Abstract
Simple SummaryIn the following study, methods of geometric morphometrics were used to identify invasive forms of Harmonia axyridis. The study confirms the efficiency of geometric morphometrics as a tool for identifying minimal shape plasticity in wing shape and patterns of sexual shape dimorphism among invasive forms. Although more detailed studies are needed for further clarity, the study demonstrates that these methods can analyze phenotypic differences among the forms and reveal subtle phenotypic changes that explain genetic alterations within an invasive H. axyridis species.The Asian ladybird (Harmonia axyridis Pallas), native to Asia, is one of the 100 most invasive species in the world and has spread worldwide. This study aimed to characterize color forms of H. axyridis in Croatia and to analyze the variability of wing shape between populations and indicated forms. Geometric morphometric methods were used to analyze a total of 129 left and right wings in males and 126 left and right wings in females of H. axyridis collected from four different sites in Croatia. The results show a significant difference in wing shapes between the studied forms. Each form had its own specific morphotype that likely originated under the influence of genetic changes in the species. This study demonstrates that the use of geometric morphometric analysis is effective in studying the variability in H. axyridis populations. As this study is the first of its kind, for further clarity, it is necessary to conduct additional studies on a larger number of sites and an equal number of individuals of all forms.
Highlights
Among the world’s best-known biological control agents, approximately 90% of Ladybird beetles (Coleoptera, Coccinellidae) are predators
After calculating the canonical analysis of variance (CVA) to graphically discriminate between populations based on H. axyridis forms, we found that three populations had the conspicua form (Figure 5A) and four populations had spectabilis and succinea forms (Figure 5B,C), which were present in fewer individuals
Researchers have increasingly used the methods of geometric morphometrics to study multiple entomological phenomena and processes
Summary
Among the world’s best-known biological control agents, approximately 90% of Ladybird beetles (Coleoptera, Coccinellidae) are predators. H. axyridis is native to eastern and western Asia [4] and was intentionally introduced to North America and Europe in the 20th century as a classic and inundative biological control agent of aphids and scale insects [2,5]. Considered a top predator of hemipteran insects [2], H. axyridis is better known for its detrimental effects [9] by threatening native biodiversity through predation and competition with other aphid predators (e.g., coccinellids) and non-target species [3,10]. The species is an agricultural pest and an unpleasant urban pest, as it accumulates in houses or buildings in search of overwintering sites [13]. It emits an unpleasant odor by reflexively secreting blood that stains household textiles [14] and causes seasonal allergies (e.g., rhinitis, urticaria, asthma) in susceptible individuals [15,16]
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