TITLE:  Animals and Fungi Closer Than Anyone Expected
      AUTHOR:  HECHT, JEFF
     JOURNAL:  New Scientist
    CITATION:  June 12, 1993, 138(1877): 16.
        YEAR:  1993
    PUB TYPE:  Article
 IDENTIFIERS:  MOLECULAR GENETICS; EUKARYOTES; FUNGI; GENETIC TREE OF LIFE; 
               EVOLUTIONARY RELATIONS/EUKARYOTES; CHOANOFLAGELLATES
    ABSTRACT:       Researchers who have compared sequences of ribosomal RNA 
               say fungi are genetically closer to animals than to plants. 
               This work refines the genetic "tree of life," pioneered by 
               Carl Woese of the University of Illinois, which divides 
               living things into three "domains"--eubacteria, 
               archaebacteria, and eukaryotes. Traditionally, living things 
               are classified into one of five kingdoms on the basis of 
               their appearance, not on the basis of their genes. Advocates 
               of the genetic approach believe their classification shows 
               evolutionary patterns more clearly.
                    Researchers at the Marine Biological Laboratory in Woods 
               Hole, Massachusetts, studied the RNA sequences of many 
               eukaryotes, including plants, animals, fungi, and single-
               celled organisms. Statistical analysis of genetic similarity 
               showed that plants were the first to diverge from a common 
               stem, and that animals and fungi evolved later from a common 
               ancestor similar to modern, single-celled eukaryotes called 
               choanoflagellates.
                    The relationship between the three types of multicelled 
               organisms--fungi, plants, and animals--has long puzzled 
               biologists. Fungi were first grouped with plants but were 
               later classed in their own kingdom; their relationship to 
               plants and animals remained unclear. Woese put all three 
               among the eukaryotes, but made no attempt to resolve their 
               interrelations.
                    The Woods Hole researchers say molecular genetics cannot 
               pinpoint the time the groups split, but other evidence 
               indicates animals diverged from the other groups about a 
               billion years ago. The genetic data indicate that fungi, 
               plants, and animals share a common lineage with 
               choanoflagellates. These single-celled organisms have a 
               single flagellum surrounded by a ring of tentacles; they 
               resemble collar cells or choanocytes in sponges, which are 
               among the simplest animals.