Belén Estébanez

Ecological impacts of atmospheric pollution and interactions with climate change in terrestrial ecosystems of the mediterranean basin: Current research and future directions

Mediterranean Basin ecosystems, their unique biodiversity, and the key services they provide are currently at risk due to air pollution and climate change, yet only a limited number of isolated and geographically-restricted studies have addressed this topic, often with contrasting results. Particularities of air pollution in this region include high O3 levels due to high air temperatures and solar radiation, the stability of air masses, and dominance of dry over wet nitrogen deposition. Moreover, the unique abiotic and biotic factors (e.g., climate, vegetation type, relevance of Saharan dust inputs) modulating the response of Mediterranean ecosystems at various spatiotemporal scales make it difficult to understand, and thus predict, the consequences of human activities that cause air pollution in the Mediterranean Basin. Therefore, there is an urgent need to implement coordinated research and experimental platforms along with wider environmental monitoring networks in the region. In particular, a robust deposition monitoring network in conjunction with modelling estimates is crucial, possibly including a set of common biomonitors (ideally cryptogams, an important component of the Mediterranean vegetation), to help refine pollutant deposition maps. Additionally, increased attention must be paid to functional diversity measures in future air pollution and climate change studies to establish the necessary link between biodiversity and the provision of ecosystem services in Mediterranean ecosystems. Through a coordinated effort, the Mediterranean scientific community can fill the above-mentioned gaps and reach a greater understanding of the mechanisms underlying the combined effects of air pollution and climate change in the Mediterranean Basin.

Ultrastructure of the spore in four Japanese species of Ptychomitrium Fürnr. (Musci)

The ultrastructure of the mature spore in four Japanese species of the acrocarpous moss genus Ptychomitrium is presented. In all species the spores have a similar pattern: there is no recognisable aperture nor sporoderm polarity, exine and perine are poorly developed, cytoplasm only occasionally shows polarity, and plastids have a well developed inner membrane system. The presence of frequent intine protrusions is a remarkable feature of this genus. A multilaminar structure of the exine, already observed in Grimmia, occurs also in these species although here it is less pronounced. The significance of these features is discussed within these species, as well as in comparison to other taxa, especially the genus Grimmia.

Does Spore Ultrastructure Mirror Different Dispersal Strategies in Mosses? A Study of Seven Iberian Orthotrichum Species

Most mosses have xerochastic dispersal (i.e., they open their capsules when conditions are dry), which is thought to favor long-distance dispersal. However, there are several species that use a hygrochastic strategy: spores are dispersed when conditions are wet. The significance of this strategy in the Mediterranean region is unknown. In this study, we explored whether ultrastructural features related to differences in spore resistance may explain these different strategies of spore dispersal. To this end, we examined the ultrastructural features of the spores of seven closely related species in the moss genus Orthotrichum. These species all grow as epiphytes in sub-Mediterranean forests, and the group includes both xerochastic and hygrochastic members. First, we found that the spore wall layers exhibit several features previously undescribed in mosses. Second, we discovered that there are only subtle differences in spore ultrastructure with regards to spore wall thickness, the degree of plastid development, or the storage substances used. We suggest that the hygrochastic dispersal in mosses from Mediterranean environments might be related to a safe-site strategy, rather than to drought avoidance, and we underscore the necessity of conducting spore ultrastructural studies on a greater number of bryophyte species.

Orthotrichum consobrinum Cardot in Western Europe and South-Western Asia

Abstract Orthotrichum consobrinum Cardot, a moss that was earlier considered an endemic to the Sino-Japanese Region, has been found in the north of the Iberian Peninsula (Spain) and in north-eastern Anatolia (Turkey). Comparison of Spanish and Turkish material with eastern Asiatic specimens revealed no relevant morphological differences, and the specimens from both disjunct populations showed the same range of variation of the species attributes. However, the morphological analysis has revealed some distinctive features of the species that had been overlooked in the past. An updated description of this Euro-Asiatic moss is provided here.

The Sporophyte-Gametophyte Junction in Five Species of Pleurocarpous Mosses

Abstract We have studied the sporophyte-gametophyte junction at the post-meiotic stage in five pleurocarpous mosses: Isothecium myosuroides Brid., Leucodon canariensis (Brid.) Schwaegr., Leptodon longisetus Mont., Neckera cephalonica Jur. & Unger, and Neckera intermedia Brid. In all five species the foot does not penetrates the leafy caulidium. The junction in all of them corresponds to a “bryalean pattern”, with transfer cells both in the gametophyte and sporophyte. However, except in Neckera intermedia, there were several layers of foot transfer cells, deviating from the typical 1:1 arrangement in this model. At this stage, the tissues of both foot and vaginula were degenerating. Vaginular cells surrounding the foot became empty and thin-walled. Opportunistic microorganisms were often found. The five species differ with respect to the number of layers of transfer cells and the degree of development of foot hydroids.

Mature spores of four pleurocarpous mosses in the Canary Islands: ultrastructure and early germination stages

Abstract We describe the morphology and ultrastructure of mature spores of four epiphytic pleurocarpous mosses from the Canary Islands laurel forest: Leucodon canariensis (Brid.) Schwägr., Cryptoleptodon longisetus (Mont.) Enroth., Neckera cephalonica Jur. & Unger., and N. intermedia Brid. The two Neckera species are strictly isosporic, while the capsules of L. canariensis contain viable spores of two classes—uni- or multicellular, medium-sized (26–48 µm) spores; and multicellular, large (50–94 µm) spores. Also in C. longisetus, two different kinds of viable spores are produced in the capsules—unicellular, small spores (11–24 µm) and medium-sized (26–35 µm) spores. These observations suggest anisospory for both species. Intracapsular spore germination is observed in three species, but not in N. cephalonica. Spore wall stratification of the four species follows the typical pattern for mosses—perine, exine and intine. The ornamentation pattern is uncharacteristic, with perine variously papillose. All spores are inaperturate. The cytoplasm shows abundant lipid-like inclusions and chloroplasts with well-developed thylakoids. The taxonomic significance of the spore characteristics is discussed.

Amorphous mineral incrustations in the moss Homalothecium sericeum

Abstract Internal mineral deposits in stem and seta were found in living, healthy-looking specimens of the moss Homalothecium sericeum from a Spanish locality. The deposits consisted of an amorphous crust of smooth texture. After examination with EDS probes coupled to a transmission and a scanning electron microscope, and X-ray diffraction analysis, the minerals were identified as mainly opal, carbonates, and Fe and Al hydroxides, although it is irregular throughout a given mineralized region of the moss. These mineral crusts are considered to be the product of biomineralization of ions taken from the substratum. A comparison is established between these deposits and the mineral crystals found in a previous study of Hookeria lucens.

The occurrence of lipidic storage compounds in Grimmia (Bryopsida)

Abstract Using transmission electron microscopy, histochemistry, and analytical techniques, lipids are shown to constitute the most important cytoplasmic fraction in ten species of Grimmia. Major compounds common to these species are identified as β-sitosterol, linoleic acid, and α-amyrin acetate. The triterpenoid, α-amyrin, has rarely been reported in mosses, and its possible chemotaxonomic value is pointed out.

Spores potentially dispersed to longer distances are more tolerant to ultraviolet radiation: A case study in the moss genus Orthotrichum

PREMISE OF THE STUDY Ultraviolet (UV) radiation influences the viability of algal spores and seed-plant pollen depending on the species, the dose, and the wavelength. In bryophytes, one of the dominant groups of plants in many habitats, UV radiation could determine their spore dispersal strategy, and such data are critical for reconstructing the ancestral state in plants and for determining the distribution range and persistence of bryophyte species. METHODS Spores of four bryophyte species of the moss genus Orthotrichum that were either hygrochastic or xerochastic (spores dispersed under wet or dry conditions, respectively) were exposed to realistic doses of UV radiation under laboratory conditions. Spore viability was evaluated through germination experiments and, for the first time in bryophytes, ultrastructural observations. Given that the UV-B doses used were relatively higher than the UV-A doses, the UV effect was probably due more to UV-B than UV-A wavelengths. KEY RESULTS All four species reduced their spore germination capacity in a UV dose-dependent manner, concomitantly increasing spore ultrastructural damage (cytoplasmic and plastid alterations). Most spores eventually died when exposed to the highest UV dose. Interestingly, spores of hygrochastic species were much more UV-sensitive than those of xerochastic species. CONCLUSIONS UV tolerance determines moss spore viability, as indicated by germination capacity and ultrastructural damage, and differs between spores of species with different dispersal strategies. Specifically, the higher UV tolerance of xerochastic spores may enable them to be dispersed to longer distances than hygrochastic spores, thus extending more efficiently the distribution range of the corresponding species.