Population Dynamics of Tree-Dwelling Aphids: The Importance of Seasonality and Time Scale

Abstract

Changes in the weekly abundance in two natural populations of the Turkeyoak aphid, Myzocallis boerneri, from 1975 to 1992, were analyzed using autoregression methodology to determine the nature of dynamic processes. Seasonality forms the basis of aphid population dynamics. Analysis of time series of weekly and monthly data indicate statistically detectable seasonality in density changes. The monthly data statistically adjusted for seasonal effects (deseasoned) show that density fluctuates around a seasonally changing equilibrium value. Bulmer's test of density dependence applied to the seasonally adjusted monthly data reveals density dependence. The partial autocorrelation function (PACF) plots of smoothed deseasoned monthly density indicate time-lagged density-dependent processes operating between seasons and possibly on a shorter time scale of between 2 wk and 2 mo. The PACFs of smoothed deseasoned data provide statistical evidence for the existence of a ''see-saw'' relationship between density in spring, autumn, and the following spring. Analysis of annual abundances calculated from the weekly data suggests that overall abundance in any year is influenced by abundance the previous year. The pattern of changes in abundance between years is most likely the consequence of the see-saw effect operating between seasons. It is argued that aphid population density is regulated by means of density-dependent processes acting within years, which is reflected in the year-to-year changes in overall abundance.

Microbial impacts on plant-herbivore interactions: the indirect effects of a birch pathogen on a birch aphid

“…The dynamics of tree dwelling aphid populations can vary greatly both between years and within individual seasons (Sequeira and Dixon 1997), so assessing the relative impact of plant-mediated microbial effects relative to other factors is difficult. It has been suggested, however, that the influence of natural enemies and parasitoids on E. betulae populations is generally weak (Hajek and Dahlsten 1988), so such bottom-up impacts could potentially be more influential in shaping natural populations.…”

Spatial and temporal density dependence in a population of melon aphid, Aphis gossypii Glover (Homoptera: Aphididae), on established and sentinel taro plants

“…Aphids (Homoptera: Aphididae) have complex population dynamics often characterized by wide variations of population density, both on a temporal and spatial scale. Analyses of long time-series data reveal that density dependent processes commonly regulate populations of aphids within and between years (Woiwod and Hanski, 1992;Maudsley et al, 1996;Sequeira and Dixon, 1997;Jorošík and Dixon, 1999). Interactions among aphids and their host-plant largely contribute to the regulation of aphid populations, through the intrinsic quality of host plants (Kidd, 1990;Karley et al, 2003) or intraspecific competition on crowded plants resulting in an elevated level of mortality, low reproductive success, and high rate of dispersal among aphids (Dixon, 1971(Dixon, , 1998Day, 1986;Klindmann and Dixon, 1996).…”

Trophobiosis in the arboricolous ant Liometopum microcephalum (Hymenoptera: Formicidae: Dolichoderinae)

“…We assume this was due to the low population densities of aphids at the beginning of the observation period. We have no data on aphid dynamics in this area but substantial increases in the abundance of tree-dwelling aphids from April to May are recorded for temperate regions, for instance, by Sequeira & Dixon (1997), Jarošík & Dixon (1999), Molnár (2003) and Durak (2008). However, we have no explanation for the high gaster mass and low concentration of sugars in workers returning to nest trees in April compared to the other groups of workers (Figs 3, 5, 7).…”