COMBINING INDEPENDENT SOURCES OF DATA TO INVESTIGATE PATTERNS OF MORPHOSPACE OCCUPATION THROUGH TIME : AN EXAMPLE USING PALEOZOIC TEREBRATULIDE BRACHIOPOD GENERA

Significant or directional changes in morphology through time have been detected in several clades. This suggests that emergent or aggregate ecological traits that provide a survivorship advantage to one species or clade over another may covary with morphology. Without explicit investigations into these potentially important ecological traits, the description of morphological change through time is purely phenomenological. Here, I describe the pattern of morphospace occupation through the Paleozoic for a clade of articulated brachiopods, the Terebratulida. I then provide evidence suggesting that several aggregate and emergent ecological properties frequently associated with increased survivorship are not randomly dispersed in the empirical terebratulide morphospace, and that evolutionary processes acting on these traits may give rise to long-term patterns in morphospace occupation through time.

Throughout the Paleozoic, times of increasing terebratulide generic diversity are concordant with increases in the amount of morphospace occupied, whereas times of decreasing generic diversity are concordant with reductions in morphospace occupation. Extinctions, however, are not strictly biased against peripheral regions of morphospace. To determine if, and how, morphospace occupation patterns covary with emergent or aggregate ecological characteristics, I compared the position of the genera in morphospace with three variables: 1) the number of discrete latitudinal bands occupied by the genus, 2) whether the genus is tropically restricted or pandemic, and 3) the number of unique documented occurrence records for the genus. Paleozoic terebratulide genera with large geographic ranges and many occurrence records occupy centralized regions of morphospace. Strictly tropical genera with smaller geographic range sizes and few occurrence records, however, are not restricted to the periphery of morphospace, but are more evenly dispersed in morphospace.