title: Global Habitat Suitability and Ecological Niche Separation in the Phylum Placozoa.
abstract: The enigmatic placozoans, which hold a key position in the metazoan Tree of Life, have attracted substantial attention in many areas of biological and biomedical research. While placozoans have become an emerging model system, their ecology and particularly biogeography remain widely unknown. In this study, we use modelling approaches to explore habitat preferences, and distribution pattern of the placozoans phylum. We provide hypotheses for discrete ecological niche separation between genetic placozoan lineages, which may also help to understand biogeography patterns in other small marine invertebrates. We, here, used maximum entropy modelling to predict placozoan distribution using 20 environmental grids of 9.2 km2 resolution. In addition, we used recently developed metrics of niche overlap to compare habitat suitability models of three genetic clades. The predicted distributions range from 55°N to 44°S and are restricted to regions of intermediate to warm sea surface temperatures. High concentrations of salinity and low nutrient concentrations appear as secondary factors. Tests of niche equivalency reveal the largest differences between placozoan clades I and III. Interestingly, the genetically well-separated clades I and V appear to be ecologically very similar. Our habitat suitability models predict a wider latitudinal distribution for placozoans, than currently described, especially in the northern hemisphere. With respect to biogeography modelling, placozoans show patterns somewhere between higher metazoan taxa and marine microorganisms, with the first group usually showing complex biogeographies and the second usually showing "no biogeography."
authors.affiliation: ITZ, Ecology and Evolution, TiHo Hannover, Hannover, Germany.
authors.forename: Omid
authors.initials: O
authors.lastname: Paknia
authors.affiliation: ITZ, Ecology and Evolution, TiHo Hannover, Hannover, Germany.|Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.|Sackler Institute for Comparative Genomics and Division of Invertebrate Zoology, American Museum of Natural History, New York, New York, United States of America.
authors.forename: Bernd
authors.initials: B
authors.lastname: Schierwater
mesh_terms: D063147:Animal Distribution / Q000502:physiology; D000818:Animals; D001499:Bayes Theorem; D017691:Caribbean Region; D017753:Ecosystem; D049810:Genetic Speciation; D008522:Mediterranean Sea; D010140:Pacific Ocean; D010802:Phylogeny; D058974:Phylogeography; D054909:Placozoa / Q000145:classification / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D013696:Temperature
chemical_list: D012336:RNA, Ribosomal, 16S