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Geographic Range

G. groenlandica is endemic to the Canadian Arctic Archipelago and Greenland, above 70 degrees North latitude. It is known as one of the most northern members of the Lepidoptera order in the Northern hemisphere. It is officially classified as a High Arctic endemic species. Data published in December 2013 presented the first records of G. groenlandica south of the arctic circle, in alpine environments in southwest Yukon, 900 kilometers south of their previously established distribution. These populations were subsequently designated as the subspecies G.g. beringiana.

Habitat

G. groenlandica is extremely adapted to living under conditions of extreme heat deficiency in the High Arctic.

Home Range and Territoriality

The G. groenlandica caterpillar moves up to several meters per day. To understand movement for the acquisition of resources, an experiment was performed in which one group of caterpillars was physically transferred between Salix arctica (arctic willow) plants. A second group of caterpillars were individually restricted to a single willow. This arrangement was maintained throughout the active period of the caterpillars, and it was observed that those caterpillars which were moved demonstrated higher herbivory and growth rates compared to the stationary group. This suggests that the acquisition of high quality resources may be a principle motivation for G.groenlandica caterpillars to move from one plant to another.

Food Resources

Host Plant Preferences and Selection

As G. groenlandica spends much of its life as a caterpillar, and 20% of its time feeding, food resources in general apply to its larval stage of development. The primary host plant and source of food for this species is the patchily-distributed Salix arctica, the arctic willow, but larvae can feed on plants of other families, such as the flowers of Saxifraga oppositifolia and the senescent leaves of Dryas integrifolia, although less than 3% of larvae have been found to choose these alternatives. (dark red)

Compared to High Arctic populations, it was found that in lower and warmer sites in Canada,  G. groenlandica exhibits lower consumption of Salix arctica; for instance, the G. groenlandica beringiana subspecies found in the alpine environments of southwest Yukon feed on a broader spectrum of plants than populations of the High Arctic. Furthermore, the highest herbivory in this species was discovered to be at sites of intermediate temperature for its range in Canada. This is attributed to the narrow thermal adaptation of this species, meaning that it is not able to increase its levels of herbivory at warmer sites in its geographical distribution.

While the catkins of S. arctica are rarely eaten by the larvae, they are known to eat its leaves: 97% of larvae which were actively eating at the onset of their feeding season were consuming primarily new leaf buds of this plant. Removal of nitrogen and potassium by the feeding larvae is hypothesized to occur due to nutrient concentrations of the leaves of the plant compared to those in larval frass. Examining the feeding patterns of larvae, it was found that the larvae only fed in June when the young leaves of S. arctica had the highest concentrations of macronutrients and total non-structural carbohydrates, and larvae decreased their food intake towards the end of the month and into the summer, when the energy and nutrient content of the plant, specifically the level of  total non-structural carbohydrates, decreased.

Life History

The life history traits of G. groenlandica are dictated by the short, cold nature of summers in the High Arctic. Due to the restricted seasonal growth period of G. groenlandica, this species has a life cycle that is generally 10 years, but is known to extend to at least 14 years at the Alexandra Fiord lowland and at Ellesmere Island. It is much shorter (2-3 years) in alpine environments. They remain larvae for the vast majority of their lives, with the exception of up to 3-4 weeks of a single summer. While they remain in their larval stage, G. groenlandica experience numerous winter diapauses.

Life Cycle

In general, G. groenlandica caterpillars are characterized as large and densely pubescent, and they have a hair tuft on the eighth abdominal segment. The later instars of the larvae can be characterized by the color patterns of their dorsal hair tufts and the form of their spinulose hairs.

Larval activity is confined to a short period following snowmelt. The High Arctic presents a short growing season of 45-70 days, and the G. groenlandica cease foraging after 3-4 weeks in June, prior to mid-summer. Larvae tend to spend 95% of their time either basking in the sun, feeding, or moving, and only 5% of their time immobile.

At the end of this period, the larvae openly prepare to overwinter by weaving a hibernacula and entering diapause until the subsequent snowmelt. This typically occurs when daytime temperatures are at a maximum of 5-10 degrees Celcius, but in this state they are able withstand temperatures as low as -70 degrees Celcius.

Cocoons of this species are spun on exposed sites such as rocks, and they have silk cocoons of two layers, into which they incorporate larval hairs.

The developmental stages of pupation, emergence, mating, egg laying, eclosion, and molting to the second instar stage are all confined to a period of 3-4 weeks during a single summer, and emergence and reproduction may occur in a 24-hour period.

Because the lifespan of adult, fully mature individuals is so brief, adults are difficult to find in the field.

Enemies

Predators

G. groenlandica has a distinct defense reaction to bat signals.

Parasites

The primary enemies of G. groenlandica are parasitoids, namely Exorista thula and Hyposoter diechmanni. In general, more than two thirds of Gynaephora are killed by parasitoids, and parasitism in G. groenlandica specifically causes more than 50% mortality. The probability of parasitism increases towards the end of the species’ active period, which coincides with declining rates of feeding.

Genetics

Subspecies

While G. groenlandica is generally classified as a High Arctic endemic species, an article published in December 2013 contained the first reports of G. groenlandica in alpine environments. Specifically, two neighboring populations were discovered in southwest Yukon, 900 kilometers south of their previously-defined southern distributive border. Due to the distinct habitat, geography, DNA barcode, and wing phenotype of these two populations, they were classified as a subspecies, G.g.beringiana.

Hybridization

While G. groenlandica is a close relative of G. rossii, the two species are reproductively isolated and no hybridization occurs.

Physiology

Flight

While the females of this species have fully developed wings and can take flight for a short time, they do not usually fly; however, it is worth noting that while Arctic-inhabiting females tend to be flightless, alpine subspecies females are usually more mobile.

Males, on the other hand, tend to fly high, fast, and erratically during the day.

Thermoregulation: Basking, Metabolism, Oxygen Consumption

In general, the period of maximal activity in G. groenlandica occurs during the annual period of maximal solar radiation. During this time, the body temperatures of feeding larvae tend to be similar to those of molting and spinning larvae, while those of “basking” larvae tend to be higher. G. groenlandica larvae spend approximately 60% of their time basking, which is a behavior in which a caterpillar orients its body so as to maximize sun exposure and avoid wind, thus raising its body temperature by up to 20 degrees Celcius. Generally, maximal body temperature is about 30 degrees Celcius. This maximum temperature is generally only reached when larvae lie in midday sun, surrounded by snow, on a day with minimal wind. The preferred angle of orientation is towards the sun and away from the wind, and larvae tend to follow the direct angle of the sun’s rays in order to maintain maximal absorption of sunlight. They do this by orienting perpendicularly to the sun’s angle of insolation.

While larvae utilize solar radiation to promote growth, and basking may therefore increase developmental rates, it may also interfere with other activities such as feeding.When comparing growth rates at 5, 10, and 30 degrees Celcius, respectively, the growth rate was found to be lowest at 5 degrees C and metabolism rates were maximized at 30 degrees. Thus, basking tends to increase body temperature. As body temperature increases, metabolic rate increases exponentially, even when larvae are starved or seemingly inactive. Because feeding larvae tend to have lower body temperatures than basking larvae, their body temperature drops and their maintenance metabolism increases simultaneously. Consequently, larvae tend to feed during the day, when temperatures are highest, and they bask when they can’t reach these higher temperatures (more than 5 -10 degrees Celcius) needed for activity.

Changes in metabolic state and body temperature also affect oxygen consumption. Oxygen consumption was found to be much lower when body temperatures were below 10 degrees Celcius. It was also found to be lowest for inactive larvae, while it was higher for caterpillars with were moving or starved, higher still for those who were digesting, and highest for feeding larvae.

Digestion

After feeding, larvae may move to a new feeding site, but they often bask for about 5 hours. The increase in body temperature that results from basking increases digestion rate because it stimulates gut enzyme activity. G. groenlandica’s level of efficiency for the conversion of ingested food exceeds the mean value of the level in other Lepidopteran species.

Diapause

G. groenlandica experience a winter diapause period during which they form a hibernacula. In this state, they can withstand temperatures up to -70 degrees Celcius.

During the active season, larvae orient towards solar radiation and spin two-layer cocoons over a 24-hour period. When they finish, they tend to pupate with their head facing south, in a north-south orientation. In addition to dense pubescence, their cocoon helps to accumulate heat more effectively, accelerating pupal development. In this frozen state, they obtain energy from stored glycogen, but their metabolism becomes so low as to almost completely stop. This is due to the significant degradation of mitochondria, which may be restored in the spring after a period of only several hours.

Conservation

Warming Temperatures and Herbivory

When investigating Arctic moth caterpillars, it was found that larvae generally tended to have higher respiration rates and lower growth rates at warmer temperatures. They also tended to shift their diets to more nutrient-rich foods. Salix arctica and Dryas octopetala herbivory rates thus changed. Results such as this suggest host plant plasticity in G. groenlandica depending on their environment and suggest that increases in temperature due to global warming events, for instance, may have profound effects on the performance of cold-adapted herbivore invertebrates such as G. groenlandica, and herbivory rates of their food sources, suggesting that G. groenlandica may represent an indicator species for climate change.