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5 results on '"Barlow, Emily J."'

1. Ecological and genetic perspectives on dispersal in European shags (Phalacrocorax aristotelis)

Author

Barlow, Emily J.

Subjects
598.43, Population ecology, Population Dynamics, Shag (Bird)
Abstract

Dispersal is a fundamental ecological and evolutionary process that can create demographic and genetic linkage between neighbouring and distant locations, influencing the dynamics, structure and ultimately the persistence of populations. To understand observed population dynamics and structure and to predict future change, accurate and comprehensive data are required describing the pattern and magnitude of dispersal and gene flow across all relevant spatial scales. However, this is a major empirical challenge. In this thesis, I aimed to obtain comprehensive empirical data quantifying natal dispersal patterns and population genetic structure across multiple spatial scales using the European shag (Phalacrocorax aristotelis) as a model species. I used a combination of field observations of shags individually ringed on the Isle of May, Scotland and molecular genetic techniques to accomplish these aims. By locating adult shags that had been ringed as chicks on the Isle of May at their breeding locations across eastern Scotland, I demonstrated divergent dispersal distributions at small versus large spatial scales. Using both mitochondrial DNA markers and a newly developed set of microsatellite markers, I quantified population genetic structure across a pan-European scale. This was weak across both molecular markers suggesting a role for occasional effective long-distance dispersal. However, a suite of evolutionary forces besides gene flow can create observed population genetic structure. Therefore, I quantified population genetic structure across populations in eastern Scotland, and quantitatively linked this indirect estimate of gene flow with my direct field observations of dispersal. Dispersal parameters derived explicitly from field observations and the spatial organisation of populations were shown to strongly influence observed population genetic structure. Overall, these data demonstrate the need to utilise both field observations and genetic methods to comprehensively estimate the extent and effectiveness of dispersal and highlight the importance of accurately quantifying long-distance dispersal in particular for predicting future change.

Published
2011

2. Estimating dispersal distributions at multiple scales: within-colony and among-colony dispersal rates, distances and directions in European shags Phalacrocorax aristotelis

Author

Barlow, Emily J., Daunt, Francis, Wanless, Sarah, and Reid, Jane M.

Subjects
Ecology and Environment
Abstract

Knowledge of the rate, distance and direction of dispersal within and among breeding areas is required to understand and predict demographic and genetic connectivity and resulting population and evolutionary dynamics. However dispersal rates, and the full distributions of dispersal distances and directions, are rarely comprehensively estimated across all spatial scales relevant to wild populations. We used re-sightings of European Shags Phalacrocorax aristotelis colour-ringed as chicks on the Isle of May (IoM), UK, to quantify rates, distances and directions of dispersal from natal to subsequent breeding sites both within IoM (within-colony dispersal) and across 27 other breeding colonies covering 1045 km of coastline (among-colony dispersal). Additionally, we used non-breeding season surveys covering 895 km of coastline to estimate breeding season detection probability and hence potential bias in estimated dispersal parameters. Within IoM, 99.6% of individuals dispersed between their natal and observed breeding nest-site. The distribution of within-colony dispersal distances was right-skewed; mean distance was shorter than expected given random settlement within IoM, yet some individuals dispersed long distances within the colony. The distribution of within-colony dispersal directions was non-uniform but did not differ from expectation given the spatial arrangement of nest-sites. However, 10% of all 460 colour-ringed adults that were located breeding had dispersed to a different colony. The maximum observed dispersal distance (170 km) was much smaller than the maximum distance surveyed (690 km). The distribution of among-colony dispersal distances was again right-skewed. Among-colony dispersal was directional, and differed from random expectation and from the distribution of within-colony dispersal directions. Non-breeding season surveys suggested that the probability of detecting a colour-ringed adult at its breeding location was high in the northeastern UK (98%). Estimated dispersal rates and distributions were therefore robust to incomplete detection. Overall, these data demonstrate skewed and directionally divergent dispersal distributions across small (within-colony) and large (among-colony) scales, indicating that dispersal could create genetic and demographic connectivity within the study area.

Published
2013
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3. Weak large-scale population genetic structure in a philopatric seabird, the European shag Phalacrocorax aristotelis

Author

Barlow, Emily J., Daunt, Francis, Wanless, Sarah, Alvarez, David, Reid, Jane M., Cavers, Stephen, Barlow, Emily J., Daunt, Francis, Wanless, Sarah, Alvarez, David, Reid, Jane M., and Cavers, Stephen

Abstract

Quantifying population genetic structure is fundamental to testing hypotheses regarding gene flow, population divergence and dynamics across large spatial scales. In species with highly mobile life-history stages, where it is unclear whether such movements translate into effective dispersal among discrete philopatric breeding populations, this approach can be particularly effective. We used seven nuclear microsatellite loci and mitochondrial DNA (ND2) markers to quantify population genetic structure and variation across 20 populations (447 individuals) of one such species, the European Shag, spanning a large geographical range. Despite high breeding philopatry, rare cross-sea movements and recognized subspecies, population genetic structure was weak across both microsatellites and mitochondrial markers. Furthermore, although isolation-by-distance was detected, microsatellite variation provided no evidence that open sea formed a complete barrier to effective dispersal. These data suggest that occasional long-distance, cross-sea movements translate into gene flow across a large spatial scale. Historical factors may also have shaped contemporary genetic structure: cluster analyses of microsatellite data identified three groups, comprising colonies at southern, mid- and northern latitudes, and similar structure was observed at mitochondrial loci. Only one private mitochondrial haplotype was found among subspecies, suggesting that this current taxonomic subdivision may not be mirrored by genetic isolation.

Published
2011

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