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Recovery Strategy for Multi-Species at Risk in Maritime Meadows associated with Garry Oak Ecosystems in Canada (Proposed)

Species Descriptions

1.18 Seaside birds-foot lotus lotus formosissimus

Assessment summary – May 2000

Common name: seaside birds-foot lotus

Scientific name: Lotus formosissimus

Status: Endangered Reason for designation: Few remaining populations and the area of occupancy are declining because of competition from invasive alien plants and rabbits.

Occurrence: British Columbia

Status history: Designated Endangered in April 1996. Status re-examined and confirmed in May 2000. May 2000 assessment based on new quantitative criteria applied to information from the existing 1996 status report.

1.18.1 The species

Lotus formosissimus Greene is a well-delineated taxon as described in the status report (Ryan and Douglas 1996). Kartesz (1994) does not recognize any intraspecific taxa within this species.

Seaside birds-foot lotus is a sprawling perennial (20-50 cm) from stolons or rhizomes. The alternate leaves are pinnately compound with 5 (usually) round to egg-shaped leaflets. The flowers are umbels of 3-9 pink and yellow pea-like flowers. Few seeds are found in the linear to oblong pods. Seaside birds-foot lotus can be distinguished from other Lotus species by the large membraneous stipules on the leaves, perennial habit, and by the yellow and pink colour of the flowers (Douglas et al. 1999a; Ryan and Douglas 1996a).

1.18.2 Distribution

Seaside birds-foot lotus ranges from southern Vancouver Island, south along the Pacific coast to central California (Figure 9). The species is not ranked (SNR) in Washington, Oregon and California (Natureserve 2004). The Canadian populations are disjunct, by about 160 km, from the next nearest populations on the west coast of central Washington State.

In Canada, the historical and current range of seaside birds-foot lotus encompassed approximately a narrow coastal fringe about 60 km long but only about 50 m deep, hence extent of occurrence never exceeded about 3 km². The COSEWIC status report estimates the area of occupancy to be 155  although recent estimates place the total area of occupancy in Canada at under 200 .

Figure 9. Global and Canadian distribution of seaside birds-foot lotus
(Global distribution on left with uncertain distribution in Baja California; Canadian distribution on right with stars showing location of disjunct population of uncertain status)
Figure 9. Global and Canadian distribution of seaside birds-foot lotus (Global distribution on left with uncertain distribution in Baja California; Canadian distribution on right with stars showing location of disjunct population of uncertain status)

1.18.3 Population and distribution trend

The COSEWIC status report describes two extant populations, one historical population and two populations that were presumed extirpated. Subsequent, fieldwork has confirmed five populations of seaside birds-foot lotusin Canada and one presumed extirpated (BC Conservation Data Centre 2004).

The COSEWIC status report estimates a total population size of 193 plants. Subsequent surveys (Table 17) of some populations indicated that the total Canadian population number between 350 and 600 plants. The precise size of most populations cannot be determined without destructive sampling.

Table 17. Population information for seaside birds-foot lotus in Canada
PopulationLand tenureData from Status ReportSubsequent Data
DateObserver# PlantsDateObserver# Plants
Trial IslandPopulation occurs on all three land tenures on Trial Island. These consist of provincial lands designated as an ecological reserve, provincial lands leased to a radio-communications corporation, and federal lands managed by Canada Coast Guard1992Douglas282004Fairbarns100-200
William HeadFederal lands managed by Corrections Canada1953Hardypresumed extirpated2004Fairbarns7
Rocky PointFederal lands managed by Department of National Defence1993Ryan1652004Fairbarns25
Bentinck IslandFederal lands managed by Department of National Defence1977Ceskaunknown2002Fairbarns45-55
Church PointFederal lands managed by Department of National DefenceNot reported2002Fairbarns200-300
Foul Bayunknown1912Macoununknownextirpated

1.18.4 Biotic and abiotic features of habitat

The habitat of seaside birds-foot lotus consists of mesic maritime meadows. The COSEWIC status report provides information on ecosystem structure, which has been supplemented with recent vegetation sampling (Fairbarns pers. obs. 2004). These meadows are less than 30 m above sea level. Their soils are over 20 cm deep and remain moist throughout the winter months but dry almost to the permanent wilting point by late summer. The sites have never been ploughed or hayed, but some have been lightly grazed and most probably burned frequently in the past.

A sparse canopy of Garry oak (Quercus garryana), logepole pine (Pinus contorta), arbutus (Arbutus menziesii) and/or Douglas-fir (Pseudotsuga menziesii) may be present but trees are generally absent due to wind exposure, salt spray and the droughty nature of the shallow soils. Native shrubs are usually sparse or absent although snowberry (Symphoricarpos albus), Nootka rose (Rosa nutkana)and salal (Gaultheria shallon) are sometimes present. These shrub species often form dense thickets at the edge of populations of seaside birds-foot lotus and may advance into the populations in moist years, presenting a threat to the species. Wildfires and First Nations burning may have formerly constrained the advance of these low shrub thickets at some sites. Alien, invasive shrubs such as Scotch broom (Cytisus scoparius), and to a lesser extent gorse [Ulex europaeus] and spurge laurel [Daphne laureola]) are sometimes abundant. These alien species will probably invade the more sheltered locations of seaside birds-foot lotus in the absence of continuing control activities.

A mix of native and introduced species typically dominates the herb layer. The leading native species are forbs (small-flowered birds-foot trefoil [Lotus micranthus], Spanish clover [L. unifoliolatus], two-coloured lupine [Lupinus bicolor], long-spurred plectritis [Plectritis macrocera], dwarf owl-clover [Triphysaria pusilla]), although native graminoids (blue wildrye [Elymus glaucus], California oatgrass [Danthonia californica], long-stoloned sedge [Carex inops]) may be present.

Introduced grasses (common velvetgrass [Holcus lanatus], Kentucky bluegrass [Poa pratensis], sweet vernalgrass [Anthoxanthum odoratum], orchard grass [Dactylis glomerata], soft brome [Bromus hordeaceus], barren brome [Vulpia bromoides], hairgrass [Aira spp.]), are usually more abundant than introduced forbs (ribwort plantain [Plantago lanceolata], hairy cat's ear [Hypochaeris radicata], smooth cat's ear [H. glabra], hawkbit [Leontodon spp.], common vetch [Vicia sativa], and small hop-clover [Trifolium dubium]).

Mosses and lichens are usually sparse in extent, but Dicranum scoparium and Cladonia portentosa are occasionally abundant, especially where the seaside birds-foot lotus grows in the shelter of boulders and shallow outcrops.

1.18.5 Annual cycle

The COSEWIC status report provides information on the annual cycle of seaside birds-foot lotus, which has been supplemented from a subsequent study of plants on Trial and Bentinck Island and casual observations from other Canadian sites (Fairbarns in. prep. b.).

Germination occurs in March, April and May depending on weather events and site characteristics.

Established plants resprout after the summer/fall drought. Buds on the buried root-crown break dormancy as early as September if there are late summer rains that moisten the soil. Shoots may emerge from the soil by late September or early October.

In typical years, however, the soil doesn't become sufficiently moist to trigger bud break until mid-autumn, at which point cool temperatures retard shoot growth. Early shoot growth occurs underground or below the surface layer of moss and plant litter and shoots don't begin to emerge until late February or March.

Flowering peaks in May and June and most plants bear mature fruit by July. Seed dispersal begins in July, as plants begin to wither, and continues into August, well after most of the foliage has died back. Plants on dry microsites may die, flower, fruit and die-back earlier, but their fruit are often aborted or they bear smaller seeds with less endosperm.

Vegetative growth, flowering and fruiting may be slightly prolonged if unusual summer rainfall events delay the summer drought, but most plants are dormant between mid-August and December.

1.18.6 Biologically limiting factors

Seedling mortality is high, with few plants surviving their first dormant (summer) season. Survivors grow slowly and do not flower in their first year. It is not clear how long plants take to flower.