AKCE International Journal of Graphs and Combinatorics

Abstract Targeting the distribution of germ-cell markers is a widely used strategy for investigating germline development in animals. Among these markers, the vasa (vas) orthologues, which encode ATP-dependent RNA helicases, are highly conserved. Previous studies have examined asexual (parthenogenetic) and viviparous embryos of the pea aphid Acyrthosiphon pisum using a cross-reacting Vas antibody. This study utilized a specific antibody against Ap-Vas1, a Vas orthologue in the pea aphid, to gain new insights into germline development. The Ap-Vas1-specific antibody facilitates earlier detection of germ-plasm assembly at the oocyte posterior, challenging the previous assumption that germ-plasm assembly begins only at the onset of embryogenesis. Treatment of oocytes and early embryos with cytoskeleton inhibitors suggests that germ-plasm assembly primarily depends on actin, in contrast to the fly Drosophila melanogaster, where both actin and microtubules are essential. Since pea aphids lack an orthologue of osk, which encodes the protein Osk responsible for anchoring Vas to the germ plasm in Drosophila, this suggests that pea aphids employ distinct mechanisms for osk- and microtubule-independent formation of the germ plasm. Moreover, the clustering of germ cells into germarium-like structures in the extraembryonic region before entering the embryos suggests a gonad formation process different from that in Drosophila, where germ cells begin to cluster into germaria after settling within the embryonic gonads. Therefore, the analysis of the Ap-Vas1 distribution provides a deeper understanding of germline development in asexual pea aphids, uncovering novel aspects of parthenogenetic and viviparous reproduction in insects.

Abstract Puddling, a behavior in which butterflies and other insects aggregate on mineral-rich substrates such as mud, animal excrement, carrion, and even human perspiration, is a well-documented phenomenon in both temperate and tropical regions. This behavior is thought to compensate for the limited access to micronutrients in the adult diet that are important for fitness, primarily sodium and nitrogen, essential for nervous system function, growth, and reproductive processes. In this review, we consolidate existing knowledge on butterfly puddling and highlight key gaps in our understanding. The review is organized into 4 main themes: the benefits of puddling, social dynamics in puddling, sensory cues for site selection, and behavioral variation across species and regions. We explore how nutrient preferences are influenced by diet, environmental factors, and evolutionary history, with a particular focus on the role of sodium and nitrogen. We also discuss the potential reproductive benefits of puddling, including its impact on mating success and fecundity. In addition, we consider the sensory and social mechanisms butterflies use to locate suitable puddling sites. Lastly, we give a short overview on puddling in moths. This review identifies several areas for future research, particularly in understanding the adaptive significance of puddling across different taxa and environments.

Abstract Platygastrine wasps (Hymenoptera: Platygastridae) are parasitoids of gall midges (Diptera: Cecidomyiidae). They and their hosts are exceptionally abundant and speciose, with great relevance to agriculture and biodiversity research. Both groups are also “dark taxa,” whose species identification and ecological associations are obscured by a history of taxonomic confusion and neglect. Verified host records are few in number and limited in scope. In order to understand host specialization, more records are needed. However, rearing Cecidomyiidae is challenging, as many species require living host tissue to complete development. There is no universal rearing method for Cecidomyiidae and their parasitoids. The present work applies an exploratory approach to rearing gall midges, with the aim of obtaining accurate host associations and parasitoid identifications. We obtained 5 species of Platygastrinae from reared material, 3 of which are identified and diagnosed. Platygaster demades Walker (= Platygaster marchali Kieffer, syn. nov. = Platygaster ornata Kieffer, syn. nov.) is not host-specific, attacking Cecidomyiidae on Rosaceae worldwide, including Filipendula ulmaria. Synopeas gibberosum Buhl apparently specializes on Dasineura ulmaria (Bremi) on F. ulmaria. Synopeas rhanis (Walker) is known only from galls of D. urticae (Perris), but may attack other midge species on Urtica dioica. Amblyaspis sp. emerged from Hartigiola annulipes (Hartig) galls on Fagus sylvatica, and Synopeas sp. was associated with Mycodiplosis sp. on Rubus sp. Illustrations, DNA barcodes, and distributions are provided. We discuss challenges to understanding “double dark taxa” interactions, implications for biological control, and possible solutions for future research on these important but neglected systems.

Abstract Pseudacysta perseae (Heidemann 1908) (Hemiptera: Tingidae) is a foliar pest of avocados. The effects of 6 fluctuating temperature regimens, which averaged 15, 20, 25, 30, 32, and 35 °C over a 24-h period, on the developmental and reproductive biology of P. perseae were investigated. Selected temperature cycles are representative of avocado production regions in California (US). Fluctuating temperature regimens had significant effects on P. perseae development times, fecundity, fertility, longevity, and survivorship rates. One linear model (Ordinary Linear) and 7 nonlinear regression functions (Beta, Brière-2, Lactin-2, Lobry–Rosso–Flandrois, Performance-2, Ratkowsky, and Weibull) were utilized to investigate the correlation between fluctuating temperature profiles and P. perseae development times. The Beta and Weibull models failed to converge. Model parameters, Tmin, Topt, and Tmax, were estimated as 1.72 to 9.78 °C, 31.04 to 31.57 °C, and 34.05 to 39.38 °C, respectively. The thermal requirement for development, K, was estimated as 476.19 degree-days. At 32 °C, P. perseae females exhibited 4 egg-laying peaks around days 11, 35, 54, and 63 of life. A maximum daily average of eggs laid (i.e., fecundity) was 6.07 on day 35 and the average daily egg-laying rate was 3.08 eggs over a 69-day span. The maximum proportion of eggs that hatched (i.e., fertility) was 0.49 on day 31, and the average daily proportion of hatched eggs was 0.10. This study confirmed that P. perseae passes through 4 nymphal instars, not 5 as previously reported. In addition, sexual dimorphism with respect to the coloration of the fourth antennal segment is documented and is substantially darker in adult males.

Abstract Colored traps can attract or repel insect species, and effects vary among biological groups. Cerambycidae and Cetoniidae are diverse Coleoptera families of ecological and economic importance in forest and agroecosystems. Here, we assessed the effectiveness of different colors of aerial fruit-baited traps in capturing Cerambycidae and Cetoniidae beetles in the Amazon rainforest. We evaluated 4 trap colors: blue, yellow, red, and transparent (control). We sampled Cerambycidae and Cetoniidae beetles from February 2022 to January 2024 in 5 Amazon forests. We collected a total of 1588 individuals and 18 species of Cerambycidae, and 345 individuals and 11 species of Cetoniidae. Species richness and composition of Cerambycidae and Cetoniidae beetles did not differ across the different trap colors. Blue traps exhibited lower abundance of Cerambycidae than did other trap colors. Transparent traps captured more common species (Shannon diversity) than red traps. Moreover, transparent traps harbored more dominant species (Simpson diversity) of Cerambycidae compared to other trap colors. A combination of factors involving the insect with its innate or learned ability to perceive different colors and the characteristics of local vegetation can influence insect preference for certain colors. Our findings provide evidence of the high efficiency of transparent traps for sampling the diversity of Cerambycidae and Cetoniidae beetles in the Amazon rainforest.

Abstract Microplitis manilae (Ashmead) (Hymenoptera: Braconidae) is a solitary endoparasitic wasp of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), a significant agricultural pest. We compared the parasitism of M. manilae on the first-, second-, and third-instar larvae of S. frugiperda and found that M. manilae prefered the second instar. We investigated the effect of 5 temperatures (18, 22, 26, 30, and 34 °C) on the development period in the immature stage of M. manilae and found that moderately high temperatures shortened the development time. Considering the development period, cocooning rate, and emergence rate, 26 °C was the optimal temperature for the highest value of females’ fecundity. We also examined the development of the immature stage of M. manilae by dissecting parasitized hosts and cocoons in the laboratory. Our results revealed that the eggs matured within 2 d, and the larvae progressed through 3 instars, culminating in a total developmental period of about 9 d. The prepupal stage retained the larval form, and the pupa pigment gradually precipitated after molting. All stages were documented in detailed micrographs. Our study lays a robust foundation for further studies on the physiological interactions between M. manilae and S. frugiperda.

Abstract Silpha obscura Linnaeus, 1758 (Coleoptera: Silphidae) is an omnivorous beetle species known for damaging agricultural crops, making it an important target for pest control strategies. Despite its impact, no studies have yet examined the anatomical and histological structures of the male digestive and reproductive tracts of S. obscura. Therefore, this study aimed to describe these structures in detail, which could provide insights into potential control methods. Twenty individuals were collected and histologically processed, with observations made using light microscopy. The digestive tract of S. obscura comprises 3 parts: a short foregut, a relatively long and wide midgut characterized by folds and numerous crypts of the blind intestine, and a narrow and elongated hindgut, which expands into the rectum. Malpighian tubules attach at the beginning of the hindgut, which continues with the ileum, colon, and rectum and ends at the anus. The male reproductive tract includes a pair of testes, a pair of efferent ducts (vas efferentia), a pair of deferent ducts (vas deferentia), a pair of seminal vesicles, 2 pairs of accessory glands, and the ductus ejaculatorius, which extends into the ejaculatorius bulbus. The reproductive tract terminates with the aedeagus. The testes consist of 2 lobes, each containing numerous follicles where spermatogenesis and spermiogenesis occur. This study provides detailed insights into the anatomy and histology of the digestive and male reproductive tracts of Silpha obscura. These findings may lead to new strategies for controlling this agricultural pest. Understanding these structures is crucial for further research.

Abstract Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a global invasive pest attacking soft-skinned fruit. The specialist larval parasitoid wasp, Ganaspis brasiliensis (Ihering), was recently approved in Europe and the United States for classical biological control releases against D. suzukii. Rearing methods are essential for supporting innundative releases but current methods using fresh fruit are costly and susceptible to variation in host quality. To develop an artificial rearing system, we first compared the performance and development of D. suzukii and G. brasiliensis on fresh raspberries and blueberries and then on various artificial diet shapes and volumes. Drosophila suzukii had 1–2 days shorter development times in raspberry than blueberry, whereas Ganaspis adult development time was similar in both fruit and averaged 25 days. Parasitism rates by G. brasiliensis were significantly higher in blueberry than raspberry in both small and large resource patches. We found that D. suzukii preferred to lay eggs in full sphere diet shapes than in flat diet circles or semisphere diet, and in the first trial with wasps parasitism was only found on D. suzukii larvae in the full sphere shape of raspberry diet. Comparison of parasitism on full sphere raspberry and blueberry diets found higher parasitism in raspberry compared to blueberry diet. Our results indicate potential for further improvement of artificial rearing systems for G. brasiliensis to allow more cost-effective and reliable rearing for biological control programs.

Abstract Aggression is an essential component of survival and fitness, although the expression of aggression behaviors can also carry fitness costs. As a result, aggressive behaviors vary significantly across animals and are likely acted on by natural selection to produce this variation. Aggression, and associated traits like nestmate discrimination, both complex traits, have well studied genetic components, with links to genes involved in processes like neuronal function, metabolism, and hormone and cuticular hydrocarbon (CHC) production and reception. However, whether and how natural selection acts on these genes to produce variation across species is not fully understood. Using a comparative genomics approach, we analyzed natural selection in ants (Hymenoptera: Formicidae) with candidate genes previously linked to these traits. We find that aggression is associated with shifts in selection intensity, including positive selection on neurotransmitter receptors, and that ants with low levels of nestmate discrimination experience positive or relaxed selection on several CHC genes. Interestingly, we find that most candidate genes analyzed experience positive selection across ants, regardless of aggression level or discrimination ability. Our results shed new light on the means by which natural selection may act to produce variation in aggression across the ants.

Abstract The soybean tentiform leafminer, Macrosaccus morrisella (Fitch) (Lepidoptera: Gracillariidae), is a new potential pest of soybean; however, little is known about its biology. This study determined the number of instars, how to distinguish those instars, and how to differentiate the sexes of M. morrisella. Soybean plants oviposited on by M. morrisella in the laboratory were sampled daily to assess the development of the insects by measuring larval head capsule width, body length, and leaf area mined. Cages containing a subset of plants were then checked daily until the first emergence of adults. In addition, 20 pupae and resulting adults were sexed. The frequency distribution of head capsule widths of M. morrisella larvae showed 4 nonoverlapping peaks. However, examination of individuals comprising the third peak showed 2 distinct mouthpart morphologies, which were a sap-feeding 3rd instar and a tissue-feeding 4th instar with overlapping distributions of head capsule widths. Inspection of tentiform mines containing individual larvae revealed the presence of up to 4 shed head capsules, confirming the existence of 5 instars. Leaf area mined ranged from 0.28 to 498.45 mm2 per larva. Pupae of M. morrisella were sexually differentiated by observing the presence of the gonads through the cuticle in males and its absence in females, and this was confirmed by examination of the frenula of the resulting adults. This study fills an important gap in our understanding of M. morrisella biology, which is crucial for developing integrated management strategies for this potential pest of soybean in North America.

Abstract Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae) (tree-of-heaven) is an invasive tree species first introduced to the United States in 1784. With high rates of sexual reproduction, rapid growth, and prolific vegetative sprouting, A. altissima is an aggressive competitor that reduces native plant diversity and is difficult to manage beyond small-scale infestations. In the United States, the issues associated with Ailanthus management were compounded by the 2014 arrival of Lycorma delicatula (spotted lanternfly). Lycorma delicatula coevolved with A. altissima, its primary host, in eastern Asia. Suppression of A. altissima is recommended as an important strategy to slow the spread of L. delicatula. Due to the inadequacy of traditional control methods to manage A. altissima, biological controls are desired. Several potential biological control agents have been proposed for A. altissima. This review discusses current research on several promising candidates, specifically a native fungus, Verticillium nonalfalfae Inderb. et al. (Hypocreales: Plectosphaerellaceae); a trunk-boring beetle, Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae: Cryptorrhynchinae); and an eriophyid mite, Aculops ailanthi (Lin-Fuping, Jin-Changle & Kuang-Haiya) (Arachnida: Eriphyidae). A list of other possible biological control agents is also provided. We discuss unanswered questions for each species, the limits of biological controls in this system, and call for further research on integrated pest management practices for managing A. altissima.

Abstract Chrysomelinae species have a striking ecological specialization due to their trophic selection on plants usually belonging to the same botanical family. Calligrapha (Chevrolat) (Coleoptera, Chrysomelidae) is a diverse genus that comprises about 80 species distributed in most of the American continent. Cytogenetic studies of Calligrapha refer to 18 species with a modal diploid chromosome number 2n = 23 = 22 + XO (male) and a meioformula n = 11 + XO (male). A population of C. polyspila (Germar) from República Oriental del Uruguay shows 2n = 24 = 22 + Xyp (n = 12 = 11 + X/yp, male), which is coincident with the karyotype currently considered as the ancestral one. We performed for the first time a detailed karyotype analysis in specimens of C. polyspila from Argentinean natural populations. We described the male karyotype and analyzed the meiotic behavior and frequency and distribution of chiasmata. We also examined the chromatin organization and constitution by determining the amount, composition, and distribution of constitutive heterochromatin and the number and location of nucleolus organizer regions. The presence of a novel 2n in C. polyspila from República Argentina allows proposing different trends of karyotype differentiation that may have occurred in the Argentinean and Uruguayan allopatric populations. Our results provide more information on the karyology of Chrysomelinae and contribute to discussing the evolutionary significance of the different cytological features and the fixed chromosomal variants observed in these South American populations of C. polyspila.

Abstract The evolution of sociality in insects has been predicted to reduce effective population sizes, in turn leading to changes in genome architecture, including higher recombination rates, larger genomes, increased GC-biased gene conversion (gBGC), and greater intragenomic variation in GC content to maintain castes through differential methylation. As the number of sequenced insect genomes continues to grow, it remains an open question which, if any, of these genomic features are consistent across social insect genomes. A major challenge to determining such commonalities has been the lack of phylogenetically controlled analyses across independent origins of sociality. Of the 15 Hymenoptera species for which recombination rate was available, social species had higher rates of recombination. Next, we conducted a broader analysis of genome architecture by analyzing genome assemblies for 435 species of Hymenoptera and 8 species of Blattodea to test if GC content, genome size, distribution of CpG sites or codon bias repeatedly differed between social and nonsocial species. Overall, there was little support for predictable changes in genome architecture associated with sociality across Hymenoptera, after accounting for phylogenetic relationships. However, we found a significant negative relationship between sociality and GC content within the family Apidae and a significant negative relationship between sociality and genome size within the family Halictidae. In all, these results suggest that unique origins of social behavior may produce unique trends in genomic architecture. Our study highlights the need to examine genome architecture across independent origins of social behavior.

Abstract The main function of symbiotic actinobacterias in fungus-farming ants (Formicidae: Myrmicinae: Attini) is to protect the cultivated fungus against the pathogenic fungus Escovopsis spp. The microorganisms with the highest antimicrobial potential are actinobacterias, specifically Pseudonocardia and Streptomyces. These actinobacterias have demonstrated greater aggressiveness against the pathogen compared to other free-living actinobacterias, suggesting a selective process for strains with greater effectiveness in controlling the mycoparasite. Hypotheses explaining the coevolution between attinis and actinobacterias suggest that Pseudonocardia is a specialist symbiont that has coevolved with attinis, while Streptomyces is a mutualist recurrently adopted from the environment. In addition to actinobacterias, other microbial groups such as yeasts and bacteria with antimicrobial potential have been reported. The diversity of biomolecules synthesized by attini microsymbionts suggests that the microbiota of these insects could be an underexplored source of biotechnological resources with potential for combating agricultural and clinical diseases. This review addresses the antimicrobial potential of the microbiome associated with fungus-farming ants, and also analyzes aspects of coevolution, eco-physiological roles, and the diversity of microorganisms with antimicrobial potential.