Tunisian Journal of Plant Protection << TJPP >>

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Guest Editorial

Insect collections and their role in taxonomy revisions, phylogenetic evolution and conservation

Insects first colonized land over 400 million years ago and have thrived ever since. One key to their remarkable success is their evolutionary adaptability across almost all of Earth’s environments, excluding marine habitats. They represent approximately 80% of all animal species, with estimates suggesting there are anywhere from 10 million to 100 million insect species alive today. These species are classified in about 30 orders, distinguished by significant differences in body structure and metamorphosis process.

The most dominant insect orders include beetles (Coleoptera), bees, wasps, and related species (Hymenoptera), flies (Diptera), and butterflies and moths (Lepidoptera). These orders, collectively known as the "big four," exhibit complete metamorphosis, progressing from egg to larva, then pupa and, finally to adult form. In contrast, insects with incomplete metamorphosis, where nymphs resemble adult forms with minor differences, include the diverse true bugs (Hemiptera), as well as crickets, grasshoppers, locusts (Orthoptera), and dragonflies, and damselflies (Odonata), which are highly visible.

Insects play many roles serving, in the assessment of biodiversity health and ecosystem function. They provide baseline data for monitoring changes due to habitat loss, climate change, pollution, and invasive species, informing effective conservation strategies. The insects display an astonishing range of colors, patterns, and sizes, from minuscule micro-wasps to imposing giants. From a fundamental body plan featuring six legs, antennae, and a segmented exoskeleton, insects have diversified into crucial ecological roles as pollinators, predators, decomposers, parasites, pests, and disease vectors.

Significant advancements have been achieved in the revision of plant pathogenic viruses and their transmission by vectors. However, progress in taxonomic research has not matched that of virus vector research. Consequently, nearly two-thirds of the recognized vector species have necessitated one or more taxonomic revisions. Taxonomic revision is crucial for maintaining stability in nomenclature, despite the inconveniences it may cause. The majority of known vector species have already undergone one or more name changes, and further changes are inevitable due to ongoing taxonomic revisions and improved conceptual frameworks governing the classification of all taxa. Genetic studies using barcoding have significantly influenced the morphological classification of insects in several ways. Genetic barcoding utilizes a short sequence of mitochondrial DNA to quickly, and accurately identify species. This allows for reliable identification even when traditional morphological characteristics are insufficient or ambiguous. Barcoding studies often reveal cryptic species, which are morphologically similar but genetically distinct.

Insect collections are invaluable resources across various scientific fields including taxonomy, evolution, ecosystem studies, conservation efforts, and long-term research durability. They are fundamental to taxonomy, providing researchers with physical specimens for detailed species identification, description of new species, and understanding of their interactions. These collections serve, as crucial reference libraries, facilitating accurate species classification for biodiversity assessments and ecological research. Moreover, insect collections enable the tracing of evolutionary relationships over time. By comparing specimens from different periods and regions, researchers can analyze changes in morphology, behavior, and genetics, gaining insights into how insects have adapted to environmental shifts and evolved over millions of years. They play a critical role in conservation efforts by identifying threatened species, assessing population trends, and identifying biodiversity hotspots. They contribute to the development of conservation policies and, management plans aimed at preserving habitats and safeguarding species diversity. Additionally, these collections serve as repositories of genetic material, potentially supporting future restoration efforts. It also provides representative specimens of different species, facilitating precise identification through visual comparison of morphological characteristics. However, genetic studies complement this identification by comparing DNA sequences among individuals, particularly useful when morphological differences are subtle or when species are closely related phylogenetically. Collections often reveal new species or significant geographic variations within a single species and can confirm whether these differences permit a new taxonomic classification. For example, morphologically similar species in geographically distinct regions may be differentiated by genetic data, revealing underestimated diversity. Collections provide a basis for studying evolutionary relationships among insect genera. By combining morphological and genetic data, taxonomists can propose revisions that more accurately reflect species phylogeny. Genetic studies provide crucial information on the evolution of genetic characteristics and their transmission across generations, aiding in reconstructing phylogenetic trees and establishing robust taxonomic relationships. Morphologically similar groups of insects may be separated into multiple distinct species based on their genetic differences, leading to revisions in genera and higher classifications. Barcoding can also validate existing morphological classifications by confirming that observed morphological differences correspond to significant genetic differences. This reinforces confidence in the accuracy of classifications based on morphological features. Accurate taxonomy is essential for insect conservation, identifying threatened species, and developing appropriate preservation strategies.

In conclusion, insect collections and genetic studies are indispensable tools for revising the taxonomy and classification of insects. They not only help identify and describe new species but also enhance our understanding of their evolution and ensure their long-term conservation in an ever-changing world.

Prof. Sonia Bouhachem
Senior Researcher at INRAT
University of Carthage, Tunis
Tunisia