2.1 Study area and landscape characterization
The study was conducted on 11 islands of the Maldivian archipelago (a
number of islands comparable to those investigated by Steibl, Franke &
Laforsch, 2021), located in two adjacent atolls, namely the southern
part of Faafu and the northern part of Dhaalu atolls, about 150 km from
the capital Male (Fig. 1). The temperature in these islands is
homogeneous throughout the year, with almost no seasonal variation and a
mean of 28°C (Bailey, Khalil, & Chatikavanij, 2015). The natural
vegetation is characterized by dense, unfragmented coastal forests,
where association of Scaevola taccada, Pemphis acidula, andPandanus spp. are typically found together with coconut palm
coastal plantations. Differently, the inner land of inhabited islands is
characterized by scattered coconut palms along with large trees such asFicus benghalensis , Artocarpus altilis, and several
cultivated fruit or ornamental species. Exotic plant species compose
almost 60% of the vegetation of the islands (Sujanapal & Sankaran,
2016). The investigated islands were selected in order to cover a
gradient of land-use intensification related to anthropic activities,
intended as the proportion of buildings, such as houses or
infrastructures devoted to human activities. The distances among
adjacent islands range between 1110 m (between islands 8 and 9, Fig 1 )
and 12000 m (between islands 6 and 10, Fig 1). They also differ in terms
of inhabitants (0-1600 people ca, Maldives population & housing census,
2014) that leads to a gradient of land-use and habitat fragmentation
across islands (Supporting Information, Fig S1). Fragmentation was
estimated through the edge density index (i.e. , green patches
edge length divided by total area), specifically calculated for the
inland green patches (i.e. , gardens, parks and semi-natural green
covered patches excluding the usually continuous coastal forest). To
estimate edge density, index polygons enclosing the inland green patches
have been manually drawn for each island using QGIS 3.16 and Bing Aerial
base map updated to 2019. The edge density of inland green patches was
calculated through the LecoS QGIS plugin (Jung, 2013). In the five
biggest islands (i.e. , those with a major axis greater than 500
m) two sampling sites were selected. Overall, 17 sampling sites were
included in the survey (Supporting information -Table S1).
[Fig.1]