Cydalima perspectalis in Poland—8 Years of Invasion against the Background of Three Other Invasive Species

The box tree moth (Cydalima perspectalis) origins from East Asia. In Europe, it was recorded for the first time in 2007, and in Poland in 2012. By the end of 2020, it was found all over Poland. There are no published data on the range of C. perspectalis occurrence in Poland because it is not a quarantine pest in the European Union and is not subject to official monitoring. Data collected in 2018–2020 via a website dedicated to monitoring, for the first time, illustrate the current range and its largest concentrations in southern and central Poland. The monitoring confirmed that the main directions of the invasion are related to the main communication routes of Poland (south-north) and are of a long-distance character. The dispersal pattern corresponds to the model developed for Cameraria ohridella: a stratified dispersal model that considers long-distance road/rail transport. The second important factor contributing to the invasion of C. perspectalis are large human communities enabling rapid local dispersion (a diffusion model). Comparing its invasion with the monitoring data from 2007–2013 of two other invasive pests of Poland: Ostrinia nubilalis and Diabrotica virgifera, shows that a diffusion model best describes the spatial spread of these pests only to uninhabited neighboring areas.

Long-Distance Dispersal and Diffusion in the Invasion of Lonicera maackii

To investigate the relative importance of long-distance dispersal vs. diffusion in the invasion of a nonnative plant, we used age structure to infer the contribution to recruitment of external propagule rain vs. within-population reproduction. We quantified the age structure of 14 populations of Amur honeysuckle in a landscape where it recently invaded, in Darke County, OH. We sampled the largest honeysuckle individuals in each population (woodlots), and aged these by counting annual rings in stem cross sections. Individuals in the oldest four 1-yr age classes are assumed to be from external recruitment, given the minimum age at which shrubs reproduce. We used these recruitment rates to model external recruitment over the next 5 yr and used observed age structures to estimate total recruitment. We used the difference between total and external recruitment to infer the rate of internal recruitment. Our findings indicate that recruitment from within the population is of about the same magnitude as immigration in the fifth to seventh year after population establishment, but by years 8 to 9 internal recruitment dominates. At the landscape scale, the temporal-spatial pattern of population establishment supports a stratified dispersal model, with the earliest populations establishing in widely spaced woodlots, about 4 km from existing populations, and these serving as “nascent foci” for diffusion to nearby woodlots. Understanding the relative importance of long-distance dispersal vs. diffusion will inform management, e.g., whether it is more effective to scout for isolated shrubs or remove reproducing shrubs at the edge of invaded areas.

On the spatial spread of the Rice Water Weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Erirhinidae), in Italy

A five year study has been made to establish the spread of the rice water weevil <em>Lissorhoptrus oryzophilus</em> (Coleoptera: Erirhinidae) in Northern Italy. Data obtained with GPS from 2005 throughout 2009 were first georeferenced with SW ArcGis&reg; 9.2, then overlapped and compared to the map of the European environmental landscape based on the interpretation of satellite images (CORINE Land Cover map) and to the hydrographic chart CT10 (Technical Regional map 10000). The analysis of the radial rate of spread per year indicates a deceleration in the expansion from 10.864 &plusmn; 6.801 km/year in 2005 to 5.318 &plusmn; 1.401 km/year in 2009. In five years the weevil has expanded its distribution in nearly all rice paddies in Lombardy and Piedmont, over an area of about 200,000 ha, which correspond to 86% of the total Italian rice area. Its expansion is thought to follow a type of stratified dispersal, due both to insect adult active dispersal and to accidental movements caused by human transportation.

Colonization with long-distance seed dispersal and genetic structure of maternally inherited genes in forest trees: a simulation study

Since the last glacial period forest trees have expanded to their present range very rapidly, with rates up to 500 m yr−1 for oaks in Europe, which can be explained only by the dispersion of acorns over long distances. We used a stratified dispersal model, including both diffusive and long-distance dispersal of seeds, to simulate the colonization of a 100 km×300 km grid by populations of oak trees. An appropriate rate of spread is obtained with rare dispersal at distances of the order of tens of kilometres. We simulated the effect of stratified versus diffusive dispersal of seeds on the spatial genetic structure at a maternally inherited locus. Founding events associated with stratified dispersal generate a high amount of genetic differentiation among populations, which is likely to persist for a long time after colonization. Using autocorrelation methods, we show that diffusive and stratified dispersals create quite different spatial patterns of variation for the maternally inherited locus. Stratified dispersal creates patchy patterns that are concordant with a previous experimental investigation of chloroplast DNA variation at a regional scale in the oaks Quercus petraea and Quercus robur. For plant populations that have passed through recent episodes of range expansion, long-distance dispersal events are probably the most important factors of spatial genetic structuring of maternally inherited genes at small or medium geographic scales.