DOI: 10.5061/dryad.qv9s4mwhx
title: Density-dependent changes of mating system and family structure in Brandt's voles (Lasiopodomys brandtii)

description: A mating system is an important life history for animals dealing with
 changing environments. Population density affects the plasticity of a
 mating system and subsequently the family structure of animals, but its
 impacts on mating systems and social structures are rarely investigated by
 using molecular markers in field conditions. In this study, using
 microsatellite genetic markers, we examined the changes in the social and
 genetic mating system and family structure of Brandt’s voles in the
 grassland of Inner Mongolia, China, under low-, medium-, and high-density
 enclosures (each enclosure 0.48-ha with 4 replicates.) We found, that with
 the increase in population density of the founder voles introduced into
 the enclosure in early spring, both sexes increased their number of
 genetic mating partners, while males increased their social partners,
 resulting in a more promiscuous mating system. The number of genetic
 fathers and mothers per family, the number of social offspring per founder
 male or female, and the proportion of extra-group offspring increased with
 increased density, indicating that the response of the family structure to
 density change which is consistent with the change in mating system
 observed in our study. Both male and female voles had multiple mates, but
 males had a larger number of social and genetic mates, the number of
 social and genetic offspring, and the number of social and genetic
 families. Our study highlights the significance of density-dependent
 plasticity of a mating system and family structure in affecting the
 population change of small mammals.
description: The study site had
 pre-constructed
 twenty-four 0.48-ha enclosures (80 × 60 m) with galvanized iron sheets extending
 1 m below the ground’s
 surface and 1.4 m above the surface to prevent escaping, intrusion and
 movement of burrowing rodents into, out of, and between enclosures
 (Li et al.,
 2016). A raptor‐proof
 nylon netting (10 cm mesh size) covered the top of each enclosure to
 obstruct avian predators. The integrity of each enclosure’s construction
 was regularly checked and maintained. Twelve enclosures were randomly assigned to one
 of three treatments that differed in founder population size: Low Density
 (6 ♂:6 ♀), Medium Density (12 ♂:12 ♀) and High Density (18 ♂:18 ♀). Each
 treatment had four replicates. The density level was based on a previous
 test in which 13-15 pairs of male and female voles were released into each
 enclosure in April (Li et
 al., 2016). The highest
 population density of an enclosure was recorded in one of the high-density
 enclosures at 138 individuals by the end of the breeding season (autumn)
 which translates to 287.5 voles/per ha. It was lower than the highest
 density recorded in natural conditions of the same area (590-2300
 voles/ha) (Zhong et al.,
 2007; Wan et al., 2014). We captured overwintering adults
 of Brandt’s voles
 weighing ≥ 40 g for
 enclosure tests. The experimental voles were trapped and caught from the
 wild (See section for animal trapping below). They were sexed, weighed,
 and injected with a unique PIT (Passive Integrated Transponder) tag under
 their skin using the Mini RFID Glass Capsule Tag (1.25 × 7 mm) in the
 laboratory at the field station where they were kept and observed for five
 successive days before they were released into the experimental
 enclosures. The voles were raised in the laboratory under the condition of
 natural light and room temperature. Rodent chow and water were supplied ad
 libitum. On April
 17, 2018, a total of 288 voles (144 females) were introduced into three
 different density settings as the founding population. We randomly chose
 one male and one female vole and released them into one burrow. Before
 their release, we verified their sex, and weight, scanned their PIT codes,
 and collected a tail sample (2-3 mm) using sanitized and sharp scissors
 for DNA analysis following the “Institutional Animal Use and Care
 Committee Guidebook, Institute of Zoology, Chinese Academy of Sciences
 (CAS IAUCC)”. We released
 the paired voles close to an opening of a burrow and recorded their
 released location. The enclosures contained pre-existing burrow systems
 from the previous year’s experiment and were divided into a grid of 70
 grid cells. We used these cells to record and track the movement of all
 voles in the enclosure. Before releasing the founder voles, all voles
 living in the enclosures from previous studies were removed using 80 live
 traps in each enclosure. Later, a survey found that most of them lived in burrows close to each
 other, not in the same burrow where they were released, indicating they
 re-selected their partners. 
description: Data can be opened using Microsoft Excel and other similar
 software such as LibreOffice Calc. 
description: # Density-dependent changes of mating system and family structure in
 Brandt's voles (*Lasiopodomys brandtii*)
 [https://doi.org/10.5061/dryad.qv9s4mwhx](https://doi.org/10.5061/dryad.qv9s4mwhx) ## DATA & FILE OVERVIEW ### Dataset.xlxs This dataset consists of 6 sheets named: * Population size * Per capita reproductivity * Mating system * Parent structure * Offspring structure * Family link Variables: LD - low density treatment MD - medium density treatment HD - high density treatment ## Code/Software R software (v. 3.6.1)