1 / 16

Speciation: the origin of species How many species? Number described: 1.5 – 1.6 million

Speciation: the origin of species How many species? Number described: 1.5 – 1.6 million Number estimated: 5-6 million to 100 million. Species: smallest evolutionarily independent unit (fundamental unit of biodiversity). Species boundaries geographical genetic How do species originate?

alissa
Download Presentation

Speciation: the origin of species How many species? Number described: 1.5 – 1.6 million

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Speciation: the origin of species • How many species? • Number described: 1.5 – 1.6 million • Number estimated: 5-6 million to 100 million. • Species: smallest evolutionarily independent unit (fundamental unit of biodiversity). • Species boundaries • geographical • genetic • How do species originate? • Speciation mechanisms

  2. Speciation mechanisms 1. Increasing number of sets of chromosomes A. Alloploidy: stage in the speciation process B. Autoploidy: doubling of homologous chromosomes results in fertility Hybridization very common in plants Species of tobacco Alloploidy Autoploidy

  3. Species 1 (unparental) Species 2 (biparental) • 1. Uncommon in animals • Increasing sets of chromosomes • Hybridization • Very rarely produces a new • species New species 3

  4. Attempts to recreate an animals species.Laboratory Hybridization Among North American Whiptail Lizards, Including Aspidoscelis inornata arizonae X A. tigris marmorata Squamata: Teiidae), Ancestors of Unisexual Clones in Naturecharles j. cole, laurence m. hardy, herbert c. dessauer, harry l. taylor,and carol r. townsendDivision of Vertebrate Zoology (Herpetology), American Museum of Natural History (cole@amnh.org).Division of Vertebrate Zoology (Herpetology), American Museum of Natural History; Museum of Life Sciences, Louisiana State University in Shreveport, LA 71115-2399 (lhardy@lsus.edu).Division of Vertebrate Zoology (Herpetology), American Museum of Natural History; Department of Biochemistry and Molecular Biology, Louisiana State University Health Science Center, New Orleans, LA 70112.Division of Vertebrate Zoology (Herpetology), American Museum of Natural History; Department of Biology, Regis University, Denver, CO (htaylor@regis.edu).Division of Vertebrate Zoology (Herpetology), American Museum of Natural History (townsend@amnh.org).

  5. Attempt to create a parthenogenetic species in the lab. • Attempt spanned a period of > 29 years • 74 males of four species caged with 156 females of nine species • Each group kept together for at least six months. • A total of only five hybrids from three crosses were obtained over the 29 years. • Hybrids were raised to adulthood to see if they would reproduce, but none did. • The hybrid status of suspected laboratory hybrids was confirmed by karyotypic, allozyme, and morphological analyses, and histological studies were made on reproductive tissues of the hybrids, which were apparently sterile. • Three laboratory hybrids of two bisexual species, A. inornata arizonae (♀) x A. tigris marmorata (♂)…..progenitor species of A. neomexicana. • These three individuals from one clutch of eggs were the only hybrids between two bisexual species that we obtained.

  6. Bisexual parents used in attempt to recreate the origin of Aspidoscelis neomexicana

  7. Hybrid intersex Hybrid male The attempted recreation, A. neomexicana

  8. typically messy • Speciation Mechanisms • Most animal speciation is visualized as lineage splitting. • Y • Darwinian idea: slow accumulation of genetic differences. • Another idea: big changes can occur rapidly from small changes in developmental pathways. • Basic speciation models require separation of gene pools. • 1. Dispersal: either setting up peripheral isolates or island hopping. • 2. Vicariance: population is subdivided by extraneous geological or climatic events. • 3. Habitat segregation

  9. DNA sequence divergence Morphological differences Reproductive isolation Snapping shrimp species Speciation by Vicariance Asynchronous closure (3 mya)

  10. Speciation by habitat isolation How many species of African elephants? Sample: 195 elephants from 21 populations Four genes sequenced – genetic distances used to construct a phylogeny Conservation implications Two species (using a phylogenetic species concept)

  11. Speciation by Dispersal Representative Hawaiian Drosophila diversity

  12. Speciation by dispersal Aspidoscelis carmenensis A. picta A. danheimae A. franciscensis A. espiritensis

  13. Speciation nearing completion? northwest Arizona Aspidoscelis tigris

  14. Sample 4 in the middle of a step cline. Phenotypically intermediate. Why? center

  15. Assortative mating?

More Related