Seasonal patterns of growth, alginate content and block structure of the alien invader Sargassum muticum (Fucales, Ochrophyta) from the Atlantic coast of Morocco

In the present study, alginate yield and composition were investigated during the seasonal life cycle of the alien brown alga Sargassum muticum harvested from the Atlantic coast of Morocco. Alginate yield ranged from 11.14% in winter to 25.62% in spring/early summer, coinciding with maximum vegetative growth. Monthly monitoring of the alginate block structure showed that the highest mannuronate (M)/guluronate (G) ratio was recorded during the maximum development of S. muticum, before sexual maturity and during resumption of vegetative growth, giving maximum flexibility to the alga. The unusually high molar monad fractions (FG) and dyad fractions (FGG) of guluronic acid in late summer/early autumn appeared to be related to stiffness of senescent thalli. Rheological characterisation showed that the alginate of S. muticum exhibited pseudoplastic behaviour, with the highest apparent viscosities measured in late summer/early autumn when the G blocks dominated the alginate structure. This study suggests that S. muticum could be exploited as an alginophyte for commercial applications. The best harvest time is May-June, which corresponds to the highest alginate yield, maximum thallus growth, and largely completed sexual reproduction, ensuring sustainable exploitation of the species.

Pinna nobilis in the south Marmara Islands (Sea of Marmara); it still remains uninfected by the epidemic and acts as egg laying substratum for an alien invader

A total of 12 Pinna nobilis beds were found and studied at depths varying between 2 and 6 m in the south Marmara Islands (Sea of Marmara). Fan mussel individuals in the beds were healthy with a few old dead specimens, indicating that the epidemic, which has devastated P. nobilis populations in the Mediterranean Sea, has not reached the Sea of Marmara, making the region a refuge area for the species. The average density of P. nobilis in the area varied between 0.6 ind.10 m-2 and 24 ind.10 m-2. The P. nobilis shells overall provided substrata or refuge for 14 species (10 sessile and 4 motile organisms), from macroalgae to fish. Shells of juvenile and adult specimens had different species assemblages. Four distinct assemblages were detected on shells, primarily formed by the red alga Gracilaria bursa-postaris, egg cocoons of the invasive alien Rapana venosa, the gastropod Bittium reticulatum and the serpulid polychaete Spirobranchus polytrema.

An Alien Invader is the Cause of Homogenization in the Recipient Ecosystem: A Simulation-Like Approach

Biotic homogenization is an expected effect of biological invasions. Invasive alien species typically show great adaptability to a wide range of environmental conditions and may expand into different habitats, thus reducing the dissimilarity among the recipient communities. We tested this assumption by analyzing a comprehensive database (78 species × 229 samples) collected between 2012 and 2017 in the marine protected area of Portofino (NW Italy), where Caulerpa cylindracea, one of the worst invaders in the Mediterranean Sea, exhibits high substratum cover at depths between 1 m and 45 m in 14 different communities (identified according to the European Nature Information System EUNIS for habitat classification). Five samples for each of the eight depth zones (i.e., 5 m, 10 m, 15 m, 20 m, 25 m, 30 m, 35 m, and 40 m) were randomly re-sampled from the comprehensive database to produce a dataset of 67 species × 40 samples. Then, a second dataset of 66 species × 40 samples was simulated by excluding Caulerpa cylindracea. Both re-sampled datasets underwent multivariate analysis. In the presence of C. cylindracea, the overall similarity among samples was higher, thus indicating homogenization of the rocky reef communities of Portofino Marine Protected Area. Continued monitoring activity is needed to understand and assess the pattern and extent of C. cylindracea’s inclusion in the recipient ecosystems.

The Persian War as Civil War in Plataea’s Temple of Athena Areia

SummaryDifferences in the Persian-War tradition have often been noted, but there remains a general assumption that those differences were limited to self-interested quibbling within a commonly accepted narrative of the war. In this paper I argue that divergences in the Persian-War tradition went much deeper. In the decades immediately after the war’s end, the various city-states were producing commemorations of the Persian War that in some instances could hardly be said to recall the same event. I focus on a single case in point: the commemorative narrative publicized by the Plataeans in their temple to Athena Areia. Whereas the Athenians (and others) represented the war as a glorious struggle against an alien invader, the Plataeans, despite their close alliance with Athens, chose to cast it as a disturbing civil war between Greeks. These conflicting stories about the Persian War emerged because of substantial differences in all three of the factors that tend to influence memory production: the real experiences of a given past event, the preexisting social memories onto which those experiences must be grafted, and of course the evolving present needs in whose service the past is always recalled and occasionally reshaped. Most Greek states had much less in common than Athens and Plataea, and similarly deep fissures can be seen elsewhere. Ultimately, this study suggests that the Persian-War tradition was, from the beginning, far more fractured and chaotic than is currently assumed.

Modelação espacial da adequabilidade de habitat a espécies invasoras: o Carpobrotus Edulis em terreno não dunar

The use of habitat modelling for exotic invasive species can be extremely useful for identifying their potential impacts and for assisting in the design of eradication strategies. Even though the latter builds on theoretical assumptions that are quite different from those involved in the modelling of the habitat of native species, these two modelling methods are in fact quite similar. This article presents a habitat suitability modelling framework for Carpobrotus edulis, an alien invader plant in Serra do Bouro, Portugal. Several land surveys have been carried out in the study area in order to record the presence of this plant. The criteria for recording a presence were that the plant did not show any signs of weakness and that there were mat formations covering at least 5m2. Pseudo-absences were also obtained in a completely random way. The model was calibrated using a binary logistic regression. The performance of this model usually considered superior to that of models that rely on presence data only. Additionally, an evaluation technique based on the minimum area of higher adequacy is also presented. This technique assumes that, for a given probability threshold, model performance is higher whenever it has the same number of correct presences for a smaller predicted area. Using a 0.7 probability threshold, the model correctly predicted 80% of the total presences using only 8% of the study area. The model suggests that the main factor contributing to the expansion of Carpobrotus edulis has been the abandonment of agriculture in the study area. In addition, proximity to the shoreline and above-average erosion potential in the study area both seem to benefit the plant’s expansion. Conversely, steeper and longer slopes, and greater distances from the shoreline, were found to be significant contributors to the plant’s absence.

Specific Niche Characteristics Facilitate the Invasion of an Alien Fish Invader in Boreal Streams

We studied the ecological niche relations of native stream fish and an alien invader, brook trout (Salvelinus fontinalis), to examine if brook trout had located an underused environmental niche in our boreal study system. In both study years (1994 versus 2004), we found brook trout to have the most marginal niche position of all the fish species examined. The most important environmental variable affecting the distribution of brook trout was pH, with acid headwater sites being dominated by this species. Brown trout, in contrast, had relatively nonmarginal niche, occurring in average conditions across the sampled sites. Other fish species had niche positions between the two salmonids. Our results show that fish invasions may be strongly facilitated by the presence of suboptimally occupied environmental niche space in the recipient river system.

The current status of freshwater molluscs in the Kruger National Park

Surveys regarding the freshwater mollusc population of the Kruger National Park commenced before 1966 and was repeated in 1995, 2001 and recently in 2006. During this period the park was exposed to several droughts as well as floods, all of which could have had some influence on the various habitats in the park. Industrial developments and urbanisation near some of the major rivers outside the park, but which flow through the park, could also have a detrimental effect on the species diversity of the freshwater molluscs. The recent survey in 45 habitats included several dams and rivers. The survey was done to determine the current status of the mollusc species diversity. By comparing it with previous surveys, an attempt was made to establish the overall health of freshwater mollusc habitats. From the results it is clear that there was a drastic decrease in the mollusc species diversity in five of the habitats. Although there was a slight change in the species composition in some of the major rivers there was no difference in the number of species collected in these habitats. Tarebia granifera, an alien invader mollusc, was found in several rivers and dams. Gyraulus costulatus, Melanoides victoriae and Eupera ferruginea, which could not be found during the survey of 2001, were collected during the current survey.