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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.

1. Harmonia axyridis has invaded many regions of the world, with negative effects on local biodiversity, and thus it is of global concern for biological conservation. Recently it has invaded central Chile, one of the world's biodiversity hotspots, where the abundance and richness of ladybird species, particularly native species in agroecosystems, have declined following its arrival. 2. Harmonia axyridis is particularly abundant in spring in the valleys of central Chile, but there is a dramatic decline in its abundance during the hot summer months. 3. This study reports the occurrence of this invasive alien species in the summer at high altitudes (3578 m a.s.l.) in the Andes, which is the highest record worldwide. Individuals were observed on native cushion plants, in a unique environment rich in endemic species. Harmonia axyridis were active, reproducing and co-occurring with three other species of coccinellids. 4. The dispersal of H. axyridis and other coccinellids from the valleys to high altitudes could represent a mechanism to escape the adverse high temperatures during the summer, returning to the valleys in autumn. Our study highlights the need to study the impacts of invasive alien species across a range of habitats, including not only agricultural landscapes, but also extreme ecosystems.

Aim: Biological invasions are one of the major threats to biodiversity. Usually highly disturbed anthropogenic habitats favour invasion by alien species such as the coccinellid Harmonia axyridis. The spread and impact of this species has been documented in Europe and North America, but no information exists for South America. The aims of this study were to: (1) document the process of invasion of H. axyridis in Chile, (2) compare the abundance of H. axyridis in different habitats with varying degrees of disturbance and (3) assess change in the coccinellid assemblages in alfalfa fields over the 6 years following invasion. Location: Chile. Methods: The spread of H. axyridis was estimated using information from citizen scientists alongside records from the National Pest Surveillance System. The abundance of H. axyridis in different habitat types and of all coccinellids in alfalfa fields was assessed using yellow sticky traps. In alfalfa, the variations in species richness, Shannon and Simpson diversity and equitability indices through time were compared. Results: Harmonia axyridis has rapidly increased in distribution: there have been 1875 records along 2863 km up to 2015 following the first observation in 2008 from Central Chile. The records span from sea level to 3200 m a.s.l. in the Andes. It has spread at an average rate of 184.8 km per year, preferentially colonizing disturbed habitats, but also invading native habitats. In alfalfa, it is particularly abundant and has become the dominant species, with a concomitant decrease in species richness and diversity of co-occurring species. Main conclusion: Citizen science, alongside professional surveillance, has provided an effective method for studying invasion by H. axyridis, which is now well established and distributed across Chile. The rate of spread has been dramatic and the associated changes to the coccinellid community could disrupt the functioning, and ultimately resilience, of invaded ecosystems.