Microevoluonary Response in Lower Mississippian Camerate Crinoids to Predatory Pressures Jeffrey R Thompson, The Ohio State University [email protected]

Preliminary Data

Intraspecific Variability of Convexity in Agaricocrinus •Intraspecific variability in Introducon Agaricocrinus americanus (Fig. Crinoids were relavely unaffected by the end-Devonian Hangenberg event, but the major clades of Devonian durophagous fishes suffered significant exncons. These americanus 4), Agaricocrinus crassus (Fig. dominant Devonian fishes were bing or nipping predators. In response to the Hangenberg event, Lower Mississippian crinoids underwent an adapve radiaon, while 0.012 5) and Dorycrinus unicornis fish clades with a shell-crushing durophagous strategy emerged. Durophagous predators were more effecve predators on camerate crinoids and it is hypothesized that 0.01 central spines (Fig. 6) through the Lower Mississippian, camerate crinoids evolved more effecve an-predatory strategies in order to compensate for the more effecve predatory strategy of •It is necessary to determine the durophagous fishes. More convex plates and longer spines are commonly regarded to provide more effecve an-predatory strategies. Did convexity and spinosity 0.008 intraspecific variability to increase among camerate crinoids during the Lower Mississippian? A new method was formulated to test for an increase in convexity of the calyx plates among species determine whether variaon in of 2 different genera, Agaricocrinus and Aorocrinus. Spine length was analyzed in the genus Dorycrinus and was a simple linear measurement. Data are analyzed using a 0.006 plate convexity and spine runs test to determine if morphological change is stascally significant of represents a random walk. Change in plate convexity and spine length in different species is 0.004 length is between species or representave of microevoluonary change as new species evolve to changing ecological condions. between individuals Hypothesis: In the Mississippian period of geologic me, crinoid plate convexity will increase in different species through me. Convexity in pixels 0.002 •Once intraspecific variability is 0 determined, error bars may be Individuals set on further stascal analyses at the species level Fig. 4 Methods •A new method to determine convexity has been designed to assign a numerical Intraspecific Variability of Plate Convexity in value to the convexity of morphological characteriscs. This method was applied to Agaricocrinus crassus the calcite plates that make up the skeletons of the crinoids to assign a numerical 0.012 value to the convexity of these plates. •First images are edited in preparaon for algorithm. See Fig. 1 0.01

Figure 3: Curve of Best Fit for Modeled Plate 0.008

0.006

0.004 Convexity in pixels 0.002

0 From louisvillefossils.blogspot.com Individuals Fig. 5 •Spine length is a simple linear measure determined with Intraspecific Variability in Spine Length of Dorycrinus calipers unicornis 16 Modeled Height in pixels 14

12

10

Modeled Width in pixels 8

•Algorithm is then used to model plate of specimens. Fig. 2 and Fig. 3 6

I=SM86; 4 c=1252;

Figure 2: Modeled Crinoid Plate Central Spine Length in mm r=1009; Fig. 5 2 xEnd = 1681; 0 xValues = []; Individuals From crinoids.com yValues = []; T=[12 0 0]; Fig. 6 i = 1; while (xEnd>=c) j=0; Q=impixel(I,c,r+j); Future work while (Q(1) > T(1)) Much data must sll be refined from image format to numerical format. Once this is done, intraspecific variability of plate convexity will be determined Q=impixel(I,c,r+j); for Agaricocrinus. When intraspecific variability has been determined, change in different species through me will be examined using a runs test to if Q(1)<=T(1) determine whether trends exist or are random. Similar tests will be performed on the genus Aorocrinus to determine if trends in convexity exist in this xValues(i) = c; genus as well. Spine length in Dorycrinus will then be examined with a runs test to examine morphological trends through the Lower Mississippian. yValues(i) = r; Change in plate convexity in different species is representave of microevoluonary change as new species evolve to changing ecological condions. else Sallan et al. (2011) proposed a macroevoluonary change at the genus level in camerate crinoids through the Mississippian period and, if such a link j = j + 1; occurs at the species level, it will suggest a connecon between microevoluon and macroevoluon, which is quesoned by those (Gould, 2002) who

end Modeled Height in pixels envision a hierarchy in evoluonary processes. end r = r + j - 25; Acknowledgements c = c + 1; I would like to thank Shell for the funding of the research this summer as well as the OSU URO for the funding during the school year. Addionally, Wendy Panero and Alex Rytel have i = i + 1; Modeled Width in pixels provided invaluable assisance with Matlab. Finally I would like to thank Anne Carey for the opportunity to parcipate in the SURE program end References Gould S.J., 2002, The Structure of Evoluonary Theory, Harvard University Press, Cambridge, Massachusses, 1433 p. Sallan, L.C., Kammer T.W., Ausich W.I., and Cook L.A., 2011 Persistent Predator-Prey Dynamics Revealed by Mass Exncon p. 8335-8338. Proceedings of the Naonal Academy of Science, vol. 108, no. 20