Multivariate Identification of Morphological-Environmental Relationships within the Cyprinidae (Pisces)

Abstract

The usefulness of two types of morphological character sets for predicting habitat use in cyprinids was tested. Two sets of morphological characters thought to be related to habitat use were defined, including a) an a priori set, derived from previous studies of functional morphology and morphological-environmental associations, in various species groups, and b) an a posteriori set, based on morphological-environmental relationships revealed by factor analysis for a subgroup of cyprinids. Environmental variables were regressed onto relevant morphological characters in both sets, to generate values of habitat use predicted by morphology. Prediction of habitat use was judged successful if actual and predicted habitat use were significantly correlated in a second subgroup of cyprinids. No successful predictors of habitat use were found among a priori designated characters. Factor analysis showed several significant associations: fin sizes and placements were predictive of preferred position in the water column; gut pigmentation, intestine length and cerebellum size predicted relative herbivory or predaceousness. Other associations shown by factor analysis were interpretable but not predictive, and related morphology to preference for vegetation and for different substrate types. The failure of a priori designated characters to predict habitat use may be due to inadequate measures of resource use. Another reason may be that eco-morphological relationships demonstrated for one species group cannot be directly extrapolated to species that do not share that group's evolutionary history.