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Geographic distribution of the nonnative Mediterranean Gecko (hemidactylus turcicus) in Oklahoma.

Frequently, distributional information for novel nonnative species is inaccurate (Graham et al., 2007) or filled with unwarranted gaps. Successful invaders often colonize new locations long before detection (Molnar et al., 2008). Factors that contribute to obscure spatial data are varied among different exotic species. in the case of the Mediterranean gecko (Hemidactylus turcicus), cryptic behavior and advantageous dispersal methods allow individuals to colonize new locations while remaining undetected (Selcer, 1986).

Native throughout the Mediterranean region (Conant and Collins, 1998), H. turcicus has been introduced into the New World with established populations in the United States, Cuba, (Schwartz and Henderson, 1991; Rodder and Lotters, 2009), and parts of Central America and Mexico (Collins and Irwin, 2001; Rodder and Lotters, 2009) due to human-mediated dispersal (Locey and Stone, 2006). In the past century, H. turcicus has increased its range throughout the United States since its first record in Key West, Florida, in 1910 (Stejneger, 1922; Jadin and Coleman, 2007). Hemidactylus turcicus now exhibits a broad, patchy distribution across most of the southern United States (Davis, 1974; Meshaka, 1995; Conant and Collins, 1998; Gomez-Zlatar et al., 2006; White and Husak, 2015) with northern populations in Pennsylvania (Powell et al., 2016).

The rapid range extension of Hemidactylus turcicus is due to unintentional human-mediated introductions (Lever, 2003) and is commonly found near anthropogenically influenced habitats (Rato et al., 2011), particularly apartments, hotels, and businesses where human traffic is high (White and Husak, 2015). Because their association with human activity and natural diffusion rates are low, drop dispersal is likely the driving force behind H. turcicus range expansion (Locey and Stone, 2006). Geckos have been known to deposit eggs in nursery plants (Livo et al., 1998), moving boxes, and old piles of clothing where transportation via human movement to new potential colonization sites is possible (Selcer, 1986).

While most H. turcicus introductions are likely unintentional, deliberate human-mediated dispersal has been documented by researchers. Beginning in the 1960s, the first records of H. turcicus in Oklahoma were due to intentional releases on multiple university campuses, including the University of Oklahoma in Cleveland County (Sievert and Sievert, 2011) and the University of Central Oklahoma in Oklahoma County (Locey and Stone, 2006). Hemidactylus turcicus has since been documented by researchers throughout much of southwestern Oklahoma, with patchy distribution throughout the state (White and Husak, 2015). Prior to 2016, 54 of the 77 Oklahoma counties lacked records for H. turcicus, with the last documented range extension adding nine new counties in 2015 (White and Husak, 2015). The purpose of this study was to fill gaps between previous records of nonnative H. turcicus and assess the current status of the species in the state of Oklahoma.

For this study, we incorporated the methodology of White and Husak (2015). To assess the statewide status of H. turcicus, we selected the largest city in each Oklahoma county without previous documentation to search for gecko activity. We conducted searches an hour after sundown for 3 h or until gecko activity was observed. We selected older buildings of brick construction with the presence of eaves due to the availability of gecko refugia. To facilitate hand-capturing of geckos, we used flashlights to temporarily blind individuals, allowing for easier capture. Because H. turcicus were often observed perched out of reach on high walls, we also splashed individuals with tap water to temporarily dislodge them from the surface. Geckos adhere to surfaces using setae located on their toes (Autumn et al., 2002). When setae come in contact with water, their adhesive capabilities are reduced, therefore decreasing climbing performance (Huber et al., 2005; Sun et al., 2005; Lee et al., 2007). We hand-collected H. turcicus that fell to the ground and placed them into plastic containers with corresponding location data. We cataloged geckos that we collected into the Cameron University Zoological Museum. Each town/city was searched twice during the summer of 2014.

We documented 16 Oklahoma counties that were not previously known to contain H. turcicus: Murray, Johnston, Bryan, Pushmataha, Choctaw, Logan, Kay, Noble, Canadian, Osage, Rogers, Creek, Wagoner, Pittsburg, McIntosh, and Okmulgee (Table 1; Fig. 1). For each site, we observed multiple individuals. We often observed individuals away from lights or in low light conditions. Individuals that we observed in low light conditions were often positioned near refugia or hidden behind rain gutters that run vertically against walls. Including the previous 24 Oklahoma counties (White and Husak, 2015), a total of 40 Oklahoma counties now contain H. turcicus. We surveyed 20 counties with no gecko activity: Harmon, Greer, Kiowa, Washita, Custer, Dewey, Major, Woods, Alfalfa, Grant, Pawnee, Washington, Nowata, Lincoln, Seminole, Okfuskee, Hughes, Coal, Kingfisher, and Beckham (Fig. 1).

We documented 16 additional Oklahoma county records for H. turcicus, thus filling notable gaps in the previously known range. A substantial number of the new records are located throughout central Oklahoma where human populations per county varied from 10,980 (Johnston County) to 133,378 (Canadian County), with an average of 44,277.31 per county (n = 16) (United States Census Bureau, The 20 Oklahoma counties with no observed gecko activity varied in human population from 2,788 (Harmon County) to 52,021 (Washington County), with an average of 15,118.65 (n = 20) per county (United States Census Bureau, Oklahoma counties with larger populations potentially have increased opportunities for human-mediated dispersal, due to increased human traffic and widespread highway systems.

Counties containing H. turcicus are limited in western Oklahoma, especially in surveyed counties closest to the panhandle and the New Mexico border. Western Oklahoma counties with unsuccessful searches have human populations ranging from 2,788 (Harmon County) to 29,744 (Custer County), with an average of 9,705 (n = 9) people per county (United States Census Bureau, https:// Less-populated counties with less human traffic could reduce chances of drop dispersal events. Adjacent states with established H. turcicus populations could serve as corridors for human-mediated dispersal (White and Husak, 2015); however, significant population recruitment to western Oklahoma from adjacent Texas panhandle and New Mexico counties are unlikely due to the apparent absence of established H. turcicus populations in the Texas panhandle and activity in New Mexico being limited to sparse records in the south-central portion of the state (Conant and Collins, 1998).

Survey bias and search effort (Farallo et al., 2009) might affect H. turcicus detection rates. We targeted motels, restaurants, and gas stations adjacent to highways for searches. Counties with lower populations had fewer locations suitable for H. turcicus surveys. We often overlooked residential areas due to time constraints. Targeting heterogeneous survey sites would potentially increase H. turcicus detection rates in counties where typical H. turcicus anthropogenic habitat is reduced. We conducted nightly surveys methodically, beginning an hour after sunset. However, we selected specific survey sites depending on proximity to the previously searched site because of time constraints. We conducted individual surveys of buildings at different times depending on the completion of the previous survey. Activity of H. turcicus is known to vary throughout the night (Frankenberg, 1984), and searches conducted during times of lower activity might result in individuals going undetected.

Researchers should conduct future surveys in the remaining unsearched Oklahoma counties to assess the status of H. turcicus in the state. Revisiting surveyed counties where H. turcicus was not found could produce additional records. Undetected H. turcicus may reside within counties where searches were unsuccessful, and revisiting unsuccessful survey sites could track new introductions as drop dispersal events occur across Oklahoma. With few recorded populations in Kansas, established Oklahoma populations near the southern Kansas border may act as source populations for H. turcicus in southern Kansas. In light of frequent surveys being conducted in the state, most of Kansas may lack established populations of H. turcicus (J. White, pers. observ.).

We thank the numerous property owners who gave us access to buildings during late night hours and J. Jang and S. Ebenhoe for assistance in the field. We thank G. Sievert for comments on helpful field collecting techniques. For abstract translation, we thank C. Caio and C. De Niz.


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Submitted 28 May 2016.

Acceptance recommended by Associate Editor, Felipe de Jesus Rodriguez Romero, 7 October 2016.

Caption: FIG. 1--Previously documented distribution of Hemidactylus turcicus in Oklahoma (gray-filled circles, following White and Husak, 2015), counties searched without finding H. turcicus (open circles), and new county records documented in the current study (blackfilled circles).
Table 1--Specimens of Hemidactylus turcicus representing new county
records that we collected in Oklahoma and deposited in the Cameron
University Museum of Zoology (CUMZ).

County           City

Murray       Sulphur
Johnston     Tishomingo
Bryan        Durant
Pushmataha   Antlers
Choctaw      Hugo
Logan        Guthrie
Kay          Blackwell
Noble        Perry
Canadian     Yukon
Osage        Tulsa
Rogers       Owasso
Creek        Supulpa
Wagoner      Broken Arrow
Pittsburg    McAlester
McIntosh     Eufaula
Okmulgee     Okmulgee

County                        Coordinates

Murray       34[degrees]30'28.44"N, 96[degrees]58'5.88"W
Johnston     34[degrees]14'10.32"N, 96[degrees]40'42.96"W
Bryan        33[degrees]59'32.64"N, 96[degrees]23'49.56"W
Pushmataha   34[degrees]13'52.32"N, 95[degrees]37'12.72"W
Choctaw      34[degrees]30'38.52"N, 95[degrees]30'34.92"W
Logan        35[degrees]52'44.04"N, 97[degrees]25'31.08"W
Kay          36[degrees]48'16.2"N, 97[degrees]15'11.16"W
Noble        36[degrees]17'22.2"N, 97[degrees]17'17.16"W
Canadian     35[degrees]30'24.12"N, 97[degrees]40'21"W
Osage        36[degrees]11'36.96"N, 95[degrees]56'17.52"W
Rogers       36[degrees]16'10.2"N, 95[degrees]51'16.92"W
Creek        35[degrees]59'55.32"N, 96[degrees]6'51.12"W
Wagoner      36[degrees]3'39.24"N, 95[degrees]47'51"W
Pittsburg    34[degrees]56'0.24"N, 95[degrees]46'10.56"W
McIntosh     35[degrees]17'14.28"N, 95[degrees]34'57"W
Okmulgee     35[degrees]37'24.24"N, 95[degrees]57'38.16"W

County        Date of capture    CUMZ no.

Murray       14 August 2014        231
Johnston     14 August 2014        232
Bryan        14 August 2014        234
Pushmataha   15 August 2014        235
Choctaw      15 August 2014        236
Logan        22 August 2014        238
Kay          22 August 2014        239
Noble        22 August 2014        240
Canadian     22 August 2014        241
Osage        30 August 2014        242
Rogers       30 August 2014        243
Creek        31 August 2014        244
Wagoner      31 August 2014        245
Pittsburg    21 September 2014     246
McIntosh     21 September 2014     247
Okmulgee     31 September 2014     248
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Article Details
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Author:White, Jared W.; Husak, Michael S.; Willis, Ray E.
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1U7OK
Date:Dec 1, 2016
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