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1. Seeking compromise across competing goals in conservation translocations: The case of the ‘extinct’ Floreana Island Galapagos giant tortoise

   https://doi.org/10.1111/1365-2664.13516  

   Hunter, Elizabeth A. ; Gibbs, James P. ; Cayot, Linda J. ; Tapia, Washington ; Quinzin, Maud C. ; Miller, Joshua M. ; Caccone, Adalgisa ; Shoemaker, Kevin T. ; Rhodes, ed., Jonathan ( October 2019 , Journal of Applied Ecology)

   Conservation translocation projects must carefully balance multiple, potentially competing objectives (e.g. population viability, retention of genetic diversity, delivery of key ecological services) against conflicting stakeholder values and severe time and cost constraints. Advanced decision support tools would facilitate identifying practical solutions.

   We examined how to achieve compromise across competing objectives in conservation translocations via an examination of giant tortoises in the Galapagos Islands with ancestry from the extinct Floreana Island species (Chelonoidis niger). Efforts have begun to populate Floreana Island with tortoises genetically similar to its historical inhabitants while balancing three potentially competing objectives – restoring ecosystem services (sustaining a high tortoise population size), maximizing genome representation of the extinctC. nigerspecies and maintaining a genetically diverse population – under realistic cost constraints.

   We developed a novel approach to this conservation decision problem by coupling an individual‐based simulation model with generalized additive models and global optimization. We identified several incompatibilities among programme objectives, with quasi‐optimal single‐objective solutions (sets of management actions) differing substantially in programme duration, translocation age, incubation temperature (determinant of sex ratio) and the number of individuals directly translocated from the source population.

   Quasi‐optimal single‐objective solutions were able to produce outcomes (i.e. population size and measures of genetic diversity andC. nigergenome representation) to within 75% of their highest simulated outcomes (e.g. highest population size achieved across all simulations) within a cost constraint ofc. $2m USD, but these solutions resulted in severe declines (up to 74% reduction) in outcomes for non‐focal objectives. However, when all programme objectives were equally weighted to produce a multi‐objective solution, all objectives were met to within 90% of the highest achievable mean values across all cost constraints.

   Synthesis and applications. Multi‐objective conservation translocations are likely to encounter complex trade‐offs and conflicts among programme objectives. Here, we developed a novel combination of modelling approaches to identify optimal management strategies. We found that solutions that simultaneously addressed multiple, competing objectives performed better than single‐objective solutions. Our model‐based decision support tool demonstrates that timely, cost‐effective solutions can be identified in cases where management objectives appear to be incompatible.

    

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2. Ecoimmunological differences among congeneric tortoises in the United States

   https://doi.org/10.1111/jzo.13109  

   Sandmeier, F. C. ; Morales, J. ; Gomez, M. ; Kester, M. ; Gann‐Archuleta, K. ; Crooker, C. ; Goessling, J. M. ; Tracy, C. R. ; Weitzman, C. L. ( August 2023 , Journal of Zoology)

   Comparative studies, especially of related species that span across ecoregions, have the potential to increase our understanding of different ecological or evolutionary pressures that may drive host–pathogen dynamics. We quantified differences in immune investment, via differential leukocyte counts and bacteria‐killing assays, across four closely related species ofGopherustortoises, found across a gradient from the desert southwest to the subtropical southeast of the United States. We further quantified differences in a commensal nasal microbe (Pasteurella testudinis) and tested for associations among immune measures,P. testudinis, and previously quantified levels of the pathogenMycoplasma agassiziiand upper respiratory tract disease (URTD). We also evaluated the potential influence of environmental variables on immune investment,P. testudinis, and disease. We found that tortoise species in more arid environments had a reduced investment in inflammatory leukocytes, possibly as a strategy to reduce water loss, and invested more heavily in innate anti‐inflammatory leukocytes. Conversely, we found that species in moister, resource‐rich environments may face greater pathogen pressure, likely due to increased population densities and transmission rates among host tortoises. These tortoises had increased investment in inflammatory cells and appeared to reduce their nasal microbes (includingP. testudinis) when they exhibited URTD. Thus, we quantified two negative correlational patterns: (1) between inflammatory responses and water conservation and (2) between resource quality and transmission rates. We hypothesize that these relationships across species may reflect variable development or evolution of innate immune functions.

    

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3. Anaerobic fungi in the tortoise alimentary tract illuminate early stages of host-fungal symbiosis and Neocallimastigomycota evolution

   https://doi.org/10.1038/s41467-024-47047-4  

   Pratt, Carrie J. ; Meili, Casey H. ; Jones, Adrienne L. ; Jackson, Darian K. ; England, Emma E. ; Wang, Yan ; Hartson, Steve ; Rogers, Janet ; Elshahed, Mostafa S. ; Youssef, Noha H. ( March 2024 , Nature Communications)

   Anaerobic gut fungi (AGF,Neocallimastigomycota) reside in the alimentary tract of herbivores. While their presence in mammals is well documented, evidence for their occurrence in non-mammalian hosts is currently sparse. Culture-independent surveys of AGF in tortoises identified a unique community, with three novel deep-branching genera representing >90% of sequences in most samples. Representatives of all genera were successfully isolated under strict anaerobic conditions. Transcriptomics-enabled phylogenomic and molecular dating analyses indicated an ancient, deep-branching position in the AGF tree for these genera, with an evolutionary divergence time estimate of 104-112 million years ago (Mya). Such estimates push the establishment of animal-Neocallimastigomycotasymbiosis from the late to the early Cretaceous. Further, tortoise-associated isolates (T-AGF) exhibited limited capacity for plant polysaccharides metabolism and lacked genes encoding several carbohydrate-active enzyme (CAZyme) families. Finally, we demonstrate that the observed curtailed degradation capacities and reduced CAZyme repertoire is driven by the paucity of horizontal gene transfer (HGT) in T-AGF genomes, compared to their mammalian counterparts. This reduced capacity was reflected in an altered cellulosomal production capacity in T-AGF. Our findings provide insights into the phylogenetic diversity, ecological distribution, evolutionary history, evolution of fungal-host nutritional symbiosis, and dynamics of genes acquisition inNeocallimastigomycota.

    

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4. Migration triggers in a large herbivore: Galápagos giant tortoises navigating resource gradients on volcanoes

   https://doi.org/10.1002/ecy.2658  

   Bastille‐Rousseau, Guillaume ; Yackulic, Charles B. ; Gibbs, James P. ; Frair, Jacqueline L. ; Cabrera, Freddy ; Blake, Stephen ( April 2019 , Ecology)

   To understand how migratory behavior evolved and to predict how migratory species will respond to global environmental change it is important to quantify the fitness consequences of intra‐ and inter‐individual variation in migratory behavior. Intra‐individual variation includes behavioral responses to changing environmental conditions and hence behavioral plasticity in the context of novel or variable conditions. Inter‐individual variation determines the degree of variation on which selection can act and the rate of evolutionary responses to changes in average and extreme environmental conditions. Here we focus on variation in the partial migratory behavior of giant Galápagos tortoises (Chelonoidisspp.) and its energetic consequences. We evaluate the extent and mechanisms by which tortoises adjust migration timing in response to varying annual environmental conditions, and integrate movement data within a bioenergetic model of tortoise migration to quantify the fitness consequences of migration timing. We find strong inter‐individual variation in the timing of migration, which was not affected by environmental conditions prevailing at the time of migration but rather by average expectations estimated from multi‐annual averaged conditions. This variation is associated with an average annual loss in efficiency of ~15% relative to optimal timing based on year‐specific conditions. These results point towards a limited ability of tortoises to adjust the timing of their migrations based on prevailing (and, by extension, future) conditions, suggesting that the adaptability of tortoise migratory behavior to changing conditions is predicated more by past “normal” conditions than responses to prevailing, changing conditions. Our work offers insights into the level of environmental‐tuning in migratory behavior and a general framework for future research across taxa.

    

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5. Red Imported Fire Ants Reduce Invertebrate Abundance, Richness, and Diversity in Gopher Tortoise Burrows

   https://doi.org/10.3390/d13010007  

   Epperson, Deborah M. ; Allen, Craig R. ; Hogan, Katharine F. ( January 2021 , Diversity)

   null (Ed.)

   Gopher Tortoise (Gopherus polyphemus) burrows support diverse commensal invertebrate communities that may be of special conservation interest. We investigated the impact of red imported fire ants (Solenopsis invicta) on the invertebrate burrow community at 10 study sites in southern Mississippi, sampling burrows (1998–2000) before and after bait treatments to reduce fire ant populations. We sampled invertebrates using an ant bait attractant for ants and burrow vacuums for the broader invertebrate community and calculated fire ant abundance, invertebrate abundance, species richness, and species diversity. Fire ant abundance in gopher tortoise burrows was reduced by >98% in treated sites. There was a positive treatment effect on invertebrate abundance, diversity, and species richness from burrow vacuum sampling which was not observed in ant sampling from burrow baits. Management of fire ants around burrows may benefit both threatened gopher tortoises by reducing potential fire ant predation on hatchlings, as well as the diverse burrow invertebrate community. Fire-ant management may also benefit other species utilizing tortoise burrows, such as the endangered Dusky Gopher Frog and Schaus swallowtail butterfly. This has implications for more effective biodiversity conservation via targeted control of the invasive fire ant at gopher tortoise burrows. 

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