Growing appreciation of biodiversity and the role of apex predators, along with the increasing popularity of multispecies and trophy-oriented angling, has elevated the status of gars—in particular, the Alligator Gar Atractosteus spatula—among anglers and biologists alike. As a result, considerable effort has been spent in recent years to gain a working knowledge of the biology and ecology of the species in order to advance science-based management. In January 2019, the Alligator Gar Technical Committee of the Southern Division of the American Fisheries Society hosted a symposium entitled “Advances in the Conservation and Management of North American Gars” to showcase the results of research and management efforts conducted throughout the species’ range. Fishery researchers and managers presented a diversity of works, furthering our understanding of population dynamics, stock assessment, genetics, hatchery practices and stocking, habitat use, and angler desires associated with Alligator Gar fisheries. In our *Corresponding author: nate.smith@tpwd.texas.gov Received May 13, 2019; accepted September 13, 2019 North American Journal of Fisheries Management © 2019 American Fisheries Society ISSN: 0275-5947 print / 1548-8675 online DOI: 10.1002/nafm.10369

Advances In Conservation and Management of the Alligator Gar: A Synthesis of Current Knowledge and Introduction to a Special Section

Posthatch Development of Otoliths and Daily Ring Genesis in Age-0 Spotted Gars

In ectotherm species, environmental temperature plays a key role in development, growth, and survival. Thus, determining how temperature affects fish populations is of utmost importance to accurately predict the risk of climate change over fisheries and aquaculture, critical to warrant nutrition and food security in the coming years. Here, the potential effects of abnormal thermal regimes (24, 28 and 32 °C; TR24, TR28, and TR32, respectively) exclusively applied during embryogenesis in tropical gar (Atractosteus tropicus) has been explored to decipher the potential consequences on hatching and growth from fertilization to 16 days post-fertilization (dpf), while effects on skeletal development and body morphology were explored at fertilization and 16 dpf. Egg incubation at higher temperatures induced an early hatching and mouth opening. A higher hatching rate was obtained in eggs incubated at 28 °C when compared to those at 24 °C. No differences were found in fish survival at 16 dpf, with values ranging from 84.89 to 88.86%, but increased wet body weight and standard length were found in larvae from TR24 and TR32 groups. Thermal regime during embryogenesis also altered the rate at which the skeletal development occurs. Larvae from the TR32 group showed an advanced skeletal development, with a higher development of cartilaginous structures at hatching but reduced at 16 dpf when compared with the TR24 and TR28 groups. Furthermore, this advanced skeletal development seemed to determine the fish body morphology. Based on biometric measures, a principal component analysis showed how along development, larvae from each thermal regime were clustered together, but with each population remaining clearly separated from each other. The current study shows how changes in temperature may induce craniofacial and morphological alterations in fish during early stages and contribute to understanding the possible effects of global warming in early development of fish and its ecological implications.

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Larval Development in Tropical Gar (Atractosteus tropicus) Is Dependent on the Embryonic Thermal Regime: Ecological Implications under a Climate Change Context

Unappreciated Cenozoic ecomorphological diversification of stem gars revealed by a new large species. Acta Palaeontologica Polonica 67 (X): xxx–xxx. The evolutionary history of gars, an ancient group of ray-finned fishes, is excellently documented in the fossil record. These fishes are notable for how little the anatomy of extant species differs from that of their earliest known relatives from over 150 million years ago. As such, the low species richness of the gar crown group is thought to reflect the diversity of this clade over most of their history. Here, I describe the skeleton of a new gar species from the Eocene Willwood Formation of Wyoming, USA. Numerous features, including a shortened skull, ornamented external cranial bones, and microteeth ally the new species with Cuneatini, an obscure clade of gars restricted to the Eocene of southwestern North America. Yet, Cuneatus maximus sp. nov. is more than twice as large as its closest relatives. The holotype of the new species preserves a partial palate, providing new information about the anatomy of this poorly known cranial region in cuneatins. Phylogenetic analysis of gars with the new species C. maximus included implies a diversification of cuneatins in North America following the Cretaceous/Paleogene extinction. The presence of large-bodied stem-gars in the Eocene Willwood Formation also suggests that the fish fauna of this region was reminiscent of present-day ones from the American southeast. The discovery of C. maximus emphasizes the propensity of the fossil record to significantly increase the diversity and biogeographic range of even the most depauperate lineages.

Unappreciated Cenozoic ecomorphological diversification of stem gars revealed by a new large species

Animal signals evolve in an ecological context. Locally adapting animal sexual signals can be especially important for initiating or reinforcing reproductive isolation during the early stages of speciation. Previous studies have demonstrated that dewlap colour in Anolis lizards can be highly variable between populations in relation to both biotic and abiotic adaptive drivers at relatively large geographical scales. Here, we investigated differentiation of dewlap coloration among habitat types at a small spatial scale, within multiple islands of the West Indies, to test the hypothesis that similar local adaptive processes occur over smaller spatial scales. We explored variation in dewlap coloration in the most widespread species of anole, Anolis sagrei, across three characteristic habitats spanning the Bahamas and the Cayman Islands, namely beach scrub, primary coppice forest and mangrove forest. Using reflectance spectrometry paired with supervised machine learning, we found significant differences in spectral properties of the dewlap between habitats within small islands, sometimes over very short distances. Passive divergence in dewlap phenotype associated with isolation‐by‐distance did not seem to explain our results. On the other hand, these habitat‐specific dewlap differences varied in magnitude and direction across islands, and thus, our primary test for adaptation—parallel responses across islands—was not supported. We suggest that neutral processes or selection could be involved in several ways, including sexual selection. Our results shed new light on the scale at which signal colour polymorphism can be maintained in the presence of gene flow, and the relative role of local adaptation and other processes in driving these patterns of dewlap colour variation across islands.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/jeb.14002

Dewlap colour variation in Anolis sagrei is maintained among habitats within islands of the West Indies

Using X-ray microtomography, we describe the ossification events during the larval development of a non-teleost actinopterygian species: the Cuban gar Atractosteus tristoechus from the order Lepisosteiformes. We provide a detailed developmental series for each anatomical structure, covering a large sequence of mineralization events going from an early stage (13 days post-hatching, 21mm total length) to an almost fully ossified larval stage (118dph or 87mm in standard length). With this work, we expect to bring new developmental data to be used in further comparative studies with other lineages of bony vertebrates. We also hope that the online publication of these twelve successive 3D reconstructions, fully flagged, will be an educational tool for all students in comparative anatomy.

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Raphaël Scherrer

Papers

MicroCT survey of larval skeletal mineralization in the Cuban gar Atractosteus tristoechus (Actinopterygii; Lepisosteiformes)

Dewlap colour variation in Anolis sagrei is maintained among habitats within islands of the West Indies