My research aims to understand how speciation and evolution occur within the largest group of vertebrates – fishes. To accomplish this, I use a multifaceted approach, applying a variety of methods across recent and ancient time scales. See below for specific research projects that I am currently working on.
Fish Systematics and Ancient Processes
To gain insight into how evolution may currently occur in fishes we must take a deeper look at how evolution has shaped fish diversity in the past. To this end, a major component of my research is to investigate how certain groups of fishes are related to one another. With over 36,000 species, fishes are more diverse than mammals, birds, and reptiles combined! Earlier work shed light on how fishes are related by using carefully selected morphological characters. While these techniques are still in use, genomic techniques have advanced tremendously in the past 30 years and are now standard in many phylogenetic studies. However, in many cases our understanding of fish interrelationships are based on a handful of genes, and in some cases we don't know how certain groups are related to each other at all. My research uses advanced genomic techniques to look at many sections of the genome (hundreds to thousands of regions) in an attempt to gain a more balanced idea of how fishes are interrelated. This data is then used to determine how Earth's geological history has shaped evolution in fishes (see Biogeography below), how certain habitat shifts have impacted fishes, or how certain morphological characters have changed over time.
Example publications:
Ludt WB, Burridge CP, Chakrabarty P (2019) A taxonomic revision of Cheilodactylidae and Latridae (Centrarchiformes: Cirrhitoidei) using morphological and genomic characters. Zootaxa, 4585 (1): 121–141.
Ludt, WB, Rocha LA, Erdmann MV, Chakrabarty P (2015) Skipping across the tropics: the evolutionary history of sawtail surgeonfishes (Acanthuridae: Prionurus). Molecular Phylogenetics and Evolution 84, 166-172.
Example publications:
Ludt WB, Burridge CP, Chakrabarty P (2019) A taxonomic revision of Cheilodactylidae and Latridae (Centrarchiformes: Cirrhitoidei) using morphological and genomic characters. Zootaxa, 4585 (1): 121–141.
Ludt, WB, Rocha LA, Erdmann MV, Chakrabarty P (2015) Skipping across the tropics: the evolutionary history of sawtail surgeonfishes (Acanthuridae: Prionurus). Molecular Phylogenetics and Evolution 84, 166-172.
Population Genomics and Recent Processes
Examining fish relationships over deeper time scales can provide a historic context to fish evolution, but it is not good at determining what exactly caused speciation. Population-level process, on the other hand, can shed light on which evolutionary mechanisms are currently occurring in fishes. My research examines population processes in several systems to determine what may lead certain populations to diverge into species, and what influences population dynamics in the Indo-Pacific.
Example publications:
Ludt WB, Bernal MA, Kenworthy E*, Salas E, Chakrabarty P (2019) Investigating species limits of surgeonfishes from the Eastern Pacific (Acanthuridae: Prionurus) using genomic, ecological, and morphological data. Ecology & Evolution, 9(7), 4001–4012.
Ludt, WB, Bernal M, Bowen B, Rocha LA (2012) Living in the past: Phylogeography and population histories of Indo-Pacific Wrasses (Genus Halichoeres) in shallow lagoons versus outer reef slopes. PLoS ONE 7(6): e38042. doi:10.1371/journal.pone.0038042
Example publications:
Ludt WB, Bernal MA, Kenworthy E*, Salas E, Chakrabarty P (2019) Investigating species limits of surgeonfishes from the Eastern Pacific (Acanthuridae: Prionurus) using genomic, ecological, and morphological data. Ecology & Evolution, 9(7), 4001–4012.
Ludt, WB, Bernal M, Bowen B, Rocha LA (2012) Living in the past: Phylogeography and population histories of Indo-Pacific Wrasses (Genus Halichoeres) in shallow lagoons versus outer reef slopes. PLoS ONE 7(6): e38042. doi:10.1371/journal.pone.0038042
Biogeography and Phylogeography
Biogeography is the study of where animals occur, and gives us insights into how geological or climatic processes on this planet affect evolution. Identifying biogeographic patterns, and understanding what is driving them, is a major component of my research. I use genomic data generated using the methods above for historical biogeography and phylogeographic inferences, respectively, allowing me to examine biogeographic process on shallow, and deeper time scales. In addition to genomic techniques, I also use species occurrence data, generated from vouchered museum specimens, to examine patterns of regional species diversity, and to generate species distribution models to examine how species habitats have shifted through time. In concert, these two approaches give insight into how Earth's history has impacted species diversity patterns over time.
Example publications:
Ludt WB, Myers CE (2021) Distinguishing Between Dispersal and Vicariance: A Novel Approach Using Anti-Tropical Taxa Across the Fish Tree of Life. Journal of Biogeography, 48(3), 577–589.
Ludt, WB, Rocha LA (2015) Shifting seas: the impacts of Pleistocene sea-level fluctuations on the evolution of tropical marine taxa. Journal of Biogeography 42, 25-38.
Example publications:
Ludt WB, Myers CE (2021) Distinguishing Between Dispersal and Vicariance: A Novel Approach Using Anti-Tropical Taxa Across the Fish Tree of Life. Journal of Biogeography, 48(3), 577–589.
Ludt, WB, Rocha LA (2015) Shifting seas: the impacts of Pleistocene sea-level fluctuations on the evolution of tropical marine taxa. Journal of Biogeography 42, 25-38.
Empowering Museums and Understanding Our Impact
Natural history museums are a one-of-a-kind resource that many people don't fully appreciate. They function as libraries of biodiversity, documenting how species and communities change across space and time. In this capacity they act as the only working time machines on our planet, allowing anyone to go to a specific location and date and physically hold and examine the plants or animals that were there. However, support for natural history museums has changed over time and we have lost many smaller, but important, regional collections. Additionally, training in preservation and proper museum techniques is not as common as it once was. Part of our efforts at the NHMLA are not only promote the use of collections, but to also train others in how to manage, maintain, and increase the capacity of their own collections. We also strive to use museum material in ways to help us understand our own impact on wildlife. Current projects include examining microplastic contamination in California coastal fishes over an eight decade time period that is funded by the California Ocean Protection Council and California Sea Grant. Find out more about microplastics here!
Example publications:
Shultz AJ, Adams BJ, Bell KC, Ludt WB, Pauly GB, Vendetti JE (2021) Natural history collections are critical and underutilized resources for contemporary and future studies of urban evolution. Evolutionary Applications, 14, 233–247.
Ludt WB, Jabado RW, Al Hameli SM, Freeman L*, Teruyama G*, Chakrabarty P, Al Dhaheri SS (2020) Establishing a reference collection and DNA barcoding the coastal fishes of the United Arab Emirates. Journal of the Ocean Science Foundation, 35, 54–64.
Example publications:
Shultz AJ, Adams BJ, Bell KC, Ludt WB, Pauly GB, Vendetti JE (2021) Natural history collections are critical and underutilized resources for contemporary and future studies of urban evolution. Evolutionary Applications, 14, 233–247.
Ludt WB, Jabado RW, Al Hameli SM, Freeman L*, Teruyama G*, Chakrabarty P, Al Dhaheri SS (2020) Establishing a reference collection and DNA barcoding the coastal fishes of the United Arab Emirates. Journal of the Ocean Science Foundation, 35, 54–64.