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Diversity and relatedness enhance survival in colour polymorphic grasshoppers
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.ORCID iD: 0000-0001-9598-7618
2010 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 5, article id e10880Article in journal (Refereed) Published
Abstract [en]

Evolutionary theory predicts that different resource utilization and behaviour by alternative phenotypes may reduce competition and enhance productivity and individual performance in polymorphic, as compared with monomorphic, groups of individuals. However, firm evidence that members of more heterogeneous groups benefit from enhanced survival has been scarce or lacking. Furthermore, benefits associated with phenotypic diversity may be counterbalanced by costs mediated by reduced relatedness, since closely related individuals typically are more similar. Pygmy grasshoppers (Tetrix subulata) are characterized by extensive polymorphism in colour pattern, morphology, behaviour and physiology. We studied experimental groups founded by different numbers of mothers and found that survival was higher in low than in high density, that survival peaked at intermediate colour morph diversity in high density, and that survival was independent of diversity in low density where competition was less intense. We further demonstrate that survival was enhanced by relatedness, as expected if antagonistic and competitive interactions are discriminately directed towards non-siblings. We therefore also performed behavioural observations and staged encounters which confirmed that individuals recognized and responded differently to siblings than to non-siblings. We conclude that negative effects associated with competition are less manifest in diverse groups, that there is conflicting selection for and against genetic diversity occurring simultaneously, and that diversity and relatedness may facilitate the productivity and ecological success of groups of interacting individuals.

Place, publisher, year, edition, pages
2010. Vol. 5, no 5, article id e10880
National Category
Biological Sciences Ecology
Research subject
Ecology, Evolutionary Biology
Identifiers
URN: urn:nbn:se:lnu:diva-6046DOI: 10.1371/journal.pone.0010880Scopus ID: 2-s2.0-77956542364OAI: oai:DiVA.org:lnu-6046DiVA, id: diva2:323520
Available from: 2010-06-11 Created: 2010-06-11 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Evolution in changing environments revealed by fire melanism in pygmy grasshopper
Open this publication in new window or tab >>Evolution in changing environments revealed by fire melanism in pygmy grasshopper
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

According to theory, genetic diversity can be maintained by environmental variation and the degree of genetic and phenotypic polymorphism may enhance the ability of populations to endure stress imposed by changing environments. In my thesis I used colour polymorphic pygmy grasshoppers (Tetrix subulata) as a model system to explore how environmental variation influenced genetic diversity. I compared population colour morph frequencies between populations in burnt and non-burnt areas and performed experiments to investigate to what extent colour patterns in these insects are determined by genes and influenced by phenotypic plasticity in response to environmental effects experienced during development. My results showed that the frequency of black individuals on average was much higher in recently fire ravaged areas, a condition known as fire melanism. The highest proportion of black individuals was reached within the first year after a fire. After the initial increase, the proportion of black individuals declined again and the distribution among alternative colour morphs became more even. Data for individuals raised in captivity revealed a high correspondence between maternal and offspring colour patterns, indicating a strong genetic influence on colour. Additional experiments demonstrated that the development of colour patterns in pygmy grasshoppers was not influenced by burnt material or high population densities, two environmental cues associated with post fire environments.

To test if reduced competition among alternative colour morphs may contribute to the maintenance of colour pattern polymorphism in these insects I examined if average survival was higher in diverse compared to homogeneous groups of individuals. I found that survival increased with colour pattern diversity, presumably due to reduced competition among alternative colour morphs. Relaxation of competition may explain why the distribution among alternative colour patterns changed and became more even after the initial evolution of fire melanism. My results demonstrate that environmental change may cause extremely rapid and reversible evolution, indicate that fluctuating selection may preserve genetic variation and support the notion that polymorphism may increase average individual success and enable populations to withstand environmental change.

 

Place, publisher, year, edition, pages
Linnaues University Press, 2010
Series
Linnaeus University Dissertations ; 5/2010
Keywords
Evolution Melanism Polymorphism Pygmy grasshoppers
National Category
Biological Sciences
Research subject
Natural Science, Evolutionary Biology
Identifiers
urn:nbn:se:hik:diva-2457 (URN)978-91-86491-05-5 (ISBN)
Public defence
2010-03-12, Fullriggaren, Landgången 4, Kalmar, 09:00 (English)
Opponent
Supervisors
Available from: 2010-01-20 Created: 2010-01-20 Last updated: 2013-03-22Bibliographically approved

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Caesar, SofiaKarlsson, MagnusForsman, Anders

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