World Congress of Malacology Antwerp ... - Unitas Malacologica

permission to begin a conservation assessment for North American freshwater gastropods and an
initial committee has been formed. The final evaluation will be based on our current understanding of
freshwater gastropod taxonomy. Breaking with earlier assessments, we seek to replace categorical
rankings (i.e. Endangered, Threatened, Species of Concern, etc.), with more definitive G-rankings
that are actively monitored by NatureServe, state Natural Heritage Programs and UNITAS. A draft
evaluation focusing on 655 species in all 50 states and 11 Canadian Provinces was completed in early
2004. This initial assessment determined 60 species of freshwater snails are likely extinct, at least
310 additional species rank as G1 or G2, with another 75 species listed as G3. Thus, 445 currently
valid aquatic gastropod taxa are extinct, endangered, threatened, or of special concern – the highest
level of imperilment for any group of animals in North America. The initial draft checklist will be
presented and comments from symposium participants solicited.
Molecular phylogeny as a lens for examining morphology and biogeography: Examples from
the chromodorid nudibranchs
Johnson, Rebecca Fay
Department of Invertebrate Zoology and Geology, California Academy of Sciences, 875 Howard St.,
San Francisco, CA 94103, USA,
Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz,
CA 95064, USA,
Email: rjohnson@calacademy.org
Chromodorid nudibranchs are a diverse, beautifully colored family of shell-less opisthobranchs found
worldwide, mainly in the tropics. The last comprehensive study of the entire group is 23 years old
and was based solely on morphology. Except for a few cases, many morphological characters used to
diagnose genera are continuous or can be found throughout the group. This lack of understanding of
characters has led to both the expansion of genus diagnoses and the creation of new generic names
for unusual morphology. These problems combined with the regional nature of many previous studies
have added to the difficulty of determining monophyletic groups and polarizing morphological
characters for phylogenetic analyses. Previous molecular work on chromodorids has been limited to
fewer than 10% of the more than 300 described species. Of these sequenced species the majority are
from the Atlantic and eastern and southern Australia. The Indo-Pacific tropics are home to the
greatest diversity of chromodorid nudibranchs, and yet the bulk of this fauna has never been included
in any molecular studies of the group. In this study, thanks to targeted collecting trips, dedicated
collectors and DNA extracted from museum collections, I was able to include specimens from the
Indo-Pacific, eastern Pacific and Caribbean. I sequenced fragments of the mitochondrial genes,
cytochrome oxidase I (658bp) and 16s (~330bp), for over 225 individuals, representing 120 species
and 15 of the 17 genera currently classified in the family Chromodoridiade. By including three
species of from the Actinocyclidae and other dorid nudibranchs in my data set, I was able to test the
monophyly of the chromodorids, the proposed sister group relationship of the actinocyclids to the
chromodorids as well as further investigating the relationships among chromodorids. This
phylogenetic hypothesis is a framework for further examining morphological characters, discovering
synapomorphies, delineating monophyletic groups, and exploring biogeographic questions.
106