Differentiation in a greenhouse world 2
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Differentiation in a greenhouse world 2
1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2arctic Survey. High Cross. Madingley Road. Cambridge CB3 OET. UK5:BioGeoD. Edinburgh. EH16 6DR. UK. E mail: biogeod@gmail.com6;Department of Earth Sciences. University College London. Gower street. WC1E 6BT. UK. E mail: 7mark,bell521 (agmail.com89Keywords: faunal differentiation, greenhouse world. N Differentiation in a greenhouse world 2eogastropoda, dominance in polar faunas, lOtrophic generalists, seasonality in primary productivity, relative diversity distributions, rank 11 abundanDifferentiation in a greenhouse world 2
ce models1213Short running title: Early Cenozoic faunal differentiation14'Correspondence: J. Alistair Crame. British Antarctic Survey. High Cross. Mad1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2 in-paper Appendix)18Number of references: 6919Number of figures: 511220ABSTRACT21 Aim To investigate those factors that influenced the differentiation of high-latitude and polar marine 22faunas on both ecological and evolutionary timescales. Can a focus on a greenhouse world provide 23some importan Differentiation in a greenhouse world 2t clues?24Location World-wide, but with particular emphasis on the evolution of Antarctic marine faunas.25Time period Early Cenozoic era and present dDifferentiation in a greenhouse world 2
ay.26Major taxa studied Mollusca, especially Neogastropoda.27Methods The Early Cenozoic global radiation of one of the largest extant marine clades.281Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2 was assessed using Sorensen’s dissimilarity 30index. and component species in each of the three faunas were assigned to 29 families and family 31groups. Relative diversity distributions were fitted to these three faunas as well as two modern ones 32to assess the contrast in evenness between high- a Differentiation in a greenhouse world 2nd low-latitude assemblages.33Results By the Middle Eocene a distinct high-latitude neogastropod fauna had evolved in Antarctica. 34ln addition, the dDifferentiation in a greenhouse world 2
istribution of species within families in this fauna is statistically significantly less 35even than that in the tropics. Indeed, there is no detectab1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2ed by a small number of trophic generalist groups.38Main Conclusion As the hyperdiverse Neogastropoda clade radiated globally through the Early 39Cenozoic it differentiated into distinct high- and low-latitude components. The fact that it did so in a 40greenhouse world strongly suggests that somethi Differentiation in a greenhouse world 2ng else besides temperature was involved in this 41 process. The predominance of generalist feeding types in the Antarctic fossil faunas is linked toDifferentiation in a greenhouse world 2
the32442phenomenon of a seasonally pulsed food supply, just as it is today. Seasonality in primary 43productivity may act as a fundamental control on 1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2ecame firmly 46established at approximately the Eocene - Oligocene (E - 0) boundary, some 34 Myr ago (Thomas & 47Gooday. 1996: Hawkins et al.. 2006: Mittelbach et al.. 2007: Archibald et al.. 2010). At this time we 48know that there was either a marked dip in global mean annual temperatures, increas Differentiation in a greenhouse world 2e in the 49volume of the East Antarctic ice sheet, or. very probably, a combination of the two (Eldrett et al., 502009; Petersen & Schrag, 2015). TheDifferentiation in a greenhouse world 2
equatorial - polar temperature gradients almost certainly 51steepened considerably at this time and this in turn intensified the essentially latitude-1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2ess, as our investigations into the biogeography and palaeobiogeography of the high-55latitude and polar regions continue it is becoming apparent that, at least in the marine realm. 56distinctive polar assemblages with strikingly modern affinities can be detected over 20 Myr prior to 57the E - o bou Differentiation in a greenhouse world 2ndary in the fossil record of the Early - Middle Eocene epochs. This is particularly so in 58Antarctica where intensive investigation of the prolificDifferentiation in a greenhouse world 2
La Meseta Formation of Seymour Island. 59Antarctic Peninsula (c. 65°s palaeolatitude) has revealed that approximately 32% of the Middle 60Eocene mollu1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2 of the principal taxonomic groups 62within this fauna, the Neogastropoda, has revealed that, not only are 37% of the species present 63assignable to modern genera, but the vast majority of these belong to a single family. Buccinidae. s.l. 64(Beu, 2009: Crame et al., 2014). In this respect the overa Differentiation in a greenhouse world 2ll taxonomic structure of the Middle Eocene 65neogastropod fauna is very similar to that of the extant fauna. A recent investigation established 66thaDifferentiation in a greenhouse world 2
t, whereas both the Arctic and Antarctic modern neogastropod faunas were characterised by536https://khothuvien.cori!67patterns of high dominance/low e1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British Anta Differentiation in a greenhouse world 2 present in a 69number of other widespread taxonomic groups at the present day (Brown, 2014; see also, below).1Differentiation of high-latitude and polar marine faunas in a greenhouse world2J. Alistair Crame1. Alistair J. McGowan2, Mark A. Bell3 3^British AntaGọi ngay
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