Variations in body size and reproductive mode of oribatid mites along an altitudinal gradient in a temperate mountain region

Abstract

Body size and reproductive strategies are usuallyconnected to several important ecological processes and have drawn the interest of numerous researchers. While numerous studies have investigated the patterns of body size or reproductive mode across elevation gradients, few studies focused on the variations in body size along environmental gradients between taxa in different reproductive modes. Here, we investigated how abundance and body size of sexual and parthenogenetic oribatid mites change along an altitudinal gradient in Changbai Mountain. The results indicated that the community-weighted mean (CWM) body size of sexual taxa was lowest at 1800 m mainly attributing to precipitation. The percentage of parthenogenetic individuals was higher at 600 m, 1600 m and 2200 m compared to other altitudes. Temperature and precipitation accounted for most of the variation in soil oribatid mite communities. Parthenogenetic species accounted for almost half of the total species suggesting parthenogenetic reproduction wins in the harsh environment. However, parthenogenetic species were more frequent in litter than soil indicating they were more susceptible to resource availability. Sexual taxa were considered exploiting resources more efficiently in soil layer as they produce genetically diverse offspring. Further, sexual taxa had larger body size in litter compared to soil habitats, their body size positively correlated with C:N ratio indicating the food resources are important in body size variations between different reproductive modes. The body size of parthenogenetic taxa was negatively related to C:P and N:P ratio suggesting that phosphorus probably increased the availability of certain food resources. The different use of resources contribute to variations in body size between sexual and parthenogenetic taxa. Our findings highlight the variations of functional traits across environmental gradients, provide new insight into climate and resource driving shifts in body size and reproductive mode among oribatid mites inhabiting mountain ranges.