Transcript Hawaiian Violets - Ohio University

EVOLUTION
OF THE HAWAIIAN VIOLETS (VIOLA)
HARVEY E. BALLARD, JR.
Department of Environmental and Plant
Biology, and
Molecular and Cellular Biology Program, Ohio
University
EVOLUTION OF THE HAWAIIAN VIOLAS
 Evolutionary relationships of
Hawaiian violets
 Relationships among
Hawaiians, Diversification
and Inter-Island Dispersal
 Adaptive Radiation
 Biogeographic Source and
Mechanism
GROWTH HABITS OF HAWAIIAN VIOLAS
treelet/tall shrub
(V. tracheliifolia)
erect shrub
(V. chamissoniana,
creeping herb/subshrub
(V. kauaensis, V. maviensis)
V. robusta, V. oahuensis,
V. waialenalenae)
QUESTIONS ABOUT HAWAIIAN VIOLAS
What does DNA data reveal about
the origin and relationships of the
Hawaiian violets that morphology
cannot?
Does the evolutionary pattern of
the Hawaiian violets conform to
the “progression rule”?
QUESTIONS ABOUT HAWAIIAN VIOLAS
What typical features of an
“adaptive radiation” are
demonstrated by Hawaiian
violets?
How did the ancestral seed get
from the Arctic to Kauai?
EVOLUTION OF THE HAWAIIAN VIOLAS
 Evolutionary relationships of
Hawaiian violets
 Relationships among
Hawaiians, Diversification
and Inter-Island Dispersal
 Adaptive Radiation
 Biogeographic Source and
Mechanism
PHYLOGENETIC TREE
FROM DNA SEQUENCE
DATA FOR
GENUS VIOLA
WORLDWIDE
•Hawaiians not
basal w/Latin
Americans
•Hawaiians form a
“natural” group
•Nearest relative is
Viola langsdorffii
PREVIOUSLY
HYPOTHESIZED
RELATIVES OF THE
HAWAIIAN VIOLAS
Viola kauaensis
Viola rubella
Viola tracheliifolia Viola waialenalenae
Viola stipularis
NEW DNA EVIDENCE--ARCTIC TUNDRA BOG VIOLET, VIOLA
LANGSDORFFII, IS NEAREST RELATIVE TO THE HAWAIIAN
VIOLAS!!
•Northern Pacific
rather than Latin
American origin
for Hawaiians
•Herbaceous
rather than woody
ancestry
•Wetland origin
EVOLUTION OF THE HAWAIIAN VIOLAS
 Evolutionary relationships of
Hawaiian violets
 Relationships among
Hawaiians, Diversification
and Inter-Island Dispersal
 Adaptive Radiation
 Biogeographic Source and
Mechanism
PHYLOGENETIC TREE
FROM DNA SEQUENCE
DATA FOR HAWAIIAN
AND RELATED VIOLAS
•Branch lengths
shorter in Hawaiian
violets than others
in related groups
•Short basal
branches in
Hawaiiansabrupt
diversification
PHYLOGENETIC TREE
SHOWING ISLAND
DISTRIBUTIONS AND
HABITATS OF HAWAIIAN
VIOLAS
•Basal species
diversified on Kauai
•Arctic bog violet
yielded first dry-land,
then wet-land plants
•Dispersal/diversification west to east
INFERRED SEQUENCE OF SPECIATION AND DISPERSAL
EVENTS IN HAWAIIAN VIOLA
EVOLUTION OF THE HAWAIIAN VIOLAS
 Evolutionary relationships of
Hawaiian violets
 Relationships among
Hawaiians, Diversification
and Inter-Island Dispersal
 Adaptive Radiation
 Biogeographic Source and
Mechanism
CANONICAL VARIATES ANALYSIS OF HAWAIIAN VIOLA
TAXA USING LEAF CHARACTERS
PRINCIPAL COMPONENTS ANALYSIS OF LEAF
CHARACTERS SHOWING HABITAT ASSOCIATIONS
PHYLOGENETIC TREE
HABITATS AND GROWTH
FORMS OF HAWAIIAN
VIOLAS
•Growth form not
linked to evolutionary
relationship
•Rather, growth form
commonly linked to
habitat
PHYLOGENETIC TREE
SHOWING LEAF TRAITS
OF HAWAIIAN VIOLAS
•Leaf morphology
not linked to
evolutionary
relationship
•Like growth form, it
is linked to habitat
•Leaf anatomy
similar (not shown)
EVOLUTION OF THE HAWAIIAN VIOLAS
 Evolutionary relationships of
Hawaiian violets
 Relationships among
Hawaiians, Diversification
and Inter-Island Dispersal
 Adaptive Radiation
 Biogeographic Source and
Mechanism
SOURCE AREAS FOR WINTERING HAWAIIAN BIRDS
SUMMARY
Hawaiian
“naturalgroup),
group”,

Hawaiian Viola is
is monophyletic
monophyletic (a
(“natural”
recently derived
Biogeographic

Biogeographic origin is Arctic/Boreal
Woody

Woody growth and inflorescences are convergent
traits evolved under tropical oceanic conditions
Initial
<3.23 million

Initial colonization on Kaui ca.
million years
years ago
ago
Dispersal
eastward,
conforming
to “chain rule”

Dispersal pattern
conforms
to “progression
rule”
SUMMARY
Diversification proceeded along an environmental
gradient, from wet to dry (forest/cliff) and mesic
habitats
Growth habit and leaf morphology (and anatomy)
tied closely to habitat, presumably due to strong
environmental selection; led to distinctive
“ecomorphic syndromes” in each
habitatadaptive radiation!
FUTURE RESEARCH
Population genetic studies using highly variable
molecular markers
Ecological characterization of microhabitats and
habitat types
Investigation of potential hybridization in three
taxon pairs
Studies on taxonomic variation in V. maviensis, V.
kauaensis and V. chamissoniana-tracheliifolia
ANSWERS TO QUESTIONS ABOUT HAWAIIAN VIOLAS
What does DNA data reveal about
the origin and relationships of the
Hawaiian violets that morphology
cannot?
Latin American violet groups are
not the nearest relatives; the
Hawaiians are most closely
related to an Arctic tundra bog
violet, Viola langsdorffii.
ANSWERS TO QUESTIONS ABOUT HAWAIIAN VIOLAS
Does the evolutionary pattern of
the Hawaiian violets conform to
the “progression rule”?
Yes, all the most primitive violet
groups grow on the oldest island,
Kauai (or can be interpreted to
arise there first).
Dispersal/diversification
proceeded to younger islands
further east.
ANSWERS TO QUESTIONS ABOUT HAWAIIAN VIOLAS
What typical features of “adaptive
radiation” are demonstrated by
Hawaiian violets?
•Morphology not reflective of
evolutionary relationships—
convergence in same habitats
•Growth form & leaf morphology
linked to environment (“adaptive”)
•Woody island species from an
herbaceous ancestor
ANSWERS TO QUESTIONS ABOUT HAWAIIAN VIOLAS
How did the ancestral seed get
from the Arctic to Kauai?
Probably by birds, either in mud on
their feet or in their digestive tract.
REFERENCES
 Ballard, H. E., Jr., K. J. Sytsma, and R. R. Kowal. 1999. Shrinking the
violets: Phylogenetic relationships of infrageneric groups in Viola
(Violaceae) based on Internal Transcribed Spacer DNA Sequences.
Systematic Botany 23:439-458.
 Ballard, H. E., Jr. and K. J. Sytsma. 2000. Evolution and biogeography of
the woody Hawaiian violets (Viola, Violaceae): Arctic origins,
herbaceous ancestry and bird dispersal. Evolution 54:1521-1532.
 Carlquist, S. 1992. Hawaii: A natural history. Lawai, Kauai: Pacific
Tropical Botanical Garden.
 Givnish, T. J. 1998. Adaptive plant evolution on islands: Classical
patterns, molecular data, new insights.
 Skottsberg, C. 1940. Observations on Hawaiian violets. Gothenburg.
Botaniska Tradgard. Medelanden 13:451-528.