Ontogeny and Functional Morphology
How does natural selection shape the size and maturity of newborn offspring? How does growth rate influence the acquisition of adult morphology? Do developmental programs constrain form and function? These questions sit at the intersection of functional morphology, developmental biology and life history evolution, and are the basis for the research and teaching presented below.
Dial, T.R. and Lauder, G.V. 2020. Longer development provides first-feeding fish time to escape hydrodynamic constraints. Journal of Morphology 281(8): 956-969. DOI: 10.1002/jmor.21224
Dial, T.R., Reznick, D.N. and Brainerd, E.L. 2017. Heterochrony in the evolution of offspring size: maturation along a uniform ontogenetic trajectory. Proceedings of the Royal Society B 20171319.
Dial, T.R., Hernandez, L.P. and Brainerd, E.L. 2017. Morphological and functional maturity of the oral jaw covaries with offspring size in Trinidadian guppies. Scientific Reports 7:5771 1-10 (DIO:10.1038/s41598-017-06414-6).
Dial, T.R., Reznick, D.N. and Brainerd, E.L. 2016. Effects of neonatal size on maturity and escape performance in the Trinidadian guppy. Functional Ecology 30:943–952 (DOI:10.1111/1365-2435.12565).
Dial, T.R. and Carrier, D.R. 2012. Precocial hindlimbs and altricial forelimbs: the partitioning of ontogenetic strategies in mallards (Anas platyrhynchos). Journal of Experimental Biology 215: 3703-3710 (doi:10.1242/jeb.057380).
Dial, T.R., Heers, A.M. and Tobalske, B.W. 2012. Ontogeny of aerodynamics in mallards: comparative performance and developmental implications. Journal of Experimental Biology 215: 3693-3702 (doi:10.1242/jeb.062018).
Dial, K.P., Randall R.J. and Dial, T.R. 2006. What use is half a wing in the ecology and evolution of birds? BioScience 56: 437-445.
Matthews, D.G., Reznick, D.N. and Relative effects of genetics and plasticity in benthic-limnetic morphological divergences of Trinidadian guppies. (in prep)
Dial, K.P., Heers, A.M. and Dial, T.R. 2015. Ontogenetic and evolutionary transformations in avian locomotion: the ecological significance of incipient structures. In: K.P. Dial, N.H. Shubin, E.L. Brainerd (eds.), Great Transformations in Vertebrate Evolution. University of Chicago Press, Chicago.
Developmental constraints and allowances
Biomechanical and hydrodynamic constraints of the feeding mechanism of larval fish, but hatching at a premature developmental stage or with underdeveloped feeding apparatus could be a limitation too. Using high-speed videography (2000 frames per second) and optical illumination of tiny (4 µm) particles for flow reconstruction (PIV), colleagues and I deliver challenging hydrodynamic manipulations (by increasing water viscosity) in the lab to tease apart the relative effects of size and development in first-feeding fishes. The work has led to a novel hypothesis suggesting that organismal performance is largely a product of degree of maturation, rather than size alone (Dial and Lauder 2020).
Local adaptation and repeatability of evolution
In collaboration with Dave Matthews (graduate student in Lauder lab, Harvard Univ.) we've been investigating 3D craniofacial morphology in wild Trinidadian guppy populations adapted to either benthic (bottom-dwelling) or limnetic (water-column) diets. The project is designed to determine population-level differences in head and mouth shape of fish adapted to different diets and the repeatability of those adaptions across independent streams. We are finding that adaptive head shapes in derived benthic populations converge at a gross anatomical level, but through modification of different skeletal elements, which suggests that there is not one anatomical (and therefore genetic) solution to the problem of benthic foraging (Matthews and Dial, in prep). The next step is to investigate how these different head shapes develop, particularly in response to alternate diet types.
Ontogeny of flow refuging behavior in Rainbow trout
As an angler I have always been fascinated by the hydrodynamic environment of riparian habitat – an environment that for the entire life of resident fish is constantly flowing by them and churning over structures of the riverbed. How fish negotiate this turbulence is of profound intellectual interest as well as conservation value. In order to address how and why fish positioning occurs where it does along the length of the river, collaborators (Universities of Florida and Montana) and I quantified the swimming behavior of rainbow trout refuging within a range of eddy sizes, which are backward flowing regions of water where fish are able to escape the fast free-stream water velocity (Figure 4). In addition, we collected flow field data and were able to show that trout preference for refuging depends on the size and nature of that refuge – preference to swim in reduced flow does not always equal capacity to capitalize if the flow regime does not support the biomechanics of swimming. This study is applicable to the design of fish ladders (diversions through which migrating fish must successfully pass to breach dams) and which have on the order of single-digit percentage passage success for anadromous fishes, such as the steelhead, sturgeon or lamprey. Further directions seek to expand this research question to other fish species, test fish over a greater range of flow speeds and increase the complexity of turbulence, in an effort to get at more real-world picture of natural flow regimes and more relevant fish behavior and biomechanics.