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Fitness disadvantages to disrupted embryogenesis impose selection against suboptimal nest-site choice by female grass snakes, Natrix natrix (Colubridae)
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
2011 (English)In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 24, no 1, 177-183 p.Article in journal (Refereed) Published
Abstract [en]

Phenotypic traits of hatchling reptiles are strongly influenced by incubation regimes (e.g. of temperature and moisture), suggesting that maternal choice of suitable nest-sites should be under intense selection. Our laboratory incubation of 209 eggs (17 clutches) from wild-caught Swedish grass snakes (Natrix natrix) showed that scale abnormalities (half-scales on one side of the body, often reflecting lateral asymmetry in the number of ribs) occurred more frequently if eggs were incubated under cooler conditions. Especially at low incubation temperatures, individuals with scale asymmetries took longer to hatch than did symmetric conspecifics, were smaller in body length at hatching and were slower in trials of locomotor speed. Anti-predator tactics also covaried with scale asymmetry. These patterns suggest that individuals with asymmetric scales should have lower fitness and hence should rarely survive to adulthood in the wild. We tested this prediction by examining 201 field-collected snakes from museum collections. As predicted, scale asymmetries were seen primarily in small snakes, and rarely in larger animals. We interpret these data to suggest that scale asymmetries in this species offer an index of developmental instability and that fitness disadvantages to disrupted embryogenesis impose selection against suboptimal nest-site choice by females.

Place, publisher, year, edition, pages
2011. Vol. 24, no 1, 177-183 p.
Keyword [en]
asymmetry, development, embryo, oviparity, phenotypic
National Category
Biological Sciences
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-69708DOI: 10.1111/j.1420-9101.2010.02153.xISI: 000285418500017OAI: oai:DiVA.org:su-69708DiVA: diva2:478007
Note

authorCount :3

Available from: 2012-01-15 Created: 2012-01-15 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
Open this publication in new window or tab >>Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The onset of agriculture about 12,000 years ago has had a major influence on the biodiversity of plants and animals. Unfortunately, the rapid changes in agricultural practices that has occurred in recent times has negatively affected many farmland species. One such species is the grass snake (Natrix natrix), which has been reported to decline in many parts of Europe, including Sweden. The grass snake is unique, not only in that it is the most northerly distributed oviparous reptile in the world, but also because of its habit of using anthropogenic heat sources such as manure heaps and composts as nesting-sites. Unfortunately changes in manure management and abandonment of farmlands have resulted in a decline and fragmentation of these environments. This may pose a threat for the northernmost populations of the grass snake, because natural nests in these areas may not provide sufficient heat for the eggs to hatch. The eggs and embryos of reptiles are highly sensitive to incubation temperatures, which can influence not only hatching success but also many phenotypic traits in the hatchlings. In this thesis I used a series of laboratory and field experiments to investigate the importance of anthropogenic heat sources for the reproductive ecology of cold-climate populations of grass snakes.  More specifically, I aimed to investigate thermal regimes of nests and how they influence embryonic development and offspring traits associated with survival and fitness. The results showed that manure heaps and composts are significantly warmer than potential natural nests and that natural nests do not provide sufficient heat to sustain embryonic development. Further, manure heaps were warmer and more constant in temperature than composts, resulting in higher hatching success and earlier hatching in manure heaps. The higher thermal variability in composts increased the frequency of abnormalities that are likely to negatively affect survival and fitness. In conclusion, this thesis shows that the use of anthropogenic heat sources has enabled grass snakes to expand their range farther north than any other oviparous reptile and that the thermal dichotomy in the primary nesting environments used by grass snakes contribute to important life-history variation in this species. These findings have important implications for conservation of reptile populations in general and grass snakes in particular.  

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2016
Keyword
agriculture, anthropogenic, climate, embryonic development, incubation
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-125524 (URN)978-91-7649-307-6 (ISBN)
Public defence
2016-02-19, Vivi Täckholmsalen, Svante Arrhenius väg 20 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2016-01-27 Created: 2016-01-13 Last updated: 2017-02-23Bibliographically approved

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