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Sampling Biases (sampling + biase)
Selected AbstractsBreaking taboos in the tropics: incest promotes colonization by wood-boring beetlesGLOBAL ECOLOGY, Issue 4 2001Bjarte H. Jordal Abstract 1,Inbreeding and parthenogenesis are especially frequent in colonizing species of plants and animals, and inbreeding in wood-boring species in the weevil families Scolytinae and Platypodidae is especially common on small islands. In order to study the relationship between colonization success, island attributes and mating system in these beetles, we analysed the relative proportions of inbreeders and outbreeders for 45 Pacific and Old World tropical islands plus two adjacent mainland sites, and scored islands for size, distance from nearest source population, and maximum altitude. 2,The numbers of wood-borer species decreased with decreasing island size, as expected; the degree of isolation and maximum island altitude had negligible effects on total species numbers. 3,Numbers of outbreeding species decreased more rapidly with island size than did those of inbreeders. Comparing species with similar ecology (e.g. ambrosia beetles) showed that this difference was best explained by differential success in colonization, rather than by differences in resource utilization or sampling biases. This conclusion was further supported by analyses of data from small islands, which suggested that outbreeding species have a higher degree of endemism and that inbreeding species are generally more widespread. 4,Recently established small populations necessarily go through a period of severe inbreeding, which should affect inbreeding species much less than outbreeding ones. In addition, non-genetic ecological and behavioural (,Allee') effects are also expected to reduce the success of outbreeding colonists much more than that of inbreeders: compared with inbreeders, outbreeders are expected to have slower growth rates, have greater difficulties with mate-location and be vulnerable to random extinction over a longer period. [source] The ED strategy: how species-level surrogates indicate general biodiversity patterns through an ,environmental diversity' perspectiveJOURNAL OF BIOGEOGRAPHY, Issue 8 2004D. P. Faith Abstract Biodiversity assessment requires that we use surrogate information in practice to indicate more general biodiversity patterns. ,ED' refers to a surrogates framework that can link species data and environmental information based on a robust relationship of compositional dissimilarities to ordinations that indicate underlying environmental variation. In an example analysis of species and environmental data from Panama, the environmental and spatial variables that correlate with an hybrid multi-dimensional scaling ordination were able to explain 83% of the variation in the corresponding Bray Curtis dissimilarities. The assumptions of ED also provide the rationale for its use of p-median optimization criteria to measure biodiversity patterns among sites in a region. M.B. Araújo, P.J. Densham & P.H. Williams (2004, Journal of Biogeography31, 1) have re-named ED as ,AD' in their evaluation of the surrogacy value of ED based on European species data. Because lessons from previous work on ED options consequently may have been neglected, we use a corroboration framework to investigate the evidence and ,background knowledge' presented in their evaluations of ED. Investigations focus on the possibility that their weak corroboration of ED surrogacy (non-significance of target species recovery relative to a null model) may be a consequence of Araújo et al.'s use of particular evidence and randomizations. We illustrate how their use of discrete ED, and not the recommended continuous ED, may have produced unnecessarily poor species recovery values. Further, possible poor optimization of their MDS ordinations, due to small numbers of simulations and/or low resolution of stress values appears to have provided a possible poor basis for ED application and, consequently, may have unnecessarily favoured non-corroboration results. Consideration of Araújo et al.'s randomizations suggests that acknowledged sampling biases in the European data have not only artefactually promoted the non-significance of ED recovery values, but also artefactually elevated the significance of competing species surrogates recovery values. We conclude that little credence should be given to the comparisons of ED and species-based complementarity sets presented in M.B. Araújo, P.J. Densham & P.H. Williams (2004, Journal of Biogeography31, 1), unless the factors outlined here can be analysed for their effects on results. We discuss the lessons concerning surrogates evaluation emerging from our investigations, calling for better provision in such studies of the background information that can allow (i) critical examination of evidence (both at the initial corroboration and re-evaluation stages), and (ii) greater synthesis of lessons about the pitfalls of different forms of evidence in different contexts. [source] Prevalence of myofascial temporomandibular disorder in US community womenJOURNAL OF ORAL REHABILITATION, Issue 11 2008M. N. JANAL Summary, This study estimates the prevalence of the myofascial subtype of temporomandibular disorders (M-TMD) defined by Research Diagnostic Criteria (RDC), and relates that prevalence to the surveyed report of facial pain. From among 20 000 women selected at random in the NY metropolitan area who completed a telephone survey of facial pain, 2000 were invited for an RDC/TMD examination; 782 examinations were completed. Prevalence was estimated in analyses that were weighted to correct sampling biases. Differences among demographic strata were evaluated with logistic regression. The prevalence of M-TMD was estimated to be 10·5% (95% CL = 8·5,13·0%). Prevalence was significantly higher among younger women, among women of lower socio-economic status, among Black women, and among non-Hispanic women. The report of facial pain in the telephone survey (10·1%) had high specificity for M-TMD diagnosis (94·7%), but low sensitivity (42·7%). M-TMD is a fairly common disorder among American women. Among those reporting facial pain during the last month, half met RDC palpation criteria for M-TMD; thus, a formal physical examination is imperative to establish this diagnosis. Prevalence varies with age, socio-economic status, race and Hispanic ethnicity. A substantial number of RDC-diagnosed cases of M-TMD did not report facial pain in the survey; the reason for this requires further study. [source] Pacific walrus (Odobenus rosmarus divergens): Differential prey digestion and dietMARINE MAMMAL SCIENCE, Issue 4 2009Gay Sheffield Abstract Stomach content data from 798 Pacific walruses (Odobenus rosmarus divergens) collected during 1952,1991 were analyzed using a method that evaluates the stage of digestion of prey remains. Non-molluscan prey taxa were not well represented in previous interpretations of walrus diet due to digestion biases. Stomach contents least affected by digestion (fresh stomachs) contained more prey taxa than stomachs of an unknown or more digested state. Bivalves, gastropods, and polychaete worms were the most frequent prey items in both the Bering and Chukchi seas, although bivalves occurred more frequently in stomachs from the Bering Sea and gastropods occurred more frequently in stomachs from the Chukchi Sea. Male and female walruses consumed essentially the same prey when in the same location. Using only fresh stomachs collected between 1975 and 1985, there was no significant difference between the proportion that contained mostly bivalves and the proportion that contained non-bivalve prey items. Earlier interpretations of a change in walrus diet in this period compared to the prior two decades may have been due to digestion as well as sampling biases. Current climatic changes may affect walrus's access to diverse, productive shallow water feeding areas. [source] An investigation of the behavior of Cu and Cr during iron meteorite crystallizationMETEORITICS & PLANETARY SCIENCE, Issue 4 2009Nancy L. CHABOT To investigate the origin of Cu and Cr concentrations observed in these meteorites, a thorough set of solid metal/liquid metal experiments were conducted in the Fe-Ni-S system. In addition to Cu and Cr, partitioning values were also determined for As, Au, Bi, Co, Mo, Ni, Pb, Rh, Ru, Sb, Sn, V, and Zn from the experiments. Experimental results for Cu and Cr showed similar chalcophile partitioning behavior, whereas these elements have differently sloped trends within magmatic iron meteorite groups. Thus, fractional crystallization alone cannot control both the Cu and Cr concentrations in these iron meteorite groups. A simple fractional crystallization model based on our experimental Cu partitioning results was able to match the Cu versus Au trend observed in the S-poor IVB iron meteorite group but not the decreasing Cu versus Au trends in the IIAB and IIIAB groups or the unique S-shaped Cu versus Au trend in the IVA group. However, the crystallization model calculations were found to be very sensitive to the specific choice for the mathematical expression of D(Cu), suggesting that any future refinement of the parameterization of D(Cu) should include a reassessment of the Cu fractional crystallization trends. The Cr versus Au trends in magmatic iron meteorite groups are steeper than those of Cu and not explained by fractional crystallization. Other influences, such as the removal of chromite from the crystallizing system or sampling biases during iron meteorite compositional analyses, are likely responsible for the Cr trends in magmatic iron meteorite groups. [source] | ||||||||||