Major professional aims and interests
I have a life-long fascination with the complexity and diversity of biological shapes in animals, which range from relatively simple to the most intricate forms. My main interest is to study the mechanistic principles of biological shape changes during evolution. As all animal shapes arise through the developmental process, it is critical to understand the relationship between evolution and development. Intellectually, I am a disciple of Karl von Baer, D’Arcy Thompson, Ivan Schmalhausen, C.H. Waddington, Stephen J. Gould and Pere Alberch, who all believed that a successful exploration of many evolutionary phenomena relies on the deeper understanding of the connection between the phylogeny and ontogeny and learning the principles upon which the organisms are constructed during individual development. In modern developmental evolution field research,
I distinguish three distinct but highly interdependent components:

(i) morphometrics to reveal the kind and direction of morphological change within a given phylogeny,
(ii) identification of candidate mechanisms that correlate with evolutionary changes, and

(iii) functional experiments which causally link developmental changes with morphological transitions.
In my own work, I take a cross-disciplinary and highly collaborative approach that integrates the three evo-devo research components and combines advances from disparate fields, such as phylogenetics, genomics, paleontology, morphometrics, cell biology, and developmental genetics to gain mechanistic understanding of morphogenesis and evolutionary processes that generate morphological variation.

A combination of geometric morphometrics, comparative molecular embryology and functional experimentation methods helps us address many important evolutionary questions and groups of organisms (central diagram from Mallarino and Abzhanov, 2012). My projects on non-model species follow this scheme and they are in different stage of progression from morphological studies (blue) to identification of associated candidate developmental mechanisms (orange) to their experimental testing (green). My major devo-evo projects are several diverse groups of vertebrates: 1) Darwin’s Finches and tanager relatives, 2) Hawaiian Honeycreepers’ beak diversity; 3) non-avian to avian dinosaur large-scale transition; 4) skull diversification and dimorphism in anole lizards; and 5) diverse faces of phyllostomid bat ecomorphs.
The principal focus for my studies is on the vertebrate face and head. Vertebrate head is the most complex part of the body and cranial diversity in vertebrates is an inviting and challenging research topic as animal crania show many unique and adaptive features which reflect their natural history. Most of the head diversity depends on the shapes and sizes of the bones and cartilages that make up the cranial skeleton. Thus, studies on craniofacial skeletal development in “model” (laboratory-bred species) and “non-model” (wild species) animals are fundamental to understanding mechanisms that generated cranial diversity during vertebrate evolution and continue to generate morphological variation today. They are also critical to the advancement of future diagnoses and treatments of human craniofacial disorders. Even though many of the species I study cannot be established in the laboratory, they remain extremely important “natural experiments” and should be explored mechanistically.
My group studies non-model organisms to understand how morphological evolution arose under natural conditions and selective pressures, and I use model organisms to study the underlying developmental principles and to functionally test roles of candidate genes identified in comparative studies. The main reason for my studying multiple non-model species in parallel is to recognize common principles and mechanisms as different taxa can give insights into different aspects of the great puzzle of adaptive evolution that I wish to understand.