Laurel Yohe
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Postdoctoral Researcher, Geology & Geophysics, Yale University
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How Dinosaur Brains and Bat Noses Can Save the World
NatGeo Article
Laurel Yohe presents on How Dinosaur Brains and Bat Noses Can Save the World. This is part of Stony Brook University Postdoc Spotlight 2021 series.
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Genome Biology and Evolution, Aug 2019
Is vomeronasal evolution in bats a one way street? - Anna M. Jackson Award Presentation
Presentation at Evolution 2016: SSB Mayr Award Symposium 2
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In mammals, social and reproductive behaviors are mediated by chemical cues encoded by hyperdiverse families of receptors expressed in the vomeronasal organ. Between species, the number of intact receptors can vary by orders of magnitude. However, the evolutionary processes behind variation in receptor number, and its link to fitness-related behaviors are not well understood. From vomeronasal transcriptomes, we discovered the first evidence of intact vomeronasal type-1 receptor (V1r) genes in bats, and we tested whether putatively functional bat receptors were orthologous to those of related taxa, or whether bats have evolved novel receptors. Instead of lineage-specific duplications, we found that bat V1rs in bats show high levels of orthology to those of their relatives, and receptors are under comparative levels of purifying selection compared to non-bats. Despite widespread vomeronasal organ loss in bats, V1r copies have been retained for >65 million years. The highly conserved nature of bat V1rs challenges our current understanding of mammalian V1r function and suggest roles other than conspecific recognition or mating initiation in social behavior.
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Microscopy and Microanalysis, June 2018
Morphological and developmental basis of olfactory evolution
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The increased accessibility of soft-tissue data through diffusible iodine-based contrast-enhanced computed tomography (diceCT) enables comparative biologists to increase the taxonomic breadth of their studies with museum specimens. However, it is still unclear how soft-tissue measurements from preserved specimens reflect values from freshly collected specimens and whether diceCT preparation may affect these measurements. Here, we document and evaluate the accuracy of diceCT in museum specimens based on the soft-tissue reconstructions of brains and eyes of five bats. Based on proxies, both brains and eyes were roughly 60% of the estimated original sizes when first imaged. However, these structures did not further shrink significantly over a 4-week staining interval, and 1 week in 2.5% iodine-based solution yielded sufficient contrast for differentiating among soft-tissues. Compared to six “fresh” bat specimens imaged shortly after field collection (not fixed in ethanol), the museum specimens had significantly lower relative volumes of the eyes and brains. Variation in field preparation techniques and conditions, and long-term storage in ethanol may be the primary causes of shrinkage in museum specimens rather than diceCT staining methodology. Identifying reliable tissue-specific correction factors to adjust for the shrinkage now documented in museum specimens requires future work with larger samples.
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Biological Journal of the Linnean Society, 2018
Is vomeronasal variation explained by Ecology or Phylogeny
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Vestigial characters are common across the tree of life, but the underlying evolutionary processes shaping phenotypic loss are poorly understood. The mammalian vomeronasal system, which detects social chemical cues important to fitness, is an impressive example of a sensory system lost multiple times. Three times more losses are inferred among bats than in other mammalian orders. We characterized the relationship between amino acid substitutions in a gene tightly linked to vomeronasal function (Trpc2) and the accessory olfactory bulb, a brain region that processes the detection of these vomeronasal chemical cues. By applying a phylogenetic logistic regression, we found a strong negative relationship between the branch lengths representing rates of codon changes in the Trpc2 gene tree and the presence or absence of an accessory olfactory bulb. Longer branch lengths predict loss of the accessory olfactory bulb, suggesting selection has relaxed on the system as a whole. Based on this relationship, we predicted the absence of an accessory olfactory bulb in 19 bat species with unknown morphology. Several species with predicted losses have specialized skull morphology, suggesting a potential tradeoff between adaptation in skull shape and maintenance of the vomeronasal system. This study offers a new approach to relate genetic mechanisms and phenotypes at a macroevolutionary scale.
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Evolution, May 2021
Olfactory receptor evolution shows association with phyllostomid dietary radiation
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The role of mechanical morphologies in the exploitation of novel niche space is well characterized, however, the role of sensory structures in unlocking new niches is less clear. Here we investigate the relationship between the evolution of sensory structures and diet during the radiation of noctilionoid bats. With a broad range of foraging ecologies and a well-supported phylogeny, noctilionoids constitute an ideal group for studying this relationship. We used diffusible iodine-based contrast enhanced computed tomography (diceCT) scans of 44 noctilionoid species to analyze relationships between the relative volumes of three sensory structures (olfactory bulbs, orbits, and cochleae) and diet. We found a positive relationship between frugivory and both olfactory and orbit size. However, we also found a negative relationship between nectarivory and cochlea size. Ancestral state estimates suggest that larger orbits and olfactory bulbs were present in the common ancestor of family Phyllostomidae, but not in other noctilionoid. This constellation of traits indicates a shift toward omnivory at the base of Phyllostomidae, predating their radiation into an exceptionally broad range of dietary niches. This is consistent with a scenario in which changes in sensory systems associated with foraging and feeding set the stage for subsequent morphological modification and diversification.