Recent and Widespread Rapid Morphological Change in Rodents

Abstract

In general, rapid morphological change in mammals has been infrequently documented. Examples that do exist are almost exclusively of rodents on islands. Such changes are usually attributed to selective release or founder events related to restricted gene flow in island settings. Here we document rapid morphological changes in rodents in 20 of 28 museum series collected on four continents, including 15 of 23 mainland sites. Approximately 17,000 measurements were taken of 1302 rodents. Trends included both increases and decreases in the 15 morphological traits measured, but slightly more trends were towards larger size. Generalized linear models indicated that changes in several of the individual morphological traits were associated with changes in human population density, current temperature gradients, and/or trends in temperature and precipitation. When we restricted these analyses to samples taken in the US (where data on human population trends were presumed to be more accurate), we found changes in two additional traits to be positively correlated with changes in human population density. Principle component analysis revealed general trends in cranial and external size, but these general trends were uncorrelated with climate or human population density. Our results indicate that over the last 100+ years, rapid morphological change in rodents has occurred quite frequently, and that these changes have taken place on the mainland as well as on islands. Our results also suggest that these changes may be driven, at least in part, by human population growth and climate change.

Comparación de la morfología geométrica de la mandíbula de dos roedores africanos, Thryonomys swinderianus y Cricetomys gambianus (Rodentia: Thryonomyidae y Nesomyidae)

“…A more dorsally placed and posteriorly oriented coronoid process relative to the articular condyle in C. gambianus is similar to ruminant's mandible (Olopade, 2006) located well above the level of the cheek tooth row in contrast to T. swinderianus whose coronoid and condyle are placed at the same level with the tooth rows; a trait synonymous with primitive carnivoran condition (Figueirido et al, 2008) in some members of Heteromydae (Pergams & Lawler, 2009) perhaps for mechanical advantage in prey/ food summarization.…”

“…A rapidly extending geographic distribution of the two species has been observed in areas otherwise not reported especially islands and landlocked enclaves (Hendry et al, 2006;Wright et al, 2006;Pergams & Lawler, 2009). Ecological separation and home range overlaps exist between them as they share and interact in conflict or competitively but not necessarily exploitatively within territory limits (Ajayi et al, 1978;Happolds, 1987).…”

“…Ecological separation and home range overlaps exist between them as they share and interact in conflict or competitively but not necessarily exploitatively within territory limits (Ajayi et al, 1978;Happolds, 1987). Occasional interaction between colonies of both in drought periods has increased in frequency due to human and natural agents of change (Pergams & Lawler, 2009). A colony comprise of a male and about five females (Onyeanusi et al, 2009;) making seasonal availability or scarcity of food, high temperature deviations, flooding and moonlight the limiting or promoting factors of interactions (Happolds, 1987).…”

Effects of Anthropogenic Events and Viral Persistence on Rodent Reservoirs of Hantavirus Infection: Understanding Host-Pathogen Interactions Facilitates Novel Approaches to Intervention Strategies

“…Effects of urbanization, such as habitat fragmentation, deforestation and food scarcity leading to increased feeding competition, act as chronic stressors for rodents. This results in rapid physiological changes and lower immunity to viruses, which is mediated by GCs [52,53].…”

Collectively, we need to accelerate Arctic specimen sampling

“…Seabird specimens were used to document rises in mercury levels in the Atlantic Ocean and high-latitude New World birds (Thompson et al 1998;Evers et al 2014). Population changes and conservation -Historical specimens have also been used to show increased levels of environmental stress and morphological and genetic changes through time in extant populations (e.g., Glenn et al 1999;Groombridge et al 2000;Lens et al 2002;Pergams and Lawler 2009;Gardner et al 2011). Invasive species have also become important in collections-based research (Lavoie 2012).…”