World Congress of Malacology Antwerp ... - Unitas Malacologica

A DNA-based phylogeny resolves divergent and convergent evolution of limpets (Lottiidae)
Eernisse, Douglas J. 1 ; Hewson, William E. 2 ; Kelly, Ryan P. 3
1. Department of Biological Science, California State University, Fullerton, CA 92834 USA,
Email: deernisse@fullerton.edu
2. Department of Biological Science, California State University, Fullerton, CA 92834 USA,
Email: william@uts-hawaii.com
3. Columbia University and American Museum of Natural History, New York, NY USA,
Email: rpk@stanford.edu
A preliminary phylogenetic analysis of the limpet genus Lottia (Patellogastropoda: Lottiidae), based
on over 400 new and 50 existing partial mitochondrial 16S rDNA sequences, has revealed striking
convergence and divergence in shell shape and feeding ecology. Altogether, 30 western North
American species of Lottia and related genera have been newly sequenced, most represented by
multiple populations and multiple specimens per population. All 30 were resolved as reciprocally
monophyletic. Deeper branching patterns within Lottia are less well resolved by 16S alone, with only
some species groups supported, but resolution is still sufficient to infer interesting patterns of limpet
ecology and morphology. Among the new or previously reported (e.g., D. R. Lindberg, B. Simison,
E. Begovic) patterns that this analysis corroborates are: 1) dramatic shifts in feeding ecology: limpets
living on surf grasses (“Lottia” paleacea) or eel grasses (“L.” depicta) are in a clade apart from
Lottia, and this clade also includes a coralline alga specialist, “L.” rosacea; 2) striking parallelisms:
“L.” rosacea is phylogenetically distant from another morphologically similar coralline alga
specialist, Lottia triangularis; another example is a new species that is highly convergent to the L.
“ochracea” rock ecomorph; 3) profound ecomorphological variation: Lottia “ochracea” is merely a
rock ecomorph of a species, L. instabilis, known for its habit of living on kelp stipes; 4) cryptic
species: three other new species are likely allopatric species pairs of L. digitalis, L. pelta, or L.
strigatella, respectively, and each pair of species has a similar broad range of ecophenotypic
variation; 5) new phylogenetic resolution: as rooted with outgroups, Acmaea mitra, A. funiculata, and
Lepeta caeca, the most basal Lottiidae lineage is the type species of Tectura, T. virginea, whereas a
common northern Atlantic species usually referred to this genus, “Tectura” testudinalis, is
phylogenetically remote – it is instead clearly nested within Lottia.
Chitons as potential models for investigating recent and parallel evolution of eyes
Eernisse, Douglas J.
Department of Biological Science, California State University, Fullerton, CA 92834 USA,
Email: deernisse@fullerton.edu
Chitons lack a brain or even a head but have hundreds of sensory organs called esthetes (or aesthetes)
in the upper layer of their shell plates, and these can be traced to Paleozoic chitons over 400 million
years old. The nervous innervation of esthetes is complex and can be visualized with epoxy casts as
compared across chitons in a recent collaborative study. Esthetes often have a photosensory role and
1920s naturalists demonstrated that a chiton would immediately stop crawling and clamp tightly
when a shadow was cast from over 10m away. Two phylogenetically distant lineages of chitons
(Chitonidae: Acanthopleurinae and the distantly related genus Schizochtion) have evolved even more
elaborate ocelli, organized in radiating rows on their shell plates. A preliminary molecular analysis
has confirmed that ocelli must have evolved in parallel. Ocelli are qualitatively different from a
simple esthete, being much larger with a well-developed lens, cornea, etc. There are a few
ultrastructural and electrophysiological studies and some behavioral experiments have been done to
cover up the ocelli to observe how behavior changes, but ocelli are still woefully under-studied. For
example, the lineage with the largest ocelli in chitons (Schizochiton) was last studied in the 1890s.
The lack of ancient fossils of Acanthopleurinae or Schizochiton and their derived taxonomic position
implies that chiton ocelli only recently evolved. In contrast, the primary model systems for examining
eye anatomy and evolution (e.g., mammals, flies, cephalopods) already had ancestors with eyes 500+
55