Reviews in Fish Biology and Fisheries 13: 91–110, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
91
Morphometric variation of wild trout populations from northwestern Mexico (Pisces: Salmonidae) Gorgonio Ruiz-Campos1 , Faustino Camarena-Rosales1 , Alejandro Varela-Romero2 , Sergio S´anchez-Gonz´ales3 & Jorge De La Rosa-V´elez4 1 Facultad
de Ciencias, Universidad Aut´onoma de Baja California, Apdo. Postal 1653, Ensenada, Baja California, 22800, M´exico; Mailing address: PMB 064, P.O. Box 189003-064, Coronado, CA 92178, USA (E-mail:
[email protected]); 2 Departamento de Investigaciones Cient´ıficas y Tecnol´ogicas de la Universidad de Sonora, Apdo. Postal 1819, Hermosillo, Sonora, 83000, M´exico; 3 Escuela de Biolog´ıa, Universidad Aut´onoma de Sinaloa, Apdo. Postal 264, Culiac´an, Sinaloa, 80010, M´exico; 4 Facultad de Ciencias Marinas, Universidad Aut´onoma de Baja California, Apdo. Postal 1653, Ensenada, Baja California, 22800, M´exico Accepted 5 August 2003
Contents Abstract Resumen Introduction Study area Materials and methods Trout sampling Morphometric analysis Results and discussion Morphometric variation of wild trout populations from northwestern Mexico Variation and patterns of coloration Distributional and taxonomical considerations Acknowledgements References
page 91 92 92 92 93
98
109 110
Key words: morphometrics, northwestern Mexico, Oncorhynchus, variation, wild trout
Abstract Morphometric variation of 17 wild trout populations of the genus Oncorhynchus from northwestern Mexico was analyzed. We used 25 standardized morphometric characters following a box truss protocol. In the discriminant function analysis (DFA) of the examined specimens (n = 214), grouped by drainage, the canonical root 1 explained 88.1% of the total variation. Sixteen linear characters allow distinguishing O. mykiss nelsoni (Sierra San Pedro Mártir [SSPM]) from O. chrysogaster and O. mykiss sspp. (Sierra Madre Occidental [SMO]). Two distinctive groups of populations were recognized on the basis of the squared Mahalanobis’ distances, one for the SSPM (O. m. nelsoni) and the other for the SMO. The latter group is divided into four subgroups: (1) O. chrysogaster (Río Fuerte and Río Culiacán) and O. mykiss ssp. (Río Piaxtla); (2) O. mykiss sspp. (Río San Lorenzo, Río Baluarte, and Río Acaponeta); (3) O. mykiss sspp. (Río Yaqui and Río Mayo); and (4) O. chrysogaster (Río Sinaloa). In the DFA among populations within each taxon, the canonical variable 1 accounted for 41.8% of the total variation for O. m. nelsoni, 59.4% for O. chrysogaster, and 43.8% for O. m. sspp.
92 Resumen Se analiz´o la variaci´on morfom´etrica de 17 poblaciones de truchas silvestres del g´enero Oncorhynchus del noroeste de M´exico. Veinticinco medidas lineales estandarizadas fueron utilizadas siguiendo un protocolo de enrejado. En el an´alisis de funci´on discriminante (AFD) de 214 especimenes examinados y agrupados por cuenca hidrol´ogica, la ra´ız can´onica 1 explic´o el 88.1% de la variaci´on total. Diecis´eis caracteres lineales permiten distinguir a O. mykiss nelsoni (SSPM) de O. chrysogaster y O. mykiss sspp. (SMO). Dos grupos distintivos de poblaciones fueron reconocidos con base en las distancias cuadradas de Mahalanobis, uno para la SSPM (O. m. nelsoni), y el otro, para las truchas de la SMO. Este u´ ltimo grupo est´a dividido en cuatro subgrupos: (1) O. chrysogaster (r´ıos Fuerte y Culiac´an) y O. m. ssp. (R´ıo Piaxtla); (2) O. m. sspp. (r´ıos San Lorenzo, Baluarte y Acaponeta); (3) O. m. sspp. (r´ıos Yaqui y Mayo); y (4) O. chrysogaster (R´ıo Sinaloa). En el AFD entre poblaciones dentro de cada tax´on, la variable can´onica 1 explic´o el 41.8% de la variaci´on total para O. m. nelsoni, 59.4% para O. chrysogaster, y 43.8% para O. m. sspp.
Introduction For at least a century, the native trout of the genus Oncorhynchus have been known to inhabit certain streams of the Pacific and the Gulf of California drainages in northwestern Mexico (Meek, 1904; Evermann, 1908). These trout include two nominal species, the coastal rainbow trout (Nelson’s trout) O. mykiss nelsoni (Evermann, 1908) in the western slope of the SSPM, Baja California (Evermann, 1908; Snyder, 1926; Ruiz-Campos and Pister, 1995) and the Mexican golden trout O. chrysogaster (Needham and Gard, 1964) in the SMO (Río Fuerte, Río Sinaloa, and Río Culiacán drainages) from Chihuahua and Durango (Needham and Gard, 1959, 1964; Miller, 1950; Behnke, 1992; 2002; Hendrickson et al., 2002); other undescribed subspecies of rainbow trout (hereafter named “other rainbow trout”) also occur north and south of the range of the Mexican golden trout (Smith, 1984, 1991; Behnke, 1992, 2002; Nielsen et al., 1996, 1998). Currently, O. m. nelsoni and O. chrysogaster have been respectively categorized as “of special concern” and “threatened” by the Mexican government due to their low abundances and confined distributions (SEMARNAT, 2002). Needham and Gard (1959) analyzed meristic and morphometric variation of native trout populations from several localities in the northwestern region of Mexico. Their analysis was based on 243 voucher specimens and considered 28 linear measures expressed in thousandths of the standard length. Only four of these measurements were found to be significant for future studies of variation: least interorbital width, head length, distance from occiput to tip of snout, and length of the adipose fin.
The increasing establishment of nonnative rainbow trout hatcheries (O. m. irideus) in the headwater stream tributaries of the ríos Yaqui, Mayo, San Lorenzo, Presidio, Baluarte, and Acaponeta currently represents one of the main factors threatening the genetic integrity of the native trout populations in the SMO because of hybridization and competition (Behnke, 2002). Likewise, the environmental disturbance of these streams due to anthropogenic activities (e.g., pollution by rural communities and sawmills, logging, diversion of flows and mining) has decreased habitat quality for the trout and other native fish (Hendrickson et al., 2002). From October 2000 to September 2001, we carried out several collecting expeditions to various mountain streams in the states of Baja California, Sonora, Chihuahua, and Durango, as part of a study on the genetic and morphometric characterization of the wild trout populations from northwestern Mexico. For the present study, we analyzed 25 linear characters of the box truss morphometric protocol (Bookstein et al., 1985) for a total of 17 wild trout populations from northwestern Mexico, to evaluate and characterize the variation, within and among these populations, as well as to detect useful diagnostic characters for separation of the taxa recognized there.
Study area The streams sampled in the present study (Figure 1) belong to two major hydrologic areas of northwestern Mexico: the Baja California Drainage and the Northern Pacific Drainage (Tamayo and West, 1964).
93 The Baja California Drainage includes the streams that rise on the western slope of the SSPM and drain toward the Pacific ocean. These coastal streams are represented by the arroyos [ríos] San Rafael, San Telmo, and Santo Domingo, which have perennial flows in their headwaters, but become intermittent in their middle and lower courses during extremely dry conditions (Yruretagoyena-Ugalde, 1992; RuizCampos and Pister, 1995). The Pacific Drainage is represented by the large rivers that rise on the western slope of the SMO, cross the costal lowlands from Sonora to central Nayarit, and finally empty into the Gulf of California. In southern Sonora and northern Sinaloa, these large rivers possess a complex regime with two periods of maximum discharge, one during the summer rainy season and the other, although less important, in January and February, when occasional winter cyclonic rains (“equipatas”) and snow melting from the higher mountains produce some runoff. The most important rivers of this hydrologic complex are (from north to south): Yaqui, Mayo, Fuerte, Sinaloa, Culiacán, San Lorenzo, Piaxtla, Presidio, Baluarte, and Acaponeta (Tamayo and West, 1964; Figure 1).
Materials and methods Trout sampling Trout sampling was carried out between October 2000 and September 2001 in 17 mountain streams belonging to 12 drainages from northwestern Mexico (Figure 1). The sampling sites are situated in elevations ranging from 560 m at the SSPM to 2,637 m above sea level at SMO (Table 1). Simultaneous to the trout sampling, measurements of water quality were performed at different points of each study stream with Hydrolab Scout 2 (Hydrolab Co., Austin, Texas) multiparameter equipment, which recorded simultaneously temperature (◦ C), pH, conductivity (mS/cm), and dissolved oxygen (mg/l). The average values of physical-chemical variables in the different streams are presented in Table 1. The geographic location of each collecting site was determined using a GPS system. Names and hydrographic boundaries of the studied streams were based on 1:250,000 topographic maps published by the Instituto Nacional de Estadística, Geografía e Informática (INEGI). Trout were captured along 200 m-transects of each stream with AC Smith-Root 15-B POW electrofishing
equipment. Hook and line was also used for those streams where sampling with electrofishing was difficult (e.g., Arroyo La Grulla at SSPM and Arroyo El Concheño at upper Río Mayo). Considering that most of the sampled populations exhibited low densities, we selected a sample of 10– 15 adult individuals per locality for morphometric analysis. In the field, the recently captured specimens were individually labeled and placed in plastic bags, kept on dry ice until arrival at the laboratory, and then stored in a freezer at –80 ◦ C. Morphometric analysis Twenty-five linear measures (M) based on box truss protocol (Bookstein et al., 1985) were considered in the present morphometric analysis (Figure 2), and described as follows: snout tip to upper jaw tip (M1-2), snout tip to occiput (M1-3), upper jaw tip to occiput (M2-3), upper jaw tip to pectoral fin origin (M2-4), upper jaw tip to dorsal fin origin (M2-5), occiput to pectoral fin origin (M3-4), occiput to dorsal fin origin (M3-5), pectoral fin origin to dorsal fin origin (M45), pectoral fin origin to pelvic fin origin (M4-6), pectoral fin origin to posterior insertion of dorsal fin (M4-7), dorsal fin origin to pelvic fin origin (M5-6), basal length of dorsal fin (M5-7), pelvic fin origin to posterior insertion of dorsal fin (M6-7), pelvic fin origin to anal fin origin (M6-8), pelvic fin origin to adipose fin origin (M6-9), posterior insertion of dorsal fin to anal fin origin (M7-8), posterior insertion of dorsal fin to adipose fin origin (M7-9), anal fin origin to adipose fin origin (M8-9), basal length of anal fin (M8-10), anal fin origin to posterior insertion of adipose fin (M8-11), adipose fin origin to posterior insertion of anal fin (M9-10), basal length of adipose fin (M9-11), posterior insertion of anal fin to posterior insertion of adipose fin (M10-11), posterior insertion of anal fin to mid caudal base (M10-12), and posterior insertion of adipose fin to mid caudal base (M11-12). In order to reduce the biases associated with the shrinking of the specimens due to the fixation in formalin, as well as to use these same specimens for future genetic analysis, all linear measures were made in millimeters (mm) on slightly thawed fresh individuals with fins pined out by one of the authors (GRC). The measurements were made on the left side of each specimen using a digital caliper (precision, 0.01 mm) connected to a PC. The measured specimens were stored in an ultra-freezer for subsequent obtention of tissue samples. After sampling the
Arroyo San Rafael at Rancho Garet, SSPM, B.C. Arroyo San Rafael between Garet and Mike’s Sky ranches, idem. Arroyo San Rafael at Rancho Mike’s Sky Arroyo El Potrero at Rancho El Potrero, idem. Arroyo San Antonio de Murillos at Rancho San Antonio, idem. Arroyo La Zanja immediately before the confluence with Arroyo San Antonio de Murillos, idem. Arroyo San Antonio de Murillos at Rancho San Antonio, idem. Arroyo La Grulla at La Grulla meadow, idem. Arroyo La Presita, a tributary of Arroyo La Cueva, Mesa de Tres R´ıos, Sonora.
Locality
Taxon
O. m. nelsoni
O. m. nelsoni
O. m. nelsoni O. m. nelsoni
O. m. nelsoni
O. m. nelsoni
O. m. nelsoni
O. m. nelsoni
O. m. ssp.
Code
∗1
∗1
∗1
2
∗3
∗3
∗3
4
9
1386
1397
1395
1393
1396
1392
1390
1389
1388
Cat. Num. (UABC)
Yaqui (Bavispe)
Santo Domingo
Santo Domingo
Santo Domingo
Santo Domingo
Santo Domingo
San Rafael
San Rafael
San Rafael
Drainage
23-IV-01
22-IX-01
31-III-01
26-I-01
26-I-01
25-I-01
14-X-00
14-X-00
14-X-00
Date (d/m/y)
115◦ 38 42.7
115◦ 37 47.4
108◦ 43 12.6
30◦ 48 59.4
29◦ 48 32.8
115◦ 37 35.0
30◦ 54 59.8
30◦ 49 10.0
115◦ 38 42.7
115◦ 38 42.7
30◦ 54 59.8
30◦ 54 59.8
115◦ 47 16.3
115◦ 46 38.3
115◦ 36 09.4
Longitude (S)
31◦ 05 51.7
31◦ 04 53.9
31◦ 04 27.2
Latitude (N)
1640
2034
560
560
560
892
1250
1351
1363
Altitude (m)
11.42
15.26
17.9
10.56
10.56
13.78
15.49
12.99
9.16
Temp. (◦ C)
09:37
12:45
09:45
15:30
17:00
11:15
14:05
11:50
09:05
Time
7.42
8.89
8.38
NM
NM
NM
NM
8.26
8.26
pH
0.255
0.156
0.384
NM
NM
NM
0.383
0.388
0.386
Cond. (mS/cm)
4.73
2.46
11.26
NM
NM
NM
3.88
2.24
3.51
Oxyg. (mg/l)
Table 1. Geographic location and ecological information of the collecting sites of wild trout in the northwestern Mexico (October 2000–September 2001. Physicochemical parameters expressed as average values
94
O. m. ssp.
O. m. ssp.
O. m. ssp.
O. m. ssp.
O. chrysogaster
O. chrysogaster
O. chrysogaster
10
11
12
13
5
6
7
Arroyo San Antonio above Rancho San Antonio, idem. Arroyo Los Pescados ca. Rancho La Primavera, a tributary of Arroyo La Cueva, idem. Arroyo El Potrero de Gil at rancho of the same name, Basaseachic, Chihuahua. Arroyo El Concheño ca. El Concheño town, idem. Arroyo Verde ca. Puerto Blanco, 0.3 km upstream of the bridge (El Vergel-Guadalupe and Calvo freeway), Chihuahua Arroyo Casa Quemada or Macheros, Guadalupe y Calvo, idem. Arroyo La Onza at Rancho La Onza, a tributary of R´ıo Turuachi, idem.
Taxon
Code
Locality
Table 1. Continued
1391
1368 1373
1377
1363
1364
1379
1378
Cat. Num. (UABC)
Fuerte
Sinaloa
Fuerte
Mayo
Mayo
Yaqui (Bavispe)
Yaqui (Bavispe)
Drainage
25-VI-01
25-VI-01
24-VI-01
29-IV-01
27-IV-01
25-IV-01
23-IV-01
Date (d/m/y)
Longitude (S) 108◦ 44 03.6
108◦ 40 48.1
108◦ 12 06.7
108◦ 13 12.7
106◦ 29 13.9
107◦ 01 33.1
106◦ 40 40.6
Latitude (N) 29◦ 52 46.5
29◦ 48 57.2
28◦ 14 24.2
28◦ 19 11.9
26◦ 16 31.0
26◦ 03 20.0
25◦ 57 19.3
2418
2550
2280
1972
2080
1571
1610
Altitude (m)
16.35
16.37
18.41
14.4
21.9
17.49
16.68
Temp. (◦ C)
17:45
11:08
11:10
11:13
13:48
10:13
13:10
Time
7.11
6.86
7.87
7.09
8.28
8.25
8.26
pH
0.097
0.104
0.130
0.262
0.128
0.298
0.317
Cond. (mS/cm)
4.65
4.71
4.91
NM
5.75
6.29
6.15
Oxyg. (mg/l)
95
O. m. ssp.
O. m. ssp.
16
17
1368 1376
1367 1371
1374
1370
1387
1375
Cat. Num. (UABC)
Piaxtla
San Lorenzo
Acaponeta
Presidio
Baluarte
Culiac´an
Drainage
01-VIl-01
30-VI-01
29-VI-01
28-VI-01
28-VI-01
26-VI-01
Date (d/m/y)
105◦ 24 47.4
105◦ 47 31.4
106◦ 00 08.3
23◦ 38 53.3
24◦ 28 02.3
24◦ 18 57.5
105◦ 33 33.4
23◦ 42 12.7
105◦ 25 37.2
106◦ 40 42.2
25◦ 48 17.4
23◦ 45 38.3
Longitude (S)
Latitude (N)
∗ Localities combined due to their geographic proximities. ∗∗ Trout collected (n = 4) but not measured, this site is not shown in Figure 1, NM = Not measured.
O. m. ssp.
15
O. m. ssp.
O. m. ssp.
14
∗∗
O. chrysogaster
8
Arroyo Mesa San Rafael, a tributary of Arroyo Agua Blanca, at Soledad de Agua Blanca, idem. Arroyo CoscomateChavarr´ıa, between Coscomate and Chavarr´ıa towns, El Salto Durango. Arroyo El Agua ca. rainbow trout hatchery at Ejido La Victoria, idem. Arroyo Los MetatesLos Laureles at Ejido El Brillante, idem. Arroyo La Sidra, upstream of the trout hatchery at Ejido Vencedores, Dimas, Durango. Arroyo La Quebrada or El Pinto, ca. La Traspana, idem.
Taxon
Code
Locality
Table 1. Continued
2638
2270
2560
2560
2400
2240
Altitude (m)
16.17
22.755
12.3
20.14
18.08
18.69
Temp. (◦ C)
19:11
15:59
09:33
13:24
13:45
11:16
Time
6.04
8.19
7.28
7.24
7.11
8.17
pH
0.092
0.112
0.114
0.093
0.083
0.180
Cond. (mS/cm)
6.005
4.61
5.45
5.18
5.23
4.785
Oxyg. (mg/l)
96
97
Figure 1. Geographic locations of trout sampling in the northwest of Mexico (period of October 2000 to September 2001). See Table 1 for the geographical coordinates of the collecting sites.
Figure 2. Landmarks based on Bookstein et al. (1985) box truss protocol for the morphometric analysis of wild trout populations from northwestern Mexico. See text for description of landmarks.
tissue for genetic analyses, all the specimens were fixed with 70% ethanol and finally deposited in the Ichthyological Collection of the Facultad de Ciencias, Universidad Autónoma de Baja California (UABC) at Ensenada (Table 1). The best model for the standardization of the morphometric data of each taxon was the regression of Elliott et al. (1995). This model removes the size component from the shape measurements (allometry), and is defined by the following equation: Ms = Mo
(Ls/Lo )b , where Ms = standardized measurement, Mo = measured character length (mm), Ls = overall (arithmetic) mean standard length (mm) for all individuals from all populations of each taxon, Lo = standard length (mm) of specimen, and “b” was estimated for each character from the observed data using the non-linear equation, M = a Lb . Parameter “b” was estimated as the slope of the regression of log Mo on log Lo , using every fish in every population of each taxon.
98 The standardized morphometric values of the 17 studied wild trout populations were analyzed within each taxon and among drainages, and compared by means of discriminate function analysis (DFA) using Statistica 5.0 software (StatSoft, Inc., Tulsa, OK, 1995). This multivariate analysis allowed us to determine which combinations of variables (distances) discriminated best among populations and detected which populations were the most different.
Results and discussion The three taxa of the genus Oncorhynchus sampled here (Behnke, 2002) and their respective drainages of distribution are as follows: Nelson’s trout O. mykiss nelsoni from the SSPM (Río Santo Domingo and Río San Rafael drainages); Mexican golden trout O. chrysogaster from the SMO (Río Fuerte, Río Sinaloa, and Río Culiacán drainages); and other rainbow trout (O. mykiss sspp.) from the SMO, occurring north and south of the range of Mexican golden trout (Río Yaqui, Río Mayo, Río Piaxtla, Río San Lorenzo, Río Presidio, Río Baluarte, and Río Acaponeta drainages). Morphometric variation of wild trout populations from northwestern Mexico The descriptive statistics (means, standard errors, and coefficient of variation) of the standardized morphometric data of 25 linear measures for 17 wild trout populations are presented in Table 2 and Figure 3. Nelson’s trout For this taxon inhabiting the SSPM, the linear characters with the highest CV were associated with M1-2 (snout tip to upper jaw tip) and M9-11 (basal length of adipose fin), with respective values of 12.5% and 21.0%. The lowest CV were registered for two linear characters: M2-5 (upper jaw tip to dorsal fin origin) and M4-5 (pectoral fin origin to dorsal fin origin) with values of 3.9% each (Table 2). In the DFA applied to four populations of this taxon, only one of 25 examined characters (M1-2) was statistically significant (p < 0.01, Table 3). The value of tolerance, which oscillates between 0 when fully redundant to 1.0 when it is not, varied for the different characters examined, with the highest values (> 0.5) for M4-6 (pectoral fin origin to pelvic fin origin), M4-7 (pectoral fin origin to posterior insertion of dorsal fin),
and M7-9 (posterior insertion of dorsal fin to adipose fin origin). The canonical variables (cv) 1 and 2 accounted for 41.8% and 35.4% of the total variation, respectively (Table 4). In cv1, three characters exerted the major effects: M3-4 (occiput to pectoral fin origin, Y1 = –0.8292), M8-11 (anal fin origin to posterior insertion of adipose fin, Y1 = 1.2045) and M9-10 (anterior insertion of adipose fin to posterior insertion of anal fin, Y1 = –0.8728). For cv2, two linear characters were the most important to explain this variation: M12 (snout tip to upper jaw tip, Y2 = –1.1812) and M7-8 (posterior insertion of dorsal fin to anal fin origin, Y2 = –0.8628). The predicted classification of individuals among populations was 83.9% for Arroyo San Rafael, 92.9% (Arroyo El Potrero), 80.0% (arroyos San Antonio [de Murillos]-La Zanja), and 84.6% (Arroyo La Grulla). The tree diagram resulting from the squared Mahalanobis’ distances, which indicate the extent of discrimination among populations, revealed a shorter distance between those of Arroyo San Rafael and Arroyo San Antonio-La Zanja (Figure 4A). Mexican golden trout In this taxon the highest CV were mainly correlated with two linear characters, M7-9 (posterior insertion of dorsal fin to adipose fin origin) and M9-11 (basal length of adipose fin), with values of 13.5% and 23.1%, respectively (Table 2). Likewise, the lowest CV were detected for M2-5 (upper jaw tip to dorsal fin origin) and M4-7 (pectoral fin origin to posterior insertion of dorsal fin), with respective values of 2.73% and 3.22%. In the DFA applied to four populations of this taxon, none of 25 examined characters was statistically significant (p < 0.01, Table 3). The value of tolerance of the characters varied from 0.044 (M4-5, pectoral fin origin to dorsal fin origin) to 0.330 (M2-4, upper jaw tip to pectoral fin origin) (Table 3). The cv1 and cv2 accounted for 59.4% and 22.7% of the total variation, respectively (Table 4). The cv1 was most strongly correlated with four linear characters: M1-3 (snout tip to occiput, Y1 = –1.836), M2-3 (upper jaw tip to occiput, Y1 = 1.668), M4-5 (pectoral fin origin to dorsal fin origin, Y1 = –2.551) and M4-7 (pectoral fin origin to posterior insertion of dorsal fin, Y1 = 1.794). For cv2, two linear characters account for a great part of this variation: M3-5 (occiput to dorsal fin origin, Y2 = –1.574) and M6-9 (pelvic fin origin to adipose fin origin, Y2 = 1.255).
16.04 21.78 19.21 13.37 48.90 21.13 38.29 39.17 38.65 52.36 27.09 16.43 25.91 23.89 40.07 25.61 25.10 21.94 12.61 22.17 14.80 2.64 13.96 18.98 17.36
84.92
43
15
86.41 112.18
15
49.41
88.82
15
48.42
3
48.67
5
49.40
10
47.28
15.34 15.05 20.48 20.17 17.94 17.80 12.23 14.03 50.78 50.25 21.94 22.48 41.23 40.39 43.29 41.81 40.92 40.07 55.88 54.13 32.48 31.61 16.99 16.56 30.35 29.24 24.48 24.42 41.26 39.73 28.28 29.77 22.37 23.55 23.43 23.05 12.35 12.57 23.61 23.61 16.97 17.53 3.56 4.11 15.18 15.32 19.62 20.75 19.80 20.15
8
45.70
17.16 21.00 17.97 11.84 49.09 21.67 40.09 41.24 37.30 53.98 30.63 18.21 29.48 26.68 42.05 27.92 21.86 24.54 14.00 24.54 17.61 4.61 15.39 20.18 19.49
10
47.73
14.80 21.39 18.07 13.60 49.90 21.37 38.28 41.45 38.71 55.83 30.14 18.00 29.51 24.54 42.08 26.76 22.94 23.29 14.63 23.99 15.91 3.47 14.39 20.92 19.66
16.95 22.74 19.66 14.29 54.10 22.74 43.07 43.62 42.31 58.32 30.59 18.69 29.59 26.64 43.84 28.62 25.07 24.47 14.27 24.89 17.05 3.38 15.62 20.88 20.31
98
214
72.43 109.03
89.43 105.63 270.00 107.40
72.43
–
–
15.36 11.80 13.40 14.19 12.04 11.28 14.49 11.31 12.51 13.53 12.47 14.78 11.93 15.50 12.85 12.11 13.12 14.02 17.12 12.57 12.36 24.91 11.56 9.34 9.00
TOTAL CV
48.06 –
8.71 6.56 6.84 9.46 4.95 5.30 9.60 5.57 5.33 4.12 9.49 8.07 8.26 11.4 4.23 8.51 7.34 10.0 9.20 6.09 8.79 26.10 5.74 7.91 6.99
C.V.
87.73 126.91 122.60 132.05 177.09 122.32 118.04 127.57
17
47.80
17.07 20.05 18.19 13.32 50.04 22.02 40.44 41.27 39.19 53.21 27.25 15.51 26.26 24.45 40.28 23.78 24.43 22.73 12.99 22.96 15.53 3.12 14.06 20.14 19.21
17
–
94.46
14
47.95
15.95 22.32 18.06 13.45 49.87 20.27 37.31 37.92 36.55 51.71 25.96 16.19 25.04 21.60 38.91 24.34 24.02 21.51 12.20 21.36 14.24 2.54 13.95 20.35 19.35
16
177.00 157.00 203.14 180.00 203.14 179.00 116.80 120.65 135.75 179.00 201.00 156.00 132.09 106.86 149.42 221.00 205.42 133.69 148.00 270.00 270.00
5
48.20
16.36 21.39 18.46 13.18 49.84 21.24 39.18 40.16 39.64 53.23 26.58 16.17 25.55 23.11 39.66 25.92 24.77 21.86 12.57 22.52 15.14 3.02 14.07 19.32 18.11
O. mykiss sspp. 13 14 15
–
10
48.78
15.03 20.55 18.66 14.28 51.55 21.92 43.68 41.56 40.24 54.25 29.95 15.91 28.19 26.22 39.83 28.08 22.64 21.64 11.91 22.09 16.49 3.84 14.74 20.08 19.97
12
72.43
81.93 102.30
14
47.27
10.1 8.4 8.39 7.57 2.73 5.14 5.27 4.72 6.68 3.22 5.08 5.85 5.68 7.44 6.86 4.72 13.5 6.03 7.95 5.59 5.68 23.1 5.58 6.68 6.45
11
84.92 104.40
81.93 100.22 122.65
73
47.28
15.27 21.57 17.84 12.14 50.05 20.81 38.42 41.94 38.86 56.14 28.92 17.81 29.45 24.23 41.30 26.14 22.17 22.48 13.28 23.51 15.60 3.07 14.55 21.17 20.55
10
119.21
13
48.69
16.14 20.46 17.73 12.25 48.78 21.55 38.02 40.24 38.86 54.91 29.18 18.85 28.33 24.86 40.92 26.94 21.43 23.21 13.27 23.35 16.86 2.93 15.11 20.39 20.39
9
97.78 110.37 112.94 117.05 110.46 131.55 110.71
15
48.99
16.67 22.86 18.55 12.72 49.02 20.73 37.30 38.61 38.88 53.53 27.53 17.86 27.24 22.67 36.85 25.38 18.59 21.15 12.30 22.50 16.01 2.99 14.64 20.51 20.90
CV
146.03 134.23 147.56 159.92 146.56 137.32
14.00 19.45 16.02 13.01 48.30 19.40 39.04 40.17 39.73 54.36 27.76 17.75 27.12 25.74 41.99 27.15 25.12 23.17 12.67 23.52 16.04 2.87 14.85 20.67 19.47
O. chrysogaster 7 8
SL (ave.) SL (min) SL (max)
14
48.54
12.50 6.55 6.36 7.85 3.92 4.35 5.83 3.90 5.89 12.00 7.41 6.77 5.71 6.86 6.69 5.50 5.58 5.49 8.97 4.62 6.53 21.00 7.20 9.01 5.81
6
31
47.92
20.95 25.74 23.10 16.77 61.33 26.40 49.47 48.65 47.72 68.73 32.81 21.68 32.30 31.40 50.64 31.94 28.20 28.04 17.77 28.25 19.42 4.01 17.67 21.92 21.70
5
N
49.85
20.14 25.56 22.26 15.99 61.69 26.32 50.11 49.72 47.97 64.01 34.99 22.15 34.00 31.87 49.65 32.86 28.49 28.27 16.92 29.02 19.71 4.15 18.02 23.50 22.82
CV
49.37
19.29 25.62 22.43 16.65 64.79 25.82 51.42 51.58 50.15 65.87 35.37 21.32 34.45 30.46 50.35 33.50 27.81 28.69 16.44 28.80 19.57 3.05 17.96 21.51 22.10
O. mykiss nelsoni 3 4
CV
2
18.70 25.93 22.99 16.58 62.48 25.53 50.60 49.60 49.04 67.75 34.91 22.31 33.55 31.38 51.58 32.37 29.19 28.61 17.33 28.91 19.15 3.64 17.44 21.92 21.64
1
M1-2 M1-3 M2-3 M2-4 M2-5 M3-4 M3-5 M4-5 M4-6 M4-7 M5-6 M5-7 M6-7 M6-8 M6-9 M7-8 M7-9 M8-9 M8-10 M8-11 M9-10 M9-11 M10-11 M10-12 M11-12
CODE
Wild Populations
Table 2. Means and coefficient of variation (CV) of standardized morphometric characters (M) for 17 native trout populations from northwestern Mexico. (See codes for number of population and linear characters in Figure 1 and text, respectively). N = number of specimens examined, SL = no transformed standard length
99
100
Figure 3. Box plots of 18 significant standardized morphometric characters for 17 wild trout populations from northwestern Mexico. See description of morphometric characters in text.
101
Figure 3. Continued.
102
Figure 3. Continued.
The predicted classification of individuals was 100% for each population. Furthermore, the tree diagram resulting from the squared Mahalanobis’ distances for these populations revealed a shorter distance between the population of Arroyo Casa Quemada (Río Sinaloa) and those of Mesa San Rafael (Río Culiacán) (Figure 4B). Other rainbow trout In this complex of populations, the linear characters exhibiting the highest variation (CV) were M6-8 (pelvic fin origin to anal fin origin, 11.4%) and M9-11 (basal length of adipose fin, 26.1%) (Table 2), while those with the lowest variation were M4-7 (pectoral fin origin to posterior insertion of dorsal fin, 4.12%) and M6-9 (pelvic fin origin to adipose fin origin, 4.23%). In the DFA applied to 9 populations of this complex, four of 25 characters examined resulted statistically significant (p < 0.01): M1-2 (snout tip to upper jaw tip), M4-7 (pectoral fin origin to posterior insertion of dorsal fin), M8-9 (anal fin origin to adipose fin origin), and M11-12 (posterior insertion of adipose fin to mid caudal base (Table 3). The highest values of tolerance (> 0.5) were associated with M2-5 (upper
jaw tip to dorsal fin origin), M3-5 (occiput to dorsal fin origin) and M10-12 (posterior insertion of anal fin to mid caudal base). The cv 1 and cv2 accounted for 43.8% and 19.1% of the total variation, respectively (Table 4). In cv1 two characters have a major effect: M1-2 (snout tip to upper jaw tip, Y1 = –0.8369) and M9-10 (adipose fin origin to posterior insertion of anal fin, Y1 = 0.6322); while in the cv2 they were M4-7 (pectoral fin origin to posterior insertion of dorsal fin, Y2 = –0.9826) and M8-9 (anal fin origin to adipose fin origin, Y2 = 0.8307). The predicted classification of individuals among the nine populations of this complex was as follows: Arroyo La Presita [Río Yaqui] (80%), Arroyo San Antonio [Río Yaqui] (100%), Arroyo Los Pescados [Río Yaqui] (93.3%), Arroyo Potrero de Gil [Río Mayo] (94.1%), Arroyo El Concheño [Río Mayo] (100%), Arroyo Coscomate [Río Baluarte] (100%), Arroyo Los Metates [Río Acaponeta] (80.0%), Arroyo La Sidra [Río San Lorenzo] (100%), and Arroyo La Quebrada [Río Piaxtla] (90.0%). The tree diagram resulting from the squared Mahalanobis’ distances for these populations revealed two groups of populations, one represented by populations of the Río Yaqui and
0.0917
F (75,135) 2.2093
