Morphological Variation in the Horsehoe Crab Limulus polyphemus

Riska, Bruce

doi:10.2307/2408237

Cited by 38 publications

(17 citation statements)

References 10 publications

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“…This study, which represents the first rangewide survey of nuclear DNA variation in any horseshoe crab, does not support the null hypothesis of a homogeneous gene pool for L. polyphemus inhabiting the Atlantic coast of North America. The pattern of genetic variation observed is consistent with that identified previously in surveys of morphological variation (Shuster 1979;Riska 1981). In their entirety, these research findings suggest a series of discontinuities across the species' range that could indicate regional adaptive significance or reflect vicariant geographic events.…”

Section: Discussionsupporting

confidence: 89%

Regional Differentiation and Sex‐Biased Dispersal among Populations of the Horseshoe Crab Limulus polyphemus

et al. 2005

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Fourteen microsatellite DNA loci were surveyed in 892 horseshoe crabs Limulus polyphemus collected from 21 sites ranging from Franklin, Maine, to the Yucatán Peninsula, Mexico. This rangewide survey revealed a high degree of genetic diversity (up to 50 alleles per locus) and heterozygosity (up to 97.2%). There appears to be substantial gene flow between each population and its nearest neighbors. The correlation of genetic distance and geographic distance supports isolation by distance as a mechanism underlying the structure of L. polyphemus along the Atlantic coast of North America. Two statistical descriptors, mean assignment percentage and assignment variance, suggested the presence of male-biased dispersal throughout the study area. Within the continuum of isolation by distance and in the presence of male-biased dispersal, the clustering of specific collections on a tree of genetic distances and hierarchical gene diversity analyses demonstrate discrete regional units. These results suggest defining four management units within the United States: the Gulf of Maine, mid-Atlantic, Atlantic Florida, and Gulf Florida. Further sampling is needed, particularly from North Carolina to the southernmost tip of Atlantic Florida, to test this hypothesis. Multilocus assignment tests indicate a high probability of correctly assigning individuals to the proposed management unit from which they were collected and could serve as a useful tool for identifying the source of animals that are caught at sea.

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Section: Discussionsupporting

confidence: 89%

Regional Differentiation and Sex‐Biased Dispersal among Populations of the Horseshoe Crab Limulus polyphemus

et al. 2005

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“…Thus, in Limulus polyphemus, the level of allozyme heterozygosity (H = 0.057) proved similar to mean estimates for many other animals (Selander et al 1970); and, levels and patterns ofintraspecific differentiation in mitochondrial DNA (mtDNA) were similar to those of several other inverte-brate and vertebrate species inhabiting the same coastal range in the southeastern United States (Saunders et al 1986;Avise 1992). This "normalcy" of genetic variability within and among populations of L. polyphemus suggests that consensus patterns ofmolecular versus morphotypic evolution in horseshoe crabs may be conspicuously decoupled (but see Riska [1981] and Shuster [1982], who documented variability and geographic differentiation in the morphological traits of L. polyphemus as well).…”

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confidence: 55%

A Speciational History of “Living Fossils”: Molecular Evolutionary Patterns in Horseshoe Crabs

1994

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Abstract.-Horseshoe crabs' exceptional morphological conservatism over the past 150 My has led to their reputation as "living fossils," but also has served to obscure phylogenetic relationships within the complex. Here we employ nucleotide sequences from two mitochondrial genes to assess molecular evolutionary rates and patterns among all extant horseshoe crab species. The American species Limulus polyphemus proved to be the sister taxon to a clade composed of the Asiatic species Tachypleus gigas, T. tridentatus, and Carcinoscorpius rotundicauda, whose relationships inter se were not resolved definitively. Both absolute and relative rate tests suggest a moderate slowdown in sequence evolution in horseshoe crabs. Nonetheless, dates of the lineage separations remain uncertain primarily because of reservations about molecular-clock calibrations resulting from large rate variances at examined loci across Arthropods and other animal lineages,as inferred in this and prior studies. Thus, ironically, separation dates as estimated by molecular evidence in general may remain most insecure in taxonomic groups for which such information is needed most-those lacking strong biogeographic or fossil benchmarks for internal-clock calibrations. In any event, the current results show that large numbers of molecular characters distinguish even these most morphologically conservative of organisms. Furthermore, comparisons against previously published mitochondrial sequence data in the morphologically dynamic hermit crab-king crab complex demonstrates that striking heterogeneity in levels of morphotypic differentiation can characterize Arthropod lineages at similar magnitudes of molecular divergence.

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“…Horseshoe crabs spawn in estuaries, laying eggs in sand (Leschen et al 2006), and their larvae have limited dispersal even within the estuary (Botton and Loveland 2003). Smaller adults are found at both the northern and southern extremes (Riska 1981;Sekiguchi and Shuster 2009), and horseshoe crabs from southern Florida cannot survive temperatures typical of Massachusetts, and vice versa (Mayer 1914;Sekiguchi and Shuster 2009). Abundance, harvest pressure, population trends, and regulations vary greatly among the regions (ASMFC 1998b;Smith et al 2009).…”

Section: Invertebrate Speciesmentioning

confidence: 99%

Managing a Marine Stock Portfolio: Stock Identification, Structure, and Management of 25 Fishery Species along the Atlantic Coast of the United States

McBride

2014

N American J Fish Manag

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In this review, stock identification methods used, resulting stock numbers and boundaries, and assessment and management context were explored for all 25 species managed by the Atlantic States Marine Fisheries Commission (ASMFC). This included invertebrates and vertebrates distributed between Maine and Florida, with a few species ranging across all these states and some ranging into the Gulf of Mexico and the Canadian Maritimes. The effects of larval dispersal or mixing of adults in the marine environment were evident. Marine and catadromous spawners were recognized and treated as a unit stock (e.g., northern shrimp Pandalus borealis, American Eel Anguilla rostrata, Atlantic menhaden Brevoortia tyrannus, Bluefish Pomatomus saltatrix, Tautog Tautoga onitis), a metapopulation (American lobster Homarus americanus, Atlantic Herring Clupea harengus), or two stocks, north and south of Cape Hatteras, a major biogeographic boundary, (Black Sea Bass Centropristis striata, Scup Stenotomus chrysops, Red Drum Sciaenops ocellatus, Summer Flounder Paralichthys dentatus). Estuarine and anadromous spawners were structured and managed at a finer spatial scale (horseshoe crab Limulus polyphemus, Atlantic Sturgeon Acipenser oxyrinchus, American Shad Alosa sapidissima and the river herrings Blueback Herring A. aestivalis and Alewife A. pseudoharengus, and Spotted Seatrout Cynoscion nebulosus). A broad suite of stock identification methods have been applied to ASMFC species and reviewed here in five categories: life history traits, other phenotypic traits, genetic traits, natural marks, and applied marks. An interdisciplinary mix of methods has been achieved for a few species (Striped Bass Morone saxatilis, Winter Flounder Pseudopleuronectes americanus), but only a few or no stock identification methods have been applied to others (Spiny Dogfish Squalus acanthias, Hickory Shad A. mediocris, Spot Leiostomus xanthurus, Spanish Mackerel Scomberomorus maculatus). Clinal phenotypic variation has contributed to several long-standing debates about stock structure; some of these have been recently reevaluated as a unit stock (Atlantic Croaker Micropogonias undulatus, Weakfish Cynoscion regalis), and others are still debated. For some ASMFC species, other priorities (e.g., bycatch) dominate the uncertainty of the assessment or management process. Otherwise, stock identification remains a research priority for most of these species. Continued research of this subject should consider (1) research priorities tabulated by ASMFC review panels, (2) strategic use of interdisciplinary stock identification methods, (3) use of experiments or reaction norms to separate phenotypes from genotypes, (4) genetic surveys at a seascape scale, (5) demonstration of contingent (nongenetic) structure and its implications for management, and (6) simulation modeling. Obstacles to adopting finer-scale structure into assessments or management of ASMFC fisheries include: (1) multiple stock units are apparent but boundaries are not clear, (2) monitoring requirements for...

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Morphological Variation in the Horsehoe Crab Limulus polyphemus

Cited by 38 publications

References 10 publications

Regional Differentiation and Sex‐Biased Dispersal among Populations of the Horseshoe Crab Limulus polyphemus

Regional Differentiation and Sex‐Biased Dispersal among Populations of the Horseshoe Crab Limulus polyphemus

A Speciational History of “Living Fossils”: Molecular Evolutionary Patterns in Horseshoe Crabs

Managing a Marine Stock Portfolio: Stock Identification, Structure, and Management of 25 Fishery Species along the Atlantic Coast of the United States

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