Small-flowered sand-verbena COSEWIC assessment and status report: chapter 18

Range of Occurrence in Canada:

Alberta, Saskatchewan

extent of occurrence (EO )(km²) :

9.7 km²

specify trend (decline, stable, increasing, unknown) :

Decline (one extirpated population)

are there extreme fluctuations in EO (> 1 order of magnitude)?

no

area of occupancy (AO) (km²)

< 1 sq. km

specify trend (decline, stable, increasing, unknown) :

decline

are there extreme fluctuations in AO (&gt; 1 order magnitude)?

No but visible presence of plants is dependent on degree of precipitation each year

number of extant locations :

8

specify trend in # locations (decline, stable, increasing, unknown) :

decline

are there extreme fluctuations in # locations (&gt;1 order of magnitude)?

no

habitat trend:  specify declining, stable, increasing or unknown trend in area, extent or quality of habitat :

decline in available habitat.

generation time (average age of parents in the population) (indicate years, months, days, etc.) :

one year (annual).

number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values)

<4000 (3156 counts and estimated)

total population trend:  specify declining, stable, increasing or unknown trend in number of mature individuals :

Uncertain (fluctuating numbers)

if decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period)

are there extreme fluctuations in number of mature individuals (&gt; 1 order of magnitude)?

yes

is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., &lt; 1 successful migrant / year)?

yes

list each population and the number of mature individuals in each

• Alberta
  • Lower Bow, 789
  • Purple Springs, 269
  • Grassy Lake, 1797
  • N of Medicine Hat, 100 est.
  • N of Medicine Hat  (Suffield), 100
  • Lost River, 100 est.
  • Suffield Nat. Wild. Area, 1
  • Wolf Island, extirpated?
• Saskatchewan
  • 1site, none recently

specify trend in number of populations (decline, stable, increasing, unknown) :

decline

are there extreme fluctuations in number of populations (&gt;1 order of magnitude)?

fluctuation primarily due to dormancy under drought conditions

does species exist elsewhere (in Canada or outside)?

Western U.S.

status of the outside population(s)?

Kansas (S1), Nebraska (S1), California (S1.3), Wyoming (S3), South Dakota (SH)

is immigration known or possible?

not likely due to disjunction

would immigrants be adapted to survive here?

unknown

is there sufficient habitat for immigrants here?

possibly