I am inspired by the diversity in fishes and their huge variety in species and forms. There are about as many fish species as there are birds, amphibians, reptiles, and mammals combined, so they are an important part of vertebrate diversity. In my research, I study the evolution of fishes to understand their relationships, the evolution of traits in fishes like body size, and how fishes diversified. To do this, I use genomics and comparative methods to reconstruct evolutionary trees, which then provide a historical framework to reconstruct how genomes and traits evolved.
Whole Genome Analysis of the Whale Shark
The Whale Shark genome project is a collaboration between Emory University and Georgia Aquarium. Whale sharks are the largest species of fish, and one of the most charismatic fishes in the sea. Despite the wide public interest in sharks, there were no published genomes for any true sharks until we published the whale shark genome. In ongoing research, we will use the genome to help us understand the origin of vertebrates, the evolution of sharks, and the unique biology of the whale shark.
- 2017. TD Read, RA Petit III, SJ Joseph, MT Alam, MR Weil, Maida Ahmad, R Bhimani, JS Vuong, CP Haase, DH Webb, M Tan (corresponding author), ADM Dove. Draft sequencing and assembly of the genome of the world’s largest fish, the whale shark: Rhincodon typus Smith 1828. BMC Genomics 18: 532. doi: 10.1186/s12864-017-3926-9
Evolution of Miniaturization in Cypriniformes
The order Cypriniformes is one of the most diverse groups of fishes, including over 4,000 species of carps, minnows, and their relatives. The Cypriniformes also have among the largest number of species of miniature fishes, including some of the smallest vertebrates, like Paedocypris. I have been particularly interested in understanding the evolution of miniaturization in these fishes. My research has provided insight into the relationships among fishes in this group, into patterns of body size evolution across one of the most diverse groups of fishes, and into the effect of selection across thousands of genes in miniature fishes. (Photo kindly provided by Rupert Collins).
- 2016. CC Stout, M Tan (co-first author), AR Lemmon, EM Lemmon, JW Armbruster. Resolving Cypriniformes relationships using an Anchored Hybrid Enrichment approach. BMC Evolutionary Biology 16: 244. doi: 10.1186/s12862-016-0819-5
Adaptive Radiation in Fishes
Adaptive radiation is a classic process used to explain the diversity of species. However, adaptive radiation has been difficult to detect in many comparative datasets. In collaboration with Dr. Ed Burress, we are dissecting the patterns of evolution in fishes, especially cichlids, to gain insight into the role of ecology and morphology in their diversification.
- 2018. ED Burress, L Piálek, J Casciotta, A Almirón, M Tan, JW Armbruster, O Říčan. Island- and lake-like parallel adaptive radiations replicated in rivers. Proceedings of the Royal Society B 285: 20171762. doi: 10.1098/rspb.2017.1762
- 2017. ED Burress, M Tan. Ecological opportunity alters the timing and shape of adaptive radiation. Evolution. doi: 10.1111/evo.13362
- 2017. ED Burress, JM Holcomb, M Tan, JW Armbruster. Ecological diversification associated with the benthic-to-pelagic transition by North American minnows. Journal of Evolutionary Biology 30(3): 549-560. doi: 10.1111/jeb.13024
Evolution of Defenses in Catfishes
The catfishes (Order Siluriformes) are a diverse group of fishes. Roughly one in twenty vertebrate species is a catfish! It has been hypothesized that the evolution of catfish defense mechanisms have helped catfishes diversify, but this has yet to be tested. Through a recently-funded fellowship from the National Science Foundation, I will study the relationship of the evolution of catfish defense mechanisms to their rates of diversification.
Part of what makes research so exciting is to be able to get out into the field to catch fishes! I have been lucky to have numerous field experiences, including in the United States, Suriname, Thailand, and Peru. Catching fish isn’t just stamp collecting, specimens serve as a primary source of data for my research, so that I can understand what species are out there, where they’re found, and what their genes and genomes are like. Specimens that I have collected have been preserved and stored in natural history collections at Auburn University and the Florida Museum of Natural History. In the photo, I am inspecting a vial of larval fishes I had just collected in the Salween River of Thailand, under the shadow of the mountains that form the border on the Myanmar side. (Photo by Zach Randall).
- 2014. CK Ray, M Tan, & JW Armbruster. First record of Chrosomus erythrogaster (Cypriniformes: Cyprinidae) in the Mobile Basin. Southeastern Naturalist 13(4): N33-N36. doi: 10.1656/058.013.0402
Taxonomy of Fishes
Many species remain unknown to science. For scientists to understand how biodiversity arose and the evolution of biodiversity, we must understand what is out there. Furthermore, the classification of these species provides the foundation for the understanding of the diversity of species. I have helped describe numerous new species of catfishes from South America. Pictured is a new species that we described, Peckoltia greedoi, photo by Jonathan Armbruster. I have also contributed to the classification of species that are part of the Order Cypriniformes.
- 2018. M Tan, JW Armbruster. Phylogenetic classification of extant genera of fishes of the order Cypriniformes (Teleostei: Ostariophysi). Zootaxa 4476(1): 006–039. doi: 10.11646/zootaxa.4476.1.4
- 2016. M Tan, LS de Souza, JW Armbruster. A new species of Panaqolus (Siluriformes: Loricariidae) from the rio Branco. Neotropical Ichthyology 14(2): e150033. doi: 10.1590/1982-0224-20150033
- 2016. M Tan, JW Armbruster. Two new species of spotted Hypancistrus from the Rio Negro Drainage (Loricariidae, Hypostominae). ZooKeys 552: 123-135. doi: 10.3897/zookeys.552.5956
- 2015. JW Armbruster, DC Werneke, M Tan. Three new species of saddled loricariid catfishes, and a review of Hemiancistrus, Peckoltia, and allied genera (Siluriformes). ZooKeys 480: 97-123. doi: 10.3897/zookeys.480.6540
- 2012. M Tan, JW Armbruster. Cordylancistrus santarosensis (Siluriformes: Loricariidae), a new species with unique snout deplatation from the Río Santa Rosa, Ecuador. Zootaxa 3243:52-58.