Quantifying Molluscan Body Size in Evolutionary and Ecological Analyses: Maximizing the Return on Data-Collection Efforts

Kosnik, Matthew A.; Jablonski, David; Lockwood, Rowan; Novack-Gottshall, Philip M.

doi:10.2110/palo.2006.p06-012r

Cited by 77 publications

(61 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Shell size was measured by taking three perpendicular measurements, the longest linear dimension (x), the next longest linear measurement perpendicular to the first measurement (y), and the length perpendicular to the first two measurements (z). Shell size was calculated as the geometric mean of x, y, and z (Kosnik et al 2006). Ethalia and Natica shell thickness was measured by taking several measurements along the outer aperture edge to determine a representative thickness.…”

Section: Methodsmentioning

confidence: 99%

Taphonomic bias and time-averaging in tropical molluscan death assemblages: differential shell half-lives in Great Barrier Reef sediment

Kosnik¹,

Hua²,

Kaufman³

et al. 2009

Paleobiology

View full text Add to dashboard Cite

Abstract.-Radiocarbon-calibrated amino acid racemization ages of 428 individually dated shells representing four molluscan taxa are used to quantify time-averaging and shell half-lives with increasing burial depth in the shallow-water carbonate lagoon of Rib Reef, central Great Barrier Reef, Australia. The top 20 cm of sediment contains a distinct, essentially modern assemblage. Shells recovered at depths from 25 to 125 cm are age-homogeneous and significantly older than the surface layer. Taxon age distributions within sedimentary layers indicate that the top 125 cm of lagoonal sediment is thoroughly mixed on a sub-century scale. The age distributions and shell half-lives of four taxa (Ethalia, Natica, Tellina, and Turbo) are found to be largely distinct. Shell half-lives do not coincide with any single morphological characteristic thought to infer greater durability, but they are strongly related to a combined durability score based on shell density, thickness, and shape. These results illustrate the importance of bioturbation in tropical sedimentary environments, indicate that age estimates in this depositional setting are sensitive to taxon choice, and quantify a taxon-dependent bias in shell longevity and death assemblage formation.

show abstract

Section: Methodsmentioning

confidence: 99%

Taphonomic bias and time-averaging in tropical molluscan death assemblages: differential shell half-lives in Great Barrier Reef sediment

Kosnik¹,

Hua²,

Kaufman³

et al. 2009

Paleobiology

View full text Add to dashboard Cite

show abstract

“…A linear dimension was chosen because it is the most direct measure of body mass available and because it correlates highly with other, more precise estimates of mass [19]. Within a guild, species have similar shapes, so that artefacts arising from differences in geometry are minimized.…”

Section: Methodsmentioning

confidence: 99%

Shifting sources of productivity in the coastal marine tropics during the Cenozoic era

Vermeij

2010

Proc. R. Soc. B.

View full text Add to dashboard Cite

Changes in the rates and sources of marine primary production over time are difficult to document owing to the absence of direct estimates of past productivity. Here, I use the maximum body sizes of the largest species in each of 23 tropical shallow-water marine molluscan guilds (groups of species with similar habits and trophic roles) to trace the relative importance of planktonic and benthic primary productivity from the Eocene (55 Ma) onwards. The largest members of guilds are least constrained in exploiting resources and therefore reflect the availability and accessibility of those resources most accurately. Maximum sizes of suspension-feeders and predators increased by a factor of 2.3 and 4.0, respectively, whereas those in four out of five herbivorous guilds declined. I interpret these patterns, which are discernible throughout the coastal tropics, to mean that primary production in the Eocene marine tropics was concentrated on the seafloor, as is the case today on offshore reefs and islands, and that the Miocene to the recent interval witnessed a dramatic increase in planktonic productivity along continental margins. The rise in planktonic fertility is best explained by an increase in nutrient supply from the land associated with intense global tectonic activity and more vigorous ocean mixing owing to cooling.

show abstract

“…For mammals, body size was measured in grams, drawing on a worldwide database (65). For bivalves, body size was the geometric mean of length and height (40); for gastropods, body size was maximum shell dimension (66). We compared median body mass and total latitudinal range (in degrees) for the named morphogenus to the ''total group'' (all taxa in the clade defined by the node subtending all species in the morphogenus) by using Spearman rank correlation.…”

Section: Methodsmentioning

confidence: 99%

Congruence of morphologically-defined genera with molecular phylogenies

Jablonski

Finarelli

2009

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Morphologically-defined mammalian and molluscan genera (herein ''morphogenera'') are significantly more likely to be monophyletic relative to molecular phylogenies than random, under 3 different models of expected monophyly rates: Ϸ63% of 425 surveyed morphogenera are monophyletic and 19% are polyphyletic, although certain groups appear to be problematic (e.g., nonmarine, unionoid bivalves). Compiled nonmonophyly rates are probably extreme values, because molecular analyses have focused on ''problem'' taxa, and molecular topologies (treated herein as error-free) contain contradictory groupings across analyses for 10% of molluscan morphogenera and 37% of mammalian morphogenera. Both body size and geographic range, 2 key macroevolutionary and macroecological variables, show significant rank correlations between values for morphogenera and molecularlydefined clades, even when strictly monophyletic morphogenera are excluded from analyses. Thus, although morphogenera can be imperfect reflections of phylogeny, large-scale statistical treatments of diversity dynamics or macroevolutionary variables in time and space are unlikely to be misleading.biogeography ͉ body size ͉ macroecology ͉ macroevolution ͉ systematics M orphologically-defined genera are the primary analytical units for a wide range of large-scale paleontological and neontological analyses, across topics such as global diversity dynamics (1-8), macroevolutionary trends (9-11), paleoecology (12-14), systematics (15, 16), biogeography (17-19), and conservation biology (20-23). Although assigning rank to sets of species sharing close morphological affinities (usually with 1 or more diagnostic characters) lacks rigorous criteria, analyses of genus-level operational units are less subject to sampling and other biases than species-level analyses (24-26) and generally capture a damped record of species-level patterns (4, 27, 28). However, the proliferation of phylogenetic analyses using molecular data has uncovered an increasing number of paraphyletic or polyphyletic morphogenera (e.g., refs. 29 and 30), calling into question their analytic utility. Yet, despite alarming cases (e.g., ref. 31) and gross generalizations on the value of morphology (e.g., ref. 32), this issue has yet to be addressed quantitatively. Here, we evaluate the phylogenetic status of morphogenera relative to molecular phylogenies in 2 paleobiologically and ecologically important clades, Mammalia and Mollusca, and assess the potential impact of incorrect assumption of generic monophyly on 2 key macroevolutionary and macroecological variables: body size (9, 33-35) and latitudinal range (36-41). ResultsRates of Paraphyly and Polyphyly. We coded each of the 425 genera in our database (Table S1) as monophyletic, paraphyletic, or polyphyletic (42) (Fig. 1). The probability of randomly drawing a cladogram consistent with monophyly for a particular morphogenus from the set of all potential cladograms varies with the number of species in each analysis and in each morphogenus, but does not exceed 4.7% ...

show abstract

Quantifying Molluscan Body Size in Evolutionary and Ecological Analyses: Maximizing the Return on Data-Collection Efforts

Cited by 77 publications

References 37 publications

Taphonomic bias and time-averaging in tropical molluscan death assemblages: differential shell half-lives in Great Barrier Reef sediment

Taphonomic bias and time-averaging in tropical molluscan death assemblages: differential shell half-lives in Great Barrier Reef sediment

Shifting sources of productivity in the coastal marine tropics during the Cenozoic era

Congruence of morphologically-defined genera with molecular phylogenies

Contact Info

Product

Resources

About