Bud morphology and shoot growth dynamics in two species of Mediterranean sub-shrubs co-existing in gypsum outcrops

BACKGROUND AND AIMS: Understanding the effects of the environment on the morphology and shoot growth activities of plants is crucial to identifying plant ecological strategies. This study analysed the bud morphology, bud activity, shoot growth dynamics and shoot water content at full hydration (WC(h)) of two species of Mediterranean sub-shrubs, Lepidium subulatum and Linum suffruticosum, co-existing in gypsum outcrops in north-east Spain. METHODS: Sampling was conducted monthly over 2 years in one population per species. Buds were dissected under a stereo-microscope. Shoot growth was measured as the mean increase in shoot length of 15 marked individuals between two consecutive samplings. Bud activity was studied following the variations in the number of leaf primordia shorter than 1 mm and longer than 0.025 mm in the buds. KEY RESULTS: Both species bore naked buds and displayed discontinuous seasonal patterns of shoot growth, leaf primordia formation and WC(h). The number of leaf primordia in the bud peaked before the beginning of shoot expansion. In both species, organogenesis and expansion were uncoupled throughout the year. The time lapse between these two processes varied throughout the year, and was greatest for those elements differentiated in autumn. WC(h) was more closely related to shoot expansion than to organogenesis. CONCLUSIONS: Both species displayed similar bud morphology and similar seasonal patterns of bud and shoot growth, and WC(h) as a result of the strong seasonality of the Mediterranean climate in gypsum outcrops. The beginning of the spring period of expansion of long branches coincided with maximum values of WC(h), while the rest period of summer matched minimum values. These results support the hypothesis that the growth of long branches is strongly related to WC(h).     

Diversity of Porifera in the Mediterranean coralligenous accretions,with description of a new species

Temperate reefs, built by multilayers of encrusting algae accumulated during hundreds to thousands of years, represent one of the most important habitats of the Mediterranean Sea. These bioconstructions are known as “coralligenous” and their spatial complexity allows the formation of heterogeneous microhabitats offering opportunities for a large number of small cryptic species hardly ever considered.Although sponges are the dominant animal taxon in the coralligenous rims with both insinuating and perforating species, this group is until now poorly known. Aim of this work is to develop a reference baseline about the taxonomic knowledge of sponges and, considering their high level of phenotypic plasticity, evaluate the importance of coralligenous accretions as a pocket for biodiversity conservation.Collecting samples in four sites along the coast of the Ligurian Sea, we recorded 133 sponge taxa (115 of them identified at species level and 18 at genus level). One species, Eurypon gracilis is new for science; three species, Paratimea oxeata, Clathria (Microciona) haplotoxa and Eurypon denisae are new records for the Italian sponge fauna, eleven species are new findings for the Ligurian Sea. Moreover, seventeen species have not been recorded before from the coralligenous community. The obtained data, together with an extensive review of the existing literature, increase to 273 the number of sponge species associated with the coralligenous concretions and confirm that this habitat is an extraordinary reservoir of biodiversity still largely unexplored, not only taxonomically, but also as to peculiar adaptations and life histories.     

Breeding performance and longevity of Tomicus destruens on Mediterranean and continental pine species

The pine shoot beetle Tomicus destruens (Wollaston) (Coleoptera: Curculionidae: Scolytinae) is one of the main pests of Mediterranean forests, where it is oligophagous on Mediterranean pines. However, possible global warming may make the insect move to higher latitudes and altitudes, allowing it to attack new pine species. In this respect, the aim of the present article was to assess both the acceptance and performance of T. destruens offered host and non‐host pine species. A no‐choice breeding experiment was set up under laboratory conditions, using logs of three Mediterranean (Pinus pinea L., Pinus pinaster Miller, and Pinus halepensis Aiton) and two continental (Pinus nigra Arnold and Pinus sylvestris L.) pine species. Log debarking at the end of adult emergence assessed parent fecundity, egg, and larval mortality. The quality of callow adults emerging from each tested pine was evaluated on the basis of their longevity on a semiartificial diet. Tomicus destruens colonised all tested pine species, but did not reproduce in Scots pine, taking about 79 days to complete development with no differences among pines tested. The best breeding performance, evaluated as female fecundity and adult production, was observed in P. halepensis, and the lowest in P. pinaster. On average, adults emerging from P. pinea survived longer (83 days) than from other pines, and adult longevity was the lowest in males emerging from P. nigra. Austrian pine, which under natural conditions is usually not a host of T. destruens, allowed insect development and adult production similar to P. pinea and P. pinaster.     

Mediterranean Lithophyllum stictiforme (Corallinales,Rhodophyta) is a genetically diverse species complex: implications for species circumscription,biogeography and conservation of coralligenous habitats

Lithophyllum species in the Mediterranean Sea function as algal bioconstructors, contributing to the formation of biogenic habitats such as coralligenous concretions. In such habitats, thalli of Lithophyllum, consisting of crusts or lamellae with entire or lobed margins, have been variously referred to as either one species, L. stictiforme, or two species, L. stictiforme and L. cabiochiae, in the recent literature. We investigated species diversity and phylogenetic relationships in these algae by sequencing three markers (psbA and rbcL genes, cox2,3 spacer), in conjunction with methods for algorithmic delimitation of species (ABGD and GMYC). Mediterranean subtidal Lithophyllum belong to a well‐supported lineage, hereby called the L. stictiforme complex, which also includes two species described from the Atlantic, L. lobatum and L. searlesii. Our results indicate that the L. stictiforme complex consists of at least 13 species. Among the Mediterranean species, some are widely distributed and span most of the western and central Mediterranean, whereas others appear to be restricted to specific localities. These patterns are interpreted as possibly resulting from allopatric speciation events that took place during the Messinian Salinity Crisis and subsequent glacial periods. A partial rbcL sequence from the lectotype of L. stictiforme unambiguously indicates that this name applies to the most common subtidal Lithophyllum in the central Mediterranean. We agree with recent treatments that considered L. cabiochiae and L. stictiforme conspecific. The diversity of Lithophyllum in Mediterranean coralligenous habitats has been substantially underestimated, and future work on these and other Mediterranean corallines should use identifications based on DNA sequences.     

Decomposition and nutrient dynamics in mixed litter of Mediterranean species

In the last decade a great research effort addressed the effects of litter diversity on ecosystem functions, reporting both synergistic and antagonistic effects for decomposition dynamics. Four coexisting Mediterranean species, representing a range of litter quality, were used to arrange litter mixtures at three diversity levels for a litterbag decomposition experiment. Species identity appeared as the major determinant for litter mass loss (Coronilla emerus～Hedera helix>Festuca drymeia>Quercus ilex) and nutrient release, with rates for all leaf litter types following the sequence K>N>Mg≥Ca>>Fe. Additive diversity effects were prevalent pooling together all data but also for nutrients separately. Antagonistic interactions were more common than synergistic in the cases of mass loss, N and Ca contents, but not for K, Mg and Fe dynamics. The number of species in the litterbag significantly affected the outcome of non-additive interactions, which were mostly antagonistic for two-species mixtures, and synergistic for the combined 4 species. Litter quality appears to be the most important factor affecting mass loss and nutrient dynamics, while litter diversity, influencing the rates of these processes, plays an important role in reducing their variability, thus suggesting a greater stability of ecosystems properties in presence of mixed litter.     

Rapid biodiversity assessment and monitoring method for highly diverse benthic communities: a case study of mediterranean coralligenous outcrops

Increasing anthropogenic pressures urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to explore present trends, detect future modifications and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex deep-water habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. Therefore, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We used an extensive photographic survey, covering several spatial scales (100s of m to 100s of km) within the NW Mediterranean and including 2 different coralligenous assemblages: Paramuricea clavata (PCA) and Corallium rubrum assemblage (CRA). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm(2) for PCA and 2500 cm(2) for CRA). In addition, we conclude that 3 replicates provide an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We contend that the proposed sampling approach provides a valuable tool for management and conservation planning, monitoring and research programs focused on coralligenous outcrops, potentially also applicable in other benthic ecosystems.     

The fish assemblage on a coralligenous shallow shelf off the Mediterranean coast of northern Israel

The fish assemblage on the shallow coralligenous shelf (16-30m depth) off Haifa, Israel was sampled using trammel nets throughout a period of 1 year. Complementary data were obtained via underwater censuses of fish on an artificial reef established later in the sampling area. Fortythree species of fish were sampled by trammel nets, 79% of which were observed also during the underwater censuses. Although fish of Red Sea origin constituted only 11.6% of the species composition in the net samples, they contributed 46.2% of the fish abundance and 40.6% of the biomass in these samples. This was supported by the finding that species of Red Sea origin contributed 64% of the abundance of large fish counted on the artificial reef. Siganus luridas, S. rivulatus and Sargocentron rubrum are the main contributors in number and biomass among fish of Red Sea origin. It is suggested that the biogenic rocky bottom of this area contains several components which are similar to biogenic habitats favoured by these benthic species in the Red Sea; this may explain the high abundance of these species in the studied area.     

Spatial and temporal variations of assemblages in a Mediterranean coralligenous reef and relationships with surface orientation

The structure, distribution, and temporal changes of epibenthic assemblages of a Mediterranean coralligenous reef were investigated using a multifactorial sampling design. The distribution of taxa on vertical walls and down-facing surfaces of overhangs and crevices was analysed at ten sites along 2 km of rocky reefs, south of Livorno (Ligurian Sea, Italy). The temporal variations were analysed between two periods (1995–1996 and 1997–1998) and among four sampling times within each period. Most of the space was dominated by prostrate seaweeds (including Peyssonnelia rubra, P. rosa-marina, and Mesophyllum lichenoides), turf-forming seaweeds, and the red coral Corallium rubrum. The cover of a variety of other invertebrates, mainly sponges and bryozoans, was less than 2%. All taxa were found on both vertical and down-facing surfaces. However, seaweeds dominated the vertical surfaces (mean cover >97%), while C. rubrum and other invertebrates dominated down-facing surfaces (mean density of C. rubrum >16 colonies dm⁻²). Although there was some fluctuation in the abundance of taxa, no obvious patterns were observed. These results support the model of limited temporal variability in Mediterranean coralligenous reefs, possibly related to the slow growth rates of the most abundant taxa and the reduced seasonality of physical conditions.     

Mammalian metabolism, longevity and parasite species richness

Basal metabolic rate (BMR) scales allometrically with body mass in mammals, but the reasons why some species have higher or lower metabolic rates than predicted from their body mass remain unclear. We tested the idea that parasite species richness may be a contributory factor by performing a comparative analysis on 23 species of mammals for which data were available on parasite species richness, BMR, body mass and two potentially confounding variables, i.e. host density and host longevity. Parasite species richness was positively correlated with BMR and negatively correlated with host longevity independent of body mass.     

Dendritic network structure and dispersal affect temporal dynamics of diversity and species persistence

Landscape connectivity structure, specifically the dendritic network structure of rivers, is expected to influence community diversity dynamics by altering dispersal patterns, and subsequently the unfolding of species interactions. However, previous comparative and experimental work on dendritic metacommunities has studied diversity mostly from an equilibrium perspective. Here we investigated the effect of dendritic versus linear network structure on local (α‐diversity), among (β‐diversity) and total (γ‐diversity) temporal species community diversity dynamics. Using a combination of microcosm experiments, which allowed for active dispersal of 14 protists and a rotifer species, and numerical analyses, we demonstrate the general importance of spatial network configuration and basic life history tradeoffs as driving factors of different diversity patterns in linear and dendritic systems. We experimentally found that community diversity patterns were shaped by the interaction of dispersal within the networks and local species interactions. Specifically, α‐diversity remained higher in dendritic networks over time, especially at highly connected sites. β‐diversity was initially greater in linear networks, due to increased dispersal limitation, but became more similar to β‐diversity in dendritic networks over time. Comparing the experimental results with a neutral metacommunity model we found that dispersal and network connectivity alone may, to a large extent, explain α‐ and β‐diversity dynamics. However, additional mechanisms, such as variation in carrying capacity and competition–colonization tradeoffs, were needed in the model to capture the detailed temporal diversity dynamics of the experiments, such as a general decline in γ‐diversity and long‐term dynamics in α‐diversity.     

Seed germination of high mountain Mediterranean species: altitudinal,interpopulation and interannual variability

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.     

Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity

Background and Aims

Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.

Methods

The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM, optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh.

Key Results and Conclusions

The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 µm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region – all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.     

Patterns of plant species composition on Amazonian sandstone outcrops in Colombia

Vascular plant species compositional patterns of the low forest, scrub, and herbaceous vegetation on white sand soils and sandstone substrates were studied at six sandstone plateaus in Colombian Amazonia, by means of a field survey according to the Braun‐Blanquet relevé method. Canonical Correspondence Analysis (CCA) was applied to separate effects of habitat and spatial configurations of the plateaus on species patterns. Also, information on dispersal ability and phytogeographic affinity of species was used to test explanations for between plateau differences. Low trees, shrubs and herbs were the main species recorded in 212 relevés. The main gradients in the species patterns were linked to the spatial configuration of the plateaus. Spatially controlled species patterns were mainly related to soil depth and soil organic matter. The association between phytogeographic affinity and the habitat controlled spatial link of species pointed at insufficient sampling at one plateau. Dispersal ability did not explain the habitat controlled spatially distributed occurrences of plant species. This might indicate a low frequency of local extinctions at the sandstone plateaus, especially of the poorly dispersed species, possibly because plant populations survive fire or drought disturbances in local sheltered places. Space and habitat controlled species patterns at one plateau were quite distinct from patterns at the other plateaus. This might be due to unmeasured habitat factors (e.g. unrecorded soil variation or human disturbance history) or the preferential, surveyor biased sampling procedure.     

Density dependence, lifespan and the evolutionary dynamics of longevity

Longevity is a life-history trait that is shaped by natural selection. Evolution will shape mortality trajectories and lifespans, but until now the evolutionary analysis of longevity is based principally on a density-independent (Euler-Lotka) framework. The effects of density dependence on the evolution of lifespan and mortality remain largely unexplored. We investigate the influence of different population demographies on the evolution of longevity, and show how these can be linked to adaptive radiations. We present a range of models to explore the intraspecific and interspecific density effects on longevity and, consequently, diversification. We show how the magnitude, type, and timing of mutation can also affect fitness, invasion and diversification. We argue that fitness of alternative strategies under a range of different demographic structures leads to flat, as opposed to rugged, landscapes and that these flat fitness surfaces are important in the evolution of lifespan and senescence.     

Pollinators, flowering phenology and floral longevity in two Mediterranean Aristolochia species, with a review of flower visitor records for the genus

The pollination of Aristolochia involves the temporary confinement of visitors inside the flower. A literature review has shown that some species are visited by one or a few dipteran families, while others are visited by a wider variety of dipterans, but only some of these are effective pollinators. We observed flowering phenology and temporal patterns of pollinator attendance in diverse populations of Aristolochia baetica and A. paucinervis, two species that grow in SW Spain, frequently in mixed populations. The two species had overlapping floral phenologies, extended flowering periods and long-lived flowers. A. baetica attracted a higher number of visitors than A. paucinervis . Drosophilids and, to a lesser extent, phorids, were the main pollinators of A. baetica, whereas in A. paucinervis , phorids were the only pollinators. Attendance to A. paucinervis flowers by phorids in mixed populations was markedly lower than in pure populations. This effect was more evident in years with lower pollinator density. Our results suggest that A. baetica and A. paucinervis may compete for pollinators in mixed populations.     

Low concentration structural dynamics of lanreotide and somatostatin‐14

Lanreotide, a synthetic cyclic octapeptide, analogue of the peptide hormone somatostatin‐14 (SST‐14), is routinely used as a long‐acting medication in the management of neuroendocrine tumors. Despite its therapeutic importance, low concentration structural data is still lacking for lanreotide. In fact, the major part of the previous structural investigations were focused on the remarkable aggregation properties of this peptide, appearing at high concentrations (>5 mM). Here, we have applied three optical spectroscopic techniques, i.e. fluorescence, circular dichroism and Raman scattering, for analyzing the structural dynamics at the concentrations below 5 mM, where lanreotide exists either in a monomer state or at the first stages of aggregation. The obtained data from lanreotide were discussed through their comparison with those collected from SST‐14, leading us to the following conclusions: (i) The central D‐Trp residue, forming with its adjacent Lys the main receptor interacting part of lanreotide, keeps a constant high rotational freedom whatever the environment (water, water/methanol, methanol). (ii) A solvent‐dependent tight β‐turn, belonging to the type‐II' family, is revealed in lanreotide. (iii) Raman data analyzed by band decomposition in the amide (I and III) regions allowed estimation of different secondary structural elements within the millimolar range. Interestingly, the applied protocol shows a perfect agreement between the structural features provided by the amide I and amide III Raman markers. © 2014 Wiley Periodicals, Inc. Biopolymers 101: 1019–1028, 2014.     

Variability at different spatial scales of a coralligenous assemblage at Giannutri Island (Tuscan Archipelago,northwest Mediterranean)

This study was carried out on the rocky cliffs of Giannutri Island (Tyrrhenian Sea, Italy) to test the hypothesis that coralligenous assemblages are consistent within the bathymetric range considered (25–35 m depth) over three different spatial scales (1000 m, 100 m and 10 m). A multi-factorial sampling design was used to assess patterns of vertical distribution in the studied area. Data on the percent cover of algae and invertebrates were collected at three depths (25, 30 and 35 m) using a photographic method, and percentage cover was obtained using a visual method. Analysis of the results using ANOVA indicated that the distribution and abundance of algae and some invertebrates of the sublittoral assemblages are clearly heterogeneous. Algae, sponges and bryozoans showed significant variability in distribution and abundance at different depths, but this variability was not consistent amongst transects. Ascidians did not show any variability, while the abundance of anthozoans differed significantly amongst transects. We concluded that heterogeneity in the distribution and abundance of the taxa analysed is related to the smallest spatial scale investigated (10's of m). Some of the possible causes of the observed variability are discussed.     

Scuba diving damage on coralligenous builders: Bryozoan species as an indicator of stress

The effects of scuba diving activities on coralligenous concretions builders in the Mediterranean Sea are reported for a non-marine protected area (non-MPA). Five erect bryozoan species, which are particularly vulnerable due to their fragile structure, were investigated: Adeonella calveti, Myriapora truncata, Pentapora fascialis, Reteporella grimaldii, and Smittina cervicornis. These species were sampled at frequently and rarely visited diving sites to the maximum depths reachable with the most common recreational diving certifications (i.e., 40 m). To do this, a non-destructive photographic sampling technique was used to minimize any impact on the benthic communities. For each sample, the number of colonies, their width, coverage, type of injury and degree of exposure were quantified using image analysis software. The number of species differed between the frequently and rarely visited diving sites, and frequently visited sites had significantly lower number of colonies and reduced colony width. Species-specific response to stress was associated with colony morphology and skeleton rigidity. Both the type of injury and colony position within the coralligenous habitat were affected by the presence of scuba divers. A linear model was proposed to analyse the response of bryozoans to scuba diving pressure. The results reported here suggest that P. fascialis and R. grimaldii could serve as robust species indicators of diving stress.