Earthquake-Related Changes in Species Spatial Niche Overlaps in Spring Communities

Abstract

Species interactions between stygobites (obligate groundwater organisms) are poorly known, reflecting the difficulty in studying such organisms in their natural environments. Some insight can be gained from the study of the spatial variability in microcrustacean communities in groundwater-fed springs. Earthquakes can increase hydraulic conductivity in the recharge area of karstic aquifers and flow rates in discharge zones, thus dislodging stygobites from their original habitats to the spring outlets. Earthquakes are expected to alter species spatial niche overlap at the spring outlets, where stygobites coexist with non-stygobites living in benthic and subsurface habitats. We compared the abundance of stygobiotic and non-stygobiotic microcrustaceans in groundwater-fed springs before and after the 6.3-Mw earthquake that hit the karstic Gran Sasso Aquifer (Italy) in 2009. Pre-seismic (1997, 2005) overall niche overlaps were not different from null expectations, while post-seismic (2012) species mean niche overlaps were higher, following the redistribution of animals caused by the earthquake-triggered discharge. The reduced abundance of stygobites following their dislodgement from the aquifer and the concomitant displacement of non-stygobites led to a higher post-seismic co-occurrence of stygobites and non-stygobites. Changes in aquifer structure destroyed pre-seismic species segregation patterns by creating new or strengthening already existing interactions.

Potential of A Trait-Based Approach in the Characterization of An N-Contaminated Alluvial Aquifer

“…In this study, the variance explained by the univariate models was low and this indicated that further factors, in addition to those already investigated, must be taken into account in the future to better explain the observed biological patterns. For instance, copepod species interactions could play a role in determining the biological assemblages in VO_GWB as already observed in other aquifers [74]. Similarly, previous studies showed that the grain size composition of sediments [75][76][77], and the lowering of the groundwater table [21,75], could influence the biological assemblage's patterns in alluvial aquifers.…”

A review of methods for quantifying spatial predator–prey overlap

“…A number of overlap metrics have been developed for ecological applications. These metrics have been applied to diverse ecological questions, including the examination of niche equivalency of species in environmental space (Broennimann et al, 2012;Warren, Glor, & Turelli, 2008), overlap of animal home ranges (Fieberg & Kochanny, 2005), overlap in dietary niche among competitors (Woodward & Hildrew, 2002), and changes in resource partitioning among species after environmental perturbations (Fattorini et al, 2017). Several reviews of overlap metrics have discussed their mathematical and biological properties and have investigated sources of bias and error (e.g., Hurlbert, 1978;Krebs, 1989;Rödder & Engler, 2011).…”

Finding answers in the dark: caves as models in ecology fifty years after Poulson and White

“…For instance, the effects of earthquakes on groundwater habitats was recently documented to determine a general reduction of diversity (Galassi et al 2014), variations in abundance patterns (Fattorini et al 2018) and an increase in the spatial niche overlap of previously isolated species (Fattorini et al 2017). For instance, the effects of earthquakes on groundwater habitats was recently documented to determine a general reduction of diversity (Galassi et al 2014), variations in abundance patterns (Fattorini et al 2018) and an increase in the spatial niche overlap of previously isolated species (Fattorini et al 2017).…”

“…Taking advantage of local site-specific phenomena, such as earthquakes, floods and volcanic eruptions, a few authors have recently shown that subterranean habitats may actually represent unusual, yet promising systems in which to investigate environmental stochasticity. For instance, the effects of earthquakes on groundwater habitats was recently documented to determine a general reduction of diversity (Galassi et al 2014), variations in abundance patterns (Fattorini et al 2018) and an increase in the spatial niche overlap of previously isolated species (Fattorini et al 2017). Ortuño et al (2013) showed how periodic flooding may extirpate native community in specific subterranean habitats (the so-called 'Alluvial MSS'), enhancing the possibility to use these systems to study re-colonization processes and meta-population dynamics, just like in the famous case of the Krakatau Islands (Thornton et al 1988, Whittaker et al 1989.…”