Research Interests
My current research interests stem from my desire to understand fundamental aspects of biological diversity. These fundamental aspects include the relationships of organisms and their morphological complexity. I study these aspects using phylogenetic systematics, geometric morphometrics and other tools. These tools allow us to understand broader themes such as historical biogeography, molecular evolution, conservation and the evolution of morphological diversity. As an ichthyologist, my focus is on process oriented evolutionary biology in marine fishes and pattern oriented evolutionary biology in freshwater fishes. As a systematist, I use molecular and morphological tools to help discover relationships among species and resolve taxonomy in order to better understand the evolutionary history of a taxon.
My most recent research focuses on understanding the phylogenetic and biogeographic relationships of freshwater fishes from Middle America (Central America, Mexico, Greater Antillean Islands) and on the phylogenetic and evolutionary history of deep-sea fishes in the Gulf of Mexico and the Indo-West Pacific. I am also conducting studies of blind cave fishes of Gondwanan origin and bioluminescent fishes from the deep ocean.
Deep-Sea Fish Systematics
Part of my current research focus is to resolve some of the difficult phylogenetic problems associated with bioluminescent and deep-sea fishes. In recent years I have focused on the Indo-Pacific family of ponyfishes (Leiognathidae; with collaborator John Sparks, AMNH) and on deep-sea forms including batfishes and tripod fishes (with Hans Ho and my postdoctoral fellow Matthew Davis). Many deep-sea fishes are bioluminescent and co-opt the light produced by bacteria for sexually dimorphic photic communication. By resolving the relationships among these fishes we can better understand how this ability may have influenced their evolutionary history (e.g. increased speciation rates or morphological disparity). My lab is also currently resolving the many taxonomic problems that plague these group using molecular, morphological and behavioral (flashing) characters in phylogenetic analyses. Much of this work is associated with the products of recent field trips to Vietnam, Madagascar, Sri Lanka, Indonesia, the Malay Peninsula and Taiwan. The phylogenies being prepared for these families will be used to revise the taxonomy of these group, identify new species, and test hypotheses about the role of sexual selection and photic communication on morphological diversity and species richness.
Recent Systematics Publications:
-Sparks, J.S., Chakrabarty, P. (2007) A new species of ponyfish (Teleostei:Leiognathidae: Photoplagios) from the Philippines. Copeia 2007 (3): 622-629.
-Chakrabarty, P., Sparks, J.S. (2008) Diagnoses for Leiognathus Lacepède 1802, Equula Cuvier 1815, Equulites Fowler 1904, Eubleekeria Fowler 1904, and a new ponyfish genus (Teleostei: Leiognathidae). American Museum Novitates 3623, 1-11.
Biogeography
I am also currently interested in the historical biogeography of Neotropical fishes. I hope to better understand the biogeographic relationships of Greater Antillean, Middle and South American fishes. One of the great unknowns in biogeographic studies is the origin of the fauna of the Greater Antillean islands and the four different geological blocks that have united to form Central America. I found evidence through phylogenetic analysis that the origin of some of the freshwater ichthyofauna is linked to ancient vicariance events. Vicariance was favored over alternatives because both the pattern of the recovered phylogeny and divergence time estimates were congruent with this hypothesis. I continue testing these hypotheses and several large-scale phylogenies that include a much broader sampling of taxa including fossils. The relationships of each of these groups are unique but all of them can potentially test biogeographic patterns for the region through phylogenetic analyses.
Recent Biogeography Publications:
-Chakrabarty, P. (2004) Cichlid biogeography: comment and review. Fish and Fisheries 5(2): 97-119.
-Chakrabarty, P. (2006) Systematics and Historical Biogeography of Greater Antillean Cichlidae. Molecular Phylogenetics and Evolution 39, 619-627.
Geometric Morphometrics And Analyses of Disparity
I have done a number of projects measuring and comparing morphological diversity as it is distributed among groups. I used geometric morphometric techniques and analyses of disparity to test hypotheses about morphological evolution in several fish clades. Hypotheses about the origins of various groups can often be tested by quantifying morphological diversity. I researched how African Rift Lake cichlid taxa differ in morphological diversity relative to species richness and ecological diversity. Researchers in the past have tied the rich diversity of these cichlids to different evolutionary hypotheses (e.g., microallopatric speciation, sympatric speciation). Some of these evolutionary hypotheses were based on assumptions made about the morphological diversity of some cichlid clades. I quantified morphological diversity to test these hypotheses. I am currently researching how this geometric tool can be used to test other hypotheses pertaining to morphological diversity; including the correlation between branch length on a molecular phylogeny and conservative or extreme morphologies.
Recent GM Publications:
-Chakrabarty, P. (2005) Testing conjectures about morphological diversity in cichlids of Lakes Malawi and Tanganyika. Copeia 2005 (2): 259-273.
- Chakrabarty, P., Chu, J., Luthfun, N., and Sparks, J.S. (2010) Geometric morphometrics uncovers an undescribed ponyfish (Teleostei: Leiognathidae: Equulites) with a note on the taxonomic status of Equula berbis Valenciennes. Zootaxa 2427:15-24.
Taxonomy and Morphological Studies
Morphological character analyses are essential in phylogenetics and descriptive work to ensure proper diagnoses, taxonomy and rigorous sampling of all phylogentically informative material. As a collections based scientist I will always continue to have morphological systematics as a major part of my research program. Phylogenies that include morphological characters lead to the discovery of morphological synapomorphies that can be used in descriptive works diagnosing novel taxa or higher groups. Another important use of morphological work is in the use of fossil calibrations in molecular studies. Calibrations based on fossil taxa are widely used to age different nodes in molecular phylogenies. Unfortunately, these fossils are often incorrectly placed on the molecular phylogeny because of the lack of any morphological data from extant taxa in the character matrix. More rigorous and robust conclusions about phylogenies can only be made with the use of morphological data.
Recent Morphological Publications:
-Chakrabarty, P. (2006) Taxonomic status of the Hispaniolan Cichlidae. Occasional Papers of the Museum of Zoology, University of Michigan 737: 1 – 16.
-Chakrabarty, P. (2007) A morphological phylogenetic analysis of Middle American cichlids with special emphasis on the section "Nandopsis"; sensu Regan. Miscellaneous Publications, Museum of Zoology, University of Michigan 198: 1-31.
-Chakrabarty, P., Sparks, J.S. (2007) Phylogeny and taxonomic revision of Nuchequula Whitley 1932 (Teleostei: Leiognathidae), with the description of a new species. American Museum Novitates 3588:1-28.
-Smith, W.L., Chakrabarty, P., Sparks, J.S., (2008) Phylogeny, taxonomy and evolution of South American cichlids (Percomorpha: Cichlidae: Cichlinae). Cladistics 24, 1-17.
