Download Case studies in biogeography

Case studies in Paleobiology
Vidal, G., & M. Moczydlowska-Vidal. 1997. Biodiversity, speciation and extinction trends of
Proterozoic and Cambrian phytoplankton. Paleobiology 23: 230-246.
Time: Meso – Neo Proterozoic
Location: NA
Organisms: Acritarchs (Phytoplankton)
These single celled phytoplankton left a good fossil record from the Middle Proterozoic into the
Paleozoic when few other fossils are available.
They show marked changes in diversity and abundance. Some of these changes can be correlated
with paleoclimatic and tectonic events.
Clapham, M. E. G. N. Narbonne & J. G. Gehling. 2003. Paleoecology of the oldest known
animal communities: Ediacaran assemblages at Mistaken Point, Newfoundland. Paleobiology 29:
527-544
Time~ 565 Ma
Location: Newfoundland
Organisms: Ediacaran soft bottom organisms
The extremely well preserved and varied Mistaken Point assemblages allowed Clapham
et al. to test several ecological theories about this fauna. They concluded that in the absence of
predation and any evidence of competition the different assemblages exposed on different
surfaces represent snapshots of various seres in a successional series. Faunal elements in early
stages are small and prostrate. Middle successional stages show the highest diversity. Climax
stages are dominated by large plumose upright forms. Perhaps stabilization of the silty sediments
by microbial mats allowed the development of these more structures communities.
Zhang, P., H. Zhou, Y-Q Chen, Y-F. Liu & L-H, Qu 2005. Mitogenomic perspectives on the
origin and phylogeny of living Amphibians. Systemic Biology 54 391-400
Time: mid-late Paleozoic and Mesozoic
Location: NA
Organisms: Lissamphibians (living amphibian groups)
Extant amphibians belong to three distinct groups: anurans (frogs), Caudata
(Salamanders) and Gymnophiona (caecilians). While frogs and salamanders are commonly
placed as sister groups some molecular evidence dos not fit this phylogeny.
Zhang et al. use mitochondrial sequences to investigate the phylogeny and molecular clocks to
try to date the divergence of the three living groups from possible ancestor groups which may
have included Lepospondyli, Lysorophia Temnospondyli and Dissorophoidea. They conclude
that the Lissamphibia are monophyletic, the Gymnophiona are sister to the two other groups and
that the living amphibians may be sister to the Temnospondyli. They suggest that modern
anurans may have originated in Africa-India, Salamanders in North China. From there they
spread to North America where they exhibit highest diversity. Caecilians are predominantly
Gondwanan and may have had a South America-African origin.
Van de Schootbruigge, B., T. R. Bailey, Y. Rosenthal, M. E. Katz, J. D. Wright, K. G. Miller, S.
Feist-Burkhardt and P. G. Falkowsky 2005. Early Jurassic climate change and the radiation of
organic-walled phytoplankton in the Tethys Ocean. Paleobiology 31:73-97.
Time: Lower Jurassic Sinemurian/Pliensbachian/Toarcian
Location: North West Tethys
Organisms: Phytoplankton cyst-forming dinoflagellates
A combination of oceanic connections, flooding and recession of shallow seas on continents and
inferred currents may have brought paleo-Pacific taxa into the NW Tethys replacing the ‘green’
Prasinophyte phytoplankton with ‘red’ taxa. Later, stagnation may have reduced dinoflagellate
abundance and allowed Prasinophytes. Later a boreal Sea intrusion may again have facilitated
dinoflagellate diversification which ended with the Toracian Oceanic Anoxic Event
Field, T. S., N. C. Arens, J. A. Doyle, T. E. Dawson & M. J. Donoghue 2004. Dark and
Disturbed a new image of early angiosperm ecology
Time: Early Cretaceous (or before?)
Location NA
Organisms Early Angiosperms
To Charles Darwin the suddenness of the angiosperm appearance and their rapid rise to
dominance in the fossil record was both a “perplexing phenomenon” to “those who believe in
extremely gradual evolution” and an “abominable mystery”
(http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=34068)
Recent work has suggested Amborella
(http://www.ucalgary.ca/~laidlaw/amborella/amborella_web.html) may be sister to the remaining
angiosperms. Field et al. report on morphological and photobiological studies and suggest that
the root angiosperm may have inhabited dark humid habitats they suffered frequent disturbance.
Wet understory habitats may have been uncommon in the early Mesozoic so that root
angiosperms were very uncommon and/or patchy. With more mesic conditions in the Cretaceous,
these plants may have been able to spread and diversify.
Smith, S. A. P. R. Stephens & J. J, Weins. 2005. Replicate patterns of species richness, historical
biogeography and phylogeny in Holarctic tree frogs. Evolution. 59: 2433-2450
Location: Holarctic
Time: Eocene – Miocene
Organisms: Hylid frogs (tree frogs)
Smith et al. investigate phylogenies and diversity patterns of clades of Holarctic tree frogs. They
test the hypothesis that within-group diversity increases toward lower latitudes. While tree frogs
have their global diversity maximum in the tropics (mainly due to the very high diversity in the
Neotropics) four temperate clades all show mid-latitude diversity maxima. The authors suggest
that these temperate lineages may be ecologically restricted to temperate conditions. This would
restrict them from dispersing to low latitudes and so may keep them separate from tropical
Hylids. On the other hand there is good phylogenetic evidence that they do disperse easily within
temperate latitudes.