesii Turner 1808: 57. Egregia menziesii (Turn.) Areschoug 1876: 67; Setchell & Gardner 1925: 647; Smith 1944: 149. E. menziesii ssp. insularis Silva 1957b: 45. E. laevigata Setchell 1925: 648; Smith 1944: 150. E. laevigata f. borealis Setch. 1925: 649. E. laevigata ssp. borealis (Setch.) Silva 1957b: 46. E. planifolia V. Chapman 1962: 36.

Whole sporangial plant with conspicuous stipe topped by numerous blades and sporophylls. Holdfast stout, much branched, the branches intertwined but compact; stipe nearly terete at base, becoming much flattened above, very dark brown, almost black, 1-2 m long, rough and rigid, the upper portions containing many mucilage ducts; blades entire when young, later becoming toothed along margins and (with age) corrugate on surface; blades of mature plants golden olive, more or less longitudinally grooved, lanceolate with variable denticulations along margin, some of these to 4+ cm long, 1 cm broad; sporophylls borne on partial blades, 30-50 per blade; sori irregular in shape, covering most of surface of each sporophyll. Saxicolous, forming dense subtidal "groves," low intertidal to subtidal (10 m), Vancouver Island, British Columbia, Monterey region, Santa Catalina Island (type locality), Calif., and from S. Calif. to Isla Magdalena, Baja 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: Blades may be grooved (bullate) and wide in low flow environments (often deeper), or narrow, thicker and smooth in areas with high water motion (shallow sites). Stipes are usually hollow in the southern parts of its range but not the northern (Matson & Matthews 2006).