Research within the Burress Lab tests long-standing questions in functional morphology and macroevolution such as functional and evolutionary decoupling between anatomical systems, the implications of functional and mechanical trade-offs (e.g., force versus speed), the macroevolutionary consequences of 'key innovations' and biogeographic transitions (e.g., mainland-to-island or river-to-lake), and general features of adaptive radiation (e.g., early bursts of evolution).
Functional innovations and novelties
What fascinates me about functional innovations is that they take many forms, from the conspicuous and elaborate adhesive toepads of geckos and anoles to the near cryptic adaptations of salamanders for digging and climbing. Many innovations with profound functional and ecological implications are relatively modest anatomical changes to existing structures such as ballistic tongue protrusion in salamanders and the modified pharyngeal jaw apparatus in cichlid fishes. I am interested in how innovations alter the evolutionary trajectories of lineages through changes in how organisms interact with their environment. For example, a functional innovation might make it possible to exploit a niche that would otherwise be inaccessible and subsequently enhance the ecological diversity of the group.
Example publication in this area: Burress et al. 2020. Decoupled jaws promote trophic diversity in cichlid fishes. Evolution. PDF.
Thumbnail: lower pharyngeal jaws of several Neotropical cichlids depicting the diversity of shape and dentition; dissected, prepared, and photographed by E.D.B.
Functional and mechanical trade-offs
Many biological systems consist of trade-offs such as the mechanical trade-off between the transmission of velocity versus force that characterize all vertebrate jaw systems and limbs. A major area of interest is the macroevolutionary effects of trade-offs, especially (1) if a trade-off acts as a constraint or promotor of diversification, (2) if the effect is symmetrical (or asymmetrical) along the functional/mechanical extremes of the trade-off, and (3) if the effect varies according to the extent to which a trade-off is explored (i.e., the degree of specialization).
Example publication in this area: Burress and Muñoz 2022. Functional trade-offs asymmetrically promote phenotypic evolution. Systematic Biology. PDF.
Thumbnail: Diagrams depicting motion during the feeding strike in a relatively velocity-modified jaw system (blue; Cichla) and force-modified jaw system (red; Talamancaheros). Pharyngeal jaws are shown in grey. The yellow triangle depicts 30 degrees of lower jaw rotation relative to the left-hand images.
Macroevolutionary features of adaptive radiation
I am interested in theory about adaptive radiation, especially the two extremes - predictable patterns across the tree of life (e.g., parallel evolution) and lineage-specific idiosyncrasies. Research in this area often involves teasing apart alternative explanations for an apparent adaptive radiation. Catalysts of adaptive radiation include the origin of a key innovation, extinction of competitors, geographic transitions (e.g., mainland-to-island or river-to-lake), and hybridization. I mostly use phylogenetic comparative methods, but also ecology and life history, to study both model and non-model groups. My research in this area principally involves cichlids, but also marine fishes, anole lizards, and salamanders.
Example publication in this area: Burress and Muñoz 2022. Ecological opportunity from innovation, not islands, drove the anole lizard adaptive radiation. Systematic Biology. PDF.
Thumbnail: The evolutionary history of the velocity-force trade-off among Neotropical cichlid oral jaws. Illustrations by Julie Johnson.
Parallel evolution and ecological speciation in South American pike cichlids (Crenicichla)
Crenicichla get their own section because they are my favorite fishes and are my most long-standing line of research. Crenicichla are a unique radiation of South American cichlids that are elongate predators. This group allows me to integrate 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. Secondly, I am interested in the parallel evolution of similar sets of ecomorphs in the Iguazú and Uruguay Rivers. 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 publication in this area: Burress et al. 2022. Rapid parallel morphological and mechanical diversification of South American pike cichlids (Crenicichla). Systematic Biology. PDF.
Thumbnail: Parallel adaptive radiation in the Iguazu (yellow) and Uruguay (blue) River species flocks. Paintings and design by Julie Johnson.
Interactions among ecological and geological factors in driving biodiversity
A more recent area of emphasis involves research on Appalachian salamanders and
potential explanations - life history, anatomical, and/geological - in driving the ecological, phenotypic, and species diversity of lungless salamanders throughout the Appalachian Mountains and surrounding foothills.
Example publication in this area: coming soon!
Thumbnail: A red salamander (Pseudotriton ruber vioscai) along a tributary to Halawaki Creek, Alabama, USA, photographed by E.D.B.