GEOGRAPHIC VARIATION IN THE FIRST PLEOPOD OF THE FORM I MALE DWARF CRAYFISH, CAMBARELLUS PUER HOBBS (DECAPODA, CAMBARIDAE)
BY
CARLENE L. CHAMBERS,JAMES F. PAYNE and MICHAEL L. KENNEDY1) Department of Biology, Memphis State University, Memphis, Tennessee 38152, U.S.A.
INTRODUCTION The range of the dwarf crayfish, CambarellllJ puer Hobbs, extends to south- eastern Texas and Louisiana and north into southern Missouri and Illinois along both sides of the Mississippi River (Page & Burr, 1973; Hobbs, 1974; Reimer & Clark, 1974). Various studies of the life history (Penn, 1950; Black, 1966), ecology (Penn, 1950), and behavior (Penn & Fitzpatrick, 1963; Penn & Black, 1963) of this species have been conducted; Chambers et al. (1979) reported inter- locality variation in C. puer using 10 morphological characters. They presented patterns of morphological variations and concluded that environmental influence was greater on characters of body size than on those of body shape. Hobbs (1958) noted that despite shortcomings, the first pleopod of the male is the most useful taxonomic and evolutionary character yet discovered and that insofar as is known, it is stable and little affected by ecological factors. While Hobbs and many others have used the first pleopod of form I males as a primary taxonomic character, there has been no attempt to examine variation of this character using the univariate and multivariate statistical techniques employed in this investigation. The purpose of this study was twofold: to examine geographic variation in the first pleopod of C. puer form I males by using univariate and multivariate statistical techniques and to determine the influence of selected environmental variables upon morphological variation.
MATERIALSAND METHODS Form I males of C. puer were studied from 20 localities throughout the range (fig. 1). Specimens were collected in Shelby and Lauderdale counties, Tennessee by sampling in sloughs and ditches with delta-ring dip nets. These were preserved in 70% ethyl-alcohol for later examination. Additional specimens were examined from collections of the Natural History Survey of Illinois, the United States National Museum, and from the personal collection of Dr. Joe Black, McNeese
1) Inquiries should be addressed to the junior authors. 170
State University. A total of 140 form I males was analyzed; sample sizes from these 20 localities are given in figure 1.
Fig. 1. Localities for form I males of Camharellu,rpuer Hobbs used in the study of interlocality variation. Sample sizes for each locality are: 1 = 4, 2 = 7, 3 = 7, 4 = 15, 5 = 7, 6 = 6, 7 = 11, 8 = 4, 9 = 6, 10 = 18, 11 = 3, 12 = 4, 13 = 6, 14 = 8, 15 = 7, 16 = 5, 17 = 12, 18 = 3, 19 = 3, 20 = 4.
All measurements were made with an ocular micrometer mounted in a Bausch and Lomb binocular dissecting microscope and recorded to the nearest 0.01 mm. Characters included: length of cephalothorax, length of first pleopod, length of central projection, length of caudal process, length of mesial process, distance between apices of central projection and mesial process, and distance between apices of caudal and mesial processes (fig. 2). Each measurement was converted to a