The effect of ultraviolet-depleted light on the flavonol contents of the cactus species Opuntia wilcoxii and Opuntia violacea

An early investigation at the Biosphere-2 Laboratory, an artificial ecosystem in the Arizona desert, had shown that the flavonoid content of cacti grown in glass-filtered solar light was lower than of cacti grown in normal solar light. This was attributed to the absence of ultraviolet (UV) radiation, which is required for flavonoid biosynthesis. In this study, two species of Opuntia cacti were grown in solar and UV-depleted light, and their flavonol contents of different tissues were determined by HPLC. O. wilcoxii, previously raised in the absence of UV light, was exposed to normal solar light. The flavonol content of young O. wilcoxii pads was 28-fold higher when grown in solar light as compared to UV-depleted light. The flavonol contents of mature outer tissues were only slightly higher. O. violacea, previously raised in solar light, was also maintained in the same UV-depleted artificial ecosystem. The flavonol content after hydrolysis of outer tissues was similar, whether grown in solar light or UV-depleted light. We attribute these responses to different biosynthetic and metabolic rates of young vs. mature plant tissues; slow-growing mature tissues neither produce nor metabolize compounds as quickly as immature tissues. These findings indicate that artificial ecosystems can influence the production of natural products in cultivated plants.     

Restoration of Dry Afromontane Forest Using Pioneer Shrubs as Nurse-Plants for Olea europaea ssp. cuspidata

Shrubs are often considered competitive barriers for seedlings planted in reforestation programs, although they can facilitate tree recruitment, especially in ecosystems under high abiotic stress. An alternative reforestation technique using pioneer shrubs as nurse‐plants for Olea europaea ssp. cuspidata was tested in exclosures in northern Ethiopia. Seedlings were planted in three different microhabitats, and their survival was monitored. The microhabitats were bare soil patches between shrubs, patches under the dominant shrub Acacia etbaica, and patches under Euclea racemosa, an evergreen shrub, which supports the majority of naturally established Olea recruits. The ability of shrubs to offer protection against browsing goats was tested experimentally. Controlled shading was used to determine whether solar irradiation causes seedling mortality in environments without water stress. Data were analyzed using Kaplan–Meier survival analysis, Kruskal–Wallis analysis of variance (ANOVA), and one‐way ANOVA. Olea survival was significantly higher and shoot damage by goats was lower when planted under shrub cover compared to bare soil patches, particularly under Euclea canopies, although high shade levels reduced seedling performance. Reduction of solar radiation by shrub canopies and thus control of soil–water evaporation and seedling transpiration most likely controlled the observed facilitation. Planting under shrubs may increase seedling survival and assist regeneration of dry Afromontane vegetation. Preserving pioneers also reduces soil erosion and conserves biodiversity. Excluding livestock is essential for Olea woodland restoration and allows persistent but morphologically modified Olea shrubs to develop vigorous regrowth. Facilitative processes are guiding principles for assisted forest restoration, but above‐average rains may be critical to restore higher biomass levels in semiarid areas.     

Programming microbial population dynamics by engineered cell-cell communication

A major aim of synthetic biology is to program novel cellular behavior using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behavior at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications.     

Comparative thermal adaptation in cicadas (Hemiptera: Cicadidae) inhabiting Mediterranean ecosystems

The thermal responses of cicadas inhabiting the Mediterranean ecosystems in Europe, North America, South Africa, and Australia are investigated. A total of 37 species and two subspecies from 17 genera representing eight tribes and three subfamilies of cicadas are investigated. The analysis includes species that are restricted to the Mediterranean ecosystem as well as those which also inhabit additional environments. The data suggest that cicadas adapt to the climate type regardless of particular types of plants within the various Mediterranean communities. Similarly, cicada thermal responses are independent of body size or taxonomic affinities. There is a wider range of body temperatures for the maximum voluntary tolerance temperature than for heat torpor or minimum flight temperatures. This diversity seems to be determined by the subdivision of the habitat used and the behavior of the species. All species possess relatively elevated heat torpor temperatures adapting to the general thermal characteristics of the Mediterranean ecosystem. The data suggest that cicadas adapt to the Mediterranean climate type regardless of the diversity of particular types of plants within the various communities, of body size or of taxonomic position.     

Ancient introductions of mammals in the Mediterranean Basin and their implications for conservation

• 1 The importance of taxonomy to the determination of conservation priorities and actions is widely accepted. It should be not surprising therefore that the taxonomic treatment of mammal species that have been subject to human actions in antiquity may well influence the contemporary assessment of conservation priorities at various levels.
• 2 As a result of early extinctions caused by humans and protohistoric and historic introductions, we suggest that the Mediterranean Basin and its islands are particularly prone to misdirection of efforts towards biodiversity conservation.
• 3 The two main risks associated with the failure to use an evolutionary and palaeoecological approach to conservation efforts are (i) an underestimation of the conservation importance of distinctive continental taxa vs. the apparent endemicity of island taxa; and (ii) a serious risk for native and endemic island species when anthropochorous mammals, especially ungulates, misguidedly become the focus of conservation actions, particularly inside protected areas.
• 4 Urgent measures, including refinement of mammal taxonomy, the exclusion of known anthropochorous taxa from conservation lists and implementation of protective legislation, are necessary to maintain the uniqueness and richness of the Mediterranean biodiversity hotspot.

     

Seed predation and dispersal in relict Scots pine forests in southern Spain

For two years, the seed rain and magnitude of seed losses due to predation were evaluated in Scots pine forests in southern Spain. The Crossbill was the most important pre-dispersal predator, consuming more than 80% of ripening seeds. In addition, other birds, mainly Tits and Siskin, also consumed seeds just before seed dispersal, reaching values of 16 and 51% losses in 1996 and 1997, respectively. Seed rain was monitored in different microhabitats (under pine canopies, under shrubs and in open areas), and was most intense under the canopy of mother plants both years. Post-dispersal seed predators (rodents and birds) consumed up to 96% of seeds reaching the ground. Both pre- and post-dispersal seed predators preferentially harvested filled seeds. Post-dispersal predation was similarly intense in all microhabitats, so predators did not change the spatial distribution of the seed rain. These high predation rates were constant between years, localities and habitats (woodland and treeline). We hypothesize that this high rate of seed predation is a major factor limiting the regeneration of these relict populations of Scots pine in its southernmost limit.     

Boat anchoring on Posidonia oceanica beds in a marine protected area (Italy, western Mediterranean): effect of anchor types in different anchoring stages

Seagrasses worldwide are noted for suffering from mechanical damage caused by boat anchoring. This is particularly so in sites highly frequented by boaters (marine protected areas or coastal urbanised areas). In the last decades, different strategies have been put into practice to reduce such impacts on seagrasses (i.e. by anchoring bans or by deploying boat moorings). More recently, in consideration that few marine protected area (MPA) management bodies or local administrations have the resources to enforce their anchorage regulations, the self-regulatory approach based on education and information of boaters has been preferred in several cases. At present, however, very little is known on the correct anchoring practices to ensure the safeguarding of seagrasses. The aim of the present study was to experimentally quantify in the field the damage caused to Posidonia oceanica shoot density by anchoring. A multifactorial experiment was designed to test whether the damage is dependent on (1) different anchor types (Hall, Danforth and Folding grapnel), (2) the use of a chain vs. a rope, (3) the three anchoring stages (anchor fall, dragging/lock-in and weighing), and finally (4) whether the pattern is consistent among different locations of the meadow.As expected, the three anchor types employed in the present study differed in the levels of damage inflicted on the P. oceanica meadows of the Ustica Island MPA. In particular, the use of the Hall type anchor seems to be preferable to minimise this impact in comparison with the other two anchor types. Moreover, the effect on the meadow of the three anchor types is greatly dependent on the anchoring stage. These results confirm that the weighing stage is the critical stage of the anchoring process. The number of damaged shoots of P. oceanica was not affected by the presence of the chain. These patterns were consistent between locations.In the long term, even anchoring on P. oceanica by small boats using low-impact anchors may potentially have detrimental consequences. For this reason, we suggest that in vulnerable sites, it is preferable to implement an educational program based on information of boaters on correct anchoring practices and anchor typology to use, rather than adopting strong restrictions to boat anchoring or deploying mooring buoys. Although the use of these management strategies is still recommended in the case of anchorage frequented by bigger vessels using heavier anchors and chains.     

Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes?

1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long‐term limnological data set to document changes in the food‐web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L^?1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents from ricefields. 3. Chlorophyll a concentration was reduced by half (annual mean of 180 μg L^?1). Cyanobacteria abundance remained high but its composition changed towards smaller species, both filamentous and chroococcal forms. 4. Cladocera abundance increased and reached peaks twice a year (December to March and July to September). After nutrient reduction, short‐term clear‐water phases (up to 5 weeks) occurred during February to March in several years, concomitant with annual flushing of the lake and lower fish densities. The abundance of Cladocera in winter contrasted with the spring peaks observed in northern restored shallow lakes. The zooplankton to phytoplankton biomass ratio remained lower than in northern temperate shallow lakes, probably because of fish predation on zooplankton. 5. Improvement of the water quality of Lake Albufera remained insufficient to counteract littoral reed regression or improve underwater light allowing submerged plants re‐colonise the lake. 6. Sewage diversion from Lake Albufera impacted the food web through the plankton, but higher trophic levels, such as fish and waterfowl, were affected to a lesser degree. Although the fish species present in the lake are mainly omnivorous, long‐term data on commercial fish captures indicated that fish communities changed in response to nutrient level and trophic structure as has been observed in restored shallow lakes at northern latitudes. 7. Phosphorus concentrations produced similar phytoplankton biomass in Lake Albufera as in more northern shallow lakes with abundant planktivorous fish and small zooplankton. However, in Lake Albufera, high average concentrations were maintained throughout the year. Overall, results suggest that nutrient control may be a greater priority in eutrophicated warm shallow lakes than in similar lakes at higher latitudes.     

Potential allelopathic effect of neo-clerodane diterpenes from Teucrium chamaedrys (L.) on stenomediterranean and weed cosmopolitan species

The allelopathic effects of neo-clerodane diterpenes, isolated from Teucrium chamaedrys (L.), have been evaluated on the seed germination and seedling growth of four coexisting Mediterranean species (Dactylis hispanica, Petrorhagia velutina, Phleum subulatum and Petrorhagia saxifraga) and two cosmopolitan weeds (Amaranthus retroflexus and Avena fatua). All of the structures have been elucidated on the basis of their spectroscopic features. The bioassays data, analyzed by principal component analysis, showed more negative effects on weeds respect to coexisting species. Moreover D. hispanica, P. velutina, P. subulatum showed both stimulating or inhibiting effects depending on the type of metabolite and the concentration used in the test.     

The tropical history and future of the Mediterranean biota and the West African enigma

Aim Since the opening of the Suez Canal in 1869, many tropical taxa from the Indo‐West Pacific (IWP) realm have entered the Mediterranean Sea, which is experiencing rising temperatures. My aims are: (1) to compare biogeographically this tropical transformation of the Mediterranean biota with the tropical faunas of the Mediterranean and adjacent southern European and West African seas during the Late Oligocene to Pliocene interval; (2) to infer the relative contributions of the tropical eastern Atlantic and IWP to the tropical component of the marine biota in southern Europe; and (3) to understand why West Africa is not now a major source of warm‐water species. Location Southern Europe, including the Mediterranean Sea, and the coast of tropical West Africa. Methods I surveyed the literature on fossil and living shell‐bearing molluscs to infer the sources and fates of tropical subgenus‐level taxa living in southern Europe and West Africa during the Late Oligocene to Pliocene interval. Results Ninety‐four taxa disappeared from the tropical eastern Atlantic (including the Mediterranean) but persisted elsewhere in the tropics, mainly in the IWP (81 taxa, 86%) and to a lesser extent in tropical America (36 taxa, 38%). Nine taxa inferred to have arrived in the tropical eastern Atlantic from the west after the Pliocene did not enter the Mediterranean. The modern West African fauna is today isolated from that of other parts of the marine tropics. Main conclusions Taxa now entering the Mediterranean through the Suez Canal are re‐establishing a link with the IWP that last existed 16 million years ago. This IWP element, which evolved under oligotrophic conditions and under a regime of intense anti‐predatory selection, will continue to expand in the increasingly warm and increasingly oligotrophic Mediterranean. The IWP source fauna contrasts with the tropical West African biota, which evolved under productive conditions and in a regime of less anti‐predatory specialization. Until now, the post‐Pliocene West African source area has been isolated from the Mediterranean by cold upwelling. If further warming should reduce this barrier, as occurred during the productive and warm Early Pliocene, the Mediterranean could become a meeting place for two tropical faunas of contrasting source conditions.