CONTENT - International Society of Zoological Sciences

S6 ICZ2008 - Abstracts
Evolution of main groups of Bryozoa during Phanerozoic :
present data
Françoise P. Bigey
9 rue de Douai F -75009 Paris France
Among lophophorates, bryozoans appear as peculiar organisms
especially on account of significant extent in present marine
environments and in many past marine environments as well. It
concerns stenolaemates and gymnolaemates. Fossil
phylactolaemates, fresh water colonies without mineralised skeleton,
are revealed by statoblasts only, in some cases on account of
difficult preservation. Unlike brachiopods, the other main lineage of
lophophorates, the oldest bryozoans were described from ordovician
strata.
If main prevailing paleozoic orders (cystoporates, trepostomates and
fenestrates) are extinct, they were replaced by other ones as
cheilostomes, since Upper Jurassic and, predominating now.
Mention must be done of ctenostomates, free of calcareous skeleton,
but recognised by immuration process since Ordovician.
Cyclostomates, widely developed in Jurassic and Cretaceous, are
known from Ordovician too.
Bryozoan evolution is characterised by links with main biological
crisis, particularly the permo-triassic one, quite drastic for these
organisms, even though few of them survived in Lower Triassic.
Recovery in marine environment occurred only during Jurassic. From
Middle Cretaceous cyclostomates/cheilostomates ratio in
assemblages begins to reverse for the benefit of last ones. This ratio
did not widely evolved since Eocene.
Bryozoan systematics as a whole (fossil and recent forms) is
established from skeletal characters. Phylogenenetic relations of
cyclostomates, for instance is based on wall types. Cladistic analysis
is used to propose models at different levels of organisation. For
recent bryozoans data from DNA are promising.
Why are there more genera of Mutillidae (Hymenoptera) with
wingless males in Southern Africa than elsewhere?
Denis J. Brothers
School of Biological and Conservation Sciences, University of
KwaZulu-Natal (Pietermaritzburg), Private Bag X01, Scottsville, 3209
South Africa
The velvet ants of the family Mutillidae (Hymenoptera: Vespoidea)
are larval parasitoids of the enclosed immatures of other insects,
specially other aculeate Hymenoptera (bees and wasps). Mutillid
females are all completely apterous, with the mesosomal (thoracic)
sutures entirely fused (or almost so) so that the mesosoma is a
simple box-like structure. Males are generally fully winged, with the
mesosoma essentially unmodified, and with almost all sutures
articulating. This dimorphism has been related to biology: wings
would be an encumbrance and susceptible to damage for females
searching underground or in burrows for hosts, and good motility
(flight) would be required for the discovery of mates by males,
avoidance of inbreeding and possibly dispersal. Associated with the
dimorphism in wing development is differentiation in other features
(such as colour pattern), so that the two sexes of a single species
can generally not be associated on the basis of morphology.
Nevertheless, there are several species (and genera) in which males
show wing reduction to varying degrees, with loss of flight ability,
from brachypterous with the mesosoma scarcely modified through
several intermediate steps to completely apterous and with the
mesosomal sutures entirely fused as in the female. Apterous males
generally look very similar to their females.
This poster provides an illustrated survey of the range of wing
reduction in male Mutillidae, its distribution across higher taxa,
genera and geographically, and attempts to draw some conclusions
and identify explanatory patterns.
S7- Paleontology and Evolution
- 26 -
Palaeontology: a load of old stones?
Simon Conway Morris
Downing Street, CB2 3EQ, Cambridge, England
Some years ago the distinguished evolutionary biologist John
Maynard Smith welcomed palaeontology back to the High Table; a
very English type of invitation with the implication that one would be
subject to a series of terrifying conversations whilst drinking
inordinate quantities of wine. In fact the last few years may have
been quite benign for palaeontology, with wide-spread interest
amongst evolutionary biologists, as well as being marked by a
steady stream of hi! gh profile papers in Nature and Science (and, of
course, elsewhere). But as we all know to rest on one's laurels can,
sooner or later, lead to a strong and distressing smell of
decomposition. As ever we need to look to the future. In this
presentation I will outline a few areas where we should be able to
contribute to the wider conversations in evolution and the earth
sciences. How well do we know life in very deep time, especially in
the nether regions of the Precambrian? Are we any closer to
explaining the Cambrian explosion? Is the influence of mass
extinctions over-rated? Can we identify directionality and increasing
complexity, even progress, from the fossil record? Does anybody still
seriously subscribe to the metaphor of Stephen Jay Gould that were
we to re-run the tape of life we would end up with a completely
different biosphere? So too may we finally declare punctuated
equilibrium dead and buried? What real links exist between the
fashionable areas of evo-devo and the transformations we see in the
fossil record? Where are the real puzzles in terms of identifying
transitional groups and why apparently are they so difficult to
decipher? Do we radically under-estimate the importance of nonuniformitarian
worlds: What is ecology really like in deep time? Will
we be in any position to advance our understanding of the evolution
of behaviour, as! well as sensory systems, communication and
brains, even the emergence of consciousness? And to finish on an
absurd note: What future for astrobiology?
The Lilliput Effect in Cretaceous-Tertiary (K-T) Planktonic
Foraminifera
Norman MacLeod
Palaeontology Department, The Natural History Museum, Cromwell
Road, London, UK, SW7 5BD
The stratigraphic record of K-T planktonic foraminifera represents an
outstanding target for probing the dynamics of the Lilliput Effect.
Preliminary analysis indicates this event began prior to the
emplacement of bolide impact debris. Event initiation is marked by a
rapid decrease in test size among K-T survivor taxa and defined by
the maintenance of these small-size populations, along with the
appearance of small, fully Danian species, for the first 40,000–
200,000 years of the Danian. The atypically small size of the latter is
a direct result of speciation from the former. Correction for
phylogenetic covariation reveals the presence of a strong
phylogenetic signal in generic size data. In particular, it appears the
extinction of larger-sized Cretaceous species had little effect on the
evolutionary size dynamics of the Lilliput faunas. Finally, morphotype
analysis shows that the K-T Lilliput interval represents a transition
between faunas exhibiting a diversity of trochospiral and flaring tests
to those composed almost exclusively of rounded trochospiral forms.
This, in turn leads to a subdivision of the K-T planktonic foraminiferal
Lilliput event into a two-stage structure: Stage 1 (Zone P0)
representing a small-sized, flared test-dominated fauna and Stage 2
(Zone P1a) representing a slightly larger sized rounded trochospiredominated
fauna. The entire event exhibits a duration of c. 300,000 -
500,000 years. Application of this data analysis strategy to the
succeeding Cenozoic interval illustrates the important role phylogeny
should play in understanding the evolutionary history of organismal
size.