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New distribution records of an endemic diving beetle, Heterosternuta sulphuria (Coleoptera: Dytiscidae: Hydroporinae), in Arkansas with comments on habitat and conservation.

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Hydroporus (Heterosternuta) sulphuria is a small, predaceous diving beetle originally collected from Sulphur Springs, Arkansas, in 1955 by Paul Spangler and later described (Matta and Wolfe, 1979; Nilsson, 2007). Wolfe (2000) elevated the subgenus Heterosternuta of Hydroporus to the generic level. Fourteen species currently are described in this genus (Wolfe, 2000), with three of these found only in Arkansas (H. sulphuria, H. ouachita; Matta and Wolfe, 1979, and H. phoebeae; Wolfe and Harp, 2003). Heterosternuta sulphuria was not collected on a subsequent trip to the type locality (Matta and Wolfe, 1979), and few H. sulphuria have been collected since the type series of 33 specimens. Two historical surveys of water beetles that produced a total of 1,161 organisms provided further evidence of the rarity of this species; one suspect female specimen collected in a 1988 survey (G. L. Harp, in litt.) and three female specimens (two positively identified and one suspect) collected in a 1992 survey (Wolfe and Harp, 2003). These four specimens were collected from four separate streams in the watershed of Buffalo National River. Heterosternuta sulphuria has been listed as a species of greatest conservation need in Arkansas with a priority score of 80 out of 100 (Anderson, 2006). A research need of the Arkansas Wildlife Action Plan was to obtain baseline information on distribution and population status of H. sulphuria (Anderson, 2006).

Surveys for H. sulphuria were initiated in autumn 2007 in the Ozark and Boston Mountain ecoregions in Arkansas. These have provided an additional four locations for populations of H. sulphuria (Fig. 1, Table 1), including the currently protected Hobbs State Park-Conservation Area and Sherfield Cave Stream. Preliminary results of these surveys suggest that H. sulphuria has maintained populations in small, mountain stream channels with spring-water sources. Of the four new locations for H. sulphuria, three were considered to be least-affected, watershed conditions, while one location was a small, agricultural stream in northwestern Arkansas (Little Wildcat Creek, Washington County).

At Sherfield Cave Stream, collections were made within a 15-m section of bank ca. 30 m from the cave opening. Specimens were collected from interstices of sediment-free, large gravel and cobble substrate at margins of the stream. Sherfield Cave is home to the largest colony of over-wintering Indiana myotis (Myotis sodalis) in Arkansas, and the stream provides habitat for cave isopods (Caecidotea) and the Ozark cave amphipod (Stygobromus ozarkensis; G. O. Graening and A. V. Brown, in litt.). The recent discovery of a H. sulphuria at Sherfield Cave Stream further highlights conservation efforts focused on this unique cave and stream system. The cave is protected through a landowner conservation easement and the surrounding land includes The Nature Conservancy Smith Creek Preserve. Therefore, this protection should provide effective conservation for this population of H. sulphuria.

In the Ozark National Forest, H. sulphuria was collected from a high gradient tributary to Richland Creek, which flows into Buffalo National River. Beetles were collected at this site from the underside of leaf packs in small pools with mineral substrate and small, shallow pools and crevices in bedrock. Some activity of beetles was observed under just one or two leaves in small (<10 cm diameter) depressions in the bedrock. A concern for this population is the forest road located parallel and ca. 15 m from the stream, with steep slopes between the road and stream. Recent studies conducted to document cave and karst fauna in the watershed of Buffalo National River have highlighted biological and habitat conservation in this region (Graening et al., 2006). The discovery of H. sulphuria in these associated surface waters provides an additional conservation need in this watershed. Furthermore, this

watershed has been affected by deforestation and confined-animal operations, and increased or sustained rates of these activities could have detrimental effects on H. sulphuria in these small, upland aquatic systems (Scott and Hofer, 1995; Graening et al., 2006).

Beetles at Hobbs State Park-Conservation Area were collected from a small, spring seep along the lower end of the Pigeon Roost hiking trail. Habitat at this location consisted of leaves and some gravel covering limestone bedrock. Collection sites were ca. 10 m downslope from the hiking trail, and therefore, conservation efforts should include placement of sensitive-habitat-area signs adjacent to the trail to eliminate hiking traffic near, and in, the stream. Due to the biological-conservation-based approach of Hobbs State Park-Conservation Area, this population will receive a similar level of protection as that provided by the location at Sherfield Cave Stream. Furthermore, these conservation actions within Hobbs State Park-Conservation Area would highlight and support efforts focused on protection of water quality for the adjacent Beaver Lake Reservoir, which is the primary municipal water supply for much of northwestern Arkansas. Future work should include surveys at all spring habitats in this 48.7-[km.sup.2] conservation area to determine additional occurrences of H. sulphuria.

One H. sulphuria was collected from Little Wildcat Creek, a stream dominated by agricultural land-use (71% livestock pasture). The beetle was collected during routine sampling of invertebrates associated with stream-restoration research in northwestern Arkansas. To date, we have not collected any other H. sulphuric from this site, and no beetle was found during a follow-up survey at this location. However, the inputs of spring-water and the dominant chert gravel substrate may provide adequate habitat in this system in spite of heavy agricultural land use throughout the watershed. The stream pool where we collected this one individual was fenced with no direct access by cattle, and because these beetles probably rely on stable stream margins and streambanks for development (including terrestrial pupation), cattle could be negatively affecting habitat of the beetle where access to the stream is not limited. We emphasize the importance of conservation measures at all locations for sustaining current populations of H. sulphuria; populations in watersheds associated with livestock may require special attention.

The bright coloration of the Heterosternuta (i.e., maculate dorsal surface with alternating dark and bright transverse, irregular bands) has been considered to correspond to the typical occurrence of this genus in spaces among rocks in unvegetated mineral substrate (Larson et al., 2000), with the alternating colors potentially providing a degree of protection from predators. A large series of the recently described H. phoebeae (Wolfe and Harp, 2003) and other Heterosternuta (H. wickhami and H. pulcher) with the same general coloration have been collected in recent surveys from this type of substrate in several drying pools in large streams, yet to date no H. sulphuric has been found in such habitat. The primary color pattern of many spring-specialist Hydroporinae that occur in densely shaded habitats is uniformly yellowish to brown dorsally (Larson et al., 2000), and the only genera that have been collected with H. sulphuric during our current surveys were the spring specialists Sanfzlippodytes (the type species described from a cave in Mexico) and Hydrocolus, both of which are entirely brown dorsally. Furthermore, the only significant co-occurrence of H. sulphuric with any previously collected Hydroporinae with the same general coloration was that of the type series of 33 specimens in 1955, where a group of 280 H. wickhami also was collected (Matta and Wolfe, 1979). Preliminary findings suggest that coloration of H. sulphuric could be unique in these spring-influenced systems, while multiple species of Heterostemuta with this coloration co-occur in the larger aquatic systems.

Habitat where H. sulphuric was collected in historical surveys included margins of large tributaries of the Buffalo National River (Wolfe and Harp, 2003; G. L. Harp, pers. comm.). We have not concluded surveys at those historic sites, and based on the limited number of springs visited during these current surveys, we cannot conclude that H. sulphuric is indeed primarily in spring systems. However, an interesting finding is that two historic sites for H. sulphuric (Beech Creek and Smith Creek) are just downstream from the population that was discovered at Sherfield Cave Stream. Although historical surveys have recorded low relative abundances of H. sulphuric among collected water beetles, populations may exist in the larger systems but are more difficult to locate because of the larger habitat area and potential lower densities. Additional surveys will address these issues and improve our understanding of habitat associations and life-history characteristics of H. sulphuric in the Ozark and Boston Mountain ecoregions.

Historical Distribution Records--Arkansas: Benton Co.: Sulphur Springs, 20 July 1955, no specific habitat data, 33 specimens collected by P. Spangler (Natural Museum of Natural History 97565). Izard Co.: West Lafferty Creek, 4 September 1988, one suspect female specimen collected by G. Harp. Searcy Co.: Long Creek at State Hwy 74, 28 June 1992, one positively identified female collected by G. Harp. Newton Co.: Beech Creek at State Hwy 21, 1 July 1992, one suspect female collected by G. Harp. Newton Co.: Smith Creek at State Hwy 21, 1 July 1992, one positively identified female collected by G. Harp.

New Distribution Records--Arkansas: Newton Co.: Buffalo National River, unnamed first-order tributary of Richland Creek, 30 September 2007, shallow pools and depressions and crevices in bedrock, 10 specimens collected by S. Longing and P. Bacon. 25 October 2007, same habitat, three specimens collected by S. Longing. Sherfield Cave Stream, 25 October 2007, margins of Sherfield Cave Stream in cobble substrate ca. 30 m below entrance of cave, 10 specimens collected by S. Longing. Washington Co.: Little Wildcat Creek, margin of pool in gravel substrate, one suspect female collected by S. Longing and T. Spencer. Benton Co.: Hobbs State Park-Conservation Area, 6 January 2008, spring habitat at the end of Pigeon Roost Trail, under leaves covering limestone bedrock, five specimens collected by S. Longing and P. Penny.

Three specimens from Sherfield Cave Stream were donated to R. Roughley (J. B. Wallis Museum, University of Manitoba). Two specimens from the unnamed tributary to Richland Creek were donated to E. Chapman (University of Kentucky). All other specimens were deposited in the University of Arkansas Arthropod Museum in the Dale Bumpers College of Agriculture and Life Sciences.

Funding for this project was provided by the Arkansas Game and Fish Commission (State Wildlife Grant Program, T26-R-2). Thanks to J. Anderson for providing access to Sherfield Cave. The assistance of E. Chapman, G. Harp, R. Roughley, and B. Wolfe with species identifications and suggestions on sampling the Hydroporinae is much appreciated. Thanks to G. Harp and E. Chapman for providing comments on the original draft of the manuscript.

Submitted 7 February 2008. Accepted 29 November 2008.

LITERATURE CITED

ANDERSON, J. E., EDITOR. 2006. Arkansas wildlife action plan. Arkansas Game and Fish Commission, Little Rock.

GRAENING, G. O., M. E. SLAY, AND C. BITTING. 2006. Cave fauna of the Buffalo National River. Journal of Cave and Karst Studies 68:153-163.

LARSON, D. J., Y ALARIE, AND R. E. ROUGHLEY. 2000. Predaceous diving beetles (Coleoptera: Dydscidae of the Nearctic region, with emphasis on the fauna of Canada and Alaska (D. J. Larson, Y Alarie, and R E. Roughley, editors). National Research Council of Canada Research Press, Ottawa, Ontario, Canada.

MATTA, J. F., AND G. W. WOLEE. 1979. New species of Nearctic Hydroporus (Coleoptera: Dytiscidae). Proceedings of the Biological Society of Washington 92:287-293.

NILSSON, A. N. 2007. Some necessary corrections of the spelling of species-group names within the family Dytiscidae. Zootaxa 1615:49-54.

SCOTT, D., AND K. HOFER. 1995. Spatial and temporal analysis of the morphologic and land-use characteristics of the Buffalo River watershed. Arkansas Water Resources Center Publication, University of Arkansas, Fayetteville 170:1-61.

WOLFE, G. W. 2000. Key to species of Heterosternuta of Canada and the United States. Pages 230-232 in Predaceous diving beetles (Coleoptera: Dydscidae of the Nearctic region, with emphasis on the fauna of Canada and Alaska (D. J. Larson, Y Alarie, and R E. Roughley, editors). National Research Council of Canada Research Press, Ottawa, Ontario, Canada.

WOLFE, G. W., AND G. L. HARP. 2003. A new species of predacious diving beetle, Heterosternuta phoebeae (Coleoptera: Dytiscidae), from the Ozark Mountains of Arkansas. Coleopterists Bulletin 57: 117-121.

SCOTT D. LONGING * AND BRIAN E. HAGGARD

Department of Biological and Agricultural Engineering, Division of Agriculture, University of Arkansas, 203 Engineering Hall, Fayetteville, AR 72701

Associate Editor was Joseph P. Shannon

* Correspondent. ozarkecoCa3gmail.com
TABLE 1--Current and historical locations (1-9, see Fig. 1) for beetle
surveys in northern Arkansas. Easting and northing are UTM coordinates
(NAD83 datum). Numbers in parentheses for the co-occurring
Hydroporinae are the actual numbers of beetles collected.

Location Stream Easting Northing County

1 Little Wildcat 388965 4000306 Washington
 Creek
2 Hobbs State Park- 415821 4017907 Benton
 Conservation
 Area
3 Sherfield Cave 464392 3977996 Newton
 Stream
4 Tributary of 507508 3969294 Searcy
 Richland Creek
5 Sulphur Springs 369409 4038603 Benton
6 Beech Creek 463453 3980364 Newton
7 Smith Creek 464120 3978125 Newton
8 Long Creek 551614 3971086 Searcy
9 West Lafferty 605834 3971086 Izard
 Creek

Location Record Number of
 Heterosternuta
 sulphuria
 collected

1 Current 1
2 Current 5
3 Current 10
4 Current 13
5 Historical 33
6 Historical 1
7 Historical 1
8 Historical 1
9 Historical 1

Location Co-occurring
 Hydroporinae

1 None collected
2 Sanfilippodytes (9)
3 None collected
4 Sanfilippodytes (5),
 Hydrocolus (1)
5 Heterosternuta
 wickhami (280)
6 Heterosternuta
 ouachita (21),
 H. phoebeae (22),
 H. pulchra (10),
 H. wickhami (9).
7 Heterosternuta
 phoebeae (3),
 H. wickhami (9),
 Neoporas
 striatopunctatus (1)
8 Heterosternuta
 ouachita (1),
 H. phoebeae (1)
9 Heterosternuta
 wickhami (87),
 H. pulchra (1),
 H. ouachita (1)
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Author:Longing, Scott D.; Haggard, Brian E.
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1U7AR
Date:Sep 1, 2009
Words:2214
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