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Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.

Opinion paper.

Harmonia axyridis (Pallas) has invaded most continents in the world, including South America. In Chile, it became invasive after 2010, turning into a dominant species in coccinellid guilds in alfalfa crops, where it coexists with the introduced species Hippodamia variegata (Goeze) and the native species Eriopis chilensis Hofmann, the populations of which declined after the invasion of H. axyridis. One of the echanisms attributed to the success of invasive species is the enemy release hypothesis (ERH), which predicts that natural enemies will have a lesser impact on the invasive species in the newly invaded areas than on resident species. Dinocampus coccinellae (Hymenoptera: Braconidae) is a cosmopolitan parasitoid of coccinellids, which vary in their suitability to parasitism according to species and location. The present study evaluated whether H. axyridis is a less suitable host than H. variegata and E. chilensis for D. coccinellae by assessing each step in the parasitism process, from oviposition to adult emergence in field and laboratory conditions. In the field, successful parasitism in H. axyridis (7%) was significantly lower than in H. variegata (33%) and E. chilensis (36%). H. axyridis was also the only species in which failed parasitoid larval development was greater than successful parasitism (adult emergence). In the laboratory, D. coccinellae never successfully oviposited in H. axyridis, while it did in the other two species. These results suggest that in Chile, H. axyridis is a less suitable host than the resident species for D. coccinellae. This mechanism, among others, may explain the dominance of this species in this early stage of invasion.

Global biodiversity monitoring is urgently needed across the world to assess the impacts of environmental change on biodiversity. One way to increase monitoring is through citizen science. ‘Citizen science’ is a term that we use in this chapter to describe the diverse approaches that involve people in monitoring in a voluntary capacity, thus including participatory monitoring in which people work collaboratively with scientists in developing monitoring. There is great unrealised potential for citizen science, especially in Asia and Africa. However, to fulfil this potential citizen science will need to meet local needs (for participants, communities and decision makers, including people's own use of the data and their motivations to participate) and support global needs for biodiversity monitoring (including the United Nations’ Sustainable Development Goals and the Aichi Biodiversity Targets). Activities should be feasible (for participants to provide scientifically rigorous data) and useful (for data users, from local to global scales). We use examples from across the world to demonstrate how monitoring can engage different types of participants, through different technologies, to record different variables according to different sampling approaches. Overall, these examples show how citizen science has the potential to provide a step change in our ability to monitor biodiversity—and hence respond to threats at all scales from local to global.

Identifying the main routes followed by an invasive species has significant management implications and may help to understand its colonization process. The obscure mealybug, Pseudococcus viburni (Signoret, 1875), is an important agricultural pest native to South America that infests fruit crops worldwide. The genetic diversity and structure of P. viburni samples collected around the globe was investigated here, and the most likely invasion routes were inferred using state-of-the-art population genetic methods. The results obtained include: (1) identification of low intrapopulation genetic diversity (mean number of alleles per locus below 4 and heterozygosity below 50%) and high genetic differentation among populations (average FST = 0.29); (2) strong evidence of an initial colonization from South America towards Europe and secondary introductions from Europe towards other continents, (3) evidence of population structure within Europe and, (4) support for 26 introductions from North America and Europe to South Africa. These results improve our understand- 28 ing of the worldwide distribution and invasion path-ways of P. viburni and suggest further exploring South America as the best source for potential biological control agents.