High biogeographic and latitudinal variability in gastropod drilling predation on molluscs along the eastern Indian coast: Implications on the history of fossil record of drillholes

Abstract

Studies on the large-scale latitudinal patterns of gastropod drilling predation reveal that predation pressure may decrease or increase with increasing latitude, or even show no trend, questioning the generality of any large-scale latitudinal or biogeographic pattern. Here, we analyze the nature of spatio-environmental and latitudinal variation in gastropod drilling along the Indian eastern coast by using 76 samples collected from 39 locations, covering ~2500 km, incorporating several ecoregions, and ~15° latitudinal extents. We find no environmental or latitudinal gradient. In fact, drilling intensity varies highly within the same latitudinal bin, or oceanic sub-basins, or even the same ecoregions. Moreover, different ecoregions with their distinctive biotic and abiotic environmental variables show similar predation intensities. However, one pattern is prevalent: some small infaunal prey taxa, living in the sandy-muddy substrate—which are preferred by the naticid gastropods—are always attacked more frequently over others, indicating taxon and size selectivity by the predators. The result suggests that the biotic and abiotic factors, known to influence drilling predation, determine only the local predation pattern. In the present case, the nature of substrate and prey composition determines the local predation intensity: soft substrate habitats host dominantly small, infaunal prey. Since the degree of spatial variability in drilling intensity within any time bin can be extremely high, sometimes greater than the variability across consecutive time bins, temporal patterns in drilling predation can never be interpreted without having detailed knowledge of the nature of this spatial variability within a time bin.

Environmental correlates of molluscan predator–prey body size in the northern Gulf of Mexico

“…Similar geographic trends in predator-to-prey size ratios were not observed in our study when we compared populations in productive habitats adjacent to the Mississippi River with those in less-productive environments offshore coastal Florida. Variation in the size of drilling predators, and the frequency of drilling predation, could potentially reflect spatial variation in the composition of predators (Alexander and Dietl 2001;Mondal et al 2021); however, this is unlikely to be driving the observed patterns in the northern gulf, as >90% of observed drill holes exhibited morphologies indicative of naticid predation, and predator identity did not vary geographically in our samples.…”

Predatory drilling on molluscan assemblages along the Patagonian shelf (southern Argentina)

“…In the same way, different abiotic and biotic factors could also influence the predator-prey interaction at a local level. Also Mondal et al (2021) suggested that the nature of substrate can determine the prey and predator composition, including life mode and taxonomic compositions at any location, influencing local drilling predation.…”

“…Previous studies on this topic reveal that predation pressure may decrease or increase with increasing latitude, or even show no trend, questioning the generality of any large-scale latitudinal or biogeographic pattern (e.g. Vermeij et al, 1989;Hansen and Kelley, 1995;Alexander and Dietl, 2001;Hoffmeister and Kowalewski, 2001;Visaggi and Kelley, 2015;Mondal et al, 2021). In southern South America, this issue has been previously treated by Martinelli et al (2013) for a sector (between 42°and 48°S) along the Patagonian coast, concluding that drilling predation does not indicate a latitudinal/thermodependent trend, but rather seems to be linked to local factors, which includes anthropogenic reasons, among others.…”

“…In this study, we explore drilling predation on molluscan assemblages in Argentinean Patagonia, covering ~1800 km along the Patagonian Continental Shelf (PCS) (Figure 1; Supplementary material S1). Because there are no previous studies on this topic in this area at these depths, and, even hemispherically, most data come from the Northern Hemisphere (Mondal et al ., 2021), this work aims to improve the knowledge of this type of biotic interaction in southern South America where the little information available is restricted to the intertidal to subtidal coastal environments as mentioned before.

Figure 1.Map of the study area showing the sampling sites (stations 1–19).

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“…Previous studies on this topic reveal that predation pressure may decrease or increase with increasing latitude, or even show no trend, questioning the generality of any large-scale latitudinal or biogeographic pattern (e.g. Vermeij et al ., 1989; Hansen and Kelley, 1995; Alexander and Dietl, 2001; Hoffmeister and Kowalewski, 2001; Visaggi and Kelley, 2015; Mondal et al ., 2021). In southern South America, this issue has been previously treated by Martinelli et al .…”