Species, speciation and definitions


What is a species and how do we define what determines a species?


Several concepts help scientists categorize species, and all are correct depending on the project's scope. So many concepts exist because of the vast diversity of life on Earth! Scientists have been working for hundreds of years to compile and categorize said diversity. Just as organisms evolve by external factors, science has evolved to become more complex and precise as new discoveries are made such as genetic sequencing. A general definition can be a group of organisms that can successfully interbreed with each other and produce viable offspring. Let's look deeper at some concepts to see how they can be beneficial and what limits they have. 


Firstly the Biological Species Concept (BSC) describes species as groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. This concept can be useful when you are making preliminary observations of a population or populations. You can see which individuals can reproduce and how the offspring survive if they survive. This would require one to observe multiple generations to successfully differentiate all members in a population. This concept also does not account for hybridization between species or horizontal gene transfer like in some bacteria. This concept also falls short when you consider how this applies to species that could potentially interbreed but are separated by distances or geographic barriers. How do we decide if they are separate species? 


Another concept is the Morphological Species Concept or the Genotypic Cluster Concept (GCC) which classifies a species as a group of physically similar or genetically distinguishable individuals that have little to no intermediate forms. This is one of the earlier concepts which can be easily disproved if you are looking at a wide range. If we revisit the tropical island anoles, we know that regardless of the morphological similarities between each population on each island, they are genetically more similar to individuals on their home island than to those who share the same traits on other islands. This can, however, help one to identify a species based on the geographic location they are in. If a scientist is on one such island, they can ascertain that each of the variant anoles are separate species based on their physical features such as leg length, toepad size, and coloration. 


One of the more commonly used concepts is the Phylogenetic Species Concept (PSC) which states that a group of individuals are members of the same species if they are all descended from a common ancestor. This can be helpful when determining how related certain species are if they are related at all. This concept was used to determine if the individuals of the Anole populations are more related to those who physically resemble them from other islands or to those whom they share an island with. This concept also has difficulties encompassing hybridization and horizontal gene transfer. 


All in all, it can be difficult to establish a universal definition of what a species is because really a species is an accumulation of all existing concepts. The ambiguity in defining species allows the exploration of what a species can be and how certain populations can interact with one another. Each concept has its challenges especially where hybridization is concerned, some hybrids can reproduce successfully, some are nonviable from the start causing premature death, and some can survive and grow to adulthood but are sterile and unable to pass on their genetics. We are still learning and exploring the natural world. Through the development and use of genetic sequencing, we can look more closely at groups of individuals to determine their relatedness and degree of relatedness. We have come a long way in defining species, but we still have a ways to go before we can settle on a universal definition. Perhaps one day we will be able to use species concepts to preserve or catapult populations of endangered individuals and conserve our natural resources to the best of our abilities. 

Comments

Post a Comment

Popular posts from this blog

Mutation and the Tree of Life

Image
 Mutation and the Tree of Life What is mutation and how does it affect the tree of life?  A mutation is a change in the genetic code that can lead to a change in a species. Every creature, big and small, has a genetic code that determines how they will look and survive in their environment. These mutations can also cause sicknesses such as cancer, leukemia, and Alzheimer's disease. A mutation that can affect evolution has to be able to pass from a parent to their child. Let's meet the Pacific Mouse (Pacificus rodentus)! These mice build homes on the sandy beaches of the island of Puuwai. They forage in the ocean for kelp to eat!  They have light brown fur on the top halves of their bodies and a light blue belly.  These characteristics allow the mouse to blend into the sand and  the ocean.  Let's explore some mutations in Pacificus rodentius! Looking at the family tree on the right, you will see that the first generation (indicated by "1") are all wild-type...
Read more

Genotypes and Phenotypes

Image
  Genotypes and Phenotypes How does selection act on the phenotype when its really the genotype that is passed to the next generation? Phenotype is the physical expression of a trait and genotype is the gene that causes the expression of the trait. The phenotype is very important to survive in an environment and can be one of the many factors that contribute to the overall success of the organism. For example, if we take a look at the anoles from Improbable Destinies we see that the physical expression or phenotype of each anole is what helps them to truly thrive in their niche. The twig anoles have short and stout legs that hold tightly to twigs and branches while hunting prey and hiding from predators. Garman's anole is larger and stronger, being able to easily navigate the tree trunks and upper branches of trees, even being able to consume other, smaller anoles.  These physical expressions of the genotype are what allows the gene to be successful or not. The genotype goes ...
Read more

Convergence, Natural Selection, "Survival of the Fittest"

Image
Convergence, Natural Selection, and "Survival of the Fittest" What is convergent evolution? Convergent evolution is when species share a trait or character  not  from a common ancestor. In " Improbable Destinies " one of the convergent characters is the human eye versus the octopus eye.  If we look at the figure for convergent evolution, we can observe that the most recent common ancestor for humans and octopuses occurred many, many, years ago. This ancestor is known to not have eyes!  Octopuses and Humans have specially evolved photoreceptors that allow us to view the world more clearly.  When you look at scientific models of each eye you will notice they are almost identical! You can see from the above image, that several characters look and have the same function. The iris is in the same place, surrounding the lens, on both. There are specialized photoreceptors, nerve fibers, and an optic nerve for transmitting sight to the brain.  Eyes could have ...
Read more