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1 February 2012 Symposium on “Molluscan Biogeography: Perspectives from the Pacific Ocean” at the 76th Annual Meeting of the American Malacological Society, 2010
Peter B. Marko, Alan J. Kohn
Author Affiliations +

This issue of the American Malacological Bulletin includes fourpapers from the symposium on “Molluscan Biogeography: Perspectives From the Pacific Ocean,” held at the joint annual meeting of the American Malacological Society and the Western Society of Malacologists in San Diego, California, on June 29th 2010. We focused the symposium on the Pacific region due to the wide range of macro-oceanographic environments: long linear coastlines, one- and two-dimensional archipelagoes, remote islands, and vast areas of open ocean. Past contrasts between the distributions and diversity of molluscan faunas across these different types of habitats have provided numerous important insights into the factors that influence species ranges and patterns of species diversity (e.g., Taylor 1971, Valentine and Jablonski 1983, Perron and Kohn 1985, Vermeij 1987).

The symposium included presentations on species discrimination, speciation, life history evolution, island biogeography, and phylogeography; the papers published in this volume provide a broad representation of recent research in these subdisciplines. Alan Kohn analyzed life history and geographic range data with comparative methods to reevaluate the relationship between egg size, larval developmental mode, and geographic range in the gastropod genus Conus. Phylogenetically-controlled comparisons provided strong support for the hypothesis that species with smaller eggs (and longer planktonic developmental times) do in fact have larger geographic ranges, an interesting biogeographic relationship all on its own, but also a fundamental component in hypotheses about the relationships among larval mode of development, geographic range, and species longevity in the sea (Jablonski and Lutz 1983, Jablonski and Hunt 2006). In contrast, a second contribution by Tom Duda, Marielle Terbio, Gang Chen, Semoya Phillips, Amy M. Olenzek, Dan Chang, and David W. Morris synthesized phylogeographic patterns across the tropical Pacific among four species of Conus, emphasizing the importance of dispersal capability and recent gene flow as an explanation for an absence of obvious phylogeographic concordance among four widespread tropical Pacific species. Despite limited genetic differentiation across much of each of these species' ranges (presumably as a consequence of planktonic dispersal), the data also suggest that rare jump dispersal events and peripheral isolation have resulted in considerable genetic structure in geographically distant populations of some but not all species, and may represent an important route to speciation in the tropical Pacific.

Suzanne Williams, Andie Hall, and Piotr Kuklinski used a combination of DNA sequence data and shell shape data to investigate the power of Elliptic Fourier analysis to discriminate among living and fossil species of the turbinid gastropod genus Lunella from the tropical western Pacific and Indian oceans. They reported that morphological divergence is greatest between sympatric taxa.

Christine Parent's conceptually-related paper evaluated the contribution of within-island speciation to patterns of diversity among three lineages of terrestrial snails: the Galápagos Bulimulidae, the Hawaiian Succineidae, and the Hawaiian Achatinellinae. Parent showed that within-island speciation has contributed substantially to patterns of species diversity in each archipelago but that the historical factors associated with speciation within islands appear to differ among the taxa, with either island size or habitat heterogeneity having the greatest influence over rates of speciation within islands. The surprisingly large amount of within-island speciation inferred for each of these lineages emphasizes the need for models that incorporate speciation into formal quantitative theories of island biogeography (Rosindell and Phillimore2011).

Despite the variety of ideas, hypotheses, and questions that each of the published papers addressed, together they demonstrate the importance of studying biogeographic processes on different spatial and taxonomic scales. In Conus, Duda et al.'s conclusions about the stochastic nature of long distance dispersal that undoubtedly characterize the biogeographic histories of many species in the tropical Pacific complements the more deterministic relationship between dispersal potential and range size that has emerged from Kohn's work (e.g. Vermeij 1987, Palumbi et al. 1997, Lessios and Robertson 2006). Parent's focus on within-island diversification processes and Williams et al.'s (2011) suggestions about sympatric divergence together indicate that even though most molluscan speciation is likely initiated in allopatry, the small-scale habitat heterogeneity and transient geographic isolation that initiates divergence probably results in many opportunities for ecological interactions between recently split species, which may cause strong divergent selection on morphological, ecological, and behavioral traits (e.g. Marko 2005, Parent and Crespi 2009, Pfennig and Pfennig 2010, Rundell 2011, Krug 2011). If this is how speciation often proceeds in marine organisms (perhaps most often for linearly distributed nearshore species, see Valentine and Jablonski 1983), the implications for interpreting patterns of morphological change in the fossil record are potentially profound.

In addition to the published papers, other symposium participants presented work on other topics relevant to molluscan biogeography in the Pacific. David Jacobs discussed interoceanic transport in the trematode Parorchis and the gastropods Cerithidea and Nutricola, presumably accomplished by birds. Cynthia Trowbridge discussed biogeographic patterns of diversity among north Pacific saccoglossans, Doug Eernisse evaluated the significance of parapatric distributions towards understand patterns of diversification in eastern Pacific chitons, and Peter Marko reviewed the biogeographic and evolutionary responses of eastern Pacific molluscs to Pleistocene climate change.

The symposium highlighted the need for additional spatio-temporal perspectives on biogeographic processes, particularly those leading to speciation and diversification. Too few studies have combined fine-scale sampling of diverging populations and species with complementary studies of the fossil record. Patterns of sudden morphological change in the fossil record could represent peripatric speciation as envisioned by Eldredge and Gould (1972), but could also reflect other processes such as colonization of more distantly related species (Glaubrecht 2011), secondary contact and character displacement (Marko 2005), and taxon cycles (Ricklefs and Bermingham 2002). Studying extinction rates over evolutionary timescales is impossible without examination of the fossil record (Quental and Marshall 2010, Rabosky 2010, Losos 2011), and the potential for extinction to complicate histories inferred strictly from neontological data is potentially high; incomplete taxon sampling of living species alone is a problem in many neontological studies (Marko and Jackson 2001, Alroy 2002, Agapow et al. 2004, Isaac and Purvis 2004, Moran 2004, Laurin 2010). This call for more integration between neontological and paleontological perspectives is easier said than done: the taxa with the very best fossil records are often those that live in habitats that are hard to access in the Recent (sediments and deep water). Nevertheless, malacologists are uniquely poised to address biogeographic questions from a wide range of perspectives.

We are grateful to the authors who contributed papers to this volume and to all participants at the meeting in San Diego. We would like to thank Doug Eernisse for planning the meeting and for inviting us to organize a symposium. We thank Colleen Winters and Ken Brown for their editorial assistance and for facilitating publication of these papers in the American Malacological Bulletin. The symposium was funded by the American Malacological Society.

LITERATURE CITED

1.

P. Agapow , O. R. P. Binida-Emonds , K. A. Crandall , J. L. Gittleman , G. M. Mace , J. C. Marshall , and A. Purvis . 2004. The impact of species concept on biodiversity studies. The Quarterly Review of Biology 79: 161–179. Google Scholar

2.

J. Alroy 2002. How many named species are valid? Proceedings of the National Academy of Sciences U.S.A. 99: 3706–3711. Google Scholar

3.

N. Eldredge and S. J. Gould . 1972. Punctuated equilibria: An alternative to phyletic gradualism. In : T. Schopf , ed., Models in Paleobiology. Freeman Cooper, San Francisco, California. Pp. 82–115. Google Scholar

4.

N. J. B. Isaac and A. Purvis . 2004. The ‘species problem’ and testing macroevolutionary hypotheses. Diversity and Distributions 10: 275–281. Google Scholar

5.

D. Jablonski , and G. Hunt . 2006. Larval ecology, geographic range, and species survivorship in Cretaceous mollusks: Organismic vs. species-level explanations. American Naturalist 168: 556– 564. Google Scholar

6.

D. Jablonski and R. A. Lutz . 1983. Larval ecology of marine benthic invertebrates: Paleobiological implications. Biological Reviews 58:21–89. Google Scholar

7.

P. J. Krug 2011. Patterns of speciation in marine gastropods: A review of the phylogenetic evidence for localized radiations in the sea. American Malacological Bulletin 29: 169–186. Google Scholar

8.

M. Laurin 2010. The subjective nature of Linnaean categories and its impact in evolutionary biology and biodiversity studies. Contributions to Zoology 79: 131–146. Google Scholar

9.

H. A. Lessios and D. R. Robertson . 2006. Crossing the impassable: Genetic connections in 20 reef fishes across the eastern pacific barrier. Proceedings of the Royal Society, B, Biological Sciences 273: 2201–2208. Google Scholar

10.

J. B. Losos 2011. Seeing the forest for the trees: The limitations of phylogenies in comparative biology. The American Naturalist 177: 709–727. Google Scholar

11.

P. B. Marko 2005. An intraspecific comparative analysis of character divergence between sympatric species. Evolution 59: 554–564. Google Scholar

12.

P. B. Marko and J. B. C. Jackson . 2001. Patterns of morphological diversity among Recent and fossil tropical American geminate bivalves in the family Arcidae. Journal of Paleontology 75: 590–606. Google Scholar

13.

A. L. Moran 2004. Egg size evolution in tropical American arcid bivalves: The comparative method and the fossil record. Evolution 58: 2718–2733. Google Scholar

14.

S. R. Palumbi , G. G. Grabowski , T. Duda , L. Geyer , and N. Tachino . 1997. Speciation and population genetic structure in tropical Pacific sea urchins. Evolution 51: 1506–1517. Google Scholar

15.

C. E. Parent and B. J. Crespi . 2009. Ecological opportunity in adaptive radiation of Galapagos endemic land snails. American Naturalist 174: 898–905. Google Scholar

16.

F. E. Perron and A. J. Kohn . 1985. Larval dispersal and geographic distribution in coral reef gastropods of the genus Conus. Proceedings of the Fifth International Coral Reef Congress, Tahiti, French Polynesia 4: 95–100. Google Scholar

17.

D. W. Pfennig and K. S. Pfennig . 2010. Character displacement and the origins of diversity. American Naturalist 176 (Supplement 1): 26–44. Google Scholar

18.

T. B. Quental and C. R. Marshall . 2010. Diversity dynamics: Molecular phylogenies need the fossil record. Trends in Ecology and Evolution 25: 434–441. Google Scholar

19.

D. L. Rabosky 2010. Extinction rates should not be estimated from molecular phylogenies. Evolution 64: 1816–1824. Google Scholar

20.

R. E. Ricklefs and E. Bermingham . 2002. The concept of the taxon cycle in biogeography. Global Ecology & Biogeography 11: 353–361. Google Scholar

21.

J. Rosindell and A. B. Phillimore . 2010. A unified model of island biogeography sheds light on the zone of radiation. Ecology Letters 14: 552–560. Google Scholar

22.

R. J. Rundell 2011. Snails on an evolutionary tree: Gulick, speciation, and isolation. American Malacological Bulletin 29: 145–158. Google Scholar

23.

J. D. Taylor 1971. Reef associated molluscan assemblages in the western Indian Ocean. In : D. R. Stoddard and C. M. Yonge , eds., Regional Variation in Indian Ocean Coral Reefs. Academic Press, New York. Pp. 509–536. Google Scholar

24.

J. W. Valentine and D. Jablonski . 1983. Speciation in the shallow sea: General patterns and biogeographic controls. In : R. W. Sims , J. H. Price , and P. E. S. Whalley , eds., Evolution, Time and Space: The Emergence of the Biosphere. Systematics Association Special Volume 23. Academic Press, London. Pp. 201–226. Google Scholar

25.

G. J. Vermeij 1987. The dispersal barrier in the tropical Pacific: Implications for molluscan speciation and extinction. Evolution 41: 1046–1058. Google Scholar

26.

S. Williams , D. Apte , T. Ozawa , F. Kaligis , and T. Nakano . 2011. Speciation and dispersal along continental coastlines and island arcs in the Indo-West pacific turbinid gastropod genus Lunella. Evolution 65: 1752–1771. Google Scholar
Peter B. Marko and Alan J. Kohn "Symposium on “Molluscan Biogeography: Perspectives from the Pacific Ocean” at the 76th Annual Meeting of the American Malacological Society, 2010," American Malacological Bulletin 30(1), 159-161, (1 February 2012). https://doi.org/10.4003/006.030.0114
Published: 1 February 2012
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