lesson 7 species

species

•The smallest biological unit that can evolve over time

(through its population(s))

phenotypic characters

•In practice, species are defined based on their

John S. Wilkins

has listed at least 26 different species concepts

Morphological species concept

•A species is a group of individuals that are morphologically

similar and clearly distinguishable from individuals of other

groups

typological species concept

Morphological species concept is also known as

morphological sc

•Species concept used on fossils

•Difficult to apply on species that are phenotypically

very plastic

Phenetic species concept

•A species is a group of individuals that are grouped together

based on overall similarity (numerical taxonomy); May be arbitrary

phenetic distance statistic

•Overall similarity in phenetic species concept is measured by a

 Biological species concept

•A species is a population or group of populations whose

members have the potential to interbreed and produce

fertile offspring

•Reproductive barriers

prevent gene flow between two different species

Geographical isolation

Live in different areas with

actual physical barrier

 Ecological isolation

Live in the same area but

different habitats

Temporal isolation

Different mating times

Behavioral isolation

No sexual attraction

Mechanical isolation

Incompatible mating

organs

Gametic isolation

Incompatible gametes

 Hybrid inviability

Hybrids do not survive; produced but fail to develop to reproductive maturity

Hybrid sterility

Hybrids do not produce functional gametes

Hybrid breakdown

Offspring of hybrids are weak or infertile; f1 hybrids are fertile but f2 gen fails to develop properly

Ring Species

made of a series of neighboring populations that can interbreed with neighboring related populations but not for distantly related populations usually at the end of the series

Hennigian species concept

defines species as lineage segments between two branching points

Cladistic species concept

defines species based on shared evolutionary ancestry rather than phenotypic similarity

Genealogical species conecept

defines species based on congruent patterns across multiple gene trees emphasizing genetic cohesion

chronospecies species concept

defines species based on gradual morphological changes over time in a single lineage

 Biological species concept

•Difficult to apply on organisms which are not known to

undergo sexual reproduction or where sexual barriers cannot

be determined

Recognition species concept

•A species is a group of organisms with a common method of

recognizing mates

•An offshoot of the biological species concept

•Suffers from the same limitations as the biological species

concept

Ecological species concept

•A species is a group of organisms exploiting the same

ecological niche

•Individuals may suffer from intra- and interspecific

competition

•Selection will favor extreme individuals in a population as

this will lessen the impact of competition

selection

•Biological species concept emphasizes on gene flow (or lack

thereof) whereas the ecological species concept emphasizes

on

Phylogenetic species concept

•A species is a cluster of organisms that represent a

genealogy or a lineage of descent; smallest discernible monophyletic unit

 phylogenetic tree

, also known as a tree of life or simply a phylogeny, describes

branching relationships among species, showing

which species shares its most recent common ancestor

with which other species.

•Parsimony

Species are arranged in a phylogeny such that

the smallest number of evolutionary changes is required.

Distance (or similarity.)

Species are arranged in a phylogeny such that each species is grouped with the other species that it shares the most characteristics with

Ring Species

considered to belong to the same species because they share a recent common ancestor

 Unified species concept

•Define species as separately evolving metapopulation

lineages or, more properly, segments thereof

•Metapopulation

inclusive population made up of several

connected subpopulations

•Lineage

ancestor-descendant series or a metapopulation

extended through time

7. Unified species concept

it provides a unified context for understanding the relevance

of diverse methods to the problem of species delimitation

(i.e., as methods for evaluating whether sets of populations

constitute separately evolving lineages) and thus also for

integrating the information provided by different species

delimitation methods in empirical applications

evolutionary species concept

defines species as lineages evolving separately with their own evolutionary roles and tendencies