Recording fine‐scale movement of ground beetles by two methods: Potentials and methodological pitfalls

Movement trajectories are usually recorded as a sequence of discrete movement events described by two parameters: step length (distance) and turning angle (bearing). One of the most widespread methods to record the geocoordinates of each step is by a GPS device. Such devices have limited suitability for recording fine movements of species with low dispersal ability including flightless carabid beetles at small spatio‐temporal scales. As an alternative, the distance‐bearing approach can avoid the measurement error of GPS units since it uses directly measured distances and compass azimuths. As no quantification of measurement error between distance‐bearing and GPS approaches exists so far, we generated artificial fine‐scale trajectories and in addition radio‐tracked living carabids in a temperate forest and recorded each movement step by both methods. Trajectories obtained from distance‐bearing were compared to those obtained by a GPS device in terms of movement parameters. Consequently, both types of trajectories were segmented by state‐switching modeling into two distinct movement stages typical for carabids: random walk and directed movement. We found that the measurement error of GPS compared to distance‐bearing was 1.878 m (SEM = 0.181 m) for distances and 31.330° (SEM = 2.066°) for bearings. Moreover, these errors increased under dense forest canopy and rainy weather. Distance error did not change with increasing distance recorded by distance‐bearing but bearings were significantly more sensitive to error at short distances. State‐switching models showed only slight, not significant, differences in movement states between the two methods in favor of the random walk in the distance‐bearing approach. However, the shape of the GPS‐measured trajectories considerably differed from those recorded by distance‐bearing caused especially by bearing error at short distances. Our study showed that distance‐bearing could be more appropriate for recording movement steps not only of ground‐dwelling beetles but also other small animals at fine spatio‐temporal scales

Beetles on the move: Not‐just‐a‐technical review of beetles' radio‐tracking

Radio telemetry with very high-frequency transmitters is a powerful tool for studying the movement patterns of animals. Although this tracking technology is widely utilized for various vertebrates, its application is limited to only a fraction of large-bodied insect species. Among them, beetles are the most popular insect group used for radio-tracking due to their relatively large body size, solid exoskeleton, and to some extent the well-known ecological background of some species. Here, we review the available literature about radio telemetry applied to beetles, focusing on current methodological advantages and constraints to record their movement, as well as how this method can assist in understanding various ecological aspects of beetle life history. Regardless of the huge potential of radio-tracking, the number of tracked beetle species is still very low, covering so far only 13 species belonging to five families that were studied almost exclusively in the Western Palearctic region. Most studies were descriptive, measuring simple trajectory parameters and examining movement behavior as a single strategy that is not triggered by any particular internal or external cues. Ecological aspects have been accessed to a lesser extent, especially in relation to the effects of abiotic factors and habitat use. There are still conceptual knowledge gaps: promising statistical approaches for movement analyses can connect movement patterns with specific habitat utilization but they are not yet used by entomologists. Moreover, knowing the movement patterns of many individuals and species can assist us to understand the composition and dynamics at the community level

REPRODUCTIVE CHARACTERISTICS AND HABITAT SELECTION OF CARABUS ULRICHII (COLEOPTERA, CARABIDAE) IN WOODLAND HABITATS IN HUNGARY

The distribution, seasonality and reproductive characteristics of Carabus ulrichii (Coleoptera, Carabidae) were studied in woodland habitats in Hungary. We sampled a beech forest, an oak forest and the adjacent transition zone using pitfall traps, in the Pilis Biosphere Reserve in 2005 and 2006. Generalised linear models were used to explore the impacts of the habitat quality and seasonality on the distribution of this species. We found that the light intensity model explained best the species' activity density pattern, suggesting preference for open oak forest. We also found that the mandible wear was not a good estimator of age in C. ulrichii, but ovarial condition could be used to assess reproductive status. The seasonal activity and life history patterns were similar in the three different habitats for both sexes. Although differences in the total activity density of the species were found, there were no differences either in the seasonal activity patterns, or in the age-composition, or in the reproductive characteristics of C. ulrichii among the studied habitats. C. ulrichii beetles reproduced only once per season in the studied forested habitats

Effects of varying sampling effort on the observed diversity of carabid (Coleoptera: Carabidae) assemblages in the Danglobe Project, Denmark

Diversity relations among three stages of an urbanisation gradient were studied, using the Rényi scalable diversity index family and the Right Tail Sum (RTS) diversity. The rural areas were less diverse than either the urban or the suburban ones. The urban areas were more diverse considering the dominant species, while the suburban areas were more diverse considering the rare species. Next, we examined the impact of different sampling regimes on these diversity relations. A pulsating sampling method (sampling for 2 weeks every month) gave the same diversity ordering as continuous sampling. Further reduction in sampling period altered the diversity relations

No increase in fluctuating asymmetry in ground beetles (Carabidae) as urbanisation progresses

Environmental stress can lead to a reduction in developmental homeostasis, which could be reflected in increased variability of morphological traits. Fluctuating asymmetry (FA) is one possible manifestation of such a stress, and is often taken as a proxy for individual fitness. To test the usefulness of FA in morphological traits as an indicator of environmental quality, we studied the effect of urbanisation on FA in ground beetles (Carabidae) near a Danish city. First, we performed a critical examina- tion whether morphological character traits suggested in the literature displayed true fluctuating asymmetry in three common predatory ground beetles, Carabus nemoralis, Nebria brevicollis and Pterostichus melanarius. Eight metrical (length of the second and third antennal segments, elytral length, length of the first tarsus segment, length of the first and second tibiae, length of the proximal and distal spines on the first femurs) and one meristic (the number of spines on the second tibiae) traits were examined. Most of them showed FA but not consistently. Females generally displayed a higher level of FA than males. Finally, we examined the changes in the level of FA in bilateral morphological traits along an urbanisation gradient (forest - suburban forest - forest fragments in urban park) to test whether environmental stress created by urbanisation is reflected in FA. Ground beetles common along a Danish urbanisation gradient did not seem to indicate differences in habitat quality by their level of F