105 results found
Rubin C-J, Enbody ED, Dobreva MP, et al., 2022, Rapid adaptive radiation of Darwin's finches depends on ancestral genetic modules, SCIENCE ADVANCES, Vol: 8, ISSN: 2375-2548
Marghoub A, Williams CJA, Leite JV, et al., 2022, Unravelling the structural variation of lizard osteoderms, ACTA BIOMATERIALIA, Vol: 146, Pages: 306-316, ISSN: 1742-7061
Vickaryous M, Williams C, Willan G, et al., 2022, Histological Diversity And Evolution Of Lizard Osteoderms., FASEB J, Vol: 36 Suppl 1
Many reptiles reinforce the dermis with discrete mineralized organs known as osteoderms. Among lizards, osteoderms demonstrate species-specific differences in size, shape, and distribution across the body. Whether osteoderms also vary in details of tissue composition, including the organization of the fibrillar matrix, remains unclear. Here, we investigate osteoderm histology in three species-rich lizard groups: gekkotans (geckos), scincids (skinks), and anguimorphans (anguids, helodermatids, and related taxa). With one possible exception, all lizard osteoderms are dominated by bone tissue. Unexpectedly, representative members of all the major groups develop an enigmatic, collagen-poor capping tissue. Gekkotan osteoderms are rare (<2% of species) and demonstrate considerable histological heterogeneity between species. This includes variation in bone matrices, and the development of additional (non-osseous) skeletal tissues. In the gecko genus Geckolepis, putative osteoderms appear to lack bone and instead are composed of dense collagen plates capped by a vitreous collagen-poor tissue. Unlike geckos, osteoderms are common to virtually all skinks. Most skink osteoderms are compound elements, composed of multiple conjoined smaller plates (referred to as osteodermites). Histologically, skink osteoderms are dominated by lamellar bone with well-organized Sharpey's fibres linking adjacent plates together and some woven and parallel-fibred bone. Most species develop the collagen-poor capping tissue, particularly where adjacent osteodermites articulate with one another. Osteoderms are also common to many anguimorphans, but the histology varies considerably between taxa. While anguid and helodermatid osteoderms demonstrate multiple bone matrices (woven-fibred, parallel-fibred, lamellar bone, and Sharpey-fibred), Shinisaurus osteoderms are primarily woven-fibred and Sharpey-fibred bone, and those of Varanus are mostly parallel-fibred bone. Expression of the capping tissue a
Enbody ED, Sprehn CG, Abzhanov A, et al., 2021, A multispecies BCO2 beak color polymorphism in the Darwin's finch radiation, CURRENT BIOLOGY, Vol: 31, Pages: 5597-+, ISSN: 0960-9822
Dobreva MP, Camacho J, Abzhanov A, 2021, Time to synchronize our clocks: Connecting developmental mechanisms and evolutionary consequences of heterochrony., Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, ISSN: 1552-5007
Heterochrony, defined as a change in the timing of developmental events altering the course of evolution, was first recognized by Ernst Haeckel in 1866. Haeckel's original definition was meant to explain the observed parallels between ontogeny and phylogeny, but the interpretation of his work became a source of controversy over time. Heterochrony took its modern meaning following the now classical work in the 1970-80s by Steven J. Gould, Pere Alberch, and co-workers. Predicted and described heterochronic scenarios emphasize the many ways in which developmental changes can influence evolution. However, while important examples of heterochrony detected with comparative morphological methods have multiplied, the more mechanistic understanding of this phenomenon lagged conspicuously behind. Considering the rapid progress in imaging and molecular tools available now for developmental biologists, this review aims to stress the need to take heterochrony research to the next level. It is time to synchronize the different levels of heterochrony research into a single analysis flow: from studies on organismal-level morphology to cells to molecules and genes, using complementary techniques. To illustrate how to achieve a more comprehensive understanding of phyletic morphological diversification associated with heterochrony, we discuss several recent case studies at various phylogenetic scales that combine morphological, cellular, and molecular analyses. Such a synergistic approach offers to more fully integrate phylogenetic and ontogenetic dimensions of the fascinating evolutionary phenomenon of heterochrony.
Al-Mosleh S, Choi GPT, Abzhanov A, et al., 2021, Geometry and dynamics link form, function, and evolution of finch beaks., Proceedings of the National Academy of Sciences of USA, Vol: 118, Pages: 1-7, ISSN: 0027-8424
Darwin's finches are a classic example of adaptive radiation, exemplified by their adaptive and functional beak morphologies. To quantify their form, we carry out a morphometric analysis of the three-dimensional beak shapes of all of Darwin's finches and find that they can be fit by a transverse parabolic shape with a curvature that increases linearly from the base toward the tip of the beak. The morphological variation of beak orientation, aspect ratios, and curvatures allows us to quantify beak function in terms of the elementary theory of machines, consistent with the dietary variations across finches. Finally, to explain the origin of the evolutionary morphometry and the developmental morphogenesis of the finch beak, we propose an experimentally motivated growth law at the cellular level that simplifies to a variant of curvature-driven flow at the tissue level and captures the range of observed beak shapes in terms of a simple morphospace. Altogether, our study illuminates how a minimal combination of geometry and dynamics allows for functional form to develop and evolve.
Liang C, Marghoub A, Kever L, et al., 2021, Lizard osteoderms - Morphological characterisation, biomimetic design and manufacturing based on three species, BIOINSPIRATION & BIOMIMETICS, Vol: 16, ISSN: 1748-3182
Morris ZS, Vliet KA, Abzhanov A, et al., 2021, Developmental origins of the crocodylian skull table and platyrostral face, ANATOMICAL RECORD-ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Vol: 305, Pages: 2838-2853, ISSN: 1932-8486
Williams C, Kirby A, Marghoub A, et al., 2021, A review of the osteoderms of lizards (Reptilia: Squamata), BIOLOGICAL REVIEWS, Vol: 97, Pages: 1-19, ISSN: 1464-7931
Morris Z, Abzhanov A, Pierce S, 2021, Embryonic origins of the flattened skull table and snout in Crocodylia, Experimental Biology Meeting, Publisher: WILEY, ISSN: 0892-6638
Dobreva MP, Lynton-Jenkins JG, Chaves JA, et al., 2021, Sex identification in embryos and adults of Darwin's finches, PLoS One, Vol: 16, Pages: 1-13, ISSN: 1932-6203
Darwin’s finches are an iconic example of adaptive radiation and evolution under natural selection. Comparative genetic studies using embryos of Darwin’s finches have shed light on the possible evolutionary processes underlying the speciation of this clade. Molecular identification of the sex of embryonic samples is important for such studies, where this information often cannot be inferred otherwise. We tested a fast and simple chicken embryo protocol to extract DNA from Darwin’s finch embryos. In addition, we applied minor modifications to two of the previously reported PCR primer sets for CHD1, a gene used for sexing adult passerine birds. The sex of all 29 tested embryos of six species of Darwin’s finches was determined successfully by PCR, using both primer sets. Next to embryos, hatchlings and fledglings are also impossible to distinguish visually. This extends to juveniles of sexually dimorphic species which are yet to moult in adult-like plumage and beak colouration. Furthermore, four species of Darwin’s finches are monomorphic, males and females looking alike. Therefore, sex assessment in the field can be a source of error, especially with respect to juveniles and mature monomorphic birds outside of the mating season. We caught 567 juveniles and adults belonging to six species of Darwin’s finches and only 44% had unambiguous sex-specific morphology. We sexed 363 birds by PCR: individuals sexed based on marginal sex specific morphological traits; and birds which were impossible to classify in the field. PCR revealed that for birds with marginal sex specific traits, sexing in the field produced a 13% error rate. This demonstrates that PCR based sexing can improve field studies on Darwin’s finches, especially when individuals with unclear sex-related morphology are involved. The protocols used here provide an easy and reliable way to sex Darwin’s finches throughout ontogeny, from embryos to adults.
Abzhanov A, 2021, The many faces of evolution: heterochronic developmental mechanisms for adaptive radiations, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E2-E3, ISSN: 1540-7063
Morris ZS, Abzhanov A, 2021, Heading for higher ground: Developmental origins and evolutionary diversification of the amniote face, EVOLUTIONARY DEVELOPMENTAL BIOLOGY, Vol: 141, Pages: 241-277, ISSN: 0070-2153
Reaney AM, BouchenakKhelladi Y, Tobias JA, et al., 2020, Ecological and morphological determinants of evolutionary diversification in Darwin's finches and their relatives, Ecology and Evolution, Vol: 10, Pages: 14020-14032, ISSN: 2045-7758
Darwin's finches are a classic example of adaptive radiation, a process by which multiple ecologically distinct species rapidly evolve from a single ancestor. Such evolutionary diversification is typically explained by adaptation to new ecological opportunities. However, the ecological diversification of Darwin's finches following their dispersal to Galápagos was not matched on the same archipelago by other lineages of colonizing land birds, which diversified very little in terms of both species number and morphology. To better understand the causes underlying the extraordinary variation in Darwin's finches, we analyze the evolutionary dynamics of speciation and trait diversification in Thraupidae, including Coerebinae (Darwin's finches and relatives) and, their closely related clade, Sporophilinae. For all traits, we observe an early pulse of speciation and morphological diversification followed by prolonged periods of slower steady‐state rates of change. The primary exception is the apparent recent increase in diversification rate in Darwin's finches coupled with highly variable beak morphology, a potential key factor explaining this adaptive radiation. Our observations illustrate how the exploitation of ecological opportunity by contrasting means can produce clades with similarly high diversification rate yet strikingly different degrees of ecological and morphological differentiation.
Lee HW, Esteve-Altava B, Abzhanov A, 2020, Evolutionary and ontogenetic changes of the anatomical organization and modularity in the skull of archosaurs, Scientific Reports, Vol: 10, Pages: 1-13, ISSN: 2045-2322
Comparative anatomy studies of the skull of archosaurs provide insights on the mechanisms of evolution for the morphologically and functionally diverse species of crocodiles and birds. One of the key attributes of skull evolution is the anatomical changes associated with the physical arrangement of cranial bones. Here, we compare the changes in anatomical organization and modularity of the skull of extinct and extant archosaurs using an Anatomical Network Analysis approach. We show that the number of bones, their topological arrangement, and modular organization can discriminate birds from non-avian dinosaurs, and crurotarsans. We could also discriminate extant taxa from extinct species when adult birds were included. By comparing within the same framework, juveniles and adults for crown birds and alligator (Alligator mississippiensis), we find that adult and juvenile alligator skulls are topologically similar, whereas juvenile bird skulls have a morphological complexity and anisomerism more similar to those of non-avian dinosaurs and crurotarsans than of their own adult forms. Clade-specific ontogenetic differences in skull organization, such as extensive postnatal fusion of cranial bones in crown birds, can explain this pattern. The fact that juvenile and adult skulls in birds do share a similar anatomical integration suggests the presence of a specific constraint to their ontogenetic growth.
Camacho J, Moon R, Smith SK, et al., 2020, Differential cellular proliferation underlies heterochronic generation of cranial diversity in phyllostomid bats, EvoDevo, Vol: 11, ISSN: 2041-9139
BackgroundSkull diversity in the neotropical leaf-nosed bats (Phyllostomidae) evolved through a heterochronic process called peramorphosis, with underlying causes varying by subfamily. The nectar-eating (subfamily Glossophaginae) and blood-eating (subfamily Desmondontinae) groups originate from insect-eating ancestors and generate their uniquely shaped faces and skulls by extending the ancestral ontogenetic program, appending new developmental stages and demonstrating peramorphosis by hypermorphosis. However, the fruit-eating phyllostomids (subfamilies Carollinae and Stenodermatinae) adjust their craniofacial development by speeding up certain developmental processes, displaying peramorphosis by acceleration. We hypothesized that these two forms of peramorphosis detected by our morphometric studies could be explained by differential growth and investigated cell proliferation during craniofacial morphogenesis.ResultsWe obtained cranial tissues from four wild-caught bat species representing a range of facial diversity and labeled mitotic cells using immunohistochemistry. During craniofacial development, all bats display a conserved spatiotemporal distribution of proliferative cells with distinguishable zones of elevated mitosis. These areas were identified as modules by the spatial distribution analysis. Ancestral state reconstruction of proliferation rates and patterns in the facial module between species provided support, and a degree of explanation, for the developmental mechanisms underlying the two models of peramorphosis. In the long-faced species, Glossophaga soricina, whose facial shape evolved by hypermorphosis, cell proliferation rate is maintained at lower levels and for a longer period of time compared to the outgroup species Miniopterus natalensis. In both species of studied short-faced fruit bats, Carollia perspicillata and Artibeus jamaicensis, which evolved under the acceleration model, cell proliferation rate is increased compared to the outgroup.Conc
Morris ZS, Pierce SE, Abzhanov A, 2020, Developmental mechanisms shaping crocodylian snouts, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E166-E166, ISSN: 1540-7063
Camacho J, Heyde A, Bhullar B-AS, et al., 2019, Peramorphosis, an evolutionary developmental mechanism in neotropical bat skull diversity, Developmental Dynamics, Vol: 248, Pages: 1129-1143, ISSN: 1058-8388
BackgroundThe neotropical leaf‐nosed bats (Chiroptera, Phyllostomidae) are an ecologically diverse group of mammals with distinctive morphological adaptations associated with specialized modes of feeding. The dramatic skull shape changes between related species result from changes in the craniofacial development process, which brings into focus the nature of the underlying evolutionary developmental processes.ResultsIn this study, we use three‐dimensional geometric morphometrics to describe, quantify, and compare morphological modifications unfolding during evolution and development of phyllostomid bats. We examine how changes in development of the cranium may contribute to the evolution of the bat craniofacial skeleton. Comparisons of ontogenetic trajectories to evolutionary trajectories reveal two separate evolutionary developmental growth processes contributing to modifications in skull morphogenesis: acceleration and hypermorphosis.ConclusionThese findings are consistent with a role for peramorphosis, a form of heterochrony, in the evolution of bat dietary specialists.
Abzhanov A, 2019, Phylogenetic principles and morphogenetic mechanisms for evolvability in avian adaptive radiations., Society for Comparative and Integrative Biology (SICB)
Abzhanov A, 2019, Use it or lose it: integration of cranial skeleton and musculature from plasticity to genetic assimilation, ”Morphometrics: Geometry and Statistics” workshop
Abzhanov A, 2019, Phylogenetic principles and morphogenetic mechanisms for evolvability and biological shape change, ” Morphogenesis: Geometry and Physics” workshop
Morris ZS, Abzhanov A, Pierce SE, 2019, Correlations between Developmental, Ecological, and Evolutionary Axes of Cranial Shape Variation in Extant Crocodylians and the Pseudosuchian Fossil Record, Publisher: WILEY, Pages: S186-S187, ISSN: 0362-2525
Camacho J, Moon R, Seetahal J, et al., 2019, Origins of Craniofacial Diversity in New World Leaf-Nosed Bats at the Developmental, Cellular and Genetic level, Publisher: WILEY, Pages: S93-S93, ISSN: 0362-2525
Abzhanov A, 2019, Shaping the beaks of Darwin's finches: developmental mechanisms of the famous adaptive radiation, UK Evo-Devo Symposium
Morris ZS, Pierce SE, Abzhanov A, 2019, The role of craniofacial growth zones in shaping crocodylian snouts, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E162-E162, ISSN: 1540-7063
Morris ZS, Vliet KA, Abzhanov A, et al., 2019, Heterochronic shifts and conserved embryonic shape underlie crocodylian craniofacial disparity and convergence, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 286, ISSN: 0962-8452
Abzhanov A, 2018, Shaping the beaks of Darwin's finches: developmental mechanisms of the famous adaptive radiation, Darwin's Day
Abzhanov A, 2018, Shaping the faces of Darwin's finches and phyllostomid bats: developmental mechanisms of two famous adaptive radiations., “Growth, patterning and scaling during development”
Camacho J, Tabin CJ, Abzhanov A, 2018, Exploring adaptive and novel traits of bat faces through morphometrics and developmental genetics, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E28-E28, ISSN: 1540-7063
Abzhanov A, 2018, Phylogenetic evidence and ontogenetic mechanisms for evolvability in avian adaptive radiations, Avian Models 10
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