The Pleistocene, often referred to as the ice age, is the geological epoch which lasted form 2.6 million to 11,700 years ago. This time era caused a wide variety of systematic differences in the biology and ecology of different mammals and plant taxonomy. This era was characterized by the presence of distinctive large land mammals and birds. There has been at least five major ice ages documented throughout time, but the Pleistocene epoch was the first in where Homo sapiens were evolved and by the end of this era they were documented all throughout the globe. Over the long period of the Pleistocene, there has been cases of genetic biodiversity among many different species causing either extinction or speciation throughout the populations. This is a result of the different glaciation cycles that happened because change of climate from hot to cold, and over hunting caused by humans. Scientist have not proven which factor was a leading contributor but it is documented that both have significant roles in the extinction of plants and animals during this era. The geological change of plants changed the certain habitats that the animals lived in and this would change their environmental processes thus potentially resulting in gene dispersal and different reproduction isolations. It is shown that through the Ice Age, animals either flourished and survived or they either became extinct. This era lost a wide variety fauna and flora throughout the decades that the ice covered the earth. Although this period was 11,000 years ago there are still affects that it has on the different habitats and environments throughout the globe today.
At the time of the Pleistocene, the continents has moved to their current position. At one point in the ice age, all of the continents were covered in ice entirely. The glaciers that covered these land masses were moving, it was documented that the glaciers had periods were they would move and retreat as they thawed and refrozen. Scientists have not been able to pinpoint the reason for this era, but the position of the earth in relation to the sun, composition of the atmosphere and the ocean’s current are believed to be heavy contributors (Malhi). It was during this era that the most recent episodes of cooling took place. Much of the world’s temperate zones were covered with glaciers during cool times and would retreat and unfreeze and repeat the same cycle. Scientists believe that this is could have been one of the key factors to the pleistocene extinctions (Flower). The loss of these different species caused an ecologically depauperate world.
This extinction reduced by more than half of the numbers of large-bodied mammals in the world, including herbivores, predators, and scavengers. In North America alone, 35 genus and 75 species of megafauna went extinct (Pardi). Similar numbers were lost in south america as well. The loss of large consumers from ecological systems, particularly carnivores is a significant modern conservation concern across all ecosystem types. These extinctions are seen to be because of either human predation, environmental change or both.
The pleistocene was characterized by the presence of distinctive large land mammals and birds. There was a wide variety of animals that became extinct after this time period. Such as, the mammoth, mosses, flowering plants, sabertooth tiger, and giant ground sloths. This extinction was not only caused by the ice age but over hunting as well. Although these animals are extinct there are still some around today and they have went through drastic changes not only physical but in their environment as well. Climate changes took place in the late pleistocene, the retreat of ice sheets caused global climate changes and changes throughout the local environments. Some habitats were eliminated while some expanded due to range expansion. Natural selection played a key role here to see where some of the species either thrived or became extinct. (more info here)
The canidae or from the latin word canis meaning “dog” were prevalent during the Pleistocene era. A member of this group is called a canid. This group includes the coyotes, dogs, wolves, and foxes. There is 36 different species in this family and they are found relatively all over the world except for Antarctica in groups (Meachen). Due to their close relationship, domestic dogs, wolves, coyotes can hybridize with each other. Each member of this group all posses 78 chromosomes (Arcadi). Canidae are built for endurance, they are seen to run after prey and to keep a steady speed over long distances. They have survived around human beings for long extended periods of time. The body form of canids are smaller, having long muzzles, teeth adapted for killing, long legs and bushy tails (Meachen).
These animals are very social and they tend to live in small groups and work together to perform certain goals. Canids ranged from deserts, mountains, forests and grasslands. Scientists believed that they would mark their territory with scent marking. All members of the canidae family have life births after a short gestation period lasting 45-55 days long. They can have as many as 15 pops at the same time (Arcadi). The lifespan of a dog varies. Wolves, coyotes, domestic dogs live up to ten years or more. Their diet includes bugs, deer, rodents and snakes and their ability to run up to forty miles per hour helps them catch these certain prey.
The third most abundant carnivore is the Coyote Canis latrans, they have benefited from changes to north american ecosystems. They have also experienced a drastic change to the range of their environment as well (Bozarth). Coyotes provide ecosystem services such as control of populations of rodents, deer, and other animals. After the pleistocene there has been an extinction of large animals such a wolves, mountain lions, and bears and coyotes. Coyotes are seen to be the current apex predator in many ecosystems in North America. Coyotes were only found in the Midwest throughout the pleistocene, today the modern coyote is found all over North America (Gompper). Studies show that coyotes since the pleistocene have lost their larger bodies along with facial features (Bozarth). They also used to have wider teeth for processing meat which was an adaptation for killing large prey.
Modern coyotes range in weight between 15-46 points while the ancient coyotes are estimated to have weighed about 40-46 pounds (Pardi). Pardi describes how the bigger body size of the coyotes had to do with the broader guild of big predators surrounding the land. Once different, larger species became extinct, competition for prey also decreased so coyotes became smaller over time, coyotes were no longer competing against larger wolves thus, going for smaller prey. They changed from large, pack- hunting animals to smaller canines. Although it has been said that this decline in size has been due to climate changes, but it has been due to interactions among species. This picture below shows the skeleton of a Pleistocene coyote. It is a composite from the University of California museum of Paleontology.
Although coyotes changed since the pleistocene, grey wolves, Canis lupus changed in a different way. Todays grey wolf is five to six feet tall, and modern day coyotes measure three to four feet. And instead of weighing about 40 pounds they have reached 120 pounds. Scientist have shown that this could be in result of species interactions or lack thereof. Grey wolves once occupied a habitat stretching from Western Europe across Asia into North America. Wolves have lost a substantial part of their habitat in North America (Vilà). Their genetic diversity has shrunk tremendously. C. lupus lived in Alaska and northwestern Canada (Gompper). They survived the climate and environmental changes, but they no longer roam a large part of North America. They are found across Canada, with small distribution in the U.S. along parts of the Rocky mountains and the Great Lakes. The grey wolf has went under drastic changes in their habitat due to predator control efforts and anthropogenic modification of habitat (Vilà). Their group number has decreased from two-million individuals to about 70,000 individuals. All of these mammals have changed and have geographic barriers because of the climate changes that have affected the growth and distribution of plants.
The plants of the Pleistocene are, in many ways similar to those living today but they have important differences. The fauna and flora types differed from what we see today. The main types of plants were: flowering plants, mosses, conifers, cypress tree, oak trees and prairie grass (Mead). These different plants survived because they did not require large amounts of sunlight or heat. They had the ability to adapt to the shivering temperatures and to lie dormant throughout the ice age. The change in environments in response to the climatic changes disrupted various faunas and floras both in the oceans and on land. This happened closer to the greater ice sheets. During the ice age, certain areas that we know today as the deciduous forests was more of a northern tundra, with a few trees during the different intervals of the glacial deposits retreating. And many grasses and herbs were also present. These climate conditions were very unheard of and not normal compared to what is seen in the modern word. Overall temperatures were significantly lower and seasons did not match up with their typical temperatures. Thus the plants and animals had different geological environments during the glacial times.
At times of glacial periods when vegetation belts were lowered, organisms were allowed to expand their ranges. In the interglacial periods the plants were isolated at disjunction peaks, where differentiation could occur (Vuilleumier). At different times where ice would expand, glacial tongues and lakes would be barriers to gene exchange, on the other hand where warm interglacial times, dry river valleys were a major barrier to the interbreeding of different populations from different mountains (Vuilleumier). Changes in the North Atlantic ocean were most dramatic because of the influence of the ice sheets throughout this era. Scientists were able to track this change in plants because pollen could be found in mummified dung stones. It was unlikely that the plants would grow in one spot relatively close to one another. Mammoths would move from spot to spot and this could initially transfer the different seeds or pollen to then continue the growth of different plants throughout North America at the time (Valkenburgh). Species of warm and dry habitats coexisted with species of cold and humid habitats resulting in plant community and a rich biodiversity (Bressan).
The main reason of climate fluctuations is because of the glacial-interglacial or warm and cold cycles. Both of these cycles happened at weird intervals and tended to cause some sort of chaos (Hofreiter). The speed that these different periods happened was something unheard of. For example, the glaciers covered large parts of North America and the large amounts of water bound in glaciers also resulted in sea levels being up to 120 m which is lower than today. This massive climatic and environmental changes, like stated before, influenced the genetic diversity of plants and animals (Hofreiter). One would think that during colder times, arctic species would expand their distribution more southwards.Instead they colonized the interglacial parts of North America. This can be referred to as the ‘refugium theory’ this explains that during the colder times of the Pleistocene, the ranges of high-elevation species in unglaciated areas expanded to increase gene flow among previously isolated populations (Crespi). It is expected to see genetic diversity decrease from the south to the north. By analysis of the fossil record and by sequencing ancient DNA from the remains to be able to see the genetic diversity of different species. Due to these changes with the increased snow cover in high latitude areas would cause extreme cooling. This lead to a defensive mechanism which would be the decreased carbon dioxide content in the atmosphere during the times of glaciation.
Just as the great herbivore heards disappeared throughout the pleistocene, so did the northern grasslands that they inhabited. Grasses use water resources more rapidly than trees, cactuses and thorns. When the grass numbers reaches a certain level, herbivores eat and trample all the grassland vegetation produced. In the Pleistocene era, the grassland ecosystems occupied half of the worlds land. Homo species occupied these land masses and would leave pieces of them to show that they had presence in this area (Mead). They ended up playing a distinct role in ecosystem being terminated. Another explanation of the disappearance of grasslands throughout this time is because the cold climates would change into a humid one turning the grasslands into muddy mossy tundra. This then would result in the loss of landscape.
Plant disappearance also accounts for landscape loss. Vast amounts of water due to climate change were sucked up into the ground which then resulted in dry conditions. In the mammoth ecosystem millions of herbivores maintained the ecosystems (Valkenburgh). During the winter the animals ate the grasses that had previously grown during warmer climates. While the herbivores are grazing they helped aid in plant productivity by fertilizing the land around them with their manure (Bressan). This area would have maintained throughout the pleistocene if these animals were their to maintain the landscape. Ecosystems rely solely on the animals inhabiting them. These changes have made the animals separate and the gene barriers have made them reproductively isolated.
Due to glaciers many different species and subspecies happened to get separated and they have stayed like that for decades. The effects of glaciations on the distributions of organisms were major. During different phases forests were fragmented and reduced to smaller islands, where different populations suffered from allopatric speciation. This speciation refers to when biological populations of the same species become isolated from each other and it prevents mass gene flow between the two groups. This then affects the outcome of offspring from those certain groups due to genetic modification over time Dry forests, too humid of an environment, and lack of water can act as gene flow barriers to any of the animals throughout the pleistocene (Cabanne). This diagram shows the distribution of coyotes throughout North america. The lighter grey shows the fossil sites and the black shows the modern sites of the coyotes.
Although the pleistocene era happened 11,000+ years ago, there are still many things that affect this world today. Whether it be the diversification of species throughout North America, or the differences in the plant populations that survived the Pleistocene. Many Ecological and biological changes that have either made different species either become extinct and never seen again today or the animals that went through drastic changes because of body sizes diminishing and the difference in predators.