Abstract
AbstractHybrids are chimeric organisms carrying genetic material from at least two divergent parental lineages. Hybridization can contribute to the emergence of novel lineages with unique phenotypic traits that may facilitate their adaptation to new environments. In recent years, genomic analyses have revealed the hybrid nature of several opportunistic human pathogenic yeasts. One of them isCandida inconspicua,a member of thePichia cactophilaspecies complex, for which all sequenced strains are hybrids isolated from Europe with so far unknown parentals. It has been recently proposed thatC. inconspicuaandP. cactophilas.s. should be ranked as the same species due to their genetic similarity. To obtain a better understanding of the evolution of this clade, we sequenced the genomes of theP. cactophilatype strain, of its close-relativePichia pseudocactophila, and of a putativeC. inconspicuaclinical isolate from Alaska and compared them with the previously sequenced genomes ofPichia norvegensis, C. inconspicuaand the recently describedPichia galeolata. Our results show evidence for the existence of distinct hybrid lineages within this clade and suggest an intricate scenario of recurrent hybridizations in this species complex, some of them giving rise to lineages with the ability to infect humans. Given their different hybridization histories, we propose thatC. inconspicua, P. cactophila,and the new clinical isolate from Alaska should represent three distinct species and suggest the namePichia alaskaensisfor the new taxon. Moreover, the nameC. inconspicuais recombined in the genusPichiaasP. inconspicua. Our results clarify the evolutionary relationships within theP. cactophilaspecies complex and underscore the importance of non-vertical evolution.
Publisher
Cold Spring Harbor Laboratory