1
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Sabattini J, Bollazzi M. Herbivory by Atta vollenweideri: Reviewing the significance of grass-cutting ants as a pest of livestock. Front Insect Sci 2023; 3:1101445. [PMID: 38469484 PMCID: PMC10926485 DOI: 10.3389/finsc.2023.1101445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 03/17/2023] [Indexed: 03/13/2024]
Abstract
The grass-cutting ant Atta vollenweideri is well suited for studies examining the negative effect leaf-cutting ants have on livestock production in South American grasslands because they forage on the same plants as cattle. This study investigated the impact of A. vollenweideri on livestock production in Argentinean rangelands. First, we assessed A. vollenweideri herbivory rates and its economic injury level (EIL). Second, using satellite imagery in a region covering 15,000 ha, we estimated the percentage of this area that surpassed the calculated EIL. Results showed that A. vollenweideri consumed approximately 276 kg of dry plant weight/ha/year, foraging mostly on grasses (70%). Additionally, ants cut 25% of herbs and 5% of trees. In summer and autumn, ants consumed more grasses, while in winter and spring, herbs and trees were also significantly cut. Ants consumed 7% of the forage demand needed to raise a calf according to the management regime applied by farmers. Our calculated EIL (5.85 nests/ha) falls in the range of previous studies. Colonies were absent in 93.6% of the surveyed area, while their density was below the EIL in 6.2% of the area. A. vollenweideri populations surpassed the EIL in only 0.2% of the area, which corresponds to 2.6% of the locations holding colonies. These results question the perception that Atta leaf-cutting ants are a pest of livestock production. Although ants consume a small percentage of cattle's forage demand, evidence that ants and cattle are competing in the few cases in which density surpasses the EIL is arguable. First, grass-cutting ants are capable of consuming herbs and trees in addition to the grasses on which cattle mostly feed. Second, there is no evidence indicating that both are cutting the same plant portions when preferences overlap. Third, evidence suggests that ants are not displaced under high-pressure grazing regimes by cattle. In the countries where A. vollenweideri is present, decision makers have promulgated several acts making its control mandatory. It is time to revisit the pest status of A. vollenweideri and include the use of EIL as a control criterion.
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Affiliation(s)
- Julian Sabattini
- Consejo Nacional de Investigaciones Científicas y Técnicas, Cátedra de Ecología de los Sistemas Agropecuarios, Facultad de Ciencias Agropecuarias, Universidad Nacional de Entre Ríos, Oro Verde, Argentina
| | - Martin Bollazzi
- Entomología, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
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2
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Sabattini J, Reta J, Bugnon L, Cerrudo J, Sabattini R, Peñalva A, Bollazzi M, Paz M, Sturniolo F. AntVideoRecord: Autonomous system to capture the locomotor activity of leafcutter ants. HardwareX 2022; 11:e00270. [PMID: 35509933 PMCID: PMC9058706 DOI: 10.1016/j.ohx.2022.e00270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 01/10/2022] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
The leafcutter ants (LCA) are considered plague in a great part of the American continent, causing great damage in production fields. Knowing the locomotion and foraging rhythm in LCA on a continuous basis would imply a significant advance for ecological studies, fundamentally of animal behavior. However, studying the forage rhythm of LCA in the field involves a significant human effort. This also adds a risk of subjective results due to the operator fatigue. In this work a new development named 'AntVideoRecord' is proposed to address this issue. This device is a low-cost autonomous system that records videos of the LCA path in a fixed position. The device can be easily reproduced using the freely accessible source code provided. The evaluation of this novel device was successful because it has exceeded all the basic requirements in the field: record continuously for at least seven days, withstand high and low temperatures, capture acceptable videos during the day and night, and have a simple configuration protocol by mobile devices and laptops. It was possible to confirm the correct operation of the device, being able to record more than 1900 h in the field at different climate conditions and times of the day.
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Affiliation(s)
- J.A. Sabattini
- National Council for Scientific and Technical Research (CONICET), Chair of Ecology of Agricultural Systems, Faculty of Agronomy Sciences. National University of Entre Ríos (FCA-UNER), Route No. 11 km 10,5 Oro Verde, Entre Ríos, Argentina
| | - J.M. Reta
- Electronic and 3D Prototyping Laboratory, Faculty of Engineer, National University of Entre Ríos, Argentina
| | - L.A. Bugnon
- Research Institute for Signals, Systems and Computational Intelligence (UNL - CONICET), Argentina
| | - J.I. Cerrudo
- Electronic and 3D Prototyping Laboratory, Faculty of Engineer, National University of Entre Ríos, Argentina
| | - R.A. Sabattini
- National Council for Scientific and Technical Research (CONICET), Chair of Ecology of Agricultural Systems, Faculty of Agronomy Sciences. National University of Entre Ríos (FCA-UNER), Route No. 11 km 10,5 Oro Verde, Entre Ríos, Argentina
| | - A. Peñalva
- Electronic and 3D Prototyping Laboratory, Faculty of Engineer, National University of Entre Ríos, Argentina
| | - M. Bollazzi
- Entomologia, Facultad de Agronomía, Universidad de la República, Uruguay
| | - M.O. Paz
- Electronic Engineer. Development and Independent Professional, Entre Ríos, Argentina
| | - F. Sturniolo
- Research Institute for Signals, Systems and Computational Intelligence (UNL - CONICET), Argentina
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3
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Stolle E, Pracana R, López-Osorio F, Priebe MK, Hernández GL, Castillo-Carrillo C, Arias MC, Paris CI, Bollazzi M, Priyam A, Wurm Y. Recurring adaptive introgression of a supergene variant that determines social organization. Nat Commun 2022; 13:1180. [PMID: 35277489 PMCID: PMC8917144 DOI: 10.1038/s41467-022-28806-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 02/04/2022] [Indexed: 11/09/2022] Open
Abstract
Introgression has been proposed as an essential source of adaptive genetic variation. However, a key barrier to adaptive introgression is that recombination can break down combinations of alleles that underpin many traits. This barrier might be overcome in supergene regions, where suppressed recombination leads to joint inheritance across many loci. Here, we study the evolution of a large supergene region that determines a major social and ecological trait in Solenopsis fire ants: whether colonies have one queen or multiple queens. Using coalescent-based phylogenies built from the genomes of 365 haploid fire ant males, we show that the supergene variant responsible for multiple-queen colonies evolved in one species and repeatedly spread to other species through introgressive hybridization. This finding highlights how supergene architecture can enable a complex adaptive phenotype to recurrently permeate species boundaries.
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Affiliation(s)
- Eckart Stolle
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK. .,Leibniz Institute for the Analysis of Biodiversity Change (LIB), Zoological Research Museum Alexander Koenig, Bonn, Germany.
| | - Rodrigo Pracana
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK.
| | - Federico López-Osorio
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Marian K Priebe
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Gabriel Luis Hernández
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | | | - Maria Cristina Arias
- Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Carolina Ivon Paris
- Departamento Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Martin Bollazzi
- Entomología, Departamento de Protección Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Anurag Priyam
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Yannick Wurm
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK. .,Alan Turing Institute, London, UK.
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4
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Dahan RA, Grove NK, Bollazzi M, Gerstner BP, Rabeling C. Decoupled evolution of mating biology and social structure in Acromyrmex leaf-cutting ants. Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03113-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Abstract
Insect societies vary greatly in their social structure, mating biology, and life history. Polygyny, the presence of multiple reproductive queens in a single colony, and polyandry, multiple mating by females, both increase the genetic variability in colonies of eusocial organisms, resulting in potential reproductive conflicts. The co-occurrence of polygyny and polyandry in a single species is rarely observed across eusocial insects, and these traits have been found to be negatively correlated in ants. Acromyrmex leaf-cutting ants are well-suited for investigating the evolution of complex mating strategies because both polygyny and polyandry co-occur in this genus. We used microsatellite markers and parentage inference in five South American Acromyrmex species to study how different selective pressures influence the evolution of polygyny and polyandry. We show that Acromyrmex species exhibit independent variation in mating biology and social structure, and polygyny and polyandry are not necessarily negatively correlated within genera. One species, Acromyrmex lobicornis, displays a significantly lower mating frequency compared to others, while another species, A. lundii, appears to have reverted to obligate monogyny. These variations appear to have a small impact on average intra-colonial relatedness, although the biological significance of such a small effect size is unclear. All species show significant reproductive skew between patrilines, but there was no significant difference in reproductive skew between any of the sampled species. We find that the evolution of social structure and mating biology appear to follow independent evolutionary trajectories in different species. Finally, we discuss the evolutionary implications that mating biology and social structure have on life history evolution in Acromyrmex leaf-cutting ants.
Significance statement
Many species of eusocial insects have colonies with multiple queens (polygyny), or queens mating with multiple males (polyandry). Both behaviors generate potentially beneficial genetic diversity in ant colonies as well as reproductive conflict. The co-occurrence of both polygyny and polyandry in a single species is only known from few ant species. Leaf-cutting ants have both multi-queen colonies and multiply mated queens, providing a well-suited system for studying the co-evolutionary dynamics between mating behavior and genetic diversity in colonies of eusocial insects. We used microsatellite markers to infer the socio-reproductive behavior in five South American leaf-cutter ant species. We found that variation in genetic diversity in colonies was directly associated with the mating frequencies of queens, but not with the number of queens in a colony. We suggest that multi-queen nesting and mating frequency evolve independently of one another, indicating that behavioral and ecological factors other than genetic diversity contribute to the evolution of complex mating behaviors in leaf-cutting ants.
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5
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Bollazzi M, Römer D, Roces F. Carbon dioxide levels and ventilation in Acromyrmex nests: significance and evolution of architectural innovations in leaf-cutting ants. R Soc Open Sci 2021; 8:210907. [PMID: 34849241 PMCID: PMC8611346 DOI: 10.1098/rsos.210907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Abstract
Leaf-cutting ant colonies largely differ in size, yet all consume O2 and produce CO2 in large amounts because of their underground fungus gardens. We have shown that in the Acromyrmex genus, three basic nest morphologies occur, and investigated the effects of architectural innovations on nest ventilation. We recognized (i) serial nests, similar to the ancestral type of the sister genus Trachymyrmex, with chambers excavated along a vertical tunnel connecting to the outside via a single opening, (ii) shallow nests, with one/few chambers extending shallowly with multiple connections to the outside, and (iii) thatched nests, with an above-ground fungus garden covered with plant material. Ventilation in shallow and thatched nests, but not in serial nests, occurred via wind-induced flows and thermal convection. CO2 concentrations were below the values known to affect the respiration of the symbiotic fungus, indicating that shallow and thatched nests are not constrained by harmful CO2 levels. Serial nests may be constrained depending on the soil CO2 levels. We suggest that in Acromyrmex, selective pressures acting on temperature and humidity control led to nesting habits closer to or above the soil surface and to the evolution of architectural innovations that improved gas exchanges.
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Affiliation(s)
- Martin Bollazzi
- Entomología, Facultad de Agronomía, Universidad de la República, Av. Garzon 780, Montevideo 12900, Uruguay
| | - Daniela Römer
- Entomología, Facultad de Agronomía, Universidad de la República, Av. Garzon 780, Montevideo 12900, Uruguay
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, Würzburg 97074, Germany
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6
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Schrader L, Pan H, Bollazzi M, Schiøtt M, Larabee FJ, Bi X, Deng Y, Zhang G, Boomsma JJ, Rabeling C. Publisher Correction: Relaxed selection underlies genome erosion in socially parasitic ant species. Nat Commun 2021; 12:3821. [PMID: 34131141 PMCID: PMC8206357 DOI: 10.1038/s41467-021-23950-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Lukas Schrader
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark. .,Institute for Evolution and Biodiversity, University of Münster, Münster, Germany.
| | | | - Martin Bollazzi
- Entomología, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Morten Schiøtt
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Fredrick J Larabee
- Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | | | | | - Guojie Zhang
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.,BGI-Shenzhen, Shenzhen, China.,State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Jacobus J Boomsma
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Christian Rabeling
- Department of Biology, University of Rochester, Rochester, NY, USA. .,School of Life Sciences, Arizona State University, Tempe, AZ, USA.
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7
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Schrader L, Pan H, Bollazzi M, Schiøtt M, Larabee FJ, Bi X, Deng Y, Zhang G, Boomsma JJ, Rabeling C. Relaxed selection underlies genome erosion in socially parasitic ant species. Nat Commun 2021; 12:2918. [PMID: 34006882 PMCID: PMC8131649 DOI: 10.1038/s41467-021-23178-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 04/06/2021] [Indexed: 02/03/2023] Open
Abstract
Inquiline ants are highly specialized and obligate social parasites that infiltrate and exploit colonies of closely related species. They have evolved many times convergently, are often evolutionarily young lineages, and are almost invariably rare. Focusing on the leaf-cutting ant genus Acromyrmex, we compared genomes of three inquiline social parasites with their free-living, closely-related hosts. The social parasite genomes show distinct signatures of erosion compared to the host lineages, as a consequence of relaxed selective constraints on traits associated with cooperative ant colony life and of inquilines having very small effective population sizes. We find parallel gene losses, particularly in olfactory receptors, consistent with inquiline species having highly reduced social behavioral repertoires. Many of the genomic changes that we uncover resemble those observed in the genomes of obligate non-social parasites and intracellular endosymbionts that branched off into highly specialized, host-dependent niches.
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Affiliation(s)
- Lukas Schrader
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany.
| | | | - Martin Bollazzi
- Entomología, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Morten Schiøtt
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Fredrick J Larabee
- Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | | | | | - Guojie Zhang
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- BGI-Shenzhen, Shenzhen, China
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Jacobus J Boomsma
- Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Christian Rabeling
- Department of Biology, University of Rochester, Rochester, NY, USA.
- School of Life Sciences, Arizona State University, Tempe, AZ, USA.
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8
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Smith CC, Weber JN, Mikheyev AS, Roces F, Bollazzi M, Kellner K, Seal JN, Mueller UG. Landscape genomics of an obligate mutualism: Concordant and discordant population structures between the leafcutter ant Atta texana and its two main fungal symbiont types. Mol Ecol 2019; 28:2831-2845. [PMID: 31141257 DOI: 10.1111/mec.15111] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 03/10/2019] [Accepted: 03/11/2019] [Indexed: 12/22/2022]
Abstract
To explore landscape genomics at the range limit of an obligate mutualism, we use genotyping-by-sequencing (ddRADseq) to quantify population structure and the effect of host-symbiont interactions between the northernmost fungus-farming leafcutter ant Atta texana and its two main types of cultivated fungus. Genome-wide differentiation between ants associated with either of the two fungal types is of the same order of magnitude as differentiation associated with temperature and precipitation across the ant's entire range, suggesting that specific ant-fungus genome-genome combinations may have been favoured by selection. For the ant hosts, we found a broad cline of genetic structure across the range, and a reduction of genetic diversity along the axis of range expansion towards the range margin. This population-genetic structure was concordant between the ants and one cultivar type (M-fungi, concordant clines) but discordant for the other cultivar type (T-fungi). Discordance in population-genetic structures between ant hosts and a fungal symbiont is surprising because the ant farmers codisperse with their vertically transmitted fungal symbionts. Discordance implies that (a) the fungi disperse also through between-nest horizontal transfer or other unknown mechanisms, and (b) genetic drift and gene flow can differ in magnitude between each partner and between different ant-fungus combinations. Together, these findings imply that variation in the strength of drift and gene flow experienced by each mutualistic partner affects adaptation to environmental stress at the range margin, and genome-genome interactions between host and symbiont influence adaptive genetic differentiation of the host during range evolution in this obligate mutualism.
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Affiliation(s)
- Chad C Smith
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas
| | - Jesse N Weber
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas.,Department of Biological Sciences, University of Alaska, Anchorage, Alaska
| | | | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg, Würzburg, Germany
| | - Martin Bollazzi
- Section of Entomology, Universidad de la República, Montevideo, Uruguay
| | - Katrin Kellner
- Department of Biology, University of Texas at Tyler, Tyler, Texas
| | - Jon N Seal
- Department of Biology, University of Texas at Tyler, Tyler, Texas
| | - Ulrich G Mueller
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas
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9
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Römer D, Bollazzi M, Roces F. Carbon dioxide sensing in the social context: Leaf-cutting ants prefer elevated CO 2 levels to tend their brood. J Insect Physiol 2018; 108:40-47. [PMID: 29778905 DOI: 10.1016/j.jinsphys.2018.05.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/15/2018] [Accepted: 05/17/2018] [Indexed: 06/08/2023]
Abstract
Social insects show temperature and humidity preferences inside their nests to successfully rear brood. In underground nests, ants also encounter rising CO2 concentrations with increasing depth. It is an open question whether they use CO2 as a cue to decide where to place and tend the brood. Leaf-cutting ants do show CO2 preferences for the culturing of their symbiotic fungus. We evaluated their CO2 choices for brood placement in laboratory experiments. Workers of Acromyrmex lundii in the process of relocating brood were offered a binary choice consisting of two interconnected chambers with different CO2 concentrations. Values ranged from atmospheric to high concentrations of 4% CO2. The CO2 preferences shown by workers for themselves and for brood placement were assessed by quantifying the number of workers and relocated brood in each chamber. Ants showed clear CO2 preferences for brood placement. They avoided atmospheric levels, 1% and 4% CO2, and showed a preference for levels of 3%. This is the first report of CO2 preferences for the maintenance of brood in social insects. The observed preferences for brood location were independent of the workers' own CO2 preferences, since they showed no clear-cut pattern. Workers' CO2 preferences for brood maintenance were slightly higher than those reported for fungus culturing, although brood is reared in the same chambers as the fungus in leaf-cutting ant nests. Workers' choices for brood placement in natural nests are likely the result of competing preferences for other environmental factors more crucial for brood survival, aside from those for CO2.
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Affiliation(s)
- Daniela Römer
- Department of Behavioral Physiology and Sociobiology, Biocenter, Am Hubland, University of Würzburg, 97074 Würzburg, Germany; Unidad de Entomología, Departamento de Protección Vegetal, Facultad de Agronomía, Avda. Eugenio Garzon 780, Universidad de la República, 12900 Montevideo, Uruguay.
| | - Martin Bollazzi
- Unidad de Entomología, Departamento de Protección Vegetal, Facultad de Agronomía, Avda. Eugenio Garzon 780, Universidad de la República, 12900 Montevideo, Uruguay.
| | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biocenter, Am Hubland, University of Würzburg, 97074 Würzburg, Germany.
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10
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Mueller UG, Ishak HD, Bruschi SM, Smith CC, Herman JJ, Solomon SE, Mikheyev AS, Rabeling C, Scott JJ, Cooper M, Rodrigues A, Ortiz A, Brandão CRF, Lattke JE, Pagnocca FC, Rehner SA, Schultz TR, Vasconcelos HL, Adams RMM, Bollazzi M, Clark RM, Himler AG, LaPolla JS, Leal IR, Johnson RA, Roces F, Sosa-Calvo J, Wirth R, Bacci M. Biogeography of mutualistic fungi cultivated by leafcutter ants. Mol Ecol 2017; 26:6921-6937. [PMID: 29134724 DOI: 10.1111/mec.14431] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/19/2017] [Accepted: 10/04/2017] [Indexed: 01/03/2023]
Abstract
Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (Atta, Acromyrmex) range from Argentina to the United States, with the greatest species diversity in southern South America. We elucidate the biogeography of fungi cultivated by leafcutter ants using DNA sequence and microsatellite-marker analyses of 474 cultivars collected across the leafcutter range. Fungal cultivars belong to two clades (Clade-A and Clade-B). The dominant and widespread Clade-A cultivars form three genotype clusters, with their relative prevalence corresponding to southern South America, northern South America, Central and North America. Admixture between Clade-A populations supports genetic exchange within a single species, Leucocoprinus gongylophorus. Some leafcutter species that cut grass as fungicultural substrate are specialized to cultivate Clade-B fungi, whereas leafcutters preferring dicot plants appear specialized on Clade-A fungi. Cultivar sharing between sympatric leafcutter species occurs frequently such that cultivars of Atta are not distinct from those of Acromyrmex. Leafcutters specialized on Clade-B fungi occur only in South America. Diversity of Clade-A fungi is greatest in South America, but minimal in Central and North America. Maximum cultivar diversity in South America is predicted by the Kusnezov-Fowler hypothesis that leafcutter ants originated in subtropical South America and only dicot-specialized leafcutter ants migrated out of South America, but the cultivar diversity becomes also compatible with a recently proposed hypothesis of a Central American origin by postulating that leafcutter ants acquired novel cultivars many times from other nonleafcutter fungus-growing ants during their migrations from Central America across South America. We evaluate these biogeographic hypotheses in the light of estimated dates for the origins of leafcutter ants and their cultivars.
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Affiliation(s)
- Ulrich G Mueller
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Heather D Ishak
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Sofia M Bruschi
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.,Centro de Estudos de Insetos Sociais, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil
| | - Chad C Smith
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Jacob J Herman
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Scott E Solomon
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.,Centro de Estudos de Insetos Sociais, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil.,Department of Ecology & Evolutionary Biology, Rice University, Houston, TX, USA
| | - Alexander S Mikheyev
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.,Okinawa Institute of Science & Technology, Kunigami, Okinawa, Japan
| | - Christian Rabeling
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.,School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Jarrod J Scott
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Michael Cooper
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Andre Rodrigues
- Centro de Estudos de Insetos Sociais, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil
| | - Adriana Ortiz
- Universidad Nacional de Colombia, Medellin, Colombia
| | | | - John E Lattke
- Departamento de Zoologia, Universidade Federal do Paraná, Curitiba, Brazil
| | - Fernando C Pagnocca
- Centro de Estudos de Insetos Sociais, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil
| | - Stephen A Rehner
- Mycology and Nematology Genomic Diversity and Biology Laboratory, Beltsville, MD, USA
| | - Ted R Schultz
- Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | | | - Rachelle M M Adams
- Department of Evolution, Ecology & Organismal Biology, Museum of Biological Diversity, Columbus, OH, USA
| | - Martin Bollazzi
- Section of Entomology, Universidad de la República, Montevideo, Uruguay
| | - Rebecca M Clark
- Integrative Biology, University of California-Berkeley, Berkeley, CA, USA
| | - Anna G Himler
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.,Department of Biology, College of Idaho, Caldwell, ID, USA
| | - John S LaPolla
- Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Department of Biological Sciences, Towson University, Towson, MD, USA
| | - Inara R Leal
- Departamento de Botânica, Universidade Federal de Pernambuco, Recife, PE, Brazil
| | - Robert A Johnson
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg, Würzburg, Germany
| | | | - Rainer Wirth
- Department of Plant Ecology and Systematics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Maurício Bacci
- Centro de Estudos de Insetos Sociais, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil
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Römer D, Bollazzi M, Roces F. Carbon dioxide sensing in an obligate insect-fungus symbiosis: CO2 preferences of leaf-cutting ants to rear their mutualistic fungus. PLoS One 2017; 12:e0174597. [PMID: 28376107 PMCID: PMC5380341 DOI: 10.1371/journal.pone.0174597] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 03/10/2017] [Indexed: 11/19/2022] Open
Abstract
Defense against biotic or abiotic stresses is one of the benefits of living in symbiosis. Leaf-cutting ants, which live in an obligate mutualism with a fungus, attenuate thermal and desiccation stress of their partner through behavioral responses, by choosing suitable places for fungus-rearing across the soil profile. The underground environment also presents hypoxic (low oxygen) and hypercapnic (high carbon dioxide) conditions, which can negatively influence the symbiont. Here, we investigated whether workers of the leaf-cutting ant Acromyrmex lundii use the CO2 concentration as an orientation cue when selecting a place to locate their fungus garden, and whether they show preferences for specific CO2 concentrations. We also evaluated whether levels preferred by workers for fungus-rearing differ from those selected for themselves. In the laboratory, CO2 preferences were assessed in binary choices between chambers with different CO2 concentrations, by quantifying number of workers in each chamber and amount of relocated fungus. Leaf-cutting ants used the CO2 concentration as a spatial cue when selecting places for fungus-rearing. A. lundii preferred intermediate CO2 levels, between 1 and 3%, as they would encounter at soil depths where their nest chambers are located. In addition, workers avoided both atmospheric and high CO2 levels as they would occur outside the nest and at deeper soil layers, respectively. In order to prevent fungus desiccation, however, workers relocated fungus to high CO2 levels, which were otherwise avoided. Workers' CO2 preferences for themselves showed no clear-cut pattern. We suggest that workers avoid both atmospheric and high CO2 concentrations not because they are detrimental for themselves, but because of their consequences for the symbiotic partner. Whether the preferred CO2 concentrations are beneficial for symbiont growth remains to be investigated, as well as whether the observed preferences for fungus-rearing influences the ants' decisions where to excavate new chambers across the soil profile.
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Affiliation(s)
- Daniela Römer
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, Würzburg, Germany
- Unidad de Entomología, Departamento de Protección Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
- * E-mail:
| | - Martin Bollazzi
- Unidad de Entomología, Departamento de Protección Vegetal, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay
| | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, Würzburg, Germany
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12
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Bollazzi M, Roces F. Information needs at the beginning of foraging: grass-cutting ants trade off load size for a faster return to the nest. PLoS One 2011; 6:e17667. [PMID: 21408014 PMCID: PMC3052370 DOI: 10.1371/journal.pone.0017667] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 02/09/2011] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Acquisition of information about food sources is essential for animals that forage collectively like social insects. Foragers deliver two commodities to the nest, food and information, and they may favor the delivery of one at the expenses of the other. We predict that information needs should be particularly high at the beginning of foraging: the decision to return faster to the nest will motivate a grass-cutting ant worker to reduce its loading time, and so to leave the source with a partial load. PRINCIPAL FINDINGS Field results showed that at the initial foraging phase, most grass-cutting ant foragers (Acromyrmex heyeri) returned unladen to the nest, and experienced head-on encounters with outgoing workers. Ant encounters were not simply collisions in a probabilistic sense: outgoing workers contacted in average 70% of the returning foragers at the initial foraging phase, and only 20% at the established phase. At the initial foraging phase, workers cut fragments that were shorter, narrower, lighter and tenderer than those harvested at the established one. Foragers walked at the initial phase significantly faster than expected for the observed temperatures, yet not at the established phase. Moreover, when controlling for differences in the fragment-size carried, workers still walked faster at the initial phase. Despite the higher speed, their individual transport rate of vegetable tissue was lower than that of similarly-sized workers foraging later at the same patch. CONCLUSIONS/SIGNIFICANCE At the initial foraging phase, workers compromised their individual transport rates of material in order to return faster to the colony. We suggest that the observed flexible cutting rules and the selection of partial loads at the beginning of foraging are driven by the need of information transfer, crucial for the establishment and maintenance of a foraging process to monopolize a discovered resource.
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Affiliation(s)
- Martin Bollazzi
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Würzburg, Germany
- Department of Entomology, Faculty of Agronomy, Universidad de la República, Montevideo, Uruguay
- Centro Universitario de Rivera, Universidad de la República, Rivera, Uruguay
| | - Flavio Roces
- Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Würzburg, Germany
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14
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Bollazzi M, Roces F. The thermoregulatory function of thatched nests in the South American grass-cutting ant, Acromyrmex heyeri. J Insect Sci 2010; 10:137. [PMID: 20883129 PMCID: PMC3016983 DOI: 10.1673/031.010.13701] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2009] [Accepted: 07/01/2009] [Indexed: 05/29/2023]
Abstract
The construction of mound-shaped nests by ants is considered as a behavioral adaptation to low environmental temperatures, i.e., colonies achieve higher and more stables temperatures than those of the environment. Besides the well-known nests of boreal Formica wood-ants, several species of South American leaf-cutting ants of the genus Acromyrmex construct thatched nests. Acromyrmex workers import plant fragments as building material, and arrange them so as to form a thatch covering a central chamber, where the fungus garden is located. Thus, the degree of thermoregulation attained by the fungus garden inside the thatched nest largely depends on how the thatch affects the thermal relations between the fungus and the environment. This work was aimed at studying the thermoregulatory function of the thatched nests built by the grass-cutting ant Acromyrmex heyeri Forel (Hymenoptera: Formicidae: Myrmicinae). Nest and environmental temperatures were measured as a function of solar radiation on the long-term. The thermal diffusivity of the nest thatch was measured and compared to that of the surrounding soil, in order to assess the influence of the building material on the nest's thermoregulatory ability. The results showed that the average core temperature of thatched nests was higher than that of the environment, but remained below values harmful for the fungus. This thermoregulation was brought about by the low thermal diffusivity of the nest thatch built by workers with plant fragments, instead of the readily-available soil particles that have a higher thermal diffusivity. The thatch prevented diurnal nest overheating by the incoming solar radiation, and avoided losses of the accumulated daily heat into the cold air during the night. The adaptive value of thatching behavior in Acromyrmex leaf-cutting ants occurring in the southernmost distribution range is discussed.
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Affiliation(s)
- Martin Bollazzi
- Department of Behavioural Physiology and Sociobiology (Zoology II), Biocenter, University of Würzburg
| | - Flavio Roces
- Department of Behavioural Physiology and Sociobiology (Zoology II), Biocenter, University of Würzburg
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Bollazzi M, Roces F. To build or not to build: circulating dry air organizes collective building for climate control in the leaf-cutting ant Acromyrmex ambiguus. Anim Behav 2007. [DOI: 10.1016/j.anbehav.2007.02.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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