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1. Eye‐body allometry across biphasic ontogeny in anuran amphibians

   https://doi.org/doi.org/10.1007/s10682-021-10102-3  

   Shrimpton, S. J.; Streicher, J. W.; Gower, D. J.; Bell, R. C.; Fujita, M. K.; Schott, R. K.; Thomas, K. N. (January 2021, Elements in evolutionary economics)

   Animals with biphasic lifecycles often inhabit different visual environments across ontogeny. Many frogs and toads (Amphibia: Anura) have free-living aquatic larvae (tadpoles) that metamorphose into adults that inhabit a range of aquatic and terrestrial environments. Ecological differences influence eye size across species, but these relationships have not yet been explored across life stages in an ontogenetic allometric context. We examined eye-body size scaling in a species with aquatic larvae and terrestrial adults, the common frog Rana temporaria, using a well-sampled developmental series. We found a shift in ontogenetic allometric trajectory near metamorphosis indicating prioritized growth in tadpole eyes. To explore the effects of different tadpole and adult ecologies on eye-body scaling, we expanded our taxonomic sampling to include developmental series of eleven additional anuran species. Intraspecific eye-body scaling was variable among species, with 8/12 species exhibiting a significant change in allometric slope between tadpoles and adults. Traits categorizing both tadpole ecology (microhabitat, eye position, mouth position) and adult ecology (habitat, activity pattern) across species had significant effects on allometric slopes among tadpoles, but only tadpole eye position had a significant effect among adults. Our study suggests that relative eye growth in the preliminary stages of biphasic anuran ontogenies is somewhat decoupled and may be shaped by both immediate ecological need (i.e. tadpole visual requirements) and what will be advantageous during later adult stages. 

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2. Diversity and evolution of amphibian pupil shapes

   https://doi.org/10.1093/biolinnean/blac095  

   Thomas, Kate N; Rich, Caitlyn; Quock, Rachel C; Streicher, Jeffrey W; Gower, David J; Schott, Ryan K; Fujita, Matthew K; Douglas, Ron H; Bell, Rayna C (September 2022, Biological Journal of the Linnean Society)

   Abstract Pupil constriction has important functional consequences for animal vision, yet the evolutionary mechanisms underlying diverse pupil sizes and shapes are poorly understood. We aimed to quantify the diversity and evolution of pupil shapes among amphibians and to test for potential correlations to ecology based on functional hypotheses. Using photographs, we surveyed pupil shape across adults of 1294 amphibian species, 74 families and three orders, and additionally for larval stages for all families of frogs and salamanders with a biphasic ontogeny. For amphibians with a biphasic life history, pupil shape changed in many species that occupy distinct habitats before and after metamorphosis. In addition, non-elongated (circular or diamond) constricted pupils were associated with species inhabiting aquatic or underground environments, and elongated pupils (with vertical or horizontal long axes) were more common in species with larger absolute eye sizes. We propose that amphibians provide a valuable group within which to explore the anatomical, physiological, optical and ecological mechanisms underlying the evolution of pupil shape. 

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3. Eye size and investment in frogs and toads correlate with adult habitat, activity pattern and breeding ecology

   https://doi.org/10.1098/rspb.2020.1393  

   Thomas, K. M.; Gower, D. J.; Bell, R. C.; Fujita, M. K.; Schott, R. K.; Streicher, J. W. (July 2020, Proceedings)

   null (Ed.)

   Frogs and toads (Amphibia: Anura) display diverse ecologies and behaviours, which are often correlated with visual capacity in other vertebrates. Additionally, anurans exhibit a broad range of relative eye sizes, which have not previously been linked to ecological factors in this group. We measured relative investment in eye size and corneal size for 220 species of anurans representing all 55 currently recognized families and tested whether they were correlated with six natural history traits hypothesized to be associated with the evolution of eye size. Anuran eye size was significantly correlated with habitat, with notable decreases in eye investment among fossorial, subfossorial and aquatic species. Relative eye size was also associated with mating habitat and activity pattern. Compared to other vertebrates, anurans have relatively large eyes for their body size, indicating that vision is probably of high importance. Our study reveals the role that ecology and behaviour may have played in the evolution of anuran visual systems and highlights the usefulness of museum specimens, and importance of broad taxonomic sampling, for interpreting macroecological patterns. 

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4. Late Cretaceous Notosuchians of the Maevarano Formation, Mahajanga Basin: An Ecomorphological Perspective

   Rakotozafy, B; Ranivoharimanana, L; Sertich, JJW; Rasoamiaramanana, A; O'Connor, PM (July 2024, Madamines)

   ABSTRACT The Maastrichtian Maevarano Formation of northwestern Madagascar represents deposition in a seasonal dry-wet system and hosts a rich assemblage of well-preserved fossil vertebrates. Notosuchian crocodyliforms, a diverse group of mesoeucrocodylians frequently found in Upper Cretaceous rocks of Gondwana, are well represented in this assemblage. The current study focuses on the four recognized notosuchians (Simosuchus clarki, Araripesuchus tsangatsangana, Miadanasuchus oblita and Mahajangasuchus insignis), examining their morphologic diversity to provide insight into the ecology of these sympatric taxa. Here, several complete and incomplete skulls were examined, with measurements of each cranial opening acquired for quantitative analysis. Digital photographs and high-resolution renderings based on CT/µCT reconstructions were utilized. The size, position, and orientation of the external nares, orbits, and choanae were characterized, with the relative position and size of temporal, suborbital, and external mandibular fenestrae noted for comparisons. The dentitions (size, shape, number of teeth) of the four notosuchians were also included in this study, allowing direct insight into feeding ecology of the four taxa. From the data and approaches used herein, morphologic differences were utilized to interpret potential roles of the different species in the Maevarano ecosystem. The four notosuchians can be divided between terrestrial and semi-aquatic habits, and within these ecologies, size and tooth shape assist in determining possible feeding ecology. Of the three primarily carnivorous taxa (Mahajangasuchus, Miadanasuchus, Araripesuchus), only Miadanasuchus and Araripesuchus overlapped ecologically as terrestrial predators. Maximum adult size differences between these two forms likely contributed to differences in prey choice, thereby permitting coexistence in the terrestrial environment. Simosuchus, the other terrestrial notosuchian, clearly differs from the others based on both skull and dental morphology and occupied a primarily herbivorous niche. Finally, Mahajangasuchus is the sole semi-aquatic notosuchian in the assemblage, sharing this habitat with representative and smaller-bodied neosuchians and other aquatic vertebrates and potentially competing with the other carnivorous forms for prey. In sum, the Maevarano Formation vertebrate assemblage can be used as a case-study for comparison with other Mesozoic assemblages with multiple crocodyliforms. 

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5. Trait–environment relationships could alter the spatial and temporal characteristics of aquatic insect subsidies at the macrospatial scale

   https://doi.org/10.1111/ecog.05298  

   Kopp, Darin; Allen, Daniel (December 2020, Ecography)

   null (Ed.)

   Ecological flows across ecosystem boundaries are typically studied at spatial scales that limit our understanding of broad geographical patterns in ecosystem linkages. Aquatic insects that metamorphose into terrestrial adults are important resource subsidies for terrestrial ecosystems. Traits related to their development and dispersal should determine their availability to terrestrial consumers. Here, we synthesize geospatial, aquatic biomonitoring and biological traits data to quantify the relative importance of several environmental gradients on the potential spatial and temporal characteristics of aquatic insect subsidies across the contiguous United States. We found the trait composition of benthic macroinvertebrate communities varies among hydrologic regions and could affect how aquatic insects transport subsidies as adults. Further, several trait–environment relationships were underpinned by hydrology. Large bodied taxa that could disperse further from the stream were associated with hydrologically stable conditions. Alternatively, hydrologically variable conditions were associated with multivoltine taxa that could extend the duration of subsidies with periodic emergence events throughout the year. We also found that anthropogenic impacts decrease the frequency of individuals with adult flight but potentially extend the distance subsidies travel into the terrestrial ecosystem. Collectively, these results suggest that natural and anthropogenic gradients could affect aquatic insect subsidies by changing the trait composition of benthic macroinvertebrate communities. The conceptual framework and trait–environment relationships we present shows promise for understanding broad geographical patterns in linkages between ecosystems. 

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