Introgression Between Lahontan and Endangered Owens Tui Uhubs,and Apparent Discovery of a New Tui Chub in the Owens Valley,California

Owens tui chubs (Siphateles bicolor snyderi [Miller]) have become extirpated throughout most of their range by introgression with introduced Lahontan tui chubs. The remaining non-introgressed Owens tui chub populations persist in a small number of fragmented habitats. These survivors are listed as “endangered” under both the state and federal endangered species acts. This study employs six microsatellite DNA loci to assess degrees of genetic difference within and among populations of Owens and Lahontan tui chubs and their putative hybrids. It reveals four distinct groups of tui chubs: Owens, Lahontan, hybrid Owens × Lahontan, and Cabin Bar. Patterns of microsatellite DNA variation confirm that tui chubs in the Owens River and its tributaries, and Mono Lake tributaries comprise a hybrid swarm. The overall degree of introgression between Lahontan and Owens tui chubs is approximately 40%, while the remaining 60% derives from Owens tui chub’s original genetic composition. Unexpectedly, Owens tui chubs are more genetically similar to Lahontan tui chubs than to Cabin Bar tui chubs, although they share the same river basin with the latter. Cabin Bar tui chubs possess a 3 bp deletion in the flanking region of microsatellite locus Gbi-G79. We give the Cabin Bar tui chub a common name “toikona tui chub” to distinguish it from the Owens tui chub, and recommend independent protection and recovery efforts. Management practices should prevent any future genetic mixing of non-introgressed Owens, toikona, or Lahontan tui chubs with each other, or with the hybrid swarm. Habitats of Owens and toikona tui chubs should remain isolated from the Owens River. Toikona tui chubs should be established in multiple sites.     

Genetic characterization and management of the endangered Mohave tui chub

The Mohave tui chub (Siphateles bicolor mohavensis) is the only fish native to the Mojave River, California. The fish were displaced by introduced arroyo chubs (Gila orcutti) throughout most of their range, starting in the 1930s. Two potentially relictual populations and two transplanted populations were genetically characterized using 12 microsatellite DNA loci, along with contemporary cyprinid populations in the Mojave River. We found only un-hybridized Mohave tui chubs in the refuge populations, and only un-hybridized arroyo chubs in the Mojave River. The two largest Mohave tui chub populations (Lake Tuendae and China Lake) exhibit similar, comparatively high genetic variation. Another large population (Camp Cady) with low genetic diversity shows the effect of a bottleneck of ten individuals during the historic founding event. The fourth population (MC Spring) has the fewest alleles, lowest heterozygosity, and is the most divergent, suggesting that genetic drift from a persistently low effective population size has reduced genetic diversity since its apparent isolation in 1934. We recommend instituting artificial gene flow to rebuild genetic variation in Camp Cady from both Lake Tuendae and China Lake, and the establishment of new populations with founders from both Lake Tuendae and China Lake. Additionally, we comment on the infeasibility of restoring populations of Mohave tui chub in their historic habitats.     

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.     

Distribution and Habitat Use of Sturgeon Chubs (Macrhybopsis Gelida) and Sick-Lefin Chubs (M. Meeki) in the Missouri and Yellowstone Rivers, North Dakota

Sampling was conducted on the Missouri and Yellowstone rivers, North Dakota to obtain information on the distribution, abundance and habitat use of the sturgeon chub (Macrhybopsis gelida) and sicklefin chub (M. meeki)(Family Cyprinidae), two declining benthic fish species native to the Missouri River basin. The study area consisted of three distinct river segments, the Missouri River near Williston, the Missouri River near Bismarck (below Garrison Dam), and the Yellowstone River near its confluence with the Missouri River. Both species of chub were collected, mainly with a benthic trawl, throughout 94% of the range sampled in the Williston and Yellowstone segments. Sicklefin and sturgeon chubs were the second and third most abundant cyprinids, respectively, collected from the Williston and Yellowstone segments. Best-fit regression models indicated that the presence of sturgeon chubs increased with decreasing depth, increasing velocity and decreasing water clarity, and that the presence of sicklefin chubs increased with increasing depth, decreasing velocity and decreasing water clarity. In contrast, no chubs of either species were collected in trawls from the Bismarck segment. This segment had significantly deeper, faster, and clearer water than both the Williston and Yellowstone segments.     

Bluehead chub nesting activity: a potential mechanism of population persistence in degraded stream habitats

Aquatic biodiversity continues to decline as humans modify the landscape, mainly because of stream habitat alterations and loss caused by urban development. Bluehead chubs may mitigate some effects of instream habitat degradation by providing clean gravel substrate via their spawning nests. We used path analysis, an extension of multiple linear regression, to explore the relationships among instream habitat degradation, adult chub abundance, chub nesting activity, and chub reproductive performance. Age-0 chub abundance was best explained by small adult abundance and nest abundance. Habitat disturbance indirectly and negatively influenced age-0 chub abundance through adult chubs and nest abundance. Percentages of pool and run habitat also had indirect negative effects on age-0 chub abundance. Several metrics of chub nesting activity (nest density [proportion of substrate occupied by nests], average nest size, and number of nests) were explained by both adult chub abundance and nesting site conditions. Variability among stream systems described significant variation in adult chub abundance and nesting characteristics and, if unaccounted for, would have resulted in large unexplained variability. Chub nesting activity served as a link between habitat degradation, adult chub abundance, and their reproductive performance. Our study provides preliminary evidence that bluehead chubs’ nesting activity may be a mechanism of their persistence in degraded stream reaches. We recommend confirmatory studies through in-stream manipulative experiments.     

Rangewide phylogeography and landscape genetics of the Western U.S. endemic frog Rana boylii (Ranidae): implications for the conservation of frogs and rivers

Genetic data are increasingly being used in conservation planning for declining species. We sampled both the ecological and distributional limits of the foothill yellow-legged frog, Rana boylii to characterize mitochondrial DNA (mtDNA) variation in this declining, riverine amphibian. We evaluated 1525 base pairs (bp) of cytochrome b and ND2 fragments for 77 individuals from 34 localities using phylogenetic and population genetic analyses. We constructed gene trees using maximum likelihood and Bayesian inference, and quantified genetic variance (using AMOVA and partial Mantel tests) within and among hydrologic regions and river basins. Several moderately supported, geographically-cohesive mtDNA clades were recovered for R. boylii. While genetic variation was low among populations in the largest, most inclusive clade, samples from localities at the edges of the geographic range demonstrated substantial genetic divergence from each other and from more central populations. Hydrologic regions and river basins, which represent likely dispersal corridors for R. boylii, accounted for significant levels of genetic variation. These results suggest that both rivers and larger hydrologic and geographic regions should be used in conservation planning for R. boylii.     

Comparative Restriction Enzyme Analysis of Mitochondrial DNA in Several Populations of Lake Resident Chars of the Genus Salvelinus

Restriction enzyme analysis was employed in studying the mitochondrial DNA (mtDNA) ATPase6/ND4L region in several Northeast Asian populations of resident lake char of the genus Salvelinus. On evidence of mitotypes, genetic similarity was assumed for populations of neiva (Ueginskoe Lake), lake resident char from the northern coast of the Sea of Okhotsk (Mak-Mak Lake and Elekchanskie lakes), and dolly varden. Mitotype AAAA proved to be common for these populations. Lake char populations of the Juliet and Maxi lakes (the basin of the Kolyma River) had mitotype DBAA, which is similar to mitotype DBAB observed earlier in Taranetz char from Chukotka. The divergence between mitotypes AAAA and DBAA was estimated at 0.3%. Different origins were assumed for the lake resident char populations from the basins of the Sea of Okhotsk and of the Kolyma River, the former originating in the Pacific and the latter, in the Arctic basins.     

Limnology of a desertic terminal lake,Walker Lake,Nevada, U.S.A.

Walker Lake, a large terminal lake in west-central Nevada, is rapidly desiccating and becoming more saline. From 1937 to 1977, total dissolved solids increased from 5 650 to 10 650 mg l^–1. Ionically, the lake is a chlorocarbonate one; however, as desiccation continues it should eventually have about equal amounts of chloride, sulfate and carbonate. With regard to algal nutrients, the lake appears to be nitrogen limited. The phytoplankton is currently dominated by Nodularia spumigena; at times this produces noxious blooms. The zooplankton community is depauperate and composed of three species. The fish fauna is limited to three endemic fishes, with tui chub, Gila bicolor, dominant. Lahontan cutthroat trout, Salmo clarki henshawi, is restricted during summer to a narrow mid-water zone low enough in temperature and high enough in dissolved oxygen to meet physiological requirements.Dr. Koch passed away in October 1983.     

Genetic and phenotypic variation among Galaxias maculatus populations reflects contrasting landscape effects between northern and southern Patagonia

1. Understanding the influence of landscape characteristics on genetic and phenotypic intraspecific variability can yield insights into how evolutionary processes work as well as provide essential information for the conservation of biodiversity. 2. Our aim was to compare the genetic structure and phenotypic variation among Galaxias maculatus populations inhabiting two Atlantic Ocean river basins in Patagonia in relation to historical and contemporary landscape characteristics associated with latitude. 3. Population genetic analysis (based on eight microsatellite loci, 505 individuals) indicates that genetic structure is more pronounced in the Río Negro basin (RN) at 39–41°S (10 localities) than in the southernmost Santa Cruz River basin (SCR) at 49–50°S (seven localities). Spatial autocorrelation analysis showed different effects of geographic distance in shaping population differentiation patterns in the two basins. 4. While in northern Patagonia, fragmented populations could have survived the severity of Quaternary climate cycles, at higher latitudes G. maculatus populations were probably extirpated by extensive ice sheets. Extant populations in the upper reaches of the southernmost basin probably originated from refugia close to the Atlantic Ocean. 5. Based on otolith microchemistry, we have documented facultative diadromy for the first time for the species in the SCR basin, while no evidence of migration to the sea was found in individuals from the RN basin. Vertebral number increased with latitude, and within the SCR basin, the higher counts are possibly associated with a migratory life style.     

Characterization of microsatellite loci for five members of the minnow family Cyprinidae found in the Sacramento–San Joaquin Delta and its tributaries

Two microsatellite‐enriched libraries [(CAGA)_n, (TAGA)_n] were constructed using pooled DNA from three cyprinid species native to the Sacramento–San Joaquin Delta of California: Sacramento splittail (Pogonichthys macrolepidotus); Sacramento pikeminnow (Ptychocheilus grandis); and tui chub (Siphateles bicolor). Primers were designed for 105 loci and tested for levels of polymorphism in five cyprinid species found in the Delta: Sacramento splittail, Sacramento pikeminnow, tui chub, hitch (Lavinia exilicauda), and Sacramento blackfish (Orthodon microlepidotus). Fifty‐one loci were polymorphic for at least one species and 31 loci were polymorphic for multiple species. The number of polymorphic loci per species ranged from 16 to 26.     

All grown‐up and nowhere to go: paedomorphosis and local adaptation in Ambystoma salamanders in the Cuenca Oriental of Mexico

Facultative or obligate paedomorphosis has evolved several times in Mexican populations of the salamander genus Ambystoma, leading to increased genetic divergence among populations with alternate life histories and contributing to population divergence in this species complex. In the present study, we surveyed the genetic diversity of Ambystoma populations in lakes of the Cuenca Oriental, a high elevation closed drainage basin that encompasses permanent crater lakes harbouring salamander populations. We genotyped individuals from five populations aiming to better understand population dynamics and the evolution of paedomorphosis in this system. Specifically, we tested the hypotheses that the evolution of paedomorphosis in Ambystoma taylori resulted in reduced genetic exchange with populations of Ambystoma velasci in neighbouring lakes. Second, we tested whether the populations in brackish lakes of the Cuenca Oriental, Lake Atexcac, and Lake Alchichica show restricted gene flow across the basin, possibly as a result of local adaptation to those microhabitats. Using various indices of population genetic diversity, Bayesian assignment, and approximate Bayesian computation methods, we show that genetic exchange between brackish lakes and freshwater lakes is negligible, despite continued gene flow among freshwater lakes. We show that the first divergence among populations occurred between Alchichica and the remaining populations and that the evolution of paedomorphosis in A. taylori was likely favoured by local adaptation to saline conditions, thus increasing its genetic isolation. An apparently similar process appears to be in progress independently in lake Atexcac, showing that local adaptation may play an important role in population isolation and, ultimately, in speciation.     

Acoustic homogeneity in the piranha Serrasalmus maculatus

Different studies suggest some social calls could be used in fish identification if their specificity is unambiguously assessed. Sounds of different populations of piranhas Serrasalmus maculatus Kner, 1858 were recorded to determine their homogeneity between rivers inside a single basin (Araguari and Grande River, upper Paraná River basin) and between separated basins (Amazon and Paraná basins). All fish from the different populations produced sounds with similar acoustic features. Consequently, the populations were not discernible based on individual sound characteristics. This high homogeneity between sounds from different populations indicates their usefulness for conservation projects using passive acoustic monitoring in piranhas. Moreover, it supports the use of acoustic features as complementary key characteristics in taxonomic studies.     

Molecular data reveal a complex population genetic structure for Psalidodon scabripinnis (Teleostei: Characidae) in the Atlantic Rainforest,Brazil

Recently renamed, Psalidodon scabripinnis populations of Serra da Mantiqueira, previously known as Astyanax scabripinnis have been deeply studied in the last years. These populations are small and isolated and occur very close to the watershed between Paraíba do Sul River basin and Upper Paraná River basin, in Serra da Mantiqueira region in the Atlantic Rainforest. These conditions arouse the interest in knowing theor genetic conservation status and how they responded to the separation between the two rivers basins. Therefore, we accessed the genetic diversity of five P. scabripinnis populations of this region with microsatellites and mitochondrial data. The results showed a complex structure pattern that doesn’t match the simple basin separation and a reasonably conservation status when compared with other populations of the same family or with similar natural history.     

Movements,status, access to nectar,and spatial organisation of the tui

Abstract

Movements of tui (Prosthetnadera novaeseelandiae) breeding on Tiritiri Matangi Island were followed and related to changes in nectar access. The island has limited nectar sources and birds must move to gain access to nectar year round. All tui leave the island, although the extent and timing of movement varies for different individuals. Tui return for breeding but again the timing of the return varies for individuals. Nectar sources were typically concentrated in both time and space, and access was related to individual asymmetries such as sex, residential status and age. These same asymmetries also relate to the timing of individuals movements, and where individuals nest relative to nectar sources. At concentrated food sources, access was determined by an absolute social hierarchy. Although tui defend exclusive feeding territories, breeding territories are not exclusive and access to nectar is determined by distance to nest site. Such variability in spatial organisation is related to a continuum concept of social organisation.     

The impact of fish spawning on metal and protein levels in gastrointestinal cytosol of indigenous European chub

The study presented here reports for the first time cytosolic metal and protein levels in the gastrointestinal tissue of field-collected European chub (Squalius cephalus), living in low metal-contaminated river section. In two sub-cellular fractions (untreated cytosol and heat-treated cytosol), isolated from the whole gastrointestinal tract of indigenous chubs collected during spawning (April/May 2006) and post-spawning period (September 2006), seasonal or gender related differences of trace metals and proteins were determined. In both fractions, cytosol and heat-treated cytosol, metal levels decrease as follows: Zn > Fe > Cu > Mn > Cd and are significantly higher during the spawning period. Besides that, the level of heat-sensitive proteins (metalloenzymes) in cytosolic fractions is also significantly higher during the spawning period in both male and female specimens. Higher condition indices of chubs in the spawning period imply higher feeding activity, energy reserves and recent growth of indigenous chubs. Metallothionein levels, determined in the heat-treated cytosol, are comparable in gastrointestinal tract of feral chubs collected in both seasons and confine the background metallothionein levels, on average 3 mg g⁻¹ wet tissue. Chub spawning has been identified as a confounding factor, having an impact on cytosolic metal and protein levels, presumably due to enhanced food supply (higher condition indices) and fish spawning (higher gonadosomatic indices in some male specimens).     

Complex evolutionary history in the brown trout: Insights on the recognition of conservation units

We screened genetic variation in a polytypicorganism, whose populations are oftendistributed into numerous isolated habitats,and integrated the results into a critique ofdefining ``units' of conservation for organismswith highly fragmented populations. Sixteenpopulations of brown trout Salmo truttaL. across 8 Portuguese river basins werescreened for variation at 5 loci (mtDNA andallozymes). Population history based on mtDNArevealed a mosaic pattern driven by pastfragmentation and restricted gene flow withlittle correspondence to major river drainagesor recently proposed OCUs on the IberianPeninsula. Such patterns of variation offer achallenge to conservation strategies that basethemselves on defining units of conservation,particularly if such units intend to reflect ahierarchical evolutionary structure. Wesuggest that geographically mosaic patterns ofevolutionary lineages, as well as adaptivelysignificant traits are common characteristicsof many freshwater organisms. Thus,large-scale units, even if diagnosed by mtDNAclades, are often too heterogeneous to considera ``unit' of conservation. Alternatively, abottom-up perspective that prioritizespopulations or metapopulations is both morepractical and more effective in recognizing andpreserving evolutionary diversity.     

Homage to the Virgin of Ecology,or why an aquatic insect unadapted to desiccation may maintain populations in very small,temporary Mediterranean streams

In temporary streams, the annual constriction of drying is associated with high local extinction risk. To survive in such habitats, organisms with no specific biological traits for coping with dry periods should experience high colonisation rates from permanent reaches of the same basin or from other basins. Hydropsyche siltalai is a widespread caddisfly common in permanent and temporary headwaters reaches in the Mediterranean climate region of the Iberian Peninsula. In this study, we used genetic analyses to test if populations of H. siltalai in temporary streams are resettled from populations of the same basin or from other basins. The geographical distribution of H. siltalai was surveyed in 97 temporary and permanent reaches across four basins; larvae were found in 22 reaches (12 temporary and 10 permanent). Population genetic analyses of 11 selected reaches (6 temporary and 5 permanent) revealed low genetic diversity and no genetic population structure among and within basins. Overall, H. siltalai appeared to disperse well among basins independent of stream temporality. Permanent reaches from different basins act as a source of the individuals that recolonise temporary reaches after local extinctions, indicating a metapopulation structure at regional scale. Moreover, our results support other studies that showed that dispersal among basins is a recurrent pattern in aquatic insects.     

Fish conservation in the land of steppe and sky: Evolutionarily significant units of threatened salmonid species in Mongolia mirror major river basins

Mongolia's salmonids are suffering extensive population declines; thus, more comprehensive fisheries management and conservation strategies are required. To assist with their development, a better understanding of the genetic structure and diversity of these threatened species would allow a more targeted approach for preserving genetic variation and ultimately improve long‐term species recoveries. It is hypothesized that the unfragmented river basins that have persisted across Mongolia provide unobstructed connectivity for resident salmonid species. Thus, genetic structure is expected to be primarily segregated between major river basins. We tested this hypothesis by investigating the population structure for three salmonid genera (Hucho, Brachymystax and Thymallus) using different genetic markers to identify evolutionarily significant units (ESUs) and priority rivers to focus conservation efforts. Fish were assigned to separate ESUs when the combined evidence of mitochondrial and nuclear data indicated genetic isolation. Hucho taimen exhibited a dichotomous population structure forming two ESUs, with five priority rivers. Within the Brachymystax genus, there were three B. lenokESUs and one B. tumensisESU, along with six priority rivers. While B. tumensiswas confirmed to display divergent mtDNA haplotypes, haplotype sharing between these two congeneric species was also identified. For T. baicalensis,only a single ESU was assigned, with five priority rivers identified plus Lake Hovsgol. Additionally, we confirmed that T. nigrescens from Lake Hovsgol is a synonym of T. baicalensis. Across all species, the most prominent pattern was strong differentiation among major river basins with low differentiation and weak patterns of isolation by distance within river basins, which corroborated our hypothesis of high within‐basin connectivity across Mongolia. This new genetic information provides authorities the opportunity to distribute resources for management between ESUs while assigning additional protection for the more genetically valuable salmonid rivers so that the greatest adaptive potential within each species can be preserved.     

Rotifer vertical distributions in a meromictic basin of Lake Banyoles (Spain)

The vertical distribution of rotifer populations has been analyzed in a meromictic basin (III) of the karstic Lake Banyoles. This basin had, at the time of the study, an anaerobic monimolimnion from around 17 m in summer or 21 in winter to 25 m, its maximum depth. However, below this layer a warmer microaerophilic zone with suspended marls is found in a chimney to a depth of 130 m.The rotifer distributions of several years are compared. The presence of large populations of rotifers at the oxic-anoxic interface is constant through the years, but highly variable regarding the total abundance and relative proportions of the species, depending on the importance of the vertical mixing in winter and the posterior segregation of water layers as a function of production and decomposition processes. Filinia hofmanni, Filinia longiseta longiseta are species with a restricted occurrence at the oxycline and are not present in the other non meromictic basins of the lake. Filinia terminalis, more broadly distributed, also has dense populations in summer at the oxycline in basin III, but disappears from the plankton during this season in the other basins. Other species, such as Polyarthra dolichoptera, Anuraeopsis fissa, Keratella cochlearis and Kellicottia longispina, also showed maxima at the oxycline in summer, as well as other maxima in the metalimnion. Populations at the oxycline are probably different ecotypes adapted to low oxygen conditions, but having the advantage of high food availability.     

Comparative restriction enzyme analysis of mitochondrial DNA in several populations of lake resident chars of the genus Salvelinus

Restriction enzyme analysis was employed in studying the mitochondrial DNA (mtDNA) ATPase6/ND4L region in several Northeast Asian populations of resident lake char of the genus Salvelinus. On evidence of mitotypes, genetic similarity was assumed for populations of neiva (Ueginskoe Lake), lake resident char from the northern coast of the Sea of Okhotsk (Mak-Mak Lake and Elekchanskie lakes), and dolly varden. Mitotype AAAA proved to be common for these populations. Lake char populations of the Juliet and Maxi lakes (the basin of the Kolyma river) had mitotype DBAA, which is similar to mitotype DBAB observed earlier in Taranetz char S. taranetzi from Chukotka. The divergence between mitotypes AAA and DBAA was estimated at 0.3%. Different origins were assumed for the lake resident char populations from the basins of the Sea of Okhotsk and of the Kolyma River, the former originating in the Pacific and the latter, in the Arctic basins.