Alternatives to key factor analyses for assessing the population dynamics of Hypera postica (Coleoptera: Curculionidae)

• Published in: Population ecology Vol. 56; no. 1; pp. 185 - 194
• Main Authors: Zahiri, Babak, Fathipour, Yaghoub, Khanjani, Mohammad, Moharramipour, Saeid, Zalucki, Myron Philip
• Format: Journal Article
• Language: English
• Published: Tokyo Springer Japan 2014; Blackwell Publishing Ltd
• Subjects: Alfalfa; Alfalfa weevil; Animal populations; Behavioral Sciences; Biomedical and Life Sciences; Coleoptera; Curculionidae; Density dependence; Discriminant analysis; Ecology; Eggs; Entomophthoraceae; Environmental management; Evolutionary Biology; Forestry; Hypera postica; Insects; Larvae; Life Sciences; Mathematical models; Mortality; Multiple decrement life table; Original Article; Plant Sciences; Population density; Population growth; Population regulation; Stage‐structured population; Zoology; Zygomycetes; Population regulation; Density dependence; Stage-structured population; Alfalfa weevil; Multiple decrement life table
• ISSN: 1438-3896; 1438-390X
• DOI: 10.1007/s10144-013-0402-5

Key factors are those causes that are most responsible for the observed changes in population density between generations. Stage-frequency of alfalfa weevil was modeled using Manly-1997 model. Multiple decrement life table parameters from an 8 year-field study were analyzed using traditional and λ contribution methods. In traditional method, the key factor was determined as k LII , the death of period-two larvae from all mortality factors, whereas in λ contribution method, the key factor was determined as b 2&3 , oviposition rate of females per square meter. These differences result directly from the sensitivity of the population growth rate, λ , to variation of both k and b in various stages of the weevil. Among all mortality factors, only k LI-Z , the death of period-one larvae from the entomopathogenic fungus, Zoophthora phytonomi (Arthur) Batko (Zygomycetes: Entomophthoraceae), k LII and k LII-Z , the death of period-two larvae from Z. phytonomi , acted in a density dependent fashion. Remaining factors were independent of population densities affected. Using λ contribution method, life table approach still remains a major way of studying the dynamics of field populations for applied ecologists and population managers.