BIOL 2040 Lecture Notes - Lecture 14: United States Fish And Wildlife Service, Species Problem, Eastern Wolf
3 May 2018
School
Department
Course
Professor
Speciation
Nov 26-Dec 3, 2015
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• Nov 26
Biological Species Concept (BSC)
• Species are actually or potentially interbreeding natural populations, which are reproductively
isolated from other such groups
• Advantages:
o Reproductive isolation means lack of gene flow
o Testable
o Immediately defines research program
• Disadvantages:
o Can be difficult to apply when populations don’t overlap
o Asexual organisms (bacteria, archae, some eukaryotes)
o Impossible to apply to fossil forms
Phylogenetic Species Concept (PSC)
• Monophyletic groups (A-G are distinct species)*different letters = different species
• Advantage:
o Testable (statistical significance of tree)
• Disadvantage:
o Where do they stop splitting? Proliferation of species
Morphospecies Concept (MSC)
• Species are delimited based on phenotypic differences
• Advantage:
o Widely Applicable
• Disadvantages:
o Meaning?
o How testable?
o Reproductively isolated groups can look alike (fungi, bacteria, archaea, and many
eukaryotes)
Applying Species Concepts
• Marine phytoplankton – Pesudo-nitzchia
o Diatoms
o Algal blooms
o Produce domoic acid – a neutotoxin that can accumulate in shell fish
o 2 morphospecies based on light microscopy, especially how cells line up
Agreement among species concepts
• Morphological
o Based on: light microscopy; transmission electron microscopy
• Phylogenetic
o Based on: rcbL gene tree
• Biological
o Based on mating trials
The Red Wolf and Eastern Canadian Wolf
• 2 major lineages
• Based on 8 microsatellite loci
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• If absolute isolation was required for species rcognition, all North American wolves (and coyotes)
would be considered one species
o Linked by evidence of interbreeding
The Great Lakes Wolf:
• Genetic Information:
o mtDNA (maternal)
o Y-chromosome, haplotypes (paternal)
o Autosomal DNA
• Conclusions:
o Unique population of gray wolves
o Ancient and recent introgression mtDNA and Y-chromosome of both the coyote and western
gray wolf
• Larger Analysis:
o 1. Methods
▪ canids worldwide
▪ 48,000 loci (Single nucleotide polymorphism)
o 2. Conclusions
▪ western wolf in North America is pure gray wolf
▪ See table of relatedness
▪ Coyotes colonized in Northeastern NA in the last 60 yeards
• Synthesis:
o 4 species of Canis in NA:
▪ C. lupus – Gray Wolf
▪ C. lycaon – Eastern wolf
▪ C. rufus – Red Wolf
▪ C. latrans – coyote
• Public Policy:
o Canada:
▪ The Eastern Wolf—Canis lycaon—is designated as a "Species of Special Concern" by
the Commi[ee on the Status of Endangered Wildlife in Canada (COSEWIC).
o USA:
▪ US Fish & Wildlife Service: red wolf—Canis rufus—is an endangered sp. The red
wolf is one of two species of wolves in the world…
Species Concepts – Summary
1. Biological
species are actually or potentially interbreeding natural populations, which are
reproductively isolated from other such groups-- Ernst Mayr, 1942
2. Phylogenetic
Tree tips
3. Morphospecies
Phenotypic similarities
There are three types of speciation based on geography:
1. Allopatric – physical separation
-part of the population becomes isolated
-2 populations experience different selection and/or rgd
-populations diverge in traits under selection and in genetically correlated traits
-if recontact:
A. Reinforcement of reproductive isolation OR
B. Merge back into one species
2. Parapatric – two populations contiguous at margin
-
3. Sympatric –
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Geographic Isolation:
1. Dispersal – migrate to another area (ex. To an island)
2. Vicariance – land form/water separates population
Isolation by dispersal: example
• Hawaiian Drosophilids; ~1000 species
• Changes in the species from the older island to the younger island
• Predictions of the dispersal-and-colonization hypothesis:
1. Closely related species inhabit adjacent islands
2. Branching sequence matches island formation
Support for Founder Hypothesis:
• The younger islands support more recent lineages
• The older islands contain organisms from the more ancient lineages
Speciation II
1. Mechanisms of genetic isolation
• Geographic:
o Isolation by vicariance:
▪ Ex. Isthmus of Panama
• Completion of closure: 3.1-3.5 mya
• An isthmus is a narrow strip of land with water on either side than
connects to two larger bodies of land
• Has a huge effect of the world
• Different distributions of animals (North-South)
• Land was lifted up above sea level two plates overlap
• Land split populations of species
▪ Snapping Shrimp
• Alpheus malleator
• Morphospecies concept: 7 pairs of sister species one on each side of
isthmus)
• Further study:
o PSC – DNA phylogeny
o BSC – tests of both mating and fertility of progeny
▪ Order of origin of species follows formation of a land bridge
o Vicariance events split a species distribution and reduce gene flow
• Chromosomal
o Polyploidy – change in the number of chromosome sets
▪ Autopolyploidy – within a species
▪ Allopolyploidy – different species
▪ Potential males of a new polyploidy is very limited
• Self fertilization
• Other similar polyploidy individuals if they exist
▪ *Therefore, a tetraploid (4N) must mate via selfing if there isn’t another
tetraploid
▪ If new polyploidy is successful, nearly instantaneous sympatric speciation
o Potential advantages of polyploidy:
▪ Immediate:
1. Cell Size
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