Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant

Abstract

The 1-m-tall dwarf elephant Palaeoloxodon falconeri from the Pleistocene of Sicily (Italy) is an extreme example of insular dwarfism and epitomizes the Island Rule. Based on scaling of life-history (LH) traits with body mass, P. falconeri is widely considered to be ‘r-selected’ by truncation of the growth period, associated with an early onset of reproduction and an abbreviated lifespan. These conjectures are, however, at odds with predictions from LH models for adaptive shifts in body size on islands. To settle the LH strategy of P. falconeri, we used bone, molar, and tusk histology to infer growth rates, age at first reproduction, and longevity. Our results from all approaches are congruent and provide evidence that the insular dwarf elephant grew at very slow rates over an extended period; attained maturity at the age of 15 years; and had a minimum lifespan of 68 years. This surpasses not only the values predicted from body mass but even those of both its giant sister taxon (P. antiquus) and its large mainland cousin (L. africana). The suite of LH traits of P. falconeri is consistent with the LH data hitherto inferred for other dwarfed insular mammals. P. falconeri, thus, not only epitomizes the Island Rule but it can also be viewed as a paradigm of evolutionary change towards a slow LH that accompanies the process of dwarfing in insular mammals.

Variation and process of life history evolution in insular dwarfism as revealed by a natural experiment

“…This species was observed to have a fast life history as the age distribution of its fossil assemblage was skewed to calves and immature individuals [83]. Nevertheless, a histological study suggested that this pygmy elephant had a much slower growth rate than its mainland relatives, and sexual maturity was within the range of extant elephants [84], thus this contradiction requires a further synthetic study on this species. The differences in the life history response among Mediterranean mammals, however, are unsurprising, given that these Mediterranean islands were much bigger than those for which we report life history changes (i.e., the Blakely Island, Kerama Islands, Yakushima Island, Okinawa Island, and Mallorca Island).…”

“…✝ Fossil taxa. * Life history of Elephas falconeri was disputed [83, 84]. ** Muntiacus reevesi was an artificially introduced animal in the 1980s.…”

Wild boar versus domestic pig—Deciphering of crown growth in porcine second molars

“…The commonly held view that tooth morphology represents an evolutionarily conservative trait, that is, that it changes comparatively slowly over the course of evolution (Hillson, 2014;Jordana et al, 2014;Smith, 1989Smith, , 1991Smith, , 2000, is corroborated by our findings with respect to the overall dimensions of the pig M 2 . However, tion (Jordana & Köhler, 2011;Köhler et al, 2021;Köhler & Moyà-Solà, 2009). We consider the selective pressure occurring in the process of pig domestication to have acted in the opposite direction.…”

“…The analysis of incremental growth marks with known periodicities in dental hard tissues enables the reconstruction of tooth growth and inferences on life‐history traits of extant and fossil species (Dean, 1987 , 2000 , 2006 ; Dean et al, 1993 , 2020 ; Dirks et al, 2009 , 2012 ; FitzGerald, 1998 ; Hogg, 2018 ; Köhler et al, 2021 ; O'Meara et al, 2018 ; Schwartz et al, 2002 , 2006 ; Shellis, 1998 ; Smith et al, 2006 ). In mammalian enamel and dentine, the periodicities of growth marks have been determined by labelling of the forming tissues (Bromage, 1991 ; Bromage et al, 2009 ; Emken et al, 2021 ; Iinuma et al, 2004 ; Kawasaki & Fearnhead, 1975 ; Kierdorf et al, 2013 ; Ohtsuka & Shinoda, 1995 ; Okada & Mimura, 1938 , 1940 ; Papakyrikos et al, 2020 ; Schour & Poncher, 1937 ; Smith, 2006 ; Yilmaz et al, 1977 ).…”

Paleohistology of Caraguatypotherium munozi (Mammalia, Notoungulata, Mesotheriidae) from the early late Miocene of northern Chile: A preliminary ontogenetic approach

“…Paleohistology is a useful tool for elucidating the growth patterns, life history and physiology of extinct vertebrates [20][21][22][23][24][25]. It has provided insights on several aspects of the evolutionary biology of extinct mammals including the reconstruction of their growth and development [22,[26][27][28][29], adaptations to different lifestyles [27], ecology [22,29,30] and physiology [22,27].…”