The Effect of Habitat on Insect Movements: Experimental Evidence from Wild-Caught Butterflies

Abstract

There is broad evidence that the main driver of the ongoing biodiversity crisis is land-use change, which reduces and fragments habitats. The consequence of habitat fragmentation on behavioural responses of fitness-related traits in insects have been so far understudied. In herbivorous insects, oviposition-related behaviours determine access to larval food, and the fate of the next generation. We present a pilot study to assess differences in behaviours related to movement and oviposition in Limenitis camilla butterflies from Wallonia (Belgium), one of the most fragmented regions in Europe. We first quantified variation in functional habitat connectivity across Wallonia and found that fragmented habitats had more abundant, but less evenly distributed host plants of L. camilla. Secondly, we quantified the behaviours of field-caught L. camilla females originating from habitats with contrasted landscape connectivity in an outdoor experimental setting. We found differences in behaviours related to flight investment: butterflies from fragmented woodlands spent more time in departing flight, which we associated with dispersal, than butterflies from homogenous woodlands. Although results from this study should be interpreted with caution given the limited sample size, they provide valuable insights for the advancement of behavioural research that aims to assess the effects of global changes on insects.

Keywords: Limenitis camilla; behavioural ecology; butterflies; habitat fragmentation; land-use changes; oviposition site selection.

Figure 1

Maps with 5 km hexagonal grid reporting observations of Limenitis camilla in Wallonia from 1979 to 2019: (A) the total number of observations; (B) the number of years with at least one observations and (C) the number of decades with at least one observation.

Figure 2

Steps followed to define the functional habitat for L. camilla and to choose the collection sites with stable and abundant L. camilla populations in Wallonia.

Figure 3

An outdoor flight setup consisting of four cross-shaped greenhouse aluminium tunnels covered with insect mesh, placed in “Bois de Lauzelle” forest, an experimental site belonging to UCLouvain, and an inset representing the study species Limenitis camilla. Photos: R. Voda.

Figure 4

Maps reporting: (A) the average functional habitat (FH) connectivity and (B) its coefficient of variation (right) for Wallonia. Transparent cells inside Wallonia do not contain FH. The red and light-blue small hexagons overlaid on the maps show homogenous (HW) and fragmented (FW) woodlands from where butterflies were collected.

Figure 5

Sampling areas: (A) Comine-Warneton cells (fragmented woodlands) and (B) Doische (homogeneous woodlands). The red cells with canvas pattern were 1 km cells chosen for collecting L. camilla and for quantifying host plant abundance. The background map reports in gray the extent of functional habitat.

Figure 6

Barplot showing the percentage of total trial time (for all 14 tested butterflies) spent in the different behavioural categories. Red bars indicate time spent in the target tunnel (TT), whereas blue bars indicate control tunnels (which can be any of the four tunnels named following their long-axis cardinal direction).

Figure 7

Variation in three main behavioural categories (resting, departing and navigation) for homogeneous (in green), and fragmented (in brown) woodlands, with model marginal means and 95% CIs. The 95% CIs have been calculated considering only model regression parameters (i.e., not considering the uncertainty in the model variance parameters).