Disentangling the effects of dispersal mode on the assembly of macroinvertebrate assemblages in a heterogeneous highland region

Abstract

Disentangling the effects of dispersal mode on the environmental and spatial processes structuring biological assemblages is essential to understanding the mechanisms of species coexistence and maintenance. Here, we use field investigations to link dispersal mode with environmental and spatial processes that control stream macroinvertebrate assemblage structure across the Yarlung Zangbo Grand Canyon of Tibet (Tibetan Plateau). We sampled macroinvertebrates in streams that occur in 4 distinct regions. Each of these regions has a steep elevational gradient but different altitude ranges, climate types, and water replenishment sources. We classified macroinvertebrate taxa into passive and active dispersal mode groups to test whether macroinvertebrates with different dispersal modes responded differently to environmental and spatial processes. Our results showed that the assemblage structure of active dispersal groups was more strongly determined by environmental variables (habitat filtering/species sorting) than spatial factors both within and across regions. In contrast, the structure of passive dispersers was more strongly associated with spatial factors than environmental filtering in the entire study area and within lower canyon regions. However, spatial effects were not important for either type of dispersal group in the upper canyon regions, especially in the region with glacier-fed streams, indicating the predominance of species sorting processes in these harsh environments. Furthermore, the spatial structuring of assemblages became stronger as habitat filtering declined, which indicates a reduction in species sorting processes in less harsh environments. Our findings demonstrate diverse responses of macroinvertebrate assemblages to environmental and spatial processes across this poorly-known highland river system, and imply that dispersal mode influences the underlying mechanisms of community variation.

Ecological processes underlying community assembly of aquatic bacteria and macroinvertebrates under contrasting climates on the Tibetan Plateau

“…These contrasting results may be due to the different taxonomic groups, biodiversity metrics or environmental contexts, such as the stronger differences in hydrologic conditions in Daniel et al's (2019) study compared to this study. Nevertheless, the support from both field observations (this study) and experiments (Chase, 2007) implies that comparatively harsh conditions have the potential to act as strong environmental filters, while there may be more room for random events in more benign conditions (see also Li et al, 2019). It is nevertheless important to keep in mind that any results based on actual field data provide insights that are highly context dependent.…”

“…Macroinvertebrates were first sorted in the laboratory and subsequently identified to the genus level when possible using standard keys (Morse, Yang, & Tian, 1994). Genus level was the target taxonomic level here because there are no sufficient taxonomic keys for finerlevel identifications of macroinvertebrates for this region (see also Li et al, 2019). Genuslevel information is usually, however, highly congruent with species-level information (e.g.…”

Spatial context strongly affects community composition of both passively and actively dispersing pool invertebrates in a highly heterogeneous landscape

“…However, more comprehensive studies have emerged in recent years, finding both aquatic and terrestrial metacommunities to be spatially structured (e.g., Rouquette et al., ; Soininen, ). Within freshwater ecosystems, taxa with high dispersal ability have been observed to be structured more by local characteristics (e.g., Li et al., ; Warfe et al., ), while spatial structure appears to be more important for poorer dispersers (e.g., Castillo‐Escrivà, Aguilar‐Alberola, & Mesquita‐Joanes, ; De Bie et al., ; Padial et al., ). The observed patterns further depend on the habitat type (Curry & Baird, ; Schmera et al., ), spatial scale (Patrick & Yuan, ) or topography (Razeng et al., ), and are often highly context dependent (Heino et al., ).…”

Lateral hydrological connectivity differentially affects the community characteristics of multiple groups of aquatic invertebrates in tropical wetland pans in South Africa

“…The highest levels of diversity in river floodplain systems are often observed at intermediate levels of LHC (Gallardo et al, 2014;Turić et al, 2015;Ward & Tockner, 2001). Active dispersing invertebrates might show in stronger responses to local environmental variables, indicating the importance of species sorting and habitat filtering, and a weaker response to LHC, whereas passive dispersing invertebrates might respond stronger to LHC (Dube et al, 2017;Hill, Heino, Thornhill, Ryves, & Wood, 2017;Li et al, 2019). Active dispersing invertebrates might show in stronger responses to local environmental variables, indicating the importance of species sorting and habitat filtering, and a weaker response to LHC, whereas passive dispersing invertebrates might respond stronger to LHC (Dube et al, 2017;Hill, Heino, Thornhill, Ryves, & Wood, 2017;Li et al, 2019).…”

“…Empirical studies have shown that multiple organism groups including zooplankton, macroinvertebrates, fish, amphibians, and macrophytes tend to respond differently to variation in hydrological habitat connectivity (Frisch, Libman, D'surney, & Threlkeld, 2005;Morán-Ordóñez et al, 2015;Ward et al, 1999), which seems largely related to life history characteristics and dispersal mode (active versus passive). Active dispersing invertebrates might show in stronger responses to local environmental variables, indicating the importance of species sorting and habitat filtering, and a weaker response to LHC, whereas passive dispersing invertebrates might respond stronger to LHC (Dube et al, 2017;Hill, Heino, Thornhill, Ryves, & Wood, 2017;Li et al, 2019).…”