... KRISTIN P. TEUSCH * ,1 , DOUGLAS S. JONES 2 and WARREN D. ALLMON 3 ... but most of these stud... more ... KRISTIN P. TEUSCH * ,1 , DOUGLAS S. JONES 2 and WARREN D. ALLMON 3 ... but most of these studies examined trends over relatively short time scales (230 years; Bohle-Carbonell, 1989; Carasco and Lozano, 1989; Escribano et al., 1997; Escribano and McLaren, 1999). ...
... all cases; see discussion below.) The second method is applicable to organisms whose dispersa... more ... all cases; see discussion below.) The second method is applicable to organisms whose dispersal ability is recognizable in fossils; species with apparently high dispersal abilities (eg, benthic marineinvertebrates with planktotrophic ... All Paleocene and Eocene coastal plain ...
Oxygen and carbon isotopic profiles across the shells of well-preserved bivalves and gastropods f... more Oxygen and carbon isotopic profiles across the shells of well-preserved bivalves and gastropods from the Pliocene Pinecrest Beds near Sarasota, Florida, provide detailed records of the paleoen-vironmental and paleoclimatic conditions under which these high-density shell beds accumulated, as well as offer insight into shell-growth rates and longevity. Eight turritellid gastropods were analyzed from within and surrounding two Turritella-rich beds, an upper bed within unit 2(2.5-2.0 Ma) and a lower bed situated near the top of the main shell bed, unit 6/7(3.5-2.5 Ma). Three bivalves plus another turritellid specimen from a lower horizon (middle of unit 6/7), considered to represent offshore, normal-marine conditions, were also analyzed. The isotopic profiles of all shells reflect year-round shell growth in a seasonal, subtropical to warm-temperate paleoenvironment. Cyclical patterns in δ18O reflect annual variations in water temperature which on average ranged from 15 to 24d̀C; minimum paleoseasonality contrasts varied from 7 to 9d̀C. Summer paleo-temperatures compare favorably with those detemined from ostracodes, whereas winter temperatures appear slightly cooler. Except for one pectinid specimen, temperature differences between horizons and specimens are small. Annual δ18O cycles indicate: Turritella apicalis lived longer and grew slightly faster than Turritella gladeensis; and, shell growth rates and increment formation in Mercenaria campechiensis are comparable to modern Florida populations. Coincident episodes of heavy δ18O and light δ18C in both turritellids and bivalves suggest a pattern of seasonal upwelling. This cool, nutrient-rich, upwelled water may be partially responsible for the great abundance of Pinecrest fossils. □Stable isotopes, Pliocene, Pinecrest Beds, Florida, upwelling, paleotemperature, mollusk, Turritella.
... 1989; Anderson 1996), however, reveals that a significant proportion of taxa are represented ... more ... 1989; Anderson 1996), however, reveals that a significant proportion of taxa are represented by previous collections made by Harold and Emily Vokes of ... DC Jones, MA Kosnik, S. Lidgard, S. Low, AI Miller, PM Novack-Gottshall, TD Olszewski, ME Patzkowsky, DM Raup, K. Roy ...
Three working concepts or definitions of the genus as a systematic category are available: the “p... more Three working concepts or definitions of the genus as a systematic category are available: the “phylogenetic”; or “cladistic”; concept, which views genera as monophyletic clades, the “phenetic”; or “gap”; concept, which views genera as clustered in morphological space, separated from other such groups by many differences, and the “hybridization”; concept, which holds that species in different genera can never hybridize. The hybridization concept is inapplicable to paleontological situations, leaving a choice between phenetic and phylogenetic concepts. This choice is important to both practicing paleontological taxonomists and to compilers of their work. All else being equal, evolutionary behavior of phenetically defined genera will not mirror that of species as well as phylogenetically defined genera; phenetically defined genera may have more biological reality and reveal more about the relationship between morphological change and speciation.
... Cormo-rants from Pleistocene deposits in Florida are ei-ther too fragmentary for specific ide... more ... Cormo-rants from Pleistocene deposits in Florida are ei-ther too fragmentary for specific identification or represent the living Double-Crested Cormorant (P. auritus) or the Neotropical Cormorant (P. brasilia-nus) (Emslie 1995a, 1995b). ...
ABSTRACT In This Issue... Darwin's Earthworms page 12 Tracing Darwin's Steps in P... more ABSTRACT In This Issue... Darwin's Earthworms page 12 Tracing Darwin's Steps in Patagonia page 16 Darwin & Paleontology page 22 Teaching Evolution in America page 43 ... and More !
Paleoecological studies requiring taxonomic information beyond presence/absence data (i.e. relati... more Paleoecological studies requiring taxonomic information beyond presence/absence data (i.e. relative abundance) must demonstrate that the sampling regime employed to collect such data adequately fits the faunas under investigation. A study of dense shell beds of the Middle Eocene Gosport Sand of Alabama indicates that, for localities with high abundance and diversity and little internal structure, diversity-abundance data derived from standard-sized samples vary significantly and cannot be used to develop consistent species-level distributional patterns. Based on this result and the additional observation that different species show different patterns of occurrence, we propose an operational approach for determining what sample size will yield reliable distributional data for different proportions of the fauna. In the Gospon, samples of 3–5***1 yield reliable data on the approximately 25% of the species that are most common and abundant; samples of 35–40 I would be necessary to yield similarly reliable data on the next 15-10% the remainder of species are too rare ever to be realistically examined quantitatively in bulk samples. □Sampling, paleoecology, taphonomy, Mollusks, Gosport Sand, Eocene.
A traditional focus of evolutionary paleoecology has been the reconstruction of the selective for... more A traditional focus of evolutionary paleoecology has been the reconstruction of the selective forces that have affected evolving lineages through time. If the history of those lineages is dominated by stasis and punctuation, however, this is at best an inadequate and at worst a misdirected research strategy for macroevolution, because long-term stasis implies that environmental factors may have less influence on evolving lineages than previously believed. Such reasoning has led some proponents of punctuated views to reject ecological interactions as predominant or even significant forces in evolution. This is not a necessary conclusion. It is possible to accept the empirical predominance of stasis in evolution and at the same time the importance of ecology in affecting the course of evolutionary trends within lineages. If stasis prevails, ecology matters in the evolution of lineages if either (1) stabilizing selection is an important cause of stasis or (2) ecological interactions play an important role in controlling the speciation process. Viewing allopatric speciation explicitly as a three-stage process (consisting of formation, persistence and differentiation of isolated populations) clarifies testing of the role of ecology in speciation and may redirect clade-specific evolutionary paleoecology towards more enlightening interaction with other areas of macroevolutionary study.
... KRISTIN P. TEUSCH * ,1 , DOUGLAS S. JONES 2 and WARREN D. ALLMON 3 ... but most of these stud... more ... KRISTIN P. TEUSCH * ,1 , DOUGLAS S. JONES 2 and WARREN D. ALLMON 3 ... but most of these studies examined trends over relatively short time scales (230 years; Bohle-Carbonell, 1989; Carasco and Lozano, 1989; Escribano et al., 1997; Escribano and McLaren, 1999). ...
... all cases; see discussion below.) The second method is applicable to organisms whose dispersa... more ... all cases; see discussion below.) The second method is applicable to organisms whose dispersal ability is recognizable in fossils; species with apparently high dispersal abilities (eg, benthic marineinvertebrates with planktotrophic ... All Paleocene and Eocene coastal plain ...
Oxygen and carbon isotopic profiles across the shells of well-preserved bivalves and gastropods f... more Oxygen and carbon isotopic profiles across the shells of well-preserved bivalves and gastropods from the Pliocene Pinecrest Beds near Sarasota, Florida, provide detailed records of the paleoen-vironmental and paleoclimatic conditions under which these high-density shell beds accumulated, as well as offer insight into shell-growth rates and longevity. Eight turritellid gastropods were analyzed from within and surrounding two Turritella-rich beds, an upper bed within unit 2(2.5-2.0 Ma) and a lower bed situated near the top of the main shell bed, unit 6/7(3.5-2.5 Ma). Three bivalves plus another turritellid specimen from a lower horizon (middle of unit 6/7), considered to represent offshore, normal-marine conditions, were also analyzed. The isotopic profiles of all shells reflect year-round shell growth in a seasonal, subtropical to warm-temperate paleoenvironment. Cyclical patterns in δ18O reflect annual variations in water temperature which on average ranged from 15 to 24d̀C; minimum paleoseasonality contrasts varied from 7 to 9d̀C. Summer paleo-temperatures compare favorably with those detemined from ostracodes, whereas winter temperatures appear slightly cooler. Except for one pectinid specimen, temperature differences between horizons and specimens are small. Annual δ18O cycles indicate: Turritella apicalis lived longer and grew slightly faster than Turritella gladeensis; and, shell growth rates and increment formation in Mercenaria campechiensis are comparable to modern Florida populations. Coincident episodes of heavy δ18O and light δ18C in both turritellids and bivalves suggest a pattern of seasonal upwelling. This cool, nutrient-rich, upwelled water may be partially responsible for the great abundance of Pinecrest fossils. □Stable isotopes, Pliocene, Pinecrest Beds, Florida, upwelling, paleotemperature, mollusk, Turritella.
... 1989; Anderson 1996), however, reveals that a significant proportion of taxa are represented ... more ... 1989; Anderson 1996), however, reveals that a significant proportion of taxa are represented by previous collections made by Harold and Emily Vokes of ... DC Jones, MA Kosnik, S. Lidgard, S. Low, AI Miller, PM Novack-Gottshall, TD Olszewski, ME Patzkowsky, DM Raup, K. Roy ...
Three working concepts or definitions of the genus as a systematic category are available: the “p... more Three working concepts or definitions of the genus as a systematic category are available: the “phylogenetic”; or “cladistic”; concept, which views genera as monophyletic clades, the “phenetic”; or “gap”; concept, which views genera as clustered in morphological space, separated from other such groups by many differences, and the “hybridization”; concept, which holds that species in different genera can never hybridize. The hybridization concept is inapplicable to paleontological situations, leaving a choice between phenetic and phylogenetic concepts. This choice is important to both practicing paleontological taxonomists and to compilers of their work. All else being equal, evolutionary behavior of phenetically defined genera will not mirror that of species as well as phylogenetically defined genera; phenetically defined genera may have more biological reality and reveal more about the relationship between morphological change and speciation.
... Cormo-rants from Pleistocene deposits in Florida are ei-ther too fragmentary for specific ide... more ... Cormo-rants from Pleistocene deposits in Florida are ei-ther too fragmentary for specific identification or represent the living Double-Crested Cormorant (P. auritus) or the Neotropical Cormorant (P. brasilia-nus) (Emslie 1995a, 1995b). ...
ABSTRACT In This Issue... Darwin's Earthworms page 12 Tracing Darwin's Steps in P... more ABSTRACT In This Issue... Darwin's Earthworms page 12 Tracing Darwin's Steps in Patagonia page 16 Darwin & Paleontology page 22 Teaching Evolution in America page 43 ... and More !
Paleoecological studies requiring taxonomic information beyond presence/absence data (i.e. relati... more Paleoecological studies requiring taxonomic information beyond presence/absence data (i.e. relative abundance) must demonstrate that the sampling regime employed to collect such data adequately fits the faunas under investigation. A study of dense shell beds of the Middle Eocene Gosport Sand of Alabama indicates that, for localities with high abundance and diversity and little internal structure, diversity-abundance data derived from standard-sized samples vary significantly and cannot be used to develop consistent species-level distributional patterns. Based on this result and the additional observation that different species show different patterns of occurrence, we propose an operational approach for determining what sample size will yield reliable distributional data for different proportions of the fauna. In the Gospon, samples of 3–5***1 yield reliable data on the approximately 25% of the species that are most common and abundant; samples of 35–40 I would be necessary to yield similarly reliable data on the next 15-10% the remainder of species are too rare ever to be realistically examined quantitatively in bulk samples. □Sampling, paleoecology, taphonomy, Mollusks, Gosport Sand, Eocene.
A traditional focus of evolutionary paleoecology has been the reconstruction of the selective for... more A traditional focus of evolutionary paleoecology has been the reconstruction of the selective forces that have affected evolving lineages through time. If the history of those lineages is dominated by stasis and punctuation, however, this is at best an inadequate and at worst a misdirected research strategy for macroevolution, because long-term stasis implies that environmental factors may have less influence on evolving lineages than previously believed. Such reasoning has led some proponents of punctuated views to reject ecological interactions as predominant or even significant forces in evolution. This is not a necessary conclusion. It is possible to accept the empirical predominance of stasis in evolution and at the same time the importance of ecology in affecting the course of evolutionary trends within lineages. If stasis prevails, ecology matters in the evolution of lineages if either (1) stabilizing selection is an important cause of stasis or (2) ecological interactions play an important role in controlling the speciation process. Viewing allopatric speciation explicitly as a three-stage process (consisting of formation, persistence and differentiation of isolated populations) clarifies testing of the role of ecology in speciation and may redirect clade-specific evolutionary paleoecology towards more enlightening interaction with other areas of macroevolutionary study.
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