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  • 1
    Publication Date: 2019-04-26
    Description: The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and best-understood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better-define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a co-ordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
    Publication Date: 2024-01-12
    Description: A taxonomic revision of the genus Guatteria, including the former genera Guatteriella, Guatteriopsis and Heteropetalum is given. Within the genus Guatteria 177 species are recognized, 25 of which are new. Included are chapters on the history of the taxonomy of the genus, morphology, wood anatomy, karyology, palynology, chemistry, flower biology and pollination, dispersal, distribution and ecology, phylogeny and molecular studies, conservation, and uses. A synoptical key to all species is included, as well as two dichotomous keys, one for the species of Central America and Mexico, and one for the species of NE, E and SE Brazil. The species treatments include descriptions, full synonymy, geographical and ecological notes, vernacular names and taxonomic notes. For all species distribution \nmaps are made. A complete identification list with all exsiccatae studied, an index to vernacular names and an index of scientific names is included at the end.
    Keywords: Annonaceae ; chemistry ; descriptions ; flower biology and pollination ; Guatteria ; Guatteriella ; Guatteriopsis ; Heteropetalum ; history ; molecular studies ; morphology ; Neotropics ; palynology ; phylogeny ; taxonomy ; vernacular names
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
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    In:  Mededelingen van het Botanisch Museum en Herbarium van de Rijksuniversiteit te Utrecht vol. 285 no. 1, pp. 3-440
    Publication Date: 2024-01-12
    Description: This study was undertaken, in April 1964, at the suggestion of Prof. Dr. J. Lanjouw. The need for such a revision, was, however, stressed by the authors of the subtribe, viz. PAX et K. HOFFMANN, who, while delimiting these genera, remarked that the Systematics of both the (main) genera of this subtribe (viz. Paronychia and Herniaria) required a thorough study. By that remark they implicitly wanted to convey the difficulties encountered in studying the two genera. As a matter of fact theirs is the only account covering the whole group. There is no previous review of all the species of Paronychia, and CORE\xe2\x80\x99s account (1941 of the 21 North American species is the only study of this genus. Herniaria has been studied by F. N. WILLIAMS (1896) and F. HERMANN (1937), but both the accounts are brief and sketchy reviews, and cannot be described as revisions. The present study was, therefore, undertaken to clear up the taxonomic position of these genera. The study was greatly facilitated by the extensive collections made by various workers (in some areas for the first time in history) in recent years, particularly during the past two or three decades. It is indeed immensely gratifying to note that well over 13500 herbarium sheets (about 10500 of them obtained on loan from nearly 45 herbaria) were available for study. A thorough examination of such a vast collection has necessitated a re-evaluation most of the infra-generic groupings, and, moreover, resulted in a considerable increase in the number of species belonging to the two main genera. Of the nine genera originally included by PAX et HOFFMANN in this subtribe, viz. Sphaerocoma, Corrigiola, Gymnocarpos, Lochia, Sclerocephalus, Paronychia, Siphonychia, Herniaria and Philippiella, only eight are retained in this account, the ninth (i.e. Siphonychia) is merged with Paronychia. The latter is subdivided (for the first time) into three subgenera (Siphonychia, Paronychia and Anoplonychia); the subgenus Paronychia includes 57 species of which all but one belong to the section Paronychia. The latter in turn comprises 5 sub-sections and 8 series, all of them being set up for the first time. The second major subgenus, Anoplonychia, includes 48 species grouped into two sections and four subsections. In all there are 29 species being described for the first time (20 in Paronychia, 7 in Herniaria and 2 in Corrigiola) in addition to a number of infra-specific taxa. These figures, however, do not include the taxa published by me in two earlier papers (1966, 1967).\nIn spite of the extensive collecting, however, most of the new species as well as the infra-specific taxa are known from one or a few gatherings only, and are, accordingly, described in this account as endemics. Obviously, in some of these cases more material is highly desirable. Some regions are still rather poorly known or botanized. This is particularly true of Central and Eastern Turkey, NE Spain, and parts of Morocco, Ethiopia, Peru and Chile. Moreover, leaving aside matters of taxonomic interest, which I have endeavoured to clarify in this account, there still remain some problems which require further investigation. The main genera require population studies, and the evidence available so far for hybridization needs to be substantiated. Similarly, cytotaxonomic and experimental studies are needed to help solve some of the problems concerning the delimitation of the infra-specific taxa, especially in the genus Herniaria. Another highly intriguing matter that requires further investigation concerns the correct interpretation of the petals which in most of the genera of this group are filiform structures resembling staminodia, but in two of the genera (viz. Corrigiola and Sphaerocoma) they are quite well-developed. Yet another issue that still remains to be settled, though on a much broader scale, is the long-standing controversy as to whether or not these genera, along with the other members of the subfamily Paronychioideae, are sufficiently distinct from the rest of the family Caryophyllaceae so as to justify their inclusion in a separate family. This is a matter that cannot be settled by the study of a small group of genera, or a small tribe of a large family. I have, therefore, not gone into this problem, and have followed the treatment of PAX & HOFFMANN in the disposition of this group of genera.
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 4
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    In:  Scripta Geologica vol. 149, pp. 1-158
    Publication Date: 2024-01-12
    Description: We present estimates for head and body length (HBL) of fossil rodents. We assembled HBL data and tooth row length data (LTR, UTR) for a large number of extant rodents, and calculated regression lines of HBL on LTR and UTR for all rodents together (all-rodents equation), and for separate taxonomic groups (family equations). In fossil rodents, data for complete tooth rows are scarce, therefore we use the sum of the lengths of the teeth (LRsum, URsum) as a surrogate for tooth row length. The relation between this parameter and real tooth row length (LTR, UTR) is calculated on the basis of a number of populations for which both parameters are available. We estimate HBL of fossil rodents, using LRsum and URsum and the regression lines of extant rodents, and we compare the results for lower and upper tooth row when both are available. For each species we calculate HBL through the all-rodents equation and through the family equation. We consider the amount of difference between these two values as a measure of the reliability of this method.
    Keywords: Rodentia ; body mass ; teeth ; tooth row length
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Format: application/pdf
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