What is the difference between speciation and macroevolution

Although not widespread among animals, sympatric speciation has been significant in plant variation. Hugo de Vries, a Dutch botanist, is credited with identifying polyploidy as an agent of sympatric speciation.

Through self-pollination, he created a large flowering polyploid evening primrose with 28 chromosomes instead of the normal diploid number of 14 chromosomes. The speed by which new species are created depends upon the genetic makeup of the species, their ability to adapt to environmental changes, and the speed and severity of the environmental changes. In earlier times, it was thought that speciation occurred slowly over long periods of time. This gradualistic theory has recently given way to the punctuated equilibrium model that defines speciation as occurring in jumps or sudden shifts of speciation interspersed within long periods of inactivity.

Emerging evidence from fossils lends support to the punctuated equilibrium model. This discussion is continued in the next section.

Moulton, Ed. All rights reserved including the right of reproduction in whole or in part in any form. Email Facebook Twitter.

Macroevolution refers to evolution of groups larger than an individual Macroevolution encompasses the grandest trends and transformations in evolution, such as the origin of mammals and the radiation of flowering plants.

Evo Examples Teaching Resources Learn more about macroevolution in context: How to survive a mass extinction: The work of David Jablonski , a research profile. Ancient fossils and modern climate change: The work of Jennifer McElwain , a research profile. Where species come from , a news brief with discussion questions.

For example, when you have a species that reproduces asexually, finding the boundaries between species can be a little tricky. But in most cases it does a pretty good job. The Biological Species Concept is especially useful when you have two species that look and act very similar. Eastern and Western Meadowlarks are a good example of this. They look almost exactly the same. But they cannot interbreed successfully.

Therefore, they are separate species. This definition also helps when we study evolution. Where can we draw the line between microevolution and macroevolution? When enough genetic changes accumulate in a population, eventually it loses the ability to mate with others of its species. Then, by definition, it becomes a new species. In other words, macroevolution has occurred. As we just discussed, many critics claim that macroevolution can never happen—one species can never cross over to become another one.

This statement might sound valid, but a little bit of investigation shows that it is not well supported by evidence. For one thing, the only difference between micro and macroevolution is scope. When enough micro changes accumulate, a population will eventually lose its ability to interbreed with other members of its species. At this point, we say that macroevolution has occurred.

The same processes—random mutation and natural selection—cause both micro and macro evolution. There are no invisible boundaries that prevent organisms from evolving into new species. It just takes time. Usually, the amount time required for macroevolution to occur is significant—on the order of thousands or millions of years. In fact, the evolution of new species sometimes happens so quickly that we can actually see it take place!

Biologists Peter and Rosemary Grant had been studying finches since They lived on an island called Daphne Major in the Galapagos. It was here that they conducted their studies.

When they first began their studies, only two species of Finch lived on Daphne Major: the medium ground finch and the cactus finch. But, in , Peter and Rosemary noticed that an odd new finch had immigrated to the island. It was a hybrid, a mix between a cactus finch and a medium ground finch. The odd misfit had an extra large beak, an unusual hybrid genome, and a new kind of song.

But somehow he was still able to find a mate. The female was also a bit of a misfit and had some hybrid chromosomes of her own. So their offspring were very different from the other birds on the island. Rosemary and Peter continued to carefully watch the odd hybrid line. They wondered if the birds would become isolated from the other finch species on the island or if they would eventually re-assimilate. These mechanisms include mutation, migration, genetic drift, and natural selection.

Theory suggests that the effects of these processes accumulate over time and can sometimes result in the divergence of populations and the birth of new species. In contrast, macroevolution describes patterns on the tree of life at a grand scale across vast time periods. Many different patterns can be observed across the tree of life at a grand scale Figure 1 , including stability, gradual change, rapid change, adaptive radiations , extinctions, the co-evolution of two or more species, and convergent evolution in traits between species -- just to name a few.

Macroevolutionary studies tend to draw heavily from the fossil record. Fossils document the emergence of new life forms, how their geographic distribution changed over time, and ultimately when they went extinct.

In contrast, microevolutionary changes are not frequently observed in the fossil record because the processes that govern evolutionary change within species are thought to occur over much shorter time scales.

Figure 1 Example of macroevolutionary patterns as they would appear in a phylogenetic tree, including extinctions, adaptive radiations, and stasis. Understanding macroevolution is important because it explains both the diversity of life and the pace of evolutionary change. Does evolution happen slowly or quickly? One group holds that microevolutionary processes alone can sufficiently explain grand patterns and radical changes on the tree of life.

In other words, mutation, migration, genetic drift, and natural selection can produce major evolutionary changes given enough time. The key element is vast amounts of time -- on a scale that is difficult for most people to imagine. This model of macroevolution is called phyletic gradualism. It proposes that most speciation events are the result of a gradual and uniform transformation of one species into a new one through a process called anagenesis. On the other hand, many scientists propose that grand patterns in the history of life cannot be explained exclusively by changes in allele frequencies over time, even rapid ones.

Instead, these scientists propose that large changes on the tree of life were preceded by events that decoupled the tempo and mode of evolutionary change from predictable microevolutionary processes.

Often these decoupling events were major, even cataclysmic, environmental changes that opened up new niches or caused extinctions. A classic example of such an event was the meteor impact at the end of the Cretaceous that contributed to the extinction of the dinosaurs, and as a consequence, opened up new niches that precipitated the diversification of mammals.

There are many other examples of such events, including the acquisition of novel traits like the advent of flowers as a means of reproduction in plants. It proposes that grand patterns of evolutionary change on the tree of life involve the rapid splitting of one ancestral species into two or more descendant species through cladogenesis, often followed by long periods of stasis in the descendant species Eldredge et al.

Patterns of macroevolution are easy to spot on the tree of life when one considers big events like the abrupt appearance of tetrapods in the fossil record, long periods of stasis like that observed in sharks and crocodiles, and adaptive radiations including the fairly! As one moves out along the branches of the tree of life, the processes that produced the rich patterns of biodiversity along a particular twig can be harder to understand and interpret.

Yet, there are many examples of macroevolutionary phenomena found in the order Primates, including stasis, adaptive radiations, extinctions of entire lineages, co-evolution, and convergent evolution. Recent studies have provided new insights about the tempo and mode of primate evolution using phylogenetic trees from genetic data gathered across the genomes of many extant primate lineages Fabre et al.

These studies have revealed that the tempo and mode of evolution among the primates have been punctuated by the persistence of ancient relic lineages i. Perelman et al. The long branch that separates Tarsiers from other primates suggests that this group is an ancient relict lineage that has remained in stasis relative to other primates. In contrast, the Lemuriformes part of the tree has many early short branches followed by some long branches in the descendants see Figure 1 , which suggests that the ancestors of extant lemurs experienced a rapid adaptive radiation that likely coincided with its colonization of Madagascar about mya Perelman et al.

Figure 1 A molecular phylogeny of 61 primate genera. Perelman, P. A molecular phylogeny of living primates. PLoS Genetics 7 Phylogenetic trees also allow for comparing and contrasting the tempo and mode of evolution among different groups of primates inferred from fossil and genetic data.

For instance, has evolution proceeded differently in New World monkeys versus Old World monkeys? New World monkeys last shared a common ancestor with Old World monkeys about mya, but the diversification of New World monkeys and the divergence times of these lineages are not well understood. Hodgson et al. They found that New World monkeys have experienced both successive radiations and stasis during their evolution.

Specifically, they found that the earliest New World monkey fossils were much older than the divergence dates they estimated for the extant New World monkey species. Using this evidence, along with patterns observed on phylogenetic trees, these researchers suggested that there was an early radiation of New World monkey ancestors followed by a period of stasis and then the extinction of most of this group prior to the Miocene.

Phylogenetic trees based on genetic data cannot reveal much about what might have caused adaptive radiations or extinctions. Careful examination of fossils combined with an understanding about what Earth's environment was like when these fossils were living can be used to infer what might have precipitated different macroevolutionary events. For example, during the Miocene the ancestors of Old World monkeys and apes experienced both radiations and extinctions that have been linked to climate change Harrison In the early Miocene, primates found in Africa and the Arabian Peninsula were a diverse group that occupied tropical forests and woodlands Figure 3.

During the mid-Miocene, Africa reconnected with Eurasia and a major period of global warming caused the expansion of tropical habitats northward. These developments allowed the nascent hominoid lineage to branch off and colonize newly available Eurasian habitats, leading to a major proliferation of ape species across much of Eurasia.

However, around 9. Figure 3 The family tree of extant hominoids includes only a small fraction of the diversity of apes that have lived on this planet. During the Miocene, up to ape species once lived throughout much of Europe and Asia, but ultimately went extinct.

Proconsul may have been the last common ancestor of extant hominoids. Sivapithecus was probably an ancestor to orangutans.