Butterflies
Surprisingly, urbanisation had no effect on the abundance, richness, or diversity of butterfly species on Lipsi Island (Figure 4). Habitat connectivity may be amplified due to the small spatial extent of the island, enabling butterflies to utilise both rural and urban habitats. The low building density and development of ecological corridors on Lipsi may also increase movement between urban and rural areas (Hennig and Ghazoul., 2011). Alternatively, the lack of response could be due to incomplete sampling of butterflies, with species accumulation curves indicating that 80-88% of potential butterfly species were captured. Limiting our sampling to two months in the summertime may also have reduced our scope to detect potential effects of urbanisation on butterfly abundance and diversity. It would be intriguing to monitor seasonal patterns of butterflies over the course of an entire year, but financial and logistical constraints meant we chose to conduct this study during peak butterfly activity in May and June 2021. Whilst this likely means we did not characterise the entire communities that can be found throughout the year, it gave us an indication of their abundance, diversity, and community composition in the peak season.
Nonetheless, there was a significant change in butterfly community composition between urban and rural habitats (Figure 7A), as found in several other locations (Numa et al., 2016, Stefanescu et al., 2004, Tzortzakaki et al., 2019). For example, Freyer’s grayling (H. fatua ) was the dominant butterfly in rural areas but was comparatively rare in urban settings (Figure 2A-B), reflecting its preference for meadows and thus a lack of suitable habitat in urban areas (Grill and Cleary, 2003). In contrast, the scarce swallowtail (I. podalirius ) was mainly found in urban environments (Figure 2A-B), reflecting its tendency to feed exclusively on rose plants, which are more likely to be found in urban gardens (Stefanescu et al., 2006). Butterfly species respond differently to the environmental constraints encountered along an urbanisation gradient due to variation in tolerance levels associated with life history and distribution (Pignataro et al., 2020). For example, a study in Patras city, Greece, showed that specialist butterfly species with specific feeding requirements were often absent from urban environments, whereas generalists exhibited a greater abundance in urban areas (Tzortzakaki et al. 2019). Habitat fragmentation and reduced connectivity due to urbanisation may lead to a decline in specialist species within these areas (Kuussaari et al., 2021; Brückmann et al., 2010), however, the geranium bronze (C. marshalli ) and mallow skipper (C. alceae ) were more abundant in urban areas on Lipsi, despite being specialists. Geranium bronze is highly associated with cultivated geranium plants (Pelargonium ) found in gardens and parks, whilst the mallow skipper caterpillar feeds on mallow plants (Malvaceae) which are weeds found in urban waste ground, roadsides, and gardens (Tzortzakaki et al., 2019). Therefore, the presence of cultivated plants within urban locations could mitigate the loss of natural vegetation and support certain specialist species (Chong et al., 2014), whilst generalist or opportunistic butterflies may be able to exploit the resources found in both urban and rural locations (Pignataro et al., 2020).