Tree construction, character-mapping, tree-based evolutionary interpretation, and other developments in molecular and morphological phylogenetics have had a profound influence and have shed new light on the very nature of host-parasite relations and their coevolution. Life cycle complexity, parasite ecology and the origins and evolution of parasitism itself are all underpinned by an understanding of phylogeny.
The Evolution of Parasitism - A Phylogenetic Perspective aims to bring together a range of articles that exemplifies the phylogenetic approach as applied to various disciplines within parasitology and as applied by parasitologists. Unified by the use of phylogenies, this book tackles a wide variety of parasite-specific biological problems across a diverse range of taxa. His main research interests include the systematics of platyhelminths flatworms , and other phyla, particularly with a view to revealing patterns of diversity and diversification associated with parasitism.
Tree construction, character-mapping, tree-based evolutionary interpretation, and other developments in molecular and morphological phylogenetics have had a profound influence and have shed new light on the very nature Buy Direct from Elsevier Bolero Ozon. In some cases, this has been considerable, for instance the loss of homeobox genes in tapeworms Tsai et al. First, the free-living organisms in question are rarely close relatives witness the routine use of Caenorhabditis elegans as a free-living comparator for all parasitic nematodes and until genome sequences for appropriate non-parasitic outgroups are available for each parasitic lineage our understanding of genomic change during the evolution of parasitism will be imprecise.
The evolution of parasite genomes and the origins of parasitism
Second, the scale of genomic reduction is not comparable to the celebrated Microsporidia, and neither is it indicative of widespread degeneracy. Such losses could be within the bounds of normal anagenic change and we need to explore how this rate of gene loss compares to events in purely free-living clades over the same timescales. In fact, far from a picture of degeneracy, parasite genomes display considerable innovation, chiefly in the form of multi-copy effector gene families and the genomic domains that seem to regulate their expression and diversity.
Although such lineage-specific gene family expansions are not unique to parasites, these have the strongest claim to being a theme in parasite genome evolution. Since they are species-specific, our understanding of what these gene families do is patchy, although the needs for diverse surface antigens and for alternative isoforms in different life-cycle stages have clearly driven diversification in many lineages.
In this sense, genome sequences are revealing the basis for parasite specialization, and the extent to which interactions with various hosts drove and drive genomic innovation.
The Evolution of Parasitism - A Phylogenetic Perspective - Google Книги
A decade of parasite genomics has revealed much of the genetic background to parasite adaptations and also identified purely genomic features, such as position, that are adaptive; for instance the variant antigen expression sites in Trypanosoma brucei and Babesia bovis see Jackson, ; Reid, We have seen that the most dynamic features of parasite genomes, those that are typically lineage-specific and which show the greater polymorphism within species and the greatest flexibility in genomic position, are often associated with host interaction and indicate the dominant role of immune selection in directing parasite genome evolution.
Given that a signature of recurrent co-evolutionary interactions is evident in extant parasite clades, this may also suggest that a marked increase in evolutionary rate occurs after the adoption of parasitism, as an abiotic environment is exchanged for a host that fights back. In our search for consistency in parasite genome evolution we find some obvious convergence, antigenic variation for example again and some recurring mechanistic themes repetition, horizontal gene transfer, paralogous gene family expansion outside of chromosomal cores, rapid turnover of surface antigen genes , but broadly, different lineages have evolved unique solutions to common problems of immunity and secondary metabolism, even among nematode lineages descended from a relatively recent free-living ancestor, and within clades that have a common parasitic ancestor, such as the Apicomplexa or Platyhelminthes.
How we understand the evolution of parasitism was revolutionized by phylogenetics and now by genomics. Still, parasites share the majority of their genes with free-living species and so we must ask how these are used differently. When we next revisit reduction and innovation during the origin of parasites, this may concern the networks of interacting RNA and protein species that dynamically control parasite development and physiology.
This interdisciplinary meeting would not have been possible without the generous financial support of the Wellcome Trust. National Center for Biotechnology Information , U. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence http: This article has been cited by other articles in PMC.
Comparative genomics reveals insight into virulence strategies of plant pathogenic oomycetes. Discovery of extant sexual cycles in human pathogenic fungi and their roles in the generation of diversity and virulence In Evolution and Virulence of Eukaryotic Microbes ed.
Signatures of adaptation to plant parasitism in nematode genomes. Parasitology , in press.
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