SEMINÁRIO/
LECTURE - 30 de ABRIL, 2013; às 11 h
Under
MESTRADO em ECOLOGIA/ CBMA organization
PAVLÍCEK
Tomá¨
Institute
of Evolution, University of Haifa, Haifa,
Israel
e-mail: contact@tomas-pavlicek-biology.net
Why
are difficulties so numerous in earthworm taxonomy and in the
reconstruction of their phylogeny?
Earthworms
are regarded as a very important group of soil organisms affecting
the biotic and abiotic properties of the soil. In many terrestrial
ecosystems, they constitute the majority of the soil faunal biomass.
They play a significant role in producing soil structure and
increasing the ion base-exchange capacity and ion availability.
Despite
of their importance, the earthworm taxonomy and phylogeny is in a
chaotic state. The period following the publication of the tenth
volume of "Das
Tierreich"
(Michaelsen, 1900) deemed as "Triumph of as earthworm taxonomy"
(Stephenson, 1930), has been currently replaced by a period of "unequal chaos in earthworm taxonomy" (Briones, Morán, & Posada, 2009). The blind application of the
taxonomic and phylogenetic methods developed for Deuterostomia and/or
Ecdysozoa without considering the evolutionary peculiarities of
earthworms, and possibly of all Lophotrochozoa, leads, among others,
to the observed low statistical support splits, especially in the
basal parts of the constructed bifurcating-like phylogenetic trees
(Brigandt, 2001; James et al., 2010; Jamieson, 1988; Pop, Csuzdi,
Cech, Wink, & Pop, 2007; Pop, Wink, & Pop, 2003).
The
failure
of the traditional phylogenetic approaches that are using
averaging of taxonomic characters and/or the classical
bifurcating-like phylogenetic tree like analyses, is, in our opinion,
due to the hybrid origin of earthworm species (Pavlícek, Hadid, &
Csuzdi, 2012), and possibly of other annelids. Also, the use of mtDNA
for phylogenetic analyses (and for barcoding) in earthworms is
problematic. It seems that the existing barrier protects nuclear
genes or at least part of the nuclear genes, but not the mtDNA genes,
from the effect of gene flow during hybridization events. The
documented rare cases of biclitellate homeosis producing "nsters"(Gates,
1956) indicate the potentially disastrous effects (Pavlí?ek
et al., 2012) of inter-lineage hybridizations.
At
the end of 19th century, two conflicting theories of evolution had
been proposed: the first based on the concept of continuous variation
and the second on the concept of discontinuous (saltational)
variation. W. Bateson concluded that continuous and discontinuous
variation are distinct essentially ... that they are manifestation of
different process".
Scientists like De Vries, R. Goldschmidt, N. Eldredge and S. J. Gould
would agree with the content of this quote, but it would be
dismissed, together with all the concept of the saltational
evolution, by the majority of influential evolutionary biologists
such as E. Mayr, and T. Dobzhansky. The discontinuous
variability in body size in a population of earthworms is a sign of
saltational evolution resulting from the autohomoploid hybridization
process in earthworms. The autohomoploid hybridization and other
processes, some of them unique for annelida or clitellata, during
embryogenesis and cytogenesis have a determining role on speciation,
population differentiation, and probably account for the discordance
between nuclear and mtDNA evolution. The proposed model of evolution
can also explain, among others, the problems experienced during
phylogeny reconstruction by means of bifurcating phylogenetic trees,
and failures to delineate some species by means of morphological or
genetic (molecular) distances.
Dr. PAVLÍCEK
Tomá¨
Senior
researcher at the Institute of Evolution, University of Haifa, Israel
Fields
of specialization: Evolutionary
genetics, population genetics, ecology, zoogeography, entomology,
earthworm biology.
Convenor
of the 3th,
4th,
5th
and 6th , International Oligochaete Taxonomy Meetings (Cyprus,
Turkey, Switzerland, Portugal)
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