The MUSSELp Literature

Preliminary review of the freshwater mussels (Mollusca: Bivalvia: Unionoida) of northern Africa, with an emphasis on the Nile

by Daniel L. Graf & Kevin S. Cummings

Published 2007, Journal of the Egyptian German Society of Zoology 53D: 89-118. Click here to download a pdf of this article.

Abstract. The freshwater mussels (Mollusca: Bivalvia: Unionoida) of northern Africa, including the Nile Basin, have received a good deal of attention in recent decades, but published reviews/revisions are at odds with each other and with our own museum work. We undertook a preliminary reevaluation of the species of the region to provide a consistent baseline for future research efforts and to spark interest in the study of freshwater mussels among Egyptian zoologists. Twenty-nine species in four families are reported to occur in Northern Africa; 26 in three families in the Nile and Lake Turkana. The Nile is an area of overlap between the southern extent of the Palearctic fauna and the northern limit of the Afrotropical fauna. The traditional concept of the species Chambardia wahlbergi (Krauss, 1848) is herein regarded as four distinct lineages in the region: Ch. wahlbergi hartmanni (von Martens, 1866), Ch. bourguignati Bourguignat, 1885, Ch. letourneuxi Servain, 1890 and Aspatharia marnoi (Jickeli, 1874). We provide an annotated species list of all unionoid species in northern Africa, and Nile species are illustrated. Areas of future research potential are discussed.

Review of the systematics and global diversity of freshwater mussel species (Bivalvia: Unionoida)

by Daniel L. Graf & Kevin S. Cummings

Published 2007, Journal of Molluscan Studies 73: 291-314.

Abstract. Freshwater mussels (Bivalvia: Unionoida) are interesting because of their unique life cycles, global aggregate distribution and ancient origin. They are also of practical importance due to their worldwide, imperiled status. Of utmost utility for their continued study are a modern assessment of global and regional species diversity and a natural classification that reflects phylogenetic patterns. The freshwater malacological community has taken steps toward satisfying the latter of these requirements, but a consensus census of mussel species has not been published since Fritz Haas’s revisions of the late 1960s. We set out to describe the species-level diversity of the Unionoida by reviewing the secondary literature and developing a comprehensive taxonomic database. Each valid species was assigned to one or more geographical regions (i.e. Nearctica, Neotropica, Afrotropica, Palearctica, Indotropica and Australasia) and one or more subregions, and each valid genus was assigned to the lowest possible level in a classification derived from our own, recent phylogenetic analyses. Based upon a consensus of numerous regional works, our global estimate of freshwater mussel diversity is 840 species. Regional diversity was determined as follows: Nearctica: 302 spp., Neotropica: 172, Afrotropica: 85, Palearctica: 45, Indotropica: 219 and Australasia: 33. The largest family is the Unionidae, with 674 species. However, the classification of that taxon is currently in flux, and many genera (corresponding to 225 spp.) were assigned to incertae sedis geographical assemblages. Diversity patterns are discussed, and it is suggested that reevaluation of these faunas with modern methods will likely increase recognized species diversity, especially on the southern continents. Our checklist and classification of freshwater mussel species is included as an appendix and mirrored on the MUSSEL Project Web Site (http://www.mussel-project.net/).

Click here to visit the online version of this project, Unionoida cum Grano Salis.

Palearctic freshwater mussel (Mollusca: Bivalvia: Unionoida) diversity and the Comparatory Method as a species concept

by Daniel L. Graf

Published 2007, Proceedings of the Acadedmy of Natural Sciences of Philadelphia 156: 71-88.

Palaeoheterodonta Diversity (Mollusca: Trigonioida + Unionoida): What We Know and What We Wish We Knew About Freshwater Mussel Evolution

by Daniel L. Graf & Kevin S. Cummings

Published 2006, Zoological Journal of the Linnean Society 148(3): 343-394.

Abstract. The Palaeoheterodonta is a diverse clade consisting of the freshwater bivalve order Unionoida and its marine sister group, Neotrigonia. Neotrigonia is the sole surviving genus of the Trigonioida, known from only 6 species in Australian waters. Unionoids (freshwater mussels), in contrast, are widespread on all continents except Antarctica and represented by ca. 900 species. Discussion is biased towards the freshwater mussel condition, but Neotrigonia is crucial as a “living fossil” for establishing the plesiomorphic states of unionoid synapomorphies. Neotrigonia retains many of the characters of the ancestral heteroconch.

Our object is to provide evidentiary support for the natural classification of the extant Palaeoheterodonta. A supermatrix of 50 taxa and 1183 characters was constructed from 62 previously published DNA sequences of mitochondrial cytochrome oxidase subunit I and 28S nuclear ribosomal DNA, 15 novel sequences, and 59 morphological characters. Published COI sequences for Coelatura aegyptiaca, Pseudomulleria dalyi and Obliquaria reflexa were treated as potentially problematic due to their (1) inconsistency under different methodological assuptions and (2) conflict with other data sets. Each partition was analyzed under the criterion of parsimony separately and in combined analyses; analyses were run both with and without the problematic sequences.

Based upon our “Combined Evidence” topology (with problematic sequences excluded), the Unionoida is monophyletic based upon 8 synapomorphies, including larval parasitism, brood protection and restriction to freshwater. The order is comprised of six families in two superfamilies, Unionoidea and Etherioidea: ((Unionidae + Margaritiferidae) + (Hyriidae + (Etheriidae + (Mycetopodidae + Iridinidae)))). The morphological synapomorphies of these taxa are discussed with an emphasis upon both diagnosing taxa and highlighting areas of ambiguity and missing data. Three appendices provide descriptions of the morphological characters (I), a diagnosis of apomorphies for all branches of the phylogeny (II) and a family-level classification of the extant Palaeoheterodonta, including a complete synonymy (III).

Unpublished Trees

Morphology Only, strict consensus of 34489 trees @ 126 steps each	28S Only, strict consensus of 904 trees @ 544 steps each	COI Only, problematic sequences included, strict consensus of 69 trees @ 2307 steps each	COI Only, problematic sequences excluded, strict consensus of 27 trees @ 2137 steps each

Data Matrix. grafcummings_combo.txt. Diagnoses of morphological characters.

Tree Files. morphology_trees.txt | coi_trees.txt (problematic sequences included) | coi_trees_x.txt (problematic sequences excluded) | 28s_trees.txt | molecular_trees.txt (problematic sequences included) | molecular_trees_x.txt (problematic sequences excluded) | combined_evidence_trees.txt (problematic sequences included) | combined_evidence_trees_x.txt (problematic sequences excluded)

Click here to download a zipped archive the data, tree files and logs from all parsimony analyses.

The Molluscan Literature: Geographic and Taxonomic Works

by Charles F. Sturm, Richard Petit, Timothy A. Pearce, Kevin Cummings, Enrico Schwabe & Andreas Wanniger

Published 2006, Chapter 9 in C.F. Sturm, T.A. Pearce & A. Valdés (eds.), The Mollusks: A Guide to their Study, Collection, and Preservation. American Malacological Society, Universal Publishers. pp. 111-146.

"This chapter is a general guide to collecting, identifying, and curating freshwater mussels based upon our years of experience in the field. It is not meant to be an exhaustive guide but it does contain information learned through trial and error and the experience of others in the field."

Unionoida: Freshwater Mussels

by Kevin S. Cummings & Arthur E. Bogan

Published 2006, Chapter 25 in C.F. Sturm, T.A. Pearce & A. Valdés (eds.), The Mollusks: A Guide to their Study, Collection, and Preservation. American Malacological Society, Universal Publishers. pp. 313-325.

"This chapter is a general guide to collecting, identifying, and curating freshwater mussels based upon our years of experience in the field. It is not meant to be an exhaustive guide but it does contain information learned through trial and error and the experience of others in the field."

Freshwater mussels (Mollusca: Bivalvia: Unionoida) of Angola, with description of a new species, Mutela wistarmorrisi

by Daniel L. Graf & Kevin S. Cummings

Published 2006, Proceedings of the Academy of Natural Sciences of Philadelphia 155: 163-194.

Abstract. The aquatic fauna of the Angola region in southwestern Africa, including the Cuanza (= Kwanza), Cunene, Okavango, upper Zambezi, Cassai (= Kasai) and lower Congo basins, is poorly known. The freshwater mussels (Mollusca: Unionoida) of the region have received little attention, and then usually as fringes to the Congo and Zambezi-Okavango systems. All available freshwater mussel specimens from thirteen major mollusk collections were examined and, along with a literature review, form the basis for this checklist. Twenty-three species in three families (Etheriidae, Iridinidae and Unionidae) are recognized from the Angola region, eight of which are newly recognized in the region or had not been treated as valid in recent revisions (Mandahl-Barth, 1988; Daget, 1998). One of these species, Mutela wistarmorrisi, is new to science and described herein. Chambardia welwitschi (Morelet), a widely recognized subspecies, is elevated to species-level status, and four more names are resurrected to valid status from synonymy: Mutela langi Pilsbry & Bequaert, Chambardia moutai (Dartevelle), Coelatura stagnorum (Dautzenberg) and C. rotula Pilsbry & Bequaert. Mutela legumen (Rochebrune) is recognized as the senior synonym for the species formerly referred to as Mutela carrei (Putzeys), and the known range of Aspatharia subreniformis (Sowerby) is expanded to include the Cunene, Okavango and Zambezi basins. Figures of each species are provided, and known distributions and persistent taxonomic issues are discussed. An appendix lists geocodes for localities associated with specimen records.

PDF. grafcummings2006_angola.2006

Click here for the online version of the checklist. The data have also been incorporated in the ZAMBONGO database, Freshwater Mussels of the Congo & Zambezi Basins.

The Global Decline of Nonmarine Mollusks

by Lydeard, C., R.H. Cowie, W.F. Ponder, A.E. Bogan, P. Bouchet, S.A. Clark, K.S. Cummings, T.J. Frest, O. Gargominy, D.G. Herbert, R. Hershler, K.E. Perez, B. Roth, M. Seddon, E.E. Strong & F.G. Thompson

Published 2004, Bioscience 54(4): 321-330.

Invertebrate species represent more than 99% of animal diversity; however, they receive much less publicity and attract disproportionately minor research effort relative to vertebrates. Nonmarine mollusks (i.e., terrestrial and freshwater) are one of the most diverse and imperiled groups of animals, although not many people other than a few specialists who study the group seem to be aware of their plight. Nonmarine mollusks include a number of phylogenetically disparate lineages and species-rich assemblages that represent two molluscan classes, Bivalvia (clams and mussels) and Gastropoda (snails, slugs, and limpets). In this article we provide an overview of global nonmarine molluscan biodiversity and conservation status, including several case studies documenting the diversity and global decline of nonmarine mollusks. We conclude with a discussion of the roles that mollusks and malacologists should play in conservation, including research, conservation management strategies, and education and outreach.

Molecular Phylogenetic Analysis of Two Problematic Freshwater Mussel Genera (Unio and Gonidea) and a Re-Evaluation of the Classification of the Nearctic Unionidae (Bivalvia: Palaeoheterodonta: Unionoida)

by Daniel L. Graf

Published 2002, Journal of Molluscan Studies 68: 65-71.

Abstract. The freshwater mussel genera Unio (Palearctic) and Gonidea (Pacific Nearctic drainages) have been difficult to place in the classification of the Unionidae. This has been principally due to (1) a lack of appreciation for derived vs. ancestral characters and (2) a decoupling of taxonomy from evolutionary theory. To test cladistically the positions of Unio and Gonidea relative to the well-studied Nearctic genera of the Atlantic/Gulf of Mexico drainages, partial nuclear large-ribosomal subunit (28S rDNA) sequences were obtained from representative freshwater mussel lineages, including three genera from Southeast Asia. The phylogenetic reconstruction differs from the traditional placement of Unio among the Ambleminae; instead, Unio falls sister to anodontine mussels. Gonidea is sister to the remaining Nearctic Ambleminae, and these are distinct from the Asian “amblemine” genera. Based on these results, the classification of the New World Unionidae is updated [i.e., Unioninae (= Unionini + Anodontini) + Ambleminae], and synapomorphies of the family are discussed.

Data. graf2002_28S.txt

Evolutionary relationships among the higher taxa of freshwater mussels (Bivalvia: Unionoida): inferences on phylogeny and character evolution from analyses of DNA sequence data

by Walter R. Hoeh, Arthur E. Bogan, Kevin S. Cummings & Sheldon I. Guttman

Published 2002, Malacological Review 31/32(2): 123-141.

Abstract. Doubt regarding the history of phylogenies within the Unionoida have hampered attempts to understand evolution within the group and to establish a stable classification system. To test alternative hypotheses of unionoid phylogeny, 630 base pairs of DNA sequence for the cytochrome c oxidase subunit I (COI) gene were obtained from 30 species representing the higher taxa within the Unionoida (=ingroup) and one species (Neotrigonia margaritacea) representing the Trigonioida (=outgroup). Both parsimony and neighbor-joining algorithms were employed to generate phylogenetic trees from the COI nucleotide sequences. All phylogenetic analyses produced trees with the following topology: ((((Unionidae [except Coelatura], Margaritiferidae), Coelatura), (Mutelidae, Mycetopodidae)), Hyriidae). The Hyriidae, Margaritiferidae, Mutelidae, Mycetopodidae, and Etherioidea were supported as monophyletic groups while the Unionidae and Unionoidea were judged paraphyletic. These phylogenetic relationships suggest that (1) hyriids, rather than margaritiferids, are a product of the most basal cladogenic event in the ancestral unionoid lineage, (2) the lineage ancestral to unionoids arose on one of the Gondwanan landmasses, (3) the glochidium is the ancestral unionoid larval type, and (4) endobranchial brooding is ancestral in unionoids followed by a transition to tetrageny which subsequently gave rise to ectobranchy.

A Phylogenetic Perspective on the Evolution of the Unionoida (Mollusca Bivalvia Palaeoheterodonta): Using Pattern to Test Hypotheses of Macroevolutionary Process

by Daniel L. Graf

Ph.D. dissertation defended April 2001, University of Michigan, Ann Arbor, Michigan (available on-line).

Abstract. The Unionoida, commonly known as freshwater pearly mussels or naiades, is a diverse, ancient order of strictly continental, freshwater bivalves. Most previous discussions of freshwater mussel evolution pre-dated the widespread acceptance of phylogenetic systematics and modern biogeographic theory. As a result, our understanding of the macroevolutionary processes behind the present diversity has been limited to untested narratives. This is unfortunate, as the age, distribution, and diversity of freshwater mussels makes them useful for studying divergences ranging from the Mesozoic to the Quaternary.

This dissertation documents four cladistic studies of the Unionoida. Because no single character or taxon set is appropriate across all levels of freshwater mussel phylogeny, four specific topics are addressed using separate but overlapping analyses of morphology and mitochondrial and nuclear DNA. The first analysis (Chapter 2) applies a strictly morphological character set to test the position of the Hyriidae among the Unionoida. Chapters 3 and 4 address the phylogeny and brooding character evolution among the Nearctic Unionidae using a combined (mitochondrial + nuclear) character set. Chapter 5 returns to the Hyriidae of the Australasian and Neotropical regions, using molecular characters to test hypotheses of biogeographic process. Chapter 6, the last analytical chapter, tests the position of the Nearctic genera relative to the global Unionoidea.

The seventh chapter reviews the macroevolution of the Unionoida from a phylogenetic perspective based on the results of these four studies.

Molecular phylogenetic analysis of 28S rDNA supports a Gondwanan origin for Australasian Hyriidae (Mollusca: Bivalvia: Unionoida)

By Daniel L. Graf & Diarmaid Ó Foighil

Published 2000, Vie Milieu 50: 245-254.

Abstract. The Hyriidae (Mollusca: Bivalvia: Unionoida) have a disjunct distribution, occurring on South America, Australia, and New Zealand. Most previous macroevolutionary studies of the Hyriidae pre-dated widespread acceptance of both continental drift and phylogenetic systematics. For this study, we applied molecular phylogenetic techniques to test the hypothesis that the observed disjunction of Australasian hyriids across the Tasman Sea is due to the disintegration of Gondwanaland (>80 million years ago). We sequenced a fragment of 28S rDNA for representative hyriid Velesunionini (Australia), Hyridellini (Australia and New Zealand), and Hyriinae (South America) and for outgroups belonging to the unionoid families Margaritiferidae and Unionidae. The topology of the single 28S tree [i.e., (Margaritiferidae, Unionidae, (Velesunionini, (Hyridellini, Hyriinae)))] recovered by both maximum parsimony and maximum likelihood did not support a monophyletic Australasian clade, and the branch lengths were consistent with Mesozoic vicariance. We also acquired COI sequences for the Australian subset of mussels to corroborate the 28S branch lengths. Our results suggest that (1) the Hyriidae pre-date the break up of Gondwanaland and (2) the New Zealand Hyridellini are relics rather than colonizers. Alternative long-distance dispersal hypotheses are discussed in the context of our results, historical geology, and mussel life history.

Data. grafofoighil2000b_28S.txt | grafofoighil2000b_coi.txt

The Evolution of Brooding Characters Among the Freshwater Pearly Mussels (Mollusca: Bivalvia: Unionoidea) of North America

by Daniel L. Graf & Diarmaid Ó Foighil

Published 2000, Journal of Molluscan Studies 66: 157-170.

Abstract. Brooding characters have figured prominently in the classification of North American freshwater pearly mussels (Bivalvia: Unionoidea). The purpose of our study was to phylogenetically evaluate hypotheses of brooding character evolution in order to test homology statements suggested by earlier taxonomic systems of the Unionoidea. Parsimony analysis of partial COI sequences from 29 species of freshwater mussels and 13 outgroups were used to derive a phylogeny. Thirteen brooding characters (e.g., brooding period, marsupium arrangement, structure of interlamellar septa, etc.) were traced onto this phylogeny. Results indicate that long-term brooding (bradytictia) is the derived state among North American freshwater mussels; short-term brooding (tachytictia) is plesiomorphic. Bradytictia evolved independently in the Anodontinae and Lampsilini, with unique morphological modifications derived in those clades to facilitate long-term brooding. The evolution of bradytictia among temperate clades is discussed.

Data. grafofoighil2000a_coi.txt

The Etherioidea Revisited: A Phylogenetic Analysis of Hyriid Relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida)

By Daniel L. Graf

Published 2000, Occasional Papers of the University of Michigan Museum of Zoology (729): 1-21.

Abstract. Almost all freshwater pearly mussels (Order Unionoida) have one of two types of parasitic larvae, either glochidia or lasidia. The most widely accepted hypothesis of freshwater mussel higher classification divides the order into two superfamilies, the Unionoidea and Etherioidea [= Muteloidea], based solely upon larval type. To test this hypothesis, specifically the relationships of the Hyriidae (which have glochidia), a morphological data set compiled from both larval and adult life history stages was analyzed phylogenetically using parsimony. Results indicate that hyriids, despite their development including a parasitic glochidium, share a more recent common ancestor with the Etherioidea than with any unionoidean. The Etherioidea (Hyriidae, (Iridinidae, Etheriidae)) is diagnosed by at least three adult anatomical synapomorphies. The lasidium-type larva is hypothesized to be derived from glochidia. The bearing of these results on the biogeography, character evolution, and classification of the Unionoida is discussed.

Data. graf2000_morph.txt

Conservation Status of Freshwater Mussels of the United States and Canada

by Williams, J.D., M.L. Warren, Jr., K.S. Cummings, J.L. Harris & R.J. Neves

Published 1993, Fisheries 18(9): 6-22.

Abstract. The American Fisheries Society (AFS) herein provides a list of all native freshwater mussels (families Margaritiferidae and Unionidae) in the United States and Canada. This report also provides state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution of freshwater mussels. The list includes 297 native freshwater mussels, of which 213 taxa (71.7%) are considered endangered, threatened, or of special concern. Twenty-one taxa (7.1%) are listed as endangered but possibly extinct, 77 (25.9%) as endangered but extant, 43 (14.5%) as threatened, 72 (24.2%) as of special concern, 14 (4.7%) as undetermined, and only 70 (23.6%) as currently stable. The primary reasons for the decline of freshwater mussels are habitat destruction from dams, channel modification, siltation, and the introduction of nonindigenous mollusks. The high numbers of imperiled freshwater mussels in the United States and Canada, which harbor the most diverse fauna in the world, portend a trajectory toward an extinction crisis that, if unchecked, will severely impoverish one of our richest components of aquatic biodiversity.

Page last updated 2 January 2007.