Impacts of abiotic and biotic factors on terrestrial leeches in Indonesian Borneo

Haemadipsid leeches are ubiquitous inhabitants of tropical and sub‐tropical forests in the Indo‐Pacific region. They are increasingly used as indicator taxa for biomonitoring, yet very little is known about their basic ecology. For example, to date no study has assessed the occurrence and distribution of haemadipsid leeches across naturally occurring gradients within intact habitats. We analyzed a long‐term data set (2012–2020) on the closely related tiger (Haemadipsa picta) and brown (Haemadipsa spp.) leech species to investigate if and how abiotic and biotic factors influence their occurrence across a gradient of forest types at an undisturbed tropical rainforest site in Indonesian Borneo. We compared a series of negative binomial mixed models and found that, of the abiotic factors, soil moisture had the largest positive effect on encounter rates of both leech species. Among biotic factors, forest type had differential effects on counts of the two species: while tiger leech counts were greater in low elevation forest types, brown leech counts were greater in high elevation forest types. Additionally, we found that the presence of one species had a positive effect on the presence of the other species. Finally, our results show that the tiger leech has a narrower distribution, being restricted to lower elevation forest types with higher water retention, suggesting that the tiger leech could be more sensitive to lower soil moisture levels. in Indonesian is available with online material. Bahasa Indonesia Pacet haemadipsid adalah penghuni hutan tropis dan sub‐tropis, yang hidup di kawasan Indo‐Pasifik. Mereka seringkali digunakan sebagai taksa indikator untuk biomonitoring, namun sangat sedikit yang diketahui tentang ekologi dasar mereka. Sebagai contoh, sampai saat ini tidak ada penelitian yang menilai keberadaan dan distribusi pacet haemadipsid di seluruh gradien alami di dalam habitat yang masih utuh. Kami telah menganalisis dari kumpulan data jangka panjang (2012–2020) tentang spesies pacet harimau (Haemadipsa picta) dan coklat (Haemadipsa spp.) yang memiliki kekerabatan dekat, untuk menyelidiki apakah dan bagaimana faktor abiotik dan biotik dapat memengaruhi kemunculannya di seluruh gradien tipe hutan pada suatu lokasi hutan hujan tropis yang tidak terganggu di Kalimantan, Indonesia. Kami membandingkan serangkaian model campuran binomial negatif dan menemukan bahwa, dari faktor abiotik, kelembaban tanah memiliki efek positif terbesar pada tingkat pertem