Kathleen K. Smith, Professor  

Kathleen K. Smith

My current work is a focus on the relation between evolution and development in the mammalian skull. My model system involves comparisons of development in placental and marsupial mammals. These mammals are characterized by different developmental trajectories, extending back to some of the earliest events of differentiation, largely as a result of their different life history adaptations. My work focuses on a number of different questions. First, what are the differences in the development of the craniofacial region in marsupial and placental mammals? The head is particularly important in the comparison between marupials and placentals, as many cranial systems must be functional at birth in marsupials, despite the fact that morphogenesis has just started. Second, how do the differences in the developmental pattern reflect the necessities of the marsupial reproductive strategy? What is the adaptive significance of the developmental differences and what constraints might be operating? Here I am looking at development not as merely a means to produce an adult, but as a feature that has an evolutionary significance of its own. Third, what can this comparative approach tell us about mammalian head development in general? There are many differences in the way the head develops in marsupials and placentals. It is reasonable to assume that those elements that develop independently (e.g., appear in different temporal or spatial sequences in the two taxa) are elements that are not mechanistically linked or integrated, whereas those that are consistently associated in the two taxa, despite changes in other structures, may be linked by developmental mechanisms. I am using this comparative approach to examine developmental integration and plasticity. Fourth, what are the developmental mechanisms underlying these evolutionary changes? The most significant differences in development in the two taxa reflect differences in the relative timing of the development of the central nervous system and somatic structures. Hypotheses on many levels have been proposed on the possible mechanistic relations between the development of the CNS and the cranial skeleton. To what extent can these hypotheses on mechanistic relation be tested by comparing events in organisms in which the elements are shifted dramatically in time or space? The comparison is, in essence, a natural experiment. Finally, have the specific developmental patterns of marsupial and placental mammals had an impact on the evolutionary diversity and success of these organisms?

My current project focuses on the earliest patterning events. These projects include a study of heterochronies in the earliest morphological and genetic events in the head of marsupial and placental mammals, a study of neural crest in marupial mammals, and a study of patterns of Hox gene expression along the developing body axis, relations between the brain and cranial skeleton.

Ph.D., Harvard University, 1980
B.A., University of California at Santa Cruz, 1973

Office Location: 130 Science Drive, Room 122 Duke Box 90338, Durham, NC 27708
Office Phone: (919) 684-3402
Email Address: kksmith@duke.edu
Web Page: http://people.duke.edu/~kksmith/

Organismal Biology and Behavior
Developmental Biology

Research Categories: Functional morphology and evolution of vertebrates; craniofacial development, evolutionary morphology

Research Description: I am interested in the functional and evolutionary morphology of vertebrates. My research has included the functional and phylogenetic significance of variations in form of craniofacial structures in squamate reptiles and mammals, the biomechanics of a class of structures called musculohydrostats, and the roles of adaptive evolution and constraint in morphological diversification. My current focus is on the relation between evolutionary and developmental processes, with particular focus on the evolutionary, functional and developmental consequences of heterochronies in the morphogenesis of cranial nerves, muscles, bones and sensory structures in eutherian and metatherian mammals.

I have shown that one of the most fundamental differences between the two taxa is a delay in marsupials of the development of the central nervous system (CNS) and cranial sense organs and an advancement of certain cranial skeletal-muscular tissues. Specifically, in marsupials the central nervous system and particularly the forebrain is delayed relative to the development of the bones around the oral apparatus, the chondrocranium and the differentiation of cranial muscles. Currently my work is focused on the timing and pattern of early neural crest migration in marsupials. In recent years I have demonstrated that neural crest differentiates and migrates earlier in marsupials, relative to neural tube or somite differentiation, than in another other vertebrate thus far reported. I am now focusing on the patterns of expression of major genes thought to impose regional identity on the neural crest and neural tube.

In addition I am looking at the phylogenetic context of these heterochronies, with a comparative study of early development in therian mammals, monotremes, and non-mammalian amniotes in order to identify the primitive developmental condition for mammals.

Recent Publications   (More Publications)   (search)

  1. Adamski, KN; Loyd, AM; Samost, A; Myers, B; Nightingale, R; Smith, K; 'Dale' Bass, CR, Pediatric Coronal Suture Fiber Alignment and the Effect of Interdigitation on Coronal Suture Mechanical Properties., Annals of Biomedical Engineering, vol. 43 no. 9 (September, 2015), pp. 2101-2111 [doi]  [abs].
  2. Smith, KK, Placental Evolution in Therian Mammals, in Great Transformations in Vertebrate Evolution, edited by Dial, KP; Shubin, N; Brainerd, EL (July, 2015), pp. 205-225, University of Chicago Press .
  3. Keyte, AL; Smith, KK, Heterochrony and developmental timing mechanisms: changing ontogenies in evolution., Seminars in Cell and Developmental Biology, vol. 34 (October, 2014), pp. 99-107 [doi]  [abs].
  4. Keyte, AL; Smith, KK, Heterochrony and developmental timing mechanisms: Changing ontogenies in evolution, Seminars in Cell and Developmental Biology, vol. 34 (January, 2014), pp. 99-107 [doi]  [abs].
  5. K.K. Smith, THE PLACENTA IN THERIAN MAMMALS: NEW VIEWS ON THE MARSUPIAL PLACENTAL DICHOTOMY, in Great Transformations in Vertebrate Evolution., edited by Dial, Ken, Shubin, Neil, Brainerd, Elizabeth (2014), University of California Press (this was an invited chapter and was peer reviewed..) .