scholarly journals An examination of species limits in theAulacorhynchus“prasinus” toucanet complex (Aves: Ramphastidae)

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2381 ◽  
Author(s):  
Kevin Winker
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
South America ◽  
Multivariate Analyses ◽  
Biological Species ◽  
Past Century ◽  
Social Selection ◽  
Species Limits ◽  
Color Changes ◽  
The Past

The number of species recognized inAulacorhynchustoucanets has varied tremendously over the past century. Revisors seem to disagree on whether head and bill coloration are useful indicators of species limits, especially in theA.“prasinus” complex. Using morphometrics, I tested the hypothesis that the major color-based subspecific groups ofA.“prasinus”sensu latoare simply “cookie-cutter” (i.e., morphologically nearly identical) toucanets with different head and bill colorations. Univariate and multivariate analyses show that they are not simply morphological replicates of different colors: a complex array of morphometric similarities and dissimilarities occur between the major subspecific groups, and these variations differ between the sexes. Latitude and longitude had a small but significant association with female (but not male) PC1 and PC2. Hybridization and intergradation were also considered using plumage and bill characters as a surrogate to infer gene flow. Hybridization as indicated by phenotype appears to be substantial betweenA. “p.” cyanolaemusandA. “p.” atrogularisand nonexistent between other major groups, although from genetic evidence it is likely rare betweenA. “p.” albivittaandA. “p.” cyanolaemus. The congruence and complexities of the morphological and color changes occurring among these groups suggest that ecological adaptation (through natural selection) and social selection have co-occurred among these groups and that species limits are involved. Further, hybridization is not evident at key places, despite in many cases (hypothetical) opportunity for gene flow. Consequently, I recommend that this complex be recognized as comprising five biological species:A. wagleri, prasinus, caeruleogularis, albivitta,andatrogularis. Four of these also have valid subspecies within them, and additional work may eventually support elevation of some of these subspecies to full species. Species limits in South America especially need more study.

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life

2010 ◽  
Author(s):  
Charles Darwin
Keyword(s):  
Natural Selection ◽  
South America ◽  
Origin Of Species ◽  
The Past

Introduction When on board H.M.S. ‘Beagle,’ as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me...

Age at marriage and family size: social causation and social selection hypotheses

1972 ◽  
Vol 4 (1) ◽  
pp. 117-134 ◽  
Author(s):  
Joan Busfield
Keyword(s):  
Great Britain ◽  
Family Size ◽  
Married Women ◽  
Negative Association ◽  
Past Century ◽  
Social Selection ◽  
Marriage And Family ◽  
Age At Marriage ◽  
The Past ◽  
Recent Group

The familiar and well-established negative association between a woman's age at marriage and family size has received somewhat less attention in recent years. No doubt this is because, with the reduction in fertility of the past century, the observed differentials appear less striking and seem less significant. Age at marriage is a less obvious determinant of family size than in the past. Glass & Grebenik (1954), commenting on the data produced by the 1946 Family Census, emphasized the decreasing importance of the association both absolutely and relatively. Contrasting the completed fertility of the 1900–09 and the 1925 marriage cohorts in Great Britain (Table 1), they argued that, though for all, married women the relative influence of age at marriage was unchanged, the figures for fertile marriages only (those where the wife had at least one child) appeared to indicate ‘that age at marriage and fertility were not quite so tightly linked for the more recent group’. And they added ‘this is the kind of development which would be expected with the increasing spread of family planning’.

Animal Altruism and Co-Operation: A Selected Bibliography

1974 ◽  
Vol 35 (3) ◽  
pp. 1171-1174 ◽  
Author(s):  
Susan Robinson ◽  
R. John Huber
Keyword(s):  
Natural Selection ◽  
Animal Behavior ◽  
Past Century ◽  
Mutual Aid ◽  
The Past ◽  
Survival Of The Fittest

Darwin's and Spencer's respective doctrines of “natural selection” and “survival of the fittest” have influenced psychologists' research for the past century. That is, there has been a substantial amount of research devoted to aggression and competition, while little research has been undertaken concerning co-operation and altruism. Both Darwin and Spencer, however, felt that species capable of co-operation, mutual aid, and altruism would be favored by natural selection. Thus, according to Darwinian-Spencerian theory altruism is a logical axis for the study of animal behavior. To that end, a bibliography listing studies concerning the development and maintenance of altruistic and co-operative behavior in animals is offered.

scholarly journals An overview of speciation and species limits in birds

The Auk ◽  
2021 ◽  
Author(s):  
Kevin Winker
Keyword(s):  
Gene Flow ◽  
Integrative Taxonomy ◽  
Difficult Problem ◽  
Biological Species ◽  
Biological Species Concept ◽  
Species Limits ◽  
Main Driver ◽  
Data Signal ◽  
Clear Line ◽  
Silver Bullet

Abstract Accurately determining avian species limits has been a challenge and a work in progress for most of a century. It is a fascinating but difficult problem. Under the biological species concept, only lineages that remain essentially independent when they are in sympatry are clearly species. Otherwise, there is no clear line yet found that marks when a pair of diverging lineages (e.g., in allopatry) become different enough to warrant full biological species status. Also, with more data, species limits often require reevaluation. The process of divergence and speciation is itself very complex and is the focus of intense research. Translating what we understand of that process into taxonomic names can be challenging. A series of issues are important. Single-locus criteria are unlikely to be convincing. Genetic independence is not a species limits requirement, but the degree of independence (gene flow) needs to be considered when there is opportunity for gene flow and independence is not complete. Time-based species (limits determined by time of separation) are unsatisfactory, though integrating time more effectively into our datasets is warranted. We need to disentangle data signal due to neutral processes vs. selection and prioritize the latter as the main driver of speciation. Assortative mating is also not likely to be an adequate criterion for determining species limits. Hybridization and gene flow are more important than ever, and there is a condition not being treated evenly in taxonomy: evolutionary trysts of 2 or more lineages stuck together through gene flow just short of speciation over long periods. Comparative methods that use what occurs between good species in contact to infer species limits among allopatric forms remain the gold standard, but they can be inaccurate and controversial. Species-level taxonomy in birds is likely to remain unsettled for some time. While the study of avian speciation has never been more exciting and dynamic, there is no silver bullet for species delimitation, nor is it likely that there will ever be one. Careful work using integrative taxonomy in a comparative framework is the most promising way forward.

Similar Holocene glaciation histories in tropical South America and Africa

Geology ◽  
2020 ◽  
Author(s):  
Anthony C. Vickers ◽  
Jeremy D. Shakun ◽  
Brent M. Goehring ◽  
Andrew Gorin, ◽  
Meredith A. Kelly ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
Past Century ◽  
Tropical Glaciers ◽  
The Past ◽  
Ice Cap ◽  
Ice Retreat ◽  
Quelccaya Ice Cap ◽  
The Tropics

Tropical glaciers have retreated alongside warming temperatures over the past century, yet the way in which these trends fit into a long-term geological context is largely unclear. Here, we present reconstructions of Holocene glacier extents relative to today from the Quelccaya ice cap (Peru) and the Rwenzori Mountains (Uganda) based on measurements of in situ14C and 10Be from recently exposed bedrock. Ice-extent histories are similar at both sites and suggest that ice was generally smaller than today during the first half of the Holocene and larger than today for most, if not all, of the past several millennia. The similar glaciation history in South America and Africa suggests that large-scale warming followed by cooling of the tropics during the late Holocene primarily drove ice extent, rather than regional changes in precipitation. Our results also imply that recent tropical ice retreat is anomalous in a multimillennial context.

Serrated Tussock (Nassella trichotoma) in the United States

1993 ◽  
Vol 7 (2) ◽  
pp. 525-528 ◽  
Author(s):  
Randy G. Westbrooks ◽  
Gene Cross
Keyword(s):  
United States ◽  
South Africa ◽  
New Zealand ◽  
South America ◽  
The United States ◽  
Past Century ◽  
Cool Season ◽  
The Past ◽  
The United Kingdom ◽  
Cool Season Grass

Serrated tussock [(Nassella trichotoma (Nees) Hack. # STDTR] is a clump-forming, perennial, cool season grass. It is native to South America, where it occurs in Argentina, Brazil, Chile, Peru, and Uruguay. In the past century, it has been introduced to New Zealand, Australia and South Africa, and also occurs in small acreages in France, Italy, and the United Kingdom. Serrated tussock occurs in fields, wastelands, and pastures, but rarely in wet or shaded areas.

World Distribution of Brook Trout, Salvelinus fontinalis

1969 ◽  
Vol 26 (7) ◽  
pp. 1699-1725 ◽  
Author(s):  
Hugh R. MacCrimmon ◽  
J. Scott Campbell
Keyword(s):  
South America ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
Geographic Range ◽  
Past Century ◽  
Western North America ◽  
Single Factor ◽  
The Past ◽  
Spawning Areas ◽  
World Distribution

During the past century, the endemic range of the brook trout, Salvelinus fontinalis (Mitchill), has been extended to include western North America and the continents of Europe, Asia, Africa, and South America. Water temperature appears to be the most important single factor limiting the geographic range, but adequate precipitation and suitable spawning areas are necessary also for the establishment of self-sustaining populations. It is improbable that, with the possible exception of Asia, the present range of the brook trout will be greatly extended through further attempts at introduction.

The zoonotic potential of bat-borne coronaviruses

2020 ◽  
Vol 4 (4) ◽  
pp. 365-381
Author(s):  
Ny Anjara Fifi Ravelomanantsoa ◽  
Sarah Guth ◽  
Angelo Andrianiaina ◽  
Santino Andry ◽  
Anecia Gentles ◽  
...  
Keyword(s):  
Genetic Material ◽  
Field Research ◽  
Sympatric Species ◽  
Animal Origin ◽  
Mammalian Host ◽  
Past Century ◽  
The Past ◽  
Novel Host ◽  
Horseshoe Bat ◽  
Human Infections

Seven zoonoses — human infections of animal origin — have emerged from the Coronaviridae family in the past century, including three viruses responsible for significant human mortality (SARS-CoV, MERS-CoV, and SARS-CoV-2) in the past twenty years alone. These three viruses, in addition to two older CoV zoonoses (HCoV-229E and HCoV-NL63) are believed to be originally derived from wild bat reservoir species. We review the molecular biology of the bat-derived Alpha- and Betacoronavirus genera, highlighting features that contribute to their potential for cross-species emergence, including the use of well-conserved mammalian host cell machinery for cell entry and a unique capacity for adaptation to novel host environments after host switching. The adaptive capacity of coronaviruses largely results from their large genomes, which reduce the risk of deleterious mutational errors and facilitate range-expanding recombination events by offering heightened redundancy in essential genetic material. Large CoV genomes are made possible by the unique proofreading capacity encoded for their RNA-dependent polymerase. We find that bat-borne SARS-related coronaviruses in the subgenus Sarbecovirus, the source clade for SARS-CoV and SARS-CoV-2, present a particularly poignant pandemic threat, due to the extraordinary viral genetic diversity represented among several sympatric species of their horseshoe bat hosts. To date, Sarbecovirus surveillance has been almost entirely restricted to China. More vigorous field research efforts tracking the circulation of Sarbecoviruses specifically and Betacoronaviruses more generally is needed across a broader global range if we are to avoid future repeats of the COVID-19 pandemic.

PCSK9 inhibition for LDL lowering and beyond – implications for patients with peripheral artery disease

VASA ◽  
2018 ◽  
Vol 47 (3) ◽  
pp. 165-176 ◽  
Author(s):  
Katrin Gebauer ◽  
Holger Reinecke
Keyword(s):  
Cardiovascular Risk ◽  
Risk Reduction ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Past Century ◽  
Pcsk9 Inhibitors ◽  
Cardiovascular Risk Reduction ◽  
Simultaneous Application ◽  
The Past ◽  
Pcsk9 Inhibition

Abstract. Low-density lipoprotein cholesterol (LDL-C) has been proven to be a causal factor of atherosclerosis and, along with other triggers like inflammation, the most frequent reason for peripheral arterial disease. Moreover, a linear correlation between LDL-C concentration and cardiovascular outcome in high-risk patients could be established during the past century. After the development of statins, numerous randomized trials have shown the superiority for LDL-C reduction and hence the decrease in cardiovascular outcomes including mortality. Over the past decades it became evident that more intense LDL-C lowering, by either the use of highly potent statin supplements or by additional cholesterol absorption inhibitor application, accounted for an even more profound cardiovascular risk reduction. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a serin protease with effect on the LDL receptor cycle leading to its degradation and therefore preventing continuing LDL-C clearance from the blood, is the target of a newly developed monoclonal antibody facilitating astounding LDL-C reduction far below to what has been set as target level by recent ESC/EAS guidelines in management of dyslipidaemias. Large randomized outcome trials including subjects with PAD so far have been able to prove significant and even more intense cardiovascular risk reduction via further LDL-C debasement on top of high-intensity statin medication. Another approach for LDL-C reduction is a silencing interfering RNA muting the translation of PCSK9 intracellularly. Moreover, PCSK9 concentrations are elevated in cells involved in plaque composition, so the potency of intracellular PCSK9 inhibition and therefore prevention or reversal of plaques may provide this mechanism of action on PCSK9 with additional beneficial effects on cells involved in plaque formation. Thus, simultaneous application of statins and PCSK9 inhibitors promise to reduce cardiovascular event burden by both LDL-C reduction and pleiotropic effects of both agents.

Archaeology in the Past Century

1901 ◽  
Vol 51 (1309supp) ◽  
pp. 20976-20977
Author(s):  
W. M. Flinders Petrje
Keyword(s):  
Past Century ◽  
The Past
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