Beach pinweed (Lechea maritima) COSEWIC assessment and status report: chapter 2

Species Information

Beach pinweed (Lechea maritima) is an herbaceous perennial in the family Cistaceae. The Canadian populations have been recognized as a unique variety, the Gulf of St. Lawrence beach pinweed (Lechea maritima var. subcylindrica). Since this is the only variety of Lechea maritima in Canada, this report documents the status of the Canadian populations at the species level and only refers to the var.subcylindrica when necessary for clarity. The species occurs on stable coastal sand dunes. Prostrate, densely leafy basal shoots develop from the woody base, often forming a rosette, and the fruiting stems are (10) 20-35 cm tall, usually erect and strongly branched. Plants flower in mid- to late summer and develop fruit in late summer and early fall. The numerous, inconspicuous flowers (2-4 mm wide) have three short-lived, reddish-brown petals. The fruit is a round, 3-valved capsule (1.8-2.1 mm long) usually shorter than the sepals, splitting open lengthwise to the base. The seeds, generally 4-5 per capsule, are smooth and 1-1.1 mm long, and without obvious adaptations for dispersal. Beach pinweed is best distinguished from the other pinweed in its range (narrowleaf pinweed, Lechea intermedia) by the densely white-hairy undersides of its basal leaves and by its smooth seeds.

Distribution

Beach pinweed is globally secure and occurs primarily along the Atlantic coast from New Brunswick to North Carolina. Reports from Ontario and Quebec are unsupported and likely erroneous. Gulf of St. Lawrence beach pinweed is globally rare and endemic to New Brunswick’s eastern coast and Prince Edward Island’s northern shore, 370 km disjunct from the nearest occurrence of varietymaritima in southern Maine. On Prince Edward Island, populations occur on over 41 km of shoreline, with a single occurrence 54 km west. In New Brunswick, the northern and southernmost occurrences are spread over an 87 km straight-line distance. The species’ Extent of Occurrence is 176 km²(sum of distances between population extremities along coastal shorelines in NB and PE times 1 km width) and its Area of Occupancy is 71 km² based on occupied 1 km grid squares or 152 km² using a 2 x 2 km grid.

Habitat

Beach pinweed is restricted to large, stable barrier dune systems, usually in open, dry habitats. It is apparently unable to tolerate highly active dune sections and is typically found in comparatively sheltered sites, often with the low shrub beach heather (Hudsonia tomentosa), a strong indicator of potential habitat. It is also found locally in open jack pine–red pine woodland on old dunes but these populations are small and limited to the most open woodland, suggesting that this habitat may be suboptimal.

Biology

The species is perennial from a stout, woody taproot, forming rosettes of prostrate basal shoots and sending up 1-5 flowering stalks. Reproduction is by seed, and dispersal is probably primarily by wind and water. Wind pollination is suspected but insect pollination is also possible. Lechea has been reported as primarily self-pollinating but unconfirmed suggestions of hybridization would indicate cross-pollination. Under certain conditions it can reproduce at very small sizes in its second or perhaps its first season, but most plants appear to be significantly older. Generation time is not well known, but is estimated here at 8-10 years.

Population Sizes and Trends

The total population in Canada is estimated at 181 000 plants in 15 populations within five areas, with little genetic exchange likely between those five areas. There is no direct evidence on long-term trends but five historic sites, discovered between 1892 and 1932, are still extant. At least one site has experienced recent minor declines due to storm damage, and storm frequency and intensity are likely to increase with climate change. Minor losses to ATV traffic and trampling have been noted at a few sites, and succession may be an issue at the two sites with forest cover.

Limiting Factors and Threats

The species is naturally limited by its highly specialized habitat. Sea-level rise and climate change-induced increases in storm frequency and intensity could be a long-term threat to the species and its habitat, given that much of the population is under 5 m elevation, and storm-caused decline in habitat quality has been noted at the lowest elevation sites supporting the majority of the population. It is not possible, however, to quantify climate change - related threats with any precision. Minor losses to ATV traffic and trampling have been noted at a few sites, and succession may be an issue at the two sites with forest cover. It is relatively well-protected from shoreline development by protected areas, provincial regulation and remoteness of occurrences.

Special Significance of the Species

Beach pinweed, when recognized as a distinct Canadian variety, is a globally rare endemic restricted to a very limited area, and is 380 km disjunct from the variety maritima plants from which it evolved. It is one of a number of southern species with disjunct occurrences on the relatively warm Gulf of St. Lawrence. No evidence of First Nations use of the plant or of any other human use was found.

Existing Protection or Other Status Designations

Beach pinweed has no existing legal protection, although it benefits from provincial laws and regulations governing development and limiting activity in coastal areas. Seven of 15 populations are protected in Kouchibouguac and Prince Edward Island National Parks, Portage Island National Wildlife Area, Bouctouche Dune and Cabot Beach Natural Area. Four other sites are on provincial (two Conway Sandhills populations) or federal land (two Hog Island populations, on land held in trust for the Lennox Island First Nation). The species is ranked globally as G5T1 (secure as a species but the variety is critically imperiled), although revision to G5T2 could be warranted because of recent fieldwork. It is ranked S1 (critically imperiled) and May be at risk in New Brunswick and Prince Edward Island, meaning it would receive consideration in provincial and federal environmental impact assessments.

In total, about 33% of the habitat containing the species is within protected areas.