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My Science work
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Me and my students and co-workers study biodiversity, biogeography, ecology, and evolution in South and Middle America using fish (focusing on cichlids) as our model group. Field work forms the foundation of our studies and Phylogenetic analyses form the backbone of our research. New species are routinely being discovered and described. We use up-to-date methods including phylogenomic methods based on NGS technologies, like ddRAD sequencing.
Field expeditions
(only Neotropics listed):
Several years worth of cummulative field work in South and Middle America in the last 24 years in 33 expeditions (2002-2026) into 13 Neotropical countries: 7x Ecuador, 6x Brazil, 5x Argentina, 5x Peru, 5x Mexico, 4x Venezuela, 4x Colombia, 2x Paraguay, Bolivia, Cuba, Costa Rica, Nicaragua, Panama.
Professional impact:
Contributed to systematics of 50 genera and 209 species (Eschmeyer's Catalog of Fishes, 2023).
Discoverer and author (so far, 2003-2025) of 11 genera new to science and 20 species new to science.
One new species dedicated name (Australoheros ricani) as regognition of impact on the field of study.
Collected virtually all species of Neotropical cichlids including around 100 putativelly new species.
Discoverer of several adaptive radiations of Neotropical cichlids in island-like settings (Island biogeography paradigm); e.g. Middle American cichlids, Parallel adaptive radiations in Crenicichla.
Author of developmental theory explaining evolution (and identification of homologous structures) of coloration patterns in cichlid fishes that was confirmed experimentally.
Reviewed diversity and explained evolution of the historically most complex group of Neotropical cichlids (the Middle American cichlids).
Was at the forefront of innovation of research of Neotropical cichlid systematics and evolution with phylogenetics and molecular data, the latter in all three phases, from mtDNA, through nDNA, to NGS genomics.
Most prolific Czech systematic ichthyologist.
Leader in the field of Neotropical cichlid evolutionary biology and systematics and most influential Neotropical cichlid systematist in this century (most species studied, most new species discovered, most new genera and species named).
My Science projects:
Species and Genus diversity of cichlids in the Neotropics
The understanding of biodiversity comes through the understanding of systematics of a given group, which is the now completely overlooked and absolutely underfunded (in Europe at least) cornerstone of biodiversity research and biology in general. The largest part of my studies are primarily systematic papers. Systematics and hence diversity is still incompletely known for Neotropical fishes in general and for cichlids in particular as also my own research demonstrates; 20 new discovered and described species and 11 new genera, with many additional awaiting publication (there are over 50 in Crenicichla and 25 in Bujurquina, for example).
Example study: Piálek L, Dragová K, Casciotta J, Almirón A, Říčan O (2015) Description of two new species of Crenicichla (Teleostei: Cichlidae) from the lower Iguazú River with a taxonomic reappraisal of C. iguassuensis, C. tesay and C. yaha. Historia Natural 5: 5-27.
Figure: Live specimens of the four sympatric species from the Iguazú River.
(A,B) Crenicichla tesay.
(C,D) Crenicichla iguassuensis.
(E,F) Crenicichla tapii sp. n. (E, male; F, female).
(G,H) Crenicichla tuca sp. n. (both male).
Phylogenetic relationships of cichlids in the Neotropics
Phylogeny and phylogenetic analysis is the cornerstone of evolutionary biology and its main analytical and interpretative framework. These days it has become purely molecular, while early on it was purely morphological. My research has gone through all the stages from morphological (dominating my undergraduate studies and present in several papers) through various innovations of the molecular approaches, first solely mtDNA, then the addition of nDNA, first as standard Sanger sequencing in concatenated multilocus approaches and recently through Next Generation Sequencing (NGS).
Example study: Říčan O, Piálek L, Dragová K, Novák J (2016) Diversity and evolution of the Middle American cichlid fishes (Teleostei: Cichlidae) with revised classification. Vertebrate Zoology 66: 1-102.
Figure: Comparisons of nDNA and mtDNA phylogenies of Middle American cichlids with conflicts shown between the two.
Biogeography of cichlids in the Neotropics
Biogeography is the key to understanding biodiversity and evolution. Biodiversity derives directly from biogeography through isolation and/or ecological differentiation due to intrinsic factors and extrinsic factors stemming from geodiversity that determines drainage patterns, habitat ecology and vegetation formations. Biogeography due to its complexity is hence my favorite subject which is reflected in it being the most common topic of my studies together with diversity studies. The gains in knowledge about biogeographical distribution and biogeographical patterns come through exploration and new discoveries and through analytical results.
Example study: Říčan O, Piálek L, Zardoya R, Doadrio I, Zrzavý J. (2013) Biogeography of the Mesoamerican Cichlidae (Teleostei: Heroini): colonization through the GAARlandia land bridge and early diversification. Journal of Biogeography 40: 579–593.
Figures:
1) Dated phylogeny and biogeographic reconstruction.
2) Biogeographic reconstruction of colonization of Middle America overlain on paleogeographic maps.
3) Biogeographic reconstruction of diversification in Middle America overlain on paleogeographic maps.
Morphological and Ecological adaptations and their Evolution
Ecological and morphological characters are the main indicators of adaptation and diversification. Morphological characters and their analysis appears in my publications in the form of taxonomical descriptions and in the delineation (diagnosis) of taxa, in phylogenetic analyses and in the discovery of adaptive characters correlated with the environment and autecology of the taxa. Ecological characteristics of habitats of the studied taxa determine their adaptive trajectories and are one form of biogeographical determinants and are derived directly from the underlying geomorphology and geomorphological history of the given area. As such ecological factors play importantly in our biodiversity studies.
Example study: Říčan O, Piálek L, Dragová K, Novák J (2016) Diversity and evolution of the Middle American cichlid fishes (Teleostei: Cichlidae) with revised classification. Vertebrate Zoology 66: 1-102.
Figure: Combinations of cranial and postcranial ecomorphs and corresponding generic classification of the Middle American cichlids.
Ontogenetic aspect in Evolution
Understanding of mechanisms regulating expression of traits and generating divergence of characters is a key facet of evolutionary biology. Ontogenetic studies are virtually entirely of a laboratory nature, but when the mechanisms and indicators become understood even isolated records from the field and from collections can be incorporated. Ontogeny of characters feature in several of my studies and was predominantly focused on the very complex characters of coloration patterns.
Example studies:
Říčan O, Musilová Z, Muška M, Novák J (2005) Development of coloration patterns in Neotropical cichlids (Perciformes: Cichlidae: Cichlasomatinae). Folia Zoologica: Monograph 1: 1-46.
Říčan O, Piálek L, Dragová K, Novák J (2016) Diversity and evolution of the Middle American cichlid fishes (Teleostei: Cichlidae) with revised classification. Vertebrate Zoology 66: 1-102.
Figure: Evolutionary reconstruction of twenty one different coloration pattern ontogenies found in the Middle American cichlids.
Parallel evolution and ecological speciation in South American pike cichlids (Crenicichla)
Crenicichla are a unique radiation of South American elongate predatory cichlids. This group offers me to investigate many areas of interest - functional innovations, mechanical trade-offs, parallel adaptive radiation, and phylogenetics. My collaborators and I are using phylogenomics (UCEs and ddRADseq) to evaluate Crenicichla phylogeny and population genetics. More specicfically, one area of South America (the Iguazú plus the Middle Paraná, and the Uruguay Rivers) has produced a parallel evolution of similar sets of ecomorphs. These two clades have independently and rapidly evolved several ecomorphs, including species that crush molluscs with hypertrophied pharyngeal jaws, others that pry clinging invertebrates from rock crevices with hypertrophied lips, and yet others that pick at periphyton with compact oral jaws.
Example studies:
Burress ED, Piálek L, Casciotta JR, Almirón A, Tan M, Armbruster JW, Říčan O (2018) Island-and lake-like parallel adaptive radiations replicated in rivers. Proceedings of the Royal Society B: Biological Sciences 285 (1870), 20171762.
Piálek L, Burress E, Dragová K, Almirón A, Casciotta J, Říčan O (2019) Phylogenomics of pike cichlids (Cichlidae: Crenicichla) of the C. mandelburgeri species complex: rapid ecological speciation in the Iguazú River and high endemism in the Middle Paraná basin. Hydrobiologia 832, 355–375.
Burress ED, Piálek L, Casciotta J, Almirón A, Říčan O (2023) Rapid Parallel Morphological and Mechanical Diversification of South American Pike Cichlids (Crenicichla). Systematic Biology 72 (1), 120–133,
Figures: Parallel diversification of Crenicichla cichlids in the Uruguay and Iguazú Rivers with ancestral reconstruction of feeding ecology across the species tree.
Species relationships inside the Iguazú Crenicichla species flock:
a) ML tree with bootstrap supports; b) inference of species diversity and population structure based on the Admixture analysis.
A thorough area and species sampling is crucial in biodiversity studies
A strong point of my studies is thorough sampling of areas and species for my studies.
Only this allows for a meaningfull analysis of all aspects of diversity and is also crucial for new species discoveries.
Example studies South America:
Říčan O, Dragová K, Almirón A, Casciotta J, Gottwald J, Piálek L (2021) MtDNA species-level phylogeny and delimitation support significantly underestimated diversity and endemism in the largest Neotropical cichlid genus (Cichlidae: Crenicichla). PeerJ 9, e12283.
Říčan O, Říčanová Š, Rodriguez Haro LR, Rodriguez Haro CE (2023) Unrecognized species diversity and endemism in the cichlid genus Bujurquina (Teleostei: Cichlidae) together with a molecular phylogeny document large-scale transformation of the western Amazonian river network and reveal complex paleogeography of the Ecuadorian Amazon. Hydrobiologia 850, 2199–2229.
Example study Middle America: Říčan O, Piálek L, Dragová K, Novák J (2016) Diversity and evolution of the Middle American cichlid fishes (Teleostei: Cichlidae) with revised classification. Vertebrate Zoology 66: 1-102.
Figures: Locality coverage used in the example studies (Bujurquina figure from a new study in preparation). Such sampling takes many years and even decades to assemble.
Teaching
Courses taught
A list of throughout the years ....
Systematic ichthyology (KZO / 158)
Ichthyology (KZO / 379)
Molecular methods in Zoology (KZO / 149)
Vertebrate zoogeography (KZO / 369)
Biogeography (KZO / 145)
Phylogenetics (KZO / 595)
Neotropical biology (KZO / 112)
Advances in phylogenetic research in zoology (KZO / 064)
Aquaristics (KZO / 110)
Mesozoic biology (KZO / 111)
Cenozoic biology (KZO / 113)
Diversity and evolution of fossil vertebrates (KZO / 114)
Ecology and ecophysiology of animals (KBD/EKEZ).
Ecology and Environment (KBE/412)
Evolutionary biology and phylogeny (KBO/540)
Seminar in Ecology and Environment (KBE/410)
Seminar in Evolutionary biology and phylogeny (KZO/445)
