Research Article |
Corresponding author: Grigory S. Potapov ( grigorij-potapov@yandex.ru ) Academic editor: Michael Ohl
© 2018 Grigory S. Potapov, Alexander V. Kondakov, Yulia S. Kolosova, Alena A. Tomilova, Boris Yu. Filippov, Mikhail Yu. Gofarov, Ivan N. Bolotov.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Potapov G, Kondakov A, Kolosova Y, Tomilova A, Filippov B, Gofarov M, Bolotov I (2018) Widespread continental mtDNA lineages prevail in the bumblebee fauna of Iceland. ZooKeys 774: 141-153. https://doi.org/10.3897/zookeys.774.26466
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Origins of the fauna in Iceland is controversial, although the majority of modern research supports the postglacial colonization of this island by terrestrial invertebrates rather than their long-term survival in glacial refugia. In this study, we use three bumblebee species as a model to test the hypothesis regarding possible cryptic refugia in Iceland and to evaluate a putative origin of recently introduced taxa. Bombus jonellus is thought to be a possible native Icelandic lineage, whereas B. lucorum and B. hortorum were evidently introduced in the second half of the 20th century. These phylogeographic analyses reveal that the Icelandic Bombus jonellus shares two COI lineages, one of which also occurs in populations on the British Isles and in mainland Europe, but a second lineage (BJ-02) has not been recorded anywhere. These results indicate that this species may have colonized Iceland two times and that the lineage BJ-02 may reflect a more ancient Late Pleistocene or Early Holocene founder event (e.g., from the British Isles). The Icelandic populations of both Bombus lucorum and B. hortorum share the COI lineages that were recorded as widespread throughout Eurasia, from the European countries across Russia to China and Japan. The findings presented here highlight that the bumblebee fauna of Iceland comprises mainly widespread ubiquitous lineages that arrived via natural or human-mediated dispersal events from the British Isles or the mainland.
Dispersal, Hymenoptera , invertebrate introduction, island biogeography, North Atlantic islands
Iceland is a large North Atlantic island, the fauna of which is mostly of Palaearctic origin, with very few lineages that arrived from the Nearctic Region (
Bumblebees (Hymenoptera: Apidae: Bombus spp.) are an appropriate model for biogeographic reconstructions because these insects are associated with flowering plants and are poorly equipped for dispersal across large water barriers (
In spite of the fact that there have been multiple colonizations of Iceland by bumblebees, the origin of certain lineages has not been studied using a molecular approach, and only a single barcode sequence of Bombus lucorum from Iceland is currently available (
The bumblebee samples were collected with an entomological net (Ivan N. Bolotov leg.) in western and northern Iceland (Fig.
Map of study sites and typical habitat of Bombus jonellus in Iceland. A Map of study sites (see Table
Code | Localities | Coordinates | Date | Habitats | Species and samples |
---|---|---|---|---|---|
I | Geysir | 64°18'50.9"N, 20°17'58.7"W | 12.VII.2013 | Mountain herb-dwarf shrub tundra assemblages on lava fields and geyserite | Bombus lucorum (2☿) |
II | Flókadalsá River | 64°37'4.2"N, 21°30'9.4"W | 16.VII.2013 | Roadside, Nootka lupine assemblages | B. lucorum (4☿); B. jonellus (2☿) |
III | Blanda River | 65°34'52.7"N, 20°2'59.7"W | 17.VII.2013 | Herb meadows | B. lucorum (19☿); B. jonellus (1☿, 7♂) |
IV | Mývatn Lake | 65°34'12.4"N, 16°57'12.7"W | 17.VII.2013 | Mountain herb-dwarf shrub tundra assemblages | B. lucorum (2☿); B. jonellus (11☿, 1♂) |
V | Reykjavík | 64°7'44.7"N, 21°47'12.6"W | 18.VII.2013 | Herb meadows | B. lucorum (2☿); B. jonellus (7☿, 4♀); B. hortorum (2☿) |
We obtained new cytochrome c oxidase subunit I (COI) gene sequences from 12 Icelandic bumblebee specimens (Table
Species | COI lineage | COI GenBank acc. no. | Specimen Voucher* | Locality |
---|---|---|---|---|
Bombus jonellus | BJ-01 | MH168019 | BMB35 | Blanda River |
BJ-01 | MH168020 | BMB50 | Mývatn Lake | |
BJ-01 | MH168022 | BMB54 | Mývatn Lake | |
BJ-01 | MH168027 | BMB71 | Reykjavík | |
BJ-01 | MH168028 | BMB75 | Reykjavík | |
BJ-01** | MH168025 | BMB66 | Reykjavík | |
BJ-02 | MH168021 | BMB52 | Mývatn Lake | |
B. lucorum | BL-01 | MH168017 | BMB19 | Blanda River |
BL-01 | MH168024 | BMB64 | Reykjavík | |
BL-01 | MH168018 | BMB28 | Blanda River | |
BL-01 | MH168023 | BMB63 | Reykjavík | |
B. hortorum | BH-01 | MH168026 | BMB70 | Reykjavík |
The alignment of COI sequences was performed using the ClustalW algorithm implemented in MEGA6 (
Three bumblebee species were recorded in our new samples from Iceland, i.e., Bombus jonellus, B. lucorum and B. hortorum (Table
We found that the sequenced Bombus jonellus specimens from Iceland share three COI haplotypes belonging to two different lineages (Fig.
Median-joining haplotype networks of the available COI sequences of bumblebee species inhabiting Iceland. The circle size is proportional to the number of available sequences belonging to a certain haplotype. The small red dots indicate hypothetical ancestral haplotypes. Red numbers near branches indicate the number of nucleotide substitutions between haplotypes. Black codes indicate the COI lineages inhabiting Iceland. A Bombus jonellus (N = 29) B B. lucorum (N = 115) C B. hortorum (N = 33). Photographs by Yulia S. Kolosova.
The Icelandic Bombus lucorum specimens belong to a single COI lineage (BL-01) that occurs in populations from Russia, China, Mongolia, Northern Europe (Denmark, Finland, Sweden, and Latvia), Western Europe (Austria and Germany), the British Isles (Ireland and United Kingdom), and Turkey, and in an invasive population from Hokkaido, Japan (
Approximate distribution ranges of the widespread ubiquistic COI lineages recorded in bumblebee populations from Iceland (see Suppl. material
A single sequenced specimen of Bombus hortorum from Iceland also belongs to a widespread COI lineage (BH-01) that occurs in populations from China, European Russia, Northern Europe (Denmark and Norway), Western Europe (France and Germany), Southern Europe (Italy), and the British Isles (United Kingdom) (Figs
= Bombus (Pyrobombus) jonellus subborealis Richards, 1933, syn. n.
This subspecies is thought to be distributed in Norway and Iceland (
The modern bumblebee fauna of Iceland with seven species is close to species-poor assemblages on boreal European islands (e.g. the Solovetsky Archipelago in Northern European Russia:
We are unable to discuss the putative places of founders’ origin for Icelandic Bombus hortorum and B. lucorum populations due to extensive distribution ranges of the founding lineages, and they may have originated from the British Isles and from anywhere on the mainland (Fig.
At first glance, a global phylogeographic pattern in Bombus jonellus may reflect its survival in two distant glacial refugia, i.e., in Europe and in Beringia, although no sequences of this species from Siberia are available, and may narrow the current gap between European and Nearctic haplogroups (Fig.
The presence of putative unique haplotypes in Norway, the United Kingdom, and Iceland could indicate a rapid northwestern expansion of this species from glacial refugia in Southern and Central Europe in the Late Pleistocene or Early Holocene. Our data set is very limited, and it is highly likely that the unique lineage BJ-02 from Iceland can be found somewhere on the British Isles, Shetland, and Hebrides or in mainland Europe. However, our results indicate that Bombus jonellus may have colonized Iceland two times and that the lineage BJ-02 may reflect a more ancient, Late Pleistocene or Early Holocene founder event (e.g. from the British Isles), albeit more sampling efforts are necessary to obtain a fully resolved biogeographic model for this species. We agree with
Indeed, our results inferred from the Icelandic bumblebees correspond well to the tabula rasa hypothesis. Such a phylogeographic pattern has been discovered in several other taxa, and a slowly growing body of molecular research indicates that invertebrate faunas on the North Atlantic Islands have had postglacial allochthonous origin (
This study of bumblebee ecology was supported by the Federal Agency for Scientific Organizations (no. 0409-2015-0141). Bumblebee species from the European North were studied through the support the Russian Foundation for Basic Research, RFBR (no. 16-34-60035 mol_a_dk). The global distribution of bumblebees was studied within a project of the Russian Ministry of Education and Science (no. 6.2343.2017/4.6) and the Russian Foundation for Basic Research (no. 16-05-00854). The collection of bumblebees, species identification, and the formation of a scientific collection were supported by the Federal Agency for Scientific Organizations (no. 0409-2016-0022). The bumblebee samples in Iceland were collected under the framework of a scientific agreement between the Institute of Earth Sciences, the University of Iceland, and the Institute of Environmental Problems of the North of the Ural Branch of the Russian Academy of Sciences. We are grateful to Dr. Andri Stefansson (Institute of Earth Sciences, University of Iceland, Iceland) and Dr. Oleg S. Pokrovsky (GET CNRS, IRD, University of Toulouse, France) for their great help in the organization of the fieldwork in Iceland. Special thanks go to the Edit-My-English team for improving the language of the paper.
Table S1