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1. Potential for urban warming to postpone overwintering dormancy of temperate mosquitoes

   https://doi.org/10.1016/j.jtherbio.2023.103594  

   Fyie, Lydia R; Tronetti, Hannah R; Gardiner, Mary M; Meuti, Megan E (July 2023, Journal of Thermal Biology)

   Cities are generally hotter than surrounding rural areas due to the Urban Heat Island (UHI) effect. These increases in temperature advance plant and animal phenology, development, and reproduction in the spring. However, research determining how increased temperatures affect the seasonal physiology of animals in the fall has been limited. The Northern house mosquito, Culex pipiens, is abundant in cities and transmits several pathogens including West Nile virus. Females of this species enter a state of developmental arrest, or reproductive diapause, in response to short days and low temperatures during autumn. Diapausing females halt reproduction and blood-feeding, and instead accumulate fat and seek sheltered overwintering sites. We found that exposure to increased temperatures in the lab that mimic the UHI effect induced ovarian development and blood-feeding, and that females exposed to these temperatures were as fecund as non-diapausing mosquitoes. We also found that females exposed to higher temperatures had lower survival rates in winter-like conditions, despite having accumulated equivalent lipid reserves relative to their diapausing congeners. These data suggest that urban warming may inhibit diapause initiation in the autumn, thereby extending the active biting season of temperate mosquitoes. 

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2. Light Pollution Disrupts Seasonal Differences in the Daily Activity and Metabolic Profiles of the Northern House Mosquito, Culex pipiens

   https://doi.org/10.3390/insects14010064  

   Wolkoff, Matthew; Fyie, Lydia; Meuti, Megan E. (January 2023, Insects)

   The Northern house mosquito transmits West Nile virus and survives the winter by entering a state of dormancy called diapause. Light pollution has been shown to interfere with diapause initiation in this mosquito. The effects of light pollution on daily activity rhythms and metabolic products have not been thoroughly investigated in diapausing and non-diapausing Northern house mosquitoes. We found that light pollution affected mosquito activity levels and several metabolic products differently depending on photoperiod, indicating that light pollution may disrupt nutrient accumulation and possibly interfere with diapause initiation in this species. 

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3. Phenotypic plasticity of male calls in two populations of the katydid Neoconocephalus triops (Insecta: Tettigoniidae)

   https://doi.org/10.3389/fevo.2023.1216463  

   Beckers, Oliver M.; Kijimoto, Teiya; Schul, Johannes (October 2023, Frontiers in Ecology and Evolution)

   David A. Gray (Ed.)

   The ability to respond to environmental changes plays a crucial role for coping with environmental stressors related to climate change. Substantial changes in environmental conditions can overcome developmental homeostasis, exposing cryptic genetic variation. The katydidNeoconocephalus triopsis a tropical species that extended its range to the more seasonal environment of North America where it has two reproductive generations per year. The harsher winter conditions required adults to diapause which resulted in substantially different mating calls of the diapausing winter animals compared to the non-overwintering summer animals in northern Florida. The summer call corresponds to that of tropical populations, whereas the winter call represents the alternative call phenotype. We quantified call plasticity in a tropical (Puerto Rico) and a temperate population ofN. triops(Florida) that differ in experiencing winter conditions in their geographic regions. We hypothesized that the plastic call traits, i.e., double-pulse rate and call structure, are regulated independently. Further, we hypothesized that phenotypic plasticity of double-pulse rate results in quantitative changes, whereas that of call structure in qualitative changes. We varied the photoperiod and duration of diapause during male juvenile and adult development during rearing and analyzed the double-pulse rate and call structure of the animals. Double-pulse rate changed in a quantitative fashion in both populations and significant changes appeared at different developmental points, i.e., the double-pulse rate slowed down during juvenile development in Florida, whereas during adult diapause in Puerto Rico. In the Florida population, both the number of males producing and the proportion of total call time covered by the alternative call structure (= continuous calls) increased with duration spent in diapause. In the Puerto Rico population, expression of the alternative call structure was extremely rare. Our results suggest that the expression of both pulse rate and call structure was quantitative and not categorical. Our systematic variation of environmental variables demonstrated a wide range of phenotypic variation that can be induced during development. Our study highlights the evolutionary potential of hidden genetic variation and phenotypic plasticity when confronted with rapidly changing environments and their potential role in providing variation necessary for communication systems to evolve. 

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4. Photoperiod during nest construction influences diapause status in the alfalfa leafcutting bee (Hymenoptera: Megachilidae)

   https://doi.org/10.1093/aesa/saaf029  

   Rinehart, Joshua D; Nash, Sarah E; Foster, Keegan J; Rinehart, Joseph P; Bowsher, Julia H (July 2025, Annals of the Entomological Society of America)

   Fraser, Ann (Ed.)

   Abstract Diapause initiation is determined by photoperiod and temperature in many insect species. In the solitary cavity-nesting bee Megachile rotundata (Fabricius) (Hymenoptera: Megachilidae), which undergoes facultative diapause as a prepupa, photoperiod is an important cue for diapause induction. However, it is unknown if the mother or offspring makes the decision to induce diapause or when this decision is made. Our goal was to answer these questions by manipulating photoperiod during different stages of development in M. rotundata. We subjected mothers to 3 different photoperiods as pupae and released them into the field to build nests and lay eggs when those same photoperiods occurred naturally. Offspring were collected and subjected to the same photoperiods as the mothers. We examined the effects of photoperiod on offspring diapause and the number of nests and brood cells created during each photoperiod. Our findings indicate that the photosensitive period occurs in the field, suggesting that the mother determines diapause during nest construction. We also found that reproductive output is the highest during the shortening photoperiods associated with midsummer. This study furthers our understanding of how diapause functions in Megachile rotundata and could be used to advance commercial management practices. 

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5. Diapause vs. reproductive programs: transcriptional phenotypes in a keystone copepod

   https://doi.org/10.1038/s42003-021-01946-0  

   Lenz, Petra H.; Roncalli, Vittoria; Cieslak, Matthew C.; Tarrant, Ann M.; Castelfranco, Ann M.; Hartline, Daniel K. (December 2021, Communications Biology)

   Abstract Many arthropods undergo a seasonal dormancy termed “diapause” to optimize timing of reproduction in highly seasonal environments. In the North Atlantic, the copepod Calanus finmarchicus completes one to three generations annually with some individuals maturing into adults, while others interrupt their development to enter diapause. It is unknown which, why and when individuals enter the diapause program. Transcriptomic data from copepods on known programs were analyzed using dimensionality reduction of gene expression and functional analyses to identify program-specific genes and biological processes. These analyses elucidated physiological differences and established protocols that distinguish between programs. Differences in gene expression were associated with maturation of individuals on the reproductive program, while those on the diapause program showed little change over time. Only two of six filters effectively separated copepods by developmental program. The first one included all genes annotated to RNA metabolism and this was confirmed using differential gene expression analysis. The second filter identified 54 differentially expressed genes that were consistently up-regulated in individuals on the diapause program in comparison with those on the reproductive program. Annotated to oogenesis, RNA metabolism and fatty acid biosynthesis, these genes are both indicators for diapause preparation and good candidates for functional studies. 

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