Latitudinal variation in nematode diversity and ecological roles along the Chinese coast

Abstract

AimTo test changes in the phylogenetic relatedness, niche breadth, and life‐history strategies of nematodes along a latitudinal gradient.LocationSixteen wetland locations along the Pacific coast of China, from 20°N to 40°N.MethodsLinear regression was used to relate nematode phylogenetic relatedness (average taxonomic distinctness (AvTD) and average phylogenetic diversity [AvPD]), life‐history group (based on “c‐p” colonizer–persister group classification), and dietary specificity (based on guild classification of feeding selectivity) to latitude.ResultsWetland nematode taxonomic diversity (richness and Shannon diversity indices) decreased with increasing latitude along the Chinese coast. Phylogenetic diversity indices (AvTD and AvPD) significantly increased with increasing latitude. This indicates that at lower latitudes, species within the nematode community were more closely related. With increasing latitude, the nematode relative richness and abundance decreased for selective deposit feeders but increased for nonselective deposit feeders. The proportion of general opportunists decreased with increasing latitude, but persisters showed the opposite trend. The annual temperature range and the pH of sediments were more important than vegetation type in structuring nematode communities.Main conclusionNematode niche breadth was narrower at lower latitudes with respect to dietary specificity. Higher latitudes with a more variable climate favor r over K life‐history strategists. Nematode communities at lower latitudes contained more closely related species.

Biotic homogenization of wetland nematode communities by exotic Spartina alterniflora in China

“…In our study, for native P. australis community, soils with high moisture content and low pH tended to have bacterial dominated microbial communities and high B:F ratios, and this is consistent with other studies , Zhou et al 2017. In native communities, composition of soil communities at continental and global scales should reflect geographic variation in abiotic condition, soil types, and other dominant species that influence the soil community, resulting in high beta diversity at geographic scales (Wu et al 2016, Price et al 2018, Ren et al 2018. Thus, for both nematodes and soil microbial communities, the geographic variation found in native communities was absent, homogenized, in stands of the exotic plant.…”

“…The geographic pattern that we found for these life-history groups is consistent with previous latitudinal studies in coastal habitats in China (Wu et al 2016). Within stands of P. australis, plant and algal feeders varied in relative abundance across latitude, and all three life-history groups also varied in relative abundance across latitude.…”

“…This latitudinal pattern is consistent with the results of most studies of nematodes (Lee and Riveros 2012, Nielsen et al 2014, Wu et al 2016, although some studies have found no variation in diversity across latitude (Fonseca and Netto 2015) or even increased diversity with increasing latitude (Procter 1984). This latitudinal pattern is consistent with the results of most studies of nematodes (Lee and Riveros 2012, Nielsen et al 2014, Wu et al 2016, although some studies have found no variation in diversity across latitude (Fonseca and Netto 2015) or even increased diversity with increasing latitude (Procter 1984).…”

Contrasting latitudinal clines of nematode diversity in Spartina alterniflora salt marshes between native and introduced ranges

“…drives diversity patterns of a broad range of taxa (Mittelbach et al, 2007; Schluter & Pennell, 2017). In addition to climatic parameters, however, other studies have emphasized the importance of edaphic parameters and plant traits in driving patterns of soil nematode richness and diversity (Fonseca & Netto, 2015; Sauvadet, Chauvat, Fanin, Coulibaly, & Bertrand, 2016; Wu et al, 2016). In this study, edaphic parameters were not related to soil nematode richness and diversity in the native range of S. alterniflora (Appendix : Figures –S6).…”

“…For example, in a meta‐analysis, Song et al (2017) found that the diversity of nematodes was positively correlated with annual mean temperature. Likewise, Wu et al (2016) found that climatic variables including annual temperature range and edaphic variables like pH were very important in influencing nematode community structure in coastal wetlands dominated by native plants. Because soil nematodes may respond to fine‐scale changes in soil resources, pH and moisture, they interact with environmental parameters at fine spatial scales, and these interactions and processes may be important in determining diversity patterns (Neher, 2010).…”