Species concept Flashcards
how can species mirror each other?
via convergent evolution
adaptive radiation
- what is it?
organisms diversify rapidly from an ancestral species into a multitude of new forms
adaptive radiation
-example
fish in Lake Malawi + Lake Victoria both have different species occupying different niches
e.g. snail crusher, bottom feeder etc
People have struggled w/ defining species for many yr
-> but which is the most common?
biological species concept
Mayr’s biological species concept
groups of interbreeding populations which reproductively isolated from other such groups
Barriers to recombination
Adaptive barriers
= selection against hybrid genotypes
Mechanistic barriers
= factors promoting DNA specificity
(chromosomal incompatibility)
Ecological barriers
= consequence of physical separation of populations
Mechanistic barriers
- example
Horse + donkey = mule
- sterile hybrid
= pre-zygotic barrier
Ecological barriers
- example
Ring species
- 2 gull populations which don’t interbreed are living in the same region and connected by a geographic ring of populations that can interbreed
Fuzzy species
- Paper by?
- suggests?
Hanage et al (2005)
Bacteria don’t have discrete species clusters
MLST
- what is it?
Multilocus sequence typing
- characterises isolates of microbe species
using DNA sequences of internal fragments of multiple housekeeping genes
MLST
- of Campylobacter
sequenced 7 genes to understands variation in different strains
- revealed interspecies hybrids
-> some strains had genes attributable to C. jejuni + C.coli
= HGT
introgression
transfer of genetic information from 1 species to another
as a result of hybridisation between them + repeated backcrossing
de-speciation
if gene flow between 2 species maintained at a high rate
-> 2 species may come together
hybridisation has implications for…?
species concepts
adaptive radiation
hybridisation has implications for adaptive radiation
- example
Darwin’s finches on Galapagos
- adaptive radiation to fill the niches (food source)
if ecology changed
- > great increases in the no. of intermediate birds
- > enviro would then favour them instead