Temporal changes in cranial size in South African vlei rats (Otomys): evidence for the ‘third universal response to warming’

On the role of (and threat to) natural history museums in mammal conservation: an African small mammal perspective

“…One example addressing the impacts of climate change on African small mammals is the work on vlei rats in the genus Otomys F. Cuvier, 1824 in South Africa (Nengovhela et al 2015). Examining cranial size in two species of Otomys, Nengovhela et al (2015) demonstrated rapid morphological change over a 100 year period in response to warming temperatures associated with climate change.…”

“…One example addressing the impacts of climate change on African small mammals is the work on vlei rats in the genus Otomys F. Cuvier, 1824 in South Africa (Nengovhela et al 2015). Examining cranial size in two species of Otomys, Nengovhela et al (2015) demonstrated rapid morphological change over a 100 year period in response to warming temperatures associated with climate change. Another study using predictive niche modelling for forest shrews in the genus Myosorex Gray, 1837 based on records from museum specimens resulted in their uplisting on the IUCN Red List due to threats of future climate change scenarios (Taylor et al 2017).…”

Life history and habitat do not mediate temporal changes in body size due to climate warming in rodents

“…Recently, morphological responses to climate change (usually entailing body size) have received growing interest, with changes reported in both aquatic and terrestrial environments ( Gardner et al, 2011 ; Sheridan & Bickford, 2011 ). Body size varies geographically and temporally within species ( Alhajeri & Steppan, 2016 ; McNab, 2010 ; Nengovhela, Baxter & Taylor, 2015 ; Stumpp, Fuzessy & Paglia, 2016 ; Yom-Tov & Geffen, 2011 ; Yom-Tov & Yom-Tov, 2004 ; Yom-Tov & Yom-Tov, 2005 ; Yom-Tov & Yom-Tov, 2012 ; Yom-Tov et al., 2006 ) in response to environmental variables including ambient temperature and precipitation ( Bergmann, 1847 ; Blackburn, Gaston & Loder, 1999 ; Blois, Feranec & Hadly, 2008 ; James, 1970 ), food availability ( McNab, 2010 ; Yom-Tov & Yom-Tov, 2004 ; Yom-Tov & Yom-Tov, 2005 ; Yom-Tov, Yom-Tov & Baagoe, 2003 ; Yom-Tov et al, 2010a ), predation regimes ( Gosler, Greenwood & Perrins, 1995 ), habitat fragmentation ( Schmidt & Jensen, 2003 ) and competition ( Meiri, Yom-Tov & Geffen, 2007 ; Raia & Meiri, 2006 ). Different mechanisms have been advanced to explain these effects, most commonly, in a geographic context (due to altitude and latitude), Bergmann’s Rule, which states that individuals under warmer climates should be smaller in body size as compared to individuals in colder climates ( Bergmann, 1847 ; Mayr, 1956 ).…”

“…While this rule was originally formulated at an interspecific pattern within genera, by far, most studies, including metanalyses, test this rule at the intraspecific level ( Alhajeri & Steppan, 2016 ). Bergmann’s Rule or related hypotheses that explain inverse temperature-body size clines in endotherms and ectotherms (termed “Bergmann’s clines” hereafter) have been invoked to explain body size changes due to global climate warming in a range of animals including insects, birds, rodents and salamanders ( Babin-Fenske, Anand & Alarie, 2008 ; Blanckenhorn, 2015 ; Caruso et al, 2014 ; McCoy, 2012 ; Nengovhela, Baxter & Taylor, 2015 ). However, the authenticity, general applicability and ultimate causation of Bergmann’s clines have been questioned ( Calder, 1984 ; Gardner et al, 2011 ; McNab, 1971 ; McNab, 2010 ; Millien et al, 2006 ; Scholander, 1955 ; Teplitsky & Millien, 2014 ; Yom-Tov & Geffen, 2006 ).…”

“…The main aim of our study was to relate new and existing data on rodent temporal changes in body size with life history traits and environmental attributes (like habitat type, elevational range, maximum latitude and range size; from here on referred to as “habitat”) across seven families of rodents (50 species) in order to test the hypothesis that life history attributes and habitat may be an important determinant of the tendency of rodent species to respond phenotypically to climate warming and to test the applicability of the “third universal response to climate warming” ( Gardner et al, 2011 ; Nengovhela, Baxter & Taylor, 2015 ) . Rodents and other small mammals (like shrews) are considered as ideal model animals because of their small size, short life spans, small dispersal distances and fast generation time as this may cause rapid morphological changes ( Poroshin, Polly & Wójcik, 2010 ) and adaptive convergence ( Samuels, 2009 ), which may be exacerbated by global environmental changes.…”