Mammalian Niche Conservation through Deep Time

Abstract

Climate change alters species distributions, causing plants and animals to move north or to higher elevations with current warming. Bioclimatic models predict species distributions based on extant realized niches and assume niche conservation. Here, we evaluate if proxies for niches (i.e., range areas) are conserved at the family level through deep time, from the Eocene to the Pleistocene. We analyze the occurrence of all mammalian families in the continental USA, calculating range area, percent range area occupied, range area rank, and range polygon centroids during each epoch. Percent range area occupied significantly increases from the Oligocene to the Miocene and again from the Pliocene to the Pleistocene; however, mammalian families maintain statistical concordance between rank orders across time. Families with greater taxonomic diversity occupy a greater percent of available range area during each epoch and net changes in taxonomic diversity are significantly positively related to changes in percent range area occupied from the Eocene to the Pleistocene. Furthermore, gains and losses in generic and species diversity are remarkably consistent with ∼2.3 species gained per generic increase. Centroids demonstrate southeastern shifts from the Eocene through the Pleistocene that may correspond to major environmental events and/or climate changes during the Cenozoic. These results demonstrate range conservation at the family level and support the idea that niche conservation at higher taxonomic levels operates over deep time and may be controlled by life history traits. Furthermore, families containing megafauna and/or terminal Pleistocene extinction victims do not incur significantly greater declines in range area rank than families containing only smaller taxa and/or only survivors, from the Pliocene to Pleistocene. Collectively, these data evince the resilience of families to climate and/or environmental change in deep time, the absence of terminal Pleistocene “extinction prone” families, and provide valuable insights to understanding mammalian responses to current climate change.

Environmental variation is a major predictor of global trait turnover in mammals

“…We also found a strong correlation between range size and the environmental axis containing temperature. Associations between environmental factors and range size, which were independent of other species traits, have been identified in terrestrial vertebrates (Li et al., ) and range size relationships among higher mammal taxa have been shown to be consistent through geological time (DeSantis, Tracy, Koontz, Roseberry, & Velasco, ; Hadly, Spaeth, & Li, ). Our range size results show that assemblages at northern latitudes contain species with larger geographical ranges, a pattern that is consistent with Rapoport's rule (Rapoport, ; Stevens, ).…”

Processes of ecometric patterning: modelling functional traits, environments, and clade dynamics in deep time

“…Ecometric patterns in the functional traits of communities are a useful tool for studying biotic response to climate change because they are taxon-free and can therefore be used to compare responses to past changes that are documented in the fossil record with cursrent anthropogenic change (Eronen et al, 2010a;Polly et al, 2011). Most of the work that has been done on trait-environment community assembly on continental and palaeontological scales has been empirical (e.g., Wolfe, 1993;Fortelius et al, 2002Fortelius et al, , 2014Eronen et al, 2010b,c;Polly, 2010;Lawing et al, 2012), with only a few attempts to systematically examine how ecology, evolution, and phylogeny interact to produce ecometric turnover in response to climate change (e.g., Lister, 2004;Barnosky, 2005;Blois & Hadly, 2009;DeSantis et al, 2012). We used stochastic modelling to explore the links between the evolutionary theory of quantitative traits, ecological processes, and clade dynamics in the formation of ecometric patterns in static environments.…”

“…Phylogenetic turnover was common in mammals in response to the rapid expansion of open habitat grasslands in the Late Miocene followed by global temperature downturn and closing of many habitats in the Quaternary (DeSantis et al, 2012;Liow & Finarelli, 2014;Fraser, Gorelick & Rybczynski, 2015). Borophagine canids, for example, were diverse in North American during the Miocene, but became extinct and were replaced by the global radiation of the Caninae, which is the only extant clade of canids, after the end of the Miocene (Tedford et al, 2009).…”

Past influences present: Mammalian species from different biogeographic pools sort environmentally in the Indian subcontinent

“…Moreover, species within a lineage (or genus) largely show related climatic tolerances and tightly coupled niche and dispersal limitations (Ulrich et al 2009, Olalla-Tárraga et al 2011. Hadly et al (2009) and DeSantis et al (2012) demonstrate the relative constancy of geographical range sizes in North American mammals suggesting that important ecological and rangerelated traits are conserved above the species level. Additionally, contemporary species distributions may not be in equilibrium with their environment, and may be influenced by factors other than environmental preference including hunting and habitat loss.…”