Spatial autocorrelation as a tool for identifying the geographical patterns of aphid annual abundance

Abstract

1 A spatial autocorrelation analysis was undertaken to investigate the spatial structure of annual abundance for the pest aphid Myzus persicae collected in suction traps distributed across north-west Europe. 2 The analysis was applied at two different scales. The Moran index was used to estimate the degree of spatial autocorrelation at all sites within the study area (global level). The contributions of each site to the global index were identified by the use of a local indicator of spatial autocorrelation (LISA). A hierarchical cluster analysis was undertaken to highlight differences between groups of resulting correlograms. 3 Similarity between traps was shown to occur over large geographical distances, suggesting an impact of phenomena such as climatic gradients or land use types. 4 The presence of outliers and zones of similarity (hot-spots) and of dissimilarity (cold-spots) were identified indicating a strong impact of local effects. 5 Several groups of traps characterized by similarities in their local spatial structure (correlograms, value of Moran's I i ) also had similar values for land use variables (the area occupied by agricultural zones, forest and sea). 6 It is concluded that trap data can provide information about Myzus persicae that is representative of large geographical areas. Thus, trap data can be used to estimate the aerial abundance of this species, even if the suction traps are not regularly and densely distributed.

Onwards and upwards – aphid flight trends follow climate change

“…The suction trap data set for Silwood Park was incomplete so could not be used in the analysis although the trend was similar. The existence of such a strong relationship despite the two sites being 47 km away from each other supports the contention that the distribution and number of suction traps in the United Kingdom are justified (Cocu et al 2005).…”

“…This is an important consideration as cold winters cause greater mortality to those aphids that overwinter anholocyclically (i.e. not as eggs, but as adults or immature stages) than to those that overwinter as eggs (holocyclically) (Leather 1993;Cocu et al 2005). In addition, they then attempted to explain some of the variability found in the observed phenological patterns by taking into account life cycle type, that is whether host-alternating (heteroecious; approximately 10% of aphids are heteroecious) or non-host-alternating (monoecious).…”

“…The emergence of new pests, either by invasion from elsewhere or by the ability of some native aphid species to bet-hedge (Cocu et al 2005) by producing more anholocyclic clones as suggested by Bell et al (2015) in this issue, will be dependent on phenological matching of host plants and aphids; cropping patterns are changing in response to climate change (Sacks et al 2010), and it has been suggested that insects and their food plants do not necessarily behave similarly in relation to climate change (Yang & Rudolf 2010;Kudo & Ida 2013). Certainly, as pointed out by Bell et al (2015), although flight phenology may have changed, not all aphids have increased in overall abundance; for example, Hyalopterus pruni and Aulacorthum solani seem to be becoming less common, Fig.…”

Seasonal Phenology and Species Composition of the Aphid Fauna in a Northern Crop Production Area

“…The 12.2 m high Rothamsted suction trap provides information about the composition and long distance movement of aphid taxa in large areas and helps to recognise an overall increase in the risk of pest problems and virus transmission [65],[66]. Local differences may be important for aphid control programmes where monitoring of aphids in the field informs the threshold risk level of virus transmission and the moment to begin measures for control of aphids.…”

Use of Moran’s I and Robust Statistics to Separate Geochemical Anomalies in Juirui Area (Southeast China)

“…The spatial weight matrix computed from a given distance is row-standardized so that the sums of the weights for a trap are equal to one (Cocu, 2005):…”