Brachiopod assemblages from the Early-Middle Jurassic transition in the Eastern Subbetic (SE Spain): Systematic and palaeobiogeographic implications and palaeoenvironmental significance

New data on brachiopod assemblages recorded in the Eastern Subbetic area (Alicante, SE Spain) and attributed to the Early Bajocian (Humphriesianum Zone and/or immediately older) are provided. Eleven species have been distinguished and reported for the first time in the Subbetic domain of the Betic Cordillera. The description of the morphological evidences on each analysed taxa, especially in relation to their internal morphology, brings new implications in the systematics of the Middle Jurassic brachiopods. The analysis of faunistic affinity between the recorded assemblages and those from other palaeogeographic domains, shows that the Subbetic brachiopod fauna has a clear Mediterranean affinity, as proved by the different species belonging to the genera Striirhynchia, Septocrurella, Mondegia?, Karadagithyris, Linguithyris, Papodina?, Viallithyris?, and Zugmayeria?. It is also evidenced that the Early-Middle Jurassic transition in the Eastern Subbetic accounted, in qualitative terms, a remarkable interval of faunistic renewal in the brachiopod assemblages, strongly influenced by a complex tectonic and stratigraphic framework controlled by a period of intense extensional tectonics, globally framed in the evolution of the Atlantic Ocean.

Community attributes determine facilitation potential in a semi-arid steppe

Studies on positive plant–plant relations have traditionally focused on pair-wise interactions. Conversely, the interaction with other co-occurring species has scarcely been addressed, despite the fact that the entire community may affect plant performance. We used woody vegetation patches as models to evaluate community facilitation in semi-arid steppes. We characterized biotic and physical attributes of 53 woody patches (patch size, litter accumulation, canopy density, vegetation cover, species number and identity, and phylogenetic distance), and soil fertility (organic C and total N), and evaluated their relative importance for the performance of seedlings of Pistacia lentiscus, a keystone woody species in western Mediterranean steppes. Seedlings were planted underneath the patches, and on their northern and southern edges. Woody patches positively affected seedling survival but not seedling growth. Soil fertility was higher underneath the patches than elsewhere. Physical and biotic attributes of woody patches affected seedling survival, but these effects depended on microsite conditions. The composition of the community of small shrubs and perennial grasses growing underneath the patches controlled seedling performance. An increase in Stipa tenacissima and a decrease in Brachypodium retusum increased the probability of survival. The cover of these species and other small shrubs, litter depth and community phylogenetic distance, were also related to seedling survival. Seedlings planted on the northern edge of the patches were mostly affected by attributes of the biotic community. These traits were of lesser importance in seedlings planted underneath and in the southern edge of patches, suggesting that constraints to seedling establishment differed within the patches. Our study highlights the importance of taking into consideration community attributes over pair-wise interactions when evaluating the outcome of ecological interactions in multi-specific communities, as they have profound implications in the composition, function and management of semi-arid steppes.

Subwavelength beams with polarization singularities in plasmonic metamaterials

We investigated the diffraction behavior of plasmonic Bessel beams propagating in metal-dielectric stratified materials and wire media. Our results reveal various regimes in which polarization singularities are selectively maintained. This polarization-pass effect can be controlled by appropriately setting the filling factor of the metallic inclusions and its internal periodic distribution. These results may have implications in the development of devices at the nanoscale level for manipulation of polarization and angular momentum of cylindrical vector beams.