Spatial heterogeneity in the abundance and fecundity of Arctic mosquitoes

Trapped between food, heat, and insects: Movement of moose (Alces alces) and exposure to flies in the boreal forest of Alaska

Moose (Alces alces) in the boreal forest habitats of Alaska are unlike other northern ungulates because they tolerate high densities of flies (Diptera) even though flies cause wounds and infections during the warm summer months. Moose move to find food and to find relief from overheating (hyperthermia) but do they avoid flies? We used GPS collars to measure the rate of movement (m⋅h-1) and the time spent (min⋅day-1) by enclosed moose in four habitats: wetlands, black spruce, early seral boreal forest, and late seral boreal forest. Fly traps were used in each habitat to quantify spatio-temporal abundance. Average daily air temperatures increased into July when peak biomass of forage for moose was greatest in early seral boreal forest habitats (424.46 vs. 25.15 kg⋅ha-1 on average in the other habitats). Average daily air temperatures were 1.7°C cooler in black spruce than other habitats, but fly abundance was greatest in black spruce (approximately 4-fold greater on average than the other habitats). Moose increased their movement rate with counts of biting flies (mosquitoes, black flies, horse and deer flies), but not non-biting flies (coprophagous flies). However, as air temperature increased (above 14.7°C) moose spent more time in fly-abundant black spruce, than early seral boreal forest, showing great tolerance for mosquitoes. Warm summer temperatures appear to cause moose to trade-off foraging in fly-sparse habitats for resting and dissipating heat in shady, wet habitats with abundant flies that adversely affect the fitness of moose.

Biting insects in a rapidly changing Arctic

Biting insects have a long-standing reputation for being an extreme presence in the Arctic, but it is unclear how they are responding to the rapid environmental changes currently taking place in the region. We review recent advances in our understanding of climate change responses by several key groups of biting insects, including mosquitoes, blackflies, and warble/botflies, and we highlight the significant knowledge gaps on this topic. We also discuss how changes in biting insect populations could impact humans and wildlife, including disease transmission and the disruption of culturally and economically important activities. Future work should integrate scientific with local and traditional ecological knowledge to better understand global change responses by biting insects in the Arctic and the associated consequences for the environmental security of Arctic communities.

Quantifying the nature and strength of intraspecific density dependence in Arctic mosquitoes

Processes that change with density are inherent in all populations, yet quantifying density dependence with empirical data remains a challenge. This is especially true for animals recruiting in patchy landscapes because heterogeneity in habitat quality in combination with habitat choice can obscure patterns expected from density dependence. Mosquitoes (Diptera: Culicidae) typically experience strong density dependence when larvae compete for food, however, effects vary across species and contexts. If populations experience intense intraspecific density-dependent mortality then overcompensation can occur, where the number of survivors declines at high densities producing complex endogenous dynamics. To seek generalizations about density dependence in a widespread species of Arctic mosquito, Aedes nigripes, we combined a laboratory experiment, field observations, and modeling approaches. We evaluated alternative formulations of discrete population models and compared best-performing models from our lab study to larval densities from ponds in western Greenland. Survivorship curves from the lab were the best fit by a Hassell model with compensating density dependence (equivalent to a Beverton-Holt model) where peak recruitment ranged from 8 to 80 mosquitoes per liter depending on resource supply. In contrast, our field data did not show a signal of strong density dependence, suggesting that other processes such as predation may lower realized densities in nature, and that expected patterns may be obscured because larval abundance covaries with resources (cryptic density dependence). Our study emphasizes the importance of covariation between the environment, habitat choice, and density dependence in understanding population dynamics across landscapes, and demonstrates the value of pairing lab and field studies.

Methoxyfenozide, a Molting Hormone Agonist, Affects Autogeny Capacity, Oviposition, Fecundity, and Fertility in Culex pipiens (Diptera: Culicidae)

The current study aimed to evaluate the effects of methoxyfenozide (RH-2485), an insect growth disrupter (IGD) belonging to molting hormone agonist class, against female adults of Culex pipiens L. under laboratory conditions. Lethal concentrations (LC50 = 24.54 µg/liter and LC90 = 70.79 µg/liter), previously determined against fourth instar larvae, were tested for adult female fertility, fecundity and oviposition after tarsal contact before mating and any bloodmeal. Methoxyfenozide was found to alter negatively their autogeny capacity and oviposition. A strong reduction of 56% and 72% (P < 0.001) in females' autogeny capacity was observed in both treated series, respectively. Alteration in oviposition were found to be higher with LC90 (OAI-LC90 = -0.62) than with the LC50 (OAI-LC50 = -0.42). Also fecundity and hatching rate (fertility) were significantly reduced in treated series as compared to controls. A significant reduction of 37.65 and 28.23% in fecundity and decrease of 56.85 and 71.87% in fertility were found, respectively in LC50 and LC90 treated series. Obtained data clearly demonstrated that methoxyfenozide have significant depressive effect on reproductive potential against medically important vector with minimizing ecotoxicological risks in mosquitoes management.

Arthropods and climate change - arctic challenges and opportunities

The harsh climate, limited human infrastructures, and basic autecological knowledge gaps represent substantial challenges for studying arthropods in the Arctic. At the same time, rapid climate change, low species diversity, and strong collaborative networks provide unique and underexploited Arctic opportunities for understanding species responses to environmental change and testing ecological theory. Here, I provide an overview of individual, population, and ecosystem level responses to climate change in Arctic arthropods. I focus on thermal performance, life history variation, population dynamics, community composition, diversity, and biotic interactions. The species-poor Arctic represents a unique opportunity for testing novel, automated arthropod monitoring methods. The Arctic can also potentially provide insights to further understand and mitigate the effects of climate change on arthropods worldwide.