Species Flashcards
What is a species in biological taxonomy
the smallest required unit in formal classification: a group subordinate to genus, indicated by a Latinized binomial
What is the species problem
- the unresolved problem of determining what a species is
Explain species concept vs. definition
- species as a primary concept (=an abstract idea) the term “species” may be best understood by the way it is used
- a definition attempts to give a statement of the exact meaning
- concepts exist in our heads, definitions exist on paper
Describe species as an operational definition
- an operational definition defines things in terms of the processes or tests used to quantify them
-this is often viewed as positive, since it makes the application of terms more precise and repeatable - but under operationalism, a term like species might be defined so strictly that the usefulness of the definition is compromised
Can a single all encompassing species concept be developed
- under monism the answer is yes (a view that attributes oneness or singleness to a concept)
- under pluralism there can be multiple, incompatible concepts
Do species exist independently of peoples perceptions
realism says yes, nominalism says no (Darwin was a nominalist)
What are the 4 main species concepts/definitions
- Subjective clusters
- reproductive compatibility
- monophyly/diagnostibility
- Lineage concepts
What are the species concepts that fall under subjective clusters
- Typological/ taxonomic species concept = a group of similar individuals sharing the same “essence”, separated from others by a sharp discontinuity, constant through time and with strict limits to variation
- morphological cluster concept
- gene cluster concept
- these have no references to any particular process, they rely on morphological or genetic similarity, learned by applying he examples of previous taxonomists
- criticism: a species is what a good taxonomist says it is
What are the species concepts that look at reproductive compatibility
- biological species concept = a group of actually or potentially interbreeding natural populations, reproductively isolated from other such groups (most cited concept)
- recognition concept = the most inclusive set of individual biparental organisms that share a common fertilization system
- cohesion concept = the most inclusive group of organisms having the potential for genetic and or demographic exchangeability
- these are explicitly based on the process of interbreeding/ gene flow, implying
that reproductive isolation is what really matters - occasional hybridization remains a challenge – no precise criterion
- not operational for asexual organisms, or geographically separate
populations - rely on reproductive compatibility, which is plesiomorphic
In the biological species concept what is the challenge of ring species
A ring species is a situation in which two populations which do not interbreed are living in the same region and connected by a geographic ring of populations that can interbreed
Which species concepts are based on monophyly/diagnosibility
- Phylogenetic Species Concept(s) = variations developed by cladists in 1970s and 80s in response
to perceived shortcomings of BSC (biological species concept) - Apomorphy concept = a geographically constrained group of
individuals with some unique apomorphic characters - Monophyly concept = the smallest monophyletic group deemed
worthy of formal recognition - Diagnostic concept = smallest diagnosable cluster of individuals
within which there is a parental pattern of ancestry and descent - emphasis on determining monophyly, apomorphy
- ranking at species level remains poorly defined
- single lineage can become a new species without any divergence
- detection of an apomorphy in a population may require recognition as
a new species even with no hint of reproductive isolation - paraphyletic populations may not qualify as species
- application usually means proliferation of newly recognized species - TAXONOMIC INFLATION may occur
when the number of species is
elevated by changing to another
definition for species:
Which species concepts are based on lineage concepts
- Lineage Species Concepts – growing influence in last 20 years
= species are independent lineages
(lineage is an ancestral-descendant sequence of populations) - Evolutionary concept = a lineage evolving separately from others
and with its own evolutionary role and tendencies - Hennigian concept = species are unbranched segments or lineages
in an organismal phylogeny - Ecological concept = a lineage which occupies an adaptive zone
minimally different from that of any other lineage - emphasis on species as lineages not groups
- clearly allows change over time
- the “general lineage concept” says that all other concepts agree
that species are lineages, disagreeing only about what stage of lineage
divergence a species should be recognized a
Describe Genealogical species concept
exclusive groups of organisms, where
an exclusive group is one in which all
members are more closely related to
each other than to any organism outside
the group (= reciprocal monophyly)
describe Genomic Integrity Species Concept/ Definition
species are:
1) Populations that retain their genomic integrity upon contact
OR
2) Geographically separated populations that have genetic divergences at
least as great as populations that naturally contact each other.
Describe Typological/ taxonomic species concept
= a group of similar individuals sharing the same “essence”, separated from others by a sharp discontinuity, constant through
time and with strict limits to variation
