We present a new three-dimensional theoretical ecospace for the ecological classification of marine animals based on vertical tiering, motility level, and feeding mechanism. In this context, analyses of a database of level-bottom fossil assemblages with abundance counts demonstrate fundamental changes in marine animal ecosystems between the mid-Paleozoic (461–359 Ma) and late Cenozoic (23–0.01 Ma). The average local relative abundance of infaunal burrowers, facultatively motile animals, and predators increased, whereas surface dwellers and completely non-motile animals decreased in abundance. Considering tiering, motility, and feeding together, more modes of life had high to moderate average relative abundance in the Cenozoic than in the Paleozoic. These results are robust to the biasing effects of aragonite dissolution in Paleozoic sediments and to heterogeneities in the latitudinal and environmental distributions of collections. Theoretical ecospace provides a unified system for future analyses of the utilization of ecologic opportunities by marine metazoa.

Many fossil assemblages are time-averaged, with multiple generations of organisms mixed into a single stratigraphic horizon. A time-averaged sample of a taxon should be more variable than a single-generation sample if enough morphologic change occurred during the interval of time-averaging. Time-averaging may also alter correlations between morphologic variables and obscure allometric relationships in an evolving population. To investigate these issues, we estimated the variability of six modern, single-generation samples of the bivalve Mercenaria campechiensis using Procrustes analysis and compared them with several time-averaged Pleistocene samples of M. campechiensis and M. permagna. Both the modern and the fossil samples ranged in variability, but these ranges were virtually identical. Morphology was quite stable over the hundreds to many thousands of years that passed as the assemblages accumulated, and the variabilities of the fossil samples could be used to estimate single-generation variability. At one fossil locality, the environment and paleocommunity changed partway through the collection interval; the morphology of Mercenaria appears stable above and below the transition but changes across it. This change is similar in magnitude to the differences between geographically separated modern populations, whereas temporal variation within single environmental settings is distinctly less than geographic variation. Analytical time-averaging (the mixing of fossils from different horizons) between paleocommunities increased variability slightly (but not significantly) above that found in living populations. While its constituent populations appear stable on millennial timescales, M. campechiensis has been evolutionarily static since at least the early to middle Pleistocene.

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Additional Supporting Information may be found online in the supporting information tab for this article. L E T T E R S T O T H E E D I T O R GSTP1 does not modify MC1R effects on melanoma risk 1 | BACKGROUNDGlutathione S-transferases (GSTs) are a group of enzymes that act to detoxify reactive oxygen species resulting from oxidative stress processes and melanin production. GSTP1 is a polymorphic gene encoding variant proteins involved in metabolism. The role of the rs1695*A/G GSTP1 Ile105Val polymorphism in cutaneous malignant melanoma (CMM) susceptibility remains controversial. Two recent meta-analyses reported that the GSTP1 105Val allele was associated with an increased risk of CMM.1,2 However, it was concluded by the authors of both publications that additional studies with larger cohorts were required.The melanocortin 1 receptor (MC1R) gene encodes a G-protein coupled receptor involved in the regulation of melanin production and the response to solar ultraviolet. 3 MC1R RHC-variant alleles exercise major influence on hair colour, skin colour and sun sensitivity. The association between MC1R and susceptibility to CMM and skin cancer in general has been described previously. 4,5 A 2011 Spanish study reported that the GSTP1 polymorphism was associated with light coloured hair and increased CMM risk. Furthermore, the authors described a greater penetrance of CMM risk when the GSTP1 105Val allele was combined with MC1R RHC-variant alleles.6,7 | QUESTIONS ADDRESSEDThis study has further examined the association between rs1695*A/G GSTP1 Ile105Val polymorphism and CMM. In addition, we examined the previously described effect modification of the combination of GSTP1 Ile105Val with MC1R RHC-variant alleles in a cohort of Queensland control and CMM cases and CMM control and patient samples from Germany. This study included the largest population to date, a total of 27 574 participants. Six GSTP1 polymorphisms were examined to assess for a potential effect on CMM risk (Table 1). GSTP1 rs4891 was in strong linkage disequilibrium with rs1695 (r 2 =0.92, Table S1). Although previous studies have suggested the involvement of rs1695 in CMM risk (also apparent when stratified by study, MC1R variant genotypes designated using WT, r and R allele classification and risk of CMM (Table 2). These effects were not modified by GSTP1 rs1695 genotype (A/A, A/G, G/G) in the stratified analysis (overall P=0.79). This result was also confirmed when restricted to MC1R Arg151Cys genotype (WT/WT, WT/R, R/R), the MC1R allele of highest penetrance for CMM and red hair colour (Table S3). Moreover, examination of each MC1R allele individually did not show any interaction with GSTP1 rs1695 genotype and CMM risk (Table S4). | EXPERIMENTAL DESIGN & RESULTSThe reported association of rs1695 and light hair colour 6 was not seen in our analysis. However, the rs1138272 GSTP1 Ala114ValSNP showed weak association with darker hair colour in the BTNS | LETTERS TO THE EDITOR | CONCLUSIONSThe role of GSTP1 polymorphism in CMM has been examined in sev...