Adaptive Radiations . . . Systematics meets Ecology . . . Future of Molecular Systematics 1. Biogeography 2. Ecology 3. Genomics Phylogeny Development Genetics Taxonomy Cytology Ecology Biogeography Morphology Ecology and phylogenetics intertwined when looking at the emergence of life forms on earth and their subsequent diversification Emergence of Life Forms • emergence of 3 domains of life with 6+ kingdoms Emergence of Life Forms • rise of major lineages of eukaryota - many of which we do not yet know how related
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Adaptive Radiations
. . . Systematics meets Ecology . . .
Future of Molecular Systematics
1. Biogeography
2. Ecology
3. Genomics Phylogeny
Development
Genetics
Taxonomy
Cytology
Ecology
Biogeography
Morphology
Ecology and phylogeneticsintertwined when looking atthe emergence of life formson earth and theirsubsequent diversification
Emergence of Life Forms
• emergence of 3 domains oflife with 6+ kingdoms
Emergence of Life Forms
• rise of major lineages ofeukaryota - many of which wedo not yet know how related
Emergence of Life Forms• movement of plants onto landand their subsequentdiversification
Ordovician-Devonian
Emergence of Life Forms
• and finally the rise and domination of flowering plants
Emergence of Life Forms
Emergence of flowering plants has two important facets:
1. Radiation - large number of species resulted
2. Adaptive - exploited incredible array ofecological strategies or niches
Adaptive Radiations
• in 130 my angiosperms dominatebiomes from tropical forests to arctictundra . . .
Adaptive Radiations• . . . rainfallgradients from thewettest to the mostarid habitats onearth . . .
Adaptive Radiations• . . . life forms from giant emergenttropical trees to the tiniest aquaticduckweeds . . .
Adaptive Radiations• . . . and exploited reproductive biology in elaborate outcrossingand seed dispersal methods to forgoing sex altogether via apomixisand parthenogenesis
Adaptive Radiations• Angiosperms show all necessarycharacteristics of an adapativeradiation
• Key innovation spurring thisadaptive radiation?
flowers? triaperturate pollen?vessels?
Variation in Lineage DiversityVariation in lineage diversity relates to the appearance of unequalnumbers of species in sister lineages
Besides some uniqueexceptions, the expectationis that sister lineagesshould show roughly equalnumbers of species - asthey are equal in age
What are the exceptions?
Variation in Lineage DiversityVariation in lineage diversity relates to the appearance of unequalnumbers of species in sister lineages
1. Differential extinction
One lineage (clade 1) ismore diverse simplybecause the other wasmaladapted perhaps to achanging environment
Variation in Lineage DiversityDifferential extinction is well known inthe fossil record:
6 great extinction eventsPleistocenemegafauna
Variation in Lineage DiversityDifferential extinction is well known inthe fossil record:
Diverse lycopods & horsetails in Carboniferous
Variation in Lineage DiversityVariation in lineage diversity relates to the appearance of unequalnumbers of species in sister lineages
2. Coevolution
One lineage (clade 2) ismore diverse because ofthe ability to co-evolve withother organisms
Variation in Lineage DiversityFlowering plants show remarkable abilityto co-evolve with other organisms: Pollination
Variation in Lineage DiversityFlowering plants show remarkable abilityto co-evolve with other organisms:
Chemical arm’s race
Phyllobrotica
Scutellaria
Variation in Lineage DiversityVariation in lineage diversity relates to the appearance of unequalnumbers of species in sister lineages
3. Adaptive radiation
One lineage (clade 2) ismore diverse due tocombination of speciesradiation and adaptationinto many ecological zonesperhaps due to the origin ofa novel feature
Adaptive Radiations“. . . species occasionally arriving after long intervals in a new andisolated district, and having to compete with new associates, willbe eminently liable to modification, and will often produce groupsof modified descendants” [Darwin, 1853]
Adaptive Radiations“. . . an isolated region, if large and sufficiently varied in itstopography, soil, climate and vegetation, will give rise to adiversified fauna according to the law of adaptive radiation fromprimitive and central types. Branches will spring off in alldirections to take advantage of every possible opportunity ofsecuring food.” [Osborn, 1900]
First use of termadaptive radiation
“ . . . an isolated region, if large and sufficiently varied in itstopography, soil, climate and vegetation, will give rise to adiversified fauna according to the law of adaptive radiation fromprimitive and central types. Branches will spring off in alldirections to take advantage of every possible opportunity ofsecuring food.” [Osborn, 1902]
Adaptive Radiations“. . . adaptive radiation strictly speaking refers to more or lesssimultaneous divergence of numerous lines all from much thesame ancestral adaptive type into different, also divergingadaptive zones.” [Simpson, 1953]
Issues in Adaptive Radiations• It is clear that few of the classic cases of adaptive radiationhave been studied rigorously from a combined systematic andecological point of view
Two main issues:
Issues in Adaptive Radiations1. The very characters whose diversification is being examined(e.g. beak size, shape, function in Darwin’s finches), can also beused to determine relationships and classify the organismspossessing them - potentially circular!
Issues in Adaptive Radiations2. Extreme convergence and divergence is likely in groups thatare undergoing adaptive radiations
Divergence: changes in homologous structuresamong related species; changes permit eachspecies to specialize in different environments
Convergence: changes in analogous structuresamong unrelated species; changes permit eachspecies to specialize in the same environment
Issues in Adaptive RadiationsThese two issues in studying adaptive radiations are bestaddressed by using an independent source of information -molecular phylogenetic characters
Phylogeny
Development
Genetics
Taxonomy
Cytology
Ecology
Biogeography
Morphology
Adaptive RadiationsIllustration of these problems with 3 examples of adaptiveradiation
Rift Valley CichlidsCichlids possess a double jaw system, the pharyngeal jaw isthought to be a key innovation for species proliferation anddivergence in feeding strategies
Lake Tanganyika Lake Malawi
• species with similar feedingstrategies between lakes related?• species showing different feedingstrategies within a lake related?
Rift Valley CichlidsCichlids possess a double jaw system, the pharyngeal jaw isthought to be a key innovation for species proliferation anddivergence in feeding strategies
Lake Tanganyika Lake Malawi
• divergence within each lake!
mtDNA tree
• convergence between lakes!
Salvia Staminal LeverThe giant genus Salvia (Lamiaceae) possesses two stamens withelongated connective tissue
Salvia Staminal LeverPosterior thecae abort, fuse, and can form a lever device
p
a
Salvia4 stamens 2 stamens connectives
Salvia Staminal LeverThe resulting staminal lever has been regarded as a keyinnovation for the species diversification in Salvia viapollination shifts
What does molecular phylogenetics indicate?
Jay Walker _ UW Grad
Salvia Staminal Lever• Salvia is polyphyletic with 3separate lineages of “Salvia”each sister to other generawithout elongated connective
• lever mechanism correlatedwith significant speciesdiversification each time itevolved relative to sisterlineages - key innovation!
250 spp.
500 spp.
90 spp.
• lever mechanism evolvedconvergently 3 times
lever mechanism
Hawaiian Island RadiationsIsolated, oceanic islands provide some of the most classic examplesof adaptive radiation
• isolation - once youget there, you can’tgo back
• great ecologicaldiversity - manyniches to exploit2 volcanic
ridges
NE trade winds
• low diversity -many niches open
• low competition,predation, herbivory- you can bedifferent
Hawaiian Island RadiationsIsolated, oceanic islands provide some of the most classic examplesof adaptive radiation
• archipelago is aseries of geologicallydated islands• fixed volcanichotspot but Pacificplate conveyor belt
Hawaiian Island RadiationsIsolated, oceanic islands provide some of the most classic examplesof adaptive radiation
• older to youngerislands allow fordispersalbiogeographicalanalysis
Hawaiian Island RadiationsBest studied group is the Hawaiian silversword complex
Phylogenetics, cytology,biogeography, ecology,physiology, hybridization,evolution
Silverswords
N
Kauai-11 endemic
Oahu-2 endemic
Maui Nui-7 endemic
Hawaii-3 endemic
Wilkesia gymnoxiphiumDubautia paleata Argyroxiphium
sandwicense
Plus 5 indigenous species
Tarweed (California USA) OGDubautia paleata KauaiDubautia waialealae KauaiDubautia laxa indigenousWilkesia gymnoxiphium KauaiWilkesia hobdyi KauaiArgyroxiphium caliginis MauiArgyroxiphium grayanum MauiArgyroxiphium virescens MauiArgyroxiphium sanwicense M&HArgyroxiphium kauense Hawaii
Silversword Cladogram (simplified)
Hawaiian Island Radiations
oldest
youngest island
5.2 myaestimate
Hawaiian LobeliadsWhy the Hawaiian lobeliads?
• largest group: 6genera, 115 species)• 1/9th of nativeflora• considered derivedfrom 3-5 separatecolonizations• phenomenalvariation in habitat,life form, flowers,and fruits
Hawaiian LobeliadsWhy the Hawaiian lobeliads?
• appear to have co-evolved with theendemic Hawaiianhoneycreepers
Hawaiian LobeliadsWhy the Hawaiian lobeliads?
• appear to have co-evolved with theendemic Hawaiianhoneycreepers• honeycreepersrepresent a separateadaptive radiation
Lobelia gloria-montis
Lobelia telekii - Mt. Kenya
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Brighamii
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Delissia
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Trematolobelia
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Clermontia
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Cyanea
Hawaiian LobeliadsWhat are the Hawaiian lobeliads?
Hawaiian LobeliadsThe Hawaiian lobeliads represent a single (not 5) lineage/colonization!
Givnish et al. 2009
Hawaiian LobeliadsThe Hawaiian lobeliads are an even more spectacular adaptive radiation
Hawaiian LobeliadsRemarkable divergent andconvergent character evolution- but fruit color is perfectlyconsistent with relationships
Hawaiian LobeliadsTwo clock calibrations - usingAsterid fossils or usingHawaiian Island ages - place thedifferentiation of Hawaiianlobeliads at 12-13 mya
Hawaiian LobeliadsTwo clock calibrations - usingAsterid fossils or usingHawaiian Island ages - place thedifferentiation of Hawaiianlobeliads at 12-13 mya
Original colonist arrived inGardner Pinnacles - largevolcanic islands 12-13 mya
Lobeliads are one of the oldest radiations of extant Hawaiian biota – buttheir honeycreeper pollinators would not arrive for another 7-9 my (oh-oh!)
Hawaiian LobeliadsBut . . . a recent paper shows that the 5recently extinct Hawaiian Honeyeaters – andthought to be recently derived fromAustralAsian Honeyeaters – are in fact 14-17my old and derived from an American clade -waxwings, silky flycatchers, and palm chats
Hawaiian lobeliads13-14 mya
Hawaiian Honeycreepers7 mya
Fleischer et al. 2008
Hawaiian Lobeliads
• Early lobeliads hadinitial radiation withHawaiian honeyeaters
• later radiation of twolarge genera (Cyanea andClermontia) pimarily withHawaiian honeycreepers
Hawaiian Lobeliads
Adaptive Radiations
. . . Systematics meets Ecology . . .
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