Conservation outcomes could be greatly enhanced if strategies addressing anthropogenic land-use change considered the impacts of these changes on entire communities as well as on individual species. Examining how species interactions change across gradients of habitat disturbance allows us to predict the cascading consequences of species extinctions and the response of ecological networks to environmental change. We conducted the first detailed study of changes in a commensalist network of mammals and dung beetles across an environmental disturbance gradient, from primary tropical forest to plantations, which varied in above-ground carbon density (ACD) and mammal communities. Mammal diversity changed only slightly across the gradient, remaining high even in oil palm plantations and fragmented forest. Dung beetle species richness, however, declined in response to lower ACD and was particularly low in plantations and the most disturbed forest sites. Three of the five network metrics (nestedness, network specialization and functionality) were significantly affected by changes in dung beetle species richness and ACD, but mammal diversity was not an important predictor of network structure. Overall, the interaction networks remained structurally and functionally similar across the gradient, only becoming simplified (i.e. with fewer dung beetle species and fewer interactions) in the most disturbed sites. We suggest that the high diversity of mammals, even in disturbed forests, combined with the generalist feeding patterns of dung beetles, confer resilience to the commensalist dung beetle-mammal networks. This study highlights the importance of protecting logged and fragmented forests to maintain interaction networks and potentially prevent extinction cascades in human-modified systems.
Hasil pemuliharaan boleh dipertingkat dengan lebih baik sekiranya strategi menangani kesan manusia menitikberatkan keseluruhan komuniti melainkan spesies individu. Kajian tentang interaksi spesies berubah merentas gangguan habitat membolehkan kita meramalkan akibat kepupusan spesies dan tindak balas rangkaian ekologi terhadap perubahan alam sekitar. Kami menjalankan kajian terperinci pertama tentang perubahan dalam rangkaian komensal haiwan dan kumbang tahi merentasi gangguan alam sekitar, daripada hutan tropika primer kepada ladang, yang mempunyai perbezaan dalam kepadatan karbon atas tanah (ACD) dan komuniti haiwan. Kepelbagaian haiwan hanya berubah sedikit merentasi gangguan habitat, kepelbagaiannya kekal tinggi walaupun di ladang kelapa sawit dan fragmentasi habitat. Kepelbagaian spesies kumbang tahi, bagaimanapun, menurun sebagai tindak balas kepada ACD terutamanya di ladang dan hutan yang terganggu. Tiga daripada lima metrik rangkaian (“nestedness”, pengkhususan rangkaian dan kefungsian) terjejas dengan ketara oleh perubahan dalam spesies kumbang tahi dan ACD, tetapi kepelbagaian haiwan bukanlah peramal penting dalam struktur rangkaian. Secara keseluruhannya, rangkaian interaksi kekal sama dari segi struktur dan fungsi merentasi gangguan habitat, tetapi dipermudahkan (iaitu, dengan lebih sedikit spesies kumbang tahi dan lebih sedikit interaksi) di habitat yang terganggu. Kami mencadangkan bahawa kepelbagaian haiwan yang tinggi, walaupun di dalam hutan yang terganggu, digabungkan dengan pola pemakanan umum kumbang tahi, memberikan daya tahan kepada rangkaian kumbang tahi - haiwan. Kajian ini menonjolkan kepentingan menjaga hutan yang dibalak dan fragmentasi untuk mengekalkan rangkaian interaksi dan berpotensi dalam mencegah kepupusan dalam sistem yang dipengaruhi oleh manusia.
Keywords: Borneo; Scarabaeidae; above-ground carbon; commensalist networks; ecological network; habitat modification; land-use gradient; species interactions.
© 2021 British Ecological Society.