On spatiotemporal patchiness and the coexistence of five species of Chronogaster (Nematoda: Chronogasteridae) in a riparian wetland

Abstract

Spatiotemporal patchiness in the soil environment is thought to be crucial for the maintenance of soil biodiversity. It provides diverse microhabitats (allowing resource partitioning), and presents these in a complex mosaic, such that competitors may be spatially and temporally separated (promoting patch dynamics). The objective of our study was to assess the importance of patch dynamics for the maintenance of landscape-level nematode diversity. The spatiotemporal aggregation patterns in populations of five species of the bacterivorous genus Chronogaster were analyzed for a 0.7-ha riparian wetland, during four seasons, using geostatistical methods (spatiotemporal variograms, cross-correlograms, and log-normal kriging). We found that for the three most abundant species, aggregation was significant over distances of 13-39 m, with intraspecific aggregation stronger than interspecific aggregation. In addition, species patterns appeared to be temporally dynamic: local population declines alternated with local blooms at different sites and seasons. One species was consistently present at the same few sites, but the other species showed gradual temporal decreases and increases at different locations in the wetland. Combining nematode patterns with information on soil resource distributions and Chronogaster ecology, indicated that both soil resource patchiness and repeated, but largely unpredictable, disturbances caused by local soil moisture fluctuations could promote landscape-level Chronogaster diversity by providing ample 'probability refuges.' Local species populations, reduced by competition, predation and drought, could recolonize patches either through the awakening of local dormant 'seed populations,' or through limited passive dispersal by wind, water, and phoresis. We suggest that the spatiotemporal Chronogaster data provide preliminary evidence for the importance of patch dynamics in maintaining soil nematode diversity.

The role of edaphic, vegetational and spatial factors in structuring soil animal communities in a floodplain forest of the Dnipro river

“…Soil organisms are also characterized by spatial patterns at the meso-level (1-100 m) (Saetre, 1999;Ettema et al, 2000;Jimenez et al, 2006;Widenfalk et al, 2015). At this level, the following environmental properties are important: gradients of soil pH, humidity and composition of vegetation cover (Ettema and Wardle, 2002;Berg, 2012).…”

Spatial Variation as a Tool for Inferring Temporal Variation and Diagnosing Types of Mechanisms in Ecosystems

“…Meanwhile, the breadth of spatiotemporal behaviors seen suggests a range of spatial variation, synchrony and persistence combinations leading to temporal variation in nature. Our framework may be useful for cataloguing these types of spatiotemporal dynamics in ecosystems (e.g., Table 1), and for making broad-stroke inferences about spatiotemporal mechanisms (e.g., population rescue effects [26], [57], predator-prey cycles [58], species coexistence [59], [60], and invasive species spread [61]). …”

Impact of trophic ecologies on the whereabouts of nematodes in soil

“…For the spatially structured bacterivores, no correlation with soil resource patterns could be determined . However, when the patchiness of bacterivore Chronogaster was examined at species level in the same wetland, the results pointed at an important role of largely unpredictable, local variations in humidity on the mesoscale distribution of individual bacterivorous nematode species (Ettema et al 2000).…”

“…Most papers focus on nematode feeding types Freckman, 1995, Viketoft, 2013), on restricted number taxa within a feeding type , Ettema et al, 2000, or on individual plant-parasitic nematode species (Been and Schomaker, 2006). Geostatistical modelling is a potential powerful approach to reveal spatial patterns in soil .…”

“…In nematode ecology studies, coefficients of variation of replicate samples in are typically 100% or above (e.g. Ettema et al 2000;Liang et al 2005;Viketoft et al 2009;. This source of variation is usually ignored, or -if recognized -it remains unexplained.…”