Animal Systematics lecture 4
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  • THE MALE OFFSPRING OF SUBSPECIES ARE OFTEN STERILEHowever, the terms subspecies and geographical race are used synonymously by taxonomists of mammals, birds, and insects. Race: local populations with in subspecies. Ecological Race, controversial. Since No two localities are exactly identical with respect to their environment, every subspecies is at least theoretically also an ecological race. However, some populations differ in their ecological requirements without acquiring taxonomically significant differences. More important from the taxonomic /evolutionary point of view are host races among parasites and species-specific plant feeders. If gene flow between populations on different hosts is drastically reduced such host races are the equivalent of geographic races in free living animals. Also such host races often develop subspecific characters.
  • THE MALE OFFSPRINGS OF SUBSPECIES ARE OFTEN STERILEHowever, the terms subspecies and geographical race are used synonymously by taxonomists of mammals, birds, and insects. Race: local populations with in subspecies. Ecological Race, controversial. Since No two localitite are exactly identical with respect to their environment, every subspecies is at least theoretically also an ecological race. However, some populations differ in their ecological requirements without acquiring taxonomically significant differences. More important from the taxonomic as well as evolutionary point of view are host races among parasites and species-specific plant feeders. If gene flow between populations on different hosts is drastically reduced such host races are the equivalent of geographic races in free living animals. Also such host races often develop subspecific characters.
  • For many biologists, the question of whether geographicseparation is strictly necessary for speciation (i.e., the question of whether sympatric speciation occurs) comes into sharpest focus with the case of Rhagoletispomonella. The apple maggot fly that has diverged into two host races (apple and hawthorne), apparently under geographic sympatry and aided by the different fruiting times of the two hosts. Mayr’s former student Guy Bush discovered the history of sympatric divergence in Rhagoletis, and it has long been a standard component of the debates on the prevalence of sympatric speciation.
  • it is a wonder how hundreds of species could form within confined bodies of water within 1 million years.Yong-Jin take a close look at a group of rock-dwelling species from Lake Malawi. To gain resolution, they used a new type of genetic marker that includes a microsatellite and linked sequence.
  • The results suggest that some of these species have formed within the past few thousands years and that gene exchange is ongoing between species at some loci
  • The term was coined by the English evolutionary biologist Julian Huxley in 1938. An ecocline or cline (Gr. gradient, to lean)clines consist of ecotypes or forms of species that exhibit gradual phenotypic and/or genetic differences over a geographical area, typically as a result of environmental heterogeneity.
  • At right angles to the clines are the lines of equal expression of the character.(points of identical phenotype); such a line is called an isophene. For instance, if in the range of a species of butterfly the percentage of white specimens varies from north to south, the corresponding isophenes may be indicated on a map.Any character, be it a morphological, physiological, or other genetically determined character, may vary clinally. Clines may be smooth, or they may be step clines with rather sudden changes of values.
  • At right angles to the clines are the lines of equal expression of the character.(points of identical phenotype); such a line is called an isophene. For instance, if in the range of a species of butterfly the percentage of white specimens varies from north to south, the corresponding isophenes may be indicated on a map.Any character, be it a morphological, physiological, or other genetically determined character, may vary clinally. Clines may be smooth, or they may be step clines with rather sudden changes of values.
  • Clines do not receive nomenclatural recognition. Indeed, when the geographic variation of a species is clinal, it is usually inadvisable to recognize subspecies, except possibly for the two opposite ends of the clien when they are very different or separated by a pronounced step. In days when the subspecis was still defined typologically, many proposals were made to subdivide heterogenous subspecies into still smaller hopefully uniform taxa, and terms were proposed for such taxa, e.gnatio. Now that it is being realized that every local population is different from every other one, even if they live only a few miles apart or less and that these populations are nto sharply separted from each other(except where separated by barriers), there is no longer any excuse for a formal recognition of nnumerable local subdivisions of subspecies. The term deme adopted by zoologist for the evolutionary unit corresponding to a loccal is not the name of a taxonomic category.
  • Ring speciesare a distinct type of cline where the geographical distribution in question is circular in shape, so that the two ends of the cline overlap with one another, giving two adjacent populations that rarely interbreed due to the cumulative effect of the many changes in phenotype along the cline. The populations elsewhere along the cline interbreed with their geographically adjacent populations as in a standard cline. Ring species present an interesting problem for those who seek to divide the living world into discrete species, as chain species are closely related to speciation (in this case, parapatric).
  • A classic example of ring species is the Larus gulls circumpolar species "ring". The range of these gulls forms a ring around the North Pole.The Herring GullL. argentatus, which lives primarily in Great Britain and Ireland, can hybridize with the American Herring GullL. smithsonianus, (living in North America), which can also hybridize with the Vega or East Siberian Herring GullL. vegae, the western subspecies of which, Birula's GullL. vegaebirulai, can hybridize with Heuglin's gullL. heuglini, which in turn can hybridize with the Siberian Lesser Black-backed GullL. fuscus. All four of these live across the north of Siberia. The last is the eastern representative of the Lesser Black-backed Gulls back in north-western Europe, including Great Britain.
  • all that distinguishes a ring species from two separate species is the existence of the connecting populations - if enough of the connecting populations within the ring perish to sever the breeding connection, the ring species becomes two distinct species.Formally, the issue is that interfertile " is not a transitive relation – if A can breed with B,and B can breed with C, it does not follow that A can breed with C – and thus does not define an equivalence relation. A ring species is a species that exhibits a counterexample to transitivity.
  • all that distinguishes a ring species from two separate species is the existence of the connecting populations - if enough of the connecting populations within the ring perish to sever the breeding connection, the ring species becomes two distinct species.Formally, the issue is that interfertile " is not a transitive relation – if A can breed with B,and B can breed with C, it does not follow that A can breed with C – and thus does not define an equivalence relation. A ring species is a species that exhibits a counterexample to transitivity.

Animal Systematics lecture 4 Animal Systematics lecture 4 Presentation Transcript

  • INFRASPECIFIC CATEGORIES (continued)
    THE MALE OFFSPRING OF SUBSPECIES ARE OFTEN STERILE
  • RACE: local populations with in subspecies.
    not recognized in the taxonomic hierarchy.
    Subspecies and geographical race are used synonymously by taxonomist of mammals, Birds and Insects.
    Since No two localities have identical environment, every subspecies is at least theoretically also an ecological race.
  • RACE
    Imp. Taxonomically are host races among parasites and species-specific plant feeders.
    If gene flow between populations on different hosts is drastically reduced such host races are the equivalent of geographic races in free living animals.
    such host races often develop subspecific characters.
  • The Question:whether geographic separation is essential for speciation? or whether sympatric speciation occurs?
    ___ Rhagoletispomonella(apple maggot fly)
    diverged into 2 host races 1. apple 2. hawthorne__ Sympatric, BUTdifferent fruiting
    times of the two hosts.
  • Hawthorn
    Apple:
  • Hawthorn Berry . Apple
  • Lake Malawi Lake Victoria
    relatively young. 1 million year old
    100s of Species
  • Yong-Jin take a close look at a group of rock-dwelling species from Lake Malawi. To gain resolution, they used a new type of genetic marker that includes a microsatellite and linked sequence.
    some of these species have formed within the past few thousands years and that gene exchange is ongoing between species at some loci
  • cline(Gr. Gradient)
    Julian Huxley in 1938.
    An ecocline or cline consist of ecotypes or forms of species that exhibit gradual phenotypic and/or genetic differences over a geographical area, typically as a result of environmental heterogeneity.
  • cline
    Genetically, clines result from the change of allele frequencies within the gene pool of the group of taxa in question.
    Clines may manifest in time and/or space.
  • cline
    Clines– Gradient in features within a species over space or time
    Cline is a character Gradient, not a category. A single population may belong to as many different clines as it has characters.
  • cline
    A cline is formed by a series of contiguous populations in which a given character changes gradually.
    Any genetically determined character, may vary clinally. Clines may be smooth, or they may be step clines with rather sudden changes of values.
  • Hybrid Zone,
    Hybrid Zone where multiple narrow
    clines occur.Can be used to
    understand gene flow
  • Example of Cline in Salamander
    Ensatinaescholtzii
  • C
    GAP IN RING
  • Clines do not receive nomenclatural recognition.
    When the geographic variation of a species is clinal, it is usually inadvisable to recognize subspecies, except possibly for the two opposite ends of the cline when they are very different .
  • Ring species – Cline over space (biogeographic) that results in failure of end members to interbreed, e.g. In Sea gulls.
  • Ring speciesare a distinct type of cline where the geographical distribution in question is circular in shape, so that the two ends of the cline overlap with one another, giving two adjacent populations that rarely interbreed due to the cumulative effect of the many changes in phenotype along the cline.
    The populations elsewhere along the cline interbreed with their geographically adjacent populations as in a standard cline.
    Ring species present an interesting problem for those who seek to divide the living world into discrete species, as chain species are closely related to speciation (in this case, parapatric).
  • Ring speciesare a distinct type of cline where the geographical distribution is circular in shape, so that the two ends there are two adjacent populations that rarely interbreed
    The populations elsewhere along the cline interbreed
    Ring species present an interesting problem for those who seek to divide the living world into discrete species, as chain species are closely related to speciation (in this case, parapatric).
  • A classic example of ring species is the Larus gulls circumpolar species "ring". North Pole.
    The Herring GullL. argentatus, which lives primarily in Great Britain and Ireland, can hybridize with the American Herring GullL. smithsonianus, (living in North America), which can also hybridize with the Vega or East Siberian Herring GullL. vegae, the western subspecies of which, Birula's GullL. vegaebirulai, can hybridize with Heuglin's gullL. heuglini, which in turn can hybridize with the Siberian Lesser Black-backed GullL. fuscus. All four of these live across the north of Siberia. The last is the eastern representative of the Lesser Black-backed Gulls back in north-western Europe, including Great Britain.
  • A Herring Gull, Larusargentatus (front) and a Lesser Black-backed Gull. Larusfuscus (behind) in Norway: two species with clear differences.
  • The Lesser Black-backed Gulls and Herring Gulls are sufficiently different that they do not normally hybridize; thus the group of gulls forms a continuum except where the two lineages meet in Europe.
  • all that distinguishes a ring species from two separate species is the existence of the connecting populations - if enough of the connecting populations within the ring perish to sever the breeding connection, the ring species becomes two distinct species.
  • Formally, the issue is that interfertile " is not a transitive relation – if A can breed with B,and B can breed with C, it does not follow that A can breed with C – and thus does not define an equivalence relation.
    A ring species is a species that exhibits a counterexample to transitivity.
  • References
    ^ Brown, Rob, "Same Species" vs. "Interfertile": concise wording can avoid confusion when discussing evolution, http://karmatics.com/docs/evolution-species-confusion.html 
    Alström, Per (2006): Species concepts and their application: insights from the genera Seicercus and Phylloscopus. ActaZoologicaSinica52(Supplement): 429-434. PDF fulltext
    Liebers, Dorit; de Knijff, Peter & Helbig, Andreas J. (2004): The herring gull complex is not a ring species. Proc. Roy. Soc. B271(1542): 893-901. doi:10.1098/rspb.2004.2679PDF fulltextElectronic Appendix
    Irwin, D.E., Irwin, J.H., and Price, T.D. (2001): "Ring species as bridges between microevolution and speciation." Genetica. 112-113: 223-243.
    Futuyma, D. (1998) Evolutionary Biology. Third edition. Sunderland, MA, Sinauer Associates.
    Moritz, C., C. J. Schneider, et al. (1992) "Evolutionary relationships within the Ensatinaeschscholtzii complex confirm the ring species interpretation." Systematic Biology 41: 273-291.