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Boardman L. Cross-talk between low temperature and other environmental factors. CURRENT OPINION IN INSECT SCIENCE 2024; 63:101193. [PMID: 38490451 DOI: 10.1016/j.cois.2024.101193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 03/07/2024] [Accepted: 03/11/2024] [Indexed: 03/17/2024]
Abstract
Low temperatures are rarely experienced in isolation. The impacts of low temperatures on insects can be exacerbated or alleviated by the addition of other environmental factors, including, for example, desiccation, hypoxia, or infection. One way in which environmental factors can interact is through cross-talk where different factors enact common signaling pathways. In this review, I highlight the breadth of abiotic and biotic factors that can interact with low-temperature tolerance in both natural and artificial environments; and discuss some of the candidate pathways that are possibly responsible for cross-talk between several factors. Specifically, I discuss three interesting candidates: the neurohormone octopamine, circadian clock gene vrille, and microbes. Finally, I discuss applications of cross-talk studies, and provide recommendations for researchers.
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Affiliation(s)
- Leigh Boardman
- Department of Biological Sciences, University of Memphis, Memphis, TN 38152, USA.
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Poikela N, Laetsch DR, Hoikkala V, Lohse K, Kankare M. Chromosomal Inversions and the Demography of Speciation in Drosophila montana and Drosophila flavomontana. Genome Biol Evol 2024; 16:evae024. [PMID: 38482698 PMCID: PMC10972691 DOI: 10.1093/gbe/evae024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2024] [Indexed: 04/01/2024] Open
Abstract
Chromosomal inversions may play a central role in speciation given their ability to locally reduce recombination and therefore genetic exchange between diverging populations. We analyzed long- and short-read whole-genome data from sympatric and allopatric populations of 2 Drosophila virilis group species, Drosophila montana and Drosophila flavomontana, to understand if inversions have contributed to their divergence. We identified 3 large alternatively fixed inversions on the X chromosome and one on each of the autosomes 4 and 5. A comparison of demographic models estimated for inverted and noninverted (colinear) chromosomal regions suggests that these inversions arose before the time of the species split. We detected a low rate of interspecific gene flow (introgression) from D. montana to D. flavomontana, which was further reduced inside inversions and was lower in allopatric than in sympatric populations. Together, these results suggest that the inversions were already present in the common ancestral population and that gene exchange between the sister taxa was reduced within inversions both before and after the onset of species divergence. Such ancestrally polymorphic inversions may foster speciation by allowing the accumulation of genetic divergence in loci involved in adaptation and reproductive isolation inside inversions early in the speciation process, while gene exchange at colinear regions continues until the evolving reproductive barriers complete speciation. The overlapping X inversions are particularly good candidates for driving the speciation process of D. montana and D. flavomontana, since they harbor strong genetic incompatibilities that were detected in a recent study of experimental introgression.
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Affiliation(s)
- Noora Poikela
- Department of Biological and Environmental Science, University of Jyväskylä, FI-40014, Jyväskylä, Finland
| | - Dominik R Laetsch
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Ville Hoikkala
- Department of Biological and Environmental Science, University of Jyväskylä, FI-40014, Jyväskylä, Finland
| | - Konrad Lohse
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Maaria Kankare
- Department of Biological and Environmental Science, University of Jyväskylä, FI-40014, Jyväskylä, Finland
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Gonzalez VH, Manweiler R, Smith AR, Oyen K, Cardona D, Wcislo WT. Low heat tolerance and high desiccation resistance in nocturnal bees and the implications for nocturnal pollination under climate change. Sci Rep 2023; 13:22320. [PMID: 38102400 PMCID: PMC10724170 DOI: 10.1038/s41598-023-49815-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 12/12/2023] [Indexed: 12/17/2023] Open
Abstract
Predicting insect responses to climate change is essential for preserving ecosystem services and biodiversity. Due to high daytime temperatures and low humidity levels, nocturnal insects are expected to have lower heat and desiccation tolerance compared to diurnal species. We estimated the lower (CTMin) and upper (CTMax) thermal limits of Megalopta, a group of neotropical, forest-dwelling bees. We calculated warming tolerance (WT) as a metric to assess vulnerability to global warming and measured survival rates during simulated heatwaves and desiccation stress events. We also assessed the impact of body size and reproductive status (ovary area) on bees' thermal limits. Megalopta displayed lower CTMin, CTMax, and WTs than diurnal bees (stingless bees, orchid bees, and carpenter bees), but exhibited similar mortality during simulated heatwave and higher desiccation tolerance. CTMin increased with increasing body size across all bees but decreased with increasing body size and ovary area in Megalopta, suggesting a reproductive cost or differences in thermal environments. CTMax did not increase with increasing body size or ovary area. These results indicate a greater sensitivity of Megalopta to temperature than humidity and reinforce the idea that nocturnal insects are thermally constrained, which might threaten pollination services in nocturnal contexts during global warming.
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Affiliation(s)
- Victor H Gonzalez
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA.
| | - Rachel Manweiler
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA
| | - Adam R Smith
- Department of Biological Sciences, George Washington University, Washington, District of Columbia, USA
| | - Kennan Oyen
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, 99164, USA
| | - David Cardona
- Smithsonian Tropical Research Institute, Panama, Republic of Panama
| | - William T Wcislo
- Smithsonian Tropical Research Institute, Panama, Republic of Panama
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Morgan-Richards M, Marshall CJ, Biggs PJ, Trewick SA. Insect Freeze-Tolerance Downunder: The Microbial Connection. INSECTS 2023; 14:89. [PMID: 36662017 PMCID: PMC9860888 DOI: 10.3390/insects14010089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 01/10/2023] [Accepted: 01/10/2023] [Indexed: 06/17/2023]
Abstract
Insects that are freeze-tolerant start freezing at high sub-zero temperatures and produce small ice crystals. They do this using ice-nucleating agents that facilitate intercellular ice growth and prevent formation of large crystals where they can damage tissues. In Aotearoa/New Zealand the majority of cold adapted invertebrates studied survive freezing at any time of year, with ice formation beginning in the rich microbiome of the gut. Some freeze-tolerant insects are known to host symbiotic bacteria and/or fungi that produce ice-nucleating agents and we speculate that gut microbes of many New Zealand insects may provide ice-nucleating active compounds that moderate freezing. We consider too the possibility that evolutionary disparate freeze-tolerant insect species share gut microbes that are a source of ice-nucleating agents and so we describe potential transmission pathways of shared gut fauna. Despite more than 30 years of research into the freeze-tolerant mechanisms of Southern Hemisphere insects, the role of exogenous ice-nucleating agents has been neglected. Key traits of three New Zealand freeze-tolerant lineages are considered in light of the supercooling point (temperature of ice crystal formation) of microbial ice-nucleating particles, the initiation site of freezing, and the implications for invertebrate parasites. We outline approaches that could be used to investigate potential sources of ice-nucleating agents in freeze-tolerant insects and the tools employed to study insect microbiomes.
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Affiliation(s)
- Mary Morgan-Richards
- Wildlife & Ecology Group, School of Natural Sciences, Massey University Manawatu, Palmerston North 4410, New Zealand
| | - Craig J. Marshall
- Department of Biochemistry, University of Otago, Dunedin 9016, New Zealand
| | - Patrick J. Biggs
- Molecular Biosciences, School of Natural Sciences, Massey University Manawatu, Palmerston North 4410, New Zealand
| | - Steven A. Trewick
- Wildlife & Ecology Group, School of Natural Sciences, Massey University Manawatu, Palmerston North 4410, New Zealand
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Gonzalez VH, Oyen K, Vitale N, Ospina R. Neotropical stingless bees display a strong response in cold tolerance with changes in elevation. CONSERVATION PHYSIOLOGY 2022; 10:coac073. [PMID: 36570736 PMCID: PMC9773376 DOI: 10.1093/conphys/coac073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 10/25/2022] [Accepted: 11/09/2022] [Indexed: 06/17/2023]
Abstract
Tropical pollinators are expected to experience substantial effects due to climate change, but aspects of their thermal biology remain largely unknown. We investigated the thermal tolerance of stingless honey-making bees, the most ecologically, economically and culturally important group of tropical pollinators. We assessed changes in the lower (CTMin) and upper (CTMax) critical thermal limits of 17 species (12 genera) at two elevations (200 and 1500 m) in the Colombian Andes. In addition, we examined the influence of body size (intertegular distance, ITD), hairiness (thoracic hair length) and coloration (lightness value) on bees' thermal tolerance. Because stingless beekeepers often relocate their colonies across the altitudinal gradient, as an initial attempt to explore potential social responses to climatic variability, we also tracked for several weeks brood temperature and humidity in nests of three species at both elevations. We found that CTMin decreased with elevation while CTMax was similar between elevations. CTMin and CTMax increased (low cold tolerance and high heat tolerance) with increasing ITD, hair length and lightness value, but these relationships were weak and explained at most 10% of the variance. Neither CTMin nor CTMax displayed significant phylogenetic signal. Brood nest temperature tracked ambient diel variations more closely in the low-elevation site, but it was constant and higher at the high-elevation site. In contrast, brood nest humidity was uniform throughout the day regardless of elevation. The stronger response in CTMin, and a similar CTMax between elevations, follows a pattern of variation documented across a wide range of taxa that is commonly known as the Brett's heat-invariant hypothesis. Our results indicate differential thermal sensitivities and potential thermal adaptations to local climate, which support ongoing conservation policies to restrict the long-distance relocations of colonies. They also shed light on how malleable nest thermoregulation can be across elevations.
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Affiliation(s)
- Victor H Gonzalez
- Corresponding author: Undergraduate Biology Program and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA.
| | - Kennan Oyen
- Department of Biological Sciences, McMicken College of Arts and Sciences, University of Cincinnati, 318 College Drive, Cincinnati, OH, 45221, USA
| | - Nydia Vitale
- Instituto Argentino de Investigaciones de las Zonas Áridas, CONICET, Mendoza, 5500, Argentina
| | - Rodulfo Ospina
- Laboratorio de Investigaciones en Abejas, Universidad Nacional de Colombia, Santa Fé de Bogotá, 111321, Colombia
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Himmel NJ, Sakurai A, Donaldson KJ, Cox DN. Protocols for measuring cold-evoked neural activity and cold tolerance in Drosophila larvae following fictive cold acclimation. STAR Protoc 2022; 3:101510. [PMID: 35776643 PMCID: PMC9253850 DOI: 10.1016/j.xpro.2022.101510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 05/02/2022] [Accepted: 06/09/2022] [Indexed: 11/25/2022] Open
Abstract
Here, we outline protocols to study cold acclimation in Drosophila from a neurobiological perspective, starting with fictive cold acclimation using a custom-built optogenetics-housing apparatus we call the OptoBox. We also provide detailed steps for single-unit electrophysiological recordings from larval cold nociceptors and a high-throughput cold-tolerance assay. These protocols expand the toolkit for the study of insect cold acclimation and nociception. For complete details on the use and execution of this protocol, please refer to Himmel et al. (2021).
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Affiliation(s)
- Nathaniel J Himmel
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Akira Sakurai
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Kevin J Donaldson
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Daniel N Cox
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA.
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