Predators and planariid competitors of the triclad Phagocata vitta (Dugés)

When Phagocata vitta, Crenobia alpina and Polycelis felina were exposed separately to each of seventeen potential invertebrate predators in the laboratory, only two stonefly species, Dinocras cephalotes and Perlodes microcephala, fed on the three triclad species, whilst the trichopteran Rhyacophila dorsalis ate the last two triclads. On exposing pairs of triclad species to D. cephalotes, significantly more P. felina than Ph. vitta were consumed, whereas similar numbers were eaten in each of the other two triclad combinations. Cannibalism and interspecific predation by triclad species were not observed. It is concluded that predation is unlikely to have a major influence in determining the observed distribution and abundance of triclad species in a Welsh study stream which harbours low numbers of effective predators.The de Wit model of competition was used to examine the competitive relationships between Ph. vitta, and C. alpina and P. felina, using chironomids or tubificid worms as food. In mixed cultures of Ph. vitta and P. felina fed on tubificids a stable equilibrium existed within the range of relative densities used in the experiments, whereas Ph. vitta was competitively superior to C. alpina in cultures fed on each of the food types, and to P. felina fed on chironomids. However, in theory, an equilibrium could occur when 10 or 6–7 times as many Ph. vitta as P. felina and C. alpina respectively are in the culture, when intraspecific rather than interspecific competition would become more important. Where the three triclad species coexist in the Welsh study stream, they are in similar numbers. This could imply that food is not limiting, with no consequent interspecific competition, or that the laboratory experiments were too simplistic to allow any interpretation of the field situation.     

The responses to current flow of two stream dwelling triclads,Crenobia alpina (Dana) and Polycelis felina (Dalyell)

Summary An apparatus is described which allows triclads to choose between the fast and slow regions of a stirred tank. In the absence of a stone substratum Crenobia alpina preferred or tolerated higher current speeds than Polycelis felina, this effect was enhanced when a stone substratum was added to the apparatus. These results indicate that the absence of Polycelis felina from the steep gradient regions of streams could be accounted for by its preference for slower micro-currents. Conversely the presence of Crenobia alpina in steep gradient regions could be accounted for by its preference for or tolerance to higher micro-currents.     

Distribution, ecology, mode of reproduction and karyology of freshwater planarians (Platyhelminthes; Turbellaria; Tricladida) in the springs of the central Pyrenees

The distribution, reproductive modality and karyology of populations of freshwater planarians were studied together with physico-chemical variables m 149 springs in the central Pyrenees Diversity was limited to four species (Dugesia (Dugesia) subtentaculata, Polycelis felina. Crenobia alpina and Phagocata vitta), already known from streams and lakes Planarians were found rarely (only a third of springs contain them), m low-moderate abundance, and any single spring did not harbour more than one species The distribution of potential predators and preys among the springs sampled was fairly uniform So. we assume that whereas predation is unlikely to influence triclad distribution, the oligotrophic character of these habitats may explain, through food shortage and ensuing interspecific competition, the presence of a single species in each spring Besides interspecific competition, the distribution of each species can also be influenced by particular abiotic parameters Temperature and current velocity appeared to be the dominant factors, the first separating C alpina from the rest of species, and the second favouring the presence of P felina in a large set of springs These factors also seem to determine planarian distribution in streams and rivers Other environmental factors such as calcium bicarbonated water (for D subtentaculata) and preference for karst systems (for Phagocata vitta) are of importance Some peculiarities of distribution, like the scarcity of C alpina in reophile habitats and the thermal tolerance of Phagocata vitta, may be due both to competition from P felina and to historical factors in the former and to morphological (presence of pigment) and ecological (epigean habits) features m the latter, respectively Karyological analyses demonstrated triploidy in all populations of D subtentaculata. a polyploid origin for C alpina and the finding in Phagocata vitta of a new polyploid series leading to the highest chromosome number in turbellarians (14n = 238) Furthermore, the basic chromosome number of C alpina (n = 21) and Phagocata vitta (n = 17) differs from those found in northern European populations (n = 7 in both, respectively) This suggests that under the specific names C alpina and Phagocata vitta more than one species actually occurs, this being a problem for further studies Whereas polyploidy has often been related to living in cold, harsh habitats, asexual reproduction has been linked to environments where biotic stress is low The preeminence of asexual reproduction (by fissiparity) and polyploid forms in freshwater planarians inhabiting the unproductive, biotically unsaturated springs of the central Pyrenees adds new evidence to strengthen such links     

Reproductive ecology of Dendrocoelum lacteum (Turbellaria) in a rapid stream in southern Sweden and comparisons with a lake population

Rapid streams in southern Sweden are often inhabited by the triclad Dendrocoelum lacteum. Outside Fennoscandia, this species is mainly restricted to lentic habitats. The normal food refuge for D. lacteum, the isopod Asellus aquaticus, is seldom found in the stream habitats, and probably the prey here is the amphipod Gammarus pulex. With respect to spatial and trophic niche components, it seems that D. lacteum has taken the place of Crenobia alpina in southern Sweden.Two parameters of reproduction, namely production of cocoons and of hatchlings, both peaked approximately one month later in a stream than in an adjacent lake. This difference was attributed to a low temperature regime in the stream. Number of hatchlings per cocoon and cocoon sterility were higher in the stream than in the lake. Similar cocoon and hatchling output per adult was found in the two habitats, indicating a similar reproductive effort for the two triclad populations. I suggest that D. lacteum, by virtue of its choice of microhabitat, viz., under stones, is not so vulnerable to the more severe stream environment.     

The occurrence of the freshwater isopod Heterias (Fritzianira) exul in the Lakes Region of Chile,with notes on the genus Heterias (Asellota: Janiridae)

Heterais exul, previously known from Brazil and Argentina, was collected from a number of lakes and streams in the Lakes Region of Chile (between Valdivia and Puerto Montt). It was found in a wide variety of habitats: on leaf litter, detritus, algae, rotting wood, emergent vegetation, and clean sandy bottoms. Heterias, Pseudasellus, and Fritzianira are placed in synonymy, but Fritzianira is maintained as a subgenus of Heterias because of its lack of an antenna) scale. The 3 Australian species of Heterias and H. exul are believed to have evolved from a common freshwater Gondwanaland ancestor.     

Distribution and diversity of the Syllidae (Annelida: Polychaeta) from the Mexican Gulf of Mexico and Caribbean

The objective of this study was to contribute to the knowledge of the syllids distributed in the eastern coasts of Mexico (Gulf of Mexico and Caribbean) taking into consideration their composition, distribution and diversity. Sampling was done at 77 stations including 49 in soft bottoms (terrigenous and carbonate sediments), and 28 in hard bottoms (coralline substrates) sampled in nine reef zones included in three reef systems (Veracruz, Campeche and Cozumel). In all 2084 individuals were collected (13.5% in soft sediments and 86.4% in coralline areas). Forty-five species were identified: 31 in soft bottoms and 38 in corals, with 21 species common to both types of environments. In soft bottoms, the highest species richness and diversity were found in the Carbonate Zone, while syllids were uncommon in the Terrigenous Zone. In hard bottoms, the highest density, species richness and diversity values were found in the Veracruz Reef System, followed by the Campeche Bank and Cozumel Island Reef Systems. The dominant species in soft bottoms were Haplosyllis spongicola, Exogone lourei, Typosyllis cornuta and T. papillosus, whereas T. alosae, T. corallicola, T. cornuta and H. spongicola dominated in hard bottoms. The importance and success of the syllids in both soft bottoms and reef environments, particularly in those of the Gulf of Mexico is emphasized.     

Comparative pollen morphology of Turkish species of <Emphasis Type="Italic">Petrorhagia</Emphasis> (Caryophyllaceae) and its systematic implications

Pollen morphology of 10 taxa from Turkey, four of them endemic, belonging to the genus Petrorhagia (Caryophyllaceae), P. alpina subsp. alpina, P. alpina subsp. olympica, P. cretica, P. dubia, P. hispidula, P. lycica, P. pamphylica, P. peroninii, P. prolifera and P. saxifraga, has been investigated using light (LM) and scanning electron (SEM) microscopy. Pollen morphology differences among these taxa have been determined. The pollen type of investigated taxa is polyporate (12–22-porate), sphaeroidal, the exine exhibits a tectate structure and a microechinate ornamentation. Petrorhagia alpina subsp. alpina has the smallest pollen grain diameter (18.57 μm) and P. dubia the largest one (37.80 μm). The number of pores ranges from 12 (in P. dubia and P. saxifraga) to 22 (in P. alpina subsp. alpina and P. alpina subsp. olympica and P. hispidula) with a minimum pore diameter of 2.37 μm in P. alpina subsp. alpina and a maximum pore diameter of 4.23 μm in P. peroninii. The exine thickness ranges from 1.73 μm in P. saxifraga to 3.78 μm in P. pamphylica. In this study, the systematic implications are discussed in the light of palynological results.     

Continuing dispersal of freshwater triclads (Platyhelminthes; Turbellaria) in Britain with particular reference to lakes

1. A survey of lakes in Anglesey and Snowdonia, Wales, in the summer of 1997 recorded changes in the triclad fauna which had occurred since earlier studies in the 1950s and in 1973. Two native species, Polycelis tenuis and Dugesia polychroa, and two immigrants, Planaria torva and especially Dugesia tigrina, have increased their range. The triclad fauna has remained unchanged with time in eleven out of sixteen lakes in Snowdonia, in contrast to only one out of fourteen lakes on Anglesey. This supports the hypothesis produced in the 1950s, that the triclad fauna of the ion-poor, unproductive lakes in Snowdonia would change little with time, being maintained by ecological interactions, whereas the ion-rich, productive lakes on Anglesey, from which native Dugesia spp. and Dendrocoelum lacteum are historically absent, would increase in triclad diversity. 2. An examination of national records for the distribution of D. tigrina and Pl. torva indicated their continuing dispersal in both still and running waters in mainland Britain, with the former species having the greater frequency of occurrence. 3. The reasons for this may be that D. tigrina is (a) more easily dispersed, (b) a more opportunistic, catholic feeder, (c) a more vigorous competitor, (d) able to reproduce asexually and (e) able to prey to some extent on other triclad species, as shown in the laboratory but not yet confirmed in the field. The absence of D. tigrina and Pl. torva from unproductive lakes may be explained in terms of low temperature and feeding mode, and a low standing crop of gastropods, respectively. 4. Seven surveys (1961–1997) of the triclad fauna (six species) of Colemere, England, revealed that D. tigrina was confined to one small area of the littoral zone until the mid-1980s, after which it spread fairly rapidly to occupy the entire shore by 1997. Its expansion has been to the detriment of all the native species, particularly P. tenuis, except Dd. lacteum. The possible extinction of Pl. torva may be linked to a numerical reduction in snails, particularly Potamopyrgus jenkinsi. 5. Dugesia tigrina has an adverse effect on the native triclad fauna in lakes, particularly when only a few species are present. This has been explained in terms of the availability of a wider variety of food. The presence of a larger number of triclad species denies the immigrant food items, particularly crustaceans and snails, the food refuges of Dd. lacteum and Dugesia spp., respectively. However, the long-term study of Colemere has shown that more diverse triclad faunas may also be vulnerable to this immigrant. The effect of Pl. torva on native triclads remains uncertain.     

The comparative reproductive styles of two closely related African minnows (Pseadobarbus afer andP. asper) inhabiting two different sections of the Gamtoos River system

Synopsis Two species of a monophyletic lineage of flexible-rayed redfin minnows,Pseudobarbus afer andP. asper, were studied to establish if there were any significant differences in their reproductive styles. They are sister species with few morphological or meristic differences.P. afer andP. asper are open substrate benthic spawners on coarse bottoms (rocks) and non-guarders of non-adhesive eggs. Their young are photophobic as free embryos. Riverine spawning sites indicated a conservative tendency and represented a phylogenetic constraint as compared to the more variable attributes, such as egg size, which were under environmental control within the limits expressed by the genotype. The combination of life-history attributes, gonadosomatic index, fecundity, egg size, investment per clutch, number of clutches per season and reproductive lifespan was found to be different forP. afer andP. asper. P. asper is derived and atypical of otherPseudobarbus species studied to date. Differences betweenP. afer andP. asper are directly related to the two distinct environments inhabited by these species-coastal Cape Fold Belt mountain streams and the inland Karoo streams of the Gamtoos River system.P. asper may have reverted, by juvenilization, to a more altricial form to survive the turbid, intermittent Karoo stream.     

Notes on the lichen genus Lepraria from maritime (South Shetlands) and continental (Schirmacher and Bunger Oases) Antarctica

Material of the genus Lepraria from maritime and continental Antarctica collected in 1986–2007 was studied. Four species were distinguished, L. alpina, L. caerulescens, L. straminea and one putative new taxon provisionally called Lepraria sp. AO. L. caerulescens is tentatively resurrected from the synonyms of L. alpina for the chemotype with atranorin and angardianic/roccellic acid. Lepraria sp. AO is characterized by its granular thallus similar to other members of the L. neglecta group and the presence of two fatty acids, so far unidentified and not known from other members of the genus. Morphological and chemical diagnostic characters of all taxa, their distribution and ecological features are discussed. An updated key for identification of all Antarctic species is provided.     

Redescription of Piguetiella denticulata (Annelida, Clitellata, Naididae) from Japan and the Russian Far East, with a description of the genital organs in the species

A naidid oligochaete, Piguetiella denticulata Liang and Xie (Invertebrates of Wuling Mountains area, Southwestern China, pp 383–394, 1997), is redescribed based on new material from Japan and the Russian Far East, and its generic position is verified by an examination of the reproductive organs. P. denticulata closely resembles P. michiganensis in lacking eyes and dorsal hair chaetae, but it is distinguished from the latter by having intermediate teeth on both its dorsal and ventral crotchets. In Japan, P. denticulata is widely distributed and often abundant in mountain streams with sandy and gravelly bottoms.     

Assemblage structure of stream fishes in the Western Ghats (India)

Macro and microhabitat analyses were applied to characterise the fish assemblage structure in 10 streams of the Western Ghat mountains of Peninsular India. Macrohabitat features, such as channel gradient, stream depth, stream width, riparian cover, instream cover, habitat types and substrates, were used. Microhabitat requirements of the abundant cyprinids (35 species) were also analysed. Macrohabitat assessment indicated that a high habitat diversity was associated with a high species diversity, and that habitat volume was a major determining factor for species diversity and abundance. In all streams, cyprinids were the dominant group in the assemblage and almost all cyprinids were confined to pools with a varied habitat diversity. Riffle dwelling species included ancient forms such as Glyptothorax madraspatnum, G. trewasae and Homaloptera santhamparaiensis. Suitable microhabitats for dominant cyprinid species were pools and riffle edges. Big-sized barbs and mahseers such as Hypselobarbus dobsoni, H. curmuca, H. dubius, Labeo calbasu, Puntius sarana, Tor khudree and Tor khudree malabaricus were confined to deep pools with a large area. Smaller Puntius species like P. fasciatus, P. melanampyx, P. narayani, P. sophore, P. ticto and P. vittatus lived in shallow backwater pools and pools with low flow. Species like P. arulius tambiraparniei, P. amphibius, P. bimaculatus and P. filamentosus were found towards shallow pools with moderate flow. Surface-dwelling species such as Danio aequipinnatus, Rasbora daniconius, Salmostoma spp. and Barilius spp. preferred deepwater habitats with high flow. Habitat-based multivariate analysis revealed four guilds: surface dwellers, column dwellers, generalized bottom dwellers and specialized bottom dwellers.     

New species and records of saprophytic ascomycetes (Myxotrichaceae) from decaying logs in the boreal forest

Decayed wood from fallen white spruce (Picea glauca) and trembling aspen (Populus tremuloides) collected in northeastern Alberta, Canada, was the source of new isolates of species in the ascomycete generaGymnostellatospora andPseudogymnoascus. In addition to new reports ofG. japonica, G. frigida andP. roseus, two new species are described.Gymnostellatospora canadensis sp. nov. resemblesG. japonica but differs in producing brown ascomata and in the formation of an arthroconidial anamorph.Gymnostellatospora subnuda sp. nov. is distinct in lacking differentiated peridial hyphae.Gymnostellatospora alpina was not found in decayed wood but is reviewed based on extralimital material. A dichtomous key to the five species ofGymnostellatospora is provided.     

Observations on the comparative ecology of lake-dwelling triclads in southern Sweden,Finland and northern Britain

Summary There are more lake-dwelling species of triclad in northerm Britain (10) than in southern Sweden (7) and the distribution of some differ in the two countries over approximately comparable types of lake. Dendrocoelum lacteum (Müller) occurs in a wide range of lake types in s. Sweden but is restricted to more productive lakes in n. Britain. Polycelis nigra (Müller) (absent from Sweden) has a similar, wide occurrence in Britain. Planaria torva (Müller) is more common in s. Sweden in lakes of all types but particularly in the less productive lakes. The Polycelis species P. tenuis (Ijima) and P. hepta E. H. and Y. Melander, also the Dugesia lugubris species complex show much the same distribution in both areas. Polycelis felina (Dalyell) does not occur in Sweden. The small nuber of Finnish lakes sampled confirm the data for s. Sweden. There is significant correlation between the total abundance of triclads and both the hardness and dissolved matter contents of the Swedish lake waters. Quantitatively the s. Swedish triclad populations compare most closely with those of Mid-Scotland in the n. Britain area.

---

Zusammenfassung Es gibt im Norden Britanniens eine grössere Anzahl von Tricladen (10) die Süsswasserseen bewohnen, als in Süd-Schweden (7) und einige Sorten verbreiten sich in ungefähr gleichen Arten von Seen in verschiedenem Maasse in den beiden Ländern. Dendrocoelum lacteum (Müller) erscheint in einer grossen Reihe verschiedenartiger Seen in Süd-Schweden, beschränkt sich aber im Norden Britanniens auf die Seen mit grösserem Reichtum an Lebewesen. Polycelis nigra (Müller) — in Schweden nicht vorhanden-, hat eine ähnlich weite Verbreitung in Britannien. In Süd-Schweden ist in Seen aller Art ein reicherer Bestand an PLanaria torva (Müller), besonders in den Seen mit geringerem Bestand an Lebewesen. Die Polycelis Art P. tenuis (Ijima) und P. hepta E. H. und Y. Melander und auch der Dugesia lugubris Arten-Komplex zeigen dieselbe Verbreitung in beiden Gegenden. Polycelis felina (Dalyell) kommt in Schweden nicht vor. Die kleine Zahl finnischer Seen, denen Proben entnommen wurden, bestätigen die Befunde von Süd-Schweden. Wesentlicher Zusammenhang besteht zwischen der gesamten Reichhaltigheit von Tricladen und dem Gehalt an Kalk und aufgelöster Substanz bei den schwedischen Süsswasserseen. Mengenmässig ist die Verbreitung von Tricladen in Süd-Schweden der im Norden Britanniens am echesten zu verleichen, soweit es sich um Mittel-Schottland handelt.

     

Genetic characterization of Mortierella alpina by sequencing the 18S‐28S ribosomal gene internal transcribed spacer region

Aims: The aim of this study was to establish a genetic background of Mortierella alpina, which is a cosmopolitan, soil‐inhabiting Zygomycete that also has important biotechnology potential. Methods and Results: A total of 44 18S‐28S ribosomal gene internal transcribed spacer (ITS1‐5·8S rDNA‐ITS2 DNA) regions of M. alpina from three diverse locations (Far East Asia, North America and West‐Central Europe) were sequenced and investigated. The sequences between M. alpina and the three closely related species (Mortierella macrocystis, Mortierella gamsii and Mortierella humilis) showed 74–84% sequence identity. When a phylogenetic tree was constructed with a neighbour‐joining algorithm, four clades of M. alpina isolates were clearly distinct with high bootstrap values. In addition, isolates from the West‐Central Europe were found to have the highest gene and nucleotide diversities. Conclusions: The ITS region was a suitable tool for distinguishing M. alpina from other closely related species. The region also provided information of the diversity of M. alpina. Significance and Impact of the Study: The study established a genetic background of M. alpina for identification and the diversity of M. alpina provided information for further isolation and screening of the fungus.     

Distribution,abundance, and size of rhabdoids in Dugesia polychroa. (Turbellaria: Tricladida)

The ontogenetic changes in the distribution, abundance, and size of rhabdoids were examined in an undisturbed laboratory population of Dugesia polychroa. Irrespective of triclad age, rhabdoids in the epidermis and parenchyma were more abundant on the dorsal than the ventral side of the body. No significant differences were found in the abundance of epidermal or parenchymal rhabdoids among the anterior, medial, and posterior regions of the body. Rhabdoid number and size changed significantly with triclad age, with a marked depression coinciding with the onset of cocoon production. Rhabdoid discharge was correlated with physical and/or physiological disturbance and occurred in the absence of any overt environmental disturbance. Simple allometric relationships were observed between rhabdoid size and number on one hand and body plan area on the other. Different allometric trends were observed from field-collected individuals compared to the undisturbed laboratory population. The potential function of rhabdoids in the Tricladida is discussed in light of these findings.     

Distribution of bulbil- and seed-producing plants of Poa alpina (Poaceae) and their growth and reproduction in common gardens suggest adaptation to different elevations

• Premise of the study: The European Alps harbor a spatially heterogeneous environment. Plants can be adapted genetically to this heterogeneity but may also respond to it by phenotypic plasticity. We expected the important fodder grass Poa alpina to be adapted to elevation either genetically or plastically. • Methods: We investigated in three elevational common gardens whether growth and reproductive allocation of plants reproducing either by seeds or bulbils suggest adaptation to their elevation of origin and to what extent they can respond plastically to different elevations. Additionally, we analyzed genetic diversity using microsatellites and tested whether seeds are of sexual origin. • Key results: In the field, bulbil-producing plants occurred more often at higher elevations, whereas seed-producing plants occurred more often at lower elevations, but bulbil-producing plants were generally less vigorous in the common gardens. The response of plants to elevational transplantation was highly plastic, and vigor was always best at the highest location. The small genetic differences were not clinally related to elevation of origin, underlining the importance of phenotypic plasticity. Reproductive allocation was, however, independent of elevational treatments. Seed-producing plants had higher genetic diversity than the bulbil-producing plants even though we found that seed-producing plants were facultative apomicts mostly reproducing asexually. • Conclusions: Bulbil-producing P. alpina, showing a fitness cost at lower elevations compared with seed-producing plants, seem better adapted to higher elevations. By means of its two reproductive modes and the capacity to adjust plastically, P. alpina is able to occupy a broad ecological niche across a large elevational range.     

Factors affecting the occurrence of Dendrocoelum lacteum (Turbellaria) in Swedish lakes

By discriminant analysis on data from 115 lakes in South Sweden it was shown that the distribution and abundance of the triclad Dendrocoelum lacteum was predominantly governed by the density of the isopod Asellus aquaticus, its main food. The occurrence of the latter was mainly correlated with the nutrient richness of the lakes, most probably via presence of appropriate detritus, chiefly allochtonous material. As opposed to British oligotrophic lakes, most Swedish nutrient-poor lakes are surrounded by deciduous vegetation, which indirectly promotes the existence of A. aquaticus and consequently D. lacteum. Presence of mat-forming plants generally seemed to depress triclad density, whereas smaller stones promoted their occurrence, at least in nutrient-rich lakes.     

Past,present and future of mountain species of the French Massif Central – the case of Soldanella alpina L. subsp. alpina (Primulaceae) and a review of other plant and animal studies

Aim Our goals were: (1) to investigate patterns of genetic variation in the French Massif Central (MC) of Soldanella alpina (Primulaceae), an alpine plant species that has only one known population in the region; (2) to analyse these patterns in order to deduce the Quaternary history of the population and to predict how current climatic warming may affect it; and (3) to review molecular analyses from the MC to evaluate the importance of the region for the conservation of genetic diversity. Location Europe, with a special focus on the French Massif Central and adjacent regions. Methods Amplified fragment length polymorphisms (AFLPs) were analysed for 192 individuals (nine populations) of S. alpina (subsp. alpina) representing the MC, Pyrenees and south‐western Alps. Population genetic diversity was assessed by various parameters (e.g. H_E, Shannon’s I). Neighbor‐Net and Bayesian approaches, and analysis of molecular variance (AMOVA) were used to infer population genetic relationships and structure. Results Individuals generally clustered according to populations within mountain regions. Hierarchical AMOVA indicated significant variation among mountain ranges (33.2% of the total variance), but there was also strong differentiation between populations (26.3%). The single population of S. alpina from the MC was identified as a distinct lineage of high genetic diversity. Our literature survey indicated that taxa with low and with high genetic diversity exist in the MC, and that genetic relationships to surrounding regions are diverse. Main conclusions The high genetic diversity and distinctiveness of S. alpina in the MC suggests the long‐term persistence of the single population in this region, which might have been favoured through elevational range shifts in response to past climatic change. This interpretation partly accords with other studies indicating that several plant and animal populations in the MC contain comparatively high genetic diversity, represent genetically independent lineages, and/or are likely descendants of populations that persisted in the MC throughout the Quaternary. These data underline the conservation importance of the MC as a key area for the long‐term persistence of species with often high levels of intraspecific genetic diversity.     

Differences in Swimming Ability and Behavior in Response to High Water Velocities among Native and Nonnative Fishes

We conducted swimming performance tests on native and nonnative fishes commonly found in Arizona streams to evaluate the extent of differences in swimming ability among species. Fishes with similar mean lengths were subjected to stepwise increases in water velocity in a laboratory swim tunnel until fish could no longer maintain position. Nonnative fathead minnows Pimephales promelas and red shiners Cyprinella lutrensis exhibited swimming abilities similar to native longfin dace Agosia chrysogaster, speckled dace Rhinichthys osculus and spikedace Meda fulgida. Nonnative mosquitofish Gambusia affinis exhibited swimming ability similar to native Gila topminnows Poeciliopsis occidentalis. Desert suckers Catostomus clarki, bluehead suckers Catostomus discobolus and speckled dace exhibited behavioral responses to high water velocities that may confer energetic advantages in swift water. Differences in swimming ability do not appear to adequately explain the disproportionate removal of nonnative fishes via flooding. Behavioral responses to high flows are more likely the mechanism that allows native fish to persist in streams during flood events.