Class Notes (810,430)
Canada (494,121)
Biology (1,278)
BIOL 103 (249)

Species and Speciation.docx

4 Pages
Unlock Document

Queen's University
BIOL 103
Peter T Boag

Species and Speciation - Finch speciation via dispersal and adaptation o Allopatric model of finch speciation says species diverge on different islands (allopatry) and eventually coexist on same island (sympatry) o Step 1: immigrants from mainland colonize Galapagos o Step 2: can occur repeatedly as birds disperse to other islands and adapt to local foods – genetic drift also likely o Step 3: birds recolonize island where their ancestors lived; if sufficiently distinct, have two species, otherwise merge back into single species - How are species formed? o Gradually in situ or by more rapid division of ancestral population o Usually allopatric, sometimes in sympatry - How do species persist? o Gene flow reduced by ‘RIMa’ - Variation within and between groups of organisms is common - Morphospecies were the traditional way of describing species, going back to the Latin naming system created by Swedish biologist Carl Linnaeus in the mid 1700s o Works where clear groups are defined by reliable characters o ‘Monkeyflow’ species of the genus Mimulus share distinct floral morphology and other traits associated with their preferred pollinators and habitats - Morphospecies concept not so useful for species with lots of intraspecific variation; but if variants can freely interbreed in nature and produce fertile offspring they can be described by the ‘biological species concept’ championed by Ernst Mayr in the 1960’s o All dog varieties belong to the species Canis lupus familiaris a subspecies of the gray wolf o Related species such as African jackals like Canis adustus don’t naturally interbreed with dogs due to geographic or genetic isolation - Increased availability of objective markers of shared common ancestry from molecular sequences have increased the popularity of the ‘phylogenetic species concept’ o There are isolated populations of elephants on 2 continents, but the phylogenetic species concept confirms no more and no less than three species – populations within each species are too similar to form distinct branches - Different species concepts each have strengths and weaknesses – more than one may be useful depending on context and question Species concept Criterion Advantages Disadvantages Morphological Anatomical Widely applicable Subjective difference Biological Reproductive Based on Not applicable to isolation evolutionary asexual species independence and fossils Phylogenetic Smallest Widely applicable, Few phylogenies phylogenetic group testable available - Speciation o Population becomes reproductively isolated o Separated gene pools diverge, due to genetic drift and local adaptation o Genetic exchange stops, new lineages go their independent evolutionary ways - The most common mode for speciation involved isolation of subpopulations in allopatry o Allopatric speciation (physical isolation) o Sympatric speciation - Fish separated by isthmus 3.5 years ago diverged into two species by genetic drift and adaptation to Atlantic vs. Pacific conditions - Speciation and ‘RIMs’ o RIM: Reproductive Isolating Mechanisms o Preventing gene flow between species o Postzygotic barriers evolve first  Two new species may have slightly different chromosome numbers or otherwise incompatible genomes  Morality or sterility after fertilization is more likely in recent derived species  Wastes resources if common, so selected against o Prezygotic b
More Less

Related notes for BIOL 103

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.