Evolutionary trends within bivalve prey of chesapeake group naticid gastropods

Abstract

Five genera of Miocene bivalves evolved antipredatory adaptations in response to predation by drilling naticid gastropods. I examined the evolution of two traits affecting predator-prey interaction, prey shell thickness (TH) and internal volume (IV). Thickness controls predation costs by determining drilling time, and internal volume influences the benefit derived by the predator.Internal volume showed no consistent pattern of temporal change among the taxa studied. IV fluctuated nondirectionally during the history of most genera, though both increasing and decreasing trends occurred within species of Astarte. In contrast, all five genera exhibited significant thickness increases (from 8-157%) during the three-million-year interval. Both gradual intraspecific and interspecific directional changes occurred. Taxa with the greatest predation intensities displayed the most change, suggesting that predation selected for the thickness increases. Increased thickness apparently reduced predation; a significant negative correlation between TH and predation intensity occurred within four of the bivalve genera. Improvement of predator capabilities apparently did not keep pace with increased antipredatory morphologic adaptations over the interval studied.

Shell ornamentation as a likely exaptation: evidence from predatory drilling on Cenozoic bivalves

“…studied here, were present since at least the Triassic for this lineage (McRoberts and Blodgett 2000;Yin and McRoberts 2006). Conversely, drilling frequencies were generally low in the Neoproterozoic, Paleozoic, and Mesozoic, but were higher in the Late Cretaceous-Cenozoic (Vermeij 1987;Kelley andHansen 1993, 2003;Kowalewski et al 1998;Huntley and Kowalewski 2007). Ishikawa and Kase (2007) used absence of a temporal trend, among other reasons, as an argument that conchiolin layers were an exaptation to drilling predation.…”

“…5), as might be expected given the greater overall shell thickness on ribs. Greatly thickened bivalve shells are known to inhibit drilling (e.g., Vermeij 1978), and Kelley (1989) reported that increases in shell thickness in several Miocene bivalves correlated with decreases in successful drilling and increases in prey effectiveness. Addition of ribs provides a costeffective means of increasing apparent shell thickness when drill holes are placed on ribs (see e.g.…”

Treatise Online no. 44: Part N, Revised, Volume 1, Chapter 22: Predation of bivalves

“…DE angElis, KitchEll, and post (1985) argued, based on modeling, that increasing shell thickness should be an evolutionary strategy of bivalves experiencing naticid gastropod predation. Such thickening of the shell was reported by KEllEy (1989KEllEy ( , 1991 and KEllEy and hansEn (2001) for several Eocene and Miocene bivalve lineages of the United States Coastal Plain in response to naticid predation. harpEr and sKElton (1993a) noted that taxa with thicker shells generally employ shell microstructures, such as foliated calcite and crossed lamellar aragonite, that are known to be low in organic matrix and consequently may be cheaper to secrete (palMEr, 1992); such microstructures, although mechanically weaker in terms of resistance to bending, impact resistance, and compression, are harder, and crossed-lamellar structures may be more resistant to abrasion (taylor & layMan, 1972).…”

“…Successful attacks by naticids, in which the prey suffocated during drilling, may yield incomplete holes (see ansEll & Morton, 1987, for a laboratory example), and when multiple muricids attack a prey simultaneously, they may abandon a partially completed hole once the prey is breached and feed through the gape (taylor & Morton, 1996). Nonetheless, study of drillhole size and positioning and also success rate, and in particular changes in them over geological time, has indicated evolution of particular behavioral traits on the part of the predator (e.g., selectivity of prey species or size and drillhole site on the prey; KEllEy, 1988KEllEy, , 1989KEllEy & hansEn, 1996b) …”

Comparative drilling predation on time-averaged phosphatized and nonphosphatized assemblages of the minute clypeasteroid echinoidEchinocyamus stellatusfrom Miocene offshore sediments (Globigerina Limestone Formation, Malta)

“…The geological deep-time record has revealed that drilling predation can be used as a tool to recognize ecological interactions in both fossil and extant communities (e.g., Kelley, 1989;Kowalewski et al, 1998;Harper, 2003). Drilling frequencies have increased over time (e.g., Huntley and Kowalewski, 2007) and thus represent a useful proxy for a better understanding of the development of ecological interactions through time (e.g., Bengtson and Zhao, 1992;Conway Morris and Bengtson, 1994;Kowalewski et al, 1998;Kowalewski et al, 2005).…”