World Congress of Malacology Antwerp ... - Unitas Malacologica

snails interact they may, co-operatively, stop moving; a crevice occupation rule, where if a snail
encounters a crevice it may stop moving inside the crevice; and a conspecific mucus trail following
rule. Each behavioural rule relied only on chance encounters.
The simulation accurately predicted patterns found in nature. In both simulation and reality, ‘super
trails’ formed, where mucus trails of several individuals converged as snails moved downshore.
Consequently, encounters between individuals increased, and large aggregations formed where trails
intersected with each other and with crevices.
On removal of the aggregation rule, dense aggregations of snails persisted in positions where ‘super
trails’ intersected with crevices. Aggregation, then, arises as a by-product, or emergent property, of
two individually advantageous behaviours: crevice occupation, which reduces thermal stress; and
trail following which reduces the cost of locomotion. The individual level benefit of aggregation can
then be selected for, stabilizing this emergent behaviour, and allowing aggregation to occur outside
crevices. Emergent properties of individually advantageous traits, therefore, provide an initial
mechanism to drive the evolution of co-operative behaviours.
What’s happening with (species names in) the PhyloCode?
Dayrat, Benoît
School of Natural Sciences, University of California, PO box 2039, Merced, CA 95344, USA,
Email: bdayrat@ucmerced.edu
On May 21 st , 2007, the Committee for Phylogenetic Nomenclature, which consists of 12 elected
members from the International Society for Phylogenetic Nomenclature, adopted an article providing
rules for naming species in the context of phylogenetic nomenclature. This vote, which took place
after more than ten years of debates on how to deal with species names in phylogenetic
nomenclature, constitutes a major step in the development of the PhyloCode. The new article on
species names shall be added to the version of the PhyloCode posted on the web some time this
summer. I will present the main components of this article. I will use some practical examples,
including from my monographic revision of discodoridid sea slugs, to illustrate it and discuss some of
its potential advantages.
Punctuated equilibrium alive? How living Azorian Drouetia Gude, 1911 (Gastropoda:
Pulmonata: Zonitidae) can tell a fossil story
Martins, António M. de Frias
CIBIO - Pólo Açores, Departamento de Biologia, Universidade dos Açores, 9501-801 Ponta Delgada,
São Miguel, Açores, Portugal,
Email: frias@notes.uac.pt
The theory of punctuated equilibria, arrived at and demonstrated through careful interpretation of rich
fossil data, sustains that evolution proceeds by bursts: short periods of diversification are followed by
long periods of stasis. Whereas the two time frames (rapid diversification and long stasis) can be
perceived directly from observation of the fossil record, the theory assumes various tenets observable
only in living systems: a) the biological species concept (interbreeding and reproductive isolation), b)
that reproductive isolation is generally linked to morphological change, and c) the existence of
allopatric (peripatric) speciation. Confirmation for the aforementioned assumptions can only come
from extant taxa and from them the fine resolution of short time change can be detected as well.
To see it in living taxa, one should flatten the time axis and spread it two-dimensionally. That is:
select a perfectly contained clade whose members can be assigned to discrete time frames. The model
predicts that the members of the clade living in older areas will exhibit less intraspecific diversity and
be genetically less related interspecifically (stasis), whereas those living in younger areas will be
intraspecifically more diverse although genetically closer interspecifically (diversification).
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