The germination response of 20 species from high altitude Mediterranean climates, most of them rare endemics, was studied. Our main goal was to model the germination response of a complete set of Iberian high mountain species. The effect of temperature and other parameters, such as spatial and temporal short gradients, on germination were also evaluated. Some seed features (mass and size) were also related to the germination response. Finally, we tested the effect of cold-wet stratification pretreatment when germination was low under natural conditions. Seeds were collected at four locations from 1,900 to 2,400 m a.s.l. in the Sierra de Guadarrama (Spanish Central Range) over two consecutive growing seasons (2001)(2002) and submitted to different temperatures and a constant photoperiod of 16 h light/8 h darkness. Most plants readily germinate without treatment, reaching an optimum at relatively high temperatures in contrast to lowland Mediterranean species. Seeds seem to be physiologically prepared for rapid germination even though these plants usually face very intense summer droughts after ripening and dispersal. Germination was also highly variable among altitudes, populations and years, but results were inconsistent among species. Such flexibility could be interpreted as an efficient survival strategy for species growing under unpredictable environments, such as the Mediterranean climate. Finally cold-wet stratification increased germination capacity in five of nine dormant species, as widely reported for many arctic, boreal and alpine species. In conclusion, high mountain Mediterranean species do not differ from alpine species except that a relatively high number of species are ready to germinate without any treatment.

Pioneer plants are adapted to grow in unpredictable environments. These plants have evolved several traits related to seed morphology and germination to cope with this unpredictability. The main aim of this study was to investigate the effect of plant identity and maternal environment on seed mass and germination of Sinapis arvensis. This study was undertaken with S. arvensis plants grown in four experimentally manipulated resource availability scenarios: (i) nitrogen addition, (ii) water addition, (iii) nitrogen and water simultaneously added, and (iv) control. Plants grew under field conditions in an emerging plant community. Germination response was mainly affected by maternal plant identity. This reflects not only genotype quality but also phenotypic plasticity, which allows adaptation to habitat conditions. Seed coat colour together with mean seed mass per plant explained significant fractions of the variability in germination rate. Changes in the germination response because of maternal environmental effects were also detected. Germination rate decreased in seeds from nitrogen-enriched conditions; this may be due to the induction of dormancy caused by high concentration of nitrogen in the seeds. Addition of water to maternal environment caused a decrease in total germination percentage and germination rate of seeds. Thus, our results provide evidence for maternal environmental effects on germination under field conditions. Furthermore, changes in germination timing, as detected in our study, may determine plant development and fitness in unpredictable conditions.

No abstract

No abstract

No abstract

Final germination percentages of 25 accessions of Brassicaceae from the UPM (Universidad Politécnica de Madrid) seed bank were evaluated after 38-40 years of storage. The seeds were preserved at temperatures between-5°C and-10°C in flame sealed vials containing dehydrated (blue) silica gel. Seed moisture content ranged between 0.3 and 3% (f.w.b) after storage. Most accessions (ten out of twelve) with high initial (before storage) germination rate (low initial dormancy) maintained these high values almost intact after storage (91-100% germination). In two accessions, seeds had developed a secondary dormancy, which was successfully overcome by scarification. A second set of 13 accessions had low initial germination rates (0-20%, i.e. high initial dormancy). In one accession, dormancy had been broken during storage (92% germination) and in nine accessions germination was significantly enhanced by GA 3 and or scarification. Seed dormancy most often decreases during storage but it may also increase or remain unchanged. The consideration of these dormancy variations is very important when evaluating seed longevity in wild species. The preservation method based on silica gel and low temperature (-5°C and-10°C) has proved highly efficient at least for Brassicaceae. Vials with seeds of 12 additional accesssions had remained at room temperature during 34-39 years and those seeds showed germination percentages that were similar to those preserved in the cold room. This result suggests that temperature might not be as important as expected-at least for medium-term preservation-and supports the possibility of using ultra-dry methods.

The Mediterranean area is regarded nowadays as one of the hot-spots of world biodiversity. The Baetic ranges in Spain have such a large number of endemic plant taxa that the territory has been recognized as a well-defined biogeographical unit. These endemic taxa tend to concentrate on disjunct highland areas that have been described consequently as 'highland islands'. Despite the importance and complexity of these sites, the research carried out so far has produced only descriptive classifications. These approaches overlook the relationships between the sites and do not serve to identify the main centres of endemism. Herein, multivariate analysis techniques (cluster analysis and reciprocal averaging) and the parsimony analysis of endemicity (PAE), applied to the 222 orophilous endemic taxa of the Baetic ranges, have been used to reveal the floristic similarities between the areas involved, to identify the centres of endemism and to re-assess the previous classifications. Four centres of endemism are defined, one siliceous and three calcareous. The most outstanding feature in the Baetic ranges is precisely the floristic difference between siliceous and calcareous mountains. Calcareous territories extend along a SW-NE axis in line with the oceanic-continental gradient. The nature of the soil in the vast siliceous and calcareous-dolomitic territories of the Sierra Nevada is probably the cause of the remarkable floristic diversity. Not surprisingly, in our analysis these areas stand out as centres of endemism. We conclude that previous biogeographical classifications of the ranges are too rigid and do not properly reflect the floristic similarities of the area under study.

-Spanish pine forests exhibit a high degree of resilience to frequent wildfires. For this reason