The evolutionary and behavioural ecology of a European lamprey species pair (Lampetra fluviatilis and L. planeri): conservation concerns and anthropogenic impacts

Abstract

Lampreys (Order Petromyzontiformes) have existed for over 365 million years and are considered the most ancient group of living vertebrates. Given the socio-economic, cultural, and ecological consequences of declining lamprey populations, it is imperative to address declines by implementing effective conservation management. This thesis explores the conservation issues affecting the European lamprey species pair Lampetra fluviatilis and Lampetra planeri and offers a holistic approach to their management and conservation in relation to anthropogenic impacts. The rapid development of small-scale hydropower provides substantial risk to migrating biota. At the site of an Archimedes screw turbine, damage rates to lampreys that passed through the screw were low (1.5%) and distinct seasonal, and diel, patterns of migration were exhibited by recently transformed juvenile and larval lampreys. Results indicated longer periods of impingement risk than expected. Cumulative potential impacts of multiple hydropower sites on downstream fish passage (including lampreys) should, however, be considered by regulatory agencies when planning hydropower development within catchments.

Anthropogenic barriers were also found to intensify differentiation between L. planeri populations and anadromous L. fluviatilis populations. Gene flow was consequently found to be asymmetric due to the barriers allowing downstream movement, whilst obstructing active upstream migration. Samples of 543 European river lamprey Lampetra fluviatilis and European brook lamprey Lampetra planeri from across 15 sites, primarily in the British Isles, were investigated for 829bp mtDNA sequence and 13 polymorphic microsatellite DNA loci. Contrasting patterns of population structure were found for mtDNA (which revealed no differentiation between species) and microsatellite DNA markers. Microsatellite markers revealed strong differentiation among freshwater-resident L. planeri populations, and between L. fluviatilis and L. planeri in most cases, but little structure was evident among anadromous L. fluviatilis populations. There is also evidence that there has been some degree of gene flow between L. fluviatilis and L. planeri since these populations were established. There is much debate as to whether lamprey paired-species constitute distinct species or are divergent ecotypes of a single polymorphic species. Overall, these findings are suggestive of multiple independent divergences of L. planeri from an anadromous ancestor (i.e. L. planeri are polyphyletic). Focus of conservation and management efforts, therefore, needs to be directed towards ensuring the longitudinal connectivity within rivers, and the continued existence of the specific habitats necessitated within lamprey life-cycles. Molecular techniques should be applied to identify genetically differentiated populations of freshwater-resident lampreys.Appropriate measures, such as, the designation of a network of Special Areas of Conservation (SACs), and recognising these populations as distinct Evolutionarily Significant Units, should also be implemented to ensure the survival of these populations.