Introduction
Soil biodiversity drives complicated ecological processes and plays a
crucial role in exerting ecosystem functions and the provision of
ecosystem services (Nielsen et al., 2012; Wagg et al., 2014; Geisen et
al., 2018). The composition of soil animal communities thus strongly
influences ecosystem multifunctionality (Wagg et al., 2014). For
instance, soil animal communities may alter microbial activity, litter
decomposition, nutrient mineralization, soil respiration, and plant
community composition (Bradford et al., 2002; De Deyn et al., 2003;
Eisenhauer et al., 2012; Johnston & Sibly, 2018). Consequently, shifts
in soil animal community composition could dramatically influence the
functioning and stability of terrestrial ecosystems (Sjursen et al.,
2005; Suttle et al., 2007; Briones et al., 2009; Eisenhauer et al.,
2014; Handa et al., 2014). Yet, little is known about the spatial and
environmental factors that shape soil animal communities on a regional
and global scale (Johnston & Sibly, 2020). To understand the ecosystem
functioning and the mechanism of community composition evolvement, it is
necessary to identify the factors that shape the distribution and
structure of various soil faunas (Crowther et al., 2019).
Species turnover pattern (or beta diversity) is a basic pattern in
biogeography and macroecology (Gaston, 2000), and it provides
fundamental insights into mechanisms of community assembly, especially
on a large scale (Anderson et al., 2011; Lafage et al., 2015). However,
species turnover patterns have received less attention than alpha
diversity (Lennon et al., 2001), and measures of species turnover in
previous studies usually based on single method (Gao et al., 2021).
Utilizing different methods to measure the species turnover rates can
better avoid the error caused by methods of measurement. Meanwhile, most
studies on species turnover have been conducted locally (Kraft et al.,
2011; Sasaki & Yoshihara, 2013). A few studies did investigate species
turnover on large geographic scales, but they mostly focused on plants
and animals. For example, recent studies have demonstrated that
dispersal abilities were a key factor for both woody plants and birds in
species turnover spatially (Chen et al., 2016; Sreekar et al., 2020).
The global biogeography of soil animals has begun to gain attention only
recently (Caruso et al., 2005; Dunn et al., 2009; van den Hoogen et al.,
2019; Medini et al., 2021). Most of these studies focused on specific
soil animal communities. For example, previous studies showed that
earthworm community composition is determined by the mobility of the
organisms (Medini et al., 2021), oribatid mite by spatial factors
(Caruso et al., 2005), termites of Hymenoptera by temperature and
precipitation (Dunn et al., 2009),
and nematodes by temperature (van den Hoogen et al., 2019). Despite our
accumulated knowledge about biogeographic patterns of soil biota, the
underlying mechanisms of the distribution patterns remain unexplored (Xu
et al., 2020). Particularly, the studies on the patterns of
comprehensive taxa species turnover across latitudes are limited.
Environmental filtration and spatial processes have been associated with
variations in ecological communities and biodiversity. However, their
significance on multiple dimensions of beta diversity has not been fully
explored in soil fauna (Li et al., 2020). Several research studies
indicated that species coexistence
was attributed to different environmental factors, such as habitat
heterogeneity (Li et al.,2017), temperatures in different climates
(Oliver et al., 2009), and soil nutrients (John et al., 2007). These
factors provided species with different resources, time, and space to
achieve coexistence as implied by the niche theory (Jia et al., 2015;
Escudero & Valladares, 2016). Alternatively, neutral processes stated
that species coexistence was resulted from biogeographic barriers and
low dispersal abilities (Hubbell, 2001; Jia et al., 2015). Though two
different theories, the niche theory and neutral processes actually
jointly explained the coexistence of soil animal communities. They just
have different roles on corresponding spatial scales (Gao et al., 2014).
The underlying environmental controls that shape latitudinal shifts in
soil animal communities on a global scale, however, have not been
identified (Johnston & Sibly, 2020), especially the mechanisms.
Therefore, our study aimed at addressing this knowledge gap and explored
the influence of spatial and environmental factors on soil animal
species composition across globally distributed sites by synthesizing
data of comprehensive taxa of soil animal communities.
The objectives of the current study were: (1) to obtain an integrated
analysis of the similarity of soil animal species composition along the
latitude in East Asia, (2) to identify the patterns of species turnover
along the latitude using two measures of species turnover, and (3) to
assess the relative influence of environmental and neutral processes on
species turnover of overall and functional forms of soil animals.