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Comparison of two population‐level ecotoxicological endpoints: The intrinsic ( r m ) and instantaneous ( r i ) rates of increase
Author(s) -
Walthall William K.,
Stark John D.
Publication year - 1997
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620160529
Subject(s) - acyrthosiphon pisum , population dynamics , vicia faba , imidacloprid , pisum , biology , population , aphid , zoology , botany , horticulture , toxicology , pesticide , aphididae , ecology , fecundity , homoptera , pest analysis , demography , sociology
The instantaneous rate of increase ( r i ) was compared to the intrinsic rate of increase ( r m ) as an alternative population‐level ecotoxicological endpoint. The terrestrial arthropod Acyrthosiphon pisum Harris, the pea aphid, was used as the model species and the new nicotinergic insecticide, imidacloprid, as the xenobiotic. In the first experiment, r m was generated each day from a life table for A. pisum neonates exposed to nontreated (control) potted broad bean, Vicia faba L. (variety Banner), and compared to determine the earliest r m which was not significantly different from the final r m . The r m for neonates introduced to nontreated plants was significantly different on days 6 and 7 but not significantly different between 8 to 40 d postintroduction. A second experiment examined the change in r i over time for neonates introduced at birth to nontreated broad bean and censused at 8, 11, 13, 15, 17, 19, and 21 d postintroduction. The r i for neonate populations introduced to nontreated broad bean peaked on days 11 and 19. The r i on nontreated beans was significantly different ( p < 0.05) from r m on days 8 and 15 but not significantly different at 11, 13, 17, 19, and 21 d. A third experiment was conducted comparing r m and r i following 11 d exposure to a range of imidacloprid concentrations applied to broad bean. There was a high correlation ( r = 0.91, n = 21, p < 0.01) between r i and r m 11 d after the start of the study, suggesting that r i can be used as a predictive measure in place of r m . There was a negative relationship, y = 0.32 – 0.43 x ( r 2 = 0.88, n = 21), between r i and exposure to imidacloprid‐treated broad bean, suggesting that simple regressions may be utilized as tools in the assessment of xenobiotics on population growth rates.