Bio 3400 1nd Edition Lecture 18 Outline of Last Lecture I Synapomorphies II In class activity Candy bar phylogenetic trees Outline of Current Lecture I The Comparative Method II Testes size in bats III Speciation and History of Life IV Biological Species Concept V Phylogenetic Species Concept VI Speciation Current Lecture I II The Comparative Method a A method for studying selection and adaptation b Compares species or populations c Tests for patterns across species i Correlations among traits ii Correlations between traits and features of the environment d Shows what has happened in past evolution e One of the most common methods for studying adaptation f Types of questions i Are large testes in bats an adaptation for sperm competition ii What are the respiratory adaptations to living in burrows iii What adaptations are associated with an aquatic lifestyle in mammals iv Does a reduced basal metabolic rate evolve in desert living animals Testes Size in Bats a Male bat testes size varies widely across species 0 12 8 5 of body mass b In primates the range is 0 02 0 75 c Larger testes larger ejaculates d Larger groups increases multiple mating e Is group size related to testes size i Do group size and testes size evolve in tandem ii Need to take phylogeny into account f Accounting for Phylogeny i There is variation among species in bother group size and relative testes These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III IV V VI mass ii Not all bats with large testes mass or large group size are in the same clade iii Why do we need to account for phylogeny Unit 6 Speciation and History of Life a Species i A group of interbreeding populations that are evolutionary independent of other populations ii The smallest evolutionary independent unit independent evolutionary trajectory iii A group that evolves independent of other groups The Biological Species Concept a Species a group of interbreeding populations that are reproductively isolated from other groups b Reproductive isolation defines evolutionary independence c Species do not exchange genes with one another no gene flow d Problems i Not relevant to asexual populations ii Cannot be used for fossils iii Boundary is sometimes blurry 1 Example Salamanders in California 2 Hybrid zones woodpeckers e Video on salamanders in California i Sometimes breed with each other but the offspring usually do not survive ii Reproductively isolated from one another 1 Either cannot mate at all or hybrids are unable to mate and reproduce The Phylogenetic Species Concept a Species a group of populations forming a monophyletic group b Must of diverged genetically and morphologically enough to show synapomorphies c Problems i Requires substantial resources to implement to sample etc ii May double the number of named species e g cryptic species Speciation a Formation of two or more daughter species from a single ancestral species b Key component genetic isolation i Allopatric speciation 1 Geographically separated 2 Mechanism of genetic isolation physical isolation a Dispersal organisms relocate iguanas on a raft that get blown to an island i Example Hawaii and surrounding islands b Vicariance land erosion creating two new landmasses from one i Example Isthmus of Panama closed 3 MYA ii Shrimp have no way to get across ocean anymore VII VIII ii Parapatric 1 Sort of separated but not completely 2 Range of overlap iii Sympatric 1 Geographically identical Mechanisms of Divergence in Allopatry a Genetic drift typically smaller populations when starting out so have larger effect i Genetic divergence occurs quickly for this reason b Natural selection c No gene flow Sympatric Speciation a Mechanisms of genetic isolation in sympatry i Polyploidy and chromosome changes 1 Especially important in plants 2 Tetraploids and diploids cannot mate ii FOOD speciation due to shifts in host 1 Soapberry bugs and flat versus balloon pod trees iii SEX speciation due to divergent sexual selection b Signatures of sympatric speciation via host habitat shift i Sympatric overlap of host patches ii Mating on the host causes reproductive isolation between races iii Host phenology differs iv Divergent selection on different hosts habitats