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Pedro Manuel Anastácio Emília Pereira Leite Margarida Ferreira Luís Vicente Alexandra Marçal Correia 《Limnologica》2011,41(3):228-234
The red swamp crayfish, Procambarus clarkii, and the eastern mosquitofish, Gambusia holbrooki have been introduced worldwide, but the interactions between these invasive species are not well known. The effects of crayfish presence, crayfish size and water depth on the consumption of G. holbrooki by P. clarkii were analyzed, as were the effects of mosquitofish presence and water depth on the consumption of recently hatched crayfish (RHC) by mosquitofish. To better understand this subject we conducted aquaria and open air mesocosm experiments simulating a rice field section. Aquarium experiments showed that P. clarkii consumes G. holbrooki and that G. holbrooki consumes RHC. Adult crayfish size did not significantly affect the consumption of mosquitofish and water depth had no effect on the consumption of G. holbrooki by P. clarkii and vice versa. In the outdoor mesocosm experiments P. clarkii caused no statistically significant effect on G. holbrooki numbers or biomass when compared with controls without crayfish. In spite of this, the analysis of crayfish stomach contents clearly demonstrated that several G. holbrooki individuals were consumed, indicating that crayfish can profit from the presence of G. holbrooki. Results from our study suggest that in shallow pools there are strong interactions between the two invasive species since adult crayfish predate mosquitofish and mosquitofish predate recently hatched crayfish. Therefore, there are bidirectional trophic interactions between these invasive species which change depending on their relative size. We believe that these interactions should become more relevant in confined areas such as small shallow pools formed during the late summer and autumn. 相似文献
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Semi-arid ecosystems are privileged sites to address the effects of plant interactions on community structure and dynamics because environmental conditions are demanding and may change quickly, altering in significant ways the balance between positive and negative effects among neighboring plants. Plant interaction processes have been well documented in the semi-arid region of Southeast Spain over the last 15 years. In this article we review the growing body of research on plant–plant interactions available from this area, highlighting its importance in increasing our knowledge on this field of study. This review has been organized in five sections, i) facilitation mechanisms; ii) the nurse effect; iii) the balance of interactions and environmental, ontogenic, temporal, and spatial gradients; iv) the effects of facilitation on biodiversity; and, v) facilitation and ecosystem functioning. Mechanisms of facilitation in these systems are relatively well known, but not completely explored. In these environments competition, mainly for water, is intense between neighbors and switches in intensity from belowground to aboveground as productivity increases. By contrast, facilitation may decrease quickly with increasing productivity, although the balance between facilitation and competition is not fully understood, and is further complicated because shifts can also be driven by factors such as life history or physiology of interacting species. Positive interactions are critical for maintaining biodiversity in some ecosystems in SE Spain, but their role as a driver of ecosystem functioning is less clear. Research on plant–plant interactions in this region has been highly influential and has contributed to our overall understanding of plant community dynamics. Despite the important progress achieved during the last 15 years, there is still substantial scope for exploring the effects of plant interactions at the ecosystem level, and their role as modulators of disturbances such as the current global environmental change. 相似文献
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Non-indigenous species (NIS) are a growing problem globally and, in the sea, aquaculture activities are critical vectors for their introduction. Aquaculture introduces NIS, intentionally or unintentionally, and can provide substratum for the establishment of other NIS. Little is known about the co-occurrence of NIS over long periods and we document the coexistence over decades of a farmed NIS (a mussel) with an accidently introduced species (an ascidian). Both are widespread and cause serious fouling problems worldwide. We found partial habitat segregation across depth and the position of rafts within the studied farm, which suggests competitive exclusion of the mussel in dark, sheltered areas and physiological exclusion of the ascidian elsewhere. Both species exhibit massive self-recruitment, with negative effects on the industry, but critically the introduction of NIS through aquaculture facilities also has strong detrimental effects on the natural environment. 相似文献
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Wei Cheng Geng Sun Lin-fang Du Yan Wu Qun-ying Zheng Hong-xuan Zhang Lin Liu Ning Wu 《山地科学学报》2014,11(3):746-754
Steller chamaejasme L. (S. chamaejasme for short) is one of the most noxious unpalatable weeds in China, which has been frequently reported its negative interaction (i.e. competition and allelopathy) with other herbaceous species in grasslands. This study compared species diversity, biomass and sexual reproduction of herbaceous plants in meadows with S. chamaejasme and in open meadows without S. chamaejasme in overgrazing meadows on the Tibetan Plateau in China to determine whether positive facilitation exist between S. chamaejasme and other herbaceous species under livestock’s overgrazing. The results showed that there are more herbaceous species in meadows with S. chamaejasme than those in open meadows (35s and 30s, respectively). Diversity index and above-ground biomass were also significantly higher in meadows with S. chamaejasme. There were 39% (11/28) of all species with sexual reproduction found in meadows with S. chamaejasme, which was 7 times more than those in open meadows. Our study showed that S. chamaejasme could provide biotic refuge for neighboring plants and preserve plant diversity from livestock’s overgrazing in alpine meadows on the Tibetan Plateau. It also suggested that inter-specific facilitation between S. chamaejasme and other herbaceous species may play a key role in overgrazing alpine meadows. 相似文献
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Seedling recruitment in a semi-arid steppe: The role of microsite and post-dispersal seed predation 总被引：2，自引：0，他引：2
Grasslands dominated by Stipa tenacissima are important ecosystems in the arid and semiarid climates of western Mediterranean, where they have originated by degradation of open dry forests and shrublands. At present, although the level of exploitation in these ecosystems is very low, succession processes seem to have stopped. In this study, we explore the role of microsite and post-dispersal seed predation on the seedling emergence of two species from advanced successional stages (Rhamnus lycioides, Quercus coccifera), three species from degraded stages (Cistus clusii, Helianthemum violaceum, Anthyllis terniflora), and of the dominant species (Stipa tenacissima). Seeds of these species were sown in plots divided into two microsites: (i) under tussocks of S. tenacissima and (ii) in the bare soil between tussocks. Soil moisture was significantly higher in the tussock microsites. The interaction observed between microsite and time, reflected the slower drying process under tussocks. Seed predation was in general high and differed significantly between species but not between microsites. Q. coccifera was especially affected by predation. The only germination detected in gap areas was that of H. violaceum. The results pointed to a direct facilitative effect of tussock grass on the germination in R. lycioides (20.4±8.0%) and S. tenacissima (41.3±5.7%) while the corresponding figures for bare ground were 0%. These results suggest that the recovery of potential vegetation in this ecosystem is not possible or, at least, is very slow because the residual shrub patches do not generate a sufficient number of seeds able to disperse to favorable germination microsites. S. tenacissima may act as facilitator of seedling recruitment if there is a supply of diaspores. 相似文献
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J. Cortina B. Amat V. Castillo D. Fuentes F.T. Maestre F.M. Padilla L. Rojo 《Journal of Arid Environments》2011,75(12):1377-1384
Semi-arid landscapes in the western Mediterranean have been used for millennia, resulting in large-scale transformations and widespread degradation. In some instances, these degraded environments have been unable to recover spontaneously, and ambitious restoration programs have been launched over the last decades to improve landscape conditions. Ecological restoration may speed up succession, promote more complex communities and increase their functionality. But uncertainty in the definition of restoration objectives, failure to identify most efficient practices and, particularly, socio-economic and cultural constrains may compromise future actions. Here, we review recent advances in the restoration of semi-arid vegetation cover in the Iberian southeast, discuss future challenges and suggest two key steps towards increasing the consistency and efficiency of restoration programs: emphasis on ecosystem services, and implementation of participative and adaptive management practices. 相似文献
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