Grand coulee owl-clover (Orthocarpus barbatus) COSEWIC assessment and status report: chapter 9

Population sizes and trends

There are four locations for Orthocarpus barbatus in Canada, all in the southern Okanagan Valley and the southern Similkameen Valley (Figure 3, Table 1). Population numbers range from 185 to 8000 on areas of 22 m2 to 2000 m2. Population trends are not well known. Only one site (Mount Kruger, above the racetrack) has data from more than several years. At this site, a subpopulation had ca. 200, 1200 to 1500, 153 and 222 plants in 1995, 1997, 2003 and 2004, respectively. At the Kilapoola site (Subpopulation 1), plant numbers and the area covered increased by 100% between 2003 and 2004. It may be assumed that these fluctuations are natural and due to the annual nature of the genus. Atsatt (1970) observed that patterns of abundance and distribution in populations of grassland Orthocarpus show sizeable year-to-year fluctuations within sites. Wide population fluctuations are typical in many annual species and such fluctuations may obscure population trends, especially if the increase in shoot numbers occurs through seed bank depletion.

 

Table 1. Locations and population/subpopulation sizes for Orthocarpus barbatus in British Columbia.
Population Last Observation Observers Number of Plants/Area
Mt. Kruger, above golf course 1997 Lomer Unknown
“Veronica Lake” 2002 Penny & Donovan 367/1800 m2
Mt. Kruger, above racetrack, Subpopulation 1 2004 Douglas & Smith 222/22 m2
Mt. Kruger, above racetrack, Subpopulation 2 2004 Douglas & Smith 3000-3500/245 m2
KilpoolaLake area, Subpopulation 1 2004 Douglas & Smith 5000-8000 /2000 m2
KilpoolaLake area, Subpopulation 2 2004 Douglas & Smith 185/57 m2
KilpoolaLake area, Subpopulation 3 2004 Douglas & Smith 300/484 m2

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