Macoun’s meadowfoam (Limnanthes macounii) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Macoun's meadowfoam is endemic to southern Vancouver Island and some adjacent islands in British Columbia, Canada (Figure 3).

In March 1998 Eva Buxton found a large population of a plant identified as Macoun’s meadowfoam near Moss Beach, San Mateo Co., California (Buxton & Ornduff 1999, Ceska & Ceska 1999), where it is abundant on ca 9 ha of a seasonally fallow [cabbage] field. The Californian plants differ from Vancouver Island plants in their morphology (they are more erect and more robust than British Columbian plants, their leaves are usually double pinnate) and in their physiology (they are not as hardy as Vancouver Island plants and flower about a month earlier, in common garden experiments) and they most probably represent a new, yet undescribed taxon (Eva Buxton, pers. comm.).

Canadian range

Macoun’s meadowfoam occurs only in southwestern British Columbia, on Vancouver Island and several adjacent islands (Figure 4). Its known range extends from East Sooke Park eastward to Victoria (including adjacent islands of Inskip, Chatham and Trial), to Yellow Point, the Gulf Islands (Saltspring, and Gabriola), and Hornby Island. The northernmost known location is on Hornby Island. The area of distribution is linear, which is typical for plants that grow close to the ocean. The majority of localities are on coastal bluffs not farther than 200 metres from the coastline. The exceptions are populations in the Montreul Hill area [10]^Footnote1, Pearson's College [9] and Government House [19] that are all within about two kilometres of the shore. On Montreul Hill they reach almost 200 m elevation [10.4].

The core of Macoun's meadowfoam distribution is between East Sooke Park in Sooke and Gordon Head in Victoria, 33 km apart. There is a 30 km gap between Gordon Head and Saltspring Island populations and 40 to 46 km gap between Saltspring Island and Yellow Point/Gabriola Island populations, respectively. The northernmost locality is that on Hornby Island and that locality is 80 km from the closest known locality, i.e., the one on Gabriola Island. It is difficult to calculate the extent of occurrence in this linear type of distribution. The extent of occurrence is about 40 km² (coastal strip about 200 km long and about 0.2 km wide).

Because of the lack of any active dispersal mechanism of meadowfoam nutlets, many subpopulations are smaller than 1 m²; largest subpopulations can reach up to 200 m². The total area of occupancy is very small, probably not more than one or two hectares (0.01-0.02 km²).