Different evolutionary responses to selection could explain the observed morphological distinction.
Many studies correlate environmental gradients with variation in salmonid life history and morphological traits, suggesting that diversity in these traits reflects adaptive evolutionary responses to local selective pressures (Brannon et al. 1981; Taylor 1990; Quinn and Buck 2001; Quinn 2005).
Morphological traits, such as size and shape, may reflect a combination of ecological and evolutionary responses by organisms.
Discovering genes that control morphological, behavioural and physiological phenotypes is critical for understanding adaptive evolution, for plant and animal breeding and for tracking the evolutionary responses of natural populations, such as insecticide resistance in crop pests.
Parmesan, C. Ecological and evolutionary responses to recent climate change.
Strauss, S. Y. Ecological and evolutionary responses in complex communities: implications for invasions and eco-evolutionary feedbacks.
These are adaptive, evolutionary responses.
Why frogs might exhibit conservative morphological evolutionary patterns is not clear.
Both ammonoid lineages display empirical morphological evolutionary trends of some shell characters.
They observed rapid evolutionary responses to culling.
