Brigitte Marazzi, Dr.
Postdoctoral researcher Mike Sanderson Lab Department of Ecology and Evolutionary Biology University of Arizona Tucson, USA Tel. (001)520-626-7860 Office BSE 125
bmarazzi[at]email.arizona.edu

RESEARCH INTERESTS

My research interests cover topics in botany and macroevolution, addressing questions like: How did morphological diversity of extant plants evolve? How is it characterized? What are the evolutionary processes that led to it? Did species traits such as morphological novelties have influenced lineage diversification? This means to ultimately increase our understanding of why some taxonomic groups are remarkably more diverse than related groups, which is one of the central questions in evolutionary biology.

Specifically, my current research focuses on the large, widespread, and diverse genus Senna (Leguminosae, Caesalpinioideae, Cassiinae) to explore the evolution of plant morphological novelties and key innovations. I am also highly interested in character specialization and character complexes, especially at the floral morphological level.

Senna Miller (formerly included in Cassia L.) is characterized by the presence of extrafloral nectaries in numerous species and a distinctive floral morphology, it displays a high diversity of habits (Fig. 1), and has successfully colonized a wide range of habitats in different climates and latitudes. Of the 300-350 species currently ascribed to the genus, 80% occur in the Americas [1]. Since long time, some species are used for their medicinal properties (especially as a purge) and are appreciated as ornamentals, owing to their showy yellow flowers [2, 3].

Fig. 1 Diversity of habits in Senna. © B. Marazzi.

Current Project

Evolutionary Role of Extrafloral Nectaries (EFNs)

EFNs are secretory structures attracting ants and forming a protective opportunistic ant-plant interaction or mutualism [4] in some ferns and in over 90 angiosperm families, notably in the legume family [5, 6]. In Senna, EFNs are typically found on leaves (Fig. 2) and rarely also on pedicels. Species with EFNs form a large strongly supported clade within Senna, the ‘EFN clade’ (see Marazzi et al. 2006a), and EFNs seem thus to represent a morphological novelty in the genus, raising interesting questions on their evolutionary role:

Are EFNs a key innovation in plant defense strategies?

Key innovations are one of the most important triggers of large-scale diversifications and radiations in nature explaining unusual disparities between clades [7]. The observation of a conspicuous clade size difference between the ‘EFN clade’ and its sister clade lacking EFNs and the available ecological evidence of EFNs (and mutualism) to increase plant fitness, suggest that the EFNs have played a key role in the large-scale diversification of Senna (Marazzi et al. 2006a). It is the primary aim of my current project in Mike Sanderson’s Lab (see lab webpage at http://loco.biosci.arizona.edu/) to test the hypotheses whether EFNs are a key innovation in Senna, in particular, and in angiosperms, in general.

Fig. 2 Examples of EFNs in Senna. © B. Marazzi.

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LOOKING FOR A RESEARCH PROJECT FOR YOUR MASTER STUDIES AT UofA?

If yes, several research subjects are available as part of my project on EFNs. They address fundamental questions on the ecological role, anatomy and morphology, and evolution of extrafloral nectaries in Senna. Fall 2008 and Fall 2009. Some projects may include field work. For questions and more information please email me.

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Other Projects

Floral Character Specialization and Character Complexes

Flowers of Senna are structurally highly diverse (Fig. 3), and have been the focus of my doctoral studies with Prof. Peter K. Endress (University of Zurich, Switzerland). They display an array of traits typically related to buzz pollination (i.e. bees vibrate the stamens to extract and collect the pollen [8]), such as poricidal anther dehiscence with unusual, long and tubular anther tips in some species, heteranthery with up to four different kinds of stamens and seven different kinds of heterantherous androecia, and point-tipped stigmas (Marazzi et al. 2007). This outstanding diversity makes the androecium of Senna an ideal example to illustrate the specializations that buzz flowers have undergone in conjunction with their pollination mode. Many species are further characterized by asymmetric, enantiostylous flowers, in which the entire carpel is deflected to the left or right (Fig. 3).

Asymmetric flowers are rare in angiosperms [9]. In Senna, floral asymmetry is complex: up to five floral organs out of three floral whorls (corolla, androecium, and gynoecium) directly affect the floral symmetry and form, in different combinations, up to five floral asymmetry patterns (Marazzi and Endress 2008). The presence of both species with monosymmetric and many diverse asymmetric flowers makes Senna an ideal group to study the evolution of floral asymmetry and character complexes.

Future work is aimed at reconstructing the evolution of floral structural specialization and floral asymmetry in Senna, testing also hypotheses of character state correlations to understand the multiple origins of highly asymmetric flowers.

Fig. 3 Diversity of flowers in Senna. © B. Marazzi.

Ongoing Collaborations

· Molecular Systematics of subtribe Cassiinae (Leguminosae)

By Adilva Souza and Luciano Paganucci de Queiroz, Universidade Estadual de Feira de Santana, Herbario HUEFS, Feira de Santana, Bahia, Brazil.

*** Literature cited is at the very end of the webpage ***

CURRICULUM VITAE

Education
Mar. 2007 Oct. 2002 1997-2002	Dr. sc. nat., University of Zurich, Zurich, Switzerland. Dipl. Syst. Bot. (MSc.), University of Zurich, Zurich, Switzerland. Studies in Biology (Systematic Botany as main subject at Institute of Systematic Botany, Environmental Sciences at Institute of Environmental Sciences, and Geobotany at ETH Zurich), University of Zurich, Zurich, Switzerland.
Research Experience
Nov. 2007-today Sept.-Oct. 2007 Feb.-Aug. 2007 2002-2007 2001-2002	Postdoctoral studies funded by the Swiss National Science Foundation, with Prof. Dr. Michael J. Sanderson, Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, USA. Short postdoctoral studies with Prof. Dr. Hans-Peter Linder, Institute of Systematic Botany (ISB), University of Zurich, Zurich, Switzerland. Project: Completation of the Danthonoideae (Poaceae) image database in DELTA (DEscription Language for TAxonomy). Postdoctoral studies with Prof. Dr. Peter K. Endress, ISB, University of Zurich, Zurich, Switzerland. Project: Reconstruction of the evolution of floral asymmetry in Senna. Doctoral thesis, “Molecular systematics and structure, development and evolution of floral asymmetry in the genus Senna (Leguminosae)”. Supervised by Prof. Dr. Peter K. Endress and co-supervised by Prof. Dr. Elena Conti, ISB, University of Zurich, Zurich, Switzerland. Diploma thesis (MSc.), “Senna (Leguminosae, Cassiinae) in the Flora of Paraguay”. Supervised by Prof. Dr. Rodolphe Spichiger, Conservatoire et Jardin Botaniques de la ville de Genève (CJB), Geneva, and Prof. Dr. Peter K. Endress, Institute of Systematic Botany, University of Zurich, Zurich, Switzerland.
Grants and Fellowships
2007-2009 2006 2004 2003 2002 2001	Postdoctoral fellowship of the Swiss National Science Foundation (nr. PBZHA-118849; for a 1.5-year research period with Prof. Michael J. Sanderson at the University of Arizona, Tucson, Arizona, USA). Travel grant by Schweizerische Akademie der Naturwissenschaften (SANW/SCNAT+) (for collecting trips in 2006-2007 in Bolivia). Travel grant by Georges-und-Antoine-Claraz-Schenkung (for collecting trips in 2005 in NE-Argentina and give a talk at the IBONE, Argentina). Travel grant by SANW/SCNAT+ (for collecting trips in 2004 in Brazil). Travel grant by Claraz-Schenkung (for the two extensive collecting trips during 2003 in SE-Paraguay, NW-Argentina, Panama and Mexico). Travel grant by Claraz-Schenkung (for the collecting trips in N- and NE-Argentina).
Awards
2006 2004	Katherine Esau Award (outstanding paper in developmental and structural botany at the annual meeting of ABLS, AFS, ASPT and BSA, Chico, California, USA). Poster award at the symposium “Challenges in Plant Science”, Zurich, Switzerland.
Reviewer
Plant Biosystems (formerly "Giornale Botanico Italiano") (1) Plant Systematics and Evolution (2)

NB: For the complete CV email to bmarazzi[at]email.arizona.edu

PUBLICATIONS

Research Publications

Marazzi, B., P. K. Endress (2008) Patterns and development of floral asymmetry in Senna (Leguminosae, Cassiinae). American Journal of Botany 95: 22-40.

Marazzi, B., E. Conti, P. K. Endress (2007) Diversity of anthers and stigmas in the buzz-pollinated genus Senna (Leguminosae, Cassiinae). International Journal of Plant Science 168: 371-391.

Marazzi, B., P. K. Endress, L. Paganucci de Queiroz, E. Conti (2006a) Phylogenetic relationships within Senna (Leguminosae, Cassiinae) based on three chloroplast regions: patterns in the evolution of floral symmetry and extrafloral nectaries. American Journal Botany 93: 288-303.

Marazzi, B., R. Fortunato, P. K. Endress, R. Spichiger (2006b) Senna (Cassiinae, Leguminosae) in Paraguay: synopsis, conservation, ecologic role and ethnobotany. Candollea 61: 315-329.

NB: For PDFs of articles email to bmarazzi[at]email.arizona.edu

Abstracts

Marazzi, B., M.J. Sanderson (2008) Large-scale diversification of Senna (Leguminosae) in the American continent. Botany 2008 Congress (Annual meeting of ABLS, AFS, ASPT and BSA), Vancouver, Canada. Oral presentation abstract.

Marazzi, B., P. K. Endress (2007) Diversity, development and evolution of asymmetric flowers in Senna (Leguminosae). Botanikertagung 2007 (Annual meeting of the German Society of Botany), Hamburg, Germany. Poster abstract.

Marazzi, B., P. K. Endress (2007) Diversity, development and evolution of asymmetric flowers in Senna (Leguminosae). Abstract volume of the Botany 2007 Congress (Annual meeting of ABLS, AFS, ASPT and BSA), Chicago, Illinois, USA. Oral presentation abstract ID 999.

Marazzi, B., E. Conti, P. K. Endress (2006) Evolution of floral diversity in the buzz-pollinated genus Senna (Leguminosae, Cassiinae). Abstract volume of the Botany 2006 Congress (Annual meeting of ABLS, AFS, ASPT and BSA), Chico, California, USA. Oral presentation abstract ID119.

Marazzi, B., E. Conti, L. Paganucci de Queiroz, P. K. Endress (2005) Asymmetric flowers and phylogeny in Senna (Leguminosae, Cassiinae). Symposium of the Zurich-Basel Plant Science Center, Zurich, Switzerland. Poster abstract.

Marazzi, B., E. Conti, L. Paganucci de Queiroz, P. K. Endress (2005) Asymmetric flowers and phylogeny in Senna (Leguminosae, Cassiinae). Abstract volume of the XVII International Botanical Congress, Vienna, Austria. Poster abstract P0472, p. 314.

Marazzi, B., P. K. Endress, E. Conti (2004) Phylogeny and evolution of asymmetric flowers in Senna (Leguminosae, Cassiinae). Symposium “Challenges in Plant Science” in Zurich, Switzerland. Poster abstract. Winner of a poster award.

Marazzi, B., P. K. Endress, E. Conti (2004) Phylogeny and evolution of asymmetric flowers in Senna (Leguminosae, Cassiinae). Abstract volume of the Botany 2004 Congress (Annual meeting of ABLS, AFS, ASPT and BSA), Snowbird, Utah, USA. Poster Abstract ID207, p. 53.

Literature cited

[1] Irwin HS, RC Barneby 1982 Mem New York Bot Gard 35: 1-918.

[2] Colladon TF 1816 Histoire naturelle et médicale des casses[…]. Jean Martel, Montpellier.

[3] Luckow M 1996 Baileya 23: 195-241.

[4] Heil M, D McKey 2003 Annu Rev Ecol Evol Syst 34: 425-453.

[5] Koptur S 1992 Pages 81-129 in E Bernays (Ed.) Insect-plant interactions, volume IV. CRC Press, London.

[6] McKey D 1989 Pages 673–718 in CH Stirton, JL Zarucchi, eds. Advances in legume biology. Monogr Syst Bot Mo Bot Gard 29.

[7] Sanderson MJ, MJ Donoghue 1994 Science 264: 1590-1593.

[8] Buchmann SL 1983 Pages 73-113 in CE Jones, RJ Little, eds. Handbook of experimental pollination biology. Scientific and Academic Editions, New York.

[9] Endress PK 1999 Int J Plant Sci 160 (Suppl, 6):S3-S23.

Last updated: 6 Aug 2008 - Copyright Brigitte Marazzi.