<I>Chromis Enchrysura</I>

BULLETIN OF MARINE SCIENCE, 32(1): 151-165, 1982

GEOGRAPHIC VARIATION AND REDESCRIPTION OF THE WESTERN ATLANTIC DAMSELFISH CHROMIS ENCHRYSURA JORDAN AND GILBERT (PISCES: POMACENTRIDAE)

Alan R. Emery and William F. Smith-Vaniz

ABSTRACT Chromis enchrysura is characterized by the possession of I3 dorsal spines, usually 12 anal rays and a body depth of 45 to 62% standard length. The color pattern consists of a dark blue to gray body, with a pale or blue stripe that begins as a V on the snout and extends onto the dorsum, at least in juveniles; the caudal fin is pale, yellow or dusky. The species exhibits distinct geographic variation in several morphological and meristic characters. Multivariate discriminant analysis reveals that specimens from Brazil and Bermuda, Florida and Puerto Rico, the Carolinas and western Caribbean cluster respectively into three distinct populations. Univariate analysis confirms this but also suggests c1inal variation in a circle from North Carolina to Brazil and back to Bermuda. The explanation for this pattern of variation is unclear, but may be related to water temperature.

Six species of Chromis occur in the western Atlantic and five species have been reported from the eastern and central Atlantic and Mediterranean (Wood, 1977). The western Atlantic species can be divided into two groups, one with 13 dorsal spines and a gibbous body, and a second with more terete bodies and 12 dorsal spines. The deep bodied species, Chromis enchrysura Jordan and Gilbert, C. jiavicauda (Gunther), C. insolata (Cuvier) and C. scotti Emery, are conser- vative morphologically and after a few years in alcohol are often difficult to distinguish one from another. Several of these species exhibit marked size de- pendent changes in color and shape which further complicate identification. This study was begun to determine the taxonomic status of recently collected specimens of C. enchrysura from Bermuda that differed markedly from Florida specimens (Fig. I). Examination of numerous specimens from throughout the western Atlantic revealed that the species is highly variable geographically and that in his comparison of Chromis species Emery (1968) misidentified Brazilian specimens of C. enchrysura as C. jiavicauda. A redescription of C. jiavicauda, based on recently collected specimens from Bermuda, and comparison with other western Atlantic Chromis is given in Smith-Vaniz and Emery (1980). The femi- nine gender for Chromis follows Emery (1975).

METHODS

All measurements were made with dial calipers. In the description, the morphometric data are presented as percent standard length, recording the range, followed in parentheses by the mean. Right pectoral fin length is taken from the upper axil to the tip of the longest ray; right pelvic fin length includes any filamentous extension; caudal-fin lobe measurements are of the longest rays in each lobe, including any filamentous extensions; caudal concavity is the difference in measurement between longest and shortest caudal rays expressed as percentage of standard length; body depth is taken at the origin of the pelvic fins; interorbital width is taken at the narrowest point between the eyes; caudal peduncle depth is the shallowest measurement on the peduncle; predorsal, preanal and prepelvic lengths are defined as the distances between the tip of the snout and the origin of the respective fin; spines are measured from their base, even if the base is covered by scales; body width is measured at the widest point exclusive of an expanded belly; bony eye diameter is measured in an anteropos- terior direction (vertical measurement will give a smaller diameter). Terminal dorsal- and anal-fin elements when not divided to their bases were assumed to share a common pterygiophore and were counted as a single ray. 151 152 BULLETIN OF MARINE SCIENCE, VOL. 32. NO. I, 1982

The following institutional abbreviations are used in the material examined list: ANSP-Academy of Natural Sciences of Philadelphia. FMNH-Field Museum of Natural History, Chicago. MCZ- Museum of Comparative Zoology, Harvard University. ROM-Royal Ontario Museum, Toronto. UF-Florida State Museum, Gainesville. UMML-University of Miami, Rosenstiel School of Marine and Atmospheric Science. UMMZ-Museum of Zoology, University of Michigan, Ann Arbor. USNM-United States National Museum of Natural History.

Chromis enchrysura Jordan and Gilbert yellowtail reeffish Figures 1-3; Tables ]-7

Chromis enchrysurus Jordan and Gilbert, 1882a: 286 (original description; type-locality: "spewed up" by red snappers, at Pensacola, Fla.; allied to C.jlavicauda).-Jordan and Gilbert, ]882b: 940 (description).-Jordan and Evermann, ]898: 1548-1549 (description).-Nichols, 1920: 60 (allied to new species, C. bermudae).-Longley and Hildebrand, 1941: 176 (color description, specimens trawled in 40 fm., Tortugas, Fla.).-Breder, 1948: 198-199 (comparison, distribution, stomach contents of snappers and groupers). -Briggs, 1958:283 (compi]ed distribution).-Bullis and Thompson, 1965: 55 (reported from several Caribbean loca]ities).-Starck, 1968: 24 (listed, abundant at Alligator Reef, Fla., photograph).-Emery, ]968 (description, comparison, figure, photograph).-Emery, ]973 {ecology, distribution, behavior, osteology, diet).-Bai]ey et a!., 1970: 45 (listed).-Bright and Pequegnat, 1974:29, 37, 40, 46, 49 (Flower Garden Bank, Gulf of Mexico, depth distribution, photographs).-Smith et a!., 1975:8-9 (listed, abundant at the Florida Midd]e Ground).-Zeiller, 1975:84 (etymology of scientific name, color photograph).-Thresher, 1975: 30 (color, description, distribution, ecology, color photograph).-Smith, ]976: 18, 32, 64 (distribution, depth of occurrence, zoogeographic relationship to C. jlavicauda).-Sonnier et a!., 1976: 109(occurrence of large schools at Louisiana offshore reef).-Gilmore, 1977: 141(listed as abundant on reefs off Indian River Lagoon, F]a.).-Schwartz and Porter, 1977: 437 (occurrence on calico scallop bed off North Caro]ina).-Shipp and Hopkins, 1978: ] 19(abundant in De Soto Canyon, Gulf of Mexico).-Hastings, 1979:96 (recorded on offshore reefs off northwest F]orida, but not inshore at jetties). Chromis enchrysura, Walls, 1975: 264, 302 (description, figure, color photograph).-Hoese and Moore, 1977: 216 (description) and 77 (color photograph misidentification = C. insolata).- Smith-Vaniz and Emery, ]980: 211 (comparison with C. jlavicauda). Chromis jlavicauda (non Gunther), Bullis and Thompson, ]965: 55 (reported from Caribbean ]0- calities).-Emery, 1968(description, comparison, photograph). "Bicolor pomacentrid," Colin, 1974: 36 (Jamaica, observed at 70-]20 m depth). "Bicolor damselfish," Colin, 1976: 604 (Tongue-of-the-Ocean, Bahamas, observed at 109-116 m depth; "a species of Chromis believed to be same as species recently collected in Bermuda = C. enchrysurus and observed in Jamaica"). Diagnosis.-A species of Chromis distinguished by color and shape: body dark blue to gray with a pale (blue in life) stripe that begins as a V on snout and extends onto dorsum, at least in juveniles, and caudal fin yellow, pale or dusky; dorsal spines XIII; anal rays usually ]2; body depth 45 to 62% SL and caudal fin moderately forked. Description.-Body deep 31.2-45.5 (35.7) and laterally compressed 15.3-23.0 (]8.7); eye large 9.6-]4.3 (11.3); interorbital width 9.6-12.9 (10.7). Head smoothly rounded with convex forehead. Opercle with single large posterodorsally posi- tioned spine; preopercle smooth except at ventral angle where it is rough to slightly serrate. Pre orbital (lacrymal), second and third suborbital bones reflexed from cheek. Ventral margins of these bones smoothly concave from snout to posterior edge of lips, where convex angle occurs; remainder of suborbital bones adnate to cheek. Dorsal fin XIII (rarely XII), 10-13 (usually 12; x = 12.2). Fourth dorsal spine 18.6-22.8 (20.2); longest dorsal-fin ray ]8.4-32.5 (22.3); dorsal-fin base 58.1-68.0 (62.5). Anal fin II, ] 1-13 (usually ]2; x = ]2.0); first anal spine 7.7-]2.1 (7.7); second ]8.6-22.8 (20.2); longest anal-fin ray 16.7-23.9 (20.5); anal-fin base 24.3-29.9 (26.2). Caudal fin moderately forked, caudal concavity ]6.3-22.6 (19.2); upper EMERY AND SMITH-VANIZ: ATLANTIC DAMSELFISH POPULATIONS 153

Figure I. Photographs of specimens of Chromis enchrysura; A, Adult from Florida (photo courtesy W. A. Starck, II); B, Juvenile from FLorida (photo courtesy Miami Seaquarium); C, Adult from. Bermuda; D, Juvenile from Bermuda (photo C and D courtesy P. Colin). lobe longer than lower lobe, sometimes each lobe with filamentous extension. Three short, procurrent spines precede caudal rays of both lobes. Length of upper lobe 22.9-54.4 (35.7); lower lobe 22.9-44.2 (30.1); caudal peduncle depth 14.0-- 17.7 (15.6). Pectoral-fin rays 17-20 (usually 18 or 19; x = 18.2); length of pectoral fin 30.6- 38.7 (34.5). Pelvic fin 1,5; length of pelvic fin 31.2-45.4 (41.0); preanal length 66.1-74.0 (70.8); prepelvic length 41.5-50.1 (45.0). Scales large, strongly ctenoid, covering almost entire body. Tube bearing lateral-line scales 15-19 (usually 17; x = 17.0), in smoothly curved arch following 154 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I, 1982

• Chromis

• •

Figure 2. Closed symbols indicate geographic locations from which specimens of Chromis enchrysura were examined; open symbols where acceptable sight records or literature records noted their occurrence. dorsal contour of body and ending under level of last dorsal spine. Series of scales bearing neuromast pits continues ventrally from last tube-bearing scale to mid- line of body and thence to hypural area. Suborbital bones scaly, those on pre orbital slightly elongate vertically. These scales highly variable in number, attaining complete development when fish is ca. 45-50 mm SL; approximately 6-10 suborbital scales anterior to angle of jaw. Cheek with 3 major scale rows and 5-8 accessory scales below suborbital bones. Scales absent in area between nostrils and upper lips and just posterior to lower lips. Scales present on remainder of body, and extending onto basal two thirds to three fourths of dorsal, anal and caudal fins, but restricted to basal one fourth of pectoral fin. Pelvic fins naked, but with large axillary scale laterally and two enlarged scales medially between fins. Pectoral fin without free rays. Pelvic fin with membranous connection, hid- den by axillary scale and extension of enlarged interpelvic scales, from belly and extending 5-10% of length of innermost ray. Color in C. enchrysura varies with age, behavioral state and geographic location. In life, Florida adults are bright to dull blue dorsally, with pale blue or gray venter. Caudal fin usually yellow or pale, but occasionally dusky yellow. Anal fin usually blue anteriorly and pale or yellow posteriorly. Dorsal fin blue except second dorsal fin with pale distal margin. Pectoral fin transparent with thin dark margin dorsally, and small black axillary spot. Pelvic fins blue. Thin,

-7 Figure 3. Hubbs and Hubbs diagrams plotting those characters of Chromis enchrysura against location where a clinal variation was suggested (18 of 25 characters). Range, standard deviation, twice the standard error of the mean and the mean are plotted. EMERY AND SMI TH-YANIZ: ATLANTIC DAMSELFISH POPUL ATIONS 155

I " II , :1 I" Ii j " '" ilL!j •

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I ~d I ! :1 ., HIL! I II I,:, ,. . ' ~ ~ ~ i~ii~~_. _" lldil~~ i ji~i _~~I 5; ~i 156 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I, 1982

Table I. Geographic variation in fre:juencies of lateral-line scales and pectoral-fin rays in Chromis enchrysura

Lateral-Line Scales

Locality 15 16 17 18 19 N SD

Bermuda 4 8 I 14 16.9 0.53 North Carolina 3 I 5 17,6 0.89 South Carolina 2 9 4 15 17,1 0.64 Florida 15 ]5 17.0 Puerto Rico 2 2 17.0 Western Caribbean 2 9 2 15 16.7 0.82 Brazil and Guyana 6 ] 7 ]7.1 0.38 TOTAL 2 8 52 9 2 73 16.99

Pectoral Rays

Locality 17 18 19 20 N SD

Bermuda 6 7 14 ]8.5 0,88 North Carolina 2 3 5 17.6 0.55 South Carolina 4 24 29 17.9 0.41 Florida I 13 13 18.1 0.28 Puerto Rico I I 2 17.5 0.71 Western Caribbean 2 9 7 18 18.4 0.67 Brazil and Guyana 8 8 19.0 TOTAL 10 56 24 91 18.20 bright electric blue line extends from V-shaped origin on snout to dorsal margin of eye and continues dorsolaterally across body ending below middle of spinous dorsal fin. Additional area of brilliant blue occurs on dorsal sclera of eye in naked area between nostrils.

Table 2. Geographic variation in frequencies of dorsal- and anal-fin rays in Chromis enchrysura

Dorsal Rays

Locality 10 II 12 13 N x SD

Bermuda 2 12 14 12.9 0.36 North Carolina 2 3 5 11.6 0.55 South Carolina 3 22 3 29 ]1.9 0.59 Florida I 14 15 I\.9 0.27 Puerto Rico I 1 10 12.5 0.71 Western Caribbean 15 2 18 12.0 0.43 Brazil and Guyana 3 5 8 12.6 0.52 TOTAL 7 60 23 91 12.16

Anal Rays Locality 10 11 12 13 N x SD

Bermuda 13 ] 14 12.1 0.27 North Carolina 4 I 5 12.2 0.45 South Carolina 5 21 2 29 I\.9 0.59 Florida I 14 15 11.9 0.26 Puerto Rico 2 2 12.0 Western Caribbean 4 14 19 12.0 0.41 Brazil and Guyana I 7 8 11.9 0.40 TOTAL II 75 5 92 11.97 EMERY AND SMITH-VANIZ: ATLANTIC DAMSELFISH POPULATIONS 157

Table 3. Geographic variation in frequencies of upper and lower gill rakers in Chromis enchrysurus

Upper Gill Rakers

Locality 6 7 10 N SD

Bermuda 3 6 4 ]4 8.2 0.89 North Carolina I 2 2 5 8.0 1.22 South Carolina I 10 ]5 3 29 7.7 0.71 Florida 4 5 5 1 15 7.2 0.94 Puerto Rico I 1 2 8.0 1.4] Western Caribbean ]0 8 ] 19 7.5 0.66 Brazil and Guyana 4 2 2 8 7.8 0.89 TOTAL 6 33 37 ]4 91 7.44

Lower Gill Rakers

Locality \7 18 \9 20 2\ N SD

Bermuda 2 7 4 I 14 18.3 0.83 North Carolina I 2 2 5 19.2 0.84 South Carolina 2 5 16 5 29 18.9 0.88 Florida ] 8 5 ] ]5 ]8.4 0.77 Puerto Rico I ] 2 18.5 0.71 Western Caribbean ] 4 14 ]9 ]8.7 0.63 Brazil and Guyana 2 5 1 8 ]8.6 1.06 TOTAL 10 23 46 II 91 18.67

In juveniles, life colors are brighter and caudal fin bright yellow or occasionally white. Dorsolateral blue stripe more extensive, often reaching base of posterior end of second dorsal fin. Marked variations of above color patterns occur in specimens from Bermuda. In adults, body gray and caudal fin pale or dusky. No trace of yellow present on any of fins and blue stripe does not extend beyond posterior margin of eye. In juveniles, caudal fin and ventral region of body may be uniformly white. The bright blue stripe that extends posteriorly from eye much broader than in Florida specimens and body gray-blue instead of dark blue. In specimens stored in alcohol, pigment patterns are usually discernible. Dor- sally body dark brown and dusky or pale brown ventrally. Caudal fin may be dusky, pale or transparent. Blue stripe above eye usually pale brown and con- trasts with underlying pigment. In old specimens, alcohol preservative de-em- phasizes the presence of this stripe. As is typical of some other pomacentrids, males of C. enchrysura undergo marked change in color during courtship, and usually retain such colors during nest-guarding activities. These colors are not retained in death, however. This courtship coloration involves counter-shading. Superimposed on the normally dark blue dorsum is a series of large inverted triangular patches of powderpuff blue, giving a totally different appearance to fish. Similar large pale patches also occur in courting males of Chromis insolata and C. scotti. Placement and number of patches varies with each species, see Emery (1973) for details. Color pattern during courtship and nest-guarding has not been observed in C. flavicauda. Distribution.-The geographic distribution of Chromis enchrysura (Fig. 2) is not well established. The preference of this species for deep water (at depths pre- cluding normal SCUBA diving) and hard, rugged bottom substrates, which are not easily sampled with nets, makes observation and collection difficult. The species ranges from Bermuda and North Carolina off Cape Fear to mid Brazil. 158 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I, 1982

Table 4. Summary of geographic variation in morphometries expressed as percentage of standard length in Chromis enchrysura

Bermuda North Carolina South Carolina Character N SD N x SD N x SD

Pelvic fin length 14 38.4 2.71 5 34.1 2.05 29 34.9 \.72 Pectoral fin length 14 36.5 \.93 5 3 \.4 0.98 29 33.6 1.25 Lower caudal lobe length 14 35.4 3.40 5 28.6 1.04 29 29.8 1.97 Upper caudal lobe length 14 43.7 4.34 5 32.7 1.06 29 33.1 2.74 Longest dorsal-fin ray 14 26.3 3.35 5 ]9.5 1.54 29 21.9 1.70 Longest anal-fin ray 14 2\.6 1.87 5 20.3 2.04 29 ]8.9 1.39 Body depth 14 27.5 1.28 5 52.8 1.55 29 51.7 1.81 Ana] base length ]4 27.5 1.28 5 25.9 0.83 29 25.9 0.75 Dorsal base length 14 64.5 2.]2 5 61.2 0.90 29 62.7 1.56 Interorbital width ]4 I\.6 0.77 5 9.9 0.73 29 10.4 0.37 Cauda]-peduncle depth 13 ]6.3 0.68 5 16.1 0.25 29 15.4 0.61 Pre-ana] length 14 7 \.0 1.81 5 73.6 1.49 29 69.5 2.35 Pre-dorsa] length 14 43.3 1.81 5 38.7 1.89 29 39.9 1.72 Pre-pelvic length 14 43.5 1.98 5 49.2 1.41 29 44.3 2.75 4th dorsal spine length 14 20.3 1.53 5 18.0 1.89 29 20.9 1.27 Ist anal spine length 12 8.5 0.79 5 8.3 0.68 29 10.0 1.22 2nd anal spine length 14 21.7 1.67 5 19.2 1.16 29 2\.8 \.05 Body width 14 20.2 1.33 5 18.0 1.24 15 17.] 0.64 Eye diameter 14 12.5 1.01 5 9.6 0.61 29 10.5 0.69

Between these two limits, the species is largely restricted to continental slopes along North and South Carolina, Florida, the Gulf of Mexico, western Caribbean, Guyana, and Brazil. It is less commonly collected from insular localities of the West Indies. We have examined specimens from Puerto Rico and it has been reported from Curac;ao (Luckhurst, pers. comm.), Jamaica and the Bahamas (Colin, 1974; 1976). The latter two published records (see preceding synonymy) were originally listed as uncertain identifications but can now be unequivocally assigned to C. enchrysura (Colin, pers. comm.). Its occurrence off Brazil may be a result of a sponge reef (rather than a coral reet) (Collette and Riitzler, 1977). Ecology and Behavior.-Chromis enchrysura typically occurs in deep reef areas associated with outcrops of sponge or coral. Our records indicate a minimum depth (observation only at Looe Key Reef, Fla.) of 5 m and a maximum of approximately 146 m (collection off Puerto Rico). Most observations and collections of the species are from depths of 40 to 70 m. Based on depth data from Emery (1973) and that given in our Material Examined section, the approximate depth of greatest abundance is 52 m. Our daytime observations suggest that C. enchrysura is colonial to some ex- tent and tends to occur near small outcrops, rather than in major reef areas. In Florida small juveniles often school near major reef areas with juveniles of Chromis insolata and C. scotti. Larger juveniles and sub-adults form groups, but not schools (sensu stricto), and are usually associated with small rocky outcrops or sponges, often in open sandy areas. These "groups" range in number from a few individuals to 200. Sonnier et al. (1976) mentioned "large schools" of C. enchrysura but did not elaborate. Emery (1973) found juveniles and adults abundant (up to 10 per m2) in deep water (45 m). This observation and the fact that adults were not seen in shallow water suggest that juveniles do not survive (or stay) to adulthood in shallow areas. EMERY ANO SMITH-VANIZ: ATLANTIC DAMSELFISH POPULATIONS 159

Table 4. Continued

Florida Puerto Rico Western Caribbean Brazil & Guyana Total N SD N x SO N x SO N SO N

15 35.2 2.07 2 35.3 0.21 19 35.5 2.39 7 35.4 3.07 91 35.62 15 33.6 0.94 2 36.2 0.49 19 35.8 2.09 8 34.8 0.92 92 34.54 15 30.8 \.29 2 33.8 0.71 16 3\.2 2.02 6 3\.9 \.03 87 31.30 14 34.0 0.97 2 37.6 0.78 15 34.0 2.06 7 37.7 1.88 86 35.58 15 20.8 2.07 2 24.6 0.71 19 2\.7 1.25 8 24.8 2.76 92 22.38 13 20.4 1.42 2 22.0 0.42 18 21.7 \.69 8 21.7 1.73 89 21.51 14 52.4 4.02 2 54.9 4.95 19 51.9 1.90 8 53.8 2.68 91 52.84 15 25.9 0.93 2 27.3 0.85 19 25.7 1.52 8 26.2 1.28 92 27.16 15 62.1 1.46 2 63.3 \.98 19 61.5 \.94 8 61.9 2.68 92 62.50 15 10.7 0.54 2 10.5 0.71 19 10.5 0.58 8 I\.7 0.63 92 10.74 15 15.1 0.67 2 16.0 1.06 19 15.2 0.69 8 16.1 0.55 91 15.55 15 70.8 1.34 2 71.3 1.29 19 72.0 2.36 7 70.6 1.88 91 70.82 15 41.0 1.22 2 42.5 1.20 19 40.3 2.15 8 44.6 0.90 92 41.08 15 43.9 2.37 2 45.5 1.77 19 47.1 3.12 8 43.7 1.27 92 44.93 15 20.5 1.51 2 20.9 1.13 19 20.6 1.54 8 17.9 1.77 92 20.26 14 8.8 0.95 2 9.2 0.21 19 9.7 1.00 8 8.4 1.00 89 9.29 14 20.4 1.20 2 19.8 2.26 19 21.8 1.65 8 20.7 1.06 91 21.29 15 19.6 \.21 2 18.3 \.27 19 18.3 0.94 8 20.1 1.25 78 18.83 15 11.7 0.89 2 12.0 1.06 19 11.3 1.45 8 12.3 0.61 92 11.31

In both Florida and North Carolina, adults and subadults were observed as much as 2.5 m off the bottom, but spent most of their time within 1 m of the substrate. The height they rise above the bottom when feeding on plankton seems to be related to water clarity (visibility) and the body size of individuals. In Bermuda, our observations suggest that adults rise 2 m above bottom. Geographic Variation.-Specimens from Bermuda, North Carolina, South Car- olina, Florida, Puerto Rico, western Caribbean, Brazil and Guyana, were examined to assess geographic variation. Six counts (Tables 1-3) and 19 measurements (Table 4) were compared. The means of each character for a given population were compared with those of the nearest population geographically to determine if there were any significant differences. The significance of the observed differences for each variable was calculated using Student's "t" test (Ta- ble 5). Greater differences were observed in the measurements than in the counts. The greatest number of highly significant differences was found between the Bermuda and North Carolina populations. The least number of significantly different characters was found between the populations from South Carolina, Flor- ida and the western Caribbean. The North and South Carolina populations differed in ten characters, but were still more similar than was the Bermuda population. More characters (13) were different comparing Brazil and the western Caribbean populations. A comparison of the specimens from Brazil and Bermuda, however, revealed a relatively low level of difference. Only eight characters differed (including several with P-values exceeding the .01 level). In view of the above, it might be argued that there are two populations of C. enchrysura: 1) a central population extending from North Carolina to the western Caribbean and 2) a peripheral population including specimens from Bermuda, Guyana and Brazil (no specimens were available from the Lesser Antilles). The color pattern of the Bermuda population also distinguishes it from the "central" population. The color pattern of Florida specimens, however, differs from those from Jamaica 160 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I, 1982

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Table 6. Multiple discriminant analysis of six groups of damselfish (Chromis enchrysura) based on 20 mensural and 6 meristic characters. Discriminant functions are presented as standardized discriminant coefficients

Discriminant Function

Variables II III IV V

Standard length 0.237 -0.013 -2.851 -1.301 0.211 Pelvic fin length -0.080 0.631 0.217 0.103 -0.323 Pectoral fin length -0.452 0.855 1.402 -1.229 0.883 Lower caudal lobe length 0.039 -0.075 0.0\6 0.015 0.074 Upper caudal lobe length 0.429 -0.342 0.075 0.342 -0.867 Longest dorsal-fin ray 0.481 0.382 -0.231 -0.338 -0.364 Longest anal-fin ray -0.223 0.297 0.429 -0.207 0.902 Body depth 0.205 -1.061 -0.331 0.151 -0.206 Anal base length -0.152 0.542 -0.439 0.327 -0.499 Dorsal base length -0.606 -1.680 -0.029 0.433 -1.393 Interorbital width 0.113 0.309 -0.008 -0.279 -0.\15 Caudal peduncle depth 0.516 1.017 -1.353 1.432 0.\01 Pre-anal length -0.482 -0.34\ 2.254 1.480 -0.385 Pre-dorsal length -0.027 0.332 -0.710 -0.228 1.417 Pre-pelvic length 0.088 0.784 0.620 0.086 0.352 4th dorsal spine length -0.001 -1.493 0.746 0.279 -0.393 Ist anal spine length -0.244 0.232 -0.327 -0.551 0.004 2nd anal spine length -0.181 0.877 0.287 -0.524 -0.527 Body width -0.042 -0.343 0.505 -0.660 0.756 Eye diameter 0.246 -0.4\7 0.017 0.645 -0.069 Lateral line scales -0.004 0.0\6 0.078 -0.110 -0.000 Pectoral-fin rays 0.182 0.117 0.130 -0.166 0.134 Dorsal-fin rays 0.158 0.069 0.122 -0.234 -0.\19 Anal-fin rays 0.067 -0.169 -0.076 0.403 0.006 Upper gill rakers 0.029 -0.058 0.226 0.295 -0.189 Lower gill rakers -0.086 0.063 -0.132 0.034 -0.011 Eigenvalue 13.777 4.27] 2.887 2.657 2.334 Relative percentage 53.14 16.47 11.14 10.25 9.00 Probability P = 0.001 P = 0.001 P = 0.001 P = 0.001 P = 0.001

and the Carolinas, in lacking distinct counter-shading, and a bright yellow tail. Unfortunately, the life coloration of Guyana and Brazilian specimens has not been observed. As further test of the impression that there were at least two populations of C. enchrysura represented in the samples, a multivariate comparison was made using multiple discriminant analysis (SPSS QR6.0). In this analysis, mensuraJ characters were used as simple measurements instead of converting them to per·· cent of standard length as is traditional, because discriminant analysis requires variables of normal distribution, and ratios derived from mensural characters are not necessarily distributed normally. Standard length was included in the analysis as a variable to provide a check on the possibility that the samples were significantly different only due to the size composition of the specimens analysed from each location. Such a difference, if it occurred, could be the result of real differences in sizes of individuals in the separate regions or could result from sampling bias: the analysis does not distinguish between the two. The first two functions accounted for approximately 70% of the discrimination (Table 6), the remaining three axes each accounted for approximately 10%. An index of importance was developed in which the coefficient was developed from the standardized discriminant function: each coefficient was transformed into a 162 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I. 1982

Table 7. An index of the discrimination provided by each variable, ranked on importance. See text for details

Variable I ndex of Discrimination

I Dorsal base length 9.53 2 Caudal peduncle depth 8.6] 3 Pre-anal length 8.4] 4 Pectoral fin length 8.29 5 Longest dorsal ray 5.80 6 Standard length 5.75 7 Upper caudal lobe length 5.68 8 Pre-dorsal length 4.57 9 2nd anal spine length 3.98 10 Body depth 3.87 II Longest anal ray 3.78 12 Body width 3.62 13 Eye diameter 3.52 14 1st anal spine length 3.39 15 Anal base length 3.16 16 4th dorsal spine length 2.97 17 Pre-pelvic length 2.66 18 Pectoral rays 2.28 19 Pelvic fin length 2.08 20 Dorsal rays 2.00 21 Interorbital width 1.82 22 Lower gill rakers 1.30 23 Anal rays 1.25 24 Upper gill rakers .90 25 Lower caudal lobe length .55 26 Lateral line scales .19 proportion of the total absolute value of the coefficients in each discriminant function, weighted by the discriminating ability of the function, then summed across the function (Table 7). The five most influential discriminating characters are: dorsal base length, caudal peduncle depth, preanal length, pectoral fin length, and the length of the longest dorsal fin ray: standard length ranks only sixth. Thus, it is most unlikely that discrimination is dominated by size. Subsequent analyses were performed using each variable transformed as a ratio of SL (not necessarily distributed randomly), and also as a residual value from a regression line of the variable against SL (almost certainly distributed randomly and not suffering from a size component problem). In each case, plotting the first two axes of discrimination (Fig. 4) reveals that the smallest degree of separation exists between specimens from Puerto Rico, North Carolina, South Carolina and the western Caribbean. Florida specimens also comprise a discrete group, but one which is close to the others. A distinct separation from this body of specimens is represented by the Bermuda and Brazilian specimens, which form distinct clusters close to each other. The multivariate analysis supports, in part, the hy- pothesis suggested by the univariate analysis. There are three populations, one represented by the specimens from Bermuda, Guyana and Brazil, one represented by the specimens from Florida and Puerto Rico and one represented by the remaining specimens. If the observed geographic variation in Chromis enchrysura is largely due to environmental influences rather than genetic differences, consistent trends in meristic and morphometric characters would be expected. An examination of the EMERY AND SMITH-VANIZ: ATLANTIC DAMSELFISH POPULATIONS 163

Z 1 0 I- U Z ::::> 0 LL.

I- Z « -1 z :!! a:- u CJ) -2 C

-1 0 1 2 DISCRIMINANT FUNCTION 1 Figure 4. Centroid C. represents mean volume for each population) and exterior boundaries for data from various Caribbean localities of Chromis enchrysura are shown using discriminant Functions I and 2. A, Brazil; B, Bermuda; C, Florida and Puerto Rico; D, North Carolina; E, Western Caribbean; F, South Carolina.

"direction" of variation using "Hubbs and Hubbs" diagrams (Fig. 3) reveajed that longer fins and robust bodies characterized the peripheral populations and that decreases in fin length and body robustness are correlated with latitude. Variations in meristic characters are also dinal in some cases, but are not consistent in direction. The Bermuda population represents an anomaly in that its_ characteristics are more "southern" than those of the Brazilian population. We do not know what environmental factors in combination with varying de- grees of reproductive isolation might account for the dinal geographic variation observed in Chromis enchrysura. Surface salinity would not appear to qualify: Brazil has the highest (36-37%), but Bermuda and the western Caribbean share the low ranges of salinity (35-36%), (Sverdrup et aI., 1942). There is a variation in average temperature that crudely approximates the pattern of the variation in C. enchrysura characters. In mid-winter (January) the average temperatures in Bermuda and Brazil and Guyana are 28°C, in the western Caribbean, Cuba and Florida, 24°_28°C, in South and North Carolina, 20°-24°C (Sverdrup et aI., 1942). An inversion of this trend occurs in the summer. It is possible that this combination of temperature regimes has a major influence on fin length and body form and meristic characters, but such a relationship would require substantiation through experimentation.

Material Examined.-Data are presented in the following format: museum catalog number; latitude; longitude; number of specimens; (SL range length in mm); depth; collection date. An asterisk precedes material used in the morphometric analyses. 164 BULLETINOFMARINESCIENCE,VOL.32, NO.1, 1982

BERMUDA.*ANSP 134052; 32°25'N, 64°56'W; 7 (62.0-81.0); 61-70 m; 7 Aug. 1975. *ANSP 134053, 32°27'N, 64°53'W; 5 (67.2-88.2); 56-61 m; 28 July 1975. *ANSP 134054; 32°23'N, 64°53'W; 1 (40.0); 61 m; 8 Aug. 1975. *ANSP 134055; 3r27'N, 64°54'W; I (42.5); 56 m; 24 July 1975. CAROLINAS.*UF 23860; 30023'N, 79°01'W; 2 (79.9-83.0); 59-66 m; 17 May 1964. *UF 23861; 30056'N, 80020'W; 3 (67.4-81.7); 62-66 m; 7 May 1964. *UF 23862; 32°47'N, 78°33'W; 7 (83.6-88.2); 33-35 m; 27 Jan. 1963. *UF 23863; 3r45'N, 78°33'W; 10 (57.7-89.2); 37-42 m; 27 Jan. 1963. *UF 23864; 31°49.5'N, 7~34.5'W; I (72.9); 77 m; 1963. *UF 23865; 33°07'N, 77°44'W; I (7); 88 m; 5 Dec. 1960. *UF 23866; 30039'N, 80017'W; 6 (73.4-95.6); 40-42 m; 19 Jan. 1960. *USNM 151929; 33°50'N, 7T50'W; 5 (78.8-86.0); 36-40 m; 29 May 1949. USNM 155684; 31°00'N, 80030'W; 1 (77.6); 7; 13 Mar. 1940. FLORIDA. *ANSP 138132; IT52'N, 67°I5'W; 2 (77.3-82.6); 146 m; 23 Sept. 1976. MCZ 49179; 24°36'N, 83°11'W; 7 (48.5-68.5); 55 m; 18 Oct. 1966. ROM 26395; 30ol7'N, 80015'W; 2 (80.2-85.3); 46 m; 29 Jan. 1966. UF 21069; 26°58.5'N, 83°24.5'W; I (65.2); 7; 29 Apr. 1974. UF 28763; 30052'N, 80018'W; I (90.2); 38-40 m; 17 Jan. 1960. UF 28765; 29°59'N, 80°34'W; 4 (77.3-80.4); 35 m; 13 June 1960. UF 28768; 30042'N, 80006'W; ] (83.7); 55-73 m; 18 April 1961. UF 28769; 29°52'N, 80032'W; I (81.5); 35-38 m; 19 July 1961. UF 28770; 29°56'N, 80028'W; 2 (76.0-77.0); 38 m; I May 1974. UF 28771; 30058'N, 80000'W; 1(71.4); 49-60 m; 15 May 1963. UF 28772; 24°29'N, 83°13'W; 1(74.3); 60- 64 m; 30 Oct. 1960. UF 28773; 29°58'N, 80032'W; 1(72.8); 38-40 m; 5 May 1960. UF 28774; 25°01'N, 80019'W; I (69.0); 82-84 m; 25 Oct. 1960. UF 28776; 30046'N, 80oI6'W; 3 (55.2-67.6); 40 m; 15 July 1963. UMML 6883; 24°43'N, 80037'W; 9 (47.0-85.3); 7; 22 May 1960. UMML 17455; 24°33'N, 83°IO'W; 6 (51.1-73.8); 68 m; II April 1965. UMML 17610; 24°26'N, 82°58'W; 1 (67.2); 69 m; 12 April 1965. UMML 17661; 24°32'N, 83°20'W; 2 (59.8-63.2); 71 m; 12 April ]965. *UMML 19333; 24°55'N, 80040'W; 10 (56.9-59.0); 40 m; 9 July ]965. UMML 28406; 25°00'N, 80030'W; 1(38.0); 43 m; 16 April 1970. UMML 33289; 24°30'N, 81°00'W; I (20.2); 7; spring, 1959. UMML 33290; 26°00'N, 8r50'W; 1(68.6); 37 m; 28 June 1965. *UMML 33291; 28°40'N, 85°()()'W; 10 (67.2-85.6); 55 m; 16 Dec. 1952. USNM 30871; Pensacola, Florida; 30026'N, 87°12'W; 2 (51.8-53.5) (syntypes); 7; no date. *USNM 131581; 26°40'N, 82°52'W; 3 (52.7-56.5); 49 m; 19 Mar. 1885. *USNM 142891; 29°30'N, 85°00'W; I (61.4); 48 m; 7 Feb. 1885. PUERTORICO. ANSP 138132; 17°58'N, 6T20'W; 2 (77.3-82.6); 146 m; 23 Sept. 1976. WESTERNCARIBBEAN.*FMNH 66953; 16°39'N, 81°59'W; 3 (50.8-60.1); 110m; 22 Aug. 1957. *MCZ 42059; 21°50'N, 86°38'W; 12 (52.1-85.1); 55 m; 12 June 1962. UF 23865; 21°50'N, 86°38'W; 9 (58.0- 75.4); 55 m; 12 June 1962. *UMML 10987; 21°50'N, 86°34'W; 10 (58.8-87.5); 55 m; 12 June 1962. UMMZ 174079; 22°23'N, 900]6'W; I (58.0); 60 m; 10 May 1958. UMMZ 174152; 23°36'N, 8T58'W; 1 (85.0); ?; 18 May 1958. BRAZIL. FMNH 66955; 01037'N, 46°45'W; 7 (51.0-96.7); 115-119 m; 18 Nov. ]957. FMNH 66957; 07°35'N, 56°57'W; 4 (37.0-77.8); 84-92 m; I Sept. 1958. *FMNH 66969; Or35'N, 48°]4'W; I (69.2); 97 m; 15 Nov. 1957. *FMNH 66971; 01025'N, 46°47'W; 2 (55.1-59.0); 82 m; 18 Nov. 1957. *FMNH 66972; 04°02'N, 50020'W; I (58.6); 91 m; 14 Nov. 1957. *FMNH 66973; Or40'N, 47°56'W; 2 (83.8- 87.2); 115 m; 15 Nov. 1957. GUYANA.*FMNH 66975; 08°15'N, 58°I7'W; 2 (73.0-80.8); 71-91 m; 31 Aug. 1958. LOCATIONUNKNOWN.UMML ]9052; 4 (35.1).

ACKNOWLEDGMENTS

We express our thanks to the following individuals (abbreviations correspond to the institutions cited in the methods section) who made specimens in their care available for this study: R. K. Johnson, FMNH; K. E. Hartel and K. F. Liem, MCZ; G. W. Burgess and C. R. Gilbert, UF; P. L. Colin, University of Puerto Rico; C. R. Robins, UMML; R. M. Bailey, UMMZ; V. G. Springer, USNM. Particular thanks is due to F. Emery (ROM) who counted and measured most of the specimens. The manuscript was criticized and discussed by E. J. Crossman and R. Winterbottom of the ROM. We acknowledge with special thanks the assistance of A. Baker and R. Gibson (ROM) with statistical anal ysi sand interpretati on of ou r data.

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DATE ACCEPTED:March 24, 1981.

ADDRESSES: (A.R.E.) Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Can- ada and (W.F.S.- V.) Academy of Natural Sciences at Philadelphia, 19th and the Parkway, Phila- delphia, Pennsylvania 19103.