Abstract:

Aims: The standardization of acquisition methods to collect insect specimens is a major component of insect diversity research. In light of the high species diversity, complex behavior, and wide distribution of insects, numerous active and passive acquisition methods have been developed to achieve different research goals. However, the use of active search acquisition methods is constrained by the presence of many interfering factors and poor reproducibility. Passive acquisition methods, such as flight interception trap (FIT), Malaise trap (MT) and pitfall trap (PT), have been widely adopted in different scenarios and have gradually become the most common methods for conducting insect diversity research due to their unique advantages. Despite their popularity, however, there is a lack of systematic research on the features and collecting effectiveness of these passive acquisition methods.
Methods: In this study, 13 sampling points in Shing Mun from Hong Kong, China were monitored in a one-month field survey (sampling frequency of about 2-3 days) using the three passive acquisition methods above (156 sets of equipment in total). These surveys were evaluated to determine each method's effectiveness for the beetle collection.
Results: A total of 6,380 beetle specimens of 197 species from 40 families were collected. The results of the study showed that: (1) There is a difference in the effectiveness of beetle collection by each acquisition method. Overall, FIT (36 families, 149 species) was more effective than MT (24 families, 79 species) and PT (17 families, 60 species). Ten families were collected by all the three methods. (2) The analysis of biodiversity indices and species-abundance distribution indicate the following: The richness index was the highest for FIT, followed by MT and PT. The dominance index was the highest for FIT, followed by PT and MT. The diversity index was the highest for MT, followed by FIT and PT. The evenness index was the highest for MT, followed by PT and FIT. The number of species with at least one individual collected by the three acquisition methods was very high. The species with more than one individual collected were widely distributed in time and space. There were fewer species from dominant families, though the total of individuals from these species accounted for a high proportion of all the collected beetles. (3) In terms of feeding habits, both FIT and PT enabled the collection of beetles from six dietary types. Among these, the algae-feeding family Ptiliidae was only collected by these two methods. (4) The plotted species accumulation curve demonstrated increased species discovery in a step-wise manner with gradually deceleration, which reflects the effectiveness of the three methods.
Conclusions: Each of the three acquisition methods have unique characteristics, but the comprehensive collection efficiency of FIT was markedly higher than MT and PT. Compared with PT, one of the most used acquisition methods, FIT and MT could enhance the coverage of species-richness, feeding habit, and body size of the beetles collected. This combination of collection methods would be conducive to better understand baseline beetle diversity and to conduct in-depth studies on the ecological functions and interactions of different groups. Furthermore, the beetles collected by each of the three methods were different to some extent, and thus a study's acquisition method should be selected according to the research goal and scientific problem to be addressed.

Key words: beetle, diversity, flight interception trap, Malaise trap, pitfall trap, Shing Mun