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David Jablonski

Publications and source records attributed to David Jablonski.

11 recordsLinked to original sources
PubMed2006

Out of the tropics: evolutionary dynamics of the latitudinal diversity gradient.

The evolutionary dynamics underlying the latitudinal gradient in biodiversity have been controversial for over a century. Using a spatially explicit approach that incorporates not only origination and extinction but immigration, a global analysis of genera and subgenera of marine bivalves over the past 11 million years supports an "out of the tropics" model, in which taxa preferentially originate in the tropics and expand toward the poles without losing their tropical presence. The tropics are thus both a cradle and a museum of biodiversity, contrary to the conceptual dichotomy dominant since 1974; a tropical diversity crisis would thus have profound evolutionary effects at all latitudes.

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PubMed2006

Larval ecology, geographic range, and species survivorship in Cretaceous mollusks: organismic versus species-level explanations.

The observation that geographic range size in Cretaceous mollusks is correlated with species survivorship and is heritable at the species level has figured repeatedly in discussions of species selection over the past two decades. However, some authors have suggested that the relationship between mode of larval development and geographic range supports the reduction of this example to selection on organismic properties. Our reanalysis of Jablonski's work on heritability at the species level finds that geographic range is significantly heritable (using a randomization test) in both bivalves and gastropods, even within a single larval mode. Further, generalized linear models show that geographic range size is more important than larval mode in predicting extinction probability in both gastropods and bivalves. These results reaffirm the role and heritability of geographic range as a species-level property that can promote species selection; the model-based approach applied here may help to operationalize "screening off " and related approaches to evaluating hierarchical explanations in evolution.

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PubMed2006

Assessing the fidelity of the fossil record by using marine bivalves.

Taxa that fail to become incorporated into the fossil record can reveal much about the biases of this record and provide the information needed to correct such biases in empirical analyses of the history of life. Yet little is known about the characteristics of taxa missing from the fossil record. For the marine Bivalvia, which have become a model system for macroevolutionary and macroecological analysis in the fossil record, 308 of the 1,292 living genera and subgenera (herein termed "taxa") are not recorded as fossils. These missing taxa are not a random sample of the clade, but instead tend to have small body size, reactive shell structures, commensal or parasitic habit, deep-sea distribution, narrow geographic range, restriction to regions exposing few Neogene marine sediments, or recent date of formal taxonomic description in the neontological literature. Most missing taxa show two or more of these features and tend to be concentrated in particular families. When we exclude the smallest taxa (<1 cm) and deep-sea endemics, date of published description and geographic range become the strongest predictors of the missing taxa; other factors are statistically insignificant or have relatively small effects. These biases might influence a variety of analyses including the use of fossil data in support of phylogenetic analyses, molecular clock calibrations, and analyses of spatial and temporal dynamics of clades and biotas. Clade inventories such as these can be used to develop protocols that minimize the biases imposed by sampling and preservation.

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PubMed2005

Evolutionary innovations in the fossil record: the intersection of ecology, development, and macroevolution.

The origins of evolutionary innovations have been intensively studied, but relatively little is known about their large-scale ecological patterns. For post-Paleozoic benthic marine invertebrates, which have the richest and most densely sampled fossil record, order-level taxa tend to appear first in onshore, disturbed habitats, even in groups that are now exclusively deep-water (so that present-day distributions are not reliable indicators of original environments). New results presented here show that the onshore-origination pattern is robust to shifts in taxonomic methods and to new paleontological discoveries, and the few available studies suggest that this pattern can also be seen in terms of excursions in morphospace or the acquisition of derived character states, without reference to taxonomic categories. The environmental pattern at high levels contrasts significantly with the origin of low-level novelties (such as defined genera and families) in crinoids, echinoids, and bryozoans, where first appearances tend to conform to their clade-specific bathymetric diversity gradients. This discordance seems to eliminate potential driving mechanisms that simply scale up within-population genetic or ecological processes. Little is known about the factors that promote the onshore-offshore expansion of orders across the continental shelf, or that drive some clades to abandon ancestral habitats for an exclusively deep-water distribution. The origin of evolutionary innovation must ultimately reside in developmental changes, but the onshore-origination bias could emerge from two different dynamics: the pattern could be primarily genetic and developmental, i.e., innovations truly arise onshore; or primarily ecological, i.e., innovations arise randomly but preferentially survive onshore. Whatever the ultimate driving mechanisms, these macroevolutionary patterns show that theories of large-scale evolutionary novelty must include an ecological dimension.

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PubMed2005

Species-level heritability reaffirmed: a comment on "on the heritability of geographic range sizes".

For many current issues in macroevolution and macroecology, it is important to know to what degree the attributes of species are shared among closely related lineages, a concept sometimes referred to as species-level heritability. Recently, Webb and Gaston proposed a new method for analyzing the heritability of geographic range size and concluded that range size is not heritable in Cretaceous gastropods (data from Jablonski) and modern birds (their data). Here we show that Webb and Gaston's method is flawed in that it implicitly assumes that range sizes are uniformly distributed. When range size distributions show their characteristic strong right skew, Webb and Gaston's method spuriously tends to find that range sizes of closely related pairs of species are more dissimilar than the random expectation. A reanalysis of Jablonski's data finds range size to be robustly and strongly heritable in Cretaceous gastropods and less strongly but still significantly heritable in present-day birds.

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PubMed2005

Diversity, endemism, and age distributions in macroevolutionary sources and sinks.

Quantitative tests of historical hypotheses are necessary to advance our understanding of biogeographic patterns of species distributions, but direct tests are often hampered by incomplete fossil or historical records. Here we present an alternative approach in which we develop a dynamic model that allows us to test hypotheses about regional rates of taxon origination, extinction, and dispersal using information on ages and current distributions of taxa. With this model, we test two assumptions traditionally made in the context of identifying regions as "centers of origin"--that regions with high origination rates will have high diversity and high endemism. We find that these assumptions are not necessarily valid. We also develop expressions for the regional age distributions of extant taxa and show that these may yield better insight into regional evolutionary rates. We then apply our model to data on the biogeography and ages of extant genera of marine bivalves and conclude that diversity in polar regions predominantly reflects dispersal of taxa that evolved elsewhere rather than in situ origination-extinction dynamics.

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PubMed2003

The impact of the pull of the recent on the history of marine diversity.

Up to 50% of the increase in marine animal biodiversity through the Cenozoic at the genus level has been attributed to a sampling bias termed "the Pull of the Recent," the extension of stratigraphic ranges of fossil taxa by the relatively complete sampling of the Recent biota. However, 906 of 958 living genera and subgenera of bivalve mollusks having a fossil record occur in the Pliocene or Pleistocene. The Pull of the Recent thus accounts for only 5% of the Cenozoic increase in bivalve diversity, a major component of the marine record, suggesting that the diversity increase is likely to be a genuine biological pattern.

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PubMed2003

Geographical range and speciation in fossil and living molluscs.

The notion of a positive relation between geographical range and speciation rate or speciation probability may go back to Darwin, but a negative relation between these parameters is equally plausible. Here, we test these alternatives in fossil and living molluscan taxa. Late Cretaceous gastropod genera exhibit a strong negative relation between the geographical ranges of constituent species and speciation rate per species per million years; this result is robust to sampling biases against small-bodied taxa and is not attributable to phylogenetic effects. They also exhibit weak inverse or non-significant relations between geographical range and (i) the total number of species produced over the 18 million year timeframe, and (ii) the number of species in a single timeplane. Sister-group comparisons using extant molluscan species also show a non-significant relation between median geographical range and species richness of genera. These results support the view that the factors promoting broad geographical ranges also tend to damp speciation rates. They also demonstrate that a strong inverse relation between per-species speciation rate and geographical range need not be reflected in analyses conducted within a single timeplane, underscoring the inadequacy of treating net speciation as a proxy for raw per-taxon rates.

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PubMed2003

Morphological and developmental macroevolution: a paleontological perspective.

Evidence of the morphological evolution of metazoans has been preserved, in varying degrees of completeness, in the fossil record of the last 600 million years. Although extinction has been incessant at lower taxonomic levels, genomic comparisons among surviving members of higher taxa suggest that much of the developmental systems that pattern their bodyplans has been conserved from early in their history. Comparisons between the origin of morphological disparity in the record and patterns of genomic disparity among living taxa promise to be interesting. For example, Hox cluster composition varies among major taxa, and the fossil record suggests that many of the changes in Hox clusters may have been associated with late Neoproterozoic evolution among minute benthic vermiform clades, from which crown bilaterian phyla arose just before or during the Cambrian explosion. Study of genomic differences among crown classes and orders whosetiming and mode of origin can be inferred from morphological data inthefossil record should throw further light on the timing and mode of origin of genomic disparities.

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PubMed2002

Survival without recovery after mass extinctions.

Because many survivors of mass extinctions do not participate in postrecovery diversifications, and therefore fall into a pattern that can be termed "Dead Clade Walking" (DCW), the effects of mass extinctions extend beyond the losses observed during the event itself. Analyses at two taxonomic levels provide a first-order test of the prevalence of DCWs by using simple and very conservative operational criteria. For four of the Big Five mass extinctions of the Phanerozoic, the marine genera that survived the extinction suffered approximately 10-20% attrition in the immediately following geologic stage that was significantly greater than the losses sustained in preextinction stages. The stages immediately following the three Paleozoic mass extinctions also account for 17% of all order-level losses in marine invertebrates over that interval, which is, again, significantly greater than that seen for the other stratigraphic stages (no orders are lost immediately after the end-Triassic or end-Cretaceous mass extinctions). DCWs are not evenly distributed among four regional molluscan time-series following the end-Cretaceous extinction, demonstrating the importance of spatial patterns in recovery dynamics. Although biotic interactions have been invoked to explain the differential postextinction success of clades, such hypotheses must be tested against alternatives that include stochastic processes in low-diversity lineages-which is evidently not a general explanation for the ordinal DCW patterns, because postextinction fates are not related to the size of extinction bottlenecks in Paleozoic orders-and ongoing physical environmental changes.

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