Explore the vast range of titles available.

The strong association between Varroa destructor, deformed wing virus (DWV), and high overwintering colony losses (OCL) of honey bees is well established. Three DWV master variants (DWV-A, -B, and -C) have been described, and their role in colony mortality remains an open question. Therefore, the aim of this study is to investigate the seasonal prevalence, viral load, and changing distribution of the three DWV master variants within honey bee colonies from England, Wales, and 32 states across the United States. Here, we report that in 2016, DWV-B was prevalent (100%, n = 249) and dominant (95%) in England and Wales, compared to the US. (56%, n = 217 and 23%, respectively), where DWV-A was prevalent (83%, n = 217) and dominant (63%). DWV-C was regularly detected in low viral loads (<1 × 107 genome equivalents per bee) and at lower prevalence (58% in England and Wales, n = 203, and 14% across the United States, n = 124) compared to DWV-A and -B. DWV-B prevalence and dominance in England and Wales coincided with low OCL (6%). Meanwhile, a 60% loss was reported by participating U.S. beekeepers. In the United States, DWV-A prevalence (89%, n = 18) and viral load were significantly (p = 0.002) higher (1 × 10 8–1 × 1011) in colonies that died when compared to the surviving colonies (49% (n = 27), 1 × 106–1 × 1010). DWV-B had low prevalence (56%, n = 18) in the colonies that died with viral loads of <1 × 1010. However, DWV-B was routinely detected in high viral loads (>1 × 1010) in surviving colonies from all sample locations, providing further supporting evidence of DWV-A exhibiting increased virulence over DWV-B at the colony level.

Winter sea-ice conditions are considered important for Antarctic krill Euphausia superba survival and recruitment, yet few broad-scale longitudinal studies have examined the underlying relationships between winter conditions and krill recruitment. We used data from a 4 yr winter study of krill con - dition (lipid content), diet (stable isotopes and fatty acids), and length distributions around the northern Antarctic Peninsula to examine relationships among environmental variables (annual sea-ice cover, water column chlorophyll a [chl a], and upper mixed-layer water temperature), the condition and diet of krill, and recruitment success the following year. Diet indicators (lipid content, δ15N, δ13C, and the fatty acid ratios 16:1n-7/18:4n-3 and 18:1n-9/18:1n-7) in postlarvae were consistent among years regardless of seaice cover, suggesting that post-larval krill do not rely on sea-ice resources for overwinter survival. Diet indicators in larvae were more variable and suggest that larvae may feed on sea-ice resources when they are available but can still persist in the water column when they are not. Principal component analysis between environmental variables and diet indicators showed that water-column chl a was the only variable that significantly affected diet, regardless of annual changes in sea-ice cover. Extensive winter ice in one year did not translate into successful recruitment the following year. Krill demonstrate a high degree of flexibility with respect to overwinter habitat and diet, and the degree to which sea ice is important during different times of year and at different life stages may be more complex than previously thought.

The fall armyworm (FAW) Spodoptera frugiperda is a long-distance migratory insect pest, and the invaded range of its recent expansion includes regions colder than the tropical and subtropical regions in East Asia. In order to understand the potential distribution of S. frugiperd in temperate and colder regions, we quantified the effects of temperature and exposure duration on the degree of indirect chilling injury caused to S. frugiperd under laboratory conditions. The adults were more tolerant to moderately low temperatures (3 to 15 °C) than the larvae and pupae. Survival decreased significantly when adult S. frugiperd were exposed to temperatures of 9 °C or lower. A time–temperature model suggested that indirect chilling injury began occurring at 15 °C. Survival was improved by short-term daily exposure to higher temperatures, indicating the existence of a repair mechanism for indirect chilling injury in S. frugiperd. The degree of repair depended on the temperature, but the relationship was not a simple direct proportion. These findings on indirect chilling injury and repair will improve the estimation of the potential distribution of S. frugiperd in temperate and colder regions.

In southern California, USA, annual reoccurrence of bluetongue infection in cattle (Bos taurus Linnaeus (Artiodactyla: Bovidae)) suggests that bluetongue virus (BTV) persists year-round but escapes detection during cooler months, reappearing when the weather gets warmer. The persistence of the virus in the adult biting midge vector, Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), has been suggested. However, it is unknown whether adult C. sonorensis are sufficiently active during the winter months to transmit BTV throughout this period. This study captured host-seeking C. sonorensis in the Chino dairy region of southern California throughout the BTV interseasonal period (winter through early spring) over 3 years to assess adult host-seeking activity and adult survival during this period. BTV prevalence in host-seeking midges was also determined. Host-seeking nulliparous and parous C. sonorensis were consistently captured throughout the winter months, which combined with wintertime adult midge survival of ≤27 d, suggests the BTV overwintering is likely due to ongoing low-level transmission to available cattle hosts. However, BTV was not detected in midges captured during January through April in this study, suggesting that BTV transmission during the winter months may be occurring at too low a level to detect even with the substantial trapping effort applied in this study.

Transgenerational signaling allows many organisms to anticipate seasonal variation. Diapause, a hormonally-programmed period of developmental arrest, is a widespread anticipatory seasonal response that is often mediated by transgenerational signaling. Despite the well-established adaptive significance of diapause, the molecular and physiological basis of transgenerational diapause signaling remains largely unresolved. Since lipid accumulation is a hallmark of diapause preparation, we hypothesized that increased lipid provisioning and accumulation mediate transgenerational diapause signaling. To test this hypothesis, we suppressed transcripts of two lipid metabolism genes using RNA-interference in the maternal generation of the vector mosquito, Aedes albopictus . We show that a reduction in maternal lipid storage droplet 2 ( lsd2) transcript abundance, but not diacyl-glycerol O-acyltransferase 1 ( dgat1 ) transcript abundance, reduces egg triglyceride levels. Suppression of lsd2 in adult females also leads to increased egg desiccation, inhibits the starvation tolerance of larvae, and decreases egg overwinter survival. However, knockdown of lsd2 does not affect diapause incidence, the timing of diapause termination, and post-diapause development. Together, our results indicate that transgenerational lipid provisioning affects diapause-associated overwintering fitness traits, but not the regulation of entry into diapause or termination of diapause.

Since the 1980s, the freshwater apple snails, Pomacea canaliculata , Pomacea maculata , and their hybrid, have been introduced into a wide range of freshwater ecosystems in tropical to temperate regions. Although P. canaliculata has become established in temperate East Asia, P. maculata and the hybrid are rarely found in this region. To evaluate the risk of P. maculata and the hybrid particularly as rice pests in temperate regions, we compared growth rate, winter survival rate, and feeding efficiency on rice seedlings of these snails with P. canaliculata . When P. maculata and P. canaliculata hatchlings were reared under laboratory or field conditions, the adult P. maculata had larger shells than adult P. canaliculata . Neither P. maculata nor F1 hybrids could survive winter in a simulated drained paddy field, and only a few individuals of P. maculata and F1 hybrids overwintered successfully in freshwater. Pomacea maculata juveniles fed on rice seedlings at the highest rate at temperatures above 27°C. These results suggest that P. maculata becomes a serious rice pest in temperate region as P. canaliculata once it is introduced from warmer regions under global warming. Further biological examination of P. maculata is needed to evaluate the risk of this snail in detail.

Bumblebee (Bombus spp.) queens overwintered in artificial settings tend to have low survival rates, raising concerns that diapause may be a particularly sensitive life cycle stage for this ecologically and economically valuable group of pollinators. However, it remains unclear whether lab-based estimates of diapause survival are comparable to survival rates of natural populations. In this study, we monitored the survival of Bombus impatiens queens overwintering in the field in Ipswich, MA, and conducted a meta-analysis of studies that estimate queen diapause survival in the lab to compare our field-based estimates of survival to those of lab-based studies. We found that queen B. impatiens had relatively high rates of overwintering survival after about six months (> 60%), especially when compared to estimates of six-month survival from lab studies (< 10%). We also observed a trend that broadly corroborates many lab studies of bumblebees, in that overwinter survival of queens was related to colony origin. In addition to providing the first estimate of diapause survival for bumblebee queens in nature, our study emphasizes the need to verify patterns observed in the lab to field-based studies.Implications for insect conservationAlthough protecting target species during sensitive life cycle stages is a fundamental goal of conservation ecology, it is first necessary to identify at what stages of the life cycle populations are most vulnerable. Our results suggest that, at least in some study systems, diapause survival of queen bumblebees in the field may be higher than suggested by lab studies.

For many species, behavioral modification is an effective strategy to mitigate negative effects of harsh and unpredictable environmental conditions. When behavioral modifications are not sufficient to mitigate extreme environmental conditions, intrinsic factors may be the primary determinant of survival. We investigated how movement behavior, and internal (i.e., nutrition and age) and external (i.e., food availability and snow depth) states affect survival over winter of a long‐lived and highly faithful species (mule deer; Odocoileus hemionus). We first tested whether animals changed their behavior during winter based on internal and external states; we subsequently investigated how behavior and state interacted to influence survival in the face of extraordinary winter conditions. Movement behavior changed minimally as a function of age and nutrition; yet, movement behavior affected survival—animals that exhibited more restricted movements were more likely to succumb to mortality overwinter than animals with less restricted movements. Additionally, nutrition and cumulative snow depth had a strong effect on survival: animals that were exposed to deep snow and began winter with low fat were much less likely to survive. Behavior was an effective tool in securing survival during mild or moderate winters, but nutrition ultimately underpinned survival during harsh winters.

Over the past two decades, there has been a marked increase in Uruguayan olive production. However, the humid climate of Uruguay creates favorable conditions for the development of olive anthracnose, characterized by fruit rots and blossom blight, which are frequent and destructive symptoms. Several species of Colletotrichum are responsible for the disease, with C. acutatum sensu stricto (s.s) being the most prevalent. This study aimed to analyze the survival of Colletotrichum in an olive orchard with a history of olive anthracnose. For two consecutive years, samples of fruits, leaves, and woody organs were collected monthly from aerial parts of the olive tree. Colletotrichum spp. structures were recorded in a climate chamber, and C. acutatum s.s. was quantified. The study demonstrated that Colletotrichum can survive in different organs of the olive tree, with mummified fruit being the primary survival site, followed by leaves and branches. Among the leaf and woody organs, yellow leaves, leaves from defoliated branches, terminal dry branches, and healthy new branches were identified as important survival sites. Mummified fruits were not always present on the tree throughout the year, and leaves and branches can serve as the primary source of initial inoculum for infections of flowers and fruits in their absence.

The blacklegged tick (Ixodes scapularis) spends up to 10 months in the soil between feeding as larvae and questing for hosts as nymphs the following year. We tracked the survival and energy use of 4320 engorged larvae evenly divided across 288 microcosms under field conditions from September to July on sites with high (>12 nymphs/150 m2) and low (<1.2 nymphs/150 m2) densities of naturally questing I. scapularis in New York State. Subsets of microcosms were destructively sampled periodically during this period to determine tick survivorship and physiological age. Across all sites tick mortality was low during the winter and increased in the spring and early summer, coincident with increasing energy use. Neither energy use nor mortality differed significantly between sites with high vs low natural tick density, but we did observe a significant positive relationship between soil organic matter content and the survival of I. scapularis during the spring. Our results suggest that the off-host mortality and energy use of I. scapularis nymphs is relatively low in the winter and increases significantly in the spring and early summer.