Range Extension of a Nonindigenous Midge, Polypedilum nubifer (Diptera: Chironomidae), in North America Gregory S. Wallace1, William R. Mabee1,*, and Matthew D. Combes2 Abstract - We report range extension in North America by a nonindigenous midge, Polypedilum nubifer (Skuse), based on larval specimens collected during September 2007 from reaches of two streams in the Southeastern Lowlands physiographic region of Missouri. Endemic midge composition and water quality characteristics from the reaches are also presented. Polypedilum nubifer could become a rice crop pest and human nuisance across the Coastal Plains Ecoregion if it is able to persist in this ecoregion. Polypedilum nubifer (Skuse) is a eurytopic midge commonly found in eutrophic and anthropogenically disturbed waters (Wiederholm 1983) within tropical-subtropical Australasian, Afrotropical, Oriental, and Palaearctic regions (Jacobsen and Perry 2007). Larvae of P. nubifer have been reported to damage rice seedlings in China (Wang 2000), and swarms of P. nubifer emerging from waters near human population centers have been documented to be a nuisance in Australia, Asia, and Hawaii (Jacobsen and Perry 2007). This species has also been introduced to North America, where it has been collected in Florida (Jacobsen and Perry 2007). A range extension for P. nubifer in North America is reported based upon larvae of this exotic midge collected during 19 and 20 September 2007 from reaches of New Madrid County Ditch (NMCD) and Indian Camp Slough (ICS) in the Southeastern Lowlands physiographic region in Missouri (Fig. 1). The Southeastern Lowlands of Missouri are at the extreme northern end of the Coastal Plains Ecoregion (USEPA 2006), and are characterized by streams that have been highly modified by channelization, levees, and irrigation to permit agricultural enterprise. Many farms in the Southeastern Lowlands include rice in their crop rotation. Aquatic macroinvertebrate samples containing larvae of P. nubifer were collected by sampling depositional pool and submerged rootmat habitats with 500-μm mesh bottom aquatic kick nets (Sarver et al. 2002). Midge larvae in the samples were mounted on glass slides with coverslips and identified via compound light microscope using taxonomic keys and descriptive information provided in Epler (2001), Merritt et al. (2008), and Wiederholm (1983). Larvae of P. nubifer can be distinguished from those of congeners in North America by the alternate arrangement of the Lauterborn organs of the antenna (Cranston 2007, Wiederholm 1983). Midge taxa were more diverse in samples from NMCD than at ICS (Table 1), where P. nubifer composed, respectively, 7% and 2% of the midge larvae sampled. Six midge taxa—Cricotopus bicinctus, Dicrotendipes sp., Larsia sp., Microtendipes sp., Paratendipes sp., and Procladius sp.—collected with P. nubifer, have not previously been reported to co-occur with this exotic in North America. Depositional pool, submerged rootmat, and submerged woody debris habitats were sampled at NMCD, but only depositional pool habitat was available at ICS. Thirty specimens of P. nubifer were collected from depositional pool habitat at NMCD, and one Notes of the Southeastern Nat u ral ist, Issue 8/3, 2009 559 560 Southeastern Naturalist Notes Vol. 8, No. 3 specimen was collected from depositional pool habitat at ICS. A single specimen also occurred in a submerged rootmat habitat sample from NMCD. No specimens of P. nubifer were found in samples brushed from the surface of submerged woody debris habitat. Water quality characteristics sampled once at ICS during 26 June 2007 and once at NMCD during 13 August 2007 are provided in Table 2. In Figure 1. Map of locations where Polypedilum nubifer was collected in Missouri during 19 and 20 September 2007. 2009 Southeastern Naturalist Notes 561 general, water quality at ICS and NMCD was similar, or superior to, mean values of water quality found at 89 randomly selected sites sampled across the Coastal Plains Ecoregion during summer 2004 as part of the United States Environmental Protection Agency Wadeable Streams Assessment (Table 2; USEPA 2008). This finding suggests P. nubifer is potentially capable of invading additional waters within the ecoregion. Table 2. Water quality characteristics of stream reaches sampled during 26 June and 13 August 2007 where Polypedilum nubifer was collected in Missouri during 19 and 20 September 2007 compared to mean values of select water quality characteristics for approximately 89 sites sampled throughout the Coastal Plains Ecoregion during summer of 2004. Temp = temperature (°C), Cond = conductivity (uS/cm), Turb = turbidity (NTU), DO = dissolved oxygen (ppm), TP = total phosphorus (μg/L), TN = total nitrogen (mg/L), NO = nitrate/nitrite (mg/L), NH = ammonia (mg/L), NVSS = non-volatile suspended solids (mg/L), VSS = volatile suspended solids (mg/L), Chlor = total chlorophyll (μg/L), NMCD = New Madrid County Ditch, ICS = Indian Camp Slough, CPE = Coastal Plains Ecoregion. Stream Temp Cond pH Turb DO TP TN NO NH NVSS VSS Chlor NMCD 32.5 5.09 8.19 9.1 8.99 333 1.25 0.292 0.116 52.67 10.0 5.5 ICS 24.4 3.22 7.81 76.7 6.60 155 0.65 0.034 0.089 10.86 1.5 6.2 CPE 22.4 5.28 6.85 18.3 1.750 0.153 Table 1. Midge taxa identified in samples from stream reaches where Polypedilum nubifer was collected in Missouri during 19 and 20 September 2007. NMCD = New Madrid County Ditch, ICS = Indian Camp Slough. Taxa NMCD ICS Chironomidae Ablabesmyia sp. 2 21 Chironomus sp. 2 0 Cladotanytarsus sp. 105 0 Cricotopus bicinctus 2 0 Cryptochironomus sp. 2 0 Dicrotendipes sp. 94 18 Goeldichironomus sp. 2 0 Labrundinia sp. 8 6 Larsia sp. 59 9 Microtendipes sp. 1 0 Nanocladius sp. 1 0 Parachironomus sp. 16 0 Paratendipes sp. 6 0 Polypedilum sp. 3 0 Polypedilum convictum group 1 0 Polypedilum halterale group 2 0 Polypedilum illinoense group 8 0 Polypedilum nubifer 31 1 Polypedilum scalaenum group 4 0 Procladius sp. 1 0 Tanytarsus sp. 95 8 Ceratopogonidae Ceratopogoninae 11 4 Dasyheleinae 2 0 562 Southeastern Naturalist Notes Vol. 8, No. 3 Jacobsen and Perry (2007) collected P. nubifer in southern Florida from shallow, man-made detention ponds subject to periodic fl ooding and drying during seasonal operation in 2002. Irrigation of rice and other crops in the Southeastern Lowlands of Missouri causes much of the farm land and adjacent drainage ditches to fl ood and dry in an intermittent cycle similar to that reported by Jacobsen and Perry (2007). Our records extend the known distribution of this exotic species from the southern end of the Coastal Plains Ecoregion in Florida to the northern end in Missouri. This distribution indicates the entire Coastal Plains Ecoregion may have suitable habitat for P. nubifer . It is unknown if P. nubifer will displace populations of endemic midge fauna, or what other possible ecological consequences could be associated with occurrence of this exotic species in North America. However, occurrence of the exotic P. nubifer in the Southeastern Lowlands of Missouri and likely across the Coastal Plains Ecoregion is significant given the nuisance potential of the species. Acknowledgments. We thank Dr. John H. Epler for confirming our Polypedilum nubifer identifications. Mike Allen and David Knuth collected P. nubifer specimens in the field. Raissa Espejo, Amy Jungclaus, and Lance Dorsey assisted in processing macroinvertebrate community samples. Literature Cited Cranston, P.S. 2007. The Chironomidae larvae associated with the tsunami-impacted waterbodies of the coastal plain of southwestern Thailand. The Raffl es Bulletin of Zoology 55(2):231–244. Epler, J.H. 2001. Identification Manual of the Larval Chironomidae (Diptera) of North and South Carolina: A Guide to the Taxonomy of the Midges of the Southeastern United States, Including Florida. Special Publication SJ2001-SP13. North Carolina Department of Environment and Natural Resources, Raleigh, NC, and St. Johns River Water Management District, Palatka, FL. 526 pp. Jacobsen, R.E., and S.A. Perry. 2007. Polypedilum nubifer, a chironomid midge (Diptera: Chironomidae) new to Florida that has nuisance potential. Florida Entomologist 90(1):264–267. Merritt, R.W., K.W. Cummins, and M.B. Berg (Eds.). 2008. 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Shaker Verlag, Aachen, Germany. 661 pp. Wiederholm, T. (Ed.). 1983. Chironomidae of the holarctic region: Keys and diagnoses. Part 1: Larvae. Entomologica Scandinavica Supplement 19:1–457. ¹Missouri Department of Conservation, Resource Science Center, 1110 South College Avenue, Columbia, MO 65201. ²Missouri Department of Conservation, Agriculture Systems Field Station, 3500 South Baltimore, Kirksville, MO 63501. *Corresponding author - wr.mabee@mdc.mo.gov.