Fan-shaped Spectrums of Species and Paleopolyploidy for Foundation of Crossbreeding Evolution

Although Darwin‘s evolutionary mutation theory has been widely accepted, many endeavors tried to challenge it. With more and more observation of successful hybridization and hybrids, the sexual isolation between species has become vague. The mechanism of evolution has been expanded from the classical model of evolution to multiple routes of speciation. Furthermore, a fundamental crossbreeding theory has been raised and proved by two lines of evidences: paleopolyploidy and fan-shaped spectrum of species. Ancient genome duplications are widespread throughout eukaryotic lineages, particularly in plants. The genome polyploidization can break through the sexual incompatibility between diploid counterparts to hybridize and produce new species. By comparing characteristics, all species in every taxon, both in the extinct fossil and extant organisms, can be arranged into fan-shaped spectrum according to their similarity: left primitive type-middle advanced type-right primitive type. The species are primitive at the two ends and advanced at the middle. The primitive two species always resemble two types of more primitive species that can be confirmed as their ancestors respectively, and the middle species is half similar to the two ancestors respectively. These suggest that the species in the spectrum come from two different ancestors by crossbreeding and gene combination. As a sum, advanced species originated from crossbreeding of two primitive ancestors, by major method of polyploidization, and proved by results of fan-shaped spectrum of species. Then, sex is the cause, force and opportunity for evolution.


Sexual barrier between species
Since the evolutionary synthesis, a dominant definition of species in the evolutionary biology has been the so-called "biological species concept". Under this concept, members of the same species "actually or potentially interbreed" (Mayr 1963), whereas members of different species cannot do so (e.g. crossbreed). Thus, there is a clash between two views of species: "one is based on the pattern of gene flow, and the other on the maintenance of a cluster of phenotypes " (Barton and Hewitt 1989).

Mechanisms of reproductive isolation
A variety of mechanisms limit the success of hybridization, including the large genetic difference between most species. Animal species are reproductively isolated by strong barriers to hybridization, which include morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. 3 Animal interspecific hybrids are bred normally from within the same genus.
The offspring display traits and characteristics of both parents, but are often sterile, preventing gene flow between the species (Keeton 1980). Sterility is often attributed to the different number of chromosomes between the two species. A typical example is mules or hinnies with 63 chromosomes. However, fertility in about 4 female mules has been reported (e.g.: Rong 1988).
In plants, some barriers to hybridization include blooming period differences, different pollinator vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of the chromosomes.

Hybridization
In the past, hybridization was viewed as a secondary phenomenon of little or no evolutionary importance. Alternatively, hybrids and hybridization can be viewed as natural intermediate stages of a gradual process of differentiation, possibly in sympatry or parapatry (Arnold and Mallet 1938; Barton and Hewitt 1989). Many studies have been done on hybrid zones (Barton and Hewitt 1989;Harrison 1993;Butlin 1998), but the hybridization is considered having little relevance to interspecific hybridization and the hybrids may be sterile or inviable to produce any offspring.

Introgressive hybridization have been described and defined in plants in
1938 (Anderson and Hubricht 1938). In recent 20 years, some researchers have been made in understanding the species boundary in animals both below and above the level of species. Below the species level, forms are known which remain distinct in spite of potential or actual gene flow. Above the species level, they are beginning to appreciate that hybridization, while rare on a perindividual basis, is a regular and probably important occurrence in nature (Arnold 1997;Grant 1992;Allendorf et al. 2001;Seehausen 2003). On average, at least 10% of animal species and maybe 25% of plant species are known to hybridize in nature, although the fraction of species that hybridize may be much higher in rapidly radiating groups (Mallet 2005).

Mutation for speciation
It is widely believed that mutations arise continuously and without any consideration for their utility. But more and more controversial papers have been published. Some experiments suggested that cells may have mechanisms for choosing which mutations will occur. Cairns found that when they placed bacteria that could not digest the milk sugar lactose in an environment where that sugar was the sole food source, the cells soon evolved the ability to convert the lactose into energy (Cairns et al. 1988).
Witkin reported that accidentally irradiated millions of E. coli with a lethal dose of ultraviolet light. They were all dead except for one, in which four bacterial cells had survived and continued to grow (Witkin 1946). Somehow, those cells were resistant to UV radiation. These are now known as the SOS response. The harsh environments cause nonrandom mutations and help bacteria evolve advantageous traits more quickly in stressful environments. It's a totally new way that the environment can have an impact on the genome to allow adaptation in response to need (Hull et al. 2017;Frenk et al. 2017). These indicate that the genome itself may have any kind of intelligence to keep "alive" and inheritance.

Back to Mendel and crossbreeding
Under the shadow of Darwin's success is Mendel's illuminating work  These types should be results of hybridization and the chromosome numbers have been changed or reduced with an evolutionary rate.

Polyploidy and paleopolyploidy
Plant species often hybridize and the resulting hybrids are fertile more often. with plants, known paleopolyploidy is less in the animal kingdom. It has been identified mainly in amphibians and bony fishes. The idea that vertebrates share a common whole genome duplication is known as the "2R Hypothesis".

2R Hypothesis
The hypothesis of vertebrate paleopolyploidy was proposed by Susumu Ohno as early as the 1970s. He reasoned that the vertebrate genome could not achieve its complexity without large scale whole-genome duplications. The "two rounds of genome duplication" hypothesis (2R hypothesis) came about, which is a hypothesis that the genomes of the early vertebrate lineage underwent two complete genome duplications, and thus modern vertebrate genomes reflect paleopolyploidy (Hokamp et al. 2003).
The 2R hypothesis saw a resurgence of interest in the 1990s for two reasons.
First, gene mapping data in humans and mice revealed extensive paralogy regions -sets of genes on one chromosome related to sets of genes on another chromosome in the same species, indicative of duplication events in evolution (Lundin 1993). Paralogy regions were generally in sets of four. Second, cloning of Hox genes in amphioxus revealed presence of a single Hox gene cluster, in contrast to the four clusters in humans and mice (Garcia-Fernández 1994).
These two lines of evidence suggest that two genome duplications occurred in the ancestry of vertebrates. A new study generated the sea Lamprey genetic map, which yielded strong support for the hypothesis that a single wholegenome duplication occurred in the basal vertebrate lineage, preceded and followed by several evolutionarily independent segmental duplications that occurred over chordate evolution (Smith 2015).

Advantage of allopolyploids
The allopolyploids arise as a result of the hybridization of two related species, which are believed to be much more prevalent in nature, possibly because allopolyploids inherit different genomes, resulting in increased heterozygosity, and therefore higher fitness (Soltis 2000). These different genomes result in an increased likelihood of large genomic reorganizations, which can be either deleterious, or advantageous. The latter include: 3) Speciation It has been suggested that many polyploidization events created new species, via a gain of adaptive traits, or by sexual incompatibility with their diploid counterparts.

II. Fan-shaped Spectrum of Species and Crossbreeding
In

Difficulties of the one-single ancestor
According to Darwinism's mutation theory, all animals share a single common ancestor (Darwin 1872 prominently come from another ancestor. Actually, it is a common phenomenon that when a species resembles one ancestor, it always possesses traits that are quite unlike that ancestor, but resembles another ancestor.

Spectrums of species, involving two ancestors
After analyzed almost all protists, all animal and plants from fossil forms and extant varieties and found that species always constitute a fan-shaped, successive series or spectrum at every level of taxon (e.g. Class, Order or Family) according to their similarity of characteristics. For instance, all nine species in a class of animals can be arranged into a spectrum as: The adjacent species are most similar. Moreover, the species at the two ends of the spectrum (i.e. A1 and I9) highly resemble to two taxa of species in lower or more primitive class of (e.g. P1 and P2) that can be confirmed as their Such spectrum can be easily understood in a family with many children, in which one may be very father-like and another may be very mother-like, others are partly father-like or mother-like. Someone may be not father-like and mother-like, actually, half-like respectively.

Crossbreeding model and Crossbreeding equation
Apparently, more advanced species (new species) came from the combination of two primitive species (ancestors) from different lineages upon the spectrum. The way of combination is no other method than crossbreeding in the natural conditions. This process can be simply indicated as: The discovery of fan-shaped spectrum for a taxon

Normal Distribution of species
In the probability theory of Statistics, Normal (or Gaussian) Distribution is a continuous probability distribution, with a few members at the high and low ends and many in the middle, as a bell curve. Many common attributes follow normal distribution. Here the descendants of crossbreeding, or the spectrum, from random combination also roughly follow the Normal Distribution, in which the middle type always have highest success rate or high race density, and the primitive type in two ends always have lower opportunity to survive and lower race numbers or density. Therefore, a spectrum of species shows a Normal Distribution (Fig. 2).

Evolutionary steps in animals
All origins of protists and animals (exception of marsupials and the South American ungulates) are described and proved as above spectrum and equation in the book (Liu 2016). Next are some equations.
Origin of Protists:

5) Mollusks\Bivalves + Annelids\Polychaetes Arthropods
Origin of Chordates: Annelids\Polychaetes  Arthropods (Fig. 3). Fig. 3 The two-ancestor of crossbreeding theory is exemplified by arthropods. In arthropods, the ostracoda closely resemble the bivalve and the onychophora highly resemble the polychaete. The tadpole shrimp and the shrimp of arthropods, with the carapace of thorax came from the bivalve and the segmented abdomen came from the polychaete, is middle type, half resembling the two ancestors respectively. Mixed from many free-sources. The most interesting origin of ourselves came from crossbreeding between lemurs and bears, where monkeys, humans and apes comprised a spectrum.
Monkeys resemble lemurs and locate at one end of the spectrum; apes resemble bears and locate at another end of the spectrum; humans are in the middle of the spectrum. The feet and teeth of humans are mainly from bears, but the hands obviously from lemurs. Both humans and apes have not a tail, which resemble the bears with a tail stub. By such a way, the evolutionary relationship of all protists and animals has been reconstructed. Some are satisfying and some require more analysis.

Plant evolution by crossbreeding
The plants in various taxon also can be arranged into spectrum as in the animals, in which two ancestors can be found Liu, 2021 that is just the fan-shaped spectrum of species. Actually, crossbreeding is the rationally natural way. By this way, the origin of species becomes believable, understandable and available.
Next are some views about the crossbreeding theory.
1) According to the mutation of Darwinism, when A mutated to B, A must disappear; When B mutated to C, B must disappear…; When Y mutated to Z, Y must disappear. But in our global, from A-Z, most types are existing. From the lowest viruses and bacteria to the highest arthropods and primates, almost all types are present, although there are many extinct species.
2) Any species have two different ancestors, but not one-common ancestor. The species in the taxon have been re-arranged into fan-shaped spectrums than the phylogenic tree. The evolutionary diagram is consisted of fan-shaped spectrum in nets, but not a branched tree.
3) Species are defined by their reproductive isolation. Animal crossbreeding often occurs during mass extinction, in which solitary survivors copulate with others, driven by sexual pressure. Intense mating instincts drive hybrid speciation, breaking the law of reproductive isolation. Thus, a mass extinction is always accompanied by a great explosion of new species.
Otherwise, the crossbreeding also can be taken place between pioneers from two groups in contacting regions for sexual attraction. Then, the sex is the cause, force and opportunity for evolution.

4)
In the animal's ontogenesis, the larval form is often more like their one ancestor, while the adult form is more like another ancestor. Understanding the larval and adult forms is very important for determining the two ancestors. A few plants also have such ontogenesis.

5)
A lot of species is sometimes difficult to classify. Now, according to new theory, their position can be clearly found in some spectrums.

6)
The crossbreeding theory emphasizes the similarity among species, in which many genes are shared by almost all or many species, but not the differences that produced by mutation. Furthermore, the combination of genes to form new characteristics is emphasized, but not the mutation of genes to produce new characteristics. Understanding the combination and similarity, and looking for the similarity, is very important new angle for understanding of life and controlling of life.