Models for Pleistocene Extinction

1981 ◽  
Vol 2 (2) ◽  
pp. 85-100 ◽  
Author(s):  
Kit W. Wesler
Keyword(s):  
Computer Simulation ◽  
North America ◽  
South America ◽  
Late Pleistocene ◽  
Environmental Changes ◽  
Alternative Formulation

Arguments for Paleoindian overkill of Late Pleistocene megafauna have traditionally emphasized North America with little more than token reference to other areas. Other scholars reject human causation of Pleistocene extinctions, preferring to see in climatic and environmental changes a sufficient explanation for the losses of these forms. This paper discusses the idea of overkill with reference to a computer simulation by Mosimann and Martin (1975), and offers reasons for preferring an alternative formulation. It is also suggested that the case of South America should be reviewed separately, and that an environmental explanation of Pleistocene extinction may be more suitable there.

Mammalian faunal dynamics of the great American interchange

Paleobiology ◽  
1976 ◽  
Vol 2 (3) ◽  
pp. 220-234 ◽  
Author(s):  
S. David Webb
Keyword(s):  
North America ◽  
South America ◽  
Late Pleistocene ◽  
Turnover Rate ◽  
Marked Decrease ◽  
Important Change ◽  
South American ◽  
The Family ◽  
Family Level ◽  
Land Mammal

The American interchange of land mammals reached its acme during the late Blancan and early Irvingtonian in North America and during the Chapadmalalan and Uquian in South America. It lasted about two million years and included taxa adapted to diverse habitats. It was preceded in the early Hemphillian in North America and the Huayquerian in South America by the interchange of a few heralding genera. The MacArthur-Wilson faunal equilibrium hypothesis correctly predicts a marked increase in originations, number of genera, and turnover rate for the South American fauna during the peak of the interchange. Subsequent further increases were not so predicted but closely resemble patterns also observed in late Pleistocene land mammals of Europe and North America. The continued increase in South American land mammal genera after the interchange had largely ceased resulted principally from autochthonous evolution of northern immigrant stocks. A marked decrease in South American ungulate genera (from thirteen to three) coincided with the appearance of fourteen northern ungulate genera and therefore appears to be a replacement phenomenon. The area/diversity relationship predicts no important change in generic diversity if a maximum of only nine percent of North America is occupied by the interamerican mingled fauna. At the family level, however, diversity is seriously overestimated due to the nomenclatural artifact of increased relative diversity by filtering.

Effects of insecticides on adults and eggs of Drosophila suzukii (Diptera, Drosophilidae)

2017 ◽  
Vol 43 (2) ◽  
pp. 208 ◽  
Author(s):  
Daniele Cristine Hoffmann Schlesener ◽  
Jutiane Wollmann ◽  
Juliano De Bastos Pazini ◽  
Anderson Dionei Grützmacher ◽  
Flávio Roberto Mello Garcia
Keyword(s):  
North America ◽  
South America ◽  
Chemical Control ◽  
Stone Fruits ◽  
Drosophila Suzukii ◽  
Ovicidal Effect ◽  
Mere Presence ◽  
South Of Brazil ◽  
Different Cultures ◽  
First Time

Drosophila suzukii (Diptera, Drosophilidae) is an exotic species, endemic to Asia and currently a pest to small and stone fruits in several countries of North America and Europe. It was detected in 2013 for the first time in South America, in the south of Brazil. Unlike most drosophilids, this species deserves special attention, because the females are capable of oviposit inside healthy fruits, rendering their sale and export prohibited. Despite the confirmed existence of this species in different states of Brazil, this insect is yet been to be given the pest status. Nevertheless, the mere presence of this species is enough to cause concern to producers of small fruits and to justify further investigation for it’s control, especially chemical control for a possible change in status. Therefore, the goal of this work was to evaluate, in laboratory, mortality of D. suzukii adults and ovicidal effect when exposed to different insecticides registered for species of the Tephritidae and Agromyzidae families in different cultures. The insecticides deltamethrin, dimethoate, spinosad, fenitrothion, phosmet, malathion, methidathion, and zeta-cypermethrin resulted in mortality to 100 % of the subjects three days after the treatment (DAT). Regarding the effects over eggs, it was  established that the insecticides fenitrothion, malathion, and methidathion deemed 100 % of the eggs not viable, followed by phosmet and diflubenzuron, which also caused elevated reduction in the eclosion of larvae two DAT.

Species distribution modeling reveals the ecological niche of extinct megafauna from South America

2021 ◽  
pp. 1-8
Author(s):  
Thaísa Araújo ◽  
Helena Machado ◽  
Dimila Mothé ◽  
Leonardo dos Santos Avilla
Keyword(s):  
South America ◽  
Species Distribution ◽  
Environmental Changes ◽  
Species Distribution Modeling ◽  
Human Action ◽  
Northeastern Brazil ◽  
Climate Conditions ◽  
Middle Holocene ◽  
Distribution Modeling ◽  
The Impact

Abstract Climatic and environmental changes, as well as human action, have been cited as potential causes for the extinction of megafauna in South America at the end of the Pleistocene. Among megamammals lineages with Holarctic origin, only horses and proboscideans went extinct in South America during this period. This study aims to understand how the spatial extent of habitats suitable for Equus neogeus and Notiomastodon platensis changed between the last glacial maximum (LGM) and the middle Holocene in order to determine the impact that climatic and environmental changes had on these taxa. We used species distribution modeling to estimate their potential extent on the continent and found that both species occupied arid and semiarid open lands during the LGM, mainly in the Pampean region of Argentina, southern and northeastern Brazil, and parts of the Andes. However, when climate conditions changed from dry and cold during the LGM to humid and warm during the middle Holocene, the areas suitable for these taxa were reduced dramatically. These results support the hypothesis that climatic changes were a driving cause of extinction of these megamammals in South America, although we cannot rule out the impact of human actions or other potential causes for their extinction.

Climatic implications of latest Pleistocene and earliest Holocene mammalian sympatries in eastern Washington state, USA

2008 ◽  
Vol 70 (3) ◽  
pp. 426-432 ◽  
Author(s):  
R. Lee Lyman
Keyword(s):  
North America ◽  
Late Pleistocene ◽  
Rocky Mountains ◽  
Taxonomic Composition ◽  
Washington State ◽  
The West ◽  
Mammalian Faunas ◽  
Eastern Washington

AbstractFor more than fifty years it has been known that mammalian faunas of late-Pleistocene age are taxonomically unique and lack modern analogs. It has long been thought that nonanalog mammalian faunas are limited in North America to areas east of the Rocky Mountains and that late-Pleistocene mammalian faunas in the west were modern in taxonomic composition. A late-Pleistocene fauna from Marmes Rockshelter in southeastern Washington State has no modern analog and defines an area of maximum sympatry that indicates significantly cooler summers than are found in the area today. An earliest Holocene fauna from Marmes Rockshelter defines an area of maximum sympatry, including the site area, but contains a single tentatively identified taxon that may indicate slightly cooler than modern summers.

BIOSYSTEMATIC STUDIES ON XANTHIUM: TAXONOMIC APPRAISAL AND ECOLOGICAL STATUS

1959 ◽  
Vol 37 (2) ◽  
pp. 173-208 ◽  
Author(s):  
Doris Löve ◽  
Pierre Dansereau
Keyword(s):  
North America ◽  
South America ◽  
Ecological Status ◽  
Distinct Species ◽  
Eastern North America ◽  
Flowering Response ◽  
Short Day ◽  
Stable Species ◽  
Enormous Variation

The following paper is an evaluation of the taxonomic and ecological status of the genus Xanthium L. A review of its systematics demonstrates that many so-called "species" described on material from Europe actually have their origin in America, except one, X. strumarium s. str., which seems to have a Mediterranean–European center of dispersal. Another conclusion drawn is that Xanthium consists of only two distinct species: X. spinosum L. and X. strumarium L. The former is a relatively stable species, the latter an enormously variable one readily subdivided into a number of minor taxonomic entities.Ecologically, in eastern North America at least, Xanthium is primarily a beach plant, which prefers open habitats and succumbs to crowding. The seeds are most often dispersed by water and wind. It enters easily into ruderal habitats, but only as long as these are open and unshaded.The generalized short-day flowering response in this genus supports our hypothesis that Xanthium has a tropical–subtropical origin, and we feel that it has its center in Central and/or South America, whence it has spread over the continents north and southward.There is no evidence for any sterility barriers separating the entities of X. strumarium, but we feel that an intense inbreeding with an occasional outbreeding is responsible for the enormous variation, often resulting in small, local, but unstable taxa.

A Carved Stone from D'Arcy, Saskatchewan

1940 ◽  
Vol 5 (4) ◽  
pp. 334-335
Author(s):  
Vladimar Alfred Vigfusson
Keyword(s):  
North America ◽  
Late Pleistocene ◽  
Glacial Lake ◽  
Bering Strait ◽  
The North ◽  
Gravel Pit ◽  
North Bank ◽  
The Town

In recent years, the attention of some archaeologists has been directed to the Canadian Northwest with the expectation of finding some evidence or indication of the early migrations of man on this continent. That man reached North America by Bering Strait from Asia, is generally accepted, but the theory that the migrations took place in late Pleistocene times and by way of an open corridor between the Keewatin ice and the Rockies, requires confirmation. It is significant that Folsom and Yuma points from Saskatchewan, described by E. B. Howard, were found mainly in areas bordering the ancient glacial Lake Regina.As a further contribution to this problem, it seems desirable to present a brief description of a carved stone relic found in gravel in central Saskatchewan about three years ago.The stone was found about seven miles southeast of the town of D'Arcy in a gravel pit located on Sec. 9, Tp. 28, Rge. 18, W. 3rd Meridian, on the north bank of a ravine running east into Bad Lake.

scholarly journals Memoirs of a frequent flier: Phylogenomics reveals 18 long-distance dispersals between North America and South America in the popcorn flowers (Amsinckiinae)

2017 ◽  
Vol 104 (11) ◽  
pp. 1717-1728 ◽  
Author(s):  
C. Matt Guilliams ◽  
Kristen E. Hasenstab-Lehman ◽  
Makenzie E. Mabry ◽  
Michael G. Simpson
Keyword(s):  
North America ◽  
South America ◽  
Long Distance
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