Integrating GWAS and Transcriptomics to Identify the Molecular Underpinnings of Thermal Stress Responses in \u3cem\u3eDrosophila melanogaster\u3c/em\u3e

Thermal tolerance of an organism depends on both the ability to dynamically adjust to a thermal stress and preparatory developmental processes that enhance thermal resistance. However, the extent to which standing genetic variation in thermal tolerance alleles influence dynamic stress responses vs. preparatory processes is unknown. Here, using the model species Drosophila melanogaster, we used a combination of Genome Wide Association mapping (GWAS) and transcriptomic profiling to characterize whether genes associated with thermal tolerance are primarily involved in dynamic stress responses or preparatory processes that influence physiological condition at the time of thermal stress. To test our hypotheses, we measured the critical thermal minimum (CTmin) and critical thermal maximum (CTmax) of 100 lines of the Drosophila Genetic Reference Panel (DGRP) and used GWAS to identify loci that explain variation in thermal limits. We observed greater variation in lower thermal limits, with CTmin ranging from 1.81 to 8.60°C, while CTmax ranged from 38.74 to 40.64°C. We identified 151 and 99 distinct genes associated with CTmin and CTmax, respectively, and there was strong support that these genes are involved in both dynamic responses to thermal stress and preparatory processes that increase thermal resistance. Many of the genes identified by GWAS were involved in the direct transcriptional response to thermal stress (72/151 for cold; 59/99 for heat), and overall GWAS candidates were more likely to be differentially expressed than other genes. Further, several GWAS candidates were regulatory genes that may participate in the regulation of stress responses, and gene ontologies related to development and morphogenesis were enriched, suggesting many of these genes influence thermal tolerance through effects on development and physiological status. Overall, our results suggest that thermal tolerance alleles can influence both dynamic plastic responses to thermal stress and preparatory processes that improve thermal resistance. These results also have utility for directly comparing GWAS and transcriptomic approaches for identifying candidate genes associated with thermal tolerance

A key and checklist to the Neotropical forensically important "Little House Flies" (Diptera: Fanniidae)

ABSTRACT Fanniidae (Insecta: Diptera) is a relatively small family (ca. 350 spp.) with five genera, of which Fannia Robineau-Desvoidy, 1830 and Euryomma Stein, 1899 have Neotropical distributions. Some of these species are almost always found in forensic studies. Forensically relevant species have been neglected, despite recent forensic studies that suggest their importance for estimating post-mortem interval (PMI). Thus, current and updated keys to identify adults or larvae on carcasses are unavailable for the most important species. While immature stages are important in estimating PMI, evidence suggests that adults (Fanniidae as well as other families) may also be useful for this purpose. Here we provide a key to males of the species of Fanniidae (found on corpses and other decomposing organic matter) with a checklist of species that have been used in forensics in the Neotropical region. The key comprises all 38 species of Fannia and Euryomma that have already been successfully used in forensics, and species that are potentially useful for estimating PMI. These records were found after reviews of the literature and data from entomological collections. Photographs and illustrations of the main characters in the key are provided

Transcriptional Regulation of Reproductive Diapause in the Convergent Lady Beetle, <i>Hippodamia convergens</i>

Diapause is an alternate development program that synchronizes an insect’s life cycle with seasonally abundant resources and ensures survival in unfavorable conditions. The physiological basis of diapause has been well characterized, but the molecular mechanisms regulating it are still being elucidated. Here, we present a de novo transcriptome and quantify transcript expression during diapause in the convergent lady beetle Hippodamia convergens. H. convergens is used as an augmentative biocontrol agent, and adult females undergo reproductive diapause that is regulated by photoperiod. We sampled females at three stages (early, mid, and late diapause) and compared transcript expression to non-diapausing individuals. Based on principle component analysis, the transcriptomes of diapausing beetles were distinct from non-diapausing beetles, and the three diapausing points tended to cluster together. However, there were still classes of transcripts that differed in expression across distinct phases of diapause. In general, transcripts involved in muscle function and flight were upregulated during diapause, likely to support dispersal flights that occur during diapause, while transcripts involved in ovarian development were downregulated. This information could be used to improve biological control by manipulating diapause. Additionally, our data contribute to a growing understanding of the genetic regulation of diapause across diverse insects

A key and checklist to the Neotropical forensically important "Little House Flies" (Diptera: Fanniidae)

ABSTRACT Fanniidae (Insecta: Diptera) is a relatively small family (ca. 350 spp.) with five genera, of which Fannia Robineau-Desvoidy, 1830 and Euryomma Stein, 1899 have Neotropical distributions. Some of these species are almost always found in forensic studies. Forensically relevant species have been neglected, despite recent forensic studies that suggest their importance for estimating post-mortem interval (PMI). Thus, current and updated keys to identify adults or larvae on carcasses are unavailable for the most important species. While immature stages are important in estimating PMI, evidence suggests that adults (Fanniidae as well as other families) may also be useful for this purpose. Here we provide a key to males of the species of Fanniidae (found on corpses and other decomposing organic matter) with a checklist of species that have been used in forensics in the Neotropical region. The key comprises all 38 species of Fannia and Euryomma that have already been successfully used in forensics, and species that are potentially useful for estimating PMI. These records were found after reviews of the literature and data from entomological collections. Photographs and illustrations of the main characters in the key are provided

Simulated winter warming negatively impacts survival of Antarctica's only endemic insect

1. Antarctic winters are challenging for terrestrial invertebrates, and species that live there have specialised adaptations to conserve energy and protect against cold injury in the winter. However, rapidly occurring climate change in these regions will increase the unpredictability of winter conditions, and there is currently a dearth of knowledge on how the highly adapted invertebrates of Antarctica will respond to changes in winter temperatures. 2. We evaluated the response of larvae of the Antarctic midge, Belgica antarctica, to simulated winters at three ecologically relevant mean temperature scenarios: warm (−1°C), normal (−3°C) and cold (−5°C). Within each scenario, larvae were placed into three distinct habitat types in which they are commonly observed (decaying organic matter, living moss, and Prasiola crispa algae). Following the simulated overwintering period, a range of physiological outcomes were measured, namely survival, locomotor activity, tissue damage, energy store levels and molecular stress responses. 3. Survival, energy stores and locomotor activity were significantly lower following the Warm overwintering environment than at lower temperatures, but tissue damage and heat shock protein expression (a proxy for protein damage) did not significantly differ between the three temperatures. Survival was also significantly lower in larvae overwintered in Prasiola crispa algae, although the underlying mechanism is unclear. Heat shock proteins were expressed least in larvae overwintering in living moss, suggesting it is less stressful to overwinter in this substrate, perhaps due to a more defined structure affording less direct contact with ice. 4. Our results demonstrate that a realistic 2°C increase in winter microhabitat temperature reduces survival and causes energy deficits that have implications for subsequent development and reproduction. While our Warm winter scenario was close to the range of observed overwintering temperatures for this species, warmer winters are expected to become more common in response to climate change. Conversely, if climate change reduces the length of winter, some of the negative consequences of winter warming may be attenuated, so it will be important to consider this factor in future studies. Nonetheless, our results indicate that winter warming could negatively impact cold-adapted insects such as the Antarctic midge