Specialization occurs when a given population adapts to a habitat and certain of its genotypes are more prolific than others. Those that are less prolific are naturally sifted from the population and those that survive are the specialized form of the genome for that habitat. In specialization, the genome actively adapts to the otherwise passive environment. This is in contrast to Natural Selection which suggests that nature is the acting agent while the genome is passive to it.
Common Descent as described by the evolutionary narrative uses a "tree" analogy. The creationist narrative uses an "orchard" analogy. The primary differences in the two are:
(a) The tree starts with a simple organism and grows in functional integrity (genetic material) over time. (b) The orchard starts with a master genome for the given kind (family) of animal, then declines in functional integrity (and genetic material) over time.
The common concept of speciation is difficult for secular science to describe because its application is inconsistent and its observation is always after-the-fact. For example, a lion and tiger are examples of different species, but what mechanism caused the speciation? Separation of populations seems reasonable in some cases but not in others (where multiple species of a common family co-habitate and commingle).
A recent study of mitochondria in 37 different lines of cat revealed that all of them hail from a single cat-mother in Asia.
In another study on mitochondria in dogs, some 77 domestic dogs, 49 wolves and 4 coyotes were traced back to a single family of ancient wolves in Europe.
An evolutionary view would suppose that these ancient cats and wolves gained more functionality over time to become their modern forms. A creationist view would suppose that the dog and cat "kind" were specifically created with hyper-adaptive genomes. These ultimately spread out over the Earth to eventually become their modern forms.
In the creationist model, the animal population moves into a habitat and specializes as opposed to speciates. A speciation model presumes that the new population is growing more genetic material after it deviates from the original population. A specialization model presumes that the new population is losing functionality as it adapts to its new habitat. Why is this? For any adaptive system undergoing an adaptation event, it moves toward specialization and away from adaptability. In short, it loses adaptability each time it adapts. This is a loss-of-function model.
Anecdotally, whenever scientists discuss decay in physics or chemistry, they speak in terms of a universal effect. Creationists understand this effect is related to the Curse after the Fall of Man. Secular biologists however, will object to this universality of decay by claiming that biological life gains function over time "because evolution is true." They in fact exempt biological processes from the naturally observable processes in the rest of nature. What if the biological processes are not exempt at all, and all biological systems are experiencing ongoing loss-of-function and genetic decay over each successive generation? What if living systems are not getting better, but are moving inexorably toward extinction? One universal and immutable rule of the living systems is this: extinction without replacement. And today, the strong trend is extinction without speciation. In other words, species are going extinct faster than they are being replaced, at a rate greater than 1000 per year.
Richard Lenski and Specialization
The famous "evolution" experiment by Richard Lenski actually claims that the bacteria are "specializing" into their habitat. Additional observations include that the bacteria are losing structural integrity (rounder, larger), are less adaptable than their ancestors, have exhibited loss-of-regulation in DNA (runaway mutations) and loss-of-regulation in function (citrate absorption is simply a broken regulator). These loss-of-function observations are then twisted into a torturous interpretation that they claim actually proves evolution, when they do just the opposite. They prove that even the lowly bacteria are subject to a loss of-function effect.
John Sanford and Genetic Entropy
John Sanford PhD, with Genetic Entropy describes the genomes of all creatures as being in a rapid state of decay over generations, the result of accumulated mutations, ultimately leading to extinction of all animals in the relatively near-term. This dovetails to the very temporary nature of the Creation as a whole, that it will pass away and be replaced by a new Creation. Mutations, therefore, are the chief cause of loss-of-function and have never been proven to cause gain-of-function. Sanford asserts that the individual genes are invisible to natural selection because the genes appear in unbreakable linkages and clusters requiring an all-or-nothing selection at the level of the phenotype (the whole individual) rather than the individual genes.
Specialization occurs at the genotype and in the creationist model for the aforementioned cats, could be explained thus: The hyper-adaptive population of cats is growing rapidly. Its population exhibits a wide diversity of sizes, fur colors and patterns, tail and ear appearance etc. In search of food, a group of these breaks off and moves into a habitat in a mountainous region. Here, the smaller cats and larger cats do not proliferate as fast as mid-sized cats. Over many generations, the population starts to look a lot like a mountain lion. They have effectively specialized to the habitat and their loss-of-function from their ancestors prohibits them from procreating with prior lines of cats.
Loss-of-genetic material is easily explained in terms of Mendel's flowers. If he observes red, pink and white offspring, but takes the red flowers alone and starts breeding them while leaving the white allele in the prior population, this line of flowers will never again produce a white flower (unless there is a mutation). Likewise if Mendel's assistant takes another set of red flowers, starts to breed many generations of red flowers and on the 200th generation a white flower appears, he may go to Mendel and claim that the white flower is new-genetic material. Mendel understands otherwise. The white allele was always there, just not expressing itself.
If we take the concept of specialization to the cat-and-dog mitochondrial studies above, and presume the "orchard" model that each started out with a hyper-adaptive genome that branched out, lost function as it specialized but continued to adapt to various habitats, this is a better explanation of the current-state of dogs and cats, in fact every animal, than a supposed gain-of-function through evolutionary means.
Specialization is a loss-of-function model and dovetails to the Bible's description of history. Speciation is a gain-of-function model which has never been observed nor accurately (or adequately) defined.