Benthic origins of zooplankton: An environmentally determined macroevolutionary effect

Rigby, S. V.; Milsom, Clare

doi:10.1130/0091-7613(1996)024<0052:boozae>2.3.co;2

Cited by 33 publications

(35 citation statements)

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“…This cryptic precambrian history suggests that these stem-group bilaterians must have been ''micrometazoans,'' because, although benthic (38,39), they were seemingly incapable of leaving trace fossils (see also ref. 40).…”

Section: Tempo and Mode Of Early Animal Evolutionmentioning

confidence: 99%

Estimating metazoan divergence times with a molecular clock

Peterson

Lyons

Nowak

et al. 2004

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

427

285

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Accurately dating when the first bilaterally symmetrical animals arose is crucial to our understanding of early animal evolution. The earliest unequivocally bilaterian fossils are Ϸ555 million years old. In contrast, molecular-clock analyses calibrated by using the fossil record of vertebrates estimate that vertebrates split from dipterans (Drosophila) Ϸ900 million years ago (Ma). Nonetheless, comparative genomic analyses suggest that a significant rate difference exists between vertebrates and dipterans, because the percentage difference between the genomes of mosquito and fly is greater than between fish and mouse, even though the vertebrate divergence is almost twice that of the dipteran. Here we show that the dipteran rate of molecular evolution is similar to other invertebrate taxa (echinoderms and bivalve molluscs) but not to vertebrates, which significantly decreased their rate of molecular evolution with respect to invertebrates. Using a data set consisting of the concatenation of seven different amino acid sequences from 23 ingroup taxa (giving a total of 11 different invertebrate calibration points scattered throughout the bilaterian tree and across the Phanerozoic), we estimate that the last common ancestor of bilaterians arose somewhere between 573 and 656 Ma, depending on the value assigned to the parameter scaling molecular substitution rate heterogeneity. These results are in accord with the known fossil record and support the view that the Cambrian explosion reflects, in part, the diversification of bilaterian phyla.A lthough the Cambrian explosion is of singular importance to our understanding of the history of life, it continues to defy explanation (1). This defiance stems, in part, from our inability to distinguish between two competing hypotheses: whether the Cambrian explosion reflects the rapid appearance of fossils with animals having a deep but cryptic precambrian history, or whether it reflects the true sudden appearance and diversification of animals in the Cambrian (2). Because each hypothesis makes a specific prediction of when animals arose in time, one way to distinguish between these two hypotheses is to date animal diversifications by using a molecular clock (2). A number of previous clock studies (reviewed in refs. 3 and 4) have suggested that the last common ancestor of bilaterians (LCB) lived well over one billion years ago (5, 6), whereas others suggest that LCB arose Ϸ900 million years ago (Ma) (e.g., refs. 7-10), and still others are more consistent with an origination closer to the Cambrian (11-13). These deep estimates for the origin of LCB raise the question of how hundreds of millions of years of bilaterian evolution can escape detection, given that LCB and its near relatives should have had the capability of leaving both body and trace fossils (14-16).Because molecular clocks have several inherent problems, including how the clock is calibrated, how molecular substitution rates are estimated, and how heterogeneity in these rates is detected and corrected (3, 4), as well...

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Section: Tempo and Mode Of Early Animal Evolutionmentioning

confidence: 99%

Estimating metazoan divergence times with a molecular clock

Peterson

Lyons

Nowak

et al. 2004

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

427

285

View full text Add to dashboard Cite

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“…The build-up process of the pelagic ecosystem, crucial to the functioning of the biosphere, raises the fundamental question of when and how animals started to colonize off-bottom niches (Rigby & Milsom 1996). Most exceptional Cambrian biotas (e.g.…”

Section: Introductionmentioning

confidence: 99%

Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas

Vannier

García‐Bellido²,

Hu³

et al. 2009

Proc. R. Soc. B.

102

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Exceptional fossil specimens with preserved soft parts from the Maotianshan Shale (ca 520 Myr ago) and the Burgess Shale (505 Myr ago) biotas indicate that the worldwide distributed bivalved arthropod Isoxys was probably a non-benthic visual predator. New lines of evidence come from the functional morphology of its powerful prehensile frontal appendages that, combined with large spherical eyes, are thought to have played a key role in the recognition and capture of swimming or epibenthic prey. The swimming and steering of this arthropod was achieved by the beating of multiple setose exopods and a flap-like telson. The appendage morphology of Isoxys indicates possible phylogenetical relationships with the megacheirans, a widespread group of assumed predator arthropods characterized by a pre-oral 'great appendage'. Evidence from functional morphology and taphonomy suggests that Isoxys was able to migrate through the water column and was possibly exploiting hyperbenthic niches for food. Although certainly not unique, the case of Isoxys supports the idea that off-bottom animal interactions such as predation, associated with complex feeding strategies and behaviours (e.g. vertical migration and hunting) were established by the Early Cambrian. It also suggests that a prototype of a pelagic food chain had already started to build-up at least in the lower levels of the water column.

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“…In strong contrast to these earlier described forms, tychopelagics are able to not only survive but also grow and calcify in the plankton, and thus must be able to maintain buoyancy. Interestingly, buoyancy is generally assumed to be one of the major constraining evolutionary traits on the passage from benthos to plankton (14). Species of the genus Bolivina might be more buoyant than other benthic taxa: They have been observed in plankton nets over and just off the shelf more commonly than species of other genera (23).…”

Section: Resultsmentioning

confidence: 99%

“…Traditionally, all planktic foraminifera have been seen as monophyletic [Suborder Globigerinina (12)], descended from a single Early-Middle Jurassic ancestor (13), similar to the monophyletic origins of other planktic groups (14). It has, however, not been possible to derive a satisfactory cladogram on fossil data, and the current foraminiferal molecular phylogeny has limited resolution for the prediction of deep-time ancestral relationships.…”

mentioning

confidence: 99%

Surviving mass extinction by bridging the benthic/planktic divide

Darling

Thomas

Kasemann

et al. 2009

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

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Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early-Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms. The few survivor species radiated to form diverse assemblages once again in the Cenozoic. There have, however, long been doubts regarding the monophyletic origin of planktic foraminifera. We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains. Such a lifestyle (tychopelagic) had not been recognized as adapted by foraminifera. Tychopelagic are endowed with great ecological advantage, enabling rapid recolonization of the extinction-susceptible pelagic domain from the benthos. We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny.end-Cretaceous ͉ foraminifera ͉ Mg/Ca ͉ plankton evolution ͉ SSU rRNA

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Benthic origins of zooplankton: An environmentally determined macroevolutionary effect

Cited by 33 publications

References 0 publications

Estimating metazoan divergence times with a molecular clock

Estimating metazoan divergence times with a molecular clock

Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas

Surviving mass extinction by bridging the benthic/planktic divide

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