Nest-site selection is a critical process in the life history of amphibians, directly influencing offspring survival and parental fitness. When and where an amphibian chooses to nest is strongly influenced by a range of environmental cues. In this study, we evaluated nest-site selection of the Southern Two-lined salamander, Eurycea cirrigera, in relation to a range of environmental conditions. We monitored nesting E. cirrigera under coverboards at two seepage wetlands in the South Carolina inner Coastal Plain during the breeding season of E. cirrigera. We examined nest-site selection by E. cirrigera at two scales (landscape scale and microhabitat scale) using logistic regression and AIC model selection. We found that E. cirrigera select nest sites using environmental cues across multiple spatial scales where females actively discriminate among nesting locations based on measures of temperature, hydrology, and water depth. Because amphibians are so sensitive to environmental change and variation, understanding the factors that influence key life history processes, particularly breeding phenology and oviposition site choice, are critical to the conservation of amphibian populations and their habitats.

In a biosphere transformed by human activities, understanding the relationship between age, developmental stage, or body mass and toxicological sensitivity is a relevant endeavor because the environmental release of some quantitatively important contaminants follows predictable seasonal patterns, as do wildlife demographic events. We tested the hypothesis that the sensitivity of the gladiator frog, Hypsiboas faber, to components and/or dissolution products of fertilizers varies predictably through ontogeny by sequentially exposing eggs, embryos, and larvae to ammonium nitrate, sodium nitrate, sodium nitrite, and ammonium sulfate. Nitrate was the least toxic nitrogen ion regardless of stage; the most deadly compound was ammonium or nitrite, depending on stage. Overall, embryos were more sensitive to inorganic nitrogen than more advanced developmental stages, indicating that the jelly capsule envelopes that surround the egg do not provide effective protection against contaminants. However, for most compounds tested, the relationship between lethal concentrations (LC_x), no-observed effect concentrations (NOEC), and lowest observed effect concentrations (LOEC) and developmental stage or mass was not monotonic. Whereas for sodium nitrate sensitivity declined asymptotically with developmental stage, for ammonium nitrate, sodium nitrite, and ammonium sulfate, sensitivity declined through early development and then increased again at Gosner stage 25. Together with previously published literature, this finding indicates no single and predictable trend in sensitivity through development, even if we restrict our analysis to a relatively narrow range of organisms and contaminants. Such a relationship creates complex scenarios of risk as a function of the phenology of application of fertilizers and of the temporal variation in environmental factors that modulate nitrogen speciation and toxicity in and near agricultural fields.

Na biosfera transformada por atividades humanas, entender a relação entre idade, estágio de desenvolvimento e sensibilidade toxicológica é um objetivo relevante porque a descarga ambiental de alguns importantes contaminantes segue padrões sazonais previsíveis, como ocorre com eventos demográficos da vida selvagem. Testamos a hipótese de que a sensibilidade do sapo ferreiro Hypsiboas faber a componentes e/ou produtos de dissolução de fertilizantes varia previsivelmente ao longo da ontogenia. Para tal, expusemos sequencialmente ovos, embriões e larvas da espécie ao nitrato de amônio, nitrato de sódio, nitrito de sódio e sulfato de amônio. Independente de estágio de desenvolvimento, nitrato foi o íon menos tóxico; o íon mais tóxico foi nitrito ou amônio, dependendo do estágio. De forma geral, embriões foram mais sensíveis ao nitrogênio inorgânico que estágios mais avançados de desenvolvimento, indicando que as cápsulas gelatinosas que recobrem o ovo não proporcionam proteção efetiva contra contaminantes. No entanto, para a maior parte dos compostos, não foi monotônica a relação entre concentrações letais, concentrações sem efeito observado, ou concentrações mínimas com feito observado e estágio de desenvolvimento ou massa. Se por um lado a sensibilidade ao nitrato de sódio declinou de forma assintótica com estágio, para sulfato de amônio, nitrito de sódio e sulfato de amônio a sensibilidade declinou ao longo do início do desenvolvimento, e depois aumentou novamente no estágio 25 de Gosner. Juntamente com literatura publicada anteriormente, estas observações sugerem que não há uma única tendência previsível para a sensibilidade ao longo do desenvolvimento, mesmo se restringirmos nossa análise para uma faixa relativamente estreita de organismos e contaminantes. Esta relação cria cenários complexos de risco em função da aplicação de fertilizantes, e da variação temporal nos fatores ambientais que modulam a especiação e toxicidade do nitrogênio em campos

Eastern North Pacific species of the fathead sculpin genus Malacocottus Bean are assessed following examination of over 300 specimens collected from throughout the known range of the genus, from the west coast of North America around the Pacific Rim to Japan, including the marginal waters of the Salish Sea, Bering Sea, Sea of Okhotsk, and Sea of Japan. The results of this study demonstrate that two species of Malacocottus occur in the eastern North Pacific. Malacocottus zonurus is found in the North Pacific from Washington State around the Pacific Rim to Japan, and in all marginal seas. Malacocottus kincaidi Gilbert and Thompson is apparently endemic to the Salish Sea, known only from Puget Sound and the Strait of Georgia. These two species differ in preopercular spine morphology and gill-raker counts. Malacocottus aleuticus Smith, based on a single juvenile specimen, is a synonym of M. zonurus. This study includes redescriptions of M. zonurus and M. kincaidi, comparisons of both species with M. gibber, and a key to the three known species of the genus.

Rhamphichthys heleios, new species, is described from the Amazon Basin in Brazil, being known from lakes and channels associated with the floodplains of large rivers. The new species is readily distinguished from all other congeners by a unique color pattern, composed of a series of dark irregular rounded blotches along the lateral body surface over the lateral line, and by the absence of clearly formed saddles across the dorsum. Comments on the taxonomy and use of color pattern for the systematics of Rhamphichthys are made based on examination of extensive materials in museum collections, and a key to the species of the genus occurring in the Amazon Basin is provided.

Rhamphichthys heleios, espécie nova, é descrita para a Bacia Amazônica no Brasil, sendo encontrada em lagos e canais juntos a planície de inundação de grandes rios. A espécie nova se diferencia das demais espécies de Rhamphichthys pelo seu padrão de colorido único que é composto por uma série de manchas escuras arredondadas na lateral do corpo ao longo da linha lateral e pela ausência de selas escuras no dorso. Comentários sobre a taxônomia e o uso do padrão de colorido na sistemática de Rhamphichthys são feitos basedo em uma extensa revisão de material em coleções e é fornecido uma chave de identificação das espécies do gênero da bacia amazônica.

The Pascagoula Map Turtle (Graptemys gibbonsi) is a narrowly endemic species found only in the Pascagoula River drainage in Mississippi. It is among the most poorly known turtle species because of research taxonomic biases and this species' relatively recent recognition as a unique taxon. A recent petition requested protective status for G. gibbonsi under the U.S. Endangered Species Act. We describe population parameters, quantitatively assess sexual dimorphism of G. gibbonsi, and document hormone secretion patterns from the Chickasawhay and Leaf rivers in Mississippi. We demonstrate a significant male-skewed sex ratio and a female-biased size dimorphism in both carapace length and height. Males showed a bimodal peak of plasma testosterone in fall and spring, consistent with the pattern shown by many other southeastern turtles with late summer-fall spermatogenesis and mating during spring and fall. Females did not show seasonal variation in estradiol secretion, an unexpected result that was possibly due to our small sample size of females, none of which were gravid when captured. Although this observation may be due to our limited capacity to sample females, given the reproductive issues reported for Graptemys flavimaculata from the same drainage (e.g., reproductive hormone abnormalities, low nesting frequency and success), this finding warrants concern and necessitates additional research. Finally, in order to put our hormone data in context, we briefly review hormone and reproductive patterns in southeastern U.S. turtles. Our review includes the timing of follicular enlargement, ovulation and nesting, clutch frequency, and estradiol cycles. The review for male turtles includes details on the spermatogenic cycle, spermiation, and the timing and frequency of testosterone peaks.

This study explored whether persistent differences in life history traits between populations of Least Killifish Heterandria formosa could be explained by differences in habitat-associated water type, reflecting either local adaptation or phenotypic plasticity. Fish native to a pond and a spring site were reared in the lab in either pond or spring water. Fish reared in pond water reached maturity faster and at the same size as fish reared in spring water, regardless of source population. There was no difference in daily mortality rate between fish raised in the different water types, but the longer time to maturity in spring water produced a lower cumulative survival to maturity. Water type did not affect fecundity, but fish from the spring population had larger offspring, contrary to patterns found in both the field and previously in the lab. Persistent differences among natural populations in life history traits have previously been attributed to differences in population density and predation pressure. While water type affects the expression of some life history traits in Least Killifish, those effects cannot explain the patterns of trait variation among natural populations.

Clay model experiments are commonly used to measure natural rates of predation and have become an important method in studying predator avoidance of aposematic frogs. Previous clay model experiments have demonstrated that conspicuous coloration in dendrobatid frogs is an effective deterrent to avian predators. It is generally assumed that predators recognize clay models as frogs, but few studies have examined this hypothesis. Certain aposematic frogs are similar in color to fruits on the forest floor, and it is possible that frugivorous or omnivorous birds perceive clay models as fruit. In the present study, we further investigate aposematism in Oophaga pumilio and specifically examine the importance of model shape and color. We assessed natural avian predation rates using clay models, which were either red or brown in color, and frog or ball (fruit) shaped. Overall, avian predation was significantly higher on red ball-shaped models when compared to red frog-shaped models. Brown frogs were also more likely to be preyed upon than red frogs. The omnivorous Great Tinamou (Tinamus major), however, exhibited no preference for frog color. Feeding naturally on fruits and seeds, tinamous in our study preferred and attacked red ball models more frequently, suggesting that they recognized these models as fruits. Collectively, our results provide evidence that birds distinguish between shapes and colors when making decisions about predation and that these attacks are dependent on the dietary preference of the predator. Clay model studies should take into account both color and shape of models, and consider that predation rates are likely dependent on the species assemblages present at a location and their specific dietary preferences.

This study investigates the evolutionary relationships among species in the family Scopelarchidae with molecular (eight genes) and morphological data. A new genus of pearleye is diagnosed, Lagiacrusichthys, new genus, from a previously described species (Benthalbella macropinna) distributed in Antarctic waters. The diagnosis of Lagiacrusichthys is based on molecular and anatomical information, including a highly reduced dorsal fin (5–6 rays) and a long anal fin (35–39 rays). The results represent the most taxonomically comprehensive molecular and total evidence hypotheses of the evolutionary relationships of the pearleyes to date (13 of 18 species), and these frameworks are used to comment on the historical biogeography of this widespread group. It is inferred that the pearleyes likely first evolved in central-tropical waters, with two independent invasions into Antarctic waters.

Recently, increases in both road deicing salt use and impervious cover have caused salinity to increase in urban aquatic environments. Road deicing salts consist of salt, abrasives, metals, and anticaking agents, all of which can be transferred to surrounding aquatic environments through runoff. Few studies have attempted to identify the relative toxicity of road deicing salt ingredients. To investigate the relative toxicity of NaCl and road deicing salt to amphibians, we exposed embryonic Rana ( = Lithobates) clamitans and larval Eurycea bislineata to NaCl and road deicing salt solutions with comparable NaCl concentrations in laboratory microcosms. Chemical analysis indicated the road deicing salt used was similar in chemical make up to other road deicing salt and was predominately (98.2%) NaCl. For both species we found little difference in survival between road deicing salt exposures and NaCl exposures. Our results suggest toxicity of road deicing salt is likely related to loss of osmoregulatory control as a result of NaCl exposure.

Settlement-stage larvae of the widespread apogonid Gymnapogon urospilotus are described and illustrated from specimens captured with crest nets at Moorea, Society Islands. Identification was confirmed by COI mitochondrial DNA analysis. Otoliths of the larvae had no settlement mark, indicating they had not previously settled, and 33–40 presumed daily rings. The larvae are transparent with large orange/red blotches on the tail, and limited melanophores on head and pelvic fins. The larvae have very long pelvic-fin rays (40–50% standard length [SL]) with black tips and contrasting white bands, and limited inter-ray membranes. They are apparently unique among teleost fishes in having a strongly serrate urohyal. These serrations disappear after settlement. Critical speed of the larvae was measured in a swimming chamber. Larvae of G. urospilotus are the largest (19–24 mm SL), oldest (33–40 days), and fastest (>36 cm s⁻¹) known apogonids at settlement. Photos of larvae of G. urospilotus from Guam, Ryukyu Islands, and Indonesia reveal they swim 2–3 m above coral reefs at night with the pelvic rays spread wide, presumably looking for settlement habitat. They are very conspicuous and may be mimicking small lionfish. In contrast, adults have never been seen alive on the reef. The largest reported adult G. urospilotus is 37 mm SL, which implies that this species undergoes a major portion of its growth as a pelagic larva, a life history pattern that also occurs in some reef gobiids.

A repeated pattern in North American fishes is species having geographic ranges consisting of two disjunct, widely separated areas of distribution, one in previously glaciated northern areas and one in the unglaciated Ozarks. We used phylogenetic analyses of mitochondrial DNA (ND2 and cyt b) and a nuclear DNA sequence (S7 intron 1) to examine the historical biogeography of one such species, the Least Darter, Etheostoma microperca. Uniquely for Ozark fishes, populations in western Ozark tributaries of the Arkansas River represent most of the evolutionary legacy of the species, with three markedly divergent cyt b clades. Populations in the Illinois River (Arkansas) and Shoal Creek (Missouri) appear to have been isolated for about 5 and 2 my, respectively, and potentially represent undescribed species. A wide-ranging northern clade (Hudson Bay, Great Lakes, and Ohio and upper Mississippi river systems) was sister to a clade comprising haplotypes from Blue River and all Ozark haplotypes exclusive of the Illinois River and Shoal Creek clades. The northern clade appears to have survived Illinoian and Wisconsin glaciations in one or more northern refuges and exhibits molecular genetic signals of population expansion during the Sangamon interglacial. The Blue River and western Ozark populations are especially susceptible to local extirpation with little opportunity for replacement. Persistence of these populations will require maintenance of springflows via regional groundwater management.

A morphological study of female genital papillae of Etheostoma was conducted to examine the evolution of papillae as predicted by molecular phylogenies, and to examine correlations between papilla morphology and spawning behaviors and oviposition. Thirteen characters were used to describe variation in papillae in 128 species. Based on maximum likelihood ancestral state reconstructions, we corroborated several molecular phylogenetic hypotheses with morphology and developed hypotheses on several functional traits/adaptive traits and their associations with spawning behaviors. Papillar synapomorphies supported a close relationship between Allohistium and (Etheostoma Nanostoma) Ulocentra, a monophyletic Catonotus, and a sister-group relationship between E. vitreum and Boleosoma. Results suggest that the most recent common ancestor of Etheostoma buried eggs and had a simple tube with a distal, posteriorly oriented genital pore. All egg-burying species, except species of Nothonotus, have tube papillae that inject eggs into substrate. Females of Nothonotus have short, mound, and mound-tube papillae and typically bury their entire body to deposit eggs. Egg-clumping species have mound papillae. Most species that attach eggs to objects above the substrate, the most common behavior in Etheostoma, have tube papillae; the only exceptions are E. (Psychromaster) pallididorsum with a mound papilla, and E. (Vaillantia) davisoni with a mound-tube papilla. All egg-clustering species have complex, wide, and pleated rosette papillae with ventrally directed genital pores for adpressing eggs to the undersides of rocks or logs. The only species with a rosette papilla that is not an egg-clusterer is E. vitreum, which has been described as a communal egg-attacher. The papilla of E. vitreum is unique in being rosette with dense villi and a bifurcate papillar platform. The basal platform, swollen tissue immediately posterior to the base of the genital papilla that probably enhances maneuverability and precision of oviposition, appeared at the base of a large clade including all egg-clustering species and a large number of egg-attaching species. Adaptations in papilla morphology likely played a role in the expanded use of stream habitats and the diversification of darters.

Human impacts on aquatic systems are pervasive and often extreme worldwide, resulting in numerous fish species, as well as other aquatic organisms, being at risk of extinction. Until recently, however, species targeted in conservation efforts have been treated as static units, rather than as locally evolving populations. The intent of the ASIH 2013 symposium, Fish Out of Water: Evolutionary and Ecological Issues in the Conservation of Fishes in Water-Altered Environments, was to examine fish assemblage responses to anthropogenic impacts and the potential for altered evolutionary trajectories. The recent realization that feedback between ecology and evolution can occur on ecological time scales emphasizes that ecological studies cannot assume evolutionary stasis. The cyclical interaction of ecology and evolution, termed eco-evolution, suggests that both directions of effect, ecology to evolution and evolution to ecology, are substantial. Such interactions seem to be particularly likely in many impoundments. For instance, various species of fishes show shifts in morphology in reservoir compared to stream environments, although the changes are generally species-specific or system-specific. In general, conservation efforts to recover populations that have changed in response to human-altered habitats could be compromised if systems are returned to quasi-normal states because of Darwinian debt, the situation where evolutionary recovery from genetic changes caused by anthropogenic impacts can take longer than the time required to induce the changes, resulting in evolutionary costs for future generations.

Fish with perennial life histories that inhabit ecosystems where water availability fluctuates seasonally must have movement behavior that accommodates this environmental change. Landscape structure is expected to influence magnitude and direction of these movements by affecting the distribution of water in space and time. Predicting the effects of climate change and restoring historical hydrology in the Florida Everglades, a large wetland that undergoes regular contraction in ecosystem size during seasonal droughts, requires information on how fish movement is affected by spatiotemporal patterns of water availability. We used radio telemetry to quantify spatial scale and direction of displacement of Florida Gar (Lepisosteus platyrhinchus) from focal areas of the Everglades that differ in their seasonal hydrology and position relative to drought refuges. Displacement distances increased during both rising and dropping water levels compared to periods of stable water depth, but increased more and in more directed fashion when ecosystem size was contracting. The initial position of fish relative to natural (i.e., creeks and sloughs) and artificial (i.e., canals) refuge habitats directed dry-season movement and influenced displacement distances by attracting individuals from long distances and reducing inclination of nearby fish to disperse. During rising water, displacement distances overlapped between locations near and far from dry-season refuges because of increased displacement from crowded refuge habitats and decreased movement distances at short-hydroperiod marshes. Florida Gar display flexible movement strategies that accommodate the influence of landscape context on hydrology and distance to drought refuges. Modification of the canal-levee network, managed water releases, and climate change in the Florida Everglades will interact with seasonal displacement of this abundant predator in shaping its population dynamics and food web impacts during and after drought disturbances.

Razorback Sucker Xyrauchen texanus is iconic of the plight of native “big-river” fishes of the Colorado River system of western North America. The species was historically widespread and abundant throughout the basin but has suffered substantial range reductions and population declines now characteristic of Western fishes. By the 1960s the largest remaining population was in Lake Mohave, a lower Colorado River reservoir where casual monitoring began in the mid-1950s and intensified to focus on Razorback Sucker in the late 1970s. The population then was comprised of several hundred thousand large adults, but recruitment past the larval stage was nil presumably because of predation by non-native fishes and potentially worsened by nutritional limitation. Remnant adults began to dwindle in the 1980s and were virtually gone within twenty years. An ad-hoc “Lake Mohave Native Fishes Work Group” initiated investigations to identify and understand the reasons for recruitment failure and launched an informal program to perpetuate Razorback Sucker in the reservoir. The initial goal was to establish a population of 50,000 adults in Lake Mohave, and the group developed an innovative and ultimately successful strategy in which Razorback Sucker larvae produced naturally by wild adults in the lake were harvested, reared in protected off-channel habitats, and repatriated. Demographic monitoring continued and expanded, providing annual census estimates of population abundance and trends of wild and repatriated fish. Critical genetic monitoring was initiated to track spatial and temporal diversity of harvested larvae and captured repatriates. Wild adults now are gone from Lake Mohave, but they have been replaced by a genetically diverse repatriate population of several thousand fish that spawn annually and provide larvae to continue the management cycle. However, the program is stymied by continued post-larval recruitment failure and predation losses of even the largest stocked Razorback Sucker. The program depends on stocking to maintain a repatriate population and for now has preserved the genetic legacy of the species. The species fares no better elsewhere in the basin where historical genetic diversity was lower, and, with the exception of Lake Mead, wild adults have perished and populations are maintained only by stocking of hatchery-produced fish. Naturally self-sustaining populations of Razorback Sucker are unlikely to ever again occupy the lower Colorado River mainstem and the species will remain “conservation-reliant.” A conceptual strategy that integrates use of non-native-free backwaters and the river channel has promise for this and other big-river species, and its implementation should be aggressively pursued.

Spatial ecology and movement strategies of aquatic organisms may limit their response to human-caused drying of wetland habitats. We characterized the movement strategies of the most abundant species of fish in the wetlands of the Everglades (USA) to better understand how they cope with annual fluctuations in aquatic habitat size. Over a six-year period, we used a sampling method designed to measure the density, activity levels, and movement direction of small fishes. We estimated changes in displacement speed and directional bias to identify patterns of movement that different fishes use to disperse over the gradient of disturbance in this environment. Movement of fishes ranged from highly active and directed to passive and random, and varied with hydrological condition (water rising, stable, or dropping). Six of the eight species studied displayed “directed” movement (possibly displaying taxis along environmental gradients) that varied in both speed and directional bias in response to hydrological cues. The remaining two species did not adjust the direction that they moved in response to hydrological cues, but their activity levels increased. Moving with directional bias may improve a fish's chance of early arrival in a newly available habitat or of escaping the risk of desiccation in drying wetlands. Fishes that change activity levels may improve their likelihood of reaching favorable environments by increasing diffusion rates and greater sampling of the environment. Interspecific variation in movement strategies is predicted to play a large role in community structure and may be a primary driver of the dynamics of the Everglades fish metacommunity.

In the past century and a half, surface waters in the lower Great Plains have been impacted by numerous factors related to human settlement and development of the region including construction of reservoirs, which have been well documented to have negative effects on stream fish communities. In Oklahoma, by 1925 there were only seven artificial impoundments (of 36–970 hectares), but by 2007 there were 146 impoundments in the state lake registry ranging up to 42,000 hectares. Most were built from the 1930s to the 1970s. We examined historic and recent distribution patterns of fishes in Oklahoma and western Arkansas using data from 86 collections made by A. I. Ortenburger from 1925–1927 and from 381 collections we made from 1975–2009 in the same region, to ask if faunal changes were apparent following the era of dam construction. Although exact sites in the 1920s and in 1975–2009 were not identical, there were collections in 14 Hydrologic Units (HUCs as identified by eight-digit Hydrologic Unit Codes) in the two periods that we considered comparable. At the regional level, we asked whether species collected in 1925–1927 were still present in 1975–2009. For the 25 most-common species in the 1925–1927 collections we also compared patterns of species associations (co-occurrences) in the two time periods. At the level of the 14 shared HUCs, we compared faunal composition of each HUC across time (based on the 25 common species) and examined the faunal similarity among HUCs in both time periods. We also examined occurrences of the 25 common species within individual HUCs over time as well as patterns of species associations across HUCs in the two periods. At the regional level, 81 of the 95 species collected in 1925–1927 were found by us in 1975–2009, and species association patterns were congruent across both collecting eras, suggesting that overall patterns of community composition were similar and that broad zoogeographic patterns of species distributions did not change between the two periods. At the level of the 14 HUCs, faunal composition in 1975–2009 was 76% to 100% similar with respect to species present in 1925–1927 in ten of the HUCs, but four HUCs had only 44% to 64% of species remaining. Patterns of faunal similarity among HUCs in the two periods were congruent overall, indicating that relative patterns of faunal similarity had not changed among HUCs, but an increase in the mean similarity among HUCs in 1975–2009 relative to 1925–1927 suggests that there has been some level of faunal homogenization, which may be attributable to spread of centrarchids since the historical collections. Across the 14 HUCs, 15 of the 25 species were collected in at least 80% of the HUCs in 1975–2009 in which they were initially collected 1925–1927, four species were recollected in 60% to 75%, and six were recollected in fewer than 50%. Although fish distribution patterns appear to have changed little at the regional level, there are some changes evident at the smaller scale of HUCs, but even at that level, fishes present in collections made before the era of dam building are mostly still present in those drainages today.

Alterations to the Pecos River in New Mexico and Texas, USA, including damming and river channelization, plus water extraction and diversion from, and pollution of associated habitats during the 19^th and 20^th centuries have greatly impacted many fish species. The Pecos pupfish (Cyprinodon pecosensis) is one species that was heavily impacted, especially because introduction of a congener, the sheepshead minnow (C. variegatus), to the Pecos River in the 1980s eliminated pure C. pecosensis from most of its range via hybridization. Currently, C. pecosensis is restricted to generally small isolated habitats, although historically this species had a large metapopulation with a large geographic range. The current study was an initial survey of morphological variation within different isolated habitat complexes to determine if there were habitat-morphotype distinctions. We used analysis of convex hull coverage (ACHC) with geometric morphometric data to assess whether morphotypes were distinct. ACHC results confirmed that three morphotypes were evident in the Bitter Lake National Wildlife Refuge: deep sinkhole, riverine, and marshland morphotypes. Alternatively, connectivity between a deep sinkhole and marshland habitat in the Bottomless Lakes State Park appeared to produce non-extreme body shapes with little variation, suggesting gene flow mitigates morphological divergence. Results from this study highlight that disruption of gene flow in metapopulations can spur divergent evolutionary trajectories in isolated populations. For species with conservation concern, like C. pecosensis, it is not clear if re-establishing gene flow would be beneficial or detrimental for populations that are potentially adapted to their local environments.

Although it flows through regions of northwestern California that are thought to be relatively well watered, the Eel River is increasingly stressed by drought and water withdrawals. We discuss how critical threshold changes in summer discharge can potentially tilt the Eel from a recovering salmon-supporting ecosystem toward a cyanobacterially degraded one. To maintain food webs and habitats that support salmonids and suppress harmful cyanobacteria, summer discharge must be sufficient to connect mainstem pools hydrologically with gently moving, cool base flow. Rearing salmon and steelhead can survive even in pools that become isolated during summer low flows if hyporheic exchange is sufficient. But if the ground water discharge that sustains river flow during summer drought drops below critical levels, warm stagnant conditions will kill salmonids, and cyanobacteria will thrive. Challenges and opportunities for restoring the Eel and increasing its resilience to climate extremes, water diversions, and excessive loading of fine sediments point toward exploring how land use and terrestrial vegetation affect delivery from uplands of water, heat, sediments, solutes, organic matter, and organisms—in ways that either heal or damage rivers.