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Elevational patterns in predation, herbivore performance and herbivory in hostile and enemy free space Katerina Sam, Bonny Koane, Peter A. Konga, Lucia Chmurova, Vojtech Novotny Biology Centre CAS, Institute of Entomology, Czech Republic, The New Guinea Binatang Research Center, Papua New Guinea [email protected] HYPOTHESES • Bats, birds and ants are important predators • Predators can enhance plant growth by reducing abundance of herbivores • Strength of such trophic cascades are often variable both within and between communities STUDY SITES Mt Wilhelm – Papua New Guinea 1200 200 700 2200 1700 3700 3200 2700 8 study sites separated by 500 m elevational distance, from 200 to 3700 m asl STUDY SITES Examples of the forest type at each study site METHOD Treatments Main experiment: 80 saplings (DBH = 10 ± 2.5 cm; ca. 3 – 4 m high) per elevational site 4 treatments – 20 saplings each 1) Control 2) Ant removal 30 cm 3) Ant + vertebrate removal In separate experiment at 200, 700, 2200 and 2700 m a.s.l 5) Bat removal 6) Bird removal (+ Control) - cages pulled up and down daily 4) Vertebrate removal - permanently placed cages 2x2x3m METHOD Saplings selected, treated and exposed for 176 ± 8 days Two collections made within a year 2014 2014 2015 1. Collection – non-destructive; all arthropods + ca. 50-100 leaves collected + number of all leaves estimated 2. Collection – destructive; all arthropods + all leaves removed (tree not cut-down) METHOD – Arthropod sampling METHOD – Insect sampling • Insect identified into orders or families, feeding guilds, age + measured METHOD – Leaf herbivory work 26,567 leaves analysed from 1. collection from 560 trees 28,389 leaves from 2. collection Mean total leaf area per sapling = 8.2 ± 3.4 m2 ca. 4,600 m2 of leaves involved in project METHODS – Survey of predators Ant work Bat work Bird work OTHER RELATED WORK – Survey of predators BIRD SURVEY – 33,639 individuals recorded – 241 species • 1,354 individuals mist-netted – 105 species, food surveyed Species richness 9 Abundance 1 BAT SURVEY – similar pattern, ca. 38 species – 496 individuals trapped and 283 “individuals” recorded ANT SURVEY – 4 sampling methods, 232 species, 7,611 individuals RESULTS – Insect Total ALL (mean±SE) VER RESULTS – Arthropods Guilds (mean±SE) / RESULTS – Arthropods Body Sizes Control community (mean±SE) RESULTS – Herbivory (mean±SE) RESULTS – Insect Total RESULTS – Herbivory *** *** ** ** ** ** CONCLUSIONS • Exclusion of vertebrates has positive effect on • • • • abundances of arthropods - This effect decreases with increasing elevation Exclusion of ants have little or no effect on abundances of arthropods - This effect appears only at lowest elevations Mesopredators (i.e. spiders, wasps) seems to compensate for removed predators at low elevations only Exclusion of predators changes size composition of arthropod communities Exclusion of predators leads to higher herbivorous damage THANK YOU FOR YOUR ATTENTION Follow the project Web page: http://tvardikova.weebly.com/ Email: [email protected] Acknowledgements Staff of The New Guinea Binatang Research Center Numerous village assistants from Kausi, Numba, Bundi, Sinopass, Bruno Sawmill and Kegesugl for assistance Czech Science Foundation Grant 1432024P Peter Amick Bonny Koane