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).