The Ichnogenus Undichna, With Examples From The Permian Of The Falkland Islands

Abundant, well-preserved and variable species of Undichna are described from the Permian of the Falkland Islands. The environment is considered to be non-marine and the traces are associated with turbidite and rhythmite deposits. There are strong similarities between the Undichna and other ichnogenera of the Falkland Islands and those of the Eastern Cape Province of South Africa, thus strengthening the view that the missing eastern end of the Permian Karoo Basin is present in the Falklands. Undichna binaU. insolentia occur associated within glacially influenced rhythmite and turbidite facies of a non-marine basin in the Cantera Formation, Camilla Creek, East Falkland. U. quina isp. nov. occurs on Sea Lion Island and is associated with thin (mm–cm scale) graded interbeds between thicker amalgamated sandstones in a sequence deposited by density currents derived from a delta feeding the same non-marine basin. The elements that comprise Undichna traces are (1) single sinusoidal grooves, (2) paired sinusoidal grooves, (3) broad shallow grooves, (4) repeated arcuate imprints, (5) irregular grooves, (6) striated brush-like imprints. A distinct, repeated morphology is only produced by a constant activity of the tracemaker (generally a fish). Irregular activity (e.g. acceleration, sharp turns) or current action produces non-constant morphology, lacking the defining regularity of the ichnogenus Undichna. Such irregular forms can frequently be identified as a modified expression of a described ichnospecies, but morphologically do not fall within the definition of the ichnospecies. It is suggested that rather than create new names they should be referred to as 'cf. Undichna isp.' (irregular form).     

The non-native vascular flora of the Falkland Islands

Summary

Non-native species form a significant, but under-recorded, component of the Falkland Islands vascular flora. With this in mind a comprehensive re vie w of the non-native flora of the Falkland Islands was undertaken for the first time since the publication of the definitive Flora in 1968. We have recorded 175 non-native taxa, from 46 families, from the Falkland Islands which are listed with accompanying notes on habitat, status and distribution. Twenty-nine of these are likely to be commonly encountered, though only Aira praecox, Cerastium fontanum, Rumex acetosella and Sagina procumbens are near ubiquitous throughout. The origins of much of the non-native flora are obscure, however most species seem to be of European descent, and a significant proportion of taxa seem to have become established after introductions for agricultural and horticultural purposes.     

Preliminary stock assessment of the Patagonian toothfish longline fishery around the Falkland Islands

An experimental fishery for Patagonian toothfish Dissostichus eleginoides was opened in Falkland Island waters briefly in 1992 and then from April 1994. One to two longlines per vessel were usually deployed at night, mostly fishing for 12–30 h at depths between 600 and 2000 m. The characteristics of the vessel, gear, fishing activities and the data collection and analyses methods are described. An initial evaluation of the authors' current understanding of toothfish biology and population dynamics in Falkland Island waters is given. A first analysis of toothfish numbers caught in 1994 suggests that these are changing at rates faster than expected from simple demographic processes. Therefore, despite an intensive monitoring of catch and fishing effort of each vessel, it is still not possible to derive reliable estimates for the size of the toothfish population currently exploited around the Falkland Islands. Migration patterns in and out of the fishery need to be understood before a reliable assessment of the fishery can be made. These results, together with current and future lines of research, are discussed in the light of data available from other toothfish fisheries in austral waters.     

Plant and frond dynamics of the giant kelp,Macrocystis pyrifera,forming a fringing zone in the Falkland Islands

Fluctuations in plant and frond characteristics are described for Macrocystis pyrifera (L.) C. Agardh (Laminariales, Phaeophyta) forming a fringing zone in the Falkland Islands. Giant kelp plants were sampled along a transect in the austral autumn (May 1986) and late spring (December 1986) which, according to previous frond weight analysis, were the times when extremes in population parameters were expected. Plant density and holdfast wet weights were similar for both seasons, but plants had more fronds and the fronds weighed more in spring than in autumn. Consequently, in autumn the frond biomass (1·1 wet kg m^?2) and productivity (34·1 wet g m^?2 d^?1) were lower than in spring, when a biomass of 5·0 wet kg m^?2 and a productivity of 72·4 wet g m^?2 d^?1 were recorded. Production of new fronds and loss of old fronds were determined at monthly intervals between April 1986 and March 1987. New frond production rates followed fluctuations in the quantity of light and varied between 0·08 and 0·48 fronds per plant per day. Frond loss rates did not show a seasonal pattern and fluctuated between 0·05 and 0·42 fronds per plant per day. It is suggested that the Falkland Islands Macrocystis population is more stable than most other giant kelp beds at high latitudes, because of the absence of winter storms.     

The Nature of Evolutionary Radiations: A Case Study Involving Devonian Trilobites

Evolutionary radiations, times of profound diversification of species against a broader background of more muted evolutionary change, have long been considered one of the fundamental patterns in the fossil record. Further, given the important role geological, environmental, and climatic processes play in causing speciation, analyzing the biogeographic context of radiations can yield important insight into their evolutionary mechanisms. In this study we examine biogeographic patterns and quantify rates of speciation in a diverse group of Devonian trilobites, the calmoniids, that has been hailed as a classic paleontological example of an evolutionary radiation. In particular, a phylogenetic biogeographic analysis—modified Brooks Parsimony Analysis—was used to examine the processes and geographic setting of speciation within the group. Results indicate that the Malvinokaffric Realm was a geographically complex area, and this geographic complexity created various opportunities for speciation via geodispersal and vicariance that created the fuel that fed the speciation in these taxa. Part of the geographic complexity was created not only by the inherent geologic backdrop of the region, but the overlying changes of sea level rise and fall. Rates of speciation were highest when sea level was lowest. Low sea level encouraged isolation of faunas in different tectonic basins. By contrast, sea level rise facilitated range expansion and geodispersal to other distinct tectonic basins, and speciation rates concomitantly fell; however, the taxa with the expanded ranges were later fodder for diversification when sea level fell again. Here we present a view of evolutionary radiations driven fundamentally by external abiotic factors—geology and climate—that cause range expansion and opportunities for geographic isolation with resultant rapid speciation.     

Reanalysis of Heintzichthys gouldii (Newberry), an aspinothoracid arthrodire (Placodermi) from the Famennian of northern Ohio, with a review of brachythoracid systematics

Heintzichthys gouldii is redescribed based on new material from the Interstate 71 Paleontological Salvage Project (Cleveland Museum of Natural History, 1966-67). Phylogenetic analysis of brachythoracid arthrodires clearly shows the monophyly of Camuropiscidae and the aspinothoracid arthrodires. Heintzichthys gouldii and Gorgonichthys clarki are removed from Dinichthyidae and placed within aspinothoracid arthrodires. The remaining members in the family Dinichthyidae are united solely by plesiomorphic characters. A number of putative synapomorphies for the eubrachythoracid arthrodires are questioned; however, the validity of this taxon is supported by three synapomorphies.     

Trilobites Calmoniidae de l'Ordovicien supérieur du Maroc et les origines de la Province Malvino-Cafre

A re-examination of the trilobite Baniaspis globosa Destombes (Phacopina) from the Ashgill of the Anti-Atlas (Morocco) shows that it has several derived characters which allow us to classify it in the family Calmoniidae. Calmoniids were characteristic members of the Malvino-Kaffric province during the Lower Devonian. Hence we regard the origins of this palaeogeographic province as located on the northern Gondwanan margin as early as Ashgill, or even Caradoc, times. We agree with those authors who have suggested that the trilobite associations present in the Anti-Atlas, the Montagne Noire (France) and Bohemia during the earlier Ordovician argue against the existence of a 'proto-Tethys' ocean.     

Exploratory deep-sea fishing in the Falkland Islands, south-western Atlantic

Records of demersal deep-sea fish assemblages in waters around the Falkland Islands (Patagonian shelf area) are rare. Twenty deep-water stations to the east and south of the Falkland Islands were sampled by commercial bottom trawl deployed in upper, middle and lower benthopelagic zones (depth range of approximately 500-1000 m). Forty-one species (22 families) of teleost fish were recorded, 10 species (two families) of elasmobranch and one species of agnathan. Different assemblages of fish were found to characterize each depth zone (e.g. Moridae in deeper waters, Bothidae and Rajidae in shallower waters), with diversity being greatest in the mid-zone and biomass greatest in the upper and lower zones. Some species occurred in all zones but showed depth-related abundance. Four species, namely the grenadiers Macrourus carinutus and Coelorhynchus fasciatus , the southern blue whiting Micromesistius australis , and the Patagonian toothfish Dissostichus eleginoides , accounted for 85% by weight of all fish caught. Quantitative sampling of selected species revealed depth-related variations in their population structure. Length-frequency analyses are presented for M. carinatus and D. eleginoides and show a tendency for larger individuals to inhabit deeper water. Discard rates from the commercial catch were sometimes high, particularly for the smaller species, raising concerns about the impact of a fishery on by-catch species. The potential for deep-sea fisheries in Falkland waters is discussed and further studies are suggested in the light of developing oil, gas and fishing industries. The presence of some invertebrate taxa is recorded.     

Socio-spatial levels in linearity analysis of dominance hierarchies: a case study on elephant seals

The analysis of linearity is a key aspect of the study of dominance hierarchies. To study the effect of the choice of socio-spatial level of analysis, we calculated linearity in a large set of southern elephant seal (Mirounga leonina) hierarchies from two populations (Valdés Peninsula and Falkland Islands). The socio-spatial level of analysis affects the observational effort, the completeness of matrices, and the frequency of unknown relationships. These factors, in turn, have a notable effect on linearity. We conclude that dominance should be studied at the local level, where the absence of structural zeros and the low incidence of observational zeros produce complete matrices, well rooted in the true spatial and social structure of the population. Depending on the specific social system, the extrapolation of dominance from the local level to higher levels may result in sparse matrices, and in biased estimates of linearity. The variation of the socio-spatial level of analysis may in part explain the contrasting results obtained in different studies of linearity of dominance hierarchies. Electronic Publication