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Variation in Gastropod Borehole Frequency Within the same species from similar paleoenvironmental settings The authors thank the Albert and Alice Weeks.

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Presentation on theme: "Variation in Gastropod Borehole Frequency Within the same species from similar paleoenvironmental settings The authors thank the Albert and Alice Weeks."— Presentation transcript:

1 Variation in Gastropod Borehole Frequency Within the same species from similar paleoenvironmental settings The authors thank the Albert and Alice Weeks Post-Doctoral Fellowship (University of Wisconsin-Madison) for supporting this research. Gwen M. Daley & Daniella Gatti Winthrop University Dana Geary University of Wisconsin-Madison Summer Ostrowski Michigan State University Andrew Bush University of Connecticut

2 We previously reported that higher predatory gastropod boring frequencies were found in the formation (Bermont or Fort Thompson) in which Chione elevata, Carditamera floridana and Anadara transversa were more abundant in samples from the Caloosa Shell Quarry. Introduction Prey size and predator size (outer borehole diameter) Relative prey size and boring frequencies Relative abundance and boring frequencies Five additional species were analyzed to examine correlations between:

3 1 m Section #3 Caloosa Shell Quarry Near Ruskin, Florida Ft. Thompson Fm. Bermont Fm.

4 Bermont Formation (Pleistocene) Ft. Thompson Formation (Pleistocene) Paleoecology: Primarily sand-loving nestling bivalves and gastropods with grass and rubble dwellers. Paleoenvironment: Shallow subtidal sand with grass patches. Paleoecology: Primarily grass-loving nestling bivalves and gastropods with sand and rubble dwellers. Paleoenvironment: Shallow subtidal grass-covered sand.

5 +++ = 2 kg sieves 2 kg Collection Processing Chione elevata Carditamera floridana Anadara transversa Mulinia lateralis Transennella stimpsoni Parvilucina multilineata Lucina nassula Corbula contracta Countable Specimens Countable Specimens

6 Transennella stimpsoni 1 cm Mulinia lateralis Lucina nassula Corbula contracta Parvilucina multilineata Anadara transversa Chione elevata Carditamera floridana Median Size and Per-Sample Abundance of Prey Species Green =Ft. Thompson Blue = Bermont

7 Chione elevata Carditamera floridana Anadara transversa Shallow burrowing siphonate suspension feeder Byssate* shallow burrowing suspension feeder Byssate shallow burrowing suspension feeder VeneridaeCarditidae Arcidae sea grass root

8 Mulinia lateralis Transennella stimpsoni Corbula contracta Opportunistic, R-selected Shallow burrowing siphonate suspension feeder Shallow burrowing siphonate suspension feeder Shallow burrowing siphonate suspension feeder MactridaeVeneridaeCorbulidae sea grass root

9 Lucina nassula Parvilucina multilineata Shallow burrowing siphonate lucinid suspension/deposit feeder Lucinidae sea grass root Shallow burrowing siphonate lucinid suspension/deposit feeder

10 Shell Length (cm) Outer Borehole Diameter (cm) Ft. Thompson Bermont Prey Size versus Predator Size Proxy for Predator Size

11 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Chione elevata Outer Borehole Diameter (cm) Proxy for Predator Size

12 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Carditamera floridana Outer Borehole Diameter (cm) Proxy for Predator Size

13 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Transennella stimpsoni Outer Borehole Diameter (cm) Proxy for Predator Size

14 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Mulinia lateralis Outer Borehole Diameter (cm) Proxy for Predator Size

15 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Lucina nassula Outer Borehole Diameter (cm) Proxy for Predator Size

16 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Corbula contracta Outer Borehole Diameter (cm) Proxy for Predator Size

17 Prey Size versus Predator Size Shell Length (cm) Ft. Thompson Bermont Size of shell figures indicate median size of all whole valves in formation Parvilucina multilineata Outer Borehole Diameter (cm) Proxy for Predator Size

18 Potential Prey Size versus Boring Frequency Median Shell Length (cm) Boring Frequency (%)

19 [Difference in Boring Frequencies between Formations] [Difference in Median Shell Length Between Formations (cm)] R=0.799 Difference in Potential Prey Size vs. Difference in Boring Frequency Shell color indicates formation in which that species is more abundant

20 Average Sample Size (Whole Valves) Boring Frequency (All Whole Valves in Formation) Average Sample Size versus Boring Frequency Higher boring frequency when less abundant: 4 Lower boring frequency when less abundant: 2

21 [Difference in Average Sample Size Between Formations] [Difference in Boring Frequencies between Formations] R=0.513 Difference in Boring Frequency vs. Average Sample Size Difference Shell color indicates formation in which that species is more abundant

22 Conclusions For these eight species of clam prey from the Bermont and Fort Thompson Formations: There was no correlation between median shell size of potential prey species and boring frequency, but a positive trend when the differences between formations was analyzed. Significantly higher boring frequencies were found in the formation with lower abundance in half of the species. A quarter of the species had significantly lower boring frequencies in the formation with lower abundance. Two species had no significant differences. The differences between boring frequencies and abundance between formations was positively correlated.

23 Median Shell Length versus Average Sample Size Average Sample Size Median Shell Length (cm) R=.726 Smaller shell size when more abundant: 2 Larger shell size when more abundant: 4

24 Difference in Average Sample Size Between Formations Difference in Median Shell Length Between Formations R=0.463 Difference in Median Shell Length vs. Average Sample Size Difference Shell color indicates formation in which that species is more abundant


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