World Congress of Malacology Antwerp ... - Unitas Malacologica

Hidden genetic diversity in cephalopods: cryptic speciation or deep mitochondrial coalescent
events?
Anderson, Frank E.
Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901 USA,
Email: feander@siu.edu
Some cephalopod species show evidence of substantial genetic variation and are probably species
complexes, while others appear to be panmictic over large geographic areas. Recent investigations of
Alloteuthis (Loliginidae) have revealed unexpected patterns of genetic variation. Alloteuthis
comprises three nominal species of small squid (A. media, A. subulata and A. africana) found in the
eastern Atlantic and Mediterranean. Two mitochondrial loci (COI and 16S) were sequenced from
multiple individuals from each species, collected from several localities by a network of
collaborators. Two of the nominal species (A. media and A. subulata) have substantially overlapping
geographic ranges and cannot be separated based on mitochondrial data, suggesting that these two
“species” are actually one (referable to A. media), with weak genetic differentiation between Atlantic
and Mediterranean populations. The mitochondrial data also revealed three specimens from Italian
waters that could represent a cryptic Alloteuthis species. All putative Alloteuthis species (including
the alleged cryptic species) pass two common “DNA taxonomy” tests for species diagnosis using
COI data: reciprocal monophyly and the “10X rule”.
However, the aberrant Italian specimens could simply represent an unusually deep mitochondrial
coalescent event within a single species, rather than reproductive isolation among species. To
distinguish between these possibilities, a nuclear locus (rhodopsin) was sampled. The Alloteuthis
rhodopsin phylogeny was broadly congruent with (but not identical to) the mitochondrial phylogeny,
suggesting that the cryptic species is a distinct evolutionary entity. Gene tree parsimony analysis and
results from coalescent simulations were consistent with the hypothesis that the aberrant specimens
represent a cryptic species. This study highlights the importance of 1) sampling multiple individuals,
locations and loci for species-level molecular phylogenetic studies, and 2) accounting for the
stochastic nature of the coalescent process when assessing incongruence among gene trees for closely
related taxa.
Sexual selection and its consequences in the Opisthobranchia
Anthes, Nils
Animal Evolutionary Ecology, Zoological Institute, Eberhard Karls-Universität Tübingen, Auf der
Morgenstelle 28, 72076 Tübingen, Germany,
Email: nils.anthes@uni-tuebingen.de
Charles Darwin validly argued that, in hermaphrodites such as opisthobranchs, sexual selection could
not affect traits such as external colouration. Today, however, we are aware that sexual selection
often operates much more subtly and targets a multitude of traits associated with the male or female
reproductive function of a hermaphrodite. Recent empirical studies provide intriguing insights into
the levels at which sexual selection may act in various opisthobranch groups. These include, for
example, male and female genital morphology, the behaviour associated with mating, the mode of
insemination, male and female mate choice, or the trade-offs between male and female resource
investments. Here I examine current evidence for the effects of sexual selection on the evolution of
opisthobranch characters and identify fields of research that require increased attention in the years to
come. Some specific aspects of opisthobranch reproduction, such as the often independently
performed male and female function, render this group particularly suitable to study some general
predictions of sexual selection theory.
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