Island Site Code Vegetation/land use Hydraenaspecies recorded PAL1 CR1 Disturbed primary forest H. hosiwergi, H. kodadai, H. nielshaggei, H. pseudopalawanensis, H. zetteli PAL1 CR2 Secondary forest H. nielshaggei, PAL1 CR3 Paddy fields/ farmland H. palawanensis, H. pseudopalawanensis PAL1 CR4 Disturbed Primary forest* H. zetteli PAL1 LS4 Primary forest H. claudia, H. palawanensis, H. pseudopalawanensis, H. zetteli PAL1 NC3 Secondary forest H. hosiwergi, H. palawanensis, H. pseudopalawanensis PAL1 PR1 Secondary vegetation H. jojoorculloi, H. kodadai, H. sp.2 PAL1 18 Secondary forest H. castanescens PAL1 19 Secondary forest H. kodadai PAL2 11 Disturbed primary forest/ secondary vegetation H. claudia, H. castanescens, H. hosiwergi, H. jojoorculloi, H. kodadai, H. palawanensis, H. scabra PAL2 13 Disturbed primary forest/ H. claudia, H. hosiwergi, H. jojoorculloi, H. kodadai, H. manguao, H.scabra PAL2 63 Disturbed primary forest/ H. claudia, H. jojoorculloi, H. kodadai, H. palawanensis, H. sp.2, H. sp.E PAL2 64 Secondary forest/reforestation H. claudia, H. hosiwergi, H. manguao, H. palawanensis, H. scabra PAL2 65 Secondary vegetation/ farmland H. hosiwergi, H. palawanensis, PAL2 66 Secondary vegetation/ paddy fields H. manguao PAL2 67 Secondary forest H. kodadai, H. palawanensis PAL2 68 Secondary forest H. hosiwergi, H. manguao, H. palawanensis, H. sp.2, H. sp.E PAL2 71 Secondary forest H. claudia, H. hosiwergi, H. palawanensis PAL2 72 Secondary forest H. claudia, H. hosiwergi, H. manguao, H. palawanensis PAL2 73 Secondary vegetation/ secondary forest H. hosiwergi, H. jojoorculloi, PAL2 74 Secondary forest/reforestation H. hosiwergi, H. kodadai PAL2 78 Secondary vegetation H. sp.D PAL2 100 Degraded forestsecondary forest H. hosiwergi, H. kodadai PAL2 101 Secondary forest H. claudia, H. hosiwergi PAL2 119 Disturbed primary forest H. claudia, H. hosiwergi, H. kodadai, H. manguao, H. palawanensis PAL2 120 Disturbed primary forest H. hosiwergi, H. kodadai PAL2 121 Disturbed primary forest H. claudia, H. castanescens, H. hosiwergi, H. palawanensis PAL2 122 Disturbed primary forest H. claudia, H. castanescens, H. hosiwergi, H. kodadai PAL2 146** Disturbed primary forest H. hosiwergi PAL2 177** Disturbed primary forest H. claudia, H. hosiwergi   MIN   1**   Secondary vegetation NONE MIN 2** Farmland &secondary vegetation H. palawanensis, H. scabra, H. sp.A,H. sp.B MIN 3** Farmland &secondary vegetation H. scabra, H. sp.A,H. sp.B,, H. sp.C LUZ ADM1 Secondary vegetation/ polluted NONE LUZ ADM2 Secondary vegetation/ unpolluted H. ateneo, H. palawanensis, H. scabra LUZ ADM3 Secondary vegetation / unpolluted H. ateneo, H. palawanensis, H. scabra LUZ ADM4 Secondary vegetation/ eutrophic NONE LUZ ADM5 Secondary vegetation/ eutrophic NONE SIN BB Secondary vegetation/ secondary forest H. paulmoritz SIN BG Secondary vegetation/ park H. jacobsoni SIN BT Primary Forest H. formula, H. hendrichi, H. jacobsoni, H. paulmoritz SIN KR Secondary vegetation/ secondary forest H. paulmoritz SIN LP Secondary forest H. jacobsoni, H. paulmoritz SIN MR Secondary forest/disturbed primary forest H. michaelbalkei, H. singaporensis SIN NS Primary forest H. formula, H. jacobsoni, H. paulmoritz, H. singaporensis SIN RR Secondary forest/disturbed primary forest H. formula, H. yangae SIN RS Secondary vegetation H. jacobsoni, H. paulmoritz SIN SB Secondary (?) swamp/ mangrove forest H. paulmoritz SIN UP Secondary forest H. singaporensis

Table 2: List of sampling sites of Hydraena surveys (see Material and Methods) with land-use and forest classification and list of recorded species. * this river section is situated in disturbed primary forest, but very close to upstream farmlands; **single, non-replicated sampling; label codes as in the original publication except for: BB=Bukit Batok Nature Park; BG=Botanical Gardens; BT=Bukit Timah Nature Reserve; KR=Kranji Reservoir; LP=Lower Peirce Reservoir; MR=MacRitchie Reservoir; NC3 =Nagdayan Creek; NS=Nee Soon Swamp Forest; RR=Stream near Rifle Range Road (east Bukit Timah); RS=River Sembawang/Senoko (habitat destroyed); SB=Sungai Buloh Wetland Reserve; UP=Upper Peirce Forest.