Adaptive characterizations of primates have usually included a reduction in olfactory sensitivity. However, this inference of derivation and directionality assumes an ancestral state of olfaction, ...usually by comparison to a group of extant non-primate mammals. Thus, the accuracy of the inference depends on the assumed ancestral state. Here I present a phylogenetic model of continuous trait evolution that reconstructs olfactory bulb volumes for ancestral nodes of primates and mammal outgroups. Parent-daughter comparisons suggest that, relative to the ancestral euarchontan, the crown-primate node is plesiomorphic and that derived reduction in olfactory sensitivity is an attribute of the haplorhine lineage. The model also suggests a derived increase in olfactory sensitivity at the strepsirrhine node. This oppositional diversification of the strepsirrhine and haplorhine lineages from an intermediate and non-derived ancestor is inconsistent with a characterization of graded reduction through primate evolution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Molecular phylogenetic studies that have included sirenians from the genera
,
, and
have resolved their interrelationships but have yielded divergence age estimates that are problematically ...discordant. The ages of these lineage splits have profound implications for how to interpret the sirenian fossil record-including clade membership, biogeographic patterns, and correlations with Earth history events. In an effort to address these issues, here we present a total evidence phylogenetic analysis of Sirenia that includes living and fossil species and applies Bayesian tip-dating methods to estimate their interrelationships and divergence times. In addition to extant sirenians, our dataset includes 56 fossil species from 106 dated localities and numerous afrotherian outgroup taxa. Genetic, morphological, temporal, and biogeographic data are assessed simultaneously to bring all available evidence to bear on sirenian phylogeny. The resulting time-tree is then used for Bayesian geocoordinates reconstruction analysis, which models ancestral geographic areas at splits throughout the phylogeny, thereby allowing us to infer the direction and timing of dispersals. Our results suggest that Pan-Sirenia arose in North Africa during the latest Paleocene and that the Eocene evolution of stem sirenians was primarily situated in the Tethyan realm. In the late Eocene, some lineages moved into more northern European latitudes, an area that became the source region for a key trans-Atlantic dispersal towards the Caribbean and northern-adjacent west Atlantic. This event led to the phylogenetic and biogeographic founding of crown Sirenia with the Dugongidae-Trichechidae split occurring at the Eocene-Oligocene boundary (~33.9 Ma), temporally coincident with the onset of dropping global sea levels and temperatures. This region became the nexus of sirenian diversification and supported taxonomically-rich dugongid communities until the earliest Pliocene. The Dugonginae-Hydrodamalinae split occurred near Florida during the early Miocene (~21.2 Ma) and was followed by a west-bound dispersal that gave rise to the Pacific hydrodamalines. The late middle Miocene (~12.2 Ma) split of
from all other dugongines also occurred near Florida and our analyses suggest that the Indo-Pacific distribution of modern dugongs is the result of a trans-Pacific dispersal. From at least the early Miocene, trichechid evolution was based entirely in South America, presumably within the Pebas Wetlands System. We infer that the eventual establishment of Amazon drainage into the South Atlantic allowed the dispersal of
out of South America no earlier than the mid-Pliocene. Our analyses provide a new temporal and biogeographic framework for understanding major events in sirenian evolution and their possible relationships to oceanographic and climatic changes. These hypotheses can be further tested with the recovery and integration of new fossil evidence.
In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly ...challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.
The Somali Sengi or Somali Elephant-shrew (
, Macroscelidea, Mammalia) has been considered a "lost species" and is primarily known from about 39 museum specimens, with no new vouchered occurrence ...records since the early 1970s. The scientific literature contains no data concerning living Somali Sengi individuals and the species' current Data Deficient conservation status is attributable to an absence of modern information. Almost everything that has been published about the species is derived from anatomical examinations of historic specimens, gleaned from museum collection notes, or inferred from the known habits and ecology of other sengi taxa. Here we report new evidence that the Somali Sengi
. These data include voucher specimens, georeferenced occurrence localities, body measurements, habitat parameters, and DNA sequences. While the species is historically documented as endemic to Somalia, these new records are from the neighboring Republic of Djibouti and thus expand the Somali Sengi's known range in the Horn of Africa. Furthermore, Djiboutian locality data near international borders suggests that the Somali Sengi is also a current inhabitant of both Somalia and Ethiopia. Criteria that inform conservation status assessments (e.g., suitable habitat contiguity and occurrence in wildlife protected areas) can be positively characterized in Djibouti and therefore bode well for the survival of the Somali Sengi species. New data also inform previously undocumented substrate and sheltering affiliations. DNA analyses indicate that the Somali Sengi is a descendant of the Macroscelidini lineage and therefore reveal that the species' referral to the genus
is incompatible with sengi phylogeny. This taxonomic issue is resolved by recognizing a new genus replacement and recombinant binomial that redesignates the Somali Sengi as
(gen. nov., nov. comb). An analysis of ancestral biogeography suggests that the Somali Sengi has inhabited the Horn of Africa for more than 5.4 million years-and the recognition of the species' phylogenetic ancestry appends the already remarkable biogeographic story of the Macroscelidini tribe.
Diverse lines of geological and geochemical evidence indicate that the Eocene-Oligocene transition (EOT) marked the onset of a global cooling phase, rapid growth of the Antarctic ice sheet, and a ...worldwide drop in sea level. Paleontologists have established that shifts in mammalian community structure in Europe and Asia were broadly coincident with these events, but the potential impact of early Oligocene climate change on the mammalian communities of Afro-Arabia has long been unclear. Here we employ dated phylogenies of multiple endemic Afro-Arabian mammal clades (anomaluroid and hystricognath rodents, anthropoid and strepsirrhine primates, and carnivorous hyaenodonts) to investigate lineage diversification and loss since the early Eocene. These analyses provide evidence for widespread mammalian extinction in the early Oligocene of Afro-Arabia, with almost two-thirds of peak late Eocene diversity lost in these clades by ~30 Ma. Using homology-free dental topographic metrics, we further demonstrate that the loss of Afro-Arabian rodent and primate lineages was associated with a major reduction in molar occlusal topographic disparity, suggesting a correlated loss of dietary diversity. These results raise new questions about the relative importance of global versus local influences in shaping the evolutionary trajectories of Afro-Arabia's endemic mammals during the Oligocene.
Adaptive characterizations of primates have usually included a reduction in olfactory sensitivity. However, this inference of derivation and directionality assumes an ancestral state of olfaction, ...usually by comparison to a group of extant non-primate mammals. Thus, the accuracy of the inference depends on the assumed ancestral state. Here I present a phylogenetic model of continuous trait evolution that reconstructs olfactory bulb volumes for ancestral nodes of primates and mammal outgroups. Parent-daughter comparisons suggest that, relative to the ancestral euarchontan, the crown-primate node is plesiomorphic and that derived reduction in olfactory sensitivity is an attribute of the haplorhine lineage. The model also suggests a derived increase in olfactory sensitivity at the strepsirrhine node. This oppositional diversification of the strepsirrhine and haplorhine lineages from an intermediate and non-derived ancestor is inconsistent with a characterization of graded reduction through primate evolution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The purpose of this dissertation is to reconstruct phylogenies using statistical methods. The focus herein is on rare and/or puzzling placental mammal species – namely Elephantulus revoilii (order ...Macroscelidea), Zenkerella insignis (order Rodentia), and Plesiopithecus teras & Propotto leakeyi (order Primates). These living and fossil taxa are descendants of groups that formed mammalian communities in Paleogene Afro-Arabia. Unlike the mammal groups that arrived in Africa after the landmass became connected to Eurasia, these Paleogene clades evolved together, on “Island Africa”, for nearly two-thirds of the Cenozoic. Thus, the three mammalian lineages addressed here are deeply-rooted in a unique chapter of Afro-Arabian history.The phylogenetic hypotheses generated in this dissertation were inferred from both DNA sequences and morphological character data. I have elected to apply Bayesian methods to these datasets because they are the most sophisticated phylogenetic tools currently available. These phylogenies provide the necessary frameworks against which to evaluate systematic arrangements of respective groups. Results have, in all cases, supported systematic revisions – including a resurrected family and a newly named genus. Additionally, these trees are used in this dissertation to model the chronology of lineage diversifications, to assess the pattern and timing of the evolution of peculiar adaptive traits, and to infer remarkable events of ancestral biogeography. It's my hope that these phylogenies – and the newly generated data from these rarely accessible species – will provide evolutionary context for future comparative studies of their respective lineages.
The News Interview Clayman, Steven; Heritage, John
07/2002, Letnik:
v.Series Number 16
eBook
The news interview has become a major vehicle for presenting broadcast news and political commentary, and a primary interface between the institutions of journalism and government. This much-needed ...work examines the place of the news interview in Anglo-American society and considers its historical development in the United States and Britain. The main body of the book discusses the fundamental norms and conventions that shape conduct in the modern interview. It explores the particular recurrent practices through which journalists balance competing professional norms that encourage both objective and adversarial treatment of public figures. Through analyses of well-known interviews, the book explores the relationship between journalists and public figures and also how, in the face of aggressive questioning, politicians and other public figures struggle to stay 'on message' and pursue their own agendas. This comprehensive and wide-ranging book will be essential reading for students and researchers in sociolinguistics, media and communication studies.
This paper examines two historical trends in practices of questioning deployed across a half-century (1953–2000) of U.S. presidential news conferences (164 conferences, 4608 questions): (1) the ...decline of conventionally indirect question forms, and (2) the rise of negative interrogatives as a polar question format. Both trends show journalists to be exerting increasing pressure on presidents over time but they differ in the nature of that pressure, with the decline of indirectness involving pressure to answer the question at all, and the rise of negative interrogatives involving pressure to answer in a particular way (affirmatively). Both trends have been noted in previous research, but here we take a closer look at how they differ in the pace of change over time, and their varying sensitivity to the exogenous sociopolitical landscape. Among conventionally indirect question frames, contrasting trendlines for “ability” versus “willingness” frames are also examined. All of these language-practice trends span the era of the public questioning of presidents and are thus implicated in mechanisms of governmental accountability.
•In presidential news conferences from 1953–2000, journalists have exerted increasing pressure on presidents.•Conventionally indirect question forms have become less frequent over time, which builds pressure to answer.•Negative interrogatives have grown more frequent over time, which builds pressure to answer in a particular way (affirmatively).•All these language-practice trends are implicated in mechanisms of governmental accountability.
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