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Modelling of empirical data on the abundance of host-specific, tree-dwelling aphids indicates that their abundance is determined by the effect of the abundance of their host plants on the realised annual population growth rate ( I R i ) of the aphids (Dixon & Kindlmann, [7]). Viewed in this way it is not just the abundance of the host plant of aphids that determines the abundance of aphids (Dixon & Kindlmann, [7]) but also their potential annual population growth rate ( I r i SB p sb ) and subsequently their realised population growth rate ( I R i ). The most striking and consistent feature of rare aphid species is that the period suitable for their development and reproduction is shorter than for the common species and, consequently, the potential yearly rate of increase of these rare species is lower. [Extracted from the article]

1. Following its recent global spread, Harmonia axyridis ( Coleoptera: Coccinellidae), an aphid predator of East Palearctic origin, dominated local coccinellid communities. While long-term trends in this change are well documented, little is known about seasonal changes. 2. Seasonal changes in communities of adult Coccinellidae were investigated in central Europe ( Prague), from April to November in 2010-2014. The beetles were collected at 2-weekly intervals by net-sweeping particular stands of trees ( Tilia spp., Acer spp. and Betula sp.). The numbers of beetles caught were recalculated per unit effort, and average species abundance and community richness, dominance and diversity were calculated for each 2-week period. 3. Frequencies of 21 established species varied throughout the vegetative season and general trends in this variation were similar in each of the 5 years of this study. In May- June the abundant species was Adalia decempunctata, which was later replaced by Harmonia axyridis as the most abundant species in late summer. Coccinella septempunctata colonized trees occasionally in summer. This sequence of species substitution occurred every year and was reset during winter. Species richness decreased and dominance increased during the course of each vegetative season. The diversity of the coccinellid community ( Shannon index H′) significantly decreased during the course of the vegetative season. This was caused by a gradual increase in the dominance of H. axyridis, the abundance of which explained 88% of variation in H′. 4. The existence of a significant seasonal difference indicates that it is important to take this into consideration when comparing coccinellid communities. [ABSTRACT FROM AUTHOR]