Spatial demography of Calanus finmarchicus in the Irminger Sea

Continuous Plankton Recorder data suggest that the Irminger Sea supports a major proportion of the surface-living population of the copepod Calanus finmarchicus in the northern North Atlantic, but there have been few studies of its population dynamics in the region. In this paper, we document the seasonal changes in the demographic structure of C finmarchicus in the Irminger Sea from a field programme during 2001/2002, and the associations between its developmental stages and various apparent bio-physical zones. Overwintering stages were found widely at depth (>500 m) across the Irminger Sea, and surviving females were widely distributed in the surface waters the following spring. However, recruitment of the subsequent generation was concentrated around the fringes of the Irminger Sea basin, along the edges of the Irminger and East Greenland Currents, and not in the central basin. In late summer animals were found descending back to overwintering depths in the Central Irminger Sea. The key factors dictating this pattern of recruitment appear to be (a) the general circulation regime, (b) predation on eggs in the spring, possibly by the surviving GO stock, and (c) mortality of first feeding naupliar stages in the central basin where food concentrations appear to be low throughout the year. We compared the demographic patterns in 2001/2002 with observations from the only previous major survey in 1963 and with data from the Continuous Plankton Recorder (CPR) surveys. In both previous data sets, the basic structure of GO ascent from the central basin and G1 recruitment around the fringes was a robust feature, suggesting that it is a recurrent phenomenon. The Irminger Sea is a complex mixing zone between polar and Atlantic water masses, and it has also been identified as a site of sporadic deep convection. The physical oceanographic characteristics of the region are therefore potentially sensitive to climate fluctuations. Despite this, the abundance of C finmarchicus in the region, as measured by the CPR surveys, appears not to have responded to climate factors linked to the North Atlantic Oscillation Index, in contrast with the stocks in eastern Atlantic areas. We speculate that this may because biological factors (production and mortality), rather than transport processes are the key factors affecting the population dynamics in the Irminger Sea. (c) 2007 Elsevier Ltd. All rights reserved.

Revisió del Zygodon viridissimus (Dicks.) R. Brown als herbaris de Barcelona

Con esta nota, siguiendo en parte a SMITH 1978, se rectitica la determinación de Zygodon baumgartneri Malta, identificado como Z. viridissimus (Dicks.) R. Brown en los herbarios BCB y BCF, y llamaremos Z. baumgartneri Malta fo. mediterranea (Malta) comb. nov. a las especies de Z. viridissimus (Dicks.) R. Brown fo. mediterranea Malta.

Bupleurum salicifolium R. Brown in Buch de l'archipel Macaronésien: Taxonomie et Evolution

Se ha realizado un estudio anatómico (frutos y hojas) en 24 poblaciones de Bupleurum salicifolium R. Brown in Buch recogidas en las lslas Canarias Occidentales y Madeira, lo que nos ha permitido evidenciar una estructura uniforme de los frutos. Por el contrario, en las hojas se han observado tres tipos de estructuras, así como la existencia de un canal oleoso, cuya presencia o ausencia coincide con la distribución geográfica de la especie en las diferentes islas. Estas observaciones nos han inducido a hacer una nueva propuesta sistemática: B. salicifolium subsp. salicifolium con dos variedades, var. salicifolium (Madeira y Gomera) y var. robustum comb. nova (Gomera), y subsp. aciphyllum (La Palma, Hierro, Tenerife y Gran Canaria).La importancia de cada uno de los tipos de hojas en las diferentes islas nos ha pemitido asimismo proponer un esquema de dispersión de la especie. La existencia de estructuras consideradas como más primitivas, así como la desaparición de las poblaciones diploides, permiten suponer que B. salicifolium es una especie antigua que conserva su número base de origen x = 8 (En francés).