A key-factor analysis of population fluctuations in Andraca bipunctata Walker (Lepidoptera: Bombycidae)

AbstractThe causes of fluctuation and stabilisation in a population of Andraca bipunctata Wlk. on tea in India were assessed over three years using the technique of key-factor analysis. Failure to produce the maximum complement of eggs, together with female mortality and adult migration, is shown to be the key-factor. Other mortality factors include non-viability of eggs and parasitism of the caterpillars by the tachinid Cylindromyia sp. Mortality of the female pupae tends to stabilise the population by compensating for losses due to the key-factor, but neither this nor any other mortality factors appear to be significantly density-dependent. The need for devising specialised sampling procedures and statistical tests for tropical insect populations is discussed.

Download Full-text

Population dynamics of Saissetia oleae. II. Life-tables and key-factor analysis

ENTOMOLOGIA HELLENICA ◽

10.12681/eh.13983 ◽

2017 ◽

Vol 8 ◽

pp. 59 ◽

Cited By ~ 2

Author(s):

E. T. Kapatos ◽

E.T. Stratopoulou

Keyword(s):

Factor Analysis ◽

Population Dynamics ◽

Population Change ◽

Life Tables ◽

Population Fluctuations ◽

Mortality Factors ◽

Population System ◽

Key Factor ◽

Key Factor Analysis ◽

Table Data

A series of life-tables for the population of Saisselia oleae (Oliv.) (Homoptera: Coccidae) during five yearly generations (1981-86) were constructed in Corfu. Key-factor analysis carried out on the life-table data indicated that mortality of young stages during summer, caused mainly by the high temperatures, and mortality during spring, caused mainly by predation, determine total population change within each generation. These two mortality factors are the predominant factors of the population dynamics of S. oleae determining population fluctuations. The other mortality factors of the population system of S. oleae were less important. Summer parasites and egg predators, in particular, do not play any significant role on the population dynamics of S. oleae.

Download Full-text

Key-factor analysis of immature stages of Aedes scapularis (Diptera: Culicidae) populations in southeastern Brazil

Bulletin of Entomological Research ◽

10.1079/ber2002178 ◽

2002 ◽

Vol 92 (4) ◽

pp. 271-277 ◽

Cited By ~ 7

Author(s):

C. Casanova ◽

A.P. do Prado

Keyword(s):

Larval Instar ◽

Southeastern Brazil ◽

Population Fluctuations ◽

Mortality Factors ◽

Breeding Sites ◽

Final Population ◽

Key Factor ◽

Synchronous Development ◽

Population Sizes ◽

Key Factor Analysis

AbstractDevelopment times and mortality factors were investigated for populations of Aedes scapularis (Rondani) occurring in natural temporary ground pools in southeastern Brazil. Analysis of life tables by the key-factor method showed that mortality caused by desiccation of breeding sites was the principal factor accounting for fluctuations in population sizes throughout the study period. For cohorts that completed development, mortality attributed to predation by aquatic insects ranged from 68 to 96% and was the most important cause of death. In these cohorts, final population size was determined by the high mortality rates that occurred during the fourth larval instar and pupal stages; however, the key-factor best accounting for the population fluctuations was predation of fourth instar larvae. The short mean time of 7.1 days for synchronous development of the larvae and the lack of evidence of density-dependent mortality suggested that the A. scapularis populations were not strongly regulated and can attain relatively high densities.

Download Full-text

Detecting Population Regulation of Winter Flounder from Noisy Data

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2021-0004 ◽

2022 ◽

Author(s):

Joseph A. Langan ◽

Jeremy S. Collie ◽

Cóilín Minto

Keyword(s):

Factor Analysis ◽

Class Size ◽

Life Stage ◽

Population Decline ◽

Winter Flounder ◽

Data Availability ◽

Life Stages ◽

Density Dependent ◽

Key Factor ◽

Key Factor Analysis

Year-class size of marine fish is thought to be determined during the first year of life, with density-dependent mortality during the larval or juvenile stages. However, investigations of such dynamics are often limited by data availability. To test this paradigm for winter flounder (Pseudopleuronectes americanus) in Narragansett Bay, Rhode Island, the abundances of 29 year classes moving through seven life stages were analyzed with a novel extension of key-factor analysis. Evidence of density dependence was identified between the egg and July young-of-the-year stages and high process-error variance was detected throughout the life cycle, suggesting year-class size is not fully determined until age-2. However, the first summer appeared to be a critical life stage for winter flounder, during which high temperatures, hypoxia, and predator abundance contributed to increased mortality rates behind a long-term population decline. Due to its general data requirements, the key-factor analysis method developed here may be applied to other marine populations to identify the impacts of external stressors at particular life stages and the degree to which they are compensated by density-dependent processes.

Download Full-text