Molecular ecology and fitness of
striped (Stenella coeruleoalba, Meyen, 1833) and
common (Delphinus delphis, Linnaeus, 1758)
dolphins

Abstract

In this study the molecular ecology and fitness of two Delphinidae species, the striped dolphin (Stenella coeruleoalba) and the common dolphin (Delphinus delphis), were investigated in the Mediterranean Sea and Atlantic Ocean. This thesis provides a comparative assessment of the striped and the common dolphin, using molecular methods regarding the genomic diversity and parasite resistance.
The striped and the common dolphin have a world-wide distribution, inhabiting pelagic waters and differ with respect to population structure within the study area. The aim is to reveal different patterns of genetic diversity and fitness in the species that shows greater populations structure. In order to test this, my analyses structure was a) to analyse the population structure of the striped dolphin in the Mediterranean Sea and Atlantic Ocean and compare structuring patterns with previous published studies, b) to examine the heterozygosity fitness correlation for both species, using neutral and non-neutral markers and specific parasites that are important of animal’s health. In this context this study tests that local populations show stronger relationship between genetic diversity and fitness.
This study suggested that different methods regarding to power and studied subareas show a fine-scale structure beyond that reported previously in striped dolphin populations. A key new finding is the structuring pattern in the Atlantic Ocean, where populations from Scotland and the Biscay Gulf were isolated from the one in Ireland. Also, the Ionian Sea samples grouped with the western Mediterranean, which could either be an effect of the small sample size from the Ionian Sea, or reflect a boundary closer to Greece, dividing the basins of the Mediterranean for this species.
In this study I found differences between the two hosts with respect their genetic diversity and parasite loads for both nuclear and functional loci. I also found that evidence for a heterozygosity fitness correlation was strongest for females, and this was true both for the correlation with genomic diversity as assessed using neutral markers, and for the functional immune system gene. This observable association suggests that parasites may act as an energetic stress, and may reflect the non-identical pathogenesis of parasites and their ability to inflict damage through the hormone profiles. Results illustrate potentially important interactions between genetic drift and selection, and provide specific information that will be valuable towards the conservation and management of diversity in these species.