Vegetation
The lack of significant differences in the abundance, richness, and
diversity of plants between urban and rural sites (Figure 4d-f) could be
due to the limited spatial extent of habitat patches and the prevalence
of native, unmanaged vegetation within urban green spaces on Lipsi.
Whilst rural areas had significantly more shrubs and less bare ground
than urban sites, there was no difference in the cover of trees, which
are scarce on Lipsi, negating the possibility for greater tree cover to
promote butterfly species richness (Kurylo et al. 2020). The lack of a
marked difference in vegetation structure between urban and rural areas
could thus be a key factor in explaining the similarity in butterfly
abundance and diversity across habitats. A prevalence of non-native
plant species in urban areas may prevent larval development of
butterflies (Dylewski et al., 2019), but exotic species were only
present at three urban sites and in low abundance, limiting their
potentially negative effects on butterflies. Furthermore, butterfly
abundance responds negatively to non-native plants in late spring and
positively by mid-summer (Kurylo et al., 2020), highlighting the
importance of greater temporal resolution of sampling to characterise
vegetation effects on butterflies.
Urbanisation altered vegetation community composition (Figure 5c), with
cultivated barley (Hordeum vulgare ), castor bean (Ricinus
communis ), and scutch grass (Cynodon dactylon ) prevalent in
urban environments, while natural Mastic shrubs (Pistacia
lentiscus ), wild oats (Avena barbata ), and desert saltgrass
(Distichlis spicata ) dominated in rural environments. This may
have contributed to the observed differences in butterfly community
composition, with cultivated patches hosting different butterfly
assemblages than natural forests and scrub (Chong et al., 2014). Thus,
whilst we did not detect any effect of urbanisation on the abundance or
diversity of the vegetation and butterfly assemblages, the observed
changes in taxonomic identity could have major implications for
ecosystem functioning, which should be quantified in future studies.