Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae) is the key natural enemy of Alternanthera philoxeroides (Mart.) Griseb, an invasive weed worldwide. To understand the morphology of A. hygrophila and further explore the specific host localization mechanism, scanning electron microscopy was used to observe and study the morphological characteristics of sensilla on the head appendages, tarsi, and external genital segments of A. hygrophila. Twelve types and forty-six subtypes of sensilla were observed. These contain various types of head appendices, including sensilla chaetica, sensilla trichodea, sensilla basiconca, sensilla coeloconica, sensilla styloconica, Böhm bristles, sensilla campaniform, sensilla terminal, sensilla dome, sensilla digit-like, sensilla aperture, and many subtypes. A new type of sensor was reported for the first time, which may be related to host plant recognition. This sensor was located on the distal segment of the maxillary palps of A. hygrophila and was named as sensilla petal-shaped based on its morphological characteristics. Sensilla chaetica, sensilla trichodea, and sensilla basiconca are also found on the tarsi and external genital segments. In addition, sensilla basiconica 4, sensilla coeloconica 1 and 2, sensilla styloconica 2, Böhm bristles 2, and sensilla campaniform 1 were only found in females. On the contrary, sensilla styloconica 3, sensilla coeloconica 3, and sensilla dome were only found in males. Numbers and sizes of the sensilla were also different between males and females. The potential functions related to structure were discussed in comparison with previous investigations on beetles and other monophagous insects. Our results provide a microscopic morphological basis for further research on the localization and recognition mechanism of A. hygrophila and its obligate host.

Alternanthera sessilis is considered the closest relative to the invasive weed Alternanthera philoxeroides in China, making it an important native species for studying the invasive mechanisms and adaptations of A. philoxeroides. Chloroplasts play a crucial role in a plant’s environmental adaptation, with their genomes being pivotal in the evolution and adaptation of both invasive and related species. However, the chloroplast genome of A. sessilis has remained unknown until now. In this study, we sequenced and assembled the complete chloroplast genome of A. sessilis using high-throughput sequencing. The A. sessilis chloroplast genome is 151,935 base pairs long, comprising two inverted repeat regions, a large single copy region, and a small single copy region. This chloroplast genome contains 128 genes, including 8 rRNA-coding genes, 37 tRNA-coding genes, 4 pseudogenes, and 83 protein-coding genes. When compared to the chloroplast genome of the invasive weed A. philoxeroides and other Amaranthaceae species, we observed significant variations in the ccsA, ycf1, and ycf2 regions in the A. sessilis chloroplast genome. Moreover, two genes, ccsA and accD, were found to be undergoing rapid evolution due to positive selection pressure. The phylogenetic trees were constructed for the Amaranthaceae family, estimating the time of independent species formation between A. philoxeroides and A. sessilis to be approximately 3.5186–8.8242 million years ago. These findings provide a foundation for understanding the population variation within invasive species among the Alternanthera genus.

The global invasion of the shrub L. camara poses a significant threat to ecosystems. Understanding the roles of human activity and climate in driving its spread is crucial for management. This study aimed to quantify its global invasion dynamics, identify key drivers, and predict future distribution shifts. We constructed a high-precision ensemble species distribution model by integrating historical global occurrence records, multi-source environmental variables (climate and human activity indices), and future climate scenarios (SSP1-2.6 and SSP5-8.5). The global invasion showed a clear four-stage acceleration pattern (1900–1960, 1961–1980, 1981–2000, and 2001–2025). Variable importance and response curve analysis revealed a two-phase “dispersal–colonization” mechanism: human activities (e.g., gross domestic product) acted as a “dispersal amplifier,” while a climatic factor (isothermality) served as a critical “colonization filter.” Under two future climate scenarios assuming unchanged human activity patterns, the potential suitable habitat of L. camara exhibits structural changes while maintaining stable total area. The highly suitable areas continue to shrink, with nearly half the area lost by the end of the century under the high-emission SSP5-8.5 pathway, while low-suitability zones expand significantly—yet the overall suitable habitat remains stable. Under SSP1-2.6, structural changes in suitable habitats occur more gradually. The study clarifies the distinct roles of human activity and climate in the invasion process, providing a scientific basis for differentiated global risk management strategies targeting dispersal pathways and colonization thresholds.