Coming and going – Historical distributions of the European oyster Ostrea edulis Linnaeus, 1758 and the introduced slipper limpet Crepidula fornicata Linnaeus, 1758 in the North Sea

Abstract

Natural history collections are fundamental for biodiversity research as well as for any applied environment-related research. These collections can be seen as archives of earth´s life providing the basis to address highly relevant scientific questions such as how biodiversity changes in certain environments, either through evolutionary processes in a geological timescale, or by man-made transformation of habitats throughout the last decades and/or centuries. A prominent example is the decline of the European flat oyster Ostrea edulis Linneaus, 1758 in the North Sea and the concomitant invasion of the common limpet slipper Crepidula fornicata, which has been implicated to have negative effects on O. edulis. We used collections to analyse population changes in both species in the North Sea. In order to reconstruct the change in distribution and diversity over the past 200 years, we combined the temporal and spatial information recorded with the collected specimens contained in several European natural history collections. Our data recover the decline of O. edulis in the North Sea from the 19th century to the present and the process of invasion of C. fornicata. Importantly, the decline of O. edulis was nearly completed before C. fornicata appeared in the North Sea, suggesting that the latter had nothing to do with the local extinction of O. edulis in the North Sea.

Phylogeography in an “oyster” shell provides first insights into the genetic structure of an extinct Ostrea edulis population

“…The most astonishing result is the autochthonous haplogroup WS, which is based on eight individuals that were without exception collected from the near shore of the Danish and German Wadden Sea, where the European oyster went extinct in the 1930s 8 . Its restriction to the Wadden Sea may indicate local adaptation to the distinct environmental conditions of the Wadden Sea.…”

“…Subsequently, large translocation efforts were undertaken to sustain the local oyster beds 6 , 7 . These translocation efforts were unsuccessful in the Wadden Sea, where O. edulis went locally extinct in the 1930s 3 , 7 , 8 . The decline in the remaining range was further accelerated by introduced pathogens, which led to disease outbreaks in the late 1970s and early 1980s 3 , 8 – 11 .…”

“…Human activities and their consequences have certainly played a role in the massive decline in wild O. edulis populations, but the reasons for the complete extinction of the Wadden Sea population remain poorly understood 8 , 11 . Present-day phylogeographic studies aimed to create effective resettlement strategies and to support suitable conservation management plans for many species 12 – 14 .…”

The late Holocene demise of a sublittoral oyster bed in the North Sea

“…The data furthermore suggest that a good state of the historical oyster populations in the German Bight prior to the dawn of industrial fisheries in the late 19 th /early 20 th century may stand less clear [e.g. 4 , 15 , 23 ] and that ideal habitat conditions for the restoration of O . edulis cannot be inferred from the historical/early industrial state of the North Sea.…”

“…The European flat oyster ( Ostrea edulis ) is a marine filter-feeding bivalve native to the larger North Sea area and historically occurred in vast populations occupying sublittoral environments across different habitats [ Fig 1A ; 1 – 4 ]. Ostrea edulis beds are characterized by a high structural complexity and provide shelter and settling ground for a range of associated species, thus increasing local biodiversity [ 5 – 7 ].…”