Increased Suitability of Poleward Climate for a Tropical Butterfly (Euripus nyctelius) (Lepidoptera: Nymphalidae) Accompanies its Successful Range Expansion

Ecological forecasts of insect range dynamics: a broad range of taxa includes winners and losers under future climate

Species distribution models are the primary tools to project future species' distributions, but this complex task is influenced by data limitations and evolving best practices. The majority of the 53 studies we examined utilized correlative models and did not follow current best practices for validating retrospective or future environmental data layers. Despite this, a summary of results is largely unsurprising: shifts toward cooler regions, but otherwise mixed dynamics emphasizing winners and losers. Harmful insects were more likely to show positive outcomes compared with beneficial species. Our restricted ability to consider mechanisms complicates interpretation of any single study. To improve this area of modeling, more classic field and lab studies to uncover basic ecology and physiology are crucial.

The Chromosome-Level Genome of Hestina assimilis (Lepidoptera: Nymphalidae) Reveals the Evolution of Saprophagy-Related Genes in Brush-Footed Butterflies

Most butterflies feed on nectar, while some saprophagous butterflies forage on various non-nectar foods. To date, little is known about the genomic and molecular shifts associated with the evolution of the saprophagous feeding strategy. Here, we assembled the high-quality chromosome-level genome of Hestina assimilis to explore its saprophagous molecular and genetic mechanisms. This chromosome-level genome of H. assimilis is 412.82 Mb, with a scaffold N50 of 15.70 Mb. In total, 98.11% of contigs were anchored to 30 chromosomes. Compared with H. assimilis and other Nymphalidae butterflies, the genes of metabolism and detoxification experienced expansions. We annotated 80 cytochrome P450 (CYP) genes in the H. assimilis genome, among which genes belonging to the CYP4 subfamily were significantly expanded (p < 0.01). These P450 genes were unevenly distributed and mainly concentrated on chromosomes 6-9. We identified 33 olfactory receptor (OR), 20 odorant-binding protein (OBP), and six gustatory receptor (GR) genes in the H. assimilis genome, which were fewer than in the nectarivorous Danaus plexippus. A decreased number of OBP, OR, and GR genes implied that H. assimilis should resort less to olfaction and gustation than their nectarivorous counterparts, which need highly specialized olfactory and gustatory functions. Moreover, we found one site under positive selection occurred in residue 996 (phenylalanine) of GR genes exclusive to H. assimilis, which is conservative in most lineages. Our study provides support for the adaptive evolution of feeding habits in butterflies.

Ingestional Toxicity of Radiation-Dependent Metabolites of the Host Plant for the Pale Grass Blue Butterfly: A Mechanism of Field Effects of Radioactive Pollution in Fukushima

Biological effects of the Fukushima nuclear accident have been reported in various organisms, including the pale grass blue butterfly Zizeeria maha and its host plant Oxalis corniculata. This plant upregulates various secondary metabolites in response to low-dose radiation exposure, which may contribute to the high mortality and abnormality rates of the butterfly in Fukushima. However, this field effect hypothesis has not been experimentally tested. Here, using an artificial diet for larvae, we examined the ingestional toxicity of three radiation-dependent plant metabolites annotated in a previous metabolomic study: lauric acid (a saturated fatty acid), alfuzosin (an adrenergic receptor antagonist), and ikarugamycin (an antibiotic likely from endophytic bacteria). Ingestion of lauric acid or alfuzosin caused a significant decrease in the pupation, eclosion (survival), and normality rates, indicating toxicity of these compounds. Lauric acid made the egg-larval days significantly longer, indicating larval growth retardation. In contrast, ikarugamycin caused a significant increase in the pupation and eclosion rates, probably due to the protection of the diet from fungi and bacteria. These results suggest that at least some of the radiation-dependent plant metabolites, such as lauric acid, contribute to the deleterious effects of radioactive pollution on the butterfly in Fukushima, providing experimental evidence for the field effect hypothesis.

Taxonomy and ecology of genus Psyra Walker, 1860 (Lepidoptera: Geometridae: Ennominae) from Indian Himalaya

The Psyra Walker, 1860, is a typical Sino-Himalayan genus of the subfamily Ennominae, currently known by 18 species/4 subspecies globally and 9 species from India. This study aims to revise the taxonomy and ecology of Indian Psyra by providing a morphology-based diagnostic key, highlighting their altitudinal, habitat and seasonal preferences, and modelling their distribution based on current and future climatic scenarios. Here, we describe a new species, P. variabilis sp. nov. and document 4 species and 1 subspecies as new to India, viz. P. gracilis, P. szetschwana, P. dsagara, P. falcipennis and P. debilis debilis, thus updating the global species count to 19 with 14 species/1 subspecies from India. We also submitted partial mitochondrial COI sequences of P. crypta, P. similaria, P. spurcataria and P. gracilis as novel to the global genetic database and calculated the overall genetic divergence was 5.17% within the genus, suggesting strong monophyly. Being a typical montane genus, most of the species of Psyra were active within 2000-2280 m altitude, 10.55-15.7°C annual mean temperature, 1200-2300 mm annual precipitation and 168-179 NDVI. Psyra species were predominant in wet temperate, mixed coniferous and moist temperate deciduous forests, their abundance and richness being at peak during post-monsoon months of October-November. The major bioclimatic variables influencing the overall distribution of the genus were mean temperature of warmest quarter, temperature seasonality and precipitation of coldest/driest quarter. While two of the modelled species were predicted to lose area occupancy under future climatic scenarios, the narrow-specialist, Trans-Himalayan species P. debilis debilis was projected to gain up to 75% additional area in the years 2041-60. The results of this study will be helpful to identify sites with maximum area loss projection in ecologically fragile Indian Himalaya and initiating conservation management for such climatically vulnerable insect species groups.

Phenology dictates the impact of climate change on geographic distributions of six co-occurring North American grasshoppers

Throughout the last century, climate change has altered the geographic distributions of many species. Insects, in particular, vary in their ability to track changing climates, and it is likely that phenology is an important determinant of how well insects can either expand or shift their geographic distributions in response to climate change. Grasshoppers are an ideal group to test the hypothesis that phenology correlates with range expansion, given that co-occurring confamilial, and even congeneric, species can differ in phenology. Here, I tested the hypothesis that early- and late-season species should possess different range expansion potentials, as estimated by habitat suitability from ecological niche models. I used nine different modeling techniques to estimate habitat suitability of six grasshopper species of varying phenology under two climate scenarios for the year 2050. My results suggest that, of the six species examined here, early-season species were more sensitive to climate change than late-season species. The three early-season species examined here might shift northward during the spring, while the modeled geographic distributions of the three late-season species were generally constant under climate change, likely because they were pre-adapted to hot and dry conditions. Phenology might therefore be a good predictor of how insect distributions might change in the future, but this hypothesis remains to be tested at a broader scale.

Expanding insect pollinators in the Anthropocene

Global changes are severely affecting pollinator insect communities worldwide, resulting in repeated patterns of species extirpations and extinctions. Whilst negative population trends within this functional group have understandably received much attention in recent decades, another facet of global changes has been overshadowed: species undergoing expansion. Here, we review the factors and traits that have allowed a fraction of the pollinating entomofauna to take advantage of global environmental change. Sufficient mobility, high resistance to acute heat stress, and inherent adaptation to warmer climates appear to be key traits that allow pollinators to persist and even expand in the face of climate change. An overall flexibility in dietary and nesting requirements is common in expanding species, although niche specialization can also drive expansion under specific contexts. The numerous consequences of wild and domesticated pollinator expansions, including competition for resources, pathogen spread, and hybridization with native wildlife, are also discussed. Overall, we show that the traits and factors involved in the success stories of expanding pollinators are mostly species specific and context dependent, rendering generalizations of 'winning traits' complicated. This work illustrates the increasing need to consider expansion and its numerous consequences as significant facets of global changes and encourages efforts to monitor the impacts of expanding insect pollinators, particularly exotic species, on natural ecosystems.