Spatial heterogeneity in pH, body size and habitat size generates ecological opportunity in an evolutionary radiation.

Much of the biological diversity we see today is thought to be the product of evolutionary radiation, the rapid proliferation of species from a single ancestor into multiple discrete forms. Spatial heterogeneity in environmental variables has been proposed as creating the necessary ecological opportunity to stimulate evolutionary radiation. Nonetheless, the ecological mechanisms generating and maintaining diversity in spatially heterogeneous environments are not fully understood. The authors investigated the role of strong spatial heterogeneity in generating ecological opportunity in an evolutionary radiation of freshwater populations of the three-spined stickleback (Gasterosteus aculeatus L.) on the island of North Uist using a spatially explicit Bayesian model. The authors identified pH, loch surface area and body size as predictors of variance in the number of lateral plates that comprise anti-predator armour in G. aculeatus. An East-West gradient of pH, a product of the distinctive environment of North Uist, generates a robust selective environment facilitating G. aculeatus evolutionary radiation. Larger lochs were associated with atypical phenotypes, possibly related to larger population sizes and greater selection efficiency. An association between pH and lateral plate number is likely an effect of body size, with a positive relationship between body size and lateral plate number that is mediated by swimming efficiency in G. aculeatus.

Sex steroids in diploid and triploid gibel carp (Carassius gibelio) of both sexes in different phases of the reproductive cycle.

The changes in concentrations of 17ß-estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT) in the gonads and plasma of diploid and triploid gibel carp (Carassius gibelio) from the Siemianowka Reservoir, the Vistula River drainage were quantified and compared using an enzyme immunoassay. The phase of gonad maturity was based on histological analysis and the gonadosomatic index. All fish had properly developed gonads in the pre-spawning, spawning and late spawning phases of the reproductive cycle in the fish collected in April, June and October, respectively. Diploid and triploid females and males did not differ in mean GSI in all reproductive phases. In October, ovaries of most females contained vitellogenic oocytes, testes had large numbers of spermatozoa. The hormone concentrations in both tissues depended mainly on the reproductive phase, but not on ploidy. The patterns of changes in E2 concentrations was similar in females and males. In the pre-spawning phase, diploid and triploid females showed differences in the concentrations of 11-KT in gonads and plasma, and T in plasma. Diploid males differed in pattern of T concentrations in gonads and plasma, while all males showed a similar pattern of 11-KT plasma concentrations. Spermatozoa observed in triploid males suggest that they participate in reproduction. Gibel carps, regardless of ploidy, had an extended period of reproduction, which makes this invasive species a potentially greater threat to native ichthyofauna. The sex androgen concentrations that differed between 2 n and 3 n females could be physiological factors potentially contributing to the coexistence of gynogenetic C. gibelio females and sexual diploids.

Food resource partitioning between juvenile and mature weatherfish Misgurnus fossilis.

This study represents a description of the diet composition of one of the largest European cobitids, the weatherfish Misgurnus fossilis. Specimens were collected in a drainage canal, representing a typical habitat for weatherfish, and with gut content analysis conducted with regard to individual total length and maturity stage. Overall, the weatherfish diet mainly consisted of Copepoda, Cladocera, Ostracoda, Oligochaeta, Asellus aquaticus, Chironomidae and Coleoptera larvae, Gastropoda, and detritus. To evaluate size-related patterns of resource use, fish were assigned to two size classes, defined according to size at first maturation. ANOSIM analyses revealed major ontogenetic shifts in feeding strategy, which were related to size and maturity, with a significant ontogenetic shift in feeding pattern, marked by differences in the proportions of the main taxonomic groups of prey consumed. Copepoda and Cladocera dominated in the diet of small and immature individuals, while large weatherfish primarily fed on detritus. Similarly, cluster analysis of diet classified into these food types showed distinct two groups comprising juvenile and mature fish. The weatherfish is a food opportunist using all available resources, but spatially showed a change in feeding sites. Smaller and sexually immature individuals more often use prey caught in the water column and among macrophytes, while larger (sexually mature) individuals occupying the bottom, much more often use detritus as a food base.

Prolific pioneers and reserved settlers. Changes in the life-history of the western tubenose goby (Proterorhinus semilunaris) at different invasion stages.

The western tubenose goby is one of the most wide-spread invasive fish species in European freshwaters, though information of its life-history in relation to its invasion success is limited. We compared the reproductive traits, growth rate and condition of three populations that differed in their stage of invasion in its expanding range in the River Vistula: core - the oldest population established at the centre of the invasive range; intermediate - long established by downstream dispersal from the core area but continuously supplemented by drifting specimens; front - new population at the edge of the invasive range, upstream from the core area. Pronounced differences in life-history traits were found between the 'core' and the 'front' populations. The 'front' population displayed high investment in reproduction and had heavier gonads, higher fecundity, higher batch fecundity though smaller eggs than the 'core' population. The 'core' population was characterized by the lowest fecundity, the largest eggs, the highest condition after spawning, and the highest maximum age of males. The 'intermediate' population was intermediate between the 'front' and the 'core' populations regarding reproductive traits, but showed the highest growth rates. The life-history traits that varied most among populations were gonad weight, fecundity, gonado-somatic index, condition and growth in the first years of life. Inter-individual variability of life-history traits was lower in the front of the invasive range than in the core and intermediate area. The observed plasticity in life-history appears to favour production of large numbers of offspring in newly-colonised areas in the initial stages of invasion and at the edge of the expanding range. In longer-established populations, at the core of invasive range, a strategy for greater competitiveness under intra-specific competition appears to be favoured.

The role of detritivory as a feeding tactic in a harsh environment - a case study of weatherfish (Misgurnus fossilis).

The weatherfish (Misgurnus fossilis) is a species that is tolerant of unfavourable environmental conditions and can survive low dissolved oxygen concentrations and high water temperatures. Although this species occurs across almost the whole of Europe, and is protected in many countries, relatively little is known regarding its ecology. To determine the diet of weatherfish, 120 individuals from an artificial drainage canal in central Poland were collected in two seasons (spring and late summer) with contrasting abiotic condition (oxygen concentration, water temperature and transparency). Analysis of gut fullness showed that weatherfish consumed a greater quantity of food in spring (0.92 ± 0.90) compared with summer (0.20 ± 0.26). Contrary to other cobitid taxa, weatherfish fed actively during daytime in both seasons. An estimate of the importance of each dietary component indicated that the most important food categories were chironomids, copepods, Asellus aquaticus and detritus. SIMPER analysis indicated that these four categories together constituted over 65.8% of cumulative dissimilarity in the diet between seasons. Additionally, trophic niche breadth differed significantly between seasons. The study demonstrated that the weatherfish is an opportunistic feeder, consuming large quantities of detritus despite possessing a gut morphology that is atypical of a detritivore. The quantity of detritus in the gut of weatherfish was positively associated with fish total length and varied seasonally, with a greater quantity of detritus in the diet in late summer. These results demonstrate the importance of detritus as a source of energy, particularly during periods of scarcity of alternative prey categories.

The response of cucumber plants (Cucumis sativus L.) to the application of PCB-contaminated sewage sludge and urban sediment.

BACKGROUND: The increasing production of sewage sludge (SS) engenders the problem of its responsible utilization and disposal. Likewise, urban sediments (SED) are deposited at the bottom of urban reservoirs and sedimentation ponds, and these require periodical dredging and utilization. However, while the SS and SED deposits often contain nutrients such as nitrogen and phosphorus; however, they also contain a variety of hazardous compounds including heavy metals, Persistent Organic Pollutants (POPs) and microbial pollutants. Fortunately, some species of Cucurbitaceae can accumulate high levels of POPs, such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB), in their tissues. METHODS: SS was collected from the Lodz Municipal Wastewater Treatment Plant and SED from the Sokolówka Sequential Biofiltration System. The SS and SED samples were added to soil in flower pots at three concentrations (1.8 g, 5.4 g and 10.8 g per flower pot), and one pot was left as an unamended control (C). Soil PCB concentrations were determined before cucumber planting, and after five weeks of growth. Also, total soluble protein, total chlorophyll content, chlorophyll a/b ratio and degree of lipid peroxidation (TBARS) were examined in the leaves of the cucumber plants (Cucumis sativus L.) cv. Cezar after five weeks. Antioxidative response was assessed by ascorbate peroxidase (APx) and catalase (CAT) assay. RESULTS: The initial PCB concentration in soil after application of SS or SED was dependent on the applied dose. After five weeks, PCB concentration fell significantly for all samples and confirmed that the dose of SS/SED had a strong effect. Soil remediation was found to be more effective after SS application. Total soluble protein content in the cucumber leaf tissues was dependent on both the type and the dose of the applied amendments, and increased with greater SS doses in the soil. The total chlorophyll content remained unchanged, and the chlorophyll a/b ratio was slightly elevated only after the application of the highest SS and SED dose. The use of SS and SED did not significantly affect TBARS content. APx activity fell after SS or SED application; however, CAT activity tended to increase, but only in the leaves of plants grown in SS-amended soil. DISCUSSION: The cultivation of cucumber plants reduces PCB concentration in soil amended with SS or SED; however, this effect is more evident in the case of SS. SS application also induced more intensive changes in the activity of enzymes engaged in antioxidative response and oxidative stress markers in plant tissues than SED. The levels of PCB in the SS may have triggered a more severe imbalance between pro- and antioxidative reactions in plants. Cucumber plants appear to be resistant to the presence of toxic substances in SS and SED, and the addition of SS and SED not only acts as a fertilizer, but also protects against accelerated aging.

Evidence of the sterility of allotetraploid Cobitis loaches (Teleostei, Cobitidae) using testes ultrastructure.

The diploid-polyploid populations of Cobitis distributed in Poland are usually composed of the spined loach Cobitis taenia or, less often, the Danubian loach C. elongatoides and their triploid (females) and tetraploid hybrids (females and males). The aim of this study was to determine whether tetraploid males participate in the reproduction process by analyzing their testis ultrastructure and the process of spermatogenesis in comparison with diploid males of both parental species. Tetraploid loaches were obtained from three different diploid-polyploid populations distributed in Poland. The structure of Cobitis testes are typical for most Teleostei fish with cystic-type spermatogenesis. The successive stages of developing germ cells are enclosed within cysts formed by the Sertoli cells. This paper morphologically describes the different germ cell stages of spermatogenesis (spermatogonia, spermatocytes, spermatids, and spermatozoa) of C. taenia and C. elongatoides and provides a pioneering ultrastructural analysis of tetraploid Cobitis testes which reveals their unusual structure for the first time. Thus, cysts with normal spermatogonia and spermatocytes (pachyten or leptoten stages) containing synaptonemal complexes were present and no spermatids or spermatozoa were observed. Moreover, in contrast to previously analyzed diploid species, single cells or all of the cells within the cysts displayed chromatin condensation and/or chromatin fragmentation. The obtained results clearly demonstrated that tetraploid males are sterile and diploids are fertile and are the only sperm donors in the reproduction processes of diploid-polyploid Cobitis populations.

Ephemera danica (Ephemeroptera: Ephemeridae) As a Resource for Two Commensals: Ciliated Protozoans (Sessilida) and Chironomids (Diptera).

The distribution and coexistence of two unrelated commensals, the chironomid Epoicocladius ephemerae (Kieffer 1924) and ciliate Carchesium polypinum L. 1758, on one host species, Ephemera danica Muller 1764, sampled in two small lowland rivers in 2009, 2010 and 2011, were investigated. We analyzed 288 mayfly specimens from the Bzura River and 101 from the Mroga River. The number of commensals on a single mayfly specimen varied between 0 and 18 chironomids, and from 0 to 46 colonies of ciliates. Prevalences were >48% for chironomids and ∼30% for ciliates, whereas mean intensities were low (4.01±6.04 commensals on one host). The spatial distribution of each commensal species was investigated on different parts of the host body. Neither chironomids nor ciliates infected the whole mayfly body. The co-occurrence of these two commensals was not random and showed a negative association. Chironomids were most frequent on two or three parts of the body (two parts of the abdomen, with gills and without gills, and legs), whereas ciliates were found on two parts (the whole abdomen). Coexistence of the two commensal species led to partitioning of resources that was host body size dependent: small mayflies (optimal size 11.63 mm) were primarily settled by ciliated protozoans while larger specimens (optimal size 28.77 mm) were settled by chironomids.

Population-specific responses to an invasive species.

Predicting the impacts of non-native species remains a challenge. As populations of a species are genetically and phenotypically variable, the impact of non-native species on local taxa could crucially depend on population-specific traits and adaptations of both native and non-native species. Bitterling fishes are brood parasites of unionid mussels and unionid mussels produce larvae that parasitize fishes. We used common garden experiments to measure three key elements in the bitterling-mussel association among two populations of an invasive mussel (Anodonta woodiana) and four populations of European bitterling (Rhodeus amarus). The impact of the invasive mussel varied between geographically distinct R. amarus lineages and between local populations within lineages. The capacity of parasitic larvae of the invasive mussel to exploit R. amarus was higher in a Danubian than in a Baltic R. amarus lineage and in allopatric than in sympatric R. amarus populations. Maladaptive oviposition by R. amarus into A. woodiana varied among populations, with significant population-specific consequences for R. amarus recruitment. We suggest that variation in coevolutionary states may predispose different populations to divergent responses. Given that coevolutionary relationships are ubiquitous, population-specific attributes of invasive and native populations may play a critical role in the outcome of invasion. We argue for a shift from a species-centred to population-centred perspective of the impacts of invasions.

The role of calcium and predation on plate morph evolution in the three-spined stickleback (Gasterosteus aculeatus).

While the genetic basis to plate morph evolution of the three-spined stickleback (Gasterosteus aculeatus) is well described, the environmental variables that select for different plate and spine morphs are incompletely understood. Using replicate populations of three-spined sticklebacks on North Uist, Scotland, we previously investigated the role of predation pressure and calcium limitation on the adaptive evolution of stickleback morphology and behavior. While dissolved calcium proved a significant predictor of plate and spine morph, predator abundance did not. Ecol. Evol., xxx, 2014 and xxx performed a comparable analysis to our own to address the same question. They failed to detect a significant effect of dissolved calcium on morphological evolution, but did establish a significant effect of predation; albeit in the opposite direction to their prediction.

Ecological causes of morphological evolution in the three-spined stickleback.

The central assumption of evolutionary theory is that natural selection drives the adaptation of populations to local environmental conditions, resulting in the evolution of adaptive phenotypes. The three-spined stickleback (Gasterosteus aculeatus) displays remarkable phenotypic variation, offering an unusually tractable model for understanding the ecological mechanisms underpinning adaptive evolutionary change. Using populations on North Uist, Scotland we investigated the role of predation pressure and calcium limitation on the adaptive evolution of stickleback morphology and behavior. Dissolved calcium was a significant predictor of plate and spine morph, while predator abundance was not. Stickleback latency to emerge from a refuge varied with morph, with populations with highly reduced plates and spines and high predation risk less bold. Our findings support strong directional selection in three-spined stickleback evolution, driven by multiple selective agents.

Feeding ecology of Cobitis paludica and Cobitis calderoni in Central Spain.

In total, 253 specimens of Cobitis paludica and 163 Cobitis calderoni were collected in the Lozoya River (Madrid, Spain) in April, May, July, September and December 1990. Both species showed high percentages of empty guts in all months. C. paludica fed mainly on detritus and invertebrates while Cobitis calderoni fed on invertebrates and unicellular algae. Preferred prey items were the larvae of Dipterans (Chironomidae, Simuliidae) and micro crustaceans, with Ephemeroptera (Caenis) in summer. Cobitis calderoni fed on the most abundant prey except in April and July, when it selected invertebrates. C. paludica selected invertebrates throughout all the months. Diet overlapping (Horn's Index) was complete except in September, when the abundance of invertebrates in both diets was similar. For the remaining months, food type (invertebrates, unicellular algae and detritus) abundance differed, minimizing the interspecific competition.

Feeding activity of spined loach Cobitis sp. in Lake Lucien, Poland.

The feeding activity of spined loach Cobitis sp. was studied in post-glacial ribbon Lake Lucien, Central Poland, during three 24 hrs periods in May, August and September. Samples were taken every 4 hrs and 8 to 18 (mode 10) specimens were caught on each sampling occasion. A total of 233 fish (37.3-107.6 mm TL) gut contents were examined. Six main food components (Cladocera, Chironomidae (larvae and pupae), Copepoda, Ostracoda, other macroinvertebrates and detritus) were used by the fish. Precise identification of gut contents showed that spined loach consumed large numbers of food items (from 31 to 39). Nevertheless standardised form of Levin's and Shannon-Wiener's indices revealed a rather narrow food niche, which was a result of unequal proportions of food items in gut contents and domination of few prey categories. Spined loach fed mostly from post-dusk to dawn and achieved maximum gut fullness in the morning (4.00-8.00). This nocturnal feeding pattern was consistent throughout all sampling occasions, but there was some discrepancy concerning 12.00 hours in spring and summer. Due to this, early morning activity can not be excluded. Prey selection indices indicated that spined loach preferentially consumed some small size chironomids: Tanytarsus, Cladotanytarsus, Dicrotendipes and avoided larger ones (Glyptotendipes, Stictochironomus).

Microhabitat preferences of spined loach, Cobitis sp. in the Grabia River--multivariation approach.

The pattern of microhabitat preferences of spined loach was examined in a natural, unpolluted lowland river. This fish co-occurred with 9 other species but non-random association was noted only with Ukrainian Lamprey, the most abundant species in the studied fish community. Spined loach was distributed only in areas adjacent to river banks. Microhabitat variables configuration available for the examined fish was represented by three axes obtained by principal component analysis. The presence/absence distribution pattern of spined loach was negatively dependent on the abundance of gravel and pebbles (component 1) and positively related to low velocity (component 3). The abundance of coarse sand (component 2) had no effect on the spined loach distribution pattern and fish randomly used this type of microhabitat. Although that substratum particle size plays an important role in spined loach distribution, in the natural environment this fish realised its microhabitat preferences by the avoidance of unfavourable configuration ofmicrohabitat variables such as high velocity and coarse-grained substrata (gravel and pebbles).

Growth and reproductive biology of loaches Cobitis sp. in Lake Lucien, Poland.

Five age-classes and their corresponding average body lengths of loaches from Lake Lucien were determined by the Bhattacharya method. The maximum observed length was 112 mm for females and 91 mm for males. The von Bertalanffy equation defining growth pattern was L(T) = 116 (1-exp (-0.401(t+0.02. Body length distribution of females and males differed significantly (chi2 = 91.295; df=9; P<0.00). Sex ratio showed the dominance of females in the studied population (M:F = 1:1.75; chi2 =18.00; P<0.01). Females were sexually mature at 56 mm TL and males at 52 mm TL. Female gonad weight increased with body size. The frequency distribution of egg diameters revealed 3 groups of oocytes. The average absolute fecundity was 2180 eggs and ranged from 418 to 6800 per gonad. The number of the largest oocytes (>0.6 mm in diameter) ranged from 208 to 975 (average 501) and was used to estimate fecundity at the moment of spawning. Both fecundity measures are related to body length of females their regression lines were parallel and did not differ in the coefficient of slope. The gonadosomatic index value, as an approximate measure of reproductive effort, was rather small (average IGS = 10.44 ranged from 5.12 to 17.88).