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Orthotrichum ibericum sp. nov., a new moss from the Iberian Peninsula
... In this study, we assess whether ultrastructural features (plastid development, storage substances, and spore wall configuration) are associated with spore dispersal strategies. To minimize taxonomic differences, we used seven related species, all belonging to the same section of the moss genus Orthotrichum Hedw., in which both xerochastic and hygrochastic dispersal have been observed [18][19][20]. ...
... The size range we observed matches those given in the most commonly used descriptions of the genus Orthotrichum (e.g. [18][19][20]), and although O. acuminatum tends to have larger spores, there was nonetheless a high degree of overlap with other 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 ibericum Lara & Mazimpaka fue descrito como un epífito pionero en los bosques de Quercus pyrenaica Willd. del centro-occidente peninsular (Lara & Mazimpaka 1993). Aunque en su momento se realizaron diversas campañas de herborización en las que se prospectó muy diversas zonas de melojares, sólo pudo ser encontrado en el Sistema Central (sierras de Gredos, Gata, Estrela) y en el tramo más atlántico de los Montes de Toledo (sierra de Guadalupe). ...
A catalogue of 51 corticolous taxa (eight hepatics, and 43 mosses) is presented. Among the factors accounting for so high a richness in epiphytic bryophytes in a mediterranean environment, the most relevant are: a large representation of the genus Orthotrichum (10 species) and a high number of facultative epiphytes which, from surrounding rocks or soil, colonize tree bases or trunks. -from English summary
Intercontinental disjunct distributions are a main issue in current biogeography. Bryophytes usually have broad distribution ranges and therefore constitute an interesting subject of study in this context. During recent fieldwork in western North America and eastern Africa, we found new populations of a moss morphologically similar to Orthotrichum acuminatum. So far this species has been considered to be one of the most typical epiphytic mosses of the Mediterranean Basin. The new findings raise some puzzling questions. Do these new populations belong to cryptic species or do they belong to O. acuminatum, a species which then has a multiple-continent disjunct range? In the latter case, how could such an intercontinental disjunction be explained? To answer these questions, an integrative study involving morphological and molecular approaches was conducted. Morphological results reveal that Californian and Ethiopian samples fall within the variability of those from the Mediterranean Basin. Similarly, phylogenetic analyses confirm the monophyly of these populations, showing that O. acuminatum is one of the few moss species with a distribution comprising the western Nearctic, the western Palaearctic and Palaeotropical eastern Africa. Pending a further genetic and phylogeographical study to support or reject the hypothesis, a process of long-distance dispersal (LDD) is hypothesized to explain this distribution and the origin of the species is suggested to be the Mediterranean Basin, from where diaspores of the species may have migrated to California and Ethiopia. The spore release process in O. acuminatum is revisited to support the LDD hypothesis, 2015, 180, 30–49.
Relationships between the species of the genus Orthotrichum (Musci, Orthotrichaceae) are analyzed with cladistic methods. As a result, a new phylogeny is presented: Orthotrichum paraguense is moved to a genus of its own, Sehnemobryum gen.nov. and the remaining species are shown to make up a monophyletic group, which is tentatively divided into eight subgroups to which no formal names have been assigned. Orthotrichum callistomum (with immersed stomata) is shown to be closer related to species with superficial stomata in sect. Leiocarpa, than to any species with immersed stomata, and O. cyathiforme (with superficial stomata) seems related to species with immersed stomata in subg. Pulchella. The earlier proposed relationship between O. obtusifolium and O. exiguum is supported, whereas no support is given for a separation of the species O. gymnostomum and O. obtusifolium into a genus of their own. Immersed stomata most likely developed twice within the genus, whereas a doubling of the chromosomes from a basic number of n = 6 followed by subsequent loss of one chromosome to n = 11 may have happened once or twice. The study supports the earlier assumption that the genus Orthotrichum probably originated in the Southern Hemisphere, and that the ancestral species most likely was an epiphyte having superficial stomata, a chromosome number of n = 6, symmetric division of the IPL, well developed endostome segments with a complete median line on the outside, prostomes, the dry exostome teeth recurved, capsules not being constricted below the mouth when dry, and medium-sized leaves. The taxonomic position was confirmed for O. bolanderi, whereas it was changed for O. pulchrum, O. speciosum, O. latimarginatum, and O. anaglyptodon. The systematic position of Orthotrichum cyathiforme is still not clear. The species Orthotrichum callistomum, O. cyathiforme, and O. exiguum seem essential to the understanding of the infrageneric evolution.
Se ha estudiado la brioflora epífita de los melojares del Sistema Central oriental (sierras de Gredos, Guadarrama y Ayllón), con especial atención a la composición de las comunidades pioneras sobre meló jos (Quercus pyrenaica
Willd.) de mediana edad. El área interior de la Cordillera Central alberga tres tipos de melojares que representan las etapas maduras de sendas series de vegetación; éstas se sustituyen geográficamente y con la altitud, de acuerdo con sus requerimientos térmicos y ómbricos. El clima del conjunto del área puede definirse como
mediterráneo continental, si bien se detectan importantes cambios termopluviométricos entre vertientes y a lo largo de su recorrido E-W. Tras la prospección exhaustiva de la zona, fueron elegidos 15 bosques principales y una serie de masas secundarias de características especiales, todos ellos en un relativo buen estado de conservación; estos robledales se encuentran distribuidos por ambas vertientes de las tres sierras consideradas
y a diferentes niveles altitu di nales. El muestreo de las comunidades epífitas se realizó estratificadamente,
considerando diversos niveles de altura en los árboles y colocando en ellos, aleatoriamente, cuadrados flexibles de 4dm , se recogió un mínimo de 120 muestras en cada uno de los melojares principales y un número variable en los bosques de características especiales. En todas estas muestras se determinó el recubrimiento de cada briófito, utilizando para ello seis clases de cobertura. Los datos fueron procesados calculando la frecuencia de aparición y la cobertura media de los epífitos en cada estrato del árbol de los distintos bosques; estos dos parámetros se combinaron luego en un nuevo índice, denominado índice de Significación Ecológica (ISE), que mide la importancia relativa de un briófito en un habitat determinado. Este índice ha servido para comparar gráficamente la importancia de los briófitos sobre distintas especies de árboles, en melojos de distinta edad, en diferentes estratos y en bosques diversos. Asimismo, los valores del ISE se utilizaron como base en el
tratamiento estadístico multivariante de los datos, realizado con el fin de correlacionar la distribución brioepifítica con los gradientes de los principales parámetros termométricos y pluviométricos en el área, así como con diversos índices bioclimáticos; las correlaciones se efectuaron mediante métodos indirectos de clasificación (TWINSPAN) y ordenación (DECORANA), así como por la utilización de una técnica de ordenación directa (DCCA, CANOCO). Junto a los índices bioclimáticos de diversos autoi'es, dos nuevos, denominados índices de sequedad del período más cálido (Sj y Sj), han sido ensayados, estudiándose su valor mediante la correlación con las ordenaciones directas de la variación florística. Los valores de los diversos parámetros climáticos de los
bosques estudiados se extrapolaron a partir de mapas computerizados automáticamente o fueron deducidos mediante la extrapolación de los datos de estaciones cercanas cuando existían gradientes de variaciones medias
conocidos.
Orthotrichum ibericum Lara and Mazimpaka and O. macrocephalum Lara, Garilleti and Mazimpaka have been found in the mountains of north Morocco, which constitute the first records of these species for Africa. New data on the distribution of both species in the Iberian Peninsula are provided, along with comments on the ecology of the species at their new stations and updated distribution maps of the two Orthotrichum species.
RESUMEN-Del estudio de cinco melojares situados en ambas vertientes de la Sierra de Gredos, se ha confeccionado un catálogo de 51 táxones corticícolas (8 hepáticas y 43 musgos). Entre las razones que puedan explicar esta riqueza brioflorística epífita en un entorno mediterráneo, se destaca la amplia representación del género Orthotrichum (10 especies) y el gran número de epífitos facultati vos que, ocasional o habitualmente, colonizan bases y troncos de melojos. Finalmente, se comenta las diferencias que algunos briófitos muestran en la colonización de árboles a lo largo del Sistema Central. Se aportan 13 nuevas citas y 20 segundas para la provincia de Ávila. ABSTRACT-Based on the study of more than 600 samples collected in 5 deciduous oak-woods from both faces of Gredos Range, a catalogue of 51 corticolous taxa (8 hepatics and 43 mosses) is presented. Among the factors accounting for so high a richness in epiphytic bryophytes in a mediter-ranean environment, the most relevant are: a large representation of the genus Orthotrichum (10 species) and a high number of facultative epiphytes which, from surrounding rocks or soil, colonize tree bases or trunks. Finally, comments are devoted to the differences shown by some bryophytes in bark colonization along the Spanish Central Range. 13 new records and 20 second ones are reported for the province of Ávila.
The function of the sporophyte is to produce-via meiosis-spores, and to disperse these sexually reproduced diaspores as efficiently as possible; thus, selection pressures that serve to maintain and modify this function are critical in understanding the evolution of the sporophyte generation. These pressures are significantly different in hygrophytic, mesophytic, and xerophytic habitats, and each of these habitats must be examined separately to ascertain the selection gradients and the structural modifications of plants living in them. Correlations between particular structural features and specialized habitats can be observed, and inferences of function and adaption can be drawn from these data. Reduction in many sporophyte characteristics can be correlated with xerophytic habitats. In particular; seta length is often shorter, capsules broader and erect, and the peristome reduced or absent. Peristome reduction can take place by at least two processes-(1) fusion of parts and (2) reduction of parts. Xerophytic habitats are colonized by mosses that are either tolerant of desiccation or by those that can avoid desiccation periods. The latter have a shortened life cycle and many adaptations different than those that are more poikilohydric. Although the prevalent trend in moss sporophytic evolution is one of reduction, amplification of the sporophyte can be found in mesophytix taxa and, in particular, in the entomophilous members of the Splachnaceae. An understanding of sporophyte modifications in relation to habitat preferences will greatly clarify ideas of evolutionary parallelisms and adaptive specialization.