Long-period astronomical forcing of mammal turnover

Abstract

Mammals are among the fastest-radiating groups, being charac terized by a mean species lifespan of the order of 2.5 million years Changes in organisms occur on a variety of temporal scales. Four basic temporal scales (tiers) have been recognized: the ecological timescale; the Milankovitch timescale of precession (the wobbling of the Earth's axis, �21 kyr periodicity), obliquity (tilt of the Earth's axis, 41 kyr periodicity) and eccentricity (the orbit around the Sun, � 100 and �400 kyr periodicity); the million-year timescale of species extinctions and originations; and the ultra-long timescale of mass extinctions and major taxonomic replacements9. Although the main processes controlling the fi rst tier (climate change and competition), the second tier (climate-forced distributional vari ation)3,9,IO and the fourth tier (catastrophic perturbations of the Earth's biosphere) are reasonably well defi ned, the mechanisms underlying third-tier processes are not well ill1derstood. Mammals have featured importantly in discussions on the processes pertaining to this tier2-7• Because their mean species duration is estimated at 2.3-2.6 Myr (refs 1, 2), primary (20-400kyr) Milankovitch vari ations cannot be held responsible for mammal speciation and extinction4,9,lo. It has been suggested that amplitude changes of climatic oscillations could have played a part in explaining turn over3,1O, but until now no efforts have been made systematically to compare such amplitude variations with turnover in long and well dated records.We compiled a data set of more than 200 rodent assemblages from Central Spain (see Supplementary Notes and Supplementary Ta ble 1) and analysed it in terms of turnover. The record is exceptionally long (22 Myr) , largely continuous, dense and well dated. We focused on rodents, because screen sieving allows the collection of large amounts of easily identifi able dental elements. The studied fossils originate from fl uvio-Iacustrine sections in the Madrid, Calatayud-Daroca and Te ruel basins, and amount to over 80,000 isolated molars, which were identifi ed at the species and lineage level (132 lineages, pseudo extinctions ignored). All studied localities are positioned in strati graphic sections, a large number of which have been tied to the geomagnetic polarity timescale by first-order correlations. The complete temporal sequence was calibrated to the new astronomi cally tuned timescale for the Neogene11 (Supplementary Fig. 1). The use of this new timescale is of crucial importance because it allows a direct comparison -with time series of the Earth's orbital parameters outlined above.Randomization procedures were used to capture uncertainties in the ages oflocalities (by the generation of a series of equally probable age models) and of fi rst and last rodent appearances, resulting in 1,000 equally probable time series. Sample size effects on the presence or absence of rodents were observed to be fairly small and were further reduced by inferring lineage presence on a range-through basis and by excluding...

Macroevolutionary consequences of profound climate change on niche evolution in marine molluscs over the past three million years

“…We show that large-scale parameters of species' niches, in this case temperature and salinity, do not change for a phylogenetically and ecologically diverse set of marine molluscs. Although species may modify their behaviour or resource utilization, the FN places constraints on species' interactions with the environment, which potentially governs speciation and extinction processes over long time scales [10,89]. Some researchers have suggested that niche stability may promote allopatric speciation [90,91].…”

Physiological and life history strategies of a fossil large mammal in a resource-limited environment

“…The reptile-like physiological and life history traits found in Myotragus were certainly crucial to their survival on a small island for the amazing period of 5.2 million years, more than twice the average persistence of continental species (42). Therefore, we expect similar physiological and life history traits to be present in other large insular mammals such as dwarf elephants, hippos, and deer.…”

La2010: a new orbital solution for the long-term motion of the Earth

“…In recent works, the modulation of the 405 kyr component, which is caused by the beat g 3 −g 4 of period ≈2.4 Myr, has also been identified in the sedimentary records, and is thought to be a key factor in the onset of special climate events (Lourens et al 2005;Pälike et al 2006;van Dam et al 2006). There have also 3 The secular frequencies are the frequencies of the slow precessing motion of the orbit in its plane (precession of perihelion) and of the slow motion of the plane of the orbit in space (precession of the node).…”