Trophic niche separation in sympatric rocky shore crabs

Abstract

Where two species occupy the same habitat and similar niches, competition is likely to drive small-scale spatial niche separation or resource partitioning that may not be immediately apparent. A stable isotope approach was used to investigate potential trophic niche separation between co-existing rocky shore crabs in the North-West (NW) Arabian Gulf. Leptodius exaratus and Pilumnopeus convexus which occupy similar shore height on the same rocky intertidal habitats. We also investigated conspecific differences between males vs females and adults vs juveniles. δ15N results indicated that adults of both species occupy a high trophic level in the rocky shore community, suggesting similar functional roles and potential for competition for food resources, while significant differences in δ13C values indicated differences in dietary sources between the two species, and also changes in diet between juveniles and adults in both species. MixSIAR analysis of δ15N and δ13C data confirmed field observations that both species are generalist omnivores, with potential for direct competition including adult predation on juveniles, including conspecifics. Differentiation in isotopic niches (SIBER analysis) was mainly driven by the significant differences in δ13C values, suggesting that co-existence of the two crab species is at least in part mediated by trophic niche separation or dietary resource partitioning, with some (unquantified) potential for spatial resource partitioning at the microhabitat level.

Range extension of invasive Cancer irroratus and native Carcinus maenas polewards in the Ascophyllum-dominated intertidal zone in north-west Iceland

“…A study by Einarsson (1988) indicates that H. araneus can be found everywhere from 2 m down to depths of 60 m all around Iceland, but it should be noted that any study before 2006 did not account for what effects C. irroratus might have on the native species. In other instances, co-existence of crab species in the same habitat and with similar niches have led to competitive exclusion or to changes in diet (Al-Wazzan et al ., 2019). A possible explanation for the differences in distribution and abundances in the subtidal and the intertidal zones is that, intertidally, H. araneus has a different niche foraging under the Ascophyllum cover, making it easier for larger populations to be sustained – the exception being sites where C. maenas is found in large numbers, which may lead to a competitive displacement of H. araneus .…”

Life History Parameters and Fishing Aspects of the Alien Nimble Spray Crab Percnon gibbesi in a Native Area of the Central-East Atlantic

“…Some studies have shown that crabs in benthic ecosystems often act as keystone species [ 18 , 19 , 20 ]. Many of these species are omnivorous, controlling the growth of algal species and small invertebrates, or recycling organic matter [ 21 , 22 ], so their lack or overexploitation can give rise to trophic cascades [ 16 ].…”