British Museum

About: British Museum is a archive organization based out in London, Camden, United Kingdom. It is known for research contribution in the topics: Genus & Population. The organization has 2360 authors who have published 4878 publications receiving 95510 citations. The organization is also known as: BM & the British Museum.

Genetic and fossil evidence for the origin of modern humans

Abstract: The origin of living Homo sapiens has once again been the subject of much debate. Genetic data on present human population relationships and data from the Pleistocene fossil hominid record are used to compare two contrasting models for the origin of modern humans. Both genetics and paleontology support a recent African origin for modern humans rather than a long period of multiregional evolution accompanied by gene flow.

The Use of Probability Paper for the Graphical Analysis of Polymodal Frequency Distributions

Abstract: The mathematical analysis of bimodal distributions is very complex. Karl Pearson (1894) investigated the problem and developed equations for the purpose; but found them unsolvable as the ‘majority [of the relations] lead to exponential equations the solution of which seems more beyond the wit of man than that of a numerical equation even of the ninth order’. He did indeed evolve an equation of this order and used it to analyse a few bimodal distributions, but the arithmetic involved was very laborious. Later he (Pearson, 1914) gives a table for ‘Constants of normal curve from moments of tail about stump ’which, as he describes in the introduction, occasionally permits a rough analysis of a distribution which is known to be bimodal. This method is much more rapid than the solution of the nonic equation, but ‘owing to the paucity of material in tails and corresponding irregularity there will be large probable errors’. Gottschalk (1948) discusses the question and shows that inthe special case where the bimodal distribution is symmetrical comparatively simple solutions can be found.

Taxonomic Concepts in the Ascidae, with a Modified Setal Nomenclature for the Idiosoma of the Gamasina (Acarina: Mesostigmata)

Abstract: Generic and familial concepts of the Ascidae Voigts and Oudemans (= Blattisociidae Garman, Aceosejidae Baker and Wharton) are reviewed and modified from a world standpoint. The postembryonic developments of chaetotactic and external morphological features of the body and appendages are discussed. Twenty-two genera in three subfamilies are recognized, keyed, and defined: Arctoseius Thor, Iphidozercon Berlese, Xenoseius nov., and Zerconopsis Hull in the Arctoseiinae Evans; Cheiroseius Berlese and Platyseius Berlese in the Platyseiinae Evans; Aceodromus Muma, Antennoseius Berlese, Arctoseiodes Willmann, Asca Heyden, Blattisocius Keegan, Diseius nov., Gamasellodes Athias-Henriot, Hoploseius Berlese, Lasioseius Berlese, Leioseius Berlese, Melichares Hering, Neojordensia Evans, Proctolaelaps Berlese, Protogamasellus Karg, Rhinoseius Baker and Yunker, and Zercoseius Berlese in the Ascinae Voigts and Oudemans.Newly synonymized genera are Hyattella Krantz under Lasioseius, Mucroseius Lindquist and Orolaelaps DeLeon under Melichares, Garmaniella Westerboer under Proctolaelaps, and Tropicoseius Baker and Yunker under Rhinoseius. Genera removed from the Ascidae include Africoseius Krantz, Digamasellus Berlese, Laelaptoseius Womersley, and Zygoseius Berlese.Modified systems of nomenclature based on holotrichous Gamasina are introduced and applied to setae on the dorsum of the idiosoma and on the venter of the opisthosoma.

The detection of differences among assemblages of marine benthic species based on an assessment of dominance and diversity

Abstract: Summary A criterion for comparing diversity is offered based on dominance patterns involving all the proportional species abundances. The method is applied by plotting percentage cumulative abundance curves. This can reveal that some assemblages cannot be compared in terms of diversity or equitability and that intrinsic diversity indices cannot under these circumstances be relied upon. The behaviour and interpretation of these dominance curves under different circumstances is explored using examples from macrobenthic and marine nematode studies. Dominance curves are also compared with Sanders' rarefaction curves and the relative advantages discussed. It is recommended that these graphical methods be routinely applied to marine biological data before calculating more complex diversity or equitability indices.

Anopheles gambiae complex and disease transmission in Africa

Abstract: Anopheles gambiae complex mosquitoes are present throughout tropical Africa and its offshore islands. Recent work has shown that at least 6 cryptic or “sibling” species are involved. They comprise 2 salt-water species, A. melas and A. merus, 3 freshwater species—provisionally known as species A, B, and C, and a mineralwater species known as species D. Artificial inter-species crosses yield sterile hybrid males. Rarity of hybridization in nature proves the reproductive isolation and valid genetic barriers between these 6 species. Morphological identification of most individuals of both saltwater and the mineralwater species is possible for larvae and adult females, using meristic features and other variable dimensions and ratios. Differential identification of the 3 freshwater species relies almost completely on cytotaxonomic methods. Species A and B occur together in most areas, extending southwards to sub-tropical latitudes and eastward to Mauritius. Proportions of mixed A-B populations may depend directly or indirectly on relative humidity, with A favoured when nocturnal humidities approach saturation. Species B is often absent from areas of highest humidity, but thrives in relatively arid savannas and steppes. Species C and D have relict distributions. Both saltwater species are coastal: melas in West Africa and merus in East Africa and larger islands except Zanzibar; merus also spreads inland. Apart from species C, which is always zoophilic, all members of the complex are proven or probable vectors of human malaria and filariasis, but with some wide contrasts in their levels of vectorial efficiency. Transmission of some arboviruses (Tataguine, O'nyong-nyong) is associated with species B, and perhaps with A also. Species B may transmit setariasis of cattle; melas and merus may also carry enzootic filariae. Much of the confusing ecophenotypic plasticity of A. gambiae sensu lato is attributable to the differential biological characteristics of these 6 species with their dissimilar geographical distributions, behavioural contrasts and asynchronous population dynamics. Shifts in the species balance occur regularly between A and B and between freshwater and saltwater populations. Species C does not interchange so much with B under natural conditions, but may survive at high densities after control of A or B. Additional versatility is caused by genetic polymorphism in some of the species, notably B. This species is the most widespread, and individual females tend to be either endophilic or exophilic, anthropophagic or zoophagic, early biters or late biters, and doubtless other alternatives, according to the arrangement of their floating chromosome inversions. Control measures have to be considered separately for each of the sibling species. House spraying with residual insecticides against endophilic species A is possibly sufficient to break disease transmission (assuming favourable response of ancillary vectors) and even to eradicate A completely. Efficacy of this method against other species in the complex is reduced by their exophily, which can be enhanced by behaviouristic avoidance due to the extremely low threshold of irritability exhibited by gambiae s.l. adults in general. Genetic polymorphism of species B may lead to true behaviouristic resistance. Larvicidal control of species A and B is beneficial, but made operationally difficult by their tendency to utilize temporary breeding-sites. Effectiveness of DDT and cyclodiene insecticides is further limited by the development of physiological insecticide resistance by species A and B. Adequate control of both saltwater species, and probably the mineralwater species also, can be attained by antilarval measures. Prospects of reduction of malaria and filariasis where melas, merus and species A and D are principal vectors may be much better than many people imagine. Widespread prevalence and inherent resilience of species B represents an insurmountable public health obstacle at present. Continued research may provide new control methods for integrated use against these mosquitoes. Concepts such as seeding breeding sites with pathogenic microsporidians or fungi, releasing sterile hybrid males or chemosterilized males, and other even more elaborate genetic control techniques, may be of special relevance to control of gambiae complex mosquitoes and diseases they transmit.