scholarly journals Potential evolutionary body size reduction in a Malagasy primate (Propithecus verreauxi) in response to human size-selective hunting pressure

2020 ◽  
Author(s):  
Alexis P. Sullivan ◽  
Laurie R. Godfrey ◽  
Richard R. Lawler ◽  
Heritiana Randrianatoandro ◽  
Laurie Eccles ◽  
...  
Keyword(s):  
Permutation Test ◽  
Evolutionary Change ◽  
Size Difference ◽  
Single Element ◽  
Before Present ◽  
Propithecus Verreauxi ◽  
Hunting Pressure ◽  
Living Species ◽  
Scan Data ◽  
Early Human

ABSTRACTThe Holocene arrival of humans on Madagascar precipitated major changes to the island’s biodiversity. The now-extinct, endemic “subfossil” megafauna of Madagascar were likely hunted by the island’s early human inhabitants. Perhaps in part due to preferential hunting of larger prey, no surviving species on Madagascar is larger than 10 kg. Outside of Madagascar, size-selective hunting pressure has resulted in the phyletic dwarfism of many still-living species across a diversity of phyla. On Madagascar, some subfossil bones of extant lemurs are considerably larger than those of the modern members of their species, but relatively large distances between the subfossil localities and modern samples that have been compared to date makes it impossible to reject the possibility that these size differences more simply reflect pre-existing ecogeographic variation. Here, we used high-resolution 3D scan data to conduct comparative morphological analyses of subfossil and modern skeletal remains of one of the larger extant lemurs, Verreaux’s sifakas (Propithecus verreauxi) from subfossil and modern sites ∼10 km adjacent: Taolambiby (bones dated to 725-560 – 1075-955 cal. years before present) and Beza Mahafaly Special Reserve, respectively. We found that the average subfossil sifaka bone (n=12) is 9% and significantly larger than that of modern sifakas (n=31 individuals; permutation test; p=0.037). When restricting the analysis to the single element and side with the largest representation in the subfossil sample (n=4 right distal femora), the average subfossil bone is 10% larger (p=0.046). While we cannot yet conclude whether this size difference reflects evolutionary change or an archaeological aggregation/taphonomic process, if this is a case of phyletic dwarfism in response to human size-selective harvesting pressures then the estimated rate of evolutionary change is slightly higher than that previously calculated for other archaeological cases of this phenomenon.

Chronospecies' longevities, the origin of genera, and the punctuational model of evolution

Paleobiology ◽  
1978 ◽  
Vol 4 (1) ◽  
pp. 26-40 ◽  
Author(s):  
Steven M. Stanley
Keyword(s):  
Mass Extinction ◽  
Distinct Species ◽  
Evolutionary Change ◽  
Late Cenozoic ◽  
Bottleneck Effect ◽  
Survivorship Curve ◽  
Higher Taxa ◽  
As Species ◽  
Living Species ◽  
Evolutionary Lineages

Taxonomists working with late Cenozoic faunas tend to view living species as starting points for the evaluation of chronospecies (i.e., segments of evolutionary lineages subjectively designated as species) that extend backward in time from the Recent. This practice makes it possible to construct a survivorship curve for late Cenozoic chronospecies by evaluating all fossil lineages believed to have survived to the present day. A survivorship curve is produced by plotting the fraction of these lineages existing at any time that have not undergone enough phyletic evolution that their extant representatives are assigned to new species. This kind of surviviorship curve has been plotted for chronospecies of mammals using the beginning of the Würm, rather than the Recent, as an endpoint in order to avoid the effects of the Würm and post-Würm mass extinction. The survivorship curve reveals that all but a small fraction of established chronospecies have long durations relative to intervals of time during which distinctive higher taxa have arisen. Phyletic turnover of species has been remarkably slow. Most net evolutionary change must have been associated with saltational speciation. Even the large majority of genera must have arisen rapidly by one or more divergent speciation events. Estimates of rates of extinction suggest that the bottleneck effect, in which constriction of a lineage is followed by re-expansion as a distinct species, cannot be a major source of evolutionary change. These conclusions, based on the evaluation of mammalian phylogeny, seem also to apply to other taxa of animals, supporting the punctuational model of evolution. The long durations of hominid species imply that the evolution of humans, like that of other mammals, conforms to this model.

scholarly journals Allan Charles Wilson. 18 October 1934 — 21 July 1991

2014 ◽  
Vol 60 ◽  
pp. 455-473 ◽  
Author(s):  
Rebecca L. Cann
Keyword(s):  
New Zealand ◽  
Molecular Evolution ◽  
Doctoral Students ◽  
Molecular Clock ◽  
Evolutionary Biology ◽  
Evolutionary Change ◽  
Left Behind ◽  
The Usa ◽  
Living Species ◽  
The University

Allan Charles Wilson was born on 18 October 1934 at Ngaruawahia, New Zealand. He died in Seattle, Washington, on 21 July 1991 while undergoing treatment for leukaemia. Allan was known as a pioneering and highly innovative biochemist, helping to define the field of molecular evolution and establish the use of a molecular clock to measure evolutionary change between living species. The molecular clock, a method of measuring the timescale of evolutionary change between two organisms on the basis of the number of mutations that they have accumulated since last sharing a common genetic ancestor, was an idea initially championed by Émile Zuckerkandl and Linus Pauling (Zuckerkandl & Pauling 1962), on the basis of their observations that the number of changes in an amino acid sequence was roughly linear with time in the aligned haemoglobin proteins of animals. Although it is now not unusual to see the words ‘molecular evolution’ and ‘molecular phylogeny’ together, when Allan formed his own biochemistry laboratory in 1964 at the University of California, Berkeley, many scientists in the field of evolutionary biology considered these ideas complete heresy. Allan’s death at the relatively young age of 56 years left behind his wife, Leona (deceased in 2009), a daughter, Ruth (b. 1961), and a son, David (b. 1964), as well his as mother, Eunice (deceased in 2002), a younger brother, Gary Wilson, and a sister, Colleen Macmillan, along with numerous nieces, nephews and cousins in New Zealand, Australia and the USA. In this short span of time, he trained more than 55 doctoral students and helped launch the careers of numerous postdoctoral fellows.

A standard for transmission electron spectroscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 530-531 ◽  
Author(s):  
Dennis Maher ◽  
David Joy ◽  
Peggy Mochel
Keyword(s):  
Thin Films ◽  
Electron Spectroscopy ◽  
Host Lattice ◽  
Single Element ◽  
Multicomponent Systems ◽  
Transmission Electron ◽  
Major Interest ◽  
Standard Specimens ◽  
Forms Of Carbon ◽  
Electron Energy Loss

A variety of standard specimens is needed in order to systematically investigate the instrumentation, specimen, data reduction and quantitation variables in electron energy-loss spectroscopy (EELS). Pure single element specimens (e.g. various forms of carbon) have received considerable attention to date but certain elements of interest cannot be prepared directly as thin films. Since studies of the first and second row elements in two- or multicomponent systems will be of considerable importance in microanalysis using EELS, there is a need for convenient standards containing these species. For many investigations a standard should contain the desired element, or elements, homogeneously dispersed through a suitable matrix and at an accurately known concentration. These conditions may be met by the technique of implantation.Silicon was chosen as the host lattice since its principal ionization energies, EL23 = 98 eV and Ek = 1843 eV, are well removed from the K-edges of most elements of major interest such as boron (Ek = 188 eV), carbon (Ek = 283 eV), nitrogen (Ek = 400 eV) and oxygen (Ek = 532 eV).

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

THE ULTRASTRUCTURE OF THE HUMAN GRANULOSAL LUTEIN CELL OF THE FIRST TRIMESTER OF GESTATION

1968 ◽  
Vol 58 (3) ◽  
pp. 481-496 ◽  
Author(s):  
Poul Hjortkjær Pedersen ◽  
Jørgen Falck Larsen
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
First Trimester ◽  
Corpora Lutea ◽  
Steroid Synthesis ◽  
Intracellular Location ◽  
Human Pregnancy ◽  
Subendothelial Space ◽  
Lutein Cell ◽  
Early Human

ABSTRACT The ultrastructure of granulosal lutein cells of 13 corpora lutea in early human pregnancy was studied. The predominant cytoplasmic element was the smooth endoplasmic reticulum. No convincing signs of degeneration of the lutein cells could be demonstrated within the first 14 weeks of pregnancy, as the mitochondria as well as the rough and smooth endoplasmic reticulum were well preserved. However, lysosomes may be slightly more numerous in older specimens and the subendothelial space increases with the age of gestation. A particular type of multilaminated structure one to five micron in diameter was observed, particularly in the earliest specimens. The possible intracellular location of steroid synthesis is discussed.

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