Genetic analyses support subspecies classification in the Common Ringed Plover.
“Of what use are subspecies?” asked biologist Ernst Mayr in a 1982 paper. The concept of a subspecies has generally been used to subdivide the geographical distribution of a species into meaningful units that differ in some morphological characters. Most subspecies, however, have not been assessed with genetic data (but see e.g., Wagtails). A recent study in the journal Ardea checks how well subspecies of Common Ringed Plover (Charadrius hiaticula) are supported by genetics.
How Many Subspecies?
The number of Common Ringed Plover subspecies ranges from two to seven, but most authors recognize three subspecies:
- hiaticula (southern Scandinavia and the Baltic)
- tundrae (northern Scandinavia and Russia)
- psammodromus (Canada, Greenland, Iceland and Faeroe Islands)
Birds from Chukotka, in the Russian far east, differ from the other subspecies in this region (tundrae) and might represent a distinct subspecies: kolymensis.
No Population Structure
Leon Thies (University of Graz) and his colleagues collected samples across the range of the Common Ringed Plover and genotyped them using microsatellites. In general, the genetic analyses revealed no pronounced population structure. This observation can be explained by the dispersal patterns of these birds: juveniles do not breed at the site where they were born (i.e. low natal philopatry). The dispersal between different breeding sites results in gene flow that counteracts population differentiation.
However, when prior knowledge about the sampling location is included in the models, the three main subspecies are supported by the genetic data. There was no evidence for the putative kolymensis subspecies from Chukotka.
A Hybrid Zone
Admixture analyses (using the software package Structure) suggests a hybrid zone between all three subspecies, running from Northern Scandinavia to Belarus. The authors speculate that the subspecies diverged in allopatry during the ice ages and came into secondary contact. However, a more thorough genetic analysis is needed to characterize this putative hybrid zone.
North vs. South
Finally, one paragraph in the discussion caught my attention:
In Dunlins Calidris alpina and Purple Sandpipers Calidris maritima, two sandpipers that breed at similar latitudes as Ringed Plovers, subspecies delineation based on phenotypic characters is poorly supported by genetic markers. In contrast, in several temperate or tropic waders, sub species delineation is in agreement with patterns of genetic differentiation.
Why do mismatches between genetic and phenotypic data occur more frequently in high latitude species? The classical explanation is that climatic oscillations had a stronger impact at higher latitudes. But is that really so?
Thies, L., Tomkovich, P., dos Remedios, N, Lislevand, T., Pinchuk, P., Wallander, J., Dänhardt, J., þórisson, B., Blomqvist, D & Küpper, C. (2018) Population and Subspecies Differentiation in a High Latitude Breeding Wader, the Common Ringed Plover Charadrius hiaticula. Ardea 106(2), 163-176.
This paper has been added to the Charadriiformes page.