caa a22 4500 469097647 CHVBK 20180323133035.0 cr unu---uuuuu 170328e19920901xx s 000 0 eng 10.1007/BF00317619 doi (NATIONALLICENCE)springer-10.1007/BF00317619 Sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system [Elektronische Daten] [S. Hanhimäki, J. Senn] Summary: Studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. Here we report the results of a study which examined causes of this variation. We bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch Betula pubescens ssp. tortuosa by measuring the growth of two instars of Epirrita autumnata larvae. We used only short shoot leaves from trees of a natural stand, uniform in size and age. Damage was caused by larvae and artificial tearing of leaf lamina, varying the scale and time. We separated seasonal changes in plants from instar-dependent effects of the animals by testing experimental larvae in two subsequent growth trials. We found that only larval-made damage induced responses in leaves that made the leaves significantly poorer quality for the test larvae. Artificial damage induced only weak responses, and artificial canopy-wide damage even caused slight improvement of leaf quality. Cumulative leaf damage did not strengthen birch responses. Leaves that were in the expansion phase responded to damage while fully-expanded, mature leaves showed no response. The pattern of responses indicated that there might be physiological constraints: small-scale damage induced resistance against the larvae but largescale damage did not. Prevalent weather conditions might have modified these responses. Larvae of two instars and sexes, of low- and high-density populations responded to leaf damage similarly. However, prior experience of larvae with the host plant may have affected subsequent larval performance. Variation in rapidly inducible responses in birches was caused by plant characters rather than by test animals. Springer-Verlag, 1992 Betula pubescens nationallicence Epirrita autumnata nationallicence Rapidly inducible responses nationallicence Phenology nationallicence Conditioning nationallicence Hanhimäki S. Laboratory of Ecological Zoology, Department of Biology, University of Turku, SF-20500, Turku, Finland aut Senn J. Laboratory of Ecological Zoology, Department of Biology, University of Turku, SF-20500, Turku, Finland aut Oecologia Springer-Verlag 91/3(1992-09-01), 318-331 0029-8549 91:3<318 1992 91 442 https://doi.org/10.1007/BF00317619 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00317619 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Hanhimäki S. Laboratory of Ecological Zoology, Department of Biology, University of Turku, SF-20500, Turku, Finland aut NATIONALLICENCE 700 1- Senn J. Laboratory of Ecological Zoology, Department of Biology, University of Turku, SF-20500, Turku, Finland aut NATIONALLICENCE 773 0- Oecologia Springer-Verlag 91/3(1992-09-01), 318-331 0029-8549 91:3<318 1992 91 442 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer