Niches and neutral processes contribute to the resource-diversity relationships of stream detritivores

Abstract

1. Explaining resource-diversity relationships is a long-standing goal in ecology, and there is currently little consensus as to the relative contributions of neutral versus a variety of proposed niche-related mechanisms. 2. The resource-diversity relationship of insect detritivores was examined in a survey of 25 small, parallel streams flowing into the Bay of Fundy in eastern Canada, with the objective of determining whether neutral processes (sampling effects) could account for the observed patterns. 3. Detritivore taxonomic richness showed a positive, but decelerating relationship with quantity of detritus. Richness also increased with catchment area and with stream permanence. 4. Species distribution patterns were significantly nested, and low resource streams (little detritus) tended to have species with large ranges (i.e. found in many or most streams). 5. Sampling effects could explain only part of the positive relationship between richness and detrital resources, but accounted for the species richness-area relationship. 6. Two mechanisms that could potentially increase niche space as resource abundance increased were rejected: there was no evidence that riparian forest diversity or beta diversity increased with detrital resources. 7. Two niche-related mechanisms were consistent with existing data, but will require further testing. First, flood disturbance may decrease species richness by eliminating species that require benign habitat, and lowering detritus retention, producing a positive correlation between detritivore richness and resources. Second, large wood in streams located in older riparian forest may increase habitat heterogeneity (number of niches) and the retention of organic matter, again leading to a positive relationship between detritivore diversity and detrital resources. 8. It was concluded that the positive 'productivity-diversity' relationship for stream detritivores was most likely produced in part by sampling effects, but also by ecological processes (disturbance and succession) that simultaneously influence resource level and niche availability.

The commonness of rarity in a deep‐sea taxon

“…6). This positive correlation is in contrast to most theories suggesting that higher productivities should lead to smaller ranges (Evans et al 1999, Bonn et al 2004, Sircom and Walde 2010, Whitton et al 2012). Sanders (1977) proposed that low productivity would favor specialization to consume previously underutilized carbon sources, supported by the results here (Fig.…”

Metabolic Niches and Biodiversity: A Test Case in the Deep Sea Benthos

“…General additive model relationship is shown for the conditional relationship once body size, mean depth, mean latitude, and temperature are accounted for. Bonn et al, 2004;Sircom and Walde, 2010;Whitton et al, 2012). One possible reason for this result is that the analyses here control for a variety of other geographic, environmental, and biological factors correlated with body size.…”

“…In addition, within a given environmental setting HET are predicted to possess larger biogeographic ranges as home range sizes increase to incorporate the increased food resources required (McNab, 1963;Brown and Maurer, 1987). Energetics may also impact biogeographic range size because of the connections with niche breadth (Slatyer et al, 2013): higher energy availability can lead to smaller ranges because species become resource specialists (Sircom and Walde, 2010;Whitton et al, 2012). Range size is also impacted by the degree of environmental variability in both time and space.…”

Current velocity as a factor in determining macroinvertebrate assemblages on wood surfaces

“…Enhanced resources can not only increase taxa numbers and richness but may also expand niche space (Sircom and Walde 2011). Niche expansion is a second process that may explain the assemblage patterns we found on wood.…”