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Sõber V, Sandre SL, Esperk T, Teder T, Tammaru T. Ontogeny of sexual size dimorphism revisited: Females grow for a longer time and also faster. PLoS One 2019; 14:e0215317. [PMID: 31013286 PMCID: PMC6478289 DOI: 10.1371/journal.pone.0215317] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/29/2019] [Indexed: 11/18/2022] Open
Abstract
Sex-specific mechanisms of the determination of insect body sizes are insufficiently understood. Here we use the common heath moth, Ematurga atomaria (Lepidoptera: Geometridae) to examine how larval growth trajectories differ between males and females. We monitored the development of 1379 larvae in controlled laboratory conditions. Sexually dimorphic development times during the first four instars were associated with sexual size dimorphism (SSD) in the beginning of the fifth (last) instar, when females were on average 15% heavier than males. Similarly, the duration of the last instar was about 13% longer in females. Further, we specifically focussed on the estimates of differential (instantaneous) growth rates of the larvae based on 24h mass increments of the 2nd, 3rd, 4th and 5th day in the beginning of the last instar. We calculated ‘allometric’ differential growth rates as the per-day increase in cube-root-transformed mass of the larvae. We found that allometric growth rates were slightly but significantly larger in females than in males. As this measure of growth rate (in contrast to the relative growth rate, based on the ratio of masses recorded at consecutive measurements) did not depend on body size, it allows an unambiguous separation of the effects of sex and size. We conclude that in accordance with an emerging general pattern, larger female body size in E. atomaria is achieved primarily by means of a longer growth period. Furthermore, our study shows that the differential growth rate can also be sexually dimorphic and contribute to SSD. This contribution, however, is lower than that of the development time by an order of magnitude. In addition to development periods and growth rates, other parameters of the non-linear growth curves of insect larvae also need to be considered in the context of SSD determination. In particular, weight loss prior to pupation was shown to be considerably larger in females than in males.
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Affiliation(s)
- Virve Sõber
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
- * E-mail:
| | - Siiri-Lii Sandre
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Toomas Esperk
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Tiit Teder
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
- Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
| | - Toomas Tammaru
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
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Sandre SL, Kaart T, Morehouse N, Tammaru T. Weak and inconsistent associations between melanic darkness and fitness-related traits in an insect. J Evol Biol 2018; 31:1959-1968. [PMID: 30311708 DOI: 10.1111/jeb.13387] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/08/2018] [Indexed: 01/16/2023]
Abstract
The idea that the fitness value of body coloration may be affected by biochemically mediated trade-offs has received much research attention. For example, melanization is believed to interact with other fitness-related traits via competition for substrates, costs associated with the synthesis of melanin or pleiotropic effects of the involved genes. However, genetic correlations between coloration and fitness-related traits remain poorly understood. Here, we present a quantitative-genetic study of a coloration trait correlated to melanin-based cuticular darkness ('darkness', hereafter) in a geometrid moth, Ematurga atomaria. This species has considerable variation in larval appearance. We focus on correlations between larval darkness and fitness-related growth performance traits. Both a half-sib analysis and an 'animal model' approach revealed moderately high heritabilities of larval darkness and indices of growth performance. Heritability estimates of darkness derived from the animal model were, however, considerably higher than those based on the half-sib model suggesting that the determination of coloration includes genetic interactions and epigenetic effects. Importantly, on the host plant with the largest sample size, we found no evidence for either genetic or environmental correlations between darkness and growth parameters. On an alternative host plant, there was some indication of positive genetic and negative environmental correlation between these traits. This shows that respective relationships are environment-specific. Nevertheless, the overall pattern of weak and inconsistent correlations between larval coloration and growth parameters does not support universal trade-offs between these traits and suggests that physiological costs of producing colour patterns do not necessarily interfere with adaptive evolution of coloration.
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Affiliation(s)
- Siiri-Lii Sandre
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Tanel Kaart
- Department of Animal Breeding and Biotechnology, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Tartu, Estonia
| | - Nathan Morehouse
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Toomas Tammaru
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
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Vargas HA, Rasmann S, Ramirez-Verdugo P, Villagra CA. Lioptilodes friasi (Lepidoptera: Pterophoridae) Niche Breadth in the Chilean Mediterranean Matorral Biome: Trophic and Altitudinal Dimensions. NEOTROPICAL ENTOMOLOGY 2018; 47:62-68. [PMID: 28386773 DOI: 10.1007/s13744-017-0514-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 03/15/2017] [Indexed: 06/07/2023]
Abstract
Understanding the factors driving the diet breadth of phytophagous insects remains one of the main questions in ecological research. In this study we explored the diet breadth and plant-insect associations in the plume moth Lioptilodes friasi Vargas & Parra (Lepidoptera: Pterophoridae). This phytophagous insect was originally described in association with a single host species, Haplopappus foliosus (Asteraceae), a native shrub of the Chilean Mediterranean matorral. In order to address the breadth of host plant choice, we surveyed other Haplopappus species growing along the elevation gradient of central Chile from sea level to 2600 m. We were able to obtain L. friasi adults from five additional Haplopappus species: Haplopappus chrysantemifolius and Haplopappus decurrens from the coastal zone, Haplopappus multifolius and Haplopappus schumanii from the mid-elevation zone, and Haplopappus scrobiculatus at high elevation. Our results demonstrate that the genus-specialized endophagous herbivore L. friasi has a wider distribution and climatic tolerance than previously described. Its biogeographical range extends from the lowland coastal habitats up to the Andean subnival level. We propose that shared flower phenotypic traits such as morphology and chemical composition may have allowed the colonization of closely related Haplopappus species in central Chile, the expansion of which is limited by the harsh high elevation conditions.
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Affiliation(s)
- Héctor A Vargas
- Depto de Recursos Ambientales, Facultad de Ciencias Agronómicas, Univ de Tarapacá, Casilla 6-D, Arica, Chile.
| | - Sergio Rasmann
- Institute of Biology, Univ of Neuchâtel, Neuchâtel, Switzerland
| | | | - Cristian A Villagra
- Instituto de Entomología, Facultad de Ciencias Básicas, Univ Metropolitana de Ciencias de la Educación, Santiago, Chile
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Insect herbivory may cause changes in the visual properties of leaves and affect the camouflage of herbivores to avian predators. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2326-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Välimäki P, Kivelä SM, Raitanen J, Pakanen VM, Vatka E, Mäenpää MI, Keret N, Tammaru T. Larval melanism in a geometrid moth: promoted neither by a thermal nor seasonal adaptation but desiccating environments. J Anim Ecol 2015; 84:817-828. [PMID: 25581258 DOI: 10.1111/1365-2656.12330] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 12/17/2014] [Indexed: 11/27/2022]
Abstract
Spatiotemporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually nonexclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism. In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of nonmelanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae). Geographical variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the nonmelanic ones when both temperature and the level of incident radiation were high. Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forthcoming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism.
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Affiliation(s)
- Panu Välimäki
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Sami M Kivelä
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Jani Raitanen
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Veli-Matti Pakanen
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Emma Vatka
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Maarit I Mäenpää
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Netta Keret
- Department of Ecology, University of Oulu, PO Box 3000, Oulu, FI-90014, Finland
| | - Toomas Tammaru
- Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, EE-51014, Estonia
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