A high-Arctic population of Pyla fusca (Lepidoptera, Pyralidae) on Svalbard?
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- Cite this article as:
- Coulson, S.J., Hodkinson, I.D., Webb, N.R. et al. Polar Biol (2003) 26: 283. doi:10.1007/s00300-002-0475-7
Observations of Lepidoptera on Svalbard for which locations are recorded
Plutella xylostella (L., 1758) (Yponomeutidae)
Recherchefjord (Belsund), Storholmen and southern shore (Kongsfjord), Adventdalen and Colesbukta (Isfjord), Reinsdyrflya (Liefdefjorden), St. Johnsfjord, Isfjord, Semeldalen (Van Mijenfjord), Eckmanfjord, Sorgfjord
Hofmannospila pseudospretella (Stainton, 1849) (Oecophoridae)
Kaisila (1973) (and references therein)
Pyla fusca Haworth, 1811 (Pyralidae)
Aagaard et al. (1975); G.W. Gabrielsen, personal communication (probable sightings July 2000, 2001)
Pieris napi (L., 1758) (Pieridae)
Kaisila (1973) (and references therein)
Vanessa cardui (L., 1758) (Nymphalidae)
Grumantbyen (Isfjord), Sassendalen (Sassenfjord)
Lokki et al. (1978)
Syngrapha interrogations (L., 1758) (Noctuidae)
Gåsebu (southern shore, Kongsfjord)
Sendstad et al. (1976)
Apamea maillardi (Geyer, 1834) (=zeta ssp. exulis) (Noctuidae)
Brøggerhalvøya, Ossiansarsfjellet (Kongsfjord), Adventdalen (Isfjord)
The collection site and observations
On both dates, weather conditions were warm, with high broken cloud and no, or a slight, easterly breeze. Moths were active and abundant, flying close to the ground but occasionally reaching up to 2 m. However, Pyla fusca was not noted during a short visit on 13 July 2002 despite similar weather conditions. Moreover, despite intensive searching, no moths were seen at other vegetated sites in Kongsfjord, including Blomstrandhalvøya (30 July; similar warm, still day), the southern shore of Kongsfjord (including well-developed vegetation under bird cliffs at Krykkjefjellet and Stuphallet) between 4 July and 1 August, or amongst vegetation under bird cliffs at Casimir-Périerkammen (Krossfjord) in warm but overcast conditions on 14 July.
Large numbers of Pyla fusca were observed within a small area at Ossiansarsfjellet. Their distribution in Kongsfjord was extremely restricted and adults were not seen elsewhere. This contrasts with observations of the migrant species, Plutella xylostella, during 2000, when large numbers of immigrant moths were observed and collected at many sites along the southern shore and the islands (Storholmen) of Kongsfjord (Coulson et al. 2002). No such immigration event was observed in 2002. Furthermore, there are isolated previous records of Pyla fusca from Ossiansarsfjellet over the last 30 years (Table 1), but not from elsewhere in Kongsfjord or Svalbard in general.
Local topography at the collection sites on Ossiansarsfjellet, which faces southwest, gives a relatively mild microclimate compared with north-facing localities. The high central region of Ossiansarsfjellet shelters the collection sites from cold easterly winds descending from the Krone and Kongsveg glaciers. Together, the aspect and shelter result in the southwest-facing slopes having the warmest microclimate on Kongsfjord (see Joly et al. 2002). Vegetation species richness and growth are consequentially greater (I. Alsos, personal communication) and the potential for larval growth and development is higher than elsewhere around Kongsfjord. Mikkola (1992 and personal communication) noted that other insect diversity hotspots in the Arctic, such as Lake Hazen, Ellesmere Island, and Kilpisjävi, Finland, are similarly west facing, and with a radiation-reflective water body immediately to the west.
Pyla fusca larvae are known to feed on a range of plants, including Ericaceae and Salix spp. (Wolff 1971; Emmet 1979; Goater 1986). Potential larval food plants, including S. polaris and S. reticulata, are present at Ossiansarsfjellet, where they are abundant and grow more luxuriantly relative to most other sites on Svalbard.
Pyla fusca is resident at other high-latitude locations in northern Scandinavia, Iceland, Greenland and Alaska and with similar emergence and flight times to Svalbard (de Lesse 1951; Heinrich 1956; Wolff 1964, 1971; Karsholt and Razowsky 1996).
Pyla fusca was observed on several occasions in July 2002 along the southwest shore of Ossiansarsfjellet, West Spitsbergen, Svalbard, but was apparently absent at other locations along the coasts of the fjord. The high population density and restricted distribution, combined with sporadic earlier records, suggest that this is a breeding colony rather than an immigrant population, and may have been present for at least 30 years. The microclimate at the site is amongst the warmest around Kongsfjord and suitable larval food plants are present. It seems probable that Pyla fusca is one of few Lepidoptera to have colonised Svalbard successfully and represents one of the most northerly records for a breeding population of Lepidoptera.
We thank B. Goater for identification of the specimens and K.T. Hansen (Svalbard Science Forum) for collecting the initial specimen on 9 July 2002. The eight specimens examined critically are deposited in the Natural History Museum, London. P.C. was supported under the EU-LSF scheme (NP-65/2001).