Descriptions of nest construction and reproductive behaviors of Nocomis ... asper); N. micropogon (with N. micropogon, N. platyrhynchus and N. raneyi); and N.
SE SQ UI CE N tEN NFA L
AMERICAN MIDLAND NATURALIST JULY 1991 VOLUME 126
Pi;L’JisIie4bythe Lfnwersity bNofre Dame, Notre Dame Indiana
Am. MidI. Nat. 126:103—110
Reproductive-behavioral Phylogenetics of Nocomis Species-groups EUGENE G. MAURAKIS, WILLIAM S. WOOLCOTT o MARK H. SABAJ Biology Department, Unioersity of Richmond, Richmond, Virginia 23173
ABsTR.ACT.—Descriptions of nest construction and reproductive behaviors of Nocomis species, identified from field observations and laboratory analysis of video tapes, are used to evaluate previous species-group designations (biguttatus, leptocephalus and rnicropogon) based on morphology. Three behavioral synapomorphies, the three-stage process of nest construction (excavating a concavity, forming a platform and building a mound), pit fanning of spawning troughs and pits with the anal fin of nesting males, and circle swims (reported for the first time) support the monophyly of Nocomis. Nocomis biguttatus and N. leptocephalus form a monophyletic group based on two behavioral synapomorphies (spawning pit exca vation and covering eggs after spawning).
INTRODUCTION Lachner (1946) described the morphology and life history (including feeding and repro ductive behaviors) of the cyprinid chubs Nocomis biguttatus, N. micropogora and N. lepto. cephalus. Designating the same three fishes as nominal species, Lachner and Jenkins (1971) organized the presently recognized seven pebble nest-building Nocomis species into three morphologically distinct species-groups: N. biguttatus (with N. biguttatus, N. effusus and N. asper); N. micropogon (with N. micropogon, N. platyrhynchus and N. raneyi); and N. lep tocephalus.
The objective of the present phylogenetic study was to determine if a cladogram based on reproductive behavioral characters conformed to the Nocomis morphological taxonomic groupings proposed by Lachner and Jenkins (1971). METHODS
Pebble nests of Nocomis were studied in streams in Georgia, North Carolin a, Virginia and Wisconsin from 1986 to 1990. Specific collection sites are available from the authors. Total number of nests observed for nest construction and spawning, and for nest composition (in parentheses) were: N. biguttatus, 8 (8); N. leptocephalats, 18 (12); and N. micropogon, Ii (7).
A pebble sample ( 15 cm deep) was collected from each of the upstream, middle and downstream parts of nests with a 1-1 plastic beaker. Three substrate samples (each 5 cm deep) from the stream bed, collected with the 1-1 beaker, were taken at random as far as 25 rn from nests. Nest and substrate sanples were returned to the laboratory. Pebbles were air-dried and sifted through five custom-built wire sieves. Mesh sizes, restricted to com mercially available prefabricated screen sizes, were 23.0 mm, 11.3 mm, 6.0 mm, 2.5 mm and 0.8 mm. The weight of material in each sieve or bottom pan was used to calculate the percentage of material per mesh size. Hereafter, all references to percentage of mesh size classes are based on weights. Average values of percentage pebble composition of nests and stream bed, derived from a General Linear Model procedure (SAS, 1985) were compared among species with Dun can’s Multiple Range Test (alpha 0.05). Data for nests of Nocomis 1. leptacephalus and 103
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126(1) N. 1. interocularis were combined as physical characteristics of their nests did not vary significantly (Doyle et at., 1989). Descriptions of nest construction and reproductive behaviors a e based on field obser vations and colored photographs recorded above the surface of the water during dayl ight hours with 35 mm cameras and video/television camera s. If a particular activity was observed more than once at separate nests (in the same or different geographical locations) it was designated a behavioral character. A total of 100 video-recording hours of nest construction and reproductive behaviors were replayed repeatedly frame by frame, analyzed and compared with field notes and literature accounts to determ ine behavioral characters for out-group (Campostoma anomalum) and in-group taxa (N. biguttatus, N. leptocephalus and N. micr o pogon). Seven behavioral characters of adult tuberculate breeding males and females were iden tified and determined as primitive or derived by out-group comparison. Campostoma anom a turn was selected as the out-group because an adul t male uses its mouth to remove stones from a discrete area in a gravel riffle bed or in pebble nests of nest-builders (e.g., Nocomis sp. and Semotilus sp.) to form a pit for spawning. Phylogenetic relationships of fishes were determ ined by cladistic methodologies. The algorithm PAUP (Phylogenetic Analysis Using Parsimony) version 2.4.0 developed by Swofford (1985) was used to postulate hypotheses of phylogenetic interrelationships with the following options. All characters were assigned the same or equal weights. The behavioral activities of characters 1, 2 and 5 were temporally and spatially sequential and were ordere d according to sequence. No direction was given to charac ter state transformations for char acters 3, 4, 6 and 7 as they were not sequential. All multiple equally parsimonious trees were generated by global branch swapping. CHARACTER ANALYSIS
Character 1. Nest construction—Breeding male Campostoma anornalum use their mouth s to remove stones from a discrete area in a riffle to form a concavity that is subsequently used for spawning (character state A; Table 1). Nest construction, similar among the three Nocomis species, occurs in three stages: excavating a concavity, forming a platform and building a mound (character state B). A single tubercu late male Nocomis excavates a concavity ca. 0.5 m in diam by removing stones with its mouth . Excavated pebbles, deposited on the lateral margins of the concavity, form two crescents of pebbles creating a channel through the center (Fig. la). The platform is built in the concavity. It is constru cted of stones that the male picks up with his mouth from the lateral margins of the concavity and deposits in the center and downstream end of the depression. Closing the downs tream end of the concavity with pebbles, the male continues to fill its center and then begins to dam the upstream margin. When a low ridge of pebbles is formed on the upstream margin, the male deposits pebbles on the downstream two-thirds of the platform until the entire concavity is filled (Fig. Ib). The mound is built on the platform. With its mouth , a single male collects pebbles from areas as far as 25 m from the nest and deposits them on the platform. If undisturbed, a male may complete a nest within a single day. A finishe d nest is a circular mound of pebbles with a central trough at its crest that parallels the water current (Fig. I c). Character 2. Excavation of spawning trough/pit in mound nests. —Nocomis teptocephalus and N. biguttatus excavate one to several spawning pits on the upstream slope of a pebble nest (character state C). During the period of mound building, a male (N. biguttatus or N. leptocephalus) digs a spawning pit on the upstream slope of the mound by removing stones from a discrete area with his mouth after the channe l trough has been filled.
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126(1) TLE 1.—Character and character states for out-g (Nocomis biguuatus, N. leptocephoius and N. microp roup (Campostoma anornalum) and in-group taxa ogon). Character 1—Nest construction, A = absent, B = present; 2—Spawning pit/trough in nest, A = absent, B trough, C pit; 3—Troug h/pit fan ning, A = absent, B = present; 4—Spawning clasp, A absent, B = vigorous, C weak; covered with pebbles, A = absent, B = present; —Eggs 6—Cirde swim, A = absent, B = present; 5 pebble class size, A = none, B = 6.0 mm, C = 7—Nest 11.3 mm Taxon Character
2 3 4
A A A
5 6 7
C B C
A A A
C B C
B B B
B B B
B B C
A B C
Completed Nocomis micropogon nests have deep to shallow troughs on the upstream slope (character state B). Nocomis micropogon does not dig spawning pits but uses the original central trough for spawning. All three spec ies deposit pebbles directly behind the spawning trough or pit. Spawning pits excavated in riffles or nests of pebble nest-builders by Cam postoma anomalum males are not homolog ous to those of Nocomis species as they are not preceded by nest construction (character state A). Character 3. Trough/pit fanning.—Duri ng digging and spawning, “fanning” occurs as the male swims to the downstream edge of the trough (N. micropogon) or the pit (N. leptocephalus and N. biguttatus). Lowering his head, a male breeder aligns hims elf within the trough or positions himself over the pit. As he continues forward, the male lifts his head forcing his vibrating anal fin into the grav el (character state B). This behavior is absent in C. anomalum (character state A). Character 4. Spawning.—Spawning in Nocom is leptocephalus, like that in N. bigu ttatus, occurs when a female enters a spawning pit. She aligns herself under or on the side of a male with the ventral side of her head again st the dorsal side of his pectoral fin. The male quivers his caudal fin toward the female, place s his caudal peduncle over that of the female, and forces her head up and her tail down. This action results in a vigorous spawning clasp where the female may be thrown into a verti cal position. The clasp lasts about a second, after which a female with mouth agape, still in the vertical position, drifts dow nstream (character state C; Fig. 2). Spawning in Nocomis micropogon is not as vigorous as that in N. leptocephalus and N. biguttatus. A female enters the trough where the male presses her against the troug h side. He then puts his caudal peduncle over hers with her head lodged between his oper cie and pectoral fin. The result is a comparativel y weak clasp as a relatively relaxed fema le is not thrown vertically into the water column (cha racter state B). Sometimes a female is clasped simultaneously by two males in the trough, one on each side of her body. Campostoma anomalum males do not clasp females but align themselves alongside a female during gam ete release (character state A). Character 5. Eggs covered with pebbles. —After a period of spawning with several fema les in one pit, a male Nocomis biguttatus or N. lepto cephalus collects pebbles usually from the
MAURAKIS ET AL.:
FIG. 2.—Spawning clasp of male
IVocomis leptocephalus. Note open mouth of female
mound and deposits them on the spawning pit (charac ter state B). Then the male moves either to the side or upstream of the original pit and digs another pit in the nest where he spawns again. Adult breeding male Nocoinis micropogon, like Carnpo stoma anamalum, do not cover eggs with pebbles (character state A). As spawning proceeds, a male N. micropogon continues to reshape the trough by removing stones that have fallen into it from the activity of fish. Character 6. Agonistic combat between males.—One form of combat is a combination of head butting and side-to-side swims. This is observed in Campo stoma anomalum. Two males aligned parallel, butt heads one or more times, and either lock cephalic tubercies or press their heads together as they swim upstream (character state A). In the Nocomis species this activity often is interrupted by circle swims (character state B). In this form of agonistic behavior, a nesting male and an equal-sized challenging male perform circle swims over a nest (Fig. 3). The males swim head to tail in a circle and whorl
AMERICAN MIDLAND NATURALIST
FIG. 3.—Circle swim in adult male
Nocomis leptocephalus, an agonistic behavior in Nocomis species
over a nest for as long as 10 sec. Circle swims usually occur when a spawning male Nocomis invades a nest. Character 7. Nest pebble size selection.—There were no significant differences in mean percentages for the 11.3-mm pebble size class (the highest percentage of pebble size classes) among the three species. Average percentage of the 6.0-mm size class for nests of Nocomis biguttatus was significantly greater than that in nests of the other two species (character state B). Nests of N. leptocephalus and N. rnicropogorz had significantly greater percentages of the 23.0-mm size class than those of N. biguttatus (character state C). Campostorna anomalum does not select stones for nests but does select areas of stream bed to dig spawning pits (character state A). PHYLOGENETIC ANALYSIS Phylogenetic analysis resulted in a single cladogram (10 evolutionary steps; consistency index, 1.00) (Fig. 4). Clade I represents the genus Nocomis and is defined by three synapomorphies (character state IB, three-stage process of nest construction; character state 3B, pit fanning; and character state 6B, circle swim). Clade II is a monophyletic group composed of Nocomis biguttatus and N. leptocephalus. The dade is characterized by two synapomorphies (character state 2C, excavation of spawn ing pits; and character state 5B, covering eggs in pits with pebbles). Clade III represents Nocomis micropogon and is defined by a single character (character state 4B, weak spawning clasp).
MAuLAx1s ET AL.: NOCOMIS REPRODUCTION
I (lB. 3B, 6B) FIG. 4.—Cladogram of relationships of Nocomis biguttatus, Nocomis leptocephalus and Nocomis mi cr3pogon based on reproductive behavioral characters (out-group = Campostoma anomalum, evolutionary steps = 10, consistency index = 1.0)
Clade IV (Nocomis biguttatus) is defined by one apomorphy (character state 7B, selection of 6.0-mm pebble size class for nest construction). DIscussioN Videotaping enhances the power of observation as tape recordings provid e an opportunity for repeated reviews of behavioral events. For example, prior to the use of video (Maurakis and Woolcott, 1989), not a single author reported the agonistic behavi or, circle swim, a conspicuous activity in Nocomis species. Our identification of three behavioral synapomorphies (Clade I) based on reproductive activities of adult, tuberculate males supports the monophyly of genus Nocomis proposed by
Lachner and Jenkins (1971). The three-stage process of nest construction, circle swims and trough/pit fanning occur only in Nocomis. None of these behavioral patterns have been reported in literature accounts nor recorded for other pebble nest-building cyprinid genera Exoglossum (Maurakis et at., 1991) and Semotilus (Maurakis et at., 1990) or pit-digging Campostoma species (Miller, 1962). Based on tuberculation, morphology and color of breeding males, Lachne r and Jenkins (1971) stated that the biguttatus group is more closely related to the micrap ogon group than to Nocomis teptocephalus. In contrast, our results indicate that N. leptoce phalus and N. biguttatus form a monophyletic group (Clade II) based on two synapomorph ies, spawning pit excavation and covering eggs with pebbles after spawning. Nocomis biguttatus, the smallest species within the genus (Lachner and Jenkins, 1971), is different from N. Leptocephalus and N. micropogon in that it selects a greater proportion of smaller stones (6 mm) in nests, probably a function of mouth positio n and fish size. The mouth in N. biguttatus is oblique, opening terminally (Lachner and Jenkin s, 1971) and acts as a proficient scoop. in scraping the substrate and moving smaller stones. Mouths of N. leptocephalus and N. micropogon are inferior and horizontal (Lachn er and Jenkins, 1971),
more suited for digging and lifting larger stones from the substrate.
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Our use of the term concavity (=saucer-shaped excavation or pit, Reighard, 1943) refers to the cleared depression in the substrate that is made prior to the platform. Our “pit” or “spawning pit” is synonymous to “spawning trough” of Reighard (1943). Reighard (1943) recognized two stages in Nocomis nest construction: “pit digging” and “mound building.” We favor the three-stage process described by Lachner (pers. comm.) because the majority of stones of the platform come from the lateral margins of the concavity. In all three species, stones for the mound are collected primarily from the adjacent streambed away from the nest as described by Vives (1990) for N. biguttatus. Our observations of the spawning clasp in populations of Nocomis micropogon in Virginia and North Carolina agree with that reported by Reighard (1943) for this species in Michigan. This is the first report to describe the spawning clasp in N. leptocephalus and concurs with that reported by Vives (1990) for N. biguttatus. Acknowledgments. —We dedicate this study to Ernest A. Lachner, a friend and longtime student of Nocomis species investigations. Thanks are due Sharon A. Doyle for assistance in the field and laboratory and Wilton R. Tenney for photography. Funding was in part by University of Richmond Faculty Research Grants and research awards from Highlands Biological Station, North Carolina. LITERATURE CITED
1989. Pebble nest microhabitats of two 36:93. Bull., Riot. Southeast. Nocomis spp. Assoc. LACHNER, E. A. 1946. Studies of the biology of the chubs (genus Nocomis, family Cyprinidae) of northeastern United States. Cornell 1mm. Abstr. Theses:207—210. of the chub genus Nocomis AND R. E. JENKINS. 1971. Systematics, distribution, and evolution of new species. Smith descriptions with States, United eastern of Cyprinidae) Girard (Pisces,
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journal MAuIt.kIcIs, E. G. AND W. S. WooLcorr. 1989. Were they accurate? Comparisons between accounts and video recordings of reproductive behaviors of selected cyprinids. Assoc. Southeast. Biol. Bull., 36:65. W. S. WOOLCO’IT irn J. T. MAGEE. 1990. Pebble-nests of four Semotilus species. Proc. Southeast. Fish. Council, 22:7—13. AND M. H. SABAJ. 1991. Reproductive behavior of Exoglossurn species. Bull. Ala. Hist., 10:11—16. Nat. Mus. Campostoma anomalumpullum. MILLER, R. J. 1962. Reproductive behavior of the stoneroller minnow, 17. 1962:407—4 Copeia, micropogon (Cope). Pap. Mich. REIGHARD, J. 1943. The breeding habits of the river chub, Nocomis . 24:397—423 Lett., Arts Sci. Acad. Inc. Cary, North SAS INsTrrum, INC. 1985. SAS user’s guide: statistics, version 5. SAS Inst.,
Carolina. 956 p. D. L. 1985. Phylogenetic analysis using parsimony, version 2.4. Nat. Hist. Surv., Champaign, Illinois. S. P. 1990. Nesting ecology and behavior of hornyhead chub Nocomis biguttatus, a keystone species in Allequash Creek, Wisconsin. Am. MidI. Nat., 124:46—56.
SUBITrED 17 AUGUST 1990
ACCEPTED 5 APRIL 1991