sp. 1: species concepts Flashcards
What role does identification of organisms as “species” play in bio, inc. evolutionary?
Describe species concepts, how they map onto a diagram of population divergency
def/description of 5 species concepts, strengths/weaknesses, how they compary
real world application of species concepts
Species Concept
a set of ideas about what a species could represent, how they can be recognized as a species
Why are species concepts important?
Test our understanding of evolution
diversity of evolutionary processes that are involved in the origin and maintenance of groups of organisms therefore dangerous to use a singular method to define species
Biological Species Concept (BSC)
Groups of actually or potentially interbreeding populations of organisms that are reproductively isolated from other such groups
What does it mean to call something a species
Name species to communicate with each other - convenience for humans
*suggests that no real discontinuities in nature, but there are
To allow us to know what properties they share
*ex. all Rhinolophus blasii have an echolocation freq of 92.21 - 98.16 kHz
Signal something about current properties (ex ability to interbreed)
How do we test for interbreeding?
Not always physical separation, sometimes temporal
5 Species Concepts of Focus
- Biological Species Concept (BSC)
- Phylogenetic Species Concept (PSC)
- Genotypic Cluster Species Concept (GCSP)
- Ecological Species Concept (ESC)
- Retrospective Reproductive Community Concept (RRCC)
Cohesive Processes
reproductive, ecological, and geographical-processes that can bind sets of populations together
forces that establish and reinforce boundaries between species
Selection pressures, similar traits, similar genetic histories, gene flow, interbreeding
Things they experience that make them distinct species
Non-Cohesive Process approach
- focus on traits that distinguish different species
- history of connections among individuals and populations
3 categories of species concepts
- reproductive communities (BSC)
- genealogical group (genetic history) (PSC)
- trait sharing clusters (GCSP, ESC)
What is consistent through species concepts?
Existence of reproductive communities
Strengths of BSC
Strength: provides clear criteria and expectations for “good species”. Good species don’t interbreed, levels of gene flow can be measured, and lack of gene flow leads to diff in traits.
Weaknesses of BSC
Weakness: not relevant to asexually reproducing species/lineages
potential vs actual interbreeding - geographical barrier reduces gene flow, but COULD still reproduce
How do we measure reproductive isolation? Mating trials? neutral markers?
Does reproductive isolation need to be absolute to define biological species?? are they still diff species if hybridization is sometimes/rarely possible
**does this mean application of BSC a matter of judgement?
focuses on current intrinsic ability to interbreed, but characteristics of organisms were shaped by processes of the past
Allopatric Speciation
Physical barrier reduces gene flow
Hybridization and BSC
can by hybridization between good species as long as it doesn’t result in the collapse of species.
Phylogenetic Species Concept (PSC)
Describes species based in part on monophyly
Monophyly alone isn’t enough to define a species
Also req synapomorphies
Species = populations of lineages at the tips of the tree of life, unitedy by ongoing evolutionary processes
Synapomorphies
Shared derived traits
Strengths of PSC
Applies to sexual and asexual
clear criteria
applies to fossil taxa
makes use of abundant genetic data
Challenges of PSC
in regards to monophyly, what distinguishes a species from other taxonomic levels or populations?
which genetic markers are informative/will help us distinguish btwn species? - type and magnitude of genetic differences
must assume cohesive processes binding loci to have partially shared histories
Genotypic Cluster Species Concept (GCSC)
Focuses on genotypic/phenotypic difference between populations at this time
Describes multiple non-hybridizing species in the same geographic area
Linkage disequilibrium has evolved in different populations to make them genetically different/more similar to ind. in same population
clusters of genotypes circumscribed by gaps in the range of possible multilocus genotypes btwn them - species have distinct trait clusters
Sympatric species
clusters of genotypes circumscribed by gaps in the range of possible multilocus genotypes btwn them - species have distinct trait clusters
Strengths of GCSC
takes advantage of population genetic and genomic data
Incorporates evidence for maintenance of distinct gene pools in face of potential or actual gene flow
Challenges of GCSC
Asexual lineages
Levels of differentiation - are populations different from species? if little gene flow btwn populations
Ecological Species Concept (EcSC)
a species is a lineage which occupies an adaptive zone minimally different from that of any other lineages in its range and which evolves separately from all lineages outside its range
adapted to landscape differently than others in area - ECOLOGICAL NICHE
Maps to tips of lineage (actual populations right now), but also impact of gene flow etc as lineages change to adapt to their environment
Strengths EcSC
applied to sexual and asexual
recognizes importance of ecology/adaptation in limiting gene flow
Challenges of EcSC
Unclear just how different niches have to be, to call all sets of pops distinct species
What makes a good species concept?
explain discontinuities among lineages
clear and consistent set of criteria
allow for variation in the ways which species arise and persist
helps understand how evolution produces diversity
encompasses diverse ways of being a species
Retrospective Reproductive Community Concept
provides flexibility that other concepts don’t have
relatively vague, no clear criteria
species we see today are consequences of reproductive communities of the past
RRCC = BSC + _____
all factors, retrospectivd
RRCC = PSC + ______
processes that led to differences
