Invasion dynamics

"Dynamics of the introduced tree Litsea glutinosa (Lauraceae) in Mayotte Island : Is it an invasive species? — Litsea glutinosa (Lour.) C.B. Rob, the Indian laurel, is a dioecious tree from Australasia which has been introduced on Mayotte and has proliferated during the era of sugar cane plantations (1841-1880). Efficiently dispersed by the Brown Lemur (Eulemur fulvus) and by numerous birds, this Lauraceae species now spreads into the humid area and it is present in the last remaining « natural » fragmented forests of the island. This tree, ranging from 10 to 15 meters in height, is mostly found on the wetter (rainfall > 1 500 mm/year) northern part of the island. This study analyses the population dynamics of Listea glutinosa between 1996 and 2002 in the remains of the mesophilous and ombrophilous forests, as well as the importance of vegetative reproduction in certain populations. L. glutinosa proliferates in protected forests, particularly in semi-dry forests where it can take advantage of the more open forest structure. Because of its light-demanding temperament, L. glutinosa needs an opening in the forest canopy to settle down and grow. The tree’s invading nature, however, is due partially to its capability to reproduce vegetatively; over half of the stems are produced by vegetative reproduction, mostly root-suckering. This species could lead to a specific loss of biodiversity in « natural » areas, but is not considered as a pest by local inhabitants, because of its frequent utilization, especially as fodder."

Herbarium accession data offer a useful historical botanical perspective and have been used to track the spread of plant invasions through time and space. Nevertheless, few studies have utilised this resource for genetic analysis to reconstruct a more complete picture of historical invasion dynamics, including the occurrence of separate introduction events. In this study, we combined nuclear and chloroplast microsatellite analyses of contemporary and historical collections of Senecio madagascariensis, a globally invasive weed first introduced to Australia c. 1918 from its native South Africa. Analysis of nuclear microsatellites, together with temporal spread data and simulations of herbarium voucher sampling, revealed distinct introductions to south-eastern Australia and mid-eastern Australia. Genetic diversity of the south-eastern invasive population was lower than in the native range, but higher than in the mid-eastern invasion. In the invasive range, despite its low resolution, o...

Change of a cultural phenomenon has intrigued researches from numerous disciplines. In archaeology the explanations for cultural changes are dependent upon a reliable observation of the reflections of such changes in archaeological materials. We understand a culture like an assemblage of artefacts that recurs repeatedly associated in dwellings of the same kind and with burials of the same rite.
Cultural changes can be a result of two different mechanisms: diffusion and migration. In our paper we will deal just with the manifestation of the last mechanism.
Population movement may be defined as the original peopling of an area or, if humans already lived there – like in our case, as the repeopling that takes place when a foreign population enters the area and displace or absorbs its native inhabitants. The invading population must bring with it a new language, culture and impose them on the natives.
Immigration is the intrusion of individual settlers into already populated area. The intruders usually travel as members of a family or some other kind of social group.
There is more than one reason for the peopling or re peopling of an area The migrants may have responded to their own over population or to pressure from neighboring populations. Alternatively or in addition, they may have been attracted by more favorable conditions in their now homeland. And they may also have been affected by changes in the natural and/or human components of either old or their new environments.
In Bronze Age the crafts are specialized and social stratification is developed. When a person become rich, this person will present his success through exotic products consuming. This is applicable for cultures to – like in case of Otomani culture, which has the control of important resources (gold, salt), or has the control of important commercial routes from north to south and east to west Europe. Amber from Baltic region and faience beads from east Mediterranean region is a good proof for that. At Ganovce was discovered the earliest iron dagger in Central Europe. A lot of weapons and jewelry with Mycenaean influence was discovered in area of Otomani culture.
The present evidence supports the hypothesis that during Bronze Age, Europe was connected by a number of inter-locking regional exchanges networks, in which goods moved internally by such mechanisms as gift or redistribution and in the peripheral areas and between networks by barter and trade. This network of interlocking exchanges spheres retained a high degree of coherence and stability during the European Bronze Age. At the beginning of this century this aspects of material culture was interpreted like innovation after an invasion.
A change can be in different ways: from one equivalent of artifact to another, from simple to complex, from a style to another, increase or decrease of variety or technological complexity, changes in quantity. But not all this changes are related just to invasion or immigration. To be able to explain any change in the development it is also necessary to define and express as exactly as possible the nature and size of the change observed.
The data obtaining from anthropological and ethnographic studies are useful for a understanding of pattern changes in prehistory, but our interpretation must be one based mainly on archaeological evidence.