Feeding Ecology And Ecomorphology Of Cichlid Assemblages .
Environ Biol Fish (2018) 43-1Feeding ecology and ecomorphology of cichlid assemblagesin a large Mesoamerican river deltaAllison A. Pease & Manuel Mendoza-Carranza &Kirk O. WinemillerReceived: 17 August 2017 / Accepted: 5 February 2018 / Published online: 13 February 2018# Springer Science Business Media B.V., part of Springer Nature 2018Abstract Fish assemblages in tropical lowland riversare characterized by a high richness of species that feedon a diverse array of food resources. Although closelyrelated species often have similar feeding ecology, species within the family Cichlidae display a broad spectrum of trophic niches, and resource partitioning hasbeen inferred from studies conducted in Neotropicalrivers. We investigated interspecific variation in foodresource use and its relationship to morphological variation among cichlid fishes within the Pantanos de CentlaBiosphere Reserve, a coastal area encompassing thedelta of the Grijalva-Usumacinta River in Tabasco,Mexico. Most species consumed benthic crustaceans,aquatic insect larvae, and detritus, but some were moreherbivorous, and one species was a specialized piscivore. Dietary niche overlap among species was higherthan expected for one assemblage, and similar to random expectations for another, suggesting a lesser rolefor resource partitioning than has been shown for somecichlid assemblages, perhaps due to availability of abundant resources, even in low-water conditions. Canonicalcorrespondence analysis revealed that greatest morphological differences am7ong species involved functionaltraits directly associated with resource use. Relationships between feeding ecology and morphology weresimilar to those described for other riverine cichlids.Strong ecomorphological relationships facilitate inferences about the ecology of cichlid species, includingspecies that currently lack data from field studies.Knowledge of ecological relationships will be importantfor conservation in the Pantanos de Centla, an ecosystem of global significance for biodiversity and ecosystem services.Keywords Cichlidae . Morphological traits . Nicheoverlap . NeotropicalIntroductionA. A. Pease (*)Department of Natural Resources Management, Texas TechUniversity, Box 42125, Lubbock, TX 79409-2125, USAe-mail: allison.pease@ttu.eduM. Mendoza-CarranzaSustainable Management of Basin and Coastal Zones ResearchGroup, El Colegio de la Frontera Sur (ECOSUR) UnidadVillahermosa, Km 15.5 s/n Carreterra a Reforma, RancheriaGuineo 2a, 86280 Villahermosa, Tabasco, MexicoK. O. WinemillerDepartment of Wildlife and Fisheries Sciences, Texas A&MUniversity, 2258 TAMU, College Station, TX 77843-2258, USAIn species-rich freshwater fish assemblages, cooccurring species occupy a diverse suite of trophicniches, and some have been found to partition resources,presumably to reduce interspecific competition (Ross1986; Winemiller and Pianka 1990; Herder andFreyhof 2006). Species within the same family are oftenecologically similar due to phylogenetic niche conservatism (e.g., McNyset 2009), but closely related speciesmay occupy diverse trophic niches in regions whereecological adaptive radiations have occurred (Schluter2000). In the incredibly diverse cichlid communities of
868Lake Malawi in Africa, Genner et al. (1999a, 1999b)found that cichlids coexisting along rocky shoresshowed significant differences in food resource use,but many species had considerable dietary overlap.They suggested that ecological segregation may not benecessary to support coexistence in these diverse cichlidassemblages. In more dynamic fluvial habitats, environmental variation often causes shifts in resource availability (Grossman et al. 1998), and trophic segregationmay occur during periods when fish densities are highwhile habitat and food availability are low (Winemiller1990, 1991b; Winemiller and Kelso-Winemiller 2003).Cichlids in the Neotropics consume a broad array ofresources, from aquatic macrophytes to other fishes,with some being trophic specialists while retaining anability to exploit a variety of food items (LoweMcConnell 1991; Winemiller et al. 1995; Montaña andWinemiller 2013). Differences in dietary preferences arelikely to be reflected in morphological traits related toforaging and consuming food. Prior studies of riverinecichlids have revealed strong relationships betweenmorphological traits and diet (e.g., Winemiller et al.1995; López-Fernández et al. 2012; Montaña andWinemiller 2013). For example, Winemiller et al.(1995) found that across continents, riverine cichlidsshowed convergent relationships between traits such asgut length, gape size, and head length and the proportionof fishes, invertebrates, vegetation, and detritusconsumed.Cichlids comprise a major component of the freshwater fish fauna of Mesoamerica, and the evolution andzoogeography of the group (subfamily Cichlinae) hasbeen studied extensively (e.g., Martin and Bermingham1998; Hulsey et al. 2004; López-Fernández et al. 2013).Centers of Mesoamerican cichlid diversity, such as theRío Grijalva-Usumacinta region of southern México,contain many coexisting cichlid species that displayconsiderable morphological diversity that likely reflectsniche diversification (Myers 1966; Bussing 1985; Peaseet al. 2012). Studies in other Mesoamerican regions(e.g., Winemiller et al. 1995; Cochran-Biederman andWinemiller 2010) suggest that coexisting cichlid speciespartition trophic niches. Relatively little ecological information is available for cichlids of the Lower GrijalvaUsumacinta (Miller 2005) despite the high diversity andimportance of many species for small-scale fisheries(Mendoza-Carranza et al. 2013).In this study we examined diets, niche breadth, andniche overlap of coexisting cichlid species in theEnviron Biol Fish (2018) 101:867–879Grijalva-Usumacinta River delta within the Pantanosde Centla Biosphere Reserve in Tabasco, México. Wealso sought to identify relationships between morphological features and the feeding ecology of cichlids inthese assemblages. We carried out the study during thedry season, a period when dietary niche partitioning hasbeen shown for other fluvial cichlid assemblages (e.g.,Winemiller 1991b; Jepsen et al. 1997). During lowwater periods, availability of food resources declinesand densities of most fish species increases, which increases the potential for competition. We also hypothesized that morphological variation among cichlidswould involve traits directly related to trophic resourceuse in a manner similar to ecomorphological relationships documented for other fluvial cichlids (e.g.,Winemiller et al. 1995; Cochran-Biederman andWinemiller 2010; Montaña and Winemiller 2013). Information on the trophic ecology of cichlid fishes in theLower Grijalva-Usumacinta should enhance management of fisheries resources and conservation of thisregion’s unique biodiversity.Materials and methodsStudy sites and data collectionThe Grijalva and Usumacinta join together in Tabasco,Mexico to form the largest river of Mesoamerica and amajor center of fish diversity (Myers 1966; Bussing1985; Miller 2005). Approximately 115 fish speciesfrom 31 families have been documented in theGrijalva-Usumacinta region, and an estimated 36% ofthese species are endemic (Miller 2005). Cichlids are themost species-rich family in this region, with many species occurring together in local assemblages (RodilesHernández et al. 1999; Miller 2005; Soria-Barreto andRodiles-Hernández 2008).Sampling locations were within the Pantanos deCentla Biosphere Reserve (Fig. 1), a vast protected areawithin the Lower Grijalva-Usumacinta Basin which wasdesignated by the RAMSAR convention of 1995 as awetland of international significance. San Pedrito Lagoon (18 20′36 N 92 33′50 W) is a permanent freshwater lagoon with expansive beds of aquatic macrophytes (chiefly Vallisneria americana) and shorelinesdominated by reeds (Phragmites australis). Polo Stream(18 29′21 N 92 38′23 W) is a slow-moving,mangrove-dominated freshwater tributary of the Río
Environ Biol Fish (2018) 101:867–879869Fig. 1 Map of the study area within Pantanos de Centla Biosphere Reserve, Tabasco, MexicoGrijalva below its confluence with the Río Usumacinta.Along the shorelines of the stream, structural cover isprovided by riparian plants (mangrove trees and terrestrial grasses), and the sandy substrate is covered withcoarse particulate organic matter. A detailed descriptionof these study sites is given in Mendoza-Carranza et al.(2010) and Sepúlveda-Lozada et al. (2015). Intensivesurveys were carried out in February and March 2007during the dry season (Espinal et al. 2007; YáñezArancibia et al. 2009). In Pantanos de Centla, the dryseason is characterized by low water levels ( 2 m inPolo Stream and 1 m in San Pedrito Lagoon), lowturbidity (0.90–1.5 m Secchi depth), and low salinity(4–5 UPS) (Arévalo Frías and Carranza 2012;Sepúlveda-Lozada et al. 2015). Precipitation in Tabascoduring February and March 2007 was 127.0 and55.8 mm, respectively, corresponding to the lowest valuesof the year (Servicio Meteorológico Nacional 2017).Specimens were collected using seine nets, gill nets,hook and line, and a boat-mounted trawl net. Though allmain mesohabitat types were sampled at the sites, thespecimens used for this study were captured among theVallisneria beds in San Pedrito (depths of 0.5–1 m), andalong the vegetated shorelines of Polo Stream (depths of0.1–1.2 m), areas where cichlids were abundant anddiverse. Specimens were identified following Miller(2005) and deposited in the fish collection at El Colegiode la Frontera Sur in Villahermosa, Tabasco.Given that the objective of this study was to evaluateinterspecific patterns of morphological and dietary diversity within local species assemblages, juvenile size classes, which tend to show relatively low interspecific divergence in morphology and diet (i.e., small size classesof all species consume mostly microcrustacea and othersmall aquatic invertebrates), were excluded from analyses. Species that were rarely captured during surveys ofthe mesohabitats (N 5) also were excluded from analysis. Volumetric proportions of stomach contents wereestimated following the methods of Winemiller (1990).Fishes consumed were identified to species when possible, and invertebrates were identified to order. Prey itemswere later grouped into broader categories for statisticalanalyses. These categories were: fishes, mollusks, decapod crustaceans, aquatic insect larvae, benthic meiofauna,aquatic macrophytes, algae, and detritus.Morphological measurements were made on fivespecimens of each species included in the assemblagedataset. Morphological traits were measured to thenearest 0.1 mm using vernier calipers. Followingmethods described by Winemiller (1991a), the following 24 morphological features were measured (Table 1):maximum standard length, gut length, head length, head
870Environ Biol Fish (2018) 101:867–879Table 1 The 24 morphological traits used for Lower Grijalva-Usumacinta cichlid assemblages with trait abbreviations and measurementmethodology. Trait definitions follow Winemiller (1991a) and López-Fernández et al. (2012)Morphological traitCodeTrait descriptionMaximum standardlengthGut lengthmax SL Maximum standard length from specimens collected in this studygut LLength of gut from beginning of esophagus to the anus (divided by standard length)Head lengthhead LDistance from the tip of the jaw to the posterior edge of the operculum (divided by standard length)Head depthhead D Vertical distance from dorsum to ventrum passing through the pupil (divided by body depth)Oral gapegapeVertical distance measured inside of fully open mouth at tallest point (divided by body depth)Eye positioneye PVertical distance from the center of the pupil to the ventrum (divided by head depth)Eye diametereye DHorizontal distance from eye margin to eye margin (divided by head length)Snout lengthsnt LDistance from the pupil to the tip of the upper jaw with mouth shut (divided by head length)Jaw protrusion lengthjaw PrDistance from the pupil to the tip of the upper jaw with mouth fully open and extended (divided bysnout length)Body depthbod DMaximum vertical distance from dorsum to ventrum (divided by standard length)Body widthbod WMaximum horizontal distance (divided by standard length)Caudle peduncle depthped DMinimum vertical distance from dorsum to ventrum of caudal peduncle (divided by body depth)Caudle peduncle widthped WHorizontal width of the caudal peduncle at midlength (divided by body width)Body depth belowmidlineDorsal fin lengthbdbmVertical distance from midline to ventrum (divided by body depth)dor LDistance from anterior proximal margin to posterior proximal margin of dorsal fin (divided by standardlength)Dorsal fin heightdor HMaximum distance from the proximal to distal margin of the dorsal fin (divided by standard length)Anal fin lengthana LDistance from anterior proximal margin to posterior proximal margin of anal fin (divided by standardlength)Anal fin heightana HMaximum distance from proximal to distal margin of the anal fin (divided by standard length)Caudal fin depthcau DMaximum vertical distance across the fully spread caudal fin (divided by standard length)Caudal fin lengthcau LMaximum distance from proximal to distal margin of the caudal fin (divided by standard length)Pectoral fin lengthpec LMaximum distance from proximal to distal margin of pectoral fin (divided by standard length)Pelvic fin lengthpel LMaximum distance from proximal to distal margin of pelvic fin (divided by standard length)Gill raker numberrk num Number of gill rakers in first ceratobranchialGill raker lengthrk LLength of the longest gill raker (divided by standard length)depth, oral gape, eye position, eye diameter, snout length,jaw protrusion length, body depth, body width, caudalpeduncle depth, caudal peduncle width, body depth below midline, dorsal fin length, dorsal fin height, anal finlength, anal fin height, caudal fin depth, caudal fin length,pectoral fin length, pelvic fin length, gill raker number,and gill raker length. Prior to statistical analysis, morphological measurements were standardized for size byconverting to proportions of standard length, body width,or head length as described by Winemiller (1991a).Statistical analysesFor species at each sampling site, dietary niche breadthwas estimated using Levins’s (1968) standardizedindex. Pianka’s (1973) symmetrical index of niche overlap was calculated as a measure of dietary similaritybetween species. Both indices were calculated usingvolumetric proportions of the nine aggregated prey categories above. For both measures, values may rangefrom 0 to 1, with higher values indicating greater dietdiversity and more complete overlap. To test whetherdietary niche overlap was higher or lower than randomexpectations, a randomization test (1000 iterations) wasalso performed using the niche overlap module ofEcoSim Professional (Entsminger 2014). We used theBconserved-zeroes algorithm of Winemiller and Pianka(1990) in the randomization, retaining the nichebreadths of species and the zero structure of the foodresource use matrix (i.e., resources not used by a species
Environ Biol Fish (2018) 101:867–879remained unused in the randomization). Mean observedand randomized niche overlaps by nearest neighbor rankwere also plotted.To ordinate species within assemblage morphological space, principal components analysis (PCA) wasperformed based on the correlation matrix of logtransformed morphological data (species average traitvalues). Relationships between diet (using data fromboth survey sites) and morphology were examinedusing canonical correspondence analysis (CCA). Thisallowed for measurement of the amount of variationin dietary resource use that could be explained by axesof morphological variables. The statistical significance of the diet-morphology relationship fromCCA was assessed with a permutation test (1000simulations). Both ordination analyses were performed using the Vegan package in R version 2.11.1(R Foundation for Statistical Computing 2010).To examine phylogenetic signal in the diet composition of cichlid species, we used the test for phylogeneticserial independence (TFSI, Abouheif 1999; Pavoineet al. 2008) with mean proportions of the eight preycategories above as traits. The phylogeny of Mesoamerican cichlids from Rican et al. (2016) was used, and theanalysis was performed using Phylogenetic Independence v.2.0 (http://biology.mcgill.ca/faculty/abouheif/).For each dietary category, a C statistic was calculated forphylogenetic autocorrelation, and topology of theoriginal data was randomized 1000 times to generate anull distribution for assessing statistical significance.ResultsTwelve species of native cichlids were captured duringsurveys of Pantanos de Centla Biosphere Reserve. Theeight most abundant species (Petenia splendida, Viejamelanura, Vieja bifasciata, Mayaheros urophthalmus,Trichromis salvini, Cribroheros robertsoni, Thorichthyspasionis, and Thorichthys helleri) were used for dietaryand morphological analyses (total of 323 individuals).Four additional species were collected in small numbers: Cincelicthys pearsei, Maskaheros argenteus,Thorichthys meeki, and Thorichthys socolofi.Thorichthys helleri was by far the most abundant species at both sites (n 99). All species were present atboth sites; more C. robertsoni were collected at the PoloStream site, and adult size classes of P. splendida wereonly captured from San Pedrito Lagoon.871Examination of stomach contents revealed that mostspecies consumed benthic meiofauna, aquatic insectlarvae, and detritus (Table 2). The two Vieja specieswere largely herbivorous/detritivorous, consuming largeproportions of coarse vegetative detritus and aquaticmacrophytes. Petenia splendida was a piscivore with adiet restricted to fishes (mostly juvenile cichlids). Thetwo Thorichthys species and C. robertsoni consumedsmall benthic invertebrates (benthic meiofauna, insectlarvae, and gastropods) along with coarse detritus.Thorichthys helleri consumed a higher proportion ofsnails than the other invertebrate feeders. Trichromissalvini and M. urophthalmus had more generalist, omnivorous diets composed of shrimp and smaller invertebrates as well as detritus and plant matter. In PoloStream, all cichlid species consumed substantial proportions of detritus. In general, cichlid species consumed more aquatic plants and mollusks (bivalvesand gastropods) in San Pedrito Lagoon. The diet ofM. uropthalmus differed considerably between thetwo sites, with a more carnivorous diet (includinghigh volumes of fish and decapods as well as plants)in San Pedrito Lagoon, and a diet of mostly detritusand plants in Polo Stream. The TFSI tests revealedphylogenetic constraints on the consumption ofaquatic insects (p 0.01) and algae (p 0.04).Dietary niche breadths were widest for theThorichthys species, C. robertsoni, and T. salvini, andthese species consumed relatively even proportions ofvarious invertebrate categories and detritus as well assmall volumes of several other categories (Table 2).Both Vieja species (herbivore-detritivores) andP. splendida (piscivore) had much narrower dietaryniches. For the Polo Stream cichlid assemblage, meandietary niche overlap was 0.61, a value significantlygreater (p 0.001) than expected based on 1000 randomized simulations. Dietary overlaps in Polo Streamwere higher than expected for all nearest neighbor ranks(Fig. 2). Mean dietary niche overlap in the San PedritoLagoon assemblage (0.34) was neither higher (p 0.43)nor lower (p 0.57) than expected based on randomizedsimulations. Across sites, the highest interspecific nicheoverlap was between the two Vieja species and amongthe two Thorichthys species, C. robertsoni, and T.salvini (Table 3). Petenia splendida had very low dietaryoverlap with all of the other cichlid species except forM. uropthalmus.The first two axes from the PCA performed on morphological traits explained 59.9% and 16.0%,
872Environ Biol Fish (2018) 101:867–879Table 2 Average proportional volume of prey items in gut contents of cichlid species at survey sitesSiteSpeciesnPolo StreamThorichthys helleri47 0.021 0.097Thorichthys pasionisSan PedritoLagoonFishMollusks Decapods InsectlarvaeMeiofauna9 0.024 0Plants Algae Detritus Other B0.0140.3830.0810.010 0.010 0.30200.0710.429000.3330.143 0.2600.1150.376000.2460.187 0.370.083 0.35CribroherosrobertsoniTrichromis salvini54 0.036 0.04114 0.108 00.1440.40300.007 00.2160.122 0.36MayaherosurophthalmusVieja bifasciata21 0.063 000.0300.0040.324 00.5760.002 0.1618 0.001 0.0030.0020.0010.0010.033 0.001 0.95800.01Vieja melanura19 0.002 000.0040.0010.022 0.061 0.91000.03Thorichthys helleri52 00.42300.1660.141000.1210.149 0.35Thorichthys pasionis8 0.013 0.17700.2910.1390.089 00.2660.026 0.46CribroherosrobertsoniTrichromis salvini5 00.20700.5290.0290.193 00.0210.021 0.2222 00.0210.0710.1920.0540.104 0.100 0.4540.004 0.33MayaherosurophthalmusVieja bifasciata33 0.324 0.0110.3020.00900.309 00.04500.3000.00300.702 0.041 0.24600.10Vieja melanura16 0000.0170.0020.632 0.243 0.10600.14Petenia splendida22 1.000 0000000.009 0.008 000Bolded numbers highlight dominant prey items that composed a proportion greater than 0.15 of gut content volume. B is Levin’s nichebreadth for each speciesrespectively, of variation among species (Fig. 3). Themorphological gradient along the first axis was associated with differences in jaw protrusion, gape size, gillraker number, body depth, caudal peduncle width, analfin length, pelvic fin length, dorsal fin height, and eyediameter. The second axis was most influenced by differences among species in head length, gut length, bodysize, eye position, and gill raker length. Peteniasplendida had a high positive score on PC1 due to highjaw protrusion, large gape, relatively short fins, smalleyes relative to body size, and few widely spacedgill rakers. Species with lowest scores on PC1 werecharacterized by having relatively long fins, deeperbodies, and more gill rakers. These included theVieja and Thorichthys species. Thorichthys species,C. robertsoni, and P. splendida had high scores onPC 2, which was associated with a relatively longerhead, high eye position, and short gut length. Thetwo Vieja species, which had long guts and relatively large body sizes, had low PC2 scores.Canonical correspondence analysis revealed a significant relationship between diet and morphologicaltraits (p 0.01, 1000 permutations). The first twoaxes represented 51.1% and 29.7% of diet variationexplained by morphology respectively (Fig. 4). Thedominant axis (axis 1) separated the piscivorousP. splendida from all other species. Herbivore/detritivore species were separated from species withmore invertebrates in their diets along the secondaxis. Gape width and extent of jaw protrusionwere positively correlated with axis 1 and stronglyassociated with the proportion of fish in the diet.Gut length was associated with the consumption ofalgae, aquatic macrophytes, and detritus and wasnegatively correlated with axis 2. Head length,snout length, and eye position were positivelycorrelated with axis 2 and with the frequency ofmollusks, benthic meiofauna, and aquatic insectlarvae in stomach contents. Based on the relative position of species in the CCA ordination, there were fourmain ecomorphological groups: piscivores with largegapes and highly protrusible jaws (P. splendida), benthicinvertebrate feeders with relatively long heads andsnouts and higher eye position (Thorichthys spp.,C. robertsoni), herbivore/detritivores with long gutsand shorter head lengths (Vieja spp.), and generalistfeeders with intermediate-sized mouths, heads, and guts(M. urophthalmus and T. salvini).
Environ Biol Fish (2018) 101:867–879873Fig. 2 Mean observed trophicniche overlap for Polo Stream(black boxes) and San PedritoLagoon (grey boxes) along withmean overlaps from the ECOSIMrandomization (open circles) bynearest neighbor rank for eightcommon cichlid species in thePantanos de Centla BiosphereReserveDiscussionTwelve co-occurring native cichlid species were documented in sites within Pantanos de Centla BioshpereReserve, ranking these assemblages among the mostspecies-rich in Mesoamerica (Myers 1966; Bussing1985). High dietary niche overlap was observed amongseveral cichlid species, particularly in Polo Stream,where vegetative detritus was a substantial componentof the diet for all species. Relationships between feedingecology and morphology identified by canonical correspondence were similar to those described for otherNeotropical cichlids (e.g., Winemiller et al. 1995;Cochran-Biederman and Winemiller 2010; Montañaand Winemiller 2013). These strong, consistentecomorphological relationships may be useful forpredicting diet based on morphology for other cichlidassemblages that currently lack data.Most cichlid species consumed a variety of preyitems, including insect larvae, other benthic invertebrates, detritus, and plant material. Despite the highoverlap, four basic feeding groups could be identified.Petenia splendida, a specialized piscivore, had a verynarrow trophic niche distinct from all other species.Table 3 Dietary niche overlap among co-occurring cichlid species calculated using Pianka’s (1973) symmetrical index with volumetricproportions of prey items in gut contentsPolo StreamThorichthys helleriT. hel–T. pasC. robT. salM. uroV. bifThorichthys pasionis0.590–Cribroheros robertsoni0.6510.985–Trichromis salvini0.8010.3500.411–Mayaheros urophthalmus0.5680.5420.4800.423–Vieja bifasciata0.6000.6090.5270.4020.883–Vieja melanura0.6030.6080.5270.4030.8770.998–San Pedrito LagoonT. helT. pasC. robT. salM. uroV. bifV. melThorichthys helleri–Thorichthys pasionis0.769–Cribroheros robertsoni0.6150.782–Trichromis salvini0.4020.8160.437–Mayaheros urophthalmus0.0430.1920.2080.269–Vieja bifasciata0.0830.3730.3170.4880.571–Vieja melanura0.0470.2820.3230.3960.5390.939Petenia splendida00.027000.5970.010V. melP. sple–0–
874Environ Biol Fish (2018) 101:867–879Fig. 3 PCA ordination ofmorphological traits defining theposition of Lower GrijalvaUsumacinta cichlid species in twodimensions of trait space. Traitsused to characterize the two axeshad correlation coefficients 0.2.Abbreviations for morphologicaltraits are given in Table 1Thorichthys helleri, T. pasionis, and C. robertsoni fedprimarily on benthic invertebrates. Vieja bifasciata andV. melanura consumed larger proportions of detritus andaquatic macrophytes. Finally, T. salvini andM. urophthalmus had generalist diets, consuming manykinds of invertebrates as well as detritus, algae and plantmaterial. This is consistent with findings forP. splendida and C. robertsoni in cichlid assemblagesin Quintana Roo, México, (Valtierra-Vega andSchmitter-Soto 2000) and in the Bladen River, Belize(Cochran-Biederman and Winemiller 2010). Trichromissalvini appears to be more omnivorous in the lowlandhabitats in southern Mexico (this study; Hinojosa-Garroet al. 2013) compared to upland streams in Belize(Cochran-Biederman and Winemiller 2010). Similar toour findings for Thorichthys helleri and T. pasionis,other species in the genus Thorichthys have been foundto feed predominantly on benthic invertebrates(Valtierra-Vega and Schmitter-Soto 2000; CochranBiederman and Winemiller 2010). Thorichthys specieshave been described as substrate winnowers or siftersthat ingest sand or other loose sediments; ingested material is then manipulated within the orobranchial chamber in order to separate invertebrate prey from debris,the latter being expelled from the mouth or opercularopening (López-Fernández et al. 2014).Similar spectra of trophic niches were describedfor a less diverse Mesoamerican cichlid assemblage(six species) in Belize (Cochran-Biederman andWinemiller 2010). In addition to piscivores, benthicinvertebrate feeders, herbivore-detritivores, and generalists, Winemiller et al. (1995) found that a CostaRican cichlid assemblage with high species richness(14 species) contained two additional, unique trophicspecialists: algae scraper and frugivore. Some cichlidassemblages in South America contain more cooccurring species, but herbivorous and detritivorouscichlids are rarer in these systems (Winemiller et al.1995). Myers (1966) suggested that Mesoamericancichlid species have filled an exceptionally diverseset of ecological niches owing to the low diversity ofostariophysan fishes compared to other tropical regions. Compared to cichlids in South America, Mesoamerican cichlids, as a group, consume more detritus, algae and vegetation, perhaps due to less competition for those resources from characiform andsiluriform fishes, both historically as well as presently (Winemiller et al. 1995).
Environ Biol Fish (2018) 101:867–879875Fig. 4 Ordination of prey items and morphological traits of common Lower Grijalva-Usumacinta cichlid species on the first two axes of theCCA. Abbreviations for morphological traits are given in Table 1Dietary niche overlap was higher than would bepredicted based on random expectations in the PoloStream cichlid assemblage, and did not differ fromrandom expectations in the San Pedrito Lagoon assemblage. In both sites, dietary overlap was particularly highamong benthic invertebrate feeders (Thorichthys speciesand C. robertsoni) and the herbivore-detritivore trophicgroup (Vieja species). High niche overlap among congeneric species (Thorichthys and Vieja species) suggeststhat phylogenetic niche conservatism maintains similarfeeding ecology within clades, and our analyses revealed that consumption of some prey items had astrong phylogenetic signal. Niche overlaps higher thanor similar to randomized simulations in these assemblages did not support expectations for trophic nichepartitioning among co-occurring cichlids. This wassomewhat surprising because sampling took place atthe height of the dry season, the period during wh
Feeding ecology and ecomorphology of cichlid assemblages in a large Mesoamerican river delta Allison A. Pease & Manuel Mendoza-Carranza& Kirk O. Winemiller Received: 17 August 2017/Acce
Trophic ecomorphology of cichlid fishes of Selva Lacandona, Usumacinta, Mexico Miriam Soria-Barreto & Rocío Rodiles-Hernández & Kirk O.
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