Bioee 1780 1st Edition Lecture 20 Outline of Last LectureI. Sexual selectionA) Sperm competitionB) General patterns of sexual selectionII. Sexual selection: the game showOutline of Current LectureI. Speciation videoII. SpeciesIII. Speciation A) Barriers of gene flowCurrent LectureI. Speciation video*What is a species? A group of potentially reproducing individuals that are reproductively isolated from other populations*How do new species arise? They face reproductive isolation, and evolve differently via natural and sexual selection-Allopatric speciation: geographic isolation resulting in speciation (they are often defined by genetics)-Sympatric speciation: speciation that occurs even when there is a geographic overlap*How did all the very different birds of paradise arise?-Fragmentation between islandsII. Species*Metapopulations: a connected series of populations that are isolated in space, but are connected by occasional gene flow*What is a species?-There is more than one answer, no one definition is accepted universally-However, the general idea is well understood by naturalists (paraphrased from Darwin) *Species concepts:-Phylogenetic species concept: focuses on the phylogenetic history of organisms, basically defined as the tip of a phylogenetic tree-Biological species concept: defines species as a group of actually or potentially interbreeding populations that are reproductively isolated from other groups (if they can successfully breed, they are the same species)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.#However, what about horses and donkeys?#Mules (the babies of this mix) are typically sterile#How about lions and tigers?#Ligers and Tigons also tend to be sterile-General lineage species concept: species are metapopulations of organisims that exchange alleles frequently -So which one of these is right? All? None? #No one definition will work for every taxaIII. Speciation*Whenever a species is dividing into two, there is an “in between” (there is a period where it is super ambiguous whether you have one or two species)-Why does this even matter? -Think about Florida panthers (low reproductive rate, probably due to inbreeding)-Potential solution: introduce panthers from another population-Do you know if they are the same species or notA) Barriers to gene flow*Geographic barriers (extrinsic)-Mountains, rivers, etc-Allopatric speciation-Example: snapping shrimp lived in an area where two seas were conjoined, eventually the Central American Peninsula arose, separating the population into two -Vicariance: geographic speciation from an arising barrier-Dispersal and colonization can also lead to speciation (for example: crickets on the Hawaiian islands; as the islands formed, there was occasional movement from one island to the other)*Reproductive barriers (intrinsic)*Why is sympatric speciation so rare?-If there is no geographical barrier, there is very little reason for the populations to become