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Future of Molecular Systematics
Adaptive Radiations
. . . Systematics meets Ecology . . .
Emergence of Life Forms
• emergence of 3 domains of
life with 6+ kingdoms
1. Biogeography
2. Ecology
Ecology
Biogeography
3. Genomics
Morphology
Ecology and phylogenetics
intertwined when looking at
the emergence of life forms
on earth and their
subsequent diversification
Genetics
Phylogeny
Development
Taxonomy
Cytology
Emergence of Life Forms
• rise of major lineages of
eukaryota - many of which we
do not yet know how related
Emergence of Life Forms
Emergence of Life Forms
• movement of plants onto land
and their subsequent
diversification
• and finally the rise and domination of flowering plants
Ordovician-Devonian
Emergence of Life Forms
Adaptive Radiations
Emergence of flowering plants has two important facets:
1.
Radiation - large number of species resulted
2. Adaptive - exploited incredible array of
ecological strategies or niches
• in 130 my angiosperms dominate
biomes from tropical forests to arctic
tundra . . .
Adaptive Radiations
• . . . rainfall
gradients from the
wettest to the most
arid habitats on
earth . . .
Adaptive Radiations
• . . . and exploited reproductive biology in elaborate outcrossing
and seed dispersal methods to forgoing sex altogether via apomixis
and parthenogenesis
Adaptive Radiations
• . . . life forms from giant emergent
tropical trees to the tiniest aquatic
duckweeds . . .
Adaptive Radiations
• Angiosperms show all necessary
characteristics of an adapative
radiation
• Key innovation spurring this
adaptive radiation?
flowers? triaperturate pollen?
vessels?
Variation in Lineage Diversity
Variation in Lineage Diversity
Variation in lineage diversity relates to the appearance of unequal
numbers of species in sister lineages
Variation in lineage diversity relates to the appearance of unequal
numbers of species in sister lineages
Besides some unique
exceptions, the expectation
is that sister lineages
should show roughly equal
numbers of species - as
they are equal in age
1. Differential extinction
One lineage (clade
(clade 1)
1) is
more diverse simply
because the other was
maladapted perhaps to a
changing environment
What are the exceptions?
Variation in Lineage Diversity
Differential extinction is well known in
the fossil record:
6 great extinction events
Pleistocene
megafauna
Variation in Lineage Diversity
Differential extinction is well known in
the fossil record:
Diverse lycopods & horsetails in Carboniferous
Variation in Lineage Diversity
Variation in lineage diversity relates to the appearance of unequal
numbers of species in sister lineages
Variation in Lineage Diversity
Flowering plants show remarkable ability
to co-evolve with other organisms: Pollination
2. Coevolution
One lineage (clade
(clade 2)
2) is
more diverse because of
the ability to co-evolve with
other organisms
Variation in Lineage Diversity
Flowering plants show remarkable ability
to co-evolve with other organisms:
Chemical arm’
arm’s race
Scutellaria
Variation in Lineage Diversity
Variation in lineage diversity relates to the appearance of unequal
numbers of species in sister lineages
3. Adaptive radiation
One lineage (clade
(clade 2)
2) is
more diverse due to
combination of species
radiation and adaptation
into many ecological zones
perhaps due to the origin of
a novel feature
Phyllobrotica
Adaptive Radiations
Adaptive Radiations
“. . . species occasionally arriving after long intervals in a new and
isolated district, and having to compete with new associates, will
be eminently liable to modification,
modification, and will often produce groups
of modified descendants”
[Darwin, 1853]
descendants”
“. . . an isolated region, if large and sufficiently varied in its
topography, soil, climate and vegetation, will give rise to a
diversified fauna according to the law of adaptive radiation from
primitive and central types. Branches
B ranches will spring off in all
directions to take advantage of every possible opportunity of
food.”
1900]
securing food.
[Osborn, 1902]
food.”
First use of term
adaptive radiation
Adaptive Radiations
“. . . adaptive radiation strictly speaking refers to more or less
simultaneous divergence of numerous lines all from much the
same ancestral adaptive type into different, also diverging
adaptive zones.
[Simpson, 1953]
zones.”
Issues in Adaptive Radiations
• It is clear that few of the classic cases of adaptive radiation
have been studied rigorously from a combined systematic and
ecological point of view
Two main issues:
Issues in Adaptive Radiations
Issues in Adaptive Radiations
1. The very characters whose diversification is being examined
(e.g. beak size, shape, function in Darwin’
Darwin’s finches), can also be
used to determine relationships and classify the organisms
possessing them - potentially circular!
circular!
2. Extreme convergence and divergence is likely in groups that
are undergoing adaptive radiations
Divergence:
Divergence: changes in homologous structures
among related species; changes permit each
species to specialize in different environments
Convergence:
Convergence: changes in analogous structures
among unrelated species; changes permit each
species to specialize in the same environment
Issues in Adaptive Radiations
These two issues in studying adaptive radiations are best
addressed by using an independent source of information molecular phylogenetic characters
Ecology
Biogeography
Morphology
Genetics
Phylogeny
Development
Taxonomy
Cytology
Adaptive Radiations
Illustration of these problems with 3 examples of adaptive
radiation
Rift Valley Cichlids
Rift Valley Cichlids
Cichlids possess a double jaw system, the pharyngeal jaw is
thought to be a key innovation for species proliferation and
divergence in feeding strategies
Cichlids possess a double jaw system, the pharyngeal jaw is
thought to be a key innovation for species proliferation and
divergence in feeding strategies
mtDNA tree
• species with similar feeding
strategies between lakes related?
• species showing different feeding
strategies within a lake related?
• divergence within each lake!
lake!
• convergence between lakes!
Lake Tanganyika
Lake Malawi
Salvia Staminal Lever
The giant genus Salvia (Lamiaceae) possesses two stamens with
elongated connective tissue
Lake Tanganyika
Lake Malawi
Salvia Staminal Lever
Posterior thecae abort, fuse, and can form a lever device
a
p
4 stamens
2 stamens
connectives
Salvia
Salvia Staminal Lever
The resulting staminal lever has been regarded as a key
innovation for the species diversification in Salvia via
pollination shifts
What does molecular phylogenetics indicate?
Jay Walker _ UW Grad
Salvia Staminal Lever
lever mechanism
250 spp.
500 spp.
90 spp.
Hawaiian Island Radiations
Isolated, oceanic islands provide some of the most classic examples
of adaptive radiation
• isolation - once you
get there, you can’
can’t
go back
NE trade winds
2 volcanic
ridges
• great ecological
diversity - many
niches to exploit
• low diversity many niches open
• low competition,
predation, herbivory
- you can be
different
• Salvia is polyphyletic with 3
separate lineages of “Salvia”
each sister to other genera
without elongated connective
• lever mechanism evolved
convergently 3 times
• lever mechanism correlated
with significant species
diversification each time it
evolved relative to sister
lineages - key innovation!
Hawaiian Island Radiations
Isolated, oceanic islands provide some of the most classic examples
of adaptive radiation
• archipelago is a
series of geologically
dated islands
• fixed volcanic
hotspot but Pacific
plate conveyor belt
Hawaiian Island Radiations
Isolated, oceanic islands provide some of the most classic examples
of adaptive radiation
Hawaiian Island Radiations
Best studied group is the Hawaiian silversword complex
Phylogenetics, cytology,
biogeography, ecology,
physiology, hybridization,
evolution
• older to younger
islands allow for
dispersal
biogeographical
analysis
Silverswords
Hawaiian Island Radiations
Kauai-11 endemic
Silversword Cladogram (simplified)
Oahu-2 endemic
Wilkesia gymnoxiphium
Dubautia paleata
Maui Nui-7 endemic
Hawaii-3 endemic
Argyroxiphium
sandwicense
N
5.2 mya
estimate
oldest
youngest island
Plus 5 indigenous species
Tarweed (California USA) OG
Dubautia paleata Kauai
Dubautia waialealae Kauai
Dubautia laxa indigenous
Wilkesia gymnoxiphium Kauai
Wilkesia hobdyi Kauai
Argyroxiphium caliginis Maui
Argyroxiphium grayanum Maui
Argyroxiphium virescens Maui
Argyroxiphium sanwicense M&H
H
Argyroxiphium kauense Hawaii
Hawaiian Lobeliads
Why the Hawaiian lobeliads?
Hawaiian Lobeliads
Why the Hawaiian lobeliads?
• largest group: 6
genera, 115 species)
• 1/9th of native
flora
• considered derived
from 3-5 separate
colonizations
• phenomenal
variation in habitat,
life form, flowers,
and fruits
Hawaiian Lobeliads
Why the Hawaiian lobeliads?
• appear to have coevolved with the
endemic Hawaiian
honeycreepers
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
• appear to have coevolved with the
endemic Hawaiian
honeycreepers
• honeycreepers
represent a separate
adaptive radiation
Lobelia gloria-montis
Lobelia telekii - Mt. Kenya
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
Brighamii
Delissia
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
Clermontia
Trematolobelia
Hawaiian Lobeliads
What are the Hawaiian lobeliads?
Hawaiian Lobeliads
The Hawaiian lobeliads represent a single (not 5) lineage/colonization!
Cyanea
Givnish et al. 2009
Hawaiian Lobeliads
The Hawaiian lobeliads are an even more spectacular adaptive radiation
Hawaiian Lobeliads
Remarkable divergent and
convergent character evolution
- but fruit color is perfectly
consistent with relationships
Hawaiian Lobeliads
Hawaiian Lobeliads
Two clock calibrations - using
Asterid fossils or using
Hawaiian Island ages - place the
differentiation of Hawaiian
lobeliads at 12-13 mya
Two clock calibrations - using
Asterid fossils or using
Hawaiian Island ages - place the
differentiation of Hawaiian
lobeliads at 12-13 mya
Original colonist arrived in
Gardner Pinnacles - large
volcanic islands 12-13 mya
Hawaiian Lobeliads
Hawaiian Lobeliads
Lobeliads are one of the oldest radiations of extant Hawaiian biota – but
their honeycreeper pollinators would not arrive for another 7-9 my (oh-oh!)
But . . . a recent paper shows that the 5
recently extinct Hawaiian Honeyeaters – and
thought to be recently derived from
AustralAsian Honeyeaters – are in fact 14-17
my old and derived from an American clade waxwings, silky flycatchers, and palm chats
Hawaiian lobeliads
13-14 mya
Hawaiian Honeycreepers
7 mya
Fleischer et al. 2008
Hawaiian Lobeliads
Adaptive Radiations
. . . Systematics meets Ecology . . .
• Early lobeliads had
initial radiation with
Hawaiian honeyeaters
• later radiation of two
large genera (Cyanea and
Clermontia) pimarily with
Hawaiian honeycreepers