Effective population sizes and migration rates in fragmented populations of an endangered insect (Coenagrion mercuriale: Odonata)

• Published in: The Journal of animal ecology Vol. 76; no. 4; pp. 790 - 800
• Main Authors: WATTS, PHILLIP C, SACCHERI, ILIK J, KEMP, STEPHEN J, THOMPSON, DAVID J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-07-2007; British Ecological Society; Blackwell Publishing Ltd; Blackwell
• Subjects: Animal and plant ecology; Animal ecology; Animal migration; Animal populations; Animal reproduction; Animal, plant and microbial ecology; Animals; Biological and medical sciences; capture-mark-recapture; Coenagrion mercuriale; conservation; Conservation biology; Conservation of Natural Resources; Demography; Ecological genetics; Ecology; Ecosystem; Endangered & extinct species; Estimation methods; Evolutionary genetics; Female; Fundamental and applied biological sciences. Psychology; General aspects; Genetic Drift; Genetic Variation; Genetics; Genetics, Population; Habitat conservation; Insecta; Insecta - genetics; Insects; Invertebrates; Male; migration; natural resource management; Odonata; Population Density; Population Dynamics; Population ecology; Population estimates; Population genetics; Population size; Selection, Genetic; Spatial Ecology; Beaulieu England; United Kingdom; UK; British Isles; British Isles, England, Hampshire, Southampton, Beaulieu; Genetic drift; Endangered species; Insecta; Conservation; Population number; Fragmentation; Capture recapture method; Arthropoda; Ne; capture-mark-recapture; migration; Population migration; Odonata; Invertebrata
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/j.1365-2656.2007.01249.x

1. Effective population sizes (Ne) and migration rates (m) are critical evolutionary parameters that impact on population survival and determine the relative influence of selection and genetic drift. While the parameter m is well-studied in animal populations, Ne remains challenging to measure and consequently is only rarely estimated, particularly in insect taxa. 2. We used demographic and genetic methods to estimate Ne and m in a fragmented population of the endangered damselfly Coenagrion mercuriale to better understand the contrast between genetic and field estimates of these parameters and also to identify the spatial scale over which populations may become locally adapted. 3. We found a contrast between demographic- and genetic-based estimates of these parameters, with the former apparently providing overestimates of Ne, owing to substantial underestimation of the variance in reproductive success, and the latter overestimating m, because spatial genetic structure is weak. 4. The overall Ne of sites within the population network at Beaulieu Heath, the largest C. mercuriale site in the UK, was estimated to vary between approximately 60 and 2700. 5. While Ne was not correlated with either the total numbers of adults (N) or the area of habitat, this parameter was always less than N, because of substantial variance in reproductive success. The ratio Ne/N varied between 0·006 and 0·42 and was generally larger in smaller populations, possibly representing some 'genetic compensation'. 6. From a simple genetic model and these data on Ne and m, it seems that populations of C. mercuriale have the potential to respond to localized spatial variation in selection and this would need to be considered for future genetic management of this endangered species.