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

Abstract

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 kLII, the death of period‐two larvae from all mortality factors, whereas in λ contribution method, the key factor was determined as b2&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 kLI‐Z, the death of period‐one larvae from the entomopathogenic fungus, Zoophthora phytonomi (Arthur) Batko (Zygomycetes: Entomophthoraceae), kLII and kLII‐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.

Developmental differences of local populations of alfalfa weevil (Hypera postica) (Coleoptera: Curculionidae)

“…Due to its high abundance, H. postica is the number one pest of alfalfa in Iran (Sanaei et al, 2015a). Many of the previous studies on H. postica in Iran focused on pest management in specific regions (Khanjani and Pourmirza, 2004;Moradi-Vajargah et al, 2011, 2013 without respect to population differences and so far life history traits have only been studied for Hamadan populations (Zahiri et al, 2010a(Zahiri et al, , 2010b(Zahiri et al, , 2014. However, very recently, some morphological variation among Iranian populations has been detected (Sanaei et al, 2015b(Sanaei et al, , 2015c).…”

Evolutionary view on sexual dimorphism and shape variation in Iranian populations of Hypera postica (Coleoptera: Curculionidae)

“…The alfalfa weevil, Hypera postica (Gyllenhal, 1813), is one of the most important insect pests of alfalfa crop in the world (Summers 1998). Many studies have been performed in order to understand the biology of H. postica (Khanjani and Pourmirza 2004;Moradi-Vajargah et al 2011;Zahiri et al 2010aZahiri et al , b, 2014. Except some recent studies (Sanaei et al 2014(Sanaei et al , 2015a there is still a lack of detailed information about Iranian populations of this species.…”