Although hybridization and introgression have been considered important in generation of plant diversity, their role in evolutionary diversification of animals remains unclear In this review, we reconsider the significance of introgressive hybridization in evolution and diversification of animals to determine if the generally negative assessment of these processes is warranted Unlike the situation for plants, hybrid animal taxa appear to be relatively rare This could, however, be due to negative attitudes toward hybridization and difficulty in detecting such forms Hybridization has been responsible for instantaneous creation of several unique complexes of polyploid and unisexual animals Allopolyploidy has allowed for diversification, whereas unisexual taxa have acted as conduits of gene exchange among related sexual species Many instances of diploid, bisexual taxa of hybrid origin have been put forward, but few have been carefully tested Changing attitudes toward hybrids and technological advances should allow for careful consideration of hypothesized hybrid taxa and will undoubtedly increase the number of known animal hybrid taxa

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The role of hybridization and introgression in the diversification of animals

The review concentrates on literature that has appeared since the 1960s. Since then, numerous species of Paragonimus have been described, mainly from Asia but also from Africa and the Americas. Some of these cause disease in humans. Recent information on life cycles and routes of transmission is summarized. All described species and their hosts are listed, with synonyms where known. For well-known species such as Paragonimus westermani, subspecific taxa and strains are reviewed and genetic studies discussed. Paragonimiasis in humans and experimental animals is discussed with emphasis on clinical manifestations and pathology, diagnosis, immune interactions with the host, treatment and public health issues.

Paragonimiasis and the Genus Paragonimus

Mitochondrial genomes of parasitic flatworms.

The application of molecular systematics to the parasitic Platyhelminthes (Cestoda, Digenea and Monogenea) over the last decade has advanced our understanding of their interrelationships and evolution substantially. Here we review the current state of play and the early works that led to the molecular-based hypotheses that now predominate in the field; advances in their systematics, taxonomy, classification and phylogeny, as well as trends in species circumscription, molecular targets and analytical methods are discussed for each of the three major parasitic groups. A by-product of this effort has been an ever increasing number of parasitic flatworms characterized genetically, and the useful application of these data to the diagnosis of animal and human pathogens, and to the elucidation of life histories are presented. The final section considers future directions in the field, including taxon sampling, molecular targets of choice, and the current and future utility of mitochondrial and nuclear genomics in systematic study.

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Advances and trends in the molecular systematics of the parasitic Platyhelminthes.

Publisher Summary This chapter provides an outline of the methods used for classifying and identifying polyploid animals, followed by a discussion of proposed explanations for its relative rarity as compared to plants (where it may be near-ubiquitous). The duplication of entire genomes plays a significant role in evolution that has traditionally been reserved for plants, but in terms of ancient events, has recently expanded to include groups as diverse as yeast and vertebrates. More recent duplications of complete chromosome sets have been regarded as relatively unimportant in animal evolution. Polyploidy is often occurs only under remarkably uncommon circumstances among the metazoa and is therefore generate a curiosity than an evolutionary force in this group. The known cases of polyploid vertebrates and invertebrates are reviewed in succession, with notes about the phenotypic and evolutionary consequences interspersed throughout. It is known that polyploidy has arisen by a variety of mechanisms in a diverse array of animal taxa, covering approximately every major phylum. In part, the relatively low rate of discovery of polyploidy in animals reflects the low level of effort put into looking for it, which in turn is probably driven by the low expectation of success in finding it. In part, the relatively low rate of discovery of polyploidy in animals reflects the low level of effort put into looking for it, which in turn is probably driven by the low expectation of success in finding it.

Polyploidy in Animals

Restriction endonuclease analysis of mitochondrial DNA was carried out in order to differentiate diploid and triploid types of Paragonimus westermani originating from Japan. It was found that out of 16 restriction enzymes. PstI, HaeIII and RsaI revealed consistently different cleavage patterns between the two types.

https://kochi.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1381&item_no=1&attribute_id=17&file_no=1

D. Kim

Papers

Mitochondrial DNA differentiation of Japanese diploid and triploid Paragonimus westermani