more questions: what are the closest relatives of the trentepohliales? is the order trentepohliales...
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More questions:
•What are the closest relatives of the Trentepohliales?
•Is the order Trentepohliales a monophyletic group?
•What evolutionary processes have occurred within the Trentepohliales?
• Two lineages in Viridiplantae
•Trentepohlialean taxa are unequivocally within the chlorophycean lineage
• The order Trentepohliales is included within the ulvophycean taxa
• The order Trentepohliales is a monophyletic group
• Phragmoplast?
Relationships within the Ulvophyceae• The marine orders are the most closely related to the Trentepohliales
In all phylogenetic analyses the Trentepohliales emerged as a sister group to the clade containing the Siphonocladales/Cladophorales complex and Dasycladales, both containing representatives mainly from the marine environment!
Relationships within the Trentepohliaceae
•What about the relationships inside of the family?
•Are the genera monophyletic?
•Is the species Cephaleuros virescens, with a world-wide distribution, a monophyletic taxon?
•What is the validity of several morphological characters used for separation at species and genus level?
Four main lineages in 18S rDNA:
Cephaleuros clade
Printzina lagenifera clade
Trentepohlia aurea clade (the generitype)
Trentepohlia iolithus clade
Molecular data challenge traditional classification schemes
Relationships within the Trentepohliaceae
On the basis of our results, Cephaleuros forms a well-defined monophyletic group, representing a more advanced clade
Conversely, Trentepohlia is non monophyletic and the other genera included in the analyses do not represent separate lineages, suggesting the possibility that a major rearrangement at the genus level may be necessary in the future
Relationships among Trentepohlialean genera
Printzina was proposed as a new genus for nine species previously belonging to Trentepohlia
The shape of the sporangia, the arrangement of the sporangiate-laterals, the extensive development of the prostrate parts of the thallus and the occurrence in shaded habitats were considered the key characters separating Printzina from Trentepohlia
The only feature that separates conclusively the two genera is the shape of the sporangia
•globular to reniform in Printzina
•ovoid in Trentepohlia)
The position of Phycopeltis is surprising
Importance of the position of the ostiole in the zoosporangium as key character
T. umbrina (as P. umbrina) with an ostiole opposite to the end of attachment too
T. abietina from Hawaii shows the ostiole clearly opposite to the end of attachment
Our results provide therefore some evidence that the position of the ostiole may be a good phylogenetic marker
•Cephaleuros virescens Kunze, the generitype of Cephaleuros, is generally considered to have a worldwide distribution in tropical and subtropical regions
•Strains of C. virescens do not form a monophyletic group; South Africa and Taiwan are more closely related to C. parasiticus than to other C. virescens
Relationships within a species: Cephaleuros virescens
•These data suggest that the circumscription of C. virescens should be reconsidered
•Morphological characters used to separate this species form similar taxa should be reassessed
•As currently circumscribed, C. virescens represents a complex of morphologically similar entities
•Suriname is the type locality of C. virescens, the actual distribution of this species might be restricted to tropical South and Central America
Current analyses using the chloroplast-encoded rbcL marker confirm 18SSU results
*
Lessons learned
A subaerial habit has developed within the class Ulvophyceae
Morphological criteria traditionally used for the circumscription of genera and species of Trentepohliales are not correlated with evolutionary patterns
Common and world-wide distributed species may represent a species complex of morphologically similar entities (cryptic species)
Many morphological characters used in taxonomy are not phylogenetically relevant
Another subaerial lineage has been found from a group containing representatives mainly from the marine environment
Evolution of the subaerial flora
From textbooks to popular articles there is an appreciation that terrestrial life emerged from the seas. And there is generally no explanation that by “seas” is meant from oceans and lakes – that is, from both marine and freshwater sources
Several representatives of the marine green algal class Ulvophyceae have been found to be members of the terrestrial algal flora
The order Trentepohliales and our newly described taxa are examples of a direct marine invasion of terrestrial environments!
This is in contrast with the general idea that terrestrial floras are descendents of freshwater ancestors and not directly from marine ancestors
A direct marine invasion?
One intriguing, even puzzling, question is:
How marine algae, from ulvophycean ancestors, “jump” into terrestrial habitats and became permanent representatives of the land flora?
A probable answer may came from independent bits of information:
• Fossils
• Ancient changes of sea level
• Pre-adaptive phenotypic plasticity
Records of fossils belonging to terrestrial microchlorophytes have been found as early as the late Eocene (ca. 50 mya)
Dilcher 1965
As Pelicothallus villosus
Described as a fungus
Dilcher 1965
As Pelicothallus villosus
Described as a fungus
Reynolds and Dilcher 1984
As Cephaleuros parasiticus
Re-described as an alga
Later transfer to C. villosus
By Thompson & Wujek 1997
Reynolds and Dilcher 1984
As Cephaleuros parasiticus
Re-described as an alga
Later transfer to C. villosus
By Thompson & Wujek 1997
Fossil subaerial microchlorophytes
Koeck 1939: Fossilie Kryptogamen aus der eocanean Barunkohle des Geiseltales. Nova Acta Leopoldina 6:333-351
Trentepohlia diffusaTrentepohlia diffusa
Trentepohlia aureaTrentepohlia aurea
Fossil trentepohlialean taxa have been reported from the German Eocene
Printz 1939: Vorarbeiten zu einer Monographie der Trentepohliaceen.S. Nytt Mag. Aturvidenskapene B. 80:137-210, Taf.I-XXXII
Koeck 1939: Fossilie Kryptogamen aus der eocanean Barunkohle des Geiseltales. Nova Acta Leopoldina 6:333-351
Trentepohlia rigidulaTrentepohlia rigidula
Trentepohlia aurea var. acutataTrentepohlia aurea var. acutata
Printz 1939: Vorarbeiten zu einer Monographie der Trentepohliaceen.S. Nytt Mag. Aturvidenskapene B. 80:137-210, Taf.I-XXXII
Reliable fossil records established trentepohlialean floras as far as the Eocene 50 mya
By the end of this epoch:
Continents moved closer to their present position
Tropical areas shrinking
A drying period commences
In subtropical latitudes, open woodlands with ferns and shrubby plants replaced forests
Whale ancestors left the land
Trentepohlialean taxa appeared on land over 400 my after the initial colonization of land plants in the Paleozoic (480 mya)
http://3dparks.wr.usgs.gov/
Falkowsky et al. 2004; sea level change
Ancient sea level changes
•Just before Eocene (50 mya) the sea level was at the highest and since then it has been receding
•Much of continental North America, Africa and Australia were exposed
Falkowsky et al. 2004; sea level change
Evolution of floras such as
• Diatoms• Grasses
• Intertidal marine algae live in a variable environment under great physical stress
• This may lead to a selection for a “plastic morphology” were the same genotype is expressing several morphologies under different ecological conditions
• Extant ulvophyceans are examples of this adaptive phenotypic plasticity:
Pre-adaptive phenotypic plasticity
Terrestrial ulvophytes express this adaptive phenotypic plasticity by their ecological ubiquity, ability to grow in several media, and their astonishing capacity to undergo morphological modifications:
Printzina
Trentepohlia
Phycopeltis
Cephaleuros
Information from fossils, ancient sea level changes, phenotypic plasticity and molecular data seem to indicate that:
• Terrestrial ulvophytes did not “jump” from marine to terrestrial habitats: they were “left behind” after sea levels receded during the Eocene
• Ancestors of terrestrial ulvophytes may had the pre-adaptive capabilities to exploit and diversify in the new habitat and become permanent members of the subaerial flora
Many questions still remain to be answered, for example: •Exclusively subaerial algae have a long evolutionary history compared to other green algal orders; however, their fossil evidence is relatively more recent; what is the evolutionary history of this lineage between their ancestral marine origin and their transition to land?
Cladophora-likePrecambrian 700-800 mya
Yakutina and DasycladsCambrian600 mya
TrentepohlialesEocene50 mya
Many questions still remain to be answered, for example:
•Exclusively subaerial algae have a long evolutionary history compared to other green algal orders; however, their fossil evidence is relatively more recent; what is the evolutionary history of this lineage between their ancestral marine origin and their transition to land?
•Another intriguing question is about evolutionary reversals: are there any examples of algae that originated in the continental environment and made a transition back to the sea?
Trebouxiophyceae: Stichococcus marinus?Chlorophyceae: Dunaliella spp. ?Trebouxiophyceae: marine Prasiolales (Prasiola and Rosenvingiella)
Some conclusions
The terrestrial habitat has been colonized by several lineages and more than one green algal group
The Charophycean, Trebouxiophycean and Chlorophycean algae made attempts to colonize the Land via freshwater habitats
The marine Ulvophycean taxa also made this conquest (at least twice)
Subaerial ulvophytes conquered the land using a direct strategy
The history of the conquest of terrestrial habitats by algae is more complex than previously recognized
New molecular techniques (environmental cloning and phylogenomics) may unravel more unknown lineages and unexpected discoveries!
Acknowledgments
Russell L. Chapman, Scripps Institution of OceanographyMike Guiry, National University of Ireland
Paul Broady, University of Canterbury, New ZealandThomas Friedl, University of Goettingen
Fred Brooks, American Samoa Community CollegeAlison Sherwood, University of Hawai’i at Mãnoa
Joe Zuccarello, Victoria University of Wellington, NZBruno De Reviers, Paris HerbariumRicardo Tsukamoto, Sao Paulo, BZ
Jirí Neustupa, Charles University of Prague, Czech Republic
Research at the Phycolab is funded by grants from NSF Systematics-DEB, NEP, MASGC, CA&S/UA and from a RAC/UA to JLB
Fieldwork funds to French Guiana, South Africa, Gabon, Panama, Suriname, Europe, and Southern Mexico partially provided by the Graduate School and the Department of
Biological Sciences at UA
Drs. Fabio Rindi and Sarah M. Noble, graduate students Daryl W. Lam and Haj A. Allali, several undergrads
The PhycoLab in the Web
http://bama.ua.edu/~jlopez
Ongoing Research at the PhycoLab
Subaerial microchlorophytes
South Africa
Morocco
Gabon
Southeastern USA
Panama
French Guiana
Suriname
Europe
and Australia
Assembling the Tree of Life Program:
M. Sc. Ruben Cabrera Marine Archeology
Dr. Ana Maria Suarez Inst. Marine Sciences
University of La Havana
Dr. Beatriz Martinez Oceanology Institute, CITMA
Antonio Vega, Holguin
Ivan Martin, Villaclara
Sandra Siret, Matanzas
Lidice Clero, CIM
Angel Moreira, Cienfuegos
Yusimi Alfonso, Acuario Nacional
Abdiel Jover, Santiago
Juan J. Lake, Camaguey
Mayrene Guimaraes, Cayo Coco
UA – CUBA Seaweed research collaboration
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