Study Aim: To compare the rapid shifts in body size of mainland and island populations of a native rodent and examine the mechanisms underlying these changes.

Location: Thousand Island Lake, China, which was created in 1959 when the Xin’anjiang Dam was constructed for generating hydroelectricity.

Taxon: The Chinese white-bellied rat, Niviventer confucianus.

Methods: Field surveys were conducted from 2015 to 2018 to collect data on body size of the rodents from a set of islands and nearby mainland sites. We constructed multiple linear models to examine the relationships between body size (length and mass) of rodents and biological variables (predators, interspecific and intraspecific competitors, and food availability). We also conducted structural equation modeling (SEM) by constructing models via confirmatory path analysis.

Results: All island populations of N. confucianus had significantly larger body size (both body mass and body length) than their mainland counterparts. Moreover, populations on small and more isolated islands had larger body size than their relatives on big islands. The relative absence of predators (large-bodied mammals, snakes, and raptors) on islands was most strongly associated with shifts in the body size of rodents. The documented changes occurred after only a half-century of fragmentation.

Main conclusions: The observed rapid body enlargement of rodents after habitat fragmentation is consistent with a release from predation pressure. SEM indicated that island area, rather than island isolation, had positive effects on the richness of predators, interspecific competitors and food resources, which then had an indirect impact on body size of the rodents. In this study, we report a remarkably rapid case of mammal morphological shifts in a small mammal in response to habitat fragmentation. Given the omnipresence of dams and other anthropogenic disturbances, our findings suggest that a wave of rapid phenotypic shifts in terrestrial vertebrates is taking place in the Anthropocene.

How was this dataset collected? 

We gathered these data from our field survey. We collected the data on body size by live-trapping rodents along transects from July to September in 2016 and 2017. The primary predators of N. confucianus in the region are snakes, owls, and large carnivorous mammals such as wild boars and leopard cats. We surveyed the bird community (with an emphasis on the rodent predators like Otus bakkamoena) on mainland and island sites during 2015–2018. To assess species composition and abundance of carnivore mammals that are predators of rodents, we set camera traps on study islands and mainland sites from 2015 to 2017. We conducted surveys of all vascular plant species occurring on each mainland and island site during the growing seasons (April to November) in 2017. 

All aspects of this study were approved by Chun'an Forestry Bureau, Thousand Island Lake National Forest Park and Zhejiang University.

How has it been processed?  

We constructed multiple linear models to examine the relationships between body size (length and mass) of rodents and biological variables (predators, interspecific and intraspecific competitors, and food availability). We also conducted structural equation modeling (SEM) by constructing models via confirmatory path analysis.

The document  "data-DDi.csv" is about body length and body mass data of the rodents on different sites. 


In this dataset:
"area" is island area (h)
"length" is body length of the rodents (mm)
"weight" is body mass of the study rodents (h)
"apredator" is abundance data of rodent predators
"rpredator" is richness data of rodent predators
"acompetitor" is abundance data of rodent competitors
"rcompetitor" is richness data of rodent competitors
"aqiaodou" is abundance data of rodent food, "rqiaodou" is richness data of rodent food
"intra" is intraspecific data of the study rodents
"density" is rodent density data of the study rodents

The above data are of the body size shifts of a small mammal in the Thousand Island Lake of China.