COS 74-3 - CANCELLED - Spatiotemporal patterns of intraspecific trait variation in mammals and birds

Abstract: During the past centuries, species morphological traits have been experiencing rapid shifts due to global environmental change, including average body size decline that has been widely reported in multiple taxa. Compared to mean body size, however, less is known about spatiotemporal patterns of intraspecific trait variation (ITV), which is associated with species niche breadth and is also important to understanding species’ ability to cope with novel environmental challenges. The goals of our study are assessing spatiotemporal patterns of body size ITV in mammals and birds, and determining important covariates that are associated with species ITV changing trends.

We complied a specimen dataset including individual-level body size information of mammals and birds collected in North America and China from 1880 to 2020, and assessed body size ITV trends during the recent 140 years. Here we show that body size ITV has increased by 9.59% for mammals (n=302) and 30.67% for birds (n=78), while average body size has decreased by 3.13% for mammals (n=302) and 10.11% for birds (n=78). In addition, we show that ITV temporal changing trend has varied across species, with human-harvested species had higher probability of ITV increase, and larger-sized mammals had higher probability of ITV decrease. In conclusion, this study suggests possible niche expansion in many mammal and bird species, which may buffer against ecological impacts from average downsizing, but it also risks increased maladaptation to rapidly changing environments. As trait mean and variance do not necessarily respond in similar ways to anthropogenic pressures, both should be considered for a clearer understanding of species response to global change.