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Cook JM. Sexual selection on population-level mating opportunities drives morph ratios in a fig wasp with extreme male dimorphism. BMC Ecol Evol 2021; 21:168. [PMID: 34488650 PMCID: PMC8422632 DOI: 10.1186/s12862-021-01898-3] [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: 10/01/2020] [Accepted: 08/23/2021] [Indexed: 12/02/2022] Open
Abstract
Background Alternative mating tactics are widespread in animals and associated with extreme morphological polymorphism in some insects. Some fig wasps have both highly modified wingless males and dispersing winged males. Wingless males mate inside figs before females disperse, while winged males mate elsewhere after dispersal. Hamilton proposed a model for this system with morphs determined by alternative alleles. This has an equilibrium where the proportion of winged males equals the proportion of females dispersing unmated; i.e. the proportion of matings that they obtain. Previously, we have shown qualitative support for this prediction across nine wing-dimorphic fig wasp species. Here I test the quantitative prediction in the fig wasp Pseudidarnes minerva. In addition, some fig wasp species that lack winged males, but have two wingless morphs, show a conditional strategy with morph determination influenced by the number of wasps developing in a patch. I also test for this alternative pattern in the wing-dimorphic P. minerva. Results I sampled 114 figs that contained a mean of 2.1 P. minerva wasps from 44 trees across four sites in Sydney, Australia. At the whole population level, the proportion of winged males (0.84 or 0.79 corrected for sampling bias) did not differ significantly from the proportion of unmated females (0.84), providing strong quantitative support for the prediction of Hamilton’s model. In addition, there was no evidence for other factors, such as local mate competition or fighting between wingless males, that could violate simplifying assumptions of the model. Meanwhile, the proportion of winged males was not correlated with the number of wasps per fig, providing no evidence for a conditional strategy. Conclusion The morph ratio in P. minerva is consistent with Hamilton’s simple Mendelian strategy model, where morph ratios are set by average mating opportunities at the population level. This contrasts with some fig wasps from another subfamily that show conditional morph determination, allowing finer scale adaptation to fig-level mating opportunities. However, these conditional cases do not involve wing polymorphism. Male polymorphism is common and variable in fig wasps and has evolved independently in multiple lineages with apparently different underlying mechanisms. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-021-01898-3.
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Affiliation(s)
- James M Cook
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
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Xiao J, Wei X, Zhou Y, Xin Z, Miao Y, Hou H, Li J, Zhao D, Liu J, Chen R, Niu L, Ma G, Zhen W, He S, Wang J, Wei X, Dou W, Sui Z, Zhang H, Xing S, Shi M, Huang D. Genomes of 12 fig wasps provide insights into the adaptation of pollinators to fig syconia. J Genet Genomics 2021; 48:225-236. [PMID: 34011484 DOI: 10.1016/j.jgg.2021.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/14/2021] [Accepted: 02/28/2021] [Indexed: 10/21/2022]
Abstract
Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism. The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources in the enclosed fig syconia implies that they are vulnerable to habitat changes. However, there is still no extensive genomic evidence to reveal the evolutionary footprint of this long-term mutually beneficial symbiosis in fig pollinators. In fig syconia, there are also non-pollinator species. The non-pollinator species differ in their evolutionary and life histories from pollinators. We conducted comparative analyses on 11 newly sequenced fig wasp genomes and one previously published genome. The pollinators colonized the figs approximately 66.9 million years ago, consistent with the origin of host figs. Compared with non-pollinators, many more genes in pollinators were subject to relaxed selection. Seven genes were absent in pollinators in response to environmental stress and immune activation. Pollinators had more streamlined gene repertoires in the innate immune system, chemosensory toolbox, and detoxification system. Our results provide genomic evidence for the differentiation between pollinators and nonpollinators. The data suggest that owing to the long-term adaptation to the fig, some genes related to functions no longer required are absent in pollinators.
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Affiliation(s)
- Jinhua Xiao
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China.
| | - Xianqin Wei
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yi Zhou
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zhaozhe Xin
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yunheng Miao
- Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hongxia Hou
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jiaxing Li
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Dan Zhao
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jing Liu
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Rui Chen
- Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Liming Niu
- Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
| | - Guangchang Ma
- Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
| | - Wenquan Zhen
- Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, College of Marine Sciences, Beibu Gulf University, Qinzhou 535011, China
| | - Shunmin He
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jianxia Wang
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Xunfan Wei
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Weihao Dou
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zhuoxiao Sui
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | | | - Shilai Xing
- Berry Genomics Corporation, Beijing 102206, China
| | - Miao Shi
- Berry Genomics Corporation, Beijing 102206, China
| | - Dawei Huang
- Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China; Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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