Academic journal article The American Midland Naturalist

Population Structure of an Endemic Species of Yellowcheek Darter, Etheostoma Moorei (Raney and Suttkus), of the Upper Little Red River, Arkansas

Academic journal article The American Midland Naturalist

Population Structure of an Endemic Species of Yellowcheek Darter, Etheostoma Moorei (Raney and Suttkus), of the Upper Little Red River, Arkansas

Article excerpt

ABSTRACT.-The yellowcheek darter, Etheostoma moorei (Raney and Suttkus), is an endemic species of the upper Little Red River, Arkansas. Population estimates over the past two decades have identified an 80% reduction in numbers. Seventeen presumptive loci and six meristic characters were analyzed for 85 individuals to determine the relatedness of populations from three headwater streams. Genetic distances, based on allozyme analysis ranged from 0.000 to 0.213, with each stream population partitioning into distinct subpopulations. Turkey Fork individuals had high genetic distance values from Middle and South Fork individuals. None of the six meristic features studied demonstrated significant differences between stream sites. These findings and previous ecological and life history studies all suggest that the Turkey Fork and Middle/South Fork populations be treated as unique management units.

INTRODUCTION

Approximately one third of the North American freshwater fish species have declined to the point that they are in need of protection (Moyle and Cech, 2000). One percid species in decline is the yellowcheek darter, Etheostoma moorei (Raney and Suttkus), a species that is endemic to four headwater streams of the Little Red River in Arkansas (Raney and Suttkus, 1964). Much of the known range of this species was inundated by the formation of Greers Ferry Lake beginning in 1962. Raney and Suttkus (1964) predicted that upper reaches of headwater streams (eg., Middle, South, Archey and Turkey Forks) would become sanctuaries for this species as Greers Ferry Lake became flooded. Each stream flows directly into Greers Ferry Lake, which has served as an isolating barrier for the past four decades. A postinundation study by Robison and Harp (1981) resulted in a total estimate of 60,000 individuals of this species in the four streams. Suitable habitat for the yellowcheek darter in these headwater streams has declined due to reduced flow, with recent estimates of a decline of 80% in numbers (Wine et aL, 2001). Bottlenecking, a sudden and dramatic decline in numbers, has been associated with genetic drift and rapid species change (Nei, 1987). Our objective was to use allozyme and meristic features to describe the population structure of the yellowcheek darter. We predicted that partitioning of genetic diversity and meristic characters would be consistent with previously reported life history differences that have been described (McDaniel, 1984) among populations of the species.

METHODS

Twelve sample locations were initially proposed within the known range of Etheostoma moorei in four headwater streams of the Little Red River. Due to low population densities sample locations were restricted to four sites from Middle Fork [sample size [n] = 54], two sites from South Fork (n = 27) and a single site from Turkey Fork (n = 4) (Fig. 1). The collected fish were frozen in liquid nitrogen and returned to the laboratory, where they were analyzed or immediately refrozen at -70 C. Voucher specimens have been deposited in the ichthyology collection of the Arkansas State University Museum of Zoology (ASUMZ).

Genetic analysis.--Skeletal muscle was homogenized in equal volumes (w/v) of 0.1 M Tris-HCl buffer (pH 7.0). Electrophoresis of homogenate was performed on cellulose acetate plates at 200 volts for 30-40 min in TG buffer (0.025M Tris; 0.192M Glycine) on ice (2 mA/plate). Twelve enzyme systems containing 17 putative loci proved suitable for analysis. The enzymatic loci were as follows: alcohol dehydrogenase (Adh-A; E.C. No.1.1.1), aspartate aminotransferase (mAat-A, sAat-A; E.C. No. 2.6.1.1), dipeptidase (Pep-1, Pep-2; E.C. No. 3.4.13.11), fumarate dehydrogenase (Fum-A; E.C. No. 4.2.1.2), glucose-6-phosphate isomerase (Gpi-A, Gpi-B; E.C. No. 5.3.1.9), isocitrate dehydrogenase (sIdh-A; E.C. No. 1.1.1.42), lactate dehydrogenase (Ldh-A; E.C. No. 1.1.1.27), malate dehydrogenase NAD+ (mMdh-A, sMdh-A; E.C. No. 1.1. …

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