EE Lecture 38: Adaptive Radiation Flashcards
why do some clades contain more species than others
faster speciation rate
slower extinction rate
older therefore had more time to accumulate
how many divergences did it take to lead to 85% vertebrate diversity
9
what percentage of diversity did 9 divergences take
85%
in a group at a given time since its origin, what does species richness depend on
the balance between speciation and extinction
give eqtn for noneqbm explanation of some clades containing more species than others
r = b - d
r: net diversification rate
b: speciation rate
d: extinction rate
what does fast life history in mammals lead to
faster evoln and rapid speciation, plus lower extinction rates
which selected species have faster net diversification rates
clades of r selected species
do K selected species have faster diversification rates than r selected species?
no
predict faster net diversification rates in clades of r selected species than in clades of K selected species
how does fast gestation affect extinction
fast gestations slows extinction
what is species richness in a clade limited by
oportunity eg space and ecological resources
discuss in terms of abiotic factors, why some clades have more species than others
groups with more species have
access to more resources - more niches
partition resources more finely -narrower niches
live in larger geographical regions
name a fossil that shows evidence that clades diversify towards limits
aquatic beetle
planktonic foraminifera
what do graphs of no.species vs. time (My) of planktonic foraminifera and aquatic beetle show?
that species/clades diversify towards limits
what is adaptive radiation
organisms diversifing into new forms
give some examples of adaptive radiation
Darwins Finches Carribbean Anoles Hawaiian honeycreepers Hawaiian silverswords Lake Baikal amphipods shrimps
how do Darwins finches shows adaptive radiation
13spp
3MYA
how do Carribean Anoles show adaptive radiation
c. 400 spp
how do Hawaiian honeycreepers show adaptive radiation
~50 spp
~4.5MY
how do Lake Baikal amphipods show adaptive radiation
~259spp
but Lake Baikal is an ancient lake = 28MYrs old
how is adaptive radiation initiated
ancestor arrives by chance onto enviro empty of competitors and diversified to fill an unusual range of niches
how do Hawaiian silverswords show adaptive radiation
lianes, trees, cushion plants, rosettes
28spp all within 5MY
give an example of non-adaptive radiation
plethodon salamanders
what is non-adaptive radiation
adapted for same niche but in different places
what is adaptive non-radiation
new adaptation but then diversification
evolnary dead ended
give an example of adaptive non-radiation
flying frogs
new adaptive zone, morphological and behavioural innovations
not a KEY innovation therefore evolnary dead ended - no diversification
what are the steps leading to adaptive radiation
- sources of ecological opportunity
- release from natural selection
- ecological release
- selection/ecological speciation/character displacement
- rapid speciation and morphological divergence
- adaptive radiation
what sources of ecological opportunity are there that could lead to adaptive radiation
key innovation
new habitat
antagonist extinction
what types of ecological release is there that could lead to ecological release
increased trait variance
density compensation
broader habitat or resource use
give details of a key innovation that could result in ecological release
- expanded niche space: nocturnal flight, echolocation
- partition more finely -Cichlid fish in African great lakes
give an example of fine niche partitioning
Cichlid fish in African great lakes
what is antagonist extinction
leaving behind - part of ecological opportunity
what is an adaptive landscape
a mountain
selection usually pushes pops to the top eg. mountain peak - fitness at the top
ecological release fills in adaptive valleys
evoln is less constrained therefore v. fast espesh with directional selection and character displacement
what is convergence
repeated radiations in same adaptive zone results in convergent patterns of diversity - separate diversification into similar ecomorphs
what does convergence provide evidence for1
that ecology drives diversification
define ecomorph
A local variety of a species whose appearance is determined by its ecological environment
what are vultures an example of
convergence
give an example of convergence
vultures
how do vultures show convergence
two groups of vultures, old world and new world
not especially closely related: separate origins of carrion-feeding
what is carrion feeding
eating dead and decaying flesh
what shapes diversification
niche differences and ecology
how do anolis lizards shows convergent - explain
anolis lizards in the Caribbean 6 ecomorphs that are present on all 4 large islands mixture of convergent evoln and dispersal between island -crown giant -twig -grass bush -trunk crown -trunk -trunkground
what do anolis lizards show
convergence
where are anolis lizards found
in the Caribbean
how many anolis ecomorphs are there
6, present on all 4 islands of the Caribbean
name the 6 ecomorphs of anolis lizards
crown-giant twig grass-bush trunk-crown trunk trunk-ground
what are the two main components of adaptive radiation
taxonomic diversification and ecological diversification
what is the key factor of adaptive radiation
ecological release
what may be the dominant mechanism for todays diversity
adaptive radiaton
what does convergence provide strong evidence for
that ecology drives diversification
