Seaside centipede lichen (Heterodermia sitchensis) COSEWIC assessment and status report: chapter 10

Technical Summary

Heterodermia sitchensis

Seaside centipede lichen – hétérodermie maritime

Range of Occurrence in Canada:

British Columbia

Extent and Area information

extent of occurrence (EO) (km²)

< 5000 km²

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

Unknown

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

No

area of occupancy (AO) (km²):

875 m² Footnotee

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

Unknown

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

No

number of extant locations:

10 in Canada (1 USA)

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

Original 2 popns lost; 10 new popns; fugitive life history strategy

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

No

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

Unknown, but probably stable

Population information

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

10-15 years

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

211 thalli

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

possibly declining based on Table 3

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

Original 2 popns lost, but 10 new pops. found

are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?

No

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., < successful migrant / year)?

Probably

list each population and the number of mature individuals in each:

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

Unknown

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

Unknown

Threats (actual or imminent threats to populations or habitats)

Logging, winter storms, collection of kindling by recreationists, recreation pressure and development

Rescue Effect (immigration from an outside source)

does species exist elsewhere (in Canada or outside)?

Yes

status of the outside populations(s)?

Extant

is immgration known or possible?

Unlikely

would immigrants be adapted to survive here?

Probably

is there sufficient habitat for immigrants here?

Yes

Quantitative Analysis

Not available

Status and Reasons for Designation

Status:  Endangered

Alpha-numeric code:  D1

Reasons for Designation: This is a foliose lichen restricted to shoreline Sitka spruce trees on the west coast of Vancouver Island. It has been documented from only ten locations in Canada, 11 worldwide. It requires high levels of nitrogen, so is restricted to sites subject to nitrogen enrichment, for example, sea lion haul-out sites and bird nest sites. The species may have poor dispersal abilities. It is highly vulnerable to tsunamis, and intensified winter storm activity associated with global warming.

Applicability of Criteria

Criterion A: (Declining Total Population): Does not apply.

Criterion B: (Small Distribution, and Decline or Fluctuation): The criterion is not met. Sub-criteria B1 and 2 both apply for Endangered. Sub-criterion “a” is met for Endangered as the species is probably severely fragmented. However, for sub-criterion “b” a continuing decline could not be demonstrated in part because the species has a fugitive life history strategy.

Criterion C: (Small Total Population Size and Decline): The criterion is not met. Though there are only 227 thalli known, continuing declines cannot be demonstrated.

Criterion D: (Very Small Population or Restricted Distribution): The criterion is met for Endangered as there are 227 thalli known.

Criterion E: (Quantitative Analysis): Not available.

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