Introgressive hybridization erodes morphological divergence between lentic and lotic habitats in an endangered minnow

Introgressive hybridization may erode phenotypic divergence along environmental gradients, collapsing locally adapted populations into a hybrid swarm. Alternatively, introgression may promote phenotypic divergence by providing variation on which natural selection can act. In freshwater fishes, water flow often selects for divergent morphological traits in lake versus stream habitats. We tested the effects of introgression on lake–stream morphological divergence in the minnow Owens Tui Chub (Siphateles bicolor snyderi), which has been rendered endangered by introgession from the introduced Lahontan Tui Chub (Siphateles bicolor obesa). Using geometric morphometric analysis of 457 individual Tui Chub from thirteen populations, we found that both native and introgressing parent taxa exhibited divergent body and caudal fin shapes in lake versus stream habitats, but their trajectories of divergence were distinct. In contrast, introgressed populations exhibited intermediate body and caudal fin shapes that were not differentiated by habitat type, indicating that introgression has eroded phenotypic divergence along the lentic–lotic gradient throughout the historic range of the Owens Tui Chub. Individuals within hybrid populations were less morphologically variable than those within parent populations, suggesting hybrid adaptation to selective agents other than water flow or loss of variance by drift.     

The lentic and lotic characteristics of habitats determine the distribution of benthic macroinvertebrates in Mediterranean rivers

1. The importance of flow‐related factors to benthic organisms, as well as the role of habitat conditions in shaping aquatic communities during low‐flow periods, have been recognised. Despite this, the preferences of macroinvertebrates to the ratio of lentic to lotic habitats at the reach scale have not been accurately quantified in most instances.
2. Aquatic invertebrates and habitat features in a range of temporary rivers in Sardinia were investigated. The investigation focused on the flow‐related characteristics that contribute to defining the lentic–lotic condition of the river reaches. The relation of habitat features to benthic taxa distributions was assessed using multidimensional scaling. The main aim of the paper was to quantify the responses of taxa to the different lentic and lotic habitat conditions by applying hierarchical logistic regressions. Finally, taxon optima were aligned along the lentic–lotic gradient and the responses of different taxonomic groups compared.
3. Unbroken waves and imperceptible flow were correlated with benthic taxa variability, suggesting local hydraulics and turbulence have a major role in regulating community composition. The overall lentic–lotic character of the river reaches was also clearly related to the benthic taxa distribution. More than 80% of taxa were significantly related to the lentic–lotic gradient, and an asymmetrical response curve was the predominant model.
4. Benthic groups showed taxon optima clustered in different ranges of the lentic–lotic gradient. Odonata, Coleoptera, Hemiptera, and Mollusca preferred clearly lentic conditions. Diptera mainly ranged on the lotic side of the gradient, while Trichoptera were relatively uniformly distributed across the gradient. Ephemeroptera taxa clustered in intermediate lentic–lotic conditions, with two species preferring extremely lentic habitats. In general, optima converged at intermediate and extremely lentic conditions, presumably due, respectively, to the coexistence of different lentic and lotic features and to the highly diverse environmental characteristics under extremely lentic situations.
5. These results support the conclusion that dissimilar ecological factors act on benthic taxa along the lentic–lotic range and species favouring different lentic–lotic conditions are subjected to pressures of different nature. This should not be ignored when defining species preferences and studying community structure or relationships between species in Mediterranean rivers, which cyclically vary their habitat composition. In addition, the uneven distribution of optima of different groups along the lentic–lotic gradient might affect macroinvertebrate metrics when assessing ecological status or establishing reference conditions under variable climatic conditions.

     

Anti-predator defence drives parallel morphological evolution in flea beetles

Complex morphological or functional traits are frequently considered evolutionarily unique and hence useful for taxonomic classification. Flea beetles (Alticinae) are characterized by an extraordinary jumping apparatus in the usually greatly expanded femur of their hind legs that separates them from the related Galerucinae. Here, we examine the evolution of this trait using phylogenetic analysis and a time-calibrated tree from mitochondrial (rrnL and cox1) and nuclear (small subunits and large subunits) genes, as well as morphometrics of femora using elliptic Fourier analysis. The phylogeny strongly supports multiple independent origins of the metafemoral spring and therefore rejects the monophyly of Alticinae, as defined by this trait. Geometric outline analysis of femora shows the great plasticity of this structure and its correlation with the type and diversity of the metafemoral springs. The recognition of convergence in jumping apparatus now resolves the long-standing difficulties of Galerucinae-Alticinae classification, and cautions against the value of trait complexity as a measure of taxonomic significance. The lineage also shows accelerated species diversification rates relative to other leaf beetles, which may be promoted by the same ecological factors that also favour the repeated evolution of jumping as an anti-predation mechanism.     

Effect of age‐based and environment‐based cues on reproductive investment in Gambusia affinis

We examined the multivariate life‐history trajectories of age 0 and age 1 female Gambusia affinis to determine relative effects of age‐based and environment‐based cues on reproductive investment. Age 0 females decreased reproductive investment prior to the onset of fall and winter months, while age 1 females increased reproductive investment as the summer progressed. The reproductive restraint and terminal investment patterns exhibited by age 0 and age 1 females, respectively, were consistent with the predictions from the cost of reproduction hypothesis. Age 0 females responded to environment‐based cues, decreasing reproductive investment to increase the probability of overwinter survival and subsequent reproductive opportunities in the following summer. Age 1 females responded to age‐based cues, or the proximity of death, increasing investment to current reproduction as future reproductive opportunities decreased late in life. Thus, individuals use multiple cues to determine the level of reproductive investment, and the response to each cue is dependent on the age of an individual.     

Annual reproductive cycle and rate of the spermatogenic process in male mosquitofish <Emphasis Type="Italic">Gambusia affinis</Emphasis>

The present study investigates the relationship between the annual cycle of testicular development and external environment and the rate of spermatogenesis in the mosquitofish Gambusia affinis based on histological observations of testes. The annual reproductive cycle of the mosquitofish was divided into two periods, i.e., the spermatogenic period (May–October) and resting period (October–April). In the spermatogenic period, the transition from spermatogonia to spermatocytes begins and meiosis actively progresses. In the resting period, the transition from spermatogonia to spermatocytes ceases, meiosis of spermatocytes that already shifted by this period gradually progresses, and a considerable number of sperm balls are produced. Onset of spermatogenesis seems to be related to both a rise in water temperature and a prolonged photoperiod. 5-bromo-2-deoxyuridine (BrdU) was a useful in vivo marker of DNA synthesizing spermatogenic cells. The results of immunohistochemical detection of injected BrdU indicated that 5 days are needed for the conversion of spermatocytes to spermatids, 5 days for spermatids to spermatozoa, and 10 days for spermatozoa to sperm balls.     

Shared and unique features of morphological differentiation between predator regimes in Gambusia caymanensis

When multiple groups of organisms experience similar environmental gradients, their patterns of differentiation might exhibit both shared and unique features. Here, we investigated the relative importance of three factors in generating body shape variation in a livebearing fish, Gambusia caymanensis, inhabiting the Cayman Islands: (i) shared patterns of divergent selection between predator regimes (presence/absence of piscivorous fish) driving replicated morphological differentiation, (ii) historical island effects yielding different morphologies across the three islands and (iii) unique effects of predation on morphological differentiation within each island. Shared effects of predation proved much more important than historical or unique effects. Populations coexisting with piscivorous fish exhibited larger caudal regions and smaller heads than conspecifics found in the absence of predatory fish. These results match a priori predictions, and mirror recent findings in a number of fish species, suggesting predation might often drive predictable morphological trends in disparate fishes. However, interestingly, the sexes achieved this morphological pattern through different means: head depth, caudal peduncle length and depth in males; head length, caudal peduncle depth in females. In G. caymanensis, we quantitatively confirmed that predation intensity represents a primary driver of body shape differentiation.     

Reproductive biology of the mosquitofish in a permanent natural lagoon in south-west Spain: two tactics for one species

Introduced Gambusia holbrooki in a natural lagoon of southern Spain consisted of two age groups: 1992 cohort, 7-11 months old and 1993 cohort, <4 months old. In the 1992 cohort, females grew even during the gestation period at about 0·30 mm day^-1. In the 1993 cohort, females displayed a high growth rate (0·55 mm day^-1) and reached reproductive size in a few weeks, but stopped growing when they matured. All the 1992 cohort reproduced from mid-May to mid-June, but only 50% of the 1993 cohort reproduced, from mid-August to mid-September. Reproducing females were significantly larger in the 1992 cohort (39·8 mm) than in the 1993 one (34·8 mm). The largest 1992 females cohort had reproduced previously; the 1993 cohort had not. The mean dry weight of intra-ovarian embryos decreased to a minimum immediately before birth. These metabolic costs represented 29·8 and 31·4% of the initial weights of the 1992 and 1993 embryos, respectively. Mean dry weight of full-term embryo was significantly higher in the 1992 cohort (0·80 ± 0·129 mg; 95% CL) than in the 1993 one (0·70 ± 0·086 mg; 95% CL). With more females in 1992, cohort fecundity was considerably higher (number of embryos=7151; 63%) than in the 1993 (4193; 37%) cohort. The population completed two generations each year (spring and summer). The spring stock grew slower than the summer one but continued to grow during the gestation period, reaching larger final lengths, with more synchronous reproduction and clearer evidence of a second reproductive event. Each reproductive stock displayed its own life-history characteristics, with significant differences between mean length of reproducing females, growth rate, mean brood size, offspring size, standard fecundity and minimum length at reproduction.     

Habitat availability does not explain the species richness patterns of European lentic and lotic freshwater animals

Aim In Europe, the relationships between species richness and latitude differ for lentic (standing water) and lotic (running water) species. Freshwater animals are highly dependent on suitable habitat, and thus the distribution of available habitat should strongly influence large‐scale patterns of species richness. We tested whether habitat availability can account for the differences in species richness patterns between European lentic and lotic freshwater animals. Location Europe. Methods We compiled occurrence data of 1959 lentic and 2445 lotic species as well as data on the amount of lentic and lotic habitats across 25 pre‐defined biogeographical regions of European freshwaters. We used the range of elevation of each region as a proxy for habitat diversity. We investigated the relationships between species richness, habitat availability and habitat diversity with univariate and multiple regression analyses. Results Species richness increased with habitat availability for lentic species but not for lotic species. Species richness increased with elevational range for lotic species but decreased for lentic species. For both groups, neither habitat availability nor diversity could account for previously reported latitudinal patterns in species richness. For lotic species, richness declined with latitude, whereas there was no relationship between habitat availability and latitude. For lentic species, richness showed a hump‐shaped relationship with latitude, whereas available habitat increased with latitude. Main conclusions Habitat availability and diversity are poor predictors of species richness of the European freshwater fauna across large scales. Our results indicate that the distributions of European freshwater animals are probably not in equilibrium and may still be influenced by history, namely the recurrent European glaciations and possible differences in post‐glacial recolonization. The distributions of lentic species appear to be closer to equilibrium than those of lotic species. This lends further support to the hypothesis that lentic species have a higher propensity for dispersal than lotic species.     

Morphometric variation in bluegill Lepomis macrochirus and green sunfish Lepomis cyanellus in lentic and lotic systems

Bluegill Lepomis macrochirus and green sunfish Lepomis cyanellus were examined using geometric morphometrics to evaluate the variation in morphology between fishes that reside in lentic (e.g. lakes) and lotic (e.g. streams) ecosystems. Live fishes were collected from reservoirs and rivers in central Indiana, while additional fishes were sampled from museum collections at Ball State University and the Illinois Natural History Survey. Male and female L. macrochirus and female L. cyanellus from lentic systems display a deeper body than those from lotic systems, while no differences were found in male L. cyanellus morphometry. A deeper body promotes greater manoeuverability, typically desirable in lentic systems. In contrast, the more streamlined body of the fishes found in lotic systems reduces drag as it contends with flowing water, ultimately maximizing energy efficiency. The absence of morphological differences, such as those found in male L. cyanellus, may be caused by fish occupying both lentic and lotic systems, from the population not having been present in the body of water long enough to display any adaptations, or from a lack of statistical power caused by the small sample size.     

Ecological characterization of the odonatofauna in lotic and lentic waters of northeast Algeria

The purpose of this paper is to determine the Odonata fauna structure and composition in Bejaia’s wetlands, which have been poorly sampled until now. This paper is a report of a pioneer study of dragonflies in the Bejaia area in northeastern Algeria, with the aim to improve the knowledge of the Odonata taxa present in this vast territory, which covers 3268 km². This region is of major importance, and contains Wadi Soummam which is classified by the Ramsar Convention as of international importance. In addition, Lake Mezaia is included in the Gouraya National Park, and the area also contains high mountain forest ponds, which are unknown to both the general public and the scientific community due to their remote location and poor accessibility. Despite the anthropogenic pressures on these wetlands, this study recorded 33 Odonata species, which represented 52% of the species known in Algeria. None were new to the country. The recorded species included two Maghrebian endemic taxa, namely Platycnemis subdilatata and Enallagma deserti.     

Unique evolutionary trajectories in repeated adaptation to hydrogen sulphide‐toxic habitats of a neotropical fish (Poecilia mexicana)

Replicated ecological gradients are prime systems to study processes of molecular evolution underlying ecological divergence. Here, we investigated the repeated adaptation of the neotropical fish Poecilia mexicana to habitats containing toxic hydrogen sulphide (H₂S) and compared two population pairs of sulphide‐adapted and ancestral fish by sequencing population pools of >200 individuals (Pool‐Seq). We inferred the evolutionary processes shaping divergence and tested the hypothesis of increase of parallelism from SNPs to molecular pathways. Coalescence analyses showed that the divergence occurred in the face of substantial bidirectional gene flow. Population divergence involved many short, widely dispersed regions across the genome. Analyses of allele frequency spectra suggest that differentiation at most loci was driven by divergent selection, followed by a selection‐mediated reduction of gene flow. Reconstructing allelic state changes suggested that selection acted mainly upon de novo mutations in the sulphide‐adapted populations. Using a corrected Jaccard index to quantify parallel evolution, we found a negligible proportion of statistically significant parallel evolution of J_corr = 0.0032 at the level of SNPs, divergent genome regions (J_corr = 0.0061) and genes therein (J_corr = 0.0091). At the level of metabolic pathways, the overlap was J_corr = 0.2545, indicating increasing parallelism with increasing level of biological integration. The majority of pathways contained positively selected genes in both sulphide populations. Hence, adaptation to sulphidic habitats necessitated adjustments throughout the genome. The largely unique evolutionary trajectories may be explained by a high proportion of de novo mutations driving the divergence. Our findings favour Gould's view that evolution is often the unrepeatable result of stochastic events with highly contingent effects.     

The robustness of geometric morphometrics in testing the morphological equivalence hypothesis among cichlid species from East African Great Lakes

As part of an ongoing broader investigation into whether similar morphologies among cichlid species from East African Great Lakes are due to common ancestry or convergent evolution, we used geometric morphometrics to quantitatively test the hyphothesis that Lake Tanganyika's Tropheus spp. is morphologically similar to Lake Malawi's Pseudotropheus spp. and Labeotropheus fuelleborni . Landmark-based techniques were used to investigate body shape variation and the results revealed highly significant differences among these genera with the exception of L. fuelleborni vs. Pseudotropheus ( Tropheops ) spp. An ordination of all specimens along the first two canonical variate (CV) axes indicated clear interlake separation, especially along the CV I axis, whereby Tropheus moori showed a dorsoventral expansion of the mid body section with a steeper forehead relative to Lake Malawi species. Pseudotropheus ( Maylandia ) zebra was discriminated from the rest primarily on the basis of its terminally positioned gape, which differed from the inferior subterminal gape that was prevalent in the other species. Thus, the present study reveals a pattern of parallel evolution between L. fuelleborni and Pseudotropheus ( Tropheops ) spp., but does not support an interlake convergent evolution hypothesis. Contrary to previous researchers' assertions, these results emphasize the robustness of geometric morphometrics when testing morphological equivalence hypothesis among cichlid species.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 1–9.     

Stasis and convergence characterize morphological evolution in eupolypod II ferns

Background and Aims

Patterns of morphological evolution at levels above family rank remain underexplored in the ferns. The present study seeks to address this gap through analysis of 79 morphological characters for 81 taxa, including representatives of all ten families of eupolypod II ferns. Recent molecular phylogenetic studies demonstrate that the evolution of the large eupolypod II clade (which includes nearly one-third of extant fern species) features unexpected patterns. The traditional ‘athyrioid’ ferns are scattered across the phylogeny despite their apparent morphological cohesiveness, and mixed among these seemingly conservative taxa are morphologically dissimilar groups that lack any obvious features uniting them with their relatives. Maximum-likelihood and maximum-parsimony character optimizations are used to determine characters that unite the seemingly disparate groups, and to test whether the polyphyly of the traditional athyrioid ferns is due to evolutionary stasis (symplesiomorphy) or convergent evolution. The major events in eupolypod II character evolution are reviewed, and character and character state concepts are reappraised, as a basis for further inquiries into fern morphology.

Methods

Characters were scored from the literature, live plants and herbarium specimens, and optimized using maximum-parsimony and maximum-likelihood, onto a highly supported topology derived from maximum-likelihood and Bayesian analysis of molecular data. Phylogenetic signal of characters were tested for using randomization methods and fitdiscrete.

Key Results

The majority of character state changes within the eupolypod II phylogeny occur at the family level or above. Relative branch lengths for the morphological data resemble those from molecular data and fit an ancient rapid radiation model (long branches subtended by very short backbone internodes), with few characters uniting the morphologically disparate clades. The traditional athyrioid ferns were circumscribed based upon a combination of symplesiomorphic and homoplastic characters. Petiole vasculature consisting of two bundles is ancestral for eupolypods II and a synapomorphy for eupolypods II under deltran optimization. Sori restricted to one side of the vein defines the recently recognized clade comprising Rhachidosoraceae through Aspleniaceae, and sori present on both sides of the vein is a synapomorphy for the Athyriaceae sensu stricto. The results indicate that a chromosome base number of x =41 is synapomorphic for all eupolypods, a clade that includes over two-thirds of extant fern species.

Conclusions

The integrated approach synthesizes morphological studies with current phylogenetic hypotheses and provides explicit statements of character evolution in the eupolypod II fern families. Strong character support is found for previously recognized clades, whereas few characters support previously unrecognized clades. Sorus position appears to be less complicated than previously hypothesized, and linear sori restricted to one side of the vein support the clade comprising Aspleniaceae, Diplaziopsidaceae, Hemidictyaceae and Rachidosoraceae – a lineage only recently identified. Despite x =41 being a frequent number among extant species, to our knowledge it has not previously been demonstrated as the ancestral state. This is the first synapomorphy proposed for the eupolypod clade, a lineage comprising 67 % of extant fern species. This study provides some of the first hypotheses of character evolution at the family level and above in light of recent phylogenetic results, and promotes further study in an area that remains open for original observation.     

Convergent evolution across the Australian continent: ecotype diversification drives morphological convergence in two distantly related clades of Australian frogs

Animals from different clades but subject to similar environments often evolve similar body shapes and physiological adaptations due to convergent evolution, but this has been rarely tested at the transcontinental level and across entire classes of animal. Australia's biome diversity, isolation and aridification history provide excellent opportunities for comparative analyses on broad‐scale macroevolutionary patterns. We collected morphological and environmental data on eighty‐four (98%) Australian hylid frog species and categorized them into ecotypes. Using a phylogenetic framework, we tested the hypothesis that frogs from the same ecotype display similar body shape patterns: (i) across all the Australian hylids, and (ii) through comparison with a similar previous study on 127 (97%) Australian myobatrachid species. Body size and shape variation did not follow a strong phylogenetic pattern and was not tightly correlated with environment, but there was a stronger association between morphotype and ecotype. Both arboreal and aquatic frogs had long limbs, whereas limbs of fossorial species were shorter. Other terrestrial species were convergent on the more typical frog body shape. We quantified the strength of morphological convergence at two levels: (i) between fossorial myobatrachid and hylid frogs, and (ii) in each ecomorph within the hylids. We found strong convergence within ecotypes, especially in fossorial species. Ecotypes were also reflected in physiological adaptations: both arboreal and cocooned fossorial frogs tend to have higher rates of evaporative water loss. Our results illustrate how adaptation to different ecological niches plays a crucial role in morphological evolution, boosting phenotypic diversity within a clade. Despite phylogenetic conservatism, morphological adaptation to repeatedly emerging new environments can erase the signature of ancestral morphotypes, resulting in phenotypic diversification and convergence both within and between diverse clades.     

Dopamine receptor agonist bromocriptine restrains the follicular development,hatchling success and puberty in Gambusia affinis

The present investigation was conducted to determine the influence of dopamine (DA) receptor agonist bromocriptine (BRO) on reproduction and onset of puberty in the viviparous fish Gambusia affinis. In the first experiment, the mean number of stage I and II follicles (previtellogenic) in 0.8 or 5 mg BRO treated fish did not show significant difference compared to those of experimental controls, whereas the mean number of stage III follicles were significantly lower in 5 mg BRO treated fish compared to experimental controls. However, treatment of 0.8 or 5 mg BRO resulted in significantly lower numbers of stage IV (early vitellogenic) and V (late vitellogenic) follicles compared to those of experimental controls. There was decrease in the percent occurrence of pregnancy and different stages of embryos in BRO treated fish compared with the experimental controls. Concomitant with this, sparsely distributed gonadotropin releasing hormone immunoreactive (GnRH‐ir) fibres were observed in the proximal pars distalis (PPD) region of the pituitary gland in BRO treated fish compared to those of dense accumulations of these fibres in the PPD region of the pituitary gland in experimental controls. In the second experiment, exposure of juveniles (25 DPH) to same doses of BRO for 45 days resulted in complete absence of vitellogenic follicles and presence of few GnRH‐ir fibres in 5 mg BRO treated juvenile in contrast to presence of vitellogenic follicles and dense aggregation of GnRH fibres in treatment controls. Overall, the results of the present investigation suggest that DA affects ovarian follicular and embryonic development and onset of puberty in viviparous species.     

Repeated modification of early limb morphogenesis programmes underlies the convergence of relative limb length in Anolis lizards

The independent evolution of similar morphologies has long been a subject of considerable interest to biologists. Does phenotypic convergence reflect the primacy of natural selection, or does development set the course of evolution by channelling variation in certain directions? Here, we examine the ontogenetic origins of relative limb length variation among Anolis lizard habitat specialists to address whether convergent phenotypes have arisen through convergent developmental trajectories. Despite the numerous developmental processes that could potentially contribute to variation in adult limb length, our analyses reveal that, in Anolis lizards, such variation is repeatedly the result of changes occurring very early in development, prior to formation of the cartilaginous long bone anlagen.     

Evidence for parallel ecological speciation in scincid lizards of the Eumeces skiltonianus species group (Squamata: Scincidae)

We identify instances of parallel morphological evolution in North American scincid lizards of the Eumeces skiltonianus species group and provide evidence that this system is consistent with a model of ecological speciation. The group consists of three putative species divided among two morphotypes, the small-bodied and striped E. skiltonianus and E. lagunensis versus the large-bodied and typically uniform-colored E. gilberti. Members of the group pass through markedly similar phenotypic stages during early development, but differ with respect to where terminal morphology occurs along the developmental sequence. The morphotypes also differ in habitat preference, with the large-bodied gilberti form generally inhabiting lower elevations and drier environments than the smaller, striped morphs. We inferred the phylogenetic relationships of 53 skiltonianus group populations using mtDNA sequence data from the ND4 protein-coding gene and three flanking tRNAs (900 bp total). Sampling encompassed nearly the entire geographic range of the group, and all currently recognized species and subspecies were included. Our results provide strong evidence for parallel origins of three clades characterized by the gilberti morphotype, two of which are nested within the more geographically widespread E. skiltonianus. Eumeces lagunensis was also nested among populations of E. skiltonianus. Comparative analyses using independent contrasts show that evolutionary changes in body size are correlated with differences in adult color pattern. The independently derived association of gilberti morphology with warm, arid environments suggests that phenotypic divergence is the result of adaptation to contrasting selection regimes. We provide evidence that body size was likely the target of natural selection, and that divergences in color pattern and mate recognition are probable secondary consequences of evolving large body size.     

Response of endangered Poeciliopsis occidentalis sonoriensis in the Río Yaqui drainage,Arizona, to introduced Gambusia affinis

Synopsis Potential coexistence of the native Yaqui topminnow, Poeciliopsis occidentalis sonoriensis, with introduced mosquitofish, Gambusia affinis, was examined in spring pools and streams in San Bernardino National Wildlife Refuge, southeastern Arizona. Poeciliopsis never exceeded 12% of total poeciliid numbers in a spring pool where Gambusia was present. Body size, fecundity and reproductive effort of Poeciliopsis were significantly higher in this pool than in similar spring pools where Gambusia was absent. Where Poeciliopsis and Gambusia were syntopic in a stream, numbers of Poeciliopsis declined over 1.7 years, until none were collected. Poeciliopsis then increased to > 60% of total poeciliid numbers following flash flooding. Persistence of Poeciliopsis with Gambusia in the spring pool appeared to be a result of compensatory increase in reproductive output, while in the stream it was associated with recurrent flash flooding and a uniform temperature springhead which provided refuge.     

Morphological variations of an invasive cyprinid fish (Carassius gibelio) in lentic and lotic environments inferred from the body,otolith, and scale shapes

This study investigated the morphological variation of gibel carp Carassius gibelio collected from various water bodies in Türkiye. The fish samples were obtained from three dams (Karacaören-1, Karakaya, and Keban), two natural lakes (Beyşehir and Suğla), and a river (the Tigris River). The dimorphism in body shape was examined with geometric morphometrics, while elliptic Fourier analysis and shape indices were used to describe the variation in lapilli otoliths (hereafter “otoliths”) and scale shapes. The body of C. gibelio revealed higher variations, particularly in the body depth, snout length, caudal fin, and caudal peduncle, among different stations. Geometric morphometric analysis determined a streamlined body shape of C. gibelio in the Tigris River compared to other stations, while C. gibelio from the natural lakes had a deeper body shape. The body of C. gibelio exhibited a significant homogenous shape between the Beyşehir and Suğla lakes, providing the lowest Procrustes distance. The elliptic Fourier analysis revealed that the otolith shape varied significantly between all stations. However, the scale shape was remarkably similar among nearby areas such as Karacaören dam, Suğla, and Beyşehir lakes. These results evinced high degree of intra-population morphological variation in C. gibelio in response to prevailing environmental conditions that probably facilitate their successful establishment in a novel environment.