Prey-predator interactions between two intraguild predators modulate their behavioral decisions

Influence of environmental factors on predation rate for Bactrocera dorsalis on a tropical island

In tropical environments, insect prey face high predation rates due to the diverse interspecific interactions driven by various environmental factors. However, a detailed understanding of how these factors interact to influence predation rate remains limited. This complexity increases with the presence of both native and nonnative predators, yet no comprehensive assessment has been conducted. In this study, we used the pupae of the widely distributed fruit fly Bactrocera dorsalis to examine how 8 tropical environmental factors affect its predation rate. Principal component analysis identified 3 principal components (PCs) that collectively explain 78.86% of the variance in the influence of these environmental factors: PC1 accounted for 49.62%, PC2 for 15.59%, and PC3 for 12.65%. PC1 was strongly influenced by patch density (loading: 0.87) and altitude (loading: -0.90), with communalities of 77.8% and 82.3%, respectively. PC2 was primarily driven by native predator diversity (loading: 0.90), with the highest communality (84.1%). PC3 was characterized by temperature (loading: 0.65) and humidity (loading: 0.70), with communalities of 81.2% and 81.8%, respectively. Although no individual PC had a significant effect on predation rate, the interaction between PC1 and PC2 was highly significant, indicating a strong combined effect. This interaction likely results from the way altitude and human disturbance contribute to habitat fragmentation, which in turn affects native predator diversity and alters the predation rate for B. dorsalis. These findings offer valuable insights into the interaction between B. dorsalis and its predators, as well as into the effectiveness of potential control strategies involving predators.

Activity pattern of Tityus serrulatus (Scorpiones: Buthidae) in an urban area in the state of São Paulo, Brazil

Tityus serrulatus Lutz & Mello (Scorpiones: Buthidae) is a scorpion endemic to Brazil adapted to synanthropic life, colonising and proliferating in the most populous urban areas in the country. Here, we evaluated its activity pattern in an urban cemetery in the municipality of Americana, state of São Paulo, Brazil. Additionally, we tested the effects of species reproduction and climatic seasons on the activity pattern. The Saudade Municipal Cemetery was sampled between 17:00 and 22:00 h during 455 nights from April 2006 to December 2013. The circular mean and the peak of activity were quantified for the total number of specimens, and for specimens with and without broods. Activity patterns were inferred using a rosette diagram. Circular analysis of variance was used to investigate if activity patterns changed across climatic seasons (wet and dry seasons). A total of 25,969 records (467 specimens with broods) were obtained in the field. The circular mean varied between 19:44 and 19:48 h, and the peak of activity occurred between 18:00 and 20:00 h for all groups. Peaks of activity differed from that recorded under laboratory conditions (between 21:00 and 23:00 h). Activity patterns did not differ for specimens with broods, suggesting that the reproductive condition does not alter the species activity pattern. The activity pattern differed between wet and dry seasons for all specimens and specimens without broods, but differences were small and probably biologically irrelevant, probably because the species tolerates a wide variation in abiotic conditions. Deepening the knowledge of the behaviour activity of T. serrulatus can have practical applications for health surveillance agencies, aiming to increase the effectiveness of scorpion control in urban areas.

Comparative analysis of mitochondrial genomes reveals family-specific architectures and molecular features in scorpions (Arthropoda: Arachnida: Scorpiones)

Scorpions are a group of arachnids with great evolutionary success that comprise more than 2,000 described species. Mitochondrial genomes have been little studied in this clade. We describe and compare different scorpion mitochondrial genomes and analyze their architecture and molecular characteristics. We assembled eight new scorpion mitochondrial genomes from transcriptomic datasets, annotated them, predicted the secondary structures of tRNAs, and compared the nucleotide composition, codon usage, and relative synonymous codon usage of 16 complete scorpion mitochondrial genomes. Lastly, we provided a phylogeny based on all mitochondrial protein coding genes. We characterized the mitogenomes in detail and reported particularities such as dissimilar synteny in the family Buthidae compared to other scorpions, unusual tRNA secondary structures, and unconventional start and stop codons in all scorpions. Our comparative analysis revealed that scorpion mitochondrial genomes exhibit different architectures and features depending on taxonomic identity. We highlight the parvorder Buthida, particularly the family Buthidae, as it invariably exhibited different mitogenome features such as synteny, codon usage, and AT-skew compared to the parvorder Iurida that included the rest of the scorpion families we analyzed in this study. Our results provide a better understanding of the evolution of mitogenome features and phylogenetic relationships in scorpions.