Pest risk analysis for Myriophyllum heterophyllum

Myriophyllum heterophyllum presents an overall high phytosanitary risk for the EPPO region with a low uncertainty rating. The overall likelihood of M. heterophyllum continuing to enter the EPPO region is high. The plant is imported into the EPPO region as a misidentified aquatic species for aquaria and ponds and is already established in Austria, Belgium, France, Germany, Hungary, the Netherlands, Spain and Switzerland. The risk of entry into other EPPO countries through import is considered high. The risk of the species establishing in additional countries is high as movement through irrigation and river systems acts to connect countries, facilitating spread regionally. Spread may be accelerated by recreational activities in water bodies invaded by the weed. Impacts of the species within the EPPO region are likely to be severe (high score rating), including aquatic plant species displacement, habitat dominance and effects on other aquatic organisms

Pest risk analysis for Alternanthera philoxeroides

Alternanthera philoxeroides presents a high phytosanitary risk for the EPPO region with a low uncertainty rating. A. philoxeroides is already present in the EPPO region in France and Italy. Further spread within and between EPPO countries is considered likely. The overall likelihood of A. philoxeroides continuing to enter the EPPO region is medium. It is not clear how this species entered the EPPO region and there are no clear pathways of further introduction, as the species is not widely traded as an aquarium plant or as any other type of living plant material. There may be confusion with A. sessilis, or other Alternanthera species traded for aquarium, ornamental or food purposes. The risk of the species establishing in other EPPO countries is considered high as movement through irrigation and river systems may act to connect countries, facilitating spread regionally, especially through high energy unstable river systems that may encourage fragmentation. Spread may be significantly accelerated by water based recreational activities. The potential high impact of the species within the EPPO region should be considered similar to that seen in other countries where the species has invaded and become established; i.e. Australia and the southern states of North America. Impacts are likely to be more pronounced in countries and regions where the climate most suited to population, establishment, growth and spread

Impact of three aquatic invasive species on native plants and macroinvertebrates in temperate ponds

Biological plant invasions pose a serious threat to native biodiversity and have received much attention, especially in terrestrial habitats. In freshwater ecosystems impacts of invasive plant species are less studied. We hypothesized an impact on organisms from the water column and from the sediment. We then assessed the impact of three aquatic invasive species on the plants and macroinvertebrates: Hydrocotyle ranunculoides, Ludwigia grandiflora and Myriophyllum aquaticum. Our research on 32 ponds in Belgium indicated that the reduction in the native plant species richness was a common pattern to invasion. However, the magnitude of impacts were species specific. A strong negative relationship to invasive species cover was found, with submerged vegetation the most vulnerable to the invasion. Invertebrate richness, diversity and abundance were measured in sediments of invaded and uninvaded ponds along a gradient of H. ranunculoides, L. grandiflora, and M. aquaticum species cover. We found a strong negative relationship between invasive species cover and invertebrate abundance, probably due to unsuitable conditions of the detritus for invertebrate colonization. Taxonomic compositions of aquatic invertebrate assemblages in invaded ponds differed from uninvaded ponds. Sensitive benthos, such as mayflies were completely absent in invaded ponds. The introduction of H. ranunculoides, L. grandiflora, and M. aquaticum in Belgian ponds has caused significant ecological alterations in the aquatic vegetation and the detritus community of ponds. © 2011 Springer Science+Business Media B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fluorescent dye particles as pollen analogues for measuring pollen dispersal in an insect-pollinated forest herb

In flowering plants, pollen dispersal is often the major contributing component to gene flow, hence a key parameter in conservation genetics and population biology. A cost-effective method to assess pollen dispersal consists of monitoring the dispersal of fluorescent dyes used as pollen analogues. However, few comparisons between dye dispersal and realized pollen dispersal have been performed to validate the method. We investigated pollen dispersal in two small populations of the insect-pollinated herb Primula elatior from urban forest fragments using direct (paternity analyses based on microsatellite DNA markers) and indirect (fluorescent dyes) methods. We compared these methods using two approaches, testing for the difference between the distance distributions of observed dispersal events and estimating parameters of a dispersal model, and related these results to dye dispersal patterns in three large populations. Dye and realized (based on paternity inference) pollen dispersal showed exponential decay distributions, with 74.2-94.8% of the depositions occurring at < 50 m and a few longer distance dispersal events (up to 151 m). No significant difference in curve shape was found between dye and realized pollen dispersal distributions. The best-fitting parameters characterizing the dye dispersal model were consistent with those obtained for realized pollen dispersal. Hence, the fluorescent dye method may be considered as reliable to infer realized pollen dispersal for forest herbs such as P. elatior. However, our simulations reveal that large sample sizes are needed to detect moderate differences between dye and realized pollen dispersal patterns because the estimation of dispersal parameters suffers low precision.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Clonal diversity and structure measures of <i>C</i>. <i>papyrus</i> ramets sampled in three papyrus swamps in Lake Tana under two sedimentation regimes during 2014 and 2016.

<p>Clonal diversity and structure measures of <i>C</i>. <i>papyrus</i> ramets sampled in three papyrus swamps in Lake Tana under two sedimentation regimes during 2014 and 2016.</p

Clonal growth strategy, diversity and structure: A spatiotemporal response to sedimentation in tropical <i>Cyperus papyrus</i> swamps

<div><p>Land degradation and soil erosion in the upper catchments of tropical lakes fringed by papyrus vegetation can result in a sediment load gradient from land to lakeward. Understanding the dynamics of clonal modules (ramets and genets) and growth strategies of plants on such a gradient in both space and time is critical for exploring a species adaptation and processes regulating population structure and differentiation. We assessed the spatial and temporal dynamics in clonal growth, diversity, and structure of an emergent macrophyte, <i>Cyperus papyrus</i> (papyrus), in response to two contrasting sedimentation regimes by combining morphological traits and genotype data using 20 microsatellite markers. A total of 636 ramets from six permanent plots (18 x 30 m) in three Ethiopian papyrus swamps, each with discrete sedimentation regimes (high vs. low) were sampled for two years. We found that ramets under the high sedimentation regime (HSR) were significantly clumped and denser than the sparse and spreading ramets under the low sedimentation regime (LSR). The HSR resulted in significantly different ramets with short culm height and girth diameter as compared to the LSR. These results indicated that <i>C</i>. <i>papyrus</i> ameliorates the effect of sedimentation by shifting clonal growth strategy from guerrilla (in LSR) to phalanx (in HSR). Clonal richness, size, dominance, and clonal subrange differed significantly between sediment regimes and studied time periods. Each swamp under HSR revealed a significantly high clonal richness (<i>R</i> = 0.80) as compared to the LSR (<i>R</i> = 0.48). Such discrepancy in clonal richness reflected the occurrence of initial and repeated seedling recruitment strategies as a response to different sedimentation regimes. Overall, our spatial and short-term temporal observations highlighted that HSR enhances clonal richness and decreases clonal subrange owing to repeated seedling recruitment and genets turnover.</p></div

Relationship between clonal growth, diversity and structure parameters for papyrus populations data collated for two sediment regimes in two years (Spearman’s correlation coefficient).

<p>Relationship between clonal growth, diversity and structure parameters for papyrus populations data collated for two sediment regimes in two years (Spearman’s correlation coefficient).</p

Map of Lake Tana with the papyrus swamps studied and the proportion of genets evolved temporally across two sediment regimes.

<p>Blue represents genets only evolved in 2014, red only in 2016, and green in both years. Where 1 = HSR and 2 = LSR The map is reprinted from Chebud and Melese [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190810#pone.0190810.ref057" target="_blank">57</a>] under a CC BY license, with permission from [John Wiley and Sons], and with the original copyright [2009] used as a shapefile.</p

Clonal growth traits of <i>C</i>. <i>papyrus</i> across sedimentation regimes.

<p>Clonal growth traits of <i>C</i>. <i>papyrus</i> across sedimentation regimes.</p