Dr Daniel Geiger

The Haliotidae (ormers to those in the UK, abalone where I come from!) is a very widespread family of marine gastropods. In my doctoral thesis, I undertook a general revision of the family, using all available sources of evidence. My major findings are:

1. Recent Taxa

There are 56 valid species, with 10 valid subspecies, out of over 200 described species-level taxa. This species-count is 20 less than the previously accepted total of 75, given that I have also described one new species. This revision shows that a critical evaluation of the ingroup one is studying is a crucial first step in any phylogenetic analysis.

2. Fossil Taxa

Haliotids are rare in the fossil record, due to the rocky habitats usually occupied, and to the nacreous shell, which does not preserve well. The earliest records (Upper Cretaceous: Maastrichtian) are unlikely to represent the root of the lineage. The ecology of haliotids seems not to have changed over the documented time-span, and no on-shore/off-shore pattern of vertical distribution could be detected.

3. DNA Sequence Alignment

Critical evaluation of aspects of coding analysis in cladistics revealed inconsistency in the way in which DNA sequences are used. As I used a combination of various data, such an evaluation is at the heart of a cladistic analysis. A strict comparison of the treatments of morphological and sequence data, based on philosophy of science, has led me to propose a new methodology for the treatment of sequence data in phylogenetic systematics. First, DNA sequence alignment must be limited to the smallest identifiable fragment, which I call minimum fragment alignment. Second, gaps must be treated as a fifth character state, because they are postulated during the classification of observations. Third, any differential weighting scheme is without a basis, because observations are equivalent as such, and because such weighting schemes introduce an explanatory element into the observational phase. Fourth, differences in alignments are due to questionably aligned sequences, and recoding of such areas can only be accomplished by data reduction strategies such as exclusion and data contraction. Flexible coding strategies such as elision, polymorphic coding, missing data coding, presence/absence coding and case-sensitive coding all introduce internal conflicts and inconsistencies. For few, but very dissimilar taxa, I have introduced new coding strategies of block coding and stretch coding, and they have been applied in my analyses.

4.Biogeography

The distribution of all 56 species is documented, based on data from museum collections
(cf: http://www.nhm.org/~dgeiger/ABMAP ). There are no haliotid species with a global distribution. A parsimony analysis of endemicity revealed a general Indo-Pacific origin for the family. The precise origin cannot be pin-pointed with the data now available. Two other biogeographic hypotheses (Tethys origin, Pacific Rim origin) are considered less likely, but the Indo-Pacific hypothesis also has some inconsistencies, which may be due to the potentially long evolutionary history of the family, reaching back at least to the middle Mesozoic.

5. Total Evidence Cladistic Analysis

All data analyses show the following patterns: There is a north Pacific group including the Japanese as well as the west American species; there is a group of species endemic to Australia; there is a group of widespread Indo-Pacific species, but the three species found only in New Zealand are dispersed over the whole tree.

Molecular synapomorphies can be identified for some of the above groups, but morphological characters do not show clear evolutionary patterns. The combination of molecular data sets contributes to the resolution of the combined topology, despite some missing data. The addition of morphological characters, although a complete data set, allows multiple character state optimizations leading to a large polytomy among north Pacific taxa. Outgroup comparison is currently of little value; there are no molecular data available, and similarity statements for available morphological characters are questionable.

Only four of the 17 currently proposed genus-level taxa are justified. I suggest that only the genus Haliotis, s.l. should be used for all abalone/ormers. Additionally, four subgenera may be used: Haliotis, s.s., for its Indo-Pacific type species H. asinina; Nordotis, for the north Pacific species; Notohaliotis, for the species endemic to Australia; and Sanhaliotis, for some of the widespread Indo-Pacific taxa. No other genus-level taxa warrant recognition at this time.

Pdf files of my dissertation can be downloaded from: http://www.nhm.org/~dgeiger/dissertation.html

Current Activities

Over the last year, I have written the abalone monograph in the Conchological Iconography series, tied up some loose ends in abalone systematics, and started sequencing Histone 3 and cytochrome oxidase c subunit 1 from representatives of all vetigastropod families. I have been looking at the evolution of size in Vetigastropoda, and I am continuing my philosophical analysis of cladistic methodologies. I have just begun to attack a new family (Fissurellidae), and I hope to produce a monograph in a few years.

Daniel Geiger

Research Associate,
Santa Barbara Museum of Natural History,
2559 Puesta del Sol Road, 93105 Santa Barbara, CA.. USA.

Email: dgei...@usc.edu