Environmentl Biology of Fishes 44: 7-6,1995. 1995 Kluwer Acdemic Publishers. Printed in the etherlnds. Ecomorphologicl correltes in ten species of subtropicl segrss fishes : diet nd microhbitt utiliztion Philip J. Mott', Kri B. Clifton', Ptrici Hernndez' & Brdley T. Eggold 'Deprtment of Biology, University of South Florid, Tmp, FL 6, U.S.A. Wisconsin Deprtment of turl Resources, PO. Box 48, Plymouth, WI 5 7, U.S.A. Received 1.1.199 Accepted.11.1994 Key words: Tmp By, Morphology, Feeding, Phylogeny, Convergence, Speciliztion Synopsis Ecomorphologicl correltes were sought mong ten species of distntly relted subtropicl segrss fishes. Morphomet ric dt ssocited with feeding nd microhbitt utiliztion were compred by principl components nlysis, cluster nlysis, nd cnonicl correspondence nlysis to dietry dt. Morphology ws generlly poor predictor of diet except for group of mid-wter plnktotrophic filter feeders. Seprtion of the species long morphologicl xes ppers to be relted more to microhbitt utiliztion resulting in three mjor groups: (1) group of plnktotrophic, mid-wter fishes specilized for cruising nd seeking out evsive prey chrcterized by compressed fusiform body, forked cudl fin, long, closely spced gill rkers, short to intermedite length pectorl fin, pointed pectorl fin, lrge lterl eye, short hed, nd terminl or subterminl mouth ; ( ) slow swimming, less mneuverble epibenthic fishes tht pick or suck their prey off the substrte. They re united by more rounded cudl nd pectorl fins, nd short or no gill rkers ; nd ( ) group of more mobile nd mneuverble epibenthic forgers chrcterized by more compressed, sub-gibbose body, long, pointed pectorl fins, forked cudl fins, lrge lterl eyes, subterminl mouth, nd greter jw protrusibility. Cses of convergence in trophic nd microhbitt utiliztion chrcters were pprent in some of the groups. Introduction Ecologicl morphology hs s its mjor premise tht the ecology of n orgnism is relted to its morphology. Wheres functionl morphology is the study of form nd function, ecologicl morphology overlps functionl morphology nd emphsizes form in reltion to biologicl role(s). Although there is no consensus on the definition of ecomorphology, it my be defined s the study of the reltionship between environmentl fctors, both physicl nd biotic, nd form, such s to isolte the mutul contribution of one to the other (Mott & Kotrsch1199 ). One of the purported dvntges of ecologicl morphology is its predictive power (Krr & Jmes 1975, Miles & Ricklefs 1984, Grossmn 1986, Dougls 1987). Given tht environments constrin morphology nd ecology in prllel fshion, we should be ble to predict ecologicl ptterns of individuls, popultions, or species ssemblges from their morphologicl chrcteristics (Wiens & Rotenberry 198). Although there is no definitive protocol, ecomorphologicl studies generlly seek ptterns in
8 the ecology or behvior of n orgnism or group of orgnisms nd try to relte them to ptterns in form. In the initil step of such nlyses, correltions re usully sought between morphologicl nd ecologicl vribles (e.g. Moyle & Sennyke 1984, Wikrmnyke 199, this study). This pproch provides predictbility, but no cusl explntion. It leves the investigtor with uncertinty s to performnce, optimlity, nd the constrints on the `fit' between form nd biologicl role (Mott & Kotrschl 199 ). In the second step of the investigtion, one not usully reched in mny studies, the predictions re tested through experimenttion or modeling in the lbortory to determine the potentil niche, nd secondly the effect of performnce on ctul ptterns of resource use my be determined through field studies (i.e. the relized niche) (Winwright 1987, 1991). An ontogenetic nlysis of the ecomorphologicl reltionship my be performed t this stge (Glis 199 ). In the third step, comprtive phylogenetic nlyses re undertken. Two different comprisons, with different ims, hve been pplied. Most investigtors dvocte compring the vrition of structure nd its use within closely relted tx, usully cogener or cofmilils (Leisler 198, Ymok 198, Felley 1984, Leisler & Winkler 1985, Ymok, Hori & Kurtni 1986, Pounds 1988, Winwright 1988, Kotrschl 1989, orton 1991) ; these my include comprison with more distntly relted outgroup (Mott 1988, Losos 199). It is ssumed tht choosing closely relted species will reduce the risk tht coincidentl differences will msk significnt ptterns (Huey & Bennet 1986). Findley & Blck (198 ) explicitly believe, nd others implicitly ssume, tht ecomorphologicl reltionships my be most detectble in closely relted species tht hve long history of evolution nd rdition in the sme region. This kind of comprtive pproch llows one to propose evolutionry scenrios nd hypotheses on the process of dpttion nd most redily revels prllel nd divergent evolution (Mott & Kotrschl 199 ). Convergence is difficult to study in smll, more closely relted groups. Becuse we usully hve more confidence in our phylogenetic groupings t broder txonomic scles, ecologicl (nd morphologicl) convergences cn be identified with greter ese (Winemiller et l. 1995). Therefore, nother pproch is the comprison of ecomorphologicl reltionships mong guilds of more distntly relted orgnisms (Krr & Jmes 1975, Ricklefs & Cox 1977, Gtz 1979, b, Ricklefs & Trvis 198, Wiens & Rotenberry 198, Miles & Ricklefs 1984, Moyle & Sennyke 1984, Wtson & Blon 1984, Dougls 1987, Miles et l. 1987, Wikrmnyke 199, Block et l. 1991, Wiens 1991, b, Winemiller 1991). This cn be powerful indictor of convergent evolution (e.g. Krr & Jmes 1975, Wiens 1991b). While there pper to be superficil ecomorphologicl correltions relted to feeding in fishes, for exmple, longer gill rkers re ssocited with plnktivory, shorter ones with crnivory ; longer guts with herbivory nd shorter ones with crnivory (e.g. Cho & Musick 1977, Goldschmid et l. 1984) ; s well s correltions between fin nd body shpe, nd locomotory bilities nd microhbitt utiliztion (Kest & Webb 1966, Webb 1984), there re few reltionships tht document ecomorphologicl ptterns in fishes beyond these. Gtz (1979, b) found extensive ecomorphologicl correltions bsed on feeding nd microhbitt seprtion ; orton's (1991) work supported the ecomorphologicl hypothesis tht dietry differences in cottids re in prt due to differences in reltive mouth size through the influence of mouth size on feeding performnce. Furthermore, there is strong reltionship between selected morphologicl ttributes nd microhbitt exploittion in tropicl strem fish ssemblge (Wikrmnyke 199). Winemiller (1991) lso identified ecomorphologicl divergences within higher tx of fishes from the sme region nd convergences between phylogeneticlly divergent tx from different regions. On the contrry, Kotrschl (1989) concluded tht orl jw morphology is not relible predictor of feeding ecology in 4 species of blennioid fishes. Similrly, Felley (1984) found tht priori morphologicl chrcter sets derived from previous studies of functionl morphology nd morphologiclenvironmentl ssocitions could not be used to predict hbitt use in cyprinids. An -posteriori set
9 reveled by fctor nlysis for subgroup of cyprinids ws more predictive. Becuse there is considerble mount of residul morphologicl vrition in mny communities tht cnnot be directly relted to ecologicl vribles, predictbility of morphologicl reltionships in one ssemblge from those in nother is reduced (Struss 1987). Furthermore, Grossmn (1986) believes tht behvior my be more importnt thn morphology in determining prey utiliztion in rocky intertidl fish ssemblge. Mott. (1988) found tht morphologicl structures ssocited with feeding in butterflyfishes re correlted with how the fishes feed (e.g. suction, scrping, biting), rther thn with wht they feed on. Mny of these studies tht seek correltions between morphology nd diet or microhbitt utiliztion do not utilize multivrite techniques of direct grdient nlysis, tht is, techniques tht sttisticlly compre combintions of environmentl nd morphologicl vribles simultneously. Consequently the interprettion of such studies cn be wekened if the comprison between the environmentl nd morphologicl vribles is subjective. This study is significnt in tht it : () employs suite of univrite nd multivrite techniques, including direct grdient nlysis of dietry nd morphologicl dt ; (b) seeks ecomorphologicl ptterns mong txonomiclly divergent group of fishes to investigte whether morphology is good predictor of diet ; nd (c) determines if cses of evolutionry convergence cn be identified in this feeding guild of segrss inhbiting fishes. Utilizing ten numericlly bundnt nd txonomiclly divergent species of fishes from subtropicl segrss hbitt, this study ddresses the following questions : (1) Is morphologicl similrity mong species reflective of dietry similrity? ( ) Do these species exhibit convergence in morphology? And, if so, ( ) does morphologicl convergence pper to be relted to feeding nd/or microhbitt utiliztion in this diverse fish ssemblge? Mterils nd methods Study site Fishes were collected from segrss hbitt in Boc Cieg By, ner the entrnce to Lower Tmp By, Florid ( 7 41', 8 41'W), from My to October, 1989 nd 199. The Tmp By system is lrge, shllow (< 4 m), subtropicl estury lined by limited mngrove forests nd slt mrshes. Tmp By is pproximtely 56 km long, 16 km wide t the mouth, with 41 km of shoreline. Five mjor rivers dischrge into Tmp By (Comp & Semn 1985). This nitrogen nd phosphorus enriched estury supports sesonlly high phytoplnkton biomss nd productivity. Segrss beds, mcrolge, nd benthic microflor lso contribute to the totl primry production of this system (Johnsson et l. 1985). Our study site is gently-sloping sndy bech leding to shllow (.5 to. m) Thlssi testudinum dominted segrss bed with intervening sndy ptches. Dense mts of mcrolge dominted by Grcilri nd Hypne spp, were often present. Mximum tidl fluctutions resulted in 94 cm chnge of depth, lthough collections were not mde t very low tides. Collection nd dt nlysis Thirty individuls ech of ten species found in or bove the segrss beds, including the wter column were exmined in this study (stndrd length rnges of the specimens used indicted) : Chilomycterus schoepfi (striped burrfish, 1 6-15 mm), Floridichthys crpio (goldspotted killifish, 51-79 mm), Lgodon rhomboides (pinfish, 1-154 mm), Eucinostomus gul (silver jenny, 71-114 mm), Fundulus similis (longnose killifish, 7-11 mm), Hrengul jgun (scled srdine, 84-14 mm), Syngnthus scovelli (gulf pipefish, 91-164 mm), Ancho hepsetus (striped nchovy, 9-18 mm), Menidi peninsule (tidewter silverside, 54-8 mm), nd Arius felis (hrdhed ctfish, 8-91 mm) (Fig. 1). In ll cses only sexully mture individuls were smpled. These species were used becuse they consti-
4 A. hepsetue C. choepfi M. pen Ins u I e F. crplo F. simills S. scovoil I 14 le Fig. 1. Profiles of ten species of Tmp By segrss fishes investigted. Br indictes 1 cm. tute some of the most numericlly bundnt fishes in Florid nd Tmp By segrss hbitts (Springer & Woodburn 196, Livingston 1976, Brook 1977, Livingston 198, Stoner 198, Comp 1985, Thyer et l. 1987). Collections were mde in nd bove the segrss beds with.95 cm (squre mesure) bech seine,.5 cm,.75 cm, nd 5. cm (squre mesure) monofilment gill nets, nd m otter trwl with. cm mesh cod end pulled by power bot. Fishes were dissected immeditely fter cpture nd the entire gut removed nd preserved in 1% buffered formlin with Rose Bengl. Fishes were frozen for subsequent morphologicl nlysis. A detiled description of dietry nlysis is reported in Mott et l. (1995). In brief, for species with distinct stomch, only prey items in the stomch were included. For species without distinct stomch the nterior
41 SL TL f P p C BD BW Fig.. A representtive species, Eucinostomus gul, with ten mensurl nd five coded morphometric vribles indicted. S L = stndrd length, HL = hed length, BD = body depth, B W = body width, PL = pectorl fin length, MW = mouth width, ED = eye dimeter, RL = gill rker length, RS = gill rker spcing, HLP = hed length with jw protruded, CS = cudl fin shpe, PS = pectorl fin shpe, EP = eye position, MP = position of open mouth, DT = dentition type. 1/ of the intestine ws evcuted. Specimens with empty stomchs or nterior intestines were not utilized. Prey were identified under dissecting microscope to order in most cses, nd n Index of Reltive Importnce (IRI) (Pinks et l. 1971), bsed on wet weight, frequency of occurrence, nd numbers, clculted for ech prey tx. Hill's (197 ) diversity numbers were clculted : O, the number of prey tx ; 1, the number of bundnt prey tx ;, the number of very bundnt prey tx ; nd E5, evenness. IRI vlues were used to cluster the species using the Bry..Curtis percent dissimilrity index, nd Horn's index. of overlp indicted the dietry overlp mong the species. In our nlysis 15 morphologicl chrcters were represented by either mensurl or coded vribles. Ten mensurl vribles reflecting feeding nd hbitt use (Gt 1979) were tken on ech specimen : stndrd length SL (tip of closed mouth to end of lst vertebr), hed length HL (nterior tip of closed mouth to posterior edge of opercle), hed length protruded HLP (nterior tip of protruded jw to posterior edge of opercle), body depth BD (depth t widest prt of body), body width BW (width t thickest prt of body), pectorl fin length PL (bse of fin to tip of longest ry), mouth width MW (t widest prt with mouth fully open), eye dimeter ED (dimeter between fleshy orbits long n nterior-posterior xis), gill rker length RL (longest rker on first gill rch), gill rker spcing RS (distnce between rkers on first gill rch in the vicinity of the certobrnchil-epibrnchil border). In ddition, five coded vribles were scored with integer vlues for ech species : cudl fin shpe CS (rounded =1, truncte =, emrginte =, lunte = 4, or forked = 5), pectorl fin shpe PS (rounded = 1, intermedite =, or pointed = ), eye position EP (lterl =1, slightly dorso-lterl =, or dorsl = ), open mouth position MP (suprterminl =1, terminl =, subterminl =, inferior = 4, or ventrl = 5),
4 nd dentition type DT (crdiform =1, villiform =, cnine =, incisor = 4, reduced incisiform = 5, brush-like = 6, molriform = 7, fused = 8, tricuspid = 9, or no teeth =1) (Fig. ). Mensurl vribles were mesured with ruler or vernier clipers to the nerest.1 mm. Gill rker length nd spcing were mesured to the nerest.1 mm with n oculr micrometer fitted for dissecting microscope. Principl components nlysis,(pca) ws used to identify ptterns in morphologicl vrition mong species. PCA is method of breking down or prtitioning resemblnce mtrix into set of orthogonl (perpendiculr) xes or components. Ech PCA xis corresponds to n eigenvlue of the mtrix. The eigenvlue is the vrince ccounted for by tht xis. The first few PCA xes represent the lrgest percentge of the totl vrition tht cn be explined (Ludwig & Reynolds 1988). PCA ws conducted on correltion mtrix. All continuous vribles were log o trnsformed in order to more closely pproximte norml distribution nd reduce heteroscedsticity. Two nlyses were performed to explore the reltive merits of mixing mensurl nd scored vribles: (1) PCA of the mensurl nd coded vribles together, nd ( ) one with only the mensurl vribles. The PCA nlyses were performed on SAS using the Princomp procedure. To id in dt nlysis, three dimensionl plots were constructed using the G D procedure. The mensurl vribles tht loded hevily on PCA xes nd, tht is, those tht ccount for the gretest vrince in the dt set, hed length, hed length protruded, body depth, mouth width, pectorl length, eye dimeter, gill rker spcing nd gill rker length, were log o nd lterntely squre root trnsformed nd found not to be normlly distributed in either cse. Therefore, n -priori Kruskl- Wllis test ws performed on the untrnsformed dt ( = ) to detect significnt differences mong species. Ech vrible ws found to differ significntly mong species, therefore -posteriori Mnn- Whitney U tests were crried out for ll possible pirwise combintions ( = 45) of species. The Bonferonni technique ws used to determine the significnce level for the Mnn-Whitney U tests (Gtz 1979). An lph level of =.5/45 =.1 ws used for ech pirwise comprison. For ech vrible, species tht were not significntly different were joined by line. To ssess the degree of jw protrusion reltive to hed length the following vrible ws clculted for ech species ((HLP-HL/ SL)X1) ( = ). Cluster nlysis ws performed on ll fifteen untrnsformed morphologicl vribles nd on the dietry dt of Mott et l. (1995) using the Bry- Curtis percent dissimilrity index with the flexible strtegy (( = -. 5) to crete three clusters (Ludwig & Reynolds 1988). The first cluster ws constructed with ll morphologicl vribles. In order to investigte the reltive proportions of the morphologicl ttributes, for exmple, the size of the pectorl fin reltive to the size of the fish, second cluster ws generted with the mensurl vribles expressed s percentge of stndrd length. Men vlues were used for the ten mensurl vribles. In both nlyses, the five coded vribles were entered s integer vlues. The third cluster ws on the IRI dietry vlues for nine species (excluding M. peninsule for which dt were not vilble) from Mott et l. (1995). Clusters were constructed with the Sttisticl Ecology pckge (CLUSTER progrm) of Ludwig & Reynolds (1988). While we utilized rtios for explortory dt nlysis in one cluster nlysis, we specificlly voided rtios in the sttisticl nlyses due to their inherent limittions (Atchley et l. 1976, Reist 1985, Jckson et l. 199, Jckson & Somers 1991). Cnonicl correspondence nlysis (CCA) nd detrended cnonicl correspondence nlysis (DCCA by second order polynomils) were performed on two sets of morphologicl nd dietry dt for nine species. Menidi peninsule ws excluded from this nlysis becuse the only dietry dt vilble ws qulittive dt from the literture. Cnonicl correspondence nlysis is multivrite technique of direct grdient nlysis tht selects the liner combintion of environmentl vribles (diet) tht mximizes the dispersion of the species (morphology) scores. It chooses the best weights for the environmentl vribles to construct the first CCA xis. The second nd further CCA xes lso select liner combintions of environmentl vribles tht mximize the dispersion of the species scores, but subject to the constrint of
4 being uncorrelted with previous CCA xes. Environmentl vribles my be quntittive or nominl (Jongmn et l. 1987, ter Brk 1986,1987). Detrended CCA is n efficient ordintion technique when species hve bell-shped response curves with respect to environmentl grdients (ter Brk 1986). We performed CCA nd DCCA utilizing the progrm CAOCO version.1 (ter Brk 1988). In the first dt set, species dt consisted of the 15 mensurl nd coded morphometric vribles. To reduce collirierity due to too mny environmentl vribles, only IRI vlues for eighteen very bundnt dietry tx, s indicted by Hill's, were utilized in the nlysis. In the second comprison, species dt consisted only of the morphometric vribles tht were considered relted to microhbitt utiliztion (body depth, body width, pectorl fin length, eye dimeter, cudl fin shpe, pectorl fin shpe, eye position) nd not to feeding per se. As before, the environmentl vribles comprised the IRI vlues for the eighteen very bundnt prey tx. Results Principl components nlysis-mensurl vribles only The first two principl components hd eigenvlues greter thn one nd ccounted for 88% of the cumultive vrince. Principl component 1 ccounted for 75 % of the vrince, PC ccounted for 1 %, nd PC ccounted for 7% (Tble 1, Fig. ). The eigenvlues of the first principl component were positive nd pproximtely equl in mgnitude indicting strong size vector (Struss 1987). With incresing mgnitude long principl component xis, the species hd longer, more closely spced gill rkers, longer pectorl fins, shorter heds, nd lrger eyes. Principl component seprted fishes by decresing spcing of the gill rkers, lrger mouths, shorter pectorl fins, nd decresing body depth (Tble 1, Fig. ). The following species grouped close in morphospce : Menidi peninsule, A. hepsetus, nd H. jgun formed single group ; F crpio nd F similis formed group ; Eucinostomus gul ws positioned between F similis nd L. rhomboides ; Chilomycterus schoepfi, A. felis, nd S. scovelli were seprted in morphospce (Fig. ). Tble 1. Principl components nlysis for morphometric dt on ten species of segrss fishes ( = ). Eigenvlues for the first three principl components on mensurl vribles only. Eigenvlue Difference Proportion Cumultive Prinl 7.568 6. 89.7568.757 Prin 1. 7176.585.1 7176.877 4 Prin.68656.47717.68656.9459 Prinl Prin Prin SL. 78 41 -. 97784.54177 HL. 488 4 -. 145.161558 BD. 71.1 795 -. 9964 B W. 46761 -.119 64 -, 1746 PL. 1686. 6794 -. 74 8 MW. 5778.164498. 77 56 ED. 68 9.196 4. 55 PL.189695.7 174.16 76 RS. 7755 -. 99686 -.58877 HLP. 5 687 -.19679.7 54 SL = stndrd length, HL = hed length, BD = body depth, B W = body width, PL = pectorl fin length, MW = mouth width, ED = eye dimeter, RL = gill rker length, RS = gill rker spcing, HLP = hed length with jw protruded.
4~-, 4~&
4 5 Fig.. Principl components nlysis of the ten mensurl morphometric vribles for ten species of segrss fishes ( = ). The vribles with lrger eigenvlues (Tble 1) indicted on ech xis. Club = A. felis, Dimond = C. schoepfi, Str = L. rhomboides, Cross = F similis, Spde = S. scovelli, Hert = E. gul, Circle = A. hepsetus, Tringle = H. jgun, Squre = M. peninsule, Cube = F crpio, BD = body depth, PL = pectorl fin length, MW = mouth width, ED = eye dimeter, RL = gill rker length, RS = gill rker spcing, HL = hed length, HLP = hed length with jw protruded. Principl components nlysis-mensurl nd coded forked cudl fins nd pointed pectorl fins t the vribles combined other extreme, for exmple L. rhomboides. Mouth position ws suprterminl in S scovelli nd gener- The first three principl components hd eigenv- lly subterminl t the other extreme (Tble, Fig. lues greter thn one nd ccount for 87% of the 4). cumultive vrince. Principl component 1 c- Fishes with more rounded cudl nd pectorl counted for `i5 % of the vrince, PC for % nd fins, eye more dorsolterl, shorter gill rkers, more PC for 1% (Tble ). Mensurl vribles on prin- suprterminl mouth, loss of dentition, nd increscipl component 1 were positive nd pproximtely ing hed length scored high on PC. Along princiequl in mgnitude indicting strong size vector, pl component xis there ws shift towrds more This ws not generlly the cse for the coded vri- dorsolterl eye position, more pointed pectorl bles. Dentition type ws strong nd negtive indi- fins, nd forked cudl fins (Tble, Fig. 4). cting the shift from villiform teeth, towrds tricus- Principl components nlysis bsed on compid teeth (F crpio) nd loss of dentition (S. scovel- bined mensurl nd coded vribles resulted in li) on PC xis 1. Cudl fin shpe nd pectorl fin ech species occupying less morphospce with genshpe indicted grdient from more rounded fins erlly less overlp mong species. Menidi penin- (for exmple S. scovelli) t one extreme to more sule, H. jgun, nd A. hepsetus formed tight Tble. Principl components nlysis for morphometric dt on ten species of segrss fishes ( = ). Eigenvlues for the first three principl components on mensurl nd coded vribles. Eigenvlue Difference Proportion Cumultive Prin 18. 4 84 4.9664.5495.5495 Print. 7644 1.7818. 184 9.76795 Prin 1.49461.65661.99641.86759 Prinl Print Prin SL. 8 4. 8558. 18499 HL. 144 7. 497.54975 BD. 115 -.16 9 -.14411 B W. 1189.1866 -.14 9 PL. 446 -.9 8 -.15 MW. 75 6.5684. 4845 ED. 98.475 -,1466 RL. 1 46 -. 5574.118 GS. 54 57.16 1 4 -. 66 6 HLP. 19984. 6 5.16996 CS.14156 -.41 796.4 95 PS.15 785 -. 58958.4 81 EP.67 1. 5665.5 191 MP.161817 -. 7176 -. 95 DT -. 554. 51 4. 519 SL = stndrd length, HL = hed length, BD = body depth, B W = body width, PL = pectorl fin length, MW = mouth width, ED = eye dimeter, RL = gill rker length, RS = gill rker spcing, HLP = hed length with jw protruded, CS = cudl fin shpe, PS = pectorl fin shpe, EP = eye position, MP = position of open mouth, DT = dentition type.
1.41 A(, ( e G O ( ~ PRI 6e b. Q e (o.1 t -.77 d 6 1 1 `~.59 V 9) 9 r. b `6 %. %,~. O d e J fr j.y >z PR I1 -.. 6 d O e e O u s e ($ o f,~e 6 %\% ~` ~~~ O p und ed,d t eethubter mip~ -6.8 ' x5 term hd mo p e C t1 f te e th e~ \ $$ n ( uth th e_ r `P
47 Fig. 4. Principl components nlysis of the ten mensurl nd five coded morphometric vribles combined for ten species of segrss fishes ( = ). The vribles with lrger eigenvlues (Tble ) indicted on ech xis. Club = A. felis, Dimond = C. schoepfi, Str = L. rhomboides, Cross = F similis, Spde = S. scovelli, Hert = E. gul, Circle = A. hepsetus, Tringle = H. jgun, Squre = M. peninsule, Cube = F crpio, RL = gill rker length, RS = gill rker spcing, HL = hed length, HLP = hed length with jw protruded. group, with E. gul nd L. rhomboides clustering nerby. Floridichthys crpio nd F similis were grouped very close together in morphospce with C. schoepfi nerby. Arius felis nd S. scovelli were ech morphologiclly distinct nd seprted from the other species (Fig. 4). rhomboides nd F crpio protruded their jw.7% of their stndrd length ; E. gul.5%, nd M. peninsule. %. Chilomycterus schoepfi (1.5%) nd F similis (. %) hd slight protrusibility. Morphometric clustering Mensurl morphometric vribles-univrite sttistics Principl components nlysis of the morphometric vribles resulted in few species groups nd some species seprted in morphospce. Univrite nlysis of the morphometric vribles tht loded hevily on either PCA or combined with the coded vribles resulted in the following chrcter complexes : (1) group including H. jgun, A. hepsetus nd M. peninsule chrcterized by compressed fusiform body with forked cudl fin, long, closely spced gill rkers, short to intermedite length pectorl fin, pointed pectorl fin, reltively lrge (A. hepsetus nd H. jgun) lterl eye, short hed, nd terminl or subterminl mouth ; ( ) Fundulus similis nd F crpio which both hd rounded cudl nd pectorl fins, short pectorl fins, smll body size, smll, lterl eyes, subterminl mouth, short gill rkers, nd smll mouth width nd body depth. These species shred few chrcters with C. schoepfi nd S. scovelli: rounded cudl nd pectorl fins, nd short or no (C. schoepfi) gill rkers ; nd ( ) Lgodon rhomboides nd E. gul united by their sub-gibbose body shpe (including lrge body depth), forked cudl fins, long, pointed pectorl fins, lrge, lterl eyes, nd subterminl mouth. Arius felis ws n outlier in morphospce, chrcterized by being lrge bodied with forked cudl fin, long, pointed pectorl fin, slightly dorsolterl eye, subterminl, wide mouth, long, nd widely spced gill rkers (Fig. 5). Of the species tht protrude the upper jw, L. Cluster nlysis of the fifteen, untrnsformed morphometric vribles (excluding stndrd length) resulted in three groups nd one outlier species. Eucinostomus gul, H. jgun, F similis, nd A. hepsetus formed the first group, clustering t the.11 level. Fundulus crpio nd M. peninsule formed second group t the.1 level, nd A. felis, C. schoepfi, nd L. rhomboides formed third group t the. 4 level. Syngnthus scovelli, the outlier species, ws joined to the first two groups t the. 9 level (Fig. 6). Cluster nlysis of the proportionl mesurements (mensurl morphometric vribles expressed s percent stndrd length), nd the coded vribles together resulted in different rrngement of three groups nd one outlier species. Lgodon rhomboides, E. gul nd F crpio formed group t the.1 level ; F similis nd C. schoepfi formed second group t the.1 level ; nd H. jgun, M. peninsule, A. hepsetus, nd A. felis formed third group t the.14 level. Syngnthus scovelli ws the outlier species joined to ll three groups t the.86 level (Fig. 7). Dietry overlp nd cluster nlysis Dietry overlp dt (Tble ) (Mott et l. 1995) nd cluster nlysis of the IRI dt (Fig. 8) reveled similr species grouping. The nine species on which dietry dt were collected seprted into three groups : one with reltively high overlp comprised of F crpio, H. jgun, nd A. hepsetus ; second
4 8 1 E 1 E E E 8 8 ) v s 6 6 cc t 4 Q 4 C ) S ) I. o ) > E rn w.> 7 O ' d ~ -O W E.~ C v CL d J :Z - O 7 c ' o, (V > U U) C O 7 6 E 5 d t 4 -o T ( :r o U) O o 'E V) CL Q u o E L O U Q : I J o o, - U) o U L C E 1 1 4 I I I 1 1 1 i.z Q) ) C. ~_ O I!! :P O o, o L E 7 >. o t m E U W O L c O F_ i U I ' Fig. 5. Hed length, hed length protruded, mouth width, body depth, pectorl fin length, gill rker length, gill rker spcing, nd eye dimeter of ten species of segrss fishes. Men ± one stndrd devition indicted. Species tht re not significntly different indicted ( =, Mnn-Whitney U-test, p =.5). group with intermedite overlp levels includes C. schoepfi, F similis, nd E. gul. A third group including A. felis, S scovelli, nd L. rhomboides hd reltively little dietry overlp. Dietry-morphometric correspondence Cnonicl correspondence nlysis (CCA) nd detrended CCA (DCCA) of the 15 morphologicl vribles nd dietry dt indicted tht the morphologicl vribles were poorly relted to the first four environmentl (dietry) xes (eigenvlue =. on Axis 1, Tble 4). Only % of the morph- ologicl vrince could be ccounted for by dietry xis 1. Anlysis of the seven morphologicl vribles relted to microhbitt utiliztion reveled similrly poor reltionship (eigenvlue =.55 on Axis 1, Tble 4). Eigenvlues of pproximtely. nd higher re quite common in ecologicl pplictions (ter Brk 1988, Jongmn et l. 1987), nd ordintion xes with very low eigenvlues (<. ) should be discrded (ter Brk 1988). Becuse of the poor reltionship between morphologicl nd dietry xes in this study, further nlysis of the xes ws not wrrnted.
I I 4 9 _ 6c E E 5 e E 4 E 4 C U U) 1 U) 4- _O O U).= U) U J O p O ~ E > > D O U w ~. U) c O E _ J li l U L v s ' c v W I I I I O U) 5 _ C C O ton O O O Q v t -O C W U O LU L< f Li _.5 E. ) cu 1.5 Q_ In 1. 5. 4 f 1 I I 1 I I. I I I U) ) v- v~ CO O U) O 7.~ W - U C v i p L L E i J 75 g 16 Li I U) I LU S 7 h Fig. 5. Continued. Discussion Principl components nlyses of the morphometric dt indicted tht the species seprted by vriety of chrcters ssocited with feeding nd microhbitt utiliztion. In generl, the first principl component ws indictive of overll body size. Body size in these fishes is believed to be n importnt fctor in niche seprtion (discussed below). Thus, body size is not lwys nuisnce fctor tht must somehow be removed from dt before `true' systemtic or ecologicl reltionships cn be determined (Dougls 1987) ; it my be n importnt fctor influencing species resource utiliztion. When coded vribles were considered, vribles indictive of trophic (dentition type) nd microhbitt (cudl nd pectorl fin shpe) differentition loded hevily. The second nd third principl components were linked by trophic nd microhbitt use, being strongly influenced by gill rker length nd spcing, cudl nd pectorl fin shpe, pectorl fin length, hed length nd hed length protruded, eye dimeter nd position, mouth width nd position, body depth, nd dentition type. Principl components nlysis of the ten species ws gretly ffected by the mixing of mensurl nd coded vribles. The nlysis of ll 15 vribles.resulted in the species groups clustering tighter in morphospce nd seprting more from other species groups. Our nlysis does not llow us to recommend one prticulr pproch over nother, becuse two fctors differ between the pproches. In
5 o.o Morphologicl vribles Morphologicl vribles.8. Percent stndrd length.7.8.e.7.5..4.5..4...1.. ` y ; rn > -n x m > n r.1 I e O 7 -~ V V O C m C w 7 f C w V CL.- r -' m O. C ID - V. w w CA) 7 w T ld V C, m ( V O < Fig. 6. Cluster nlysis of fifteen untrnsformed morphometric vribles for ten species of segrss fishes. Clustering by the Bry-Curtis percent dissimilrity index utilizing the flexible strtegy ( = ). the combined nlysis dditionl morphometric vribles were considered (the coded vribles). In ddition these vribles hd inherently less vribility being integer vlues. Perhps insted of coded vribles, fetures such s eye position nd cudl fin shpe should be quntified by continuous vlues derived by multidimensionl shpe nlysis. These continuous vlues would hve more inherent vrition thn the coded integer vlues. In both nlyses certin species groups were pprent. The first group ws comprised of H. jgun, A. hepsetus nd M. peninsule. A second consis- Fig. 7. Cluster nlysis of fifteen untrnsformed morphometric vribles for ten species of segrss fishes. The ten mensurl vribles expressed s percent of stndrd length. Clustering by the Bry-Curtis percent dissimilrity index utilizing the flexible strtegy ( = ). tent group included F similis nd F crpio. When ll chrcters were considered C. schoepfi nd S. scovelli were closer to this group in morphospce thn to the other species. In both nlyses, but more so in the combined nlysis, L. rhomboides nd E. gul were close in morphospce. The ctfish, A. felis, ws seprted from the other species. Cluster nlysis bsed on ll untrnsformed mor-
51 phometric vribles grouped the species loosely by size. Ancho hepsetus nd H. jgun clustered together (long with F similis nd E. gul), nd seprted from the smller M. peninsule. However, cluster nlysis of ll vribles with mensurl vribles expressed s rtio of body length grouped the fishes primrily by shpe. In this cse, L. rhomboides nd E. gul gin formed tight group with F crpio t higher level, nd the group comprised of H. jgun, M. peninsule, nd A. hepsetus ws retined nd joined to A. felis t higher level. 1.s IRI cluster.4...i I Group 1 fishes The group including H. jgun, A. hepsetus nd M. peninsule ws chrcterized by common trophic nd microhbitt morphometric chrcters : compressed fusiform body with forked cudl fin, long, closely spced gill rkers, short to intermedite length pectorl fin, pointed pectorl fin, reltively lrge (A. hepsetus nd H. jgun), lterl eye, short hed, nd terminl or subterminl mouth. This form is common to pelgic or mid-wter inhbiting fishes tht re more specilized for cruising nd seeking evsive prey (Kest & Webb 1966, Aleev 1969, Cho & Musick 1977, Gtz 1979, Webb 1984, Wikrmnyke 199). This morphology confers considerble mobility nd mneuverbility nd is common to freshwter plnktivores (Kest & Webb 1966). Reltively short hed length, s found in these species, ws correlted with smll prey size in strem fishes (Gtz 1979), nd presumbly with smll prey (primrily copepods) in these species.. s m x n n m r C Y m s n z V e m H e ' 7 m 4 e 61 Fig. 8. Dietry cluster, bsed on IRI vlues, for nine species of segrss fishes. Clustering by Bry-Curtis percent dissimilrity index utilizing the flexible strtegy ( = ) (from Mott et l. 1995). Wtson & Blon (1984) identified four recurring ecomorphologicl ptterns mong strem fishes in Borneo. The pelgic type ws chrcterized by high cudl fin spect rtio, incresed lterl compression, peduncle compression nd reltive depth, lterl eye, nd high pectorl fin spect rtio. Intr- Tble. Horn's (1966) index of niche overlp bsed on IRI vlues for nine species of fishes in Tmp By, Florid ( = ) (Mott et l. 1995). Species 1 4 5 6 7 8 9 1. A. fells 1..64.19.6. 87.65.14.7.15. A. hepsetus 1.. 7. 5.1 8.788.5 9.7 5. 59. C. schoepfi 1..4.59.175.49.157. 4. S. scovelli 1..1 9. 79.6. 5.19 5. L. rhomboides 1..196.1 6.168.114 6. F crpio 1.. 61.796. 5 7. F similis 1.. 5. 84 8. H. jgun 1.. 8 9. E. gul 1.
5 specific morphologicl polymorphism in bluegill sunfish hs been found to be relted to forging behvior nd microhbitt utiliztion. Open wter inhbitnts hd fusiform bodies nd short fins, wheres littorl vegettion feeders, which re suited for mneuvering, hd deep bodies, long pelvic nd pectorl fins, nd pectorl fins ttched in posterior position (Ehlinger & Wilson 1988, Ehlinger & Gross 199 ). Bluegill with longer pectorl fins consistently serched more slowly nd spent more time in the vegettion hbitt compred to bluegill with shorter pectorl fins (Ehlinger 199). Both H. jgun nd A. hepsetus were mid-wter plnktivores, filter feeding primrily on copepods. They hd high dietry overlp, nd clustered closely by diet with F crpio. Lucs (198 ) found tht Menidi peninsule fed selectively on clnoid copepods nd brncle cypris lrve s dults, wheres grvid femles primrily fed on fish lrve nd mphipods. Hrengul jgun, A. hepsetus nd M. peninsule hd reltively long, closely spced gill rkers. Long, closely spced gill rkers re ssocited with plnktivorous filter feeders (Lgler et l. 196, Cho & Musick 1977) lthough the extent to which gill rker spcing determines filtrtion efficiency is not cler Tble 4. (Top) Eigenvlues for cnonicl correspondence nlysis nd detrended cnonicl correspondence nlysis of 15 mensurl nd coded morphologicl vribles with IRI vlues for eighteen very bundnt prey tx (Hill's ) for nine species of segrss fishes (M. peninsule excluded) ; (Bottom) eigenvlues for cnonicl correspondence nlysis nd detrended cnonicl correspondence nlysis of seven morphologicl vribles ssocited with microhbitt utiliztion (body depth, body width, pectorl fin length, eye dimeter, cudl fin shpe, pectorl fin shpe, eye position) with IRI vlues for eighteen very bundnt prey tx (Hill's ) for nine species of segrss fishes (M. peninsule excluded). Diet xes Eigenvlues 1 4 CCA.. 7.1.8 DCCA.. 6.9. Diet xes Eigenvlues 1 4 CCA.55.17.7. DCCA.55.17.1. (see Snderson & Cech 199 ). Hrengul jgun nd A. hepsetus lcked upper jw protrusion s is common of filter-feeding fishes (Cho & Musick 1977). Menidi peninsule most likely picks its prey with its smll, protrusible mouth. Therefore, morphologicl similrity in these species ws relted to dietry similrity, prticulrly between H. jgun nd A. hepsetus. Exmining n intertidl fish ssemblge off Cliforni, Grossmn (1986) similrly found PC1 to be generl size-relted component, nd PC to be trophiclly linked. Principl component ws strongly influenced by number of gill rkers, mouth orienttion, nd eye position. Wikrmnyke (199) found very similr suite of chrcters ssocited with digestive efficiency, forging behvior, nd forging position in tropicl strem fish ssemblge. Group fishes Principl components nlysis of ll chrcters seprted F crpio, F similis, C. schoepfi, nd S scovelli from the other species. This group ws chrcterized by rounded cudl nd pectorl fins, nd short or no (C. schoepfi) gill rkers. Fundulus similis nd F crpio clustered closely in morphospce when ll vribles were considered, nd with S. scovelli when only mensurl vribles were considered. Fundulus similis nd F crpio were united by suite of chrcters including smll body size, rounded or truncte cudl fins, rounded pectorl fins, short pectorl fins, smll nd lterl eyes, subterminl mouth, short gill rkers, nd smll mouth width nd body depth. In these species, morphology ws reflective of their epibenthic microhbitt utiliztion. Morphologiclly, F similis, F crpio, CC schoepfi, nd S. scovelli re typicl of slow swimming, less mneuverble, epibenthic fishes tht re unble to sustin long periods of high-speed swimming (Kest & Webb 1966, Aleev 1969, Webb 1984). Although they occupied similr epibenthic microhbitts, F similis nd F crpio frequented shllow inshore wters, wheres C. schoepfi ws found mostly in deeper, snd nd segrss benthic hbitts (personl obser-
5 vtion). Syngnthus scovelli ws primrily cptured mong segrss bldes. Dietry similrity mong these four species did not correlte with morphologicl similrity. Floridichthys crpio primrily fed on copepods presumbly by picking or suction, consequently, it clustered by diet with Group 1 fishes, lthough it did not group with those species in morphospce. Although F similis nd C. schoepfi grouped together by Index of Reltive Importnce (long with E. gul), their diets were only superficilly similr. Fundulus similis fed primrily on smll (.4 -. mm length) bivlves s weiil s eggs which were ingested intct, nd C. schoepfi crushed lrge (operculum dimeter.-.5 mm) gstropods, bivlves (1- cm length), nd brncles. Inclusion of bivlves, lbeit very different sizes, primrily ccounted for the dietry clustering of these species (Mott et l. 1995). Although these species occupied similr microhbitts, prticulrly F crpio nd F similis, there ws low dietry overlp mong them. Syngnthus scovelli primrily utilizes suction feeding on mphipods nd shrimp nd ws n outlier species in terms of both diet nd morphology. Its suprterminl mouth nd dorsolterl eyes suit it for cpturing prey bove its body, nd its lck of dentition is chrcteristic of suction feeding fishes (Suyehiro 194, Lgler et l. 196, Dvis & Birdsong 197, Alexnder 1974, Mott 1985,1988). Group fishes Principl components nlysis grouped E. gul nd L. rhomboides closely in morphospce. The size independent cluster nlysis bsed on shpe nd proportionl vribles grouped L. rhomboides, E. gul, nd F crpio. Eucinostomus gul nd L. rhomboides were united not only by their sub-gibbose body shpe, but lso by their forked cudl fins, pointed pectorl fins, lrge eyes, lterl eye position, nd subterminl mouth. Lgodon rhomboides hd lrger mouth, nd longer nd more closely spced gill rkers thn E. gul. There ws generlly little dietry similrity nd overlp between the species t this study site. Mott et l. (1995) found L. rhomboides to feed primrily on lge nd tuni- ctes. The pinfish is the numericlly dominnt species within Thlssi testudinum beds long the subtidl res of the Gulf of Mexico (Hnsen 1969) nd n importnt predtor on mcrobenthic orgnisms within these segrss beds (Young & Young 1978). This species undergoes severl ontogenetic dietry shifts which my correspond with food vilbility (Huh & Kitting 1985), lthough the dt re conflicting. An incresed tendency towrds crnivory with growth ws reported by Subrhmnym & Drke (1975), nd Crr & Adms (197 ). This contrsts with the ontogenetic shift to herbivory cited by Drnell (1958), Hnsen (1969), Stoner (198), nd Stoner & Livingston (1984). Eucinostomus gul hd more diverse diet with five very bundnt prey items, polychete worms, bivlves, cumcens, mphipods, nd gstropods. These findings re consistent with other studies. Copepods dominted the diet of smller size clsses nd were grdully replced by polychetes s size incresed (Springer & Woodburn 196, Crr & Adms 197, Brook 1977, Livingston 1984). Both L. rhomboides nd E. gul were epibenthic forgers over sndy substrtes nd within segrss beds (personl observtions). Mojrrs (Gerreide) use their extremely protrusible mouth to bite or suck their benthic prey off the substrte (Cyrus & Blder 198, personl observtions). Lgodon rhomboides either bites off pieces of segrss nd lge with verticlly opposed, stright-edged incisiform teeth (Stoner & Livingston 1984), or, suction or rm feeds on elusive prey t this size (K.E Liem personl communiction). Protrusible upper jws re typicl of fishes tht utilize either suction feeding, picking or biting during feeding (Mott 1984, 1985, 1988, Liem 198). Lgodon rhomboides, E. gul, nd F crpio ll hd the most protrusible mouths of the species exmined (.7%,.5%,.7% of stndrd length, respectively) nd ll suck or bite their prey off the substrte. Morphologicl similrity between L. rhomboides nd E. gul ws not relted to diet, but more to microhbitt utiliztion nd how they fed. Their more compressed, sub-gibbose body, long, pointed pectorl fins, nd forked cudl fins mke them suitble for greter mneuverbility nd speed (compred to C. schoepfi, F similis, F crpio, nd S. scovelli) s
5 4 they suck or bite their reltively lrge prey within segrss beds or over sndy substrtes (Kest & Webb 1966, Gtz 1979, Webb 1984). Outlier species Syngnthus scovelli (discussed previously) nd A. felis were seprted from most of the other species in morphospce. Arius felis is lrge bodied with forked cudl fin, long, pointed pectorl fin, slightly dorsolterl eye, subterminl wide mouth, long widely spced gill rkers, nd ventrl brbels. Its fusiform body shpe grouped it with the mid-wter plnktivorous species. However, the ictlurid body form is suited for bottom feeding (Kest & Webb 1966). The importnce of crbs nd tunictes in its diet clustered it with L. rhomboides which lso consumed tunictes lthough dietry overlp ws low between the species. Correspondence between morphology nd diet Cnonicl correspondence nlysis is powerful tool for direct mesurement of the ssocition between environmentl nd species dt. We found n overll poor correltion between the morphologicl vribles under investigtion nd diet, indicting tht the species distributions (morphology) did not differ much long the environmentl grdient (dietry grdient) (ter Brk 1986). Even when morphologicl chrcters ssocited with microhbitt were considered (body depth, body width, pectorl length, eye dimeter, cudl shpe, pectorl shpe, nd eye position) there ws poor ssocition with diet. The only group in which there ws some congruence in morphology nd diet ws in the plnktotrophic, mid-wter group 1 fishes : H. jgun, A. hepsetus, nd M. peninsule. These species consistently grouped together in morphology, nd hd high dietry overlp. However, in this group of ten species dietry similrity ws not necessrily predictive of morphologicl similrity, for exmple, F crpio hd high dietry overlp nd clustered by IRI with the bove three species, yet ws morphologiclly quite distinct. Similrly, morphologicl similrity ws not necessrily predictive of dietry similrity, s exemplified by the L. rhomboides - E. gul, nd F crpio - F similis species groups which hd similr morphologies yet low dietry overlp. The generl lck of correltion between morphology nd diet is not surprising s morphology my not only be correlted with wht fish feeds on, but lso with feeding behvior (e.g. suction, biting) or microhbitt utiliztion. Our study indictes tht the `fit' is not simply between morphology nd diet, but lso between morphology nd microhbitt utiliztion. Quntittive ssessment of microhbitt utiliztion in these segrss fishes would hve llowed us to test the ssocition between morphology nd hbitt use. Gtz (1979), Moyle & Sennyke (1984), Dougls (1987), Wikrmnyke (199) nd Winemiller (1991) hve found tht morphologicl diversifiction nd speciliztion in strem fishes ws ssocited with dietry nd/or microhbitt speciliztion. iche compression, or speciliztion in strem fish communities occurred primrily in reltion to hbitt selection, in the cse of rinforest fishes of north Borneo by verticl strtifiction, nd secondrily in preference for food resources (Wtson & Bton 1984). Grossmn (1986) found tht morphologicl similrity ws poor predictor of dietry similrity in n intertidl fish ssemblge. Similr to our findings with such species s E. gul nd L. rhomboides, he found tht in some cses species which were quite similr morphologiclly frequently possessed very different diets nd vice vers. Pcific nd Western Atlntic butterflyfishes exhibited cses of convergence, divergence, nd prllelism in jw morphology; nd jw nd hed morphology ws correlted with how these fishes feed, rther thn with wht they consume (Mott 1985,1988). The inconsistencies in ecomorphologicl studies ttempting to relte morphology to dietry preference re to be expected owing to the numerous fctors tht cn influence the reltionship. A vriety of behviorl, ecologicl, physiologicl, nd morphologicl constrints cn confound ecomorphologicl reltionships. These constrints cn be evolutionry (historil) or current. Current constrints my
5 5 be ecologicl (e.g. environmentl instbility, resource vilbility, competition), behviorl (e.g. behviorl flexibility), physiologicl (e.g. sensory limittions, nutritionl requirements), or morphologicl (e.g. structurl nd sptil limittions on combining functionlly relevnt forms, phenotypic plsticity) (Mott & Kotrschl 199 ). One ecologicl constrint tht cn ffect ecomorphologicl reltionships in study such s this is resource vilbility over the species rnge. The diet of ech species should be exmined throughout its rnge nd over long enough time period to void loclized vribility. These limittions re usully too difficult to ddress nd only few studies hve ddressed them (see Grossmn 1986). Similrly, how nd where n orgnism feeds must be exmined over its sptil nd temporl rnge before ecomorphologicl ptterns cn be scertined. There is lso evidence to believe tht resource prtitioning (Ross 1986), nd consequently ecomorphologicl ptterns relting to resource use, will not necessrily be similr in different ecosystems such s mrine or freshwter hbitts, strems, lkes, corl reefs, subtropicl segrss beds nd the like. Furthermore, vrious nlyticl methodologies will ffect the puttive correltions : the choice of morphologicl chrcters ; s we hve demonstrted, lumping of mensurl nd coded vribles significntly chnges the principl components nlysis, utilizing rtios or rw mesurements, nd the method of dietry nlysis, for exmple, whether one presents the dt volumetriclly, s dried or wet weights, s percent frequency of occurrence, or s some cumultive index such s the Index of Reltive Importnce. There is, therefore, no surprise to us tht there is so much vribility nd lck of concordnce mong the ecomorphologicl studies of fish feeding. Perhps we should seek ecosystemspecific ptterns, nd stndrdized methods or t lest compre the different methodologies. Even when correltions re found between diet or microhbitt use nd morphology, we lck the certinty to scertin cusl reltionships. Ecomorphologicl studies must then proceed to the more difficult step, performnce testing of the form-function complex, for exmple, the feeding efficiency of vrious gill rker designs. Phylogenetic ptterns It hs been rgued tht exmining more distntly relted species, rther thn those with high degree of txonomic reltedness, decreses the probbility of detecting ecomorphologicl ptterns becuse choosing closely relted species will reduce the risk tht coincidentl differences will msk significnt ptterns (Huey & Bennet 1986), nd closely relted species tht hve long history of evolution nd rdition in the sme region re more likely to hve ecomorphologicl reltionships tht re detectble (Findley & Blck 198 ). However, re-occurring ecomorphologicl reltionships mong more distntly relted tx provide powerful evidence for convergence (Krr & Jmes 1975, Wiens 1991b, Losos 199, b, Mott & Kotrschl 199, Winemiller et l. 1995) nd reduce the probbility tht the ecomorphologicl pttern is chnce event, but rther one shped by evolutionry forces relted to tht prticulr ecomorphologicl reltionship. In order to scertin tht different funs hve evolved similr ptterns of niche diversifiction in response to similr environmentl fctors one must hve phylogeny to distinguish between convergence nd prllelism nd to identify historicl design constrints mong contemporry tx. Furthermore, one must hve resonbly comprble units nd scles mong : (1) heritble morphologicl trits tht reflect ecologiclly relevnt functions, ( ) funs nd tx, nd ( ) regions nd physicl nd biotic environments (Winemiller et l. 1995). It my then be possible to rigorously test evolutionry ecomorphologicl hypotheses s hs been outlined by Felsenstein (1985), Losos (199, b), Winemiller (1991), Winemiller et l. (1995), Wesnet (1995). With the vilbility of phylogeny of this brod txonomic group, nd morphologicl chrcters tht re ecologiclly relevnt, we cn t lest mke generl sttements bout evolutionry convergence nd prllelism in this group of segrss fishes. These ten species of generlly distntly relted fishes formed vriety of groups tht clustered in morphospce, indicting convergence nd prllelism in form. The only good correltion between dietry similrity nd morphologicl similrity oc-
5 6 ' rotoosnthoptorsll' Ptomlltormoo U1pItormoo Myotophltormos P n Os t II opt p ryg II slenlformss Os.roptotformois -== =---o /posulformss Fig. 9. Prtil phylogeny of the Teleostei bsed on Luder & Liem (198 ) with the ten species of segrss fishes under investigtion indicted. curred for the group of mid-wter, plnkton-feeding fishes : A. hepsetus, H. jgun, nd M. peninsule. The former two species re more closely relted (Fig. 9), re closer to the more primitive teleost body form thn the other species, nd shre the ncestrl chrcters of forked cudl fins, lterl eyes, nd intermedite length pectorl fins (Jmes Albert personl communiction). Similrity in the chrcters between these clupeomorph fishes nd the therinoid silverside is most likely due to evolutionry convergence. The epibenthic, highly mobile nd mneuverble benthic-feeding perciform species E. gul nd L. rhomboides re reltively closely relted (Fig. 9) nd presumbly shre derived [sub-gibbose body form with long, pointed pectorl fins, subterminl mouth, protrusible mouth (Scheffer & Rosen 1961)] nd ncestrl chrcters (forked cudl fins
57 nd lterl eyes). Close phylogenetic reltedness most likely indictes prllel evolution in mny chrcters. As group, the epibenthic cyprinodontids E similis nd F c rpio show convergence in some chrcters with C. schoepfi nd S. scovelli, notbly in fin shpe (more rounded pectorl nd cudl fins) nd reduction in gill rker size. Ecomorphologicl convergence in these segrss fishes is relted both to microhbit t nd trophic utiliztion, s hs been identified in other groups. Winemiller (1991) similrly identified convergence in chrcters ssocited with diet nd micro-hbitt in five regionl ssemblges of fresh wter fishes. In this ssemblge of ten species of segrss fishes, reltively few microhbitt nd trophic chrcters ccounted for most of the vrince in morphology. Although Felley (1984) cutioned tht ecomorphologicl ssocitions shown from one group of species my not be relevnt to other groups, we note tht ecomorphologicl studies encompssing freshwter nd mrine fishes, including the works of Gtz (1979), Felley (1984), Moyle & Sennyke (1984), Wtson & Blon (1984), Grossmn (1986), Mott : (1988), Wikrmnyke (199), Winemiller (1991), nd this study, hve found tht : (1) ecomorphologicl ssocitions, when they occur, re relted primrily to microhbitt utiliztion nd feeding ; nd ( ) reltively few morphologicl chrcters ccount for most of ssocition with ecology. They include, not in ny prticulr order of importnce : body size nd shpe, gill rker length nd spcing, mouth orienttion nd size, eye position nd size, gut length, shpe nd size of the pectorl nd cudl fin, hed length, tooth shpe nd size, cudl peduncle shpe nd size, degree of jw protrusion, nd presence/bsence of brbels. Ecomorphologicl studies should perhps focus on these morphologicl chrcters when evolutionry ptterns re sought. In summry, this ssemblge of ten distntly relted species of subtropicl segrss fishes demonstrted generlly poor correspondence between morphology nd diet. Morphologicl similrity ws only reflective of dietry similrity in the guild of mid-wter, plnktotrophic fishes. Morphologicl similrity in most of the remining fishes ws ppr- ently reflective of microhbitt utiliztion nd feeding behvior. In generl, three groups segregted out : (1) group of mid-wter fishes specilized for cruising nd seeking out evsive prey ; ( ) slow swimming, less mneuverble epibenthic fishes tht picked or sucked their prey off the substrte ; ( ) nd group of more mobile nd mneuverble epibenthic forgers. Within this ssemblge, cses of convergence in trophic nd microhbitt utiliztion chrcters were pprent in some of the groups. Future ecomorphologicl studies on fishes, nd segrss fishes in prticulr, should exmine correltions between morphology nd diet, microhbitt utiliztion nd forging behvior. Acknowledgements This study ws funded in prt by University of South Florid President's Reserch Awrd P.J.M. We would like to thnk Rebecc Wilcox, Robert Windheuser nd ll field volunteers for their ssistnce in mking the reserch possible. References cited Aleev, Y.G. 1969. Function nd gross morphology in fish. Akd. Sci. USSR, Sevstopol Biol. Stn., Isrel Progrm for Sci. Trnsl., Jeruslem. 68 pp. Alexnder, R.Mc. 1974. Functionl design in fishes. Hutchinson University Librry, London. 16 pp. Atchley, WR., C.T. Gskins & D. Anderson. 1976. Sttisticl properties of rtios. I. Empiricl results. Syst. Zool. 5 : 1 7-148. Block, W.M., L.A. Brennn & R.J. Gutierrez. 1991. Ecomorphologicl reltionships of guild of ground-forging birds in northern Cliforni, USA. Occologi 87 :449-458. Brook, I.M. 1977. Trophic reltionships in segrss community (Thlssi testudinum), in Crd Sound, Florid. Fish diets in reltion to mcrobenthic nd cryptic funl bundnce. Trns. Amer. Fish. Soc. 16 : 19-9. Crr, W.E.S & C.A. Adms. 197. Food hbits of juvenile mrine fishes occupying segrss beds in the esturine zone ner Crystl River, Florid. Trns. Amer. Fish. Soc. 1 : 511-54. Cho, L.. & J.A. Musick. 1977. Life history, feeding hbits, nd functionl morphology of juvenile scienid fishes in the York River Estury, Virgini. U.S. Fish. Bull. 75 : 657-7. Comp, G.S. 1985. A survey of the distribution nd migrtion of the fishes in Tmp By. pp. 9-4 5. In : S.F Tret, J.L. Simon, to
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