World Congress of Malacology Antwerp ... - Unitas Malacologica

Freshwater limpets of the well distinguished family Acroloxidae (Pulmonata: Hygrophila) are
characterized by enigmatic distribution patterns. They are restricted to the Holarctic region with very
few commonly recognized species as well as a major radiation in ancient Lake Baikal and a less
species-rich assemblage of endemics in Lake Ohrid. In the Nearctic, there is only a single rare relict
species, A. coloradensis, which has been regarded as closely related to the widespread European A.
lacustris.
We studied Acroloxidae throughout their distribution range covering Europe, Far East Russia, North
America and the ancient lakes Baikal and Ohrid. Phylogenetic and biogeographic relationships and
timing of diversification events for the acroloxids were investigated based on DNA data from two
mitochondrial (COI, LSU rDNA) and one nuclear gene (SSU rDNA).
In contrast to the commonly held view, A. lacustris is not the sister species of A. coloradensis,
instead the latter is closely related to a Far East Russian species. The endemics of both ancient lakes
each form monophyletic groups. The Lake Ohrid species are related to two other European species
and the Baikal species flock is the sister group of the Far East and North American species.
Using an average COI molecular clock rate for Protostomia of 2.23�0.22% K2P distance/My, we
estimated the age of the split of the Ohrid species at 0.97 ± 0.43 My. This temporal window coincides
with Pleistocene speciation events in other macrozoobenthic groups of Lake Ohrid. In Lake Baikal,
the onset of the intralacustrine radiation started 2.55 ± 0.43 Mya. The most recent common ancestor
of the North American A. coloradensis and the Far East A likharevi diverged 2.41 ± 0.48 Mya. The
Baikal radiation probably started in the aftermath of dramatic Late Pliocene climatic changes in the
region, while the separation of Far East and North American acroloxids is most likely linked to
earlier breakups of Beringia, mainly disintegration of united Siberian-Alaskan river system.
The subfamilies Margaritinae and Calliostomatinae from South Shetlands Island to
Bellinghausen Sea: species diversity and unknown identities
Aldea, Cristian 1,3 ; Zelaya, Diego G. 2 ; Troncoso, Jesús S. 3
1. Centro de Estudios del Cuaternario de Fuego-Patagonia y Antártica (CEQUA), Punta Arenas,
Chile,
Email: cristian-aldea@uvigo.es
2. Division Zoología Invertebrados, Museo de la Plata, 1900 La Plata, Buenos Aires, Argentina,
Email: dzelaya@fcnym.unlp.edu.ar
3. Departamento de Ecología y Biología Animal, Facultad de Ciencias del Mar, Campus Lagoas
Marcosende, 36310, Universidad de Vigo, España,
Email: troncoso@uvigo.es
During the Spanish Antarctic Expeditions BENTART (2003 and 2006) numerous species from the
subtidal to deep-water mollusks were sampled. This research was focused on West Antarctica, from
South Shetlands Islands to Bellingshausen Sea. Among these samples, trochids were particularly
abundant, both in number of species and specimens. The abundance of material coming from the
BENTART expeditions represented a great opportunity to obtain new information of some of these
taxa, as well as further precisions on the distributional range of the species. Despite the great
diversification exhibit by Trochidae in the Southern Ocean, there are many species with doubtful
taxonomic status and unknown identities, mainly from Bellingshausen Sea, an area poorly sampled.
In this study we focus on the subfamilies Margaritinae and Calliostomatinae. The Margaritinae were
represented by five species: Antimargarita dulcis (Smith, 1907), A. smithiana (Hedley, 1916),
Margarella antarctica (Lamy, 1905), M. refulgens (Smith, 1907) and Tropidomarga biangulata
Powell, 1951. First records for Antimargarita dulcis, A. smithiana and Margarella refulgens are
presented. The diagnostic characters for each of these species are revised and is discussed its
affinities with others trochids species. The Calliostomatinae were represented by one, most probably
new species of Falsimargarita, from South Shetlands Islands. This species has a shell very close to
the Margaritinae Antimargarita dulcis, and the gross anatomy of this species is studied. In this sense,
the genera Falsimargarita Powell, 1951 and Antimargarita Powell, 1951, differ in their radula, but
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