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RESEARCH

Ecology and evolution of mutualisms

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Cooperation among species has long been a hurdle for Darwinian natural selection. Theory predicts that mutualists frequently turns into parasites and exploit their partner. Shifts to parasitism appear to be rare empirically, and thus whether cheating is an important selective force in mutualism is hotly debated. Moreover, recent data has shown that it least in some systems, freeloaders outside of the mutualisms (phylogenetically unrelated) are frequent. My work on mutualisms aims to address several questions: (i) When and how mutualism specialise, and what are the implication of mutualism specialisation? (ii) When do mutualisms breakdown? and (iii) How do mutualism vary at a global scale, and how this knowledge help understand global biodiversity patterns and tailor more efficient conservation strategies? To address these questions, I use several systems: ant/plant symbioses, notably a group of c. 100 species of Australasian epiphytic Rubiaceae (Hydnophytinae), and I focus all experimental work on a subclass of 9 species that encompass facultative and obligate ant-plants. Secondly, I use all major mutualisms to address macroevolutionary and macroecological questions. This includes ant/plant defense mutualisms, pollination mutualisms, dispersal mutualisms, coral/zooxanthelae symbioses, lichens, mycorrhiza, nitrogen-fixing plants/Rhizobia and more. My experimental work includes a great deal of field ecology, but also transcriptomics and metabolomics and CT scanning, while my macroevolutionary work involves essentially database building and phylogenetic comparative methods.

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Related publications:

 

Gutiérrez-Valencia J., Chomicki G. and Renner S.S. (2017). Recurrent breakdowns of mutualisms with ant in the neotropical ant-plant genus Cecropia (Urticaceae). Molecular Phylogenetics and Evolution 111: 196–205. Link.

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Chomicki G., Renner S.S. (2017). Partner abundance controls mutualism stability and the pace of morphological change over geologic time. Proceedings of the National Academy of Sciences of the USA 114: 3951-3956. Link.

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Chomicki G., Renner S.S. (2017). The interactions of ants with their biotic environment. Proceedings of the Royal Society of London B: Biological Sciences 284: 20170013. Link. Part of aspecial issue on ‘Ants in their biotic environment’ that I am co-editing with Susanne Renner. Introduction to the special issue (review article).

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Chomicki G., Janda M., Renner S.S. (2017). The assembly of ant-farmed gardens: mutualism specialization via host broadening. Proceedings of the Royal Society of London B: Biological Sciences 284: 20161759. Link

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Chomicki G., Renner S.S. (2016). Obligate plant farming by a specialized ant. Nature Plants 2: 16181. Link

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Chomicki G., Staedler Y., Schönenberger J., Renner S.S. (2016). Partner choice through concealed floral sugar rewards evolved with the specialization of ant/plant mutualisms. New Phytologist 211 (4): 1358-1370. Link See the commentary by Judith Bronstein

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Chomicki G., Renner S.S. (2016). Evolutionary relationships and history of the ant-epiphytic genus Squamalleria (Rubiaceae: Psychotrieae) and their taxonomic implications. PLoS ONE 11(3): e0151317. Link

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Chomicki G., Ward P.S., Renner S.S. (2015). Macroevolutionary assembly of ant/plant symbioses: Pseudomyrmex ants and their ant-housing plants in the Neotropics. Proceedings of the Royal Society of London B: Biological Sciences 282 (1819): 20152200 Link

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Chomicki G., Renner S.S. (2015). Phylogenetics and molecular clocks reveal the repeated evolution of ant-plants after the late Miocene in Africa and the early Miocene in Australasia and the Neotropics. New Phytologist 207(2): 411-424. Link

 

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Macroevolution

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Understanding why species are unevenly distributed across space and across the tree of life are major questions in biology, and a thorough understanding of these questions is essential for conserving biodiversity. I am convinced that answers to these questions can only be sought through multi-faceted approaches integrating taxonomy, phylogeny, palaeontology, genomics, interaction data, trait data, georeferenced data, and sometimes geological data altogether in a comparative framework. So far I have used orchids to investigate plant diversification along an altitudinal gradient. Because orchids are globally distributed, and includes several fast radiations, they are a very interesting group to address questions about biodiversity patterns. My interest in macroevolution intersects with my mutualism research, in particular because I feel that species interactions, and mutualism in particular, have not yet been well integrated in biodiversity theory. My research in this area involves comparative methods, phylogenomics, and database building, but taxonomy is always first key step, including species description.

 

Related publications:

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Renner S.S., Sousa A., Chomicki G. Chromosome numbers, Sudanese gourds and classification of the watermelon genus Citrullus, with 60 names allocated to seven biological species. Taxon. In press.

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Perez-Escobar O.A., Chomicki G., Condamine F.L., de Vos J.M., Martins A.C., Smidt E., Klitgaard B.B., Gerlach G., Heinrichs J. (2017). Multiple geographical origins of environmental sex determination enhanced the diversification of Darwin's favourite orchids. Scientific Reports 7: 12878. Link.

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Perez-Escobar O.A., Gottschling M., Chomicki G., Condamine F.L., Klitgård B., Pansarin E., Gerlach G. (2017). Andean mountain building did not preclude dispersal of lowland epiphytic orchids in the Neotropics. Scientific Reports 7: 4919. Link.

 

Perez O.A.§, Chomicki G.§*, Condamine F.L., Matzke N.J., Silvestro D., Antonelli A. (2017). Recent origin and rapid speciation of Neotropical orchids in the world’s richest plant biodiversity hotspot. New Phytologist 215: 891–905. Link.

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Chomicki G., Renner S.S. (2016). Evolutionary relationships and history of the ant-epiphytic genus Squamalleria (Rubiaceae: Psychotrieae) and their taxonomic implications. PLoS ONE 11(3): e0151317. Link

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Renner S.S., Chomicki G., Greuter W. (2014). Proposal to conserve Momordica lanata, the basionym of Citrullus lanatus (watermelon, Cucurbitaceae), with a conserved type and against an earlier synonym. Taxon 63(4): 941-942. Link

Origin and evolution of agriculture

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The gradual shift from hunting and gathering to plant cultivation and animal husbandry started globally at the boundary between the end of the Pleistocene and the beginning of the Holocene some 12,000-11,000 years ago, and is one of the most important transition in human history, allowing the development of our modern cultures. But agriculture has evolved much earlier in several lineages across the tree of life. Primitive farming mutualisms are found in amoeba, fungus or deep-sea crab that cultivate bacteria, and damselfish, or sloth farming algae. The most advance agricultures, sharing a number of aspects with our human agriculture includes fungiculture by ants, termites and ambrosia beetles. I discovered the first specialised farming of plants by ants. I am interested in the convergences between human and non-human agriculture and work specifically in two areas: the origin and domestication of the watermelon and related crops in the Cucurbitaceae genus Citrullus, and plant farming by ants, including generalist ant-gardens and highly specialised Fijian farming symbioses involving the ant Philidris nagasau that farm Squamellaria. I use taxonomy, ancient DNA analysis and phylogenomics to decipher the origin and domestication of crops in Citrullus, and field ecology, phylogenies, metabolomics and transcriptomics to dissect the evolution and functioning of ant/plant farming mutualism.

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Related publications:

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Renner S.S., Sousa A., Chomicki G. Chromosome numbers, Sudanese gourds and classification of the watermelon genus Citrullus, with 60 names allocated to seven biological species. Taxon. In press.

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Chomicki G., Janda M., Renner S.S. (2017). The assembly of ant-farmed gardens: mutualism specialization via host broadening. Proceedings of the Royal Society of London B: Biological Sciences 284: 20161759. Link

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Chomicki G., Renner S.S. (2016). Obligate plant farming by a specialized ant. Nature Plants 2: 16181. Link

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Chomicki G., Renner S.S. (2015). Watermelon origin solved with molecular phylogenetics including Linnaean material: another example of museomics. New Phytologist 205(2): 526-532. Link 

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Renner S.S., Chomicki G., Greuter W. (2014). Proposal to conserve Momordica lanata, the basionym of Citrullus lanatus (watermelon, Cucurbitaceae), with a conserved type and against an earlier synonym. Taxon 63(4): 941-942. Link

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Evolution of morphology

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Morphology is often uncorrelated with relatedness with related species sometimes looking entirely different and species far apart looking the same. While the genetic basis of morphological novelty is becoming increasingly well understood, the rules governing morphological change at a macroevolutionary level are not well characterised. I have argued that shifts in mutualism strategies, such as specialisation or breakdown, are important drivers of morphology in interaction-related traits. My work on the evolution of morphology is twofold. First, I am interested in the evolution of plant morphology, and in particular plant architecture. Second I am interested to develop a coherent framework to understand morphological evolution at a macro-level. This involves a mix of morphological and anatomical work, functional morphology, CT-scanning, architectural analysis, together with comparative methods.

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Related publications:

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Chomicki G., Coiro M., Renner S.S. (2017). Evolution and ecology of plant architecture: integrating insights from the fossil record, extant morphology, developmental genetics, and phylogenies. Annals of Botany. In press. Invited Review.

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Perez-Escobar O.A., Chomicki G., Condamine F.L., de Vos J.M., Martins A.C., Smidt E., Klitgaard B.B., Gerlach G., Heinrichs J. (2017). Multiple geographical origins of environmental sex determination enhanced the diversification of Darwin's favourite orchids. Scientific Reports 7: 12878. Link.

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Sauquet H., von Balthazar M., Magallón S., Doyle J.A., Endress P.K., Bailes E.J., de Morais E.B., Bull-Hereñu K., Carrive L., Chartier M., Chomicki G., Coiro M., Cornette R., El Ottra J.H.L., Epicoco C., Foster C.S.P., Jabbour F., Haevermans A., Haevermans T., Hernández R., Little S.A., Löfstrand S., Luna J.A., Massoni J., Nadot S., Pamperl S., Prieu C., Reyes E., dos Santos P., Schoonderwoerd K.M., Sontag S., Soulebeau A., Städler Y., Tschan G.F., Wing-Sze Leung A., Schönenberger J. (2017). The ancestral flower of angiosperms and its early diversification. Nature Communications 8: 16047. Link.

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Chomicki G., Renner S.S. (2017). Partner abundance controls mutualism stability and the pace of morphological change over geologic time. Proceedings of the National Academy of Sciences of the USA 114: 3951-3956. Link.

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Chomicki G., Staedler Y., Schönenberger J., Renner S.S. (2016). Partner choice through concealed floral sugar rewards evolved with the specialization of ant/plant mutualisms. New Phytologist 211: 1358-1370. Link See the commentary by Judith Bronstein

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Chomicki G., Bidel L.P.R., Ming F., Coiro M., Zhang X., Wang Y., Baissac Y., Jay-Allemand C., Renner S.S. (2015). The velamen protects photosynthetic orchid roots against UV-B damage, and a large dated phylogeny implies multiple gains and losses of this function during the Cenozoic. New Phytologist 205: 1330-1341. Link

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Chomicki G., Bidel L.P.R., Baker,W. J., Jay-Allemand C. (2014). Palm snorkelling: leaf bases as aeration structures in the mangrove palm (Nypa fruticans). Botanical Journal of the Linnean Society 174: 257-270. Link

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Chomicki G., Bidel L.P.R., Jay-Allemand C. (2014). Exodermis structure controls fungal invasion in the leafless epiphytic orchid Dendrophylax lindenii (Lindl.) Benth. ex Rolfe. Flora 209: 89-94. Link

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