Biodiversity Studies: Plant Systematics and Evolution
“Biodiversity” includes the diversity of taxa and their traits. How did this diversity come about? Does the diversity represent a range of “solutions” that deal with the “problem” of living? What are these problems and what are the solutions? Answers to these questions represent understanding of the history of biodiversity.
Understanding this history entails two things: understanding the historical paths of change (what happened, when?) and understanding the underlying processes (what factors are behind such changes?).
My research is focussed on tracing historical paths of biological diversification My goal is to integrate understanding of multiple processes (developmental, morphogenetic, physiological) at multiple levels (molecular, cellular, organismal) to obtain a comprehensive understanding of evolving biological systems (plants). This work involves the marriage of multiple disciplines, e.g., “traditional” botany and “modern” molecular genetics and, critically, phylogenetics (reconstruction of evolutionary relationships among taxa and using the phylogenetic framework to analyse data from many species) — “Phylogenetic Biology“.
The taxonomic scope of this work includes monocotyledons, Dioscorea, Crotalaria, Impatiens, Rhododendron, Moringa and fungi; phylogenetic and developmental studies use both molecular and morphological data. My collaborators and I have studied developmental and evolutionary patterns of variation in characters at different levels of organization: morphological (leaf development and evolution), cellular (reproductive development), subcellular (relocalization of duplicate proteins), genomic (nuclear DNA amount and phenotypic correlates), and molecular (Knox, a homeobox multigene family) and through integrative phylogenetic analyses. Our studies have also extended into evolutionary ecology and historical analysis (presence of Datura in Asia).
Research in my lab has included investigations of phylogenetic systematics and biochemical, morphological evolution and biogeography in Dioscorea (true yams), Justicia, Impatiens and Moringa.
I do not have a laboratory now, but continue my interest in plants and their history.
- Berry E, Geeta R. Floral morphs of Justicia adhatoda L. differ in fruit and seed, but not floral, traits or pollinator visitation. Journal of Biooscience. 10.1007/s12038-021-00159-1 2021.
- Chaudhary K, Geeta R, Panjabi, P. Origin and diversification of ECERIFERUM1 (CER1) and ECERIFERUM3 (CER3) genes in land plants and phylogenetic evidence that the ancestral CER1/3 gene resulted from the fusion of pre-existing domains. Molecular Phylogenetics and Evolution 159: 107101. https://www.sciencedirect.com/science/article/abs/pii/S1055790321000348. 2021.
- Geeta R, Berry E. Floral symmetry — what it is, how it forms, and why it varies. Chapter 7, pp 131-155. In: R. Tandon, KR Savanna, Monika Koul (eds.). Reproductive Ecology of Flowering Plants: Patterns and Processes, Springer Nature, Singapore. 2020.
- Singh S, Geeta R, Das S. Comparative sequence analysis across Brassicaceae, regulatory diversity in KCS5 and KCS6 homologs from Arabidopsis thaliana and Brassica juncea, and intronic fragment as a negative transcriptional regulator. Gene Expression Patterns 38:119146. https://doi.org/10.1016/j.gep.2020.119146. 2020.
- Berry E, Choudhary AK, Mishra G, Tandon R, Geeta, R. Justicia adhatoda reveals two morphotypes with possible functional significance. Journal of Plant Research https://doi.org/10.1007/s10265-020-01224-w. 2020.
- Phukela B, Geeta R, Das S, Tandon R. Ancestral segmental duplication in Solanaceae is responsible for the origin of CRCa–CRCb paralogues in the family. Molecular Genetics and Genomics https://doi.org/10.1007/s00438-019-01641-0. 2020.
- Geeta R. Communicating science to college students and the general public. Indian Journal of Genetics, 79(1) Suppl. 367-368. 2019.
- Berry E, Geeta R. Floral Morphology of Rhododendron and its Relation with Pollinators. Rhododendron International 3: 82-97. 2019.
- Singh S, Das S, Geeta R. A segmental duplication in the common ancestor of Brassicaceae is responsible for the origin of the paralogs KCS6–KCS5, which are not shared with other angiosperms. Molecular Phylogenetics and Evolution 126: 331-345. 2018.
- Barman P, Bhat KV, Geeta R. Phylogenetic analysis of Indian Dioscorea and comparison of secondary metabolite content with sampling across the tree. Genetic Resources and Crop Evolution 65: 1003-1012. 2018.
- Berry E, Sharma SK, Pandit MK, Geeta R. Evolutionary correlation between floral monosymmetry and corolla pigmentation patterns in Rhododendron. Plant Systematics and Evolution 304: 219-230. 2018.DOI 10.1007/s00606-017-1467-y. 2018.
- Singh S, Das S, Geeta R. Role of Cuticular Wax in Adaptation to Abiotic Stress: A Molecular Perspective. Abiotic Stress-Mediated Sensing and Signaling in Plants: An Omics Perspective. 155-182. Springer, Singapore. 2018.
- Barman P, Choudhary AK, Geeta R. A modified protocol yields high quality RNA from highly mucilaginous Dioscorea tubers. 3 Biotech (2017) 7: 150. https://doi.org/10.1007/s13205-017-0775-9. 2017.
- Rathore P, Geeta R, Das S. Microsynteny and phylogenetic analysis of tandemly organised miRNA families across five members of Brassicaceae reveals complex retention and loss history. Plant Science 247:35-48. 2016.
- Gholami A, Subramaniam S, Geeta R, Pandey AK. Molecular systematics of Indian Alysicarpus (Fabaceae) based on analyses of nuclear ribosomal DNA sequences. Journal of Genetics 96: 353-363. DOI 10.1007/s12041-017-0785-8. 2017.
- Geeta R. KNOX genes and shoot development in angiosperms: old actors in new roles? Phytomorphology 66: 57-69. 2016.
- Puri R, Barman P, Geeta R. 2016. A phylogenetic approach toward the understanding of disjunct distributions of plant taxa in Western Ghats and northeastern India. Rheedea 26:17-32. 2016
- Geeta R, Lohmann LG, Magallón S, Faith DP, Hendry A, Crandall K, De Meester L, Webb C, Prieur-Richard A-H, Mimura M, Conti E, Cracraft J, Forest F, Jaramillo C, Donoghue M and Yahara T. Biodiversity only makes sense in the light of evolution. J. Biosci. 39 doi/10.1007/s12038-014-9427-y. 2014
- Sharma R, Geeta R, Bhat V. Male/Female gametophyte development in facultative apomictic plants of Cenchrus ciliaris (Poaceae) is asynchronous. S Afr. J. Bot. 91:19-31. 2014.
- Subramaniam S, Pandey AK, Geeta R, Mort ME. Molecular systematics of Indian Crotalaria (Fabaceae) based on analyses of nuclear ribosomal ITS DNA sequences. Plant Systematics and Evolution. DOI 10.1007/s00606=013-0781-2. 2013.
- Geeta R, Davalos LM, Levy A. et al. Keeping it simple: flowering plants tend to retain, and revert to, simple leaves. New Phytologist 193: 481-493. DOI: 10.1111/j.1469-8137.2011.03951.x 2012
- Vencl F, Trillo P, Geeta R. Functional interactions among tortoise beetle larval defenses reveal trait suites and escalation. Behav Ecol Sociobiol 64: DOI 10.1007/s00265-010-1031-z. 2010.
- Mignouna H, Abang MM, Asiedu R and Geeta R. Dioscorea, true yams – A biological and evolutionary link between eudicots and grasses. In Emerging Model Organisms. Cold Spring Harbor Laboratory Press. doi:10.1101/pdb.emo136. 2009.
- Geeta R and Gharaibeh W. Historical evidence for a pre-Columbian presence of Datura in the Old World and implications for a first millenium transfer from the New World. J. Biosci. 32: 1227-1244. 2007.
- Champagne CEM, Goliber TE, Wojciechowski MF, Mei RW, Townsley BT, Wang K, Paz MW, Geeta R and Sinha NR. 2007. Compound Leaf Development and Evolution in the Legumes. Plant Cell 19 3369-3378. 2007
- Byun-McKay SA and Geeta R. Protein subcellular relocalization: a new perspective on the origin of novel genes. Trends Ecol. Evol. 22:338-344. 2007.
- Tellez VO and Geeta R. Dioscorea howardiana, a new species in section Trigonobasis (Dioscoreaceae). Brittonia 59: 370-373. 2007.
- Murali TS, Suryanarayanan TS, Geeta R. Endophytic Phomopsis species: host range and implications for diversity estimates. Can J. Microbiol 52: 673-680. 2006.
- Geeta R. Structure trees, species trees: What they say about morphological development and evolution. Evol. Dev. 5: 609-621. 2003.
- Geeta R. Variation and diversification in plant evo-devo (book review). Amer. J. Bot. 90: 1257-1261. 2003.
- Geeta R. The origin and maintenance of nuclear endosperms: Viewing development through a phylogenetic lens. Proc. R. Soc. B. 270: 29-35. 2003.
- Hjortswang HI, Larsson AS, Bharathan G, Bozhkov PV, Von Arnold S, and Vahala T KNOTTED1-like homeobox genes of a gymnosperm, Norway spruce, expressed during somatic embryogenesis. Plant Physiol. Biochem. 40: 837-843. 2002.
- Bharathan G, Goliber T, Moore C, Kessler S, Pham T and Sinha N. Homologies in leaf development inferred from KNOXI gene expression. Science 296: 1858-1860. 2002.
- Bharathan G and Sinha NR. The Regulation of Compound Leaf Development. Plant Physiol. 127: 1533-1538. 2001.
- Bharathan G, Janssen B-J, Kellogg EA, and Sinha N. Phylogenetic relationships and evolution of the KNOTTED class of plant homeodomain proteins. Mol. Biol. Evol. 16: 553-563. 1999.
- Goliber T, Kessler S, Chen J-J, Bharathan G, and Sinha N. Genetic, molecular, and morphological analysis of compound leaf development. Invited review in R. A. Pederson and G. Schatten [ed.]. Current Topics in Developmental Biology, Vol 43:259-290. Academic Press. 1998.
- Bharathan G, Janssen B.-J, Kellogg EA, and Sinha N. Did homeodomain proteins duplicate before the origin of angiosperms, fungi , and metazoa? Proc. Natl. Acad. Sci. 94:13749-13753. 1997.
- Bharathan G. Does the monocot mode of leaf development characterize all monocots?” Aliso 14:271-279. 1996.
- Bharathan G. “Reproductive development and nuclear DNA content in angiosperms. Amer. J. Bot. 83:440-451. 1996.
- Bharathan G and Zimmer EA. Early branching events in monocotyledons — partial 18S ribosomal DNA sequence analysis. In P. J. Rudall, P. J. Cribb, D. F. Cutler and C. J. Humphries [ed.], Monocotyledons — systematics and evolution, Vol. I, 81-108. Royal Botanic Gardens, Kew. 1995.
- Bharathan G, Lambert G, and Galbraith DW. Nuclear DNA content of monocotyledons and related taxa. Amer. J. Bot. 81:381-386. 1994.
- Sanderson MJ, Baldwin BG, Bharathan G, Campbell CS, von Dohlen C, Ferguson D, Porter JM, Wojciechowski MF, and Donoghue MJ. The growth of phylogenetic information, and the need for a phylogenetic data base. Syst. Biol. 42:562-568. 1993.
- Sanderson MJ and Bharathan G. Does cladistic information affect inferences about branching rates? Syst. Biol. 42:1-17. 1993.