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Sand-verbena Moth (Copablepharon Fuscum)

Limiting Factors and Threats

The following factors are important for contextualizing the limiting factors and threats to Copablepharon fuscum in Canada:


Habitat Loss

The primary threat to C. fuscum is the reduction in the quantity and quality of host-plant resources as a result of loss of, or change to, open sand habitats. As noted previously, this is primarily caused by vegetation stabilization. Direct disturbance from human development and recreational use are considered secondary threats but may have substantial local impacts. Long-term maintenance of C. fuscum populations will require chronic natural disturbance to maintain Abronia latifolia populations in open sand areas or new sand deposition in which seedling colonization can occur.


Host-plant Specificity

Host-plant specificity may be an important measure of extinction risk in moths (Nieminen, 1996). Indeed, Nieminen (1996), noted: “the pattern of population extinction in moths is affected by host-plant characteristics rather than by the characteristics of the moths themselves”. He found that monophagous moths were more likely to suffer extirpation or extinction than polyphagous species.


Collecting

The collecting of specimens has likely had a very minor effect on total population size in C. fuscum. However, research collections should avoid unnecessary or concentrated collecting. Recreational collecting is inappropriate.


Population Structure

C. fuscum populations are spatially isolated. Ecological theory predicts that population extinction risk is reduced with increasing numbers of subpopulations (Hanski, 1982). This outcome is generally related to the “rescue effect” that allows multiple populations to avoid stochastic or deterministic extinctions through immigration. It relies on the dispersal ability of species to allow recolonization following population extirpation. As noted previously, it is unclear if between-site dispersal is important for C. fuscum population persistence. It is unlikely that recolonization from known US populations could occur naturally if Canadian populations were extirpated.


Btk

Btk is a commercial pest-control product used to control North American gypsy moth (Lymantria dispar). It uses spores of a naturally occurring pathogenic bacteria ( Bacillus thuringiensisvar. kurstaki) applied aerially to kill target and nontarget butterflies and moths as larvae. It has been used in the Victoria and Vancouver area on a localized basis. It has not been used near C. fuscum populations to date, but it could pose a serious risk.


Climate Change

The potential effects of climate change on C. fuscum are complex. Climate change may be associated with sea-level rise which could threaten coastal dune habitats directly. However, accelerated coastal disturbance and sediment transport associated with increased storm frequency may result in increased development of open sand habitats, which would have a positive effect.


Conservation Concerns in Similar Species

It is noteworthy that a closely related species, Copablepharon hopfingeri Francl., is the only moth species known to have been extirpated from western Canada (Lafontaine and Troubridge, 1998). It historically occurred in a small site with sandy soils at Brilliant, B.C. (near Castelgar). This loss may indicate that other Copablepharon species are similarly sensitive to habitat change.

Copablepharon longipenne Grote occurs on unstable dune systems on the northern Great Plains. As a result of extensive agriculture and control of prairie fires, this habitat has been drastically reduced in the last century (J. Troubridge, pers. comm., 2002). The moth is still common on the Great Sand Hills of southwestern Saskatchewan, where grazing by cattle has helped to retard stabilization of these dunes (J. Troubridge, pers. comm., 2002). All known Copablepharon species are associated with sandy, dune habitats. Three species occur (or did so) in Alberta and Saskatchewan: Copablepharon grande (Strecker), C. longipenne and Copablepharon viridisparum (Dod).

The Canadian distributions of several other species of noctuid moths (Apamea maxima (Dyar), Oligia tusa (Grote), Trichoclea edwardsii Smith, Lasionycta wyatti (Barnes & Benjamin), Lasionycta arietis (Grote), Agrotis gravis Grote and Euxoa wilsoni (Grote)) are restricted to coastal beaches in British Columbia (Troubridge and Crabo, 1996). Although restricted to coastal beaches, the global distribution of these species is much greater than that of C. fuscum: A. maxima, O. tusa, L. wyatti, L. arietis, E. wilsoni and A. gravis occur commonly on beaches from central California to British Columbia and persist despite stabilization of the dunes on the outer coast. T. edwardsii occurs on coastal and interior dunes in southern California, is apparently absent from the outer coast of northern California, Oregon, Washington and British Columbia, but occurs with C. fuscum on sandy beaches within the Strait of Georgia and Puget Sound.