Research Article |
Corresponding author: Hume B. Douglas ( hume.douglas@canada.ca ) Academic editor: Ron Beenen
© 2022 Hume B. Douglas, Stéphane Dumont, Karine Savard, Graham S. Thurston, Marilyn H. S. Light.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Douglas HB, Dumont S, Savard K, Thurston GS, Light MHS (2022) Palaearctic seed beetle Bruchus affinis (Coleoptera, Chrysomelidae, Bruchinae) new to North America, arrival, distribution, and autecology. ZooKeys 1128: 19-31. https://doi.org/10.3897/zookeys.1128.90016
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First North American records are presented for Bruchus affinis Frölich, 1799 (Coleoptera, Chrysomelidae, Bruchinae), as confirmed by morphology from multiple sites in Canada: British Columbia, Ontario, and Québec. Diagnostic information is presented for B. affinis in North America. This insect is expected to reduce plant reproductive output in infested Lathyrus latifolius L., Lathyrus sylvestris L., and other potential Lathyrus (Fabaceae) hosts. Impacts on broad bean (Vicia faba L.) production are expected to be small. Potential reproductive impact on native North American Lathyrus species remains unknown. The United States of America and Canada are now known to be home to 69–79 species of adventive Chrysomelidae including 16–18 Bruchinae.
We have found two dead, teneral B. affinis individuals inside Lathyrus seeds imported from Europe, and we hypothesise that this species was introduced to Canada from Europe via seeds for planting sometime before 2007. At our study sites, Lathyrus flowering began in mid June followed by oviposition in late June with first adults emerging in late August, requiring about 60 days from egg to adult stage. Dinarmus basalis (Rodani, 1877) (Hymenoptera, Pteromalidae) was newly recorded as parasitoid of Bruchus affinis in Canada, and caused about 10% mortality in B. affinis at our sites.
Invasive alien species, biological control
The univoltine seed beetle Bruchus affinis Frölich, 1799 is native to most countries of the western Palaearctic Region (
Lathyrus latifolius (Fabaceae) is a perennial flowering vine introduced to North American gardens perhaps as early as the 1700s. It is now established as an ornamental and weedy species in Canada and USA. Lathyrus sylvestris was introduced sometime before 1827 when seeds of both plants were listed in a Canadian nursery catalogue (
We also examined the phenology and behaviour of B. affinis with L. latifolius and L. sylvestris in two Gatineau localities. This was to learn how B. affinis interacts with plant hosts in Canada. In particular, we examined the timing of flowering and the B. affinis egg to adult interval. We asked: at what date does B. affinis first appear on the hosts, mate, and begin oviposition? We also investigated the period required for eggs to hatch and for adult beetles to emerge from infested seeds.
The first pods of L. latifolius to ripen in 2020 in the Gatineau garden represent the first infestation cohort for the site and plant (hereafter the index plant). Fifty-four seeds were harvested from that plant and dried at room temperature. Over the next few weeks, 18 beetles emerged, with a total seed infestation rate of 33%. Beetles were submitted to HD via the Agriculture and Agri-Food Canada Entomology National Identification Service. All specimens are deposited at the
Canadian National Collection of Insects, Arachnids, and Nematodes (
In 2021, all authors searched for additional populations of Bruchinae associated with Lathyrus spp. in Canada, examining growing plants, insect collections, and online photograph-sharing websites for specimens and observations. HD also contacted biologists with the Canadian Food Inspection Agency’s Plant Health Survey Unit to search Lathyrus plants for Bruchus beetles in other parts of Canada. Stephen Paiero checked the University of Guelph insect collection (Guelph, Ontario) for additional specimens of B. affinis, but found none. No comprehensive field survey has been conducted to determine the full range of this species in North America.
Beetle behaviour study locations were in Gatineau QC, a private garden, with only the L. latifolius index plant (45.464, −75.761). Additional beetles were observed in nearby roadsides, with eight patches of L. sylvestris, 45.4562, −75.7638 (2 m diameter); 45.4571, −75.7672 (3 m diameter); 45.4551, −75.7612 (3 m diameter); 45.455, −75.761 (2 m diameter); 45.4546, −75.7604 (5 m diameter); 45.4544, −75.7601 (1 m diameter); 45.4542, −75.7598 (6 m diameter); and 45.454, −75.7594 (2 m diameter). Historical weather data for Ottawa International Airport (Ontario, Canada) was obtained from
Behavioural observations began with daily monitoring of the garden L. latifolius plant by ML for flowering and beetle activity from June through September 2021. First inflorescences having flowers open were tagged and then tracked. The first available pods were monitored for oviposition. Tagged pods remained on the plant until mature when they were harvested and permitted to dehisce. All remaining closed pods were opened manually two months after harvest. Seed infestation and parasitoid presence were assessed for all seeds from all tagged pods. Herbarium vouchers from both Lathyrus species were collected, for deposition in herbaria (CAN/DAO) (Fig.
Morphology of Lathyrus spp. and B. affinis from Québec, Canada A apex of L. latifolius stem, garden plant (45.464, −75.561) B L. sylvestris stem, pressed (45.457, −75.767) C egg of B. affinis on outer pod wall of L. sylvestris D opened pod of L. sylvestris with seed entry holes of B. affinis larvae and white inner pod wall tissue developing beneath oviposition sites E infested seed of L. sylvestris with first instar larva of B. affinis F same with second instar larvae. Scale bars: 50 mm (A, B); 0.5 mm (C); 25 mm (D); 5 mm (E, F).
Adult beetles were hand collected (i.e. not using a net) from L. sylvestris at behavioural study sites by ML in early morning. Specimens were preserved in 95% ethanol with several voucher specimens mounted. Stem tagging was not possible at the L. sylvestris roadside localities. So, randomly selected stems were used for study. Pods at varying developmental stages were examined and/or collected on several mornings from June to October. All seeds retained for rearing were stored at room temperature and examined daily for presence of emergent beetles. Maturing green to yellow seeds were opened within 24 hours of collection using a scalpel to view their contents (Fig.
Field photography was conducted by ML using an Olympus 12.5× Super Wide Optical Zoom camera. Macro photography was done using an Olympus EM5 MkII with macro lens according to subject and an Olympus T10 Ring Flash or an Olympus RFII Ring Flash for larger subjects. An Epson Perfection Scanner V550 Photo was used to document Lathyrus stems and herbarium specimens.
The external morphology and male genitalia of Canadian specimens closely matched taxon concepts of B. affinis from
We found B. affinis at the following localities in Canada: British Columbia: Vancouver, 49.2162, −123.1713, 22.VI.2021, ex. L. latifolius, B. Spencer, 4 ex; Québec: Gatineau, 45.463, −75.765, reared from L. latifolius seeds from garden, M.H.S Light, 8 ex., CNC1053109 to CNC1053117; Gatineau, 5.IX.2021, M.H.S. Light; Wakefield, 45.6466, −75.9298, reared from L. sylvestris seeds of field edge patch,15.VIII.2021, M.H.S. Light, 12 ex.; Gatineau, boul. Cité des Jeunes, 45.4544, −75.7601, mating on flowering L. sylvestris of roadside patch, 27.VI.2021, M.H.S. Light, 5 ex.; Gatineau, 45.4546, −75.7604, 27.VI.2021, M.H.S. Light, 18 ex.; Gatineau, 45.464, −75.761, reared from L. latifolius seeds from garden, 18.VIII.2021, M.H.S. Light, 1 ex.; Gatineau, 45.71, −75.7672, reared from L. sylvestris seeds of a roadside patch, 15.VIII.2021, M.H.S. Light, 5 ex.; Gatineau, 45.4551, −75.7612, reared from L. sylvestris seeds, 15.VIII.2021, M.H.S. Light, 8 ex.; Gatineau, 45.464, −75.761, infesting L. latifolius seeds; Gatineau QC, eggs on pod 25.VI.2021, eggs hatch 6.VII, beetles hatch 18.VIII.2021, M.H.S. Light, 8 ex.; Gatineau, 45.464, −75.761, Dead Bruchus affinis from two seeds in a sealed commercial package of 25 L. latifolius seeds, 18.21.III.2021, M.H.S. Light, 2 ex.; Farm Point, 45.6092, −75.8975, 23.VI.2021, ex. roadside Lathyrus flowers, H. Douglas, 6 ex.; Laval, Boisé Papineau (Près St. Martin) sur marguerite, 45.60229, −73.68096, 19.VI.2013, S. Dumont, 1 ex.; Laval, Boisé Papineau, 45.60704, −73.68082, battage spirée en fleurs, 21.V.2014, S. Dumont, 1 ex.; Laval, Boisé Papineau, 45.603, −73.681, sur Lathyrus, 29.VII.2014, S. Dumont, 3 ex.; Laval, Contrecoeur, Camp des Grèves 45.979, −73.182, sur Lathyrus, 7.VIII.2009, S. Dumont, 3 ex.; Laval, Berge Olivier-Charbonneau 45.698, −73.529, sur L. latifolius, 21.VII.2021, S. Dumont, 22 ex.; Montréal, Anjou, près Parc Roger Rousseau 45.617, −73.545, sur L. latifolius, 22.VII.2021, S. Dumont, 20 ex.; Notre-Dame-de-l’île-Perrot (Vaudreuil), 4.VII.2007, Battage Lathyrus sp., Pierre de Tonnancour, 2 ex.; Notre-Dame-de-l’île-Perrot (Vaudreuil), 20.V.2011, Battage Caragana sp., Pierre de Tonnancour, 1 ex.; Notre-Dame-de-l’île-Perrot (Vaudreuil), 14.VI.2011, Battage Cirsium arvense, Pierre de Tonnancour, 1 ex.; Notre-Dame-de-l’île-Perrot (Vaudreuil), 20.V.2011, Battage Rubus odoratus, Pierre de Tonnancour, 1 ex.; Notre-Dame-de-l’île-Perrot (Vaudreuil), 31.VIII.2011, Battage Lathyrus latifolius, Pierre de Tonnancour, 1 ex.; Notre-Dame-de-l’île-Perrot (45.3775, −73.9431), 7.VI.2019, fauchage, champ humide, Pierre de Tonnancour, 1 ex. Ontario: Ottawa, Hurdman Bridge, 45.418, −75.664, 3.VII.2021, ex. Lathyrus flowers, 8 ex., H. Douglas (field photographs: https://www.inaturalist.org/observations/85903171. An additional female Bruchus specimen from near Québec City, seen only in internet photographs also has pronotal morphology matching B. affinis (https://www.inaturalist.org/observations/38795458), suggesting that B. affinis may also be established in that region.
We present evidence of 79 specimens from multiple sites in three provinces, separated by over 3500 km over 14 years, and rearing evidence of successful reproduction in nature. Together, these lead us to conclude that multiple populations of B. affinis are established in Canada.
Bruchus affinis can be distinguished from other North American Bruchus by the following combination of characters (adapted from key by
It was initially unknown whether the infestation of the index plant could represent the first establishment of a new population of B. affinis in Canada. Alternatively, we thought this infestation could have spread from a pre-existing adventive population. Later we found nearby patches of B. affinis-infested L. sylvestris. Finding these specimens as well as others from elsewhere in Canada (many collected before 2020) is consistent with spread of a pre-established adventive population rather than establishment of a new adventive population in the garden of the index plant resulting from planting infested seeds there.
Our finding of B. affinis specimens within seeds of L. latifolius that were commercially imported from Europe suggests that import of infested seed is a likely pathway for the introduction of this species to Canada. The discovery of B. affinis in Québec, Ontario, and British Columbia over only 15 years is consistent with multiple introductions over several years since our earliest specimen collection date in 2007. This is also consistent with movement of infested seed rather than haphazard introduction of adults (e.g. live beetles accidentally trapped in shipping containers). This evidence indicates that B. affinis was present in Canada for 15 or more years.
Bruchus affinis is known to infest seed pods of L. grandiflorus, Sibth. & Smith, L. latifolius, L. sylvestris, and L. tuberosus L. (
Bruchus affinis is also known to use Vicia faba as host in Europe (
This new North American record, added to the species counts by
Flowering of both Lathyrus species began the week of June 15, 2021. The first L. latifolius pods developed by June 23 with the first eggs appearing on pods June 25: hatching began July 6. Mature, undehisced pods were collected from August 2 to August 12. Twenty-one B. affinis emerged from the 76 seeds (22 pods) on August 18–26 only: there were no further emergences. Seed infestation rate was 27.6%, averaging about one B. affinis larva per pod. Of the 21 tagged pods, 20 contained eggs (range 1–8 eggs per pod; median 3 eggs per pod). Overall, beetle reproduction on L. latifolius commenced as soon as flowers developed. Development of the new beetle generation was complete by the end of August, with about one quarter of seeds killed by beetles.
On L. sylvestris, 30 B. affinis adults were observed on June 27 on plants at five of eight roadside patches. Few B. affinis were seen after decrease in flower production in mid-July. The first 43 B. affinis individuals reared indoors emerged on August 14. Emergence of B. affinis collected from all eight patches on July 28 (104 pods/606 seeds) occurred mainly during two peak periods with warm weather: August 14–21 (preceded by five days of hot weather, 30–31 °C; indoor 27 °C), 68 beetles; and August 25–26 (daily max. 32.8–32.7 °C; indoor 27 °C; 92 beetles). Of all 215 beetles eclosed in August 2021, 160 were from these two periods. The infestation rate of the 606 seeds was 35% (13.5–73.5% across patches). If a pod had not yet dehisced, emerging beetles chewed exit holes to exit through the pod wall. The sound of chewing was audible outdoors from up to 2 m away. All observed beetles initiated flight immediately after exiting pods outdoors or within rearing containers. Flying behaviour in containers continued for several hours, after which emerging beetles no longer attempted flight. Dehisced or manually opened pods of both species revealed white tissue developing from the inner pod wall beneath egg positions (Fig.
The earliest evidence of parasitism was September 1 when two different hymenopteran larvae were found within B. affinis-infested seeds. Hymenoptera parasitoids of B. affinis first emerged from mature seeds of L. sylvestris (collected September 5, 10, and 11. These were identified as Dinarmus basalis (Rodani, 1877), a cosmopolitan parasitoid of Bruchinae in legume seeds (
A Bruchus affinis, parasitized by Hymenoptera larvae in seed of L. sylvestris B maturing pods of L. sylvestris with hatched and unhatched eggs C dehisced pod of L. latifolius D dehisced pod of L. sylvestris showing B. affinis exit holes in pod wall and seed. Scale bars: 2 mm (A); 25 mm (B); 50 mm (C); 20 mm (D).
Onset of host flowering was about two weeks earlier in Québec (mid-June) than reported from France (early July) (
In summary, we report the following from North America (Québec): infestation of L. latifolius and L. sylvestris (Fabaceae) by Bruchus affinis; rearing of B. affinis from both hosts; oviposition in 2021 beginning late June, to adult emergence beginning mid August; observation of B. affinis adults chewing holes to exit undehisced pods of L. sylvestris; parasitization of B. affinis by Dinarmus basalis in Québec. We also found that the seed emergence hole diameter of B. affinis was consistently larger than that of parasitoid emergence holes, such that we could reliably distinguish between exit hole types. We quantified B. affinis seed infestation rates of L. latifolius (17–28%), and of L. sylvestris (13.5–73.5%) for 2021.
Bruchus affinis is established in North America in Canada in Québec, Ontario, and British Columbia since 2007 or earlier using introduced Lathyrus latifolius and L. sylvestris as hosts. These populations may have originated from imports of infested seed for planting. Numbers of recorded adventive Chrysomelidae for Canada and America north of Mexico are updated to reflect this finding. Beetle development involved an approximately two-month period from oviposition to emergence. Phenological milestones of adult flight activity, oviposition, and adult emergence were estimated for study populations. Parasitoids were documented to use B. affinis as a host in Canada, but had a minor impact on infestations, accounting for about 10% mortality of pre-emergent pupae.
We thank A. Delobel (Muséum National d’Histoire Naturelle, France); G. Kergoat (French National Research Institute for Agriculture); G. Morse, University of San Diego, and L. Borowiec (University of Wrocław) for assistance in determining the identity of our specimens. We thank I. Nei (Canadian Food Inspection Agency, CFIA), B. Spencer (Vancouver, British Columbia), and P. de Tonnancour (Vaudreuil, Québec) for specimens, and T. Kimoto (CFIA) and S. Paiero (University of Guelph) for searching. Thanks to iNaturalist website participants who posted photographs of Lathyrus and Bruchus specimens that we investigated. We also acknowledge that V. Belov (Texas A & M) University correctly identified B. Spencer’s photographed beetles as B. affinis in 2020 (https://bugguide.net/node/view/1852275); we appreciate that international identifiers like V. Belov sometimes notice new adventive insects in Canada. Thanks to M. Vankosky (AAFC), J. Tansey (Government of Saskatchewan), and J. Gavloski (Government of Manitoba) for information on pests of fava bean in Canada. Thanks to G. Kenicer (Royal Botanic Garden, Edinburgh) for assistance with identification of L. latifolius and L. sylvestris, to O. Lonsdale, G. Gibson, and J. Huber (