Speciation patterns and trends in the fossil record

Hallam, A.

doi:10.1016/s0016-6995(97)80216-1

Cited by 26 publications

(20 citation statements)

References 35 publications

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“…The bivalves, ammonites and brachiopods across the T-J boundary accord with this pattern (see the data presented earlier). As already noted, those taxa that went extinct include representatives that grew to large size, whereas all the early Hettangian taxa are small (Hallam 1998).…”

Section: Relationship Of Biotic To Environmental Changementioning

confidence: 69%

How catastrophic was the end‐Triassic mass extinction?

Hallam

2002

LET

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A review of marine and terrestrial animal and plant fossils fails to reveal convincing evidence of a global catastrophe at the Triassic-Jurassic boundary, although this time marked the nal disappearance of ceratite ammonites and conodonts, together with the extinction of most calcareous demosponges; important groups of bivalves and brachiopods went extinct. Because of facies problems, however, there is no stratigraphic section that reveals a clear-cut disappearance over a short distance. Other marine animal groups except perhaps the radiolarians fail to reveal a notable extinction of global extent immediately across the boundary. On the other hand, there was a substantially higher extinction rate among marine animals in the Rhaetian as compared with the previous stage. On the land, the record is equivocal. Dramatic changes across the T-J boundary have been claimed for plants in particular areas, such as eastern North America and East Greenland, but only gradual change has been recognized elsewhere. Similarly, claims of a T-J boundary vertebrate mass extinction have not been supported by others. For the Rhaetian as a whole, however, the turnover rate of reptiles was high. Although much remains to be learned, it seems evident that the fossil record of the latest Triassic is more consistent with a gradual scenario extended over time than a 'geologically instantaneous' impact catastrophe. & Catastrophe, mass extinction, TriassicJurassic boundary A. Hallam (A.Hallam@bham.ac.uk),

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Section: Relationship Of Biotic To Environmental Changementioning

confidence: 69%

How catastrophic was the end‐Triassic mass extinction?

Hallam

2002

LET

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“…Johnson (1984Johnson ( , 1985 also decided that punctuation was the dominant mode in Jurassic scallops. Hallam (1982Hallam ( , 1998 invoked heterochrony for Liassic Gryphaea, with the recognition of a paedomorphocline, but there has been some dispute between him and Johnson (1993Johnson ( , 1994 about the degree to which the change between three successive species was punctuational or gradualistic.…”

Section: Mode Of Speciationmentioning

confidence: 99%

Ecology and evolution of Jurassic trigoniid bivalves in Europe

Francis

Hallam

2003

LET

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A modern palaeobiological approach to the taxonomy, making full allowance for a wide range of variation, has allowed the distinction of 22 Jurassic trigoniid species in Europe, grouped into 7 genera. Most species were con®ned to shallow marine habitats ranging up to a few tens of metres in depth but were adapted to low energy environments as well as environments of moderate to high energy. The presence of external ornament on the shell¯anks was probably an adaptation to facilitate burrowing, but in the absence of useful external ornament other adaptations to increase burrowing ef®ciency may have been realized by the development of an elongate shape. Because their occurrence in Jurassic strata is only intermittent, con®dent inferences on evolutionary patterns are limited to the two commonest genera, Trigonia and Myophorella. Phyletic size increase has been recognized in the latter but not the former genus. The calculated species longevities correspond fairly closely with those established for Jurassic bivalve species in general. The mode of speciation is dominantly punctuational, but only one likely example of species splitting is recognized.

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“…5,14,15). Addressing this question is challenging due to insufficient fossil data for most taxa and the difficulties in relating morphological change to genetic divergence and the evolution of reproductive isolation (16). Fossil data can only be used to distinguish anagenesis from cladogenesis, at the assemblage level, to the extent that four general assumptions are upheld (5): (i) morphologically distinct taxa (hereafter morphospecies) that coexist temporally are reproductively isolated, and therefore independently evolving; (ii) ancestor-descendant relationships among morphospecies are inferred accurately; (iii) the vast majority of morphospecies have been identified; and (iv) the temporal range of each morphospecies, as defined by its first appearance datum (FAD) and last appearance datum (LAD), is estimated with known precision.…”

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confidence: 99%

Assessing the role of cladogenesis in macroevolution by integrating fossil and molecular evidence

Strotz

Allen

2013

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

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Assessing the extent to which population subdivision during cladogenesis is necessary for long-term phenotypic evolution is of fundamental importance in a broad range of biological disciplines. Differentiating cladogenesis from anagenesis, defined as evolution within a species, has generally been hampered by dating precision, insufficient fossil data, and difficulties in establishing a direct link between morphological changes detectable in the fossil record and biological species. Here we quantify the relative frequencies of cladogenesis and anagenesis for macroperforate planktic Foraminifera, which arguably have the most complete fossil record currently available, to address this question. Analyzing this record in light of molecular evidence, while taking into account the precision of fossil dating techniques, we estimate that the fraction of speciation events attributable to anagenesis is <19% during the Cenozoic era (last 65 Myr) and <10% during the Neogene period (last 23 Myr). Our central conclusion-that cladogenesis is the predominant mode by which new planktic Foraminifera taxa become established at macroevolutionary time scales-differs markedly from the conclusion reached in a recent study based solely on fossil data. These disparate findings demonstrate that interpretations of macroevolutionary dynamics in the fossil record can be fundamentally altered in light of genetic evidence. anagenesis, which occurs within a species, and cladogenesis, which occurs during speciation and results in the subdivision of a species into two reproductively isolated, independently evolving taxa (1, 2). Distinguishing between these modes is essential to determining the role of population subdivision in evolutionary dynamics (3,4). This topic has received considerable attention in paleontology (1, 2), perhaps because the fossil record provides the only direct record of long-term morphological change (5), but its importance extends to other biological disciplines. For example, in population genetics, models only predict that phenotypic change is contingent upon or associated with the evolution of reproductive isolation under specific circumstances (3). Thus, a primary role for cladogenesis may highlight the importance of particular speciation modes (2), metapopulations dynamics (6), or adaptive peaks in fitness landscapes (7,8). In community ecology, both evolutionary modes may influence biodiversity, but the mechanisms differ: only cladogenesis results in an increase in diversity (9-11), but anagenesis may help maintain diversity if it results in niche differences that facilitate species coexistence (12, 13).Remarkably few studies have attempted to quantify the relative frequencies of anagenesis and cladogenesis for entire species assemblages (e.g., refs. 5, 14, 15). Addressing this question is challenging due to insufficient fossil data for most taxa and the difficulties in relating morphological change to genetic divergence and the evolution of reproductive isolation (16). Fossil data can only be used to distinguish anag...

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Speciation patterns and trends in the fossil record

Cited by 26 publications

References 35 publications

How catastrophic was the end‐Triassic mass extinction?

How catastrophic was the end‐Triassic mass extinction?

Ecology and evolution of Jurassic trigoniid bivalves in Europe

Assessing the role of cladogenesis in macroevolution by integrating fossil and molecular evidence

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