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High-severity forest fires are increasing in large areas of the southern and western United States as the climate becomes warmer and drier. Natural resource managers need a better understanding of the short- and long-term effects of wildfires on lizard populations, but there is a paucity of studies focused on lizard-wildfire relationships. We used a before-after, control-impact (BACI) sample design to assess the response of three lizard species—Six-lined Racerunner (Aspidoscelis sexlineata), Prairie Lizard (Sceloporus consobrinus), and Little Brown Skink (Scincella lateralis)—to high-severity wildfires that occurred in the Lost Pines Ecoregion, Texas, USA. Specifically, we analyzed monitoring data collected across 17 trapping sessions from spring 2008 to spring 2013 using stratified N-mixture models to estimate trends in lizard abundances, while accounting for environmental parameters that might influence lizard detectability. We found no evidence of a fire-induced change in abundance for any of the lizard species we studied, but there was an increase in detectability of A. sexlineata following the wildfires. Detectability of A. sexlineata and S. lateralis increased with air temperature, detectability of S. consobrinus decreased with precipitation, and detectability was related to Julian day for all three species. Mean detection probabilities were low (<0.1), suggesting capture-mark-recapture methods at a subset of sample units should be implemented to derive more accurate estimates in future monitoring efforts. Our results provide quantitative evidence of the short-term effects of high-severity wildfires on three widely distributed lizard species. Given the wildfires did not result in decreased lizard abundances, managers should minimize their vehicle footprints off of roads during post-wildfire habitat restoration to avoid soil compaction and the potential for direct mortality.
Most temperate-climate lizards become inactive during the winter months of each year. As temperatures drop, they must find appropriate overwintering microhabitats to avoid lethal surface temperatures and/or thermoregulate. The environmental variables that characterize such microhabitats and the cues that lizards utilize to assess them are a critical but understudied component of their natural history. While many studies of overwintering site selection focus on temperature, other factors constituting microhabitats (e.g., surface structures, substrate) may play a role in site selection. We used the Jacky Dragon (Amphibolurus muricatus), an Australian agamid lizard, to test for preference of using various cover types (leaf litter, open sand, sticks, rocks) for overwintering as well as the consequences of cover type selection. Jacky Dragons preferred overwintering beneath leaves compared to other structures, and this choice was associated with growth during winter, but not with survival. Our study highlights the potential importance of cover structures in overwintering site selection, suggests that midwinter activity may be common in Jacky Dragons, and calls for further study of the winter ecology of temperate-climate lizard species.
A recently described species of pupfish, Cyprinodon desquamator, was previously reported to have rapidly and sympatrically evolved lepidophagy (scale eating) on San Salvador Island, The Bahamas. Although lepidophagy is known from a variety of marine and freshwater fish species, the effects of this mode of predation on prey species have not previously been characterized. By examining scale regeneration rates in lakes with and without the scale-eating predator, we provide evidence suggesting that C. desquamator imposes high predation pressures on sympatric fishes, which supports the hypothesis that the feeding behavior of C. desquamator may have acted as an important driver of pupfish species divergence on San Salvador Island.
The subfamily Pteroinae, a widely distributed Indo-Pacific group, contains five genera and 27 species, including the well-known, invasive Red Lionfish Pterois volitans and Devil Firefish P. miles. Other species are imported in the marine ornamental trade; however, basic biological information for most is scarce or absent, which can make the determination of invasion risk difficult. Thermal tolerance is an important physiological characteristic which can limit the distribution of non-native fishes. Here we assess the thermal tolerances of two commonly traded lionfishes in the ornamental pathway, Shortfin Turkeyfish Dendrochirus brachypterus and Zebra Turkeyfish Dendrochirus zebra, using chronic lethal methodology. Average chronic lethal minimum temperature was 11.8°C for Shortfin Turkeyfish and 14.7°C for Zebra Turkeyfish, compared to 10.0°C for Red Lionfish. Our results suggest a narrower potential distribution in the Atlantic for both species if they were to establish outside captivity. These findings are useful for future risk assessment which can inform regulatory actions, if necessary, and ultimately mitigate deleterious introductions.
A provisional model of survival and demography in two populations of the salamanderDesmognathus ocoeein the Cowee and Nantahala mountains of North Carolina was derived from existing data on growth, metamorphic timing, age at first reproduction, and fecundity. The model assumed stationary populations with stable age distributions (R0= 1.0,r =0), wherein observed ages at first reproduction in females were equal to optimal ages. Survivorship was partitioned into pre- and post-metamorphic phases, i.e., egg/larval survival and juvenile/adult survival. Premetamorphic survival estimates were fitted to the model to meet the requirement thatR0= 1.0. Equivalence of optimal and observed age at first reproduction in females, as proposed, could reflect synergistic tradeoffs between (1) growth and reproduction, and (2) mortality and reproduction. The two populations show extreme similarity in life history and demography, in contrast to differences between the Cowee and Nantahala desmognathine assemblages.
The genus-level taxonomy of the New World racers and whipsnakes (ColuberandMasticophis) has long been contentious regarding whether the two genera are mutually exclusive clades. This argument is based on morphological characters and largely single-locus analyses. Herein we examine the phylogenetic history of this group using multi-locus data in a coalescent framework, where paraphyly ofMasticophiswould result in support for the recognition of only a single genus (Coluber) for these species. We sample all currently recognized species and incorporate broad geographic sampling for the more widespread species groups to explore biogeographic patterns across North America. Our analyses suggest thatMasticophisis monophyletic with respect toColuber constrictor, albeit with low support. These results also demonstrate that there is undescribed cryptic diversity in this group, and we underscore additional avenues of study to further delimit unrecognized species in this clade. The biogeography of the island endemic,Masticophis anthonyi,is discussed with respect to what is known about other codistributed vertebrates. Lastly we provide an overview of the history of the arguments for or against the use of the generic nameMasticophisand suggest its continued use.
Predators demonstrate context-dependent foraging behaviors to dynamically and successfully track prey and can use multiple cues in this process. In squamate reptiles (snakes and lizards), chemical signals from prey significantly influence predatory behavior, especially substrate and airborne cues. In this study, we examined behavioral variation in rattlesnakes (Crotalus oreganus) during strike-induced chemosensory searching (SICS), a sterotyped complex of behaviors seen in squamates. Rattlesnakes can use both substrate and airborne chemical cues during SICS, but we sought to determine the changes during SICS when either substrate, airborne, or air-deposited chemical cues were the only types available to snakes in a Y-maze. We hypothesize that these cues represent the spectrum of chemical information available in the natural environment. We also modified scoring of choice in the Y-maze by deriving a choice penalty score, a reflection of how extensively the snake explored the unscented arm of the maze. In the presence of substrate trails, rattlesnakes relocated prey fastest, had highest rates of tongue-flicking, and received the lowest choice penalty scores during SICS. Airborne chemical cues enabled successful relocation, but rattlesnakes took longer to relocate prey, increased the frequency of many searching behaviors, and more extensively explored the Y-maze (more negative choice penalties). When air-deposited cues were the only type available, rattlesnakes took the longest to choose an arm, had the lowest rates of tongue-flicking, and backtracked most often. We suggest that as prey odor becomes more dilute, rattlesnakes demonstrate behavioral plasticity in SICS to preserve their ability to relocate prey.
The “Lembeh Frogfish” or “Ocellated Frogfish,” a distinct antennariid, known for many years, especially among members of the dive community, and suggested by some to represent an undescribed species, is identified asNudiantennarius subteres(Smith and Radcliffe). Unique in several ways—including reduced dermal spinules, the body appearing naked; illicium short, about half the length of the second dorsal-fin spine; second dorsal-fin spine unusually long and narrow, without a posterior membrane; pectoral lobe narrow, somewhat detached from the body; membranes between the rays of the paired fins deeply incised; and all pelvic-fin rays simple—the species is redescribed and figured below. Morphological and molecular analyses indicate a close relationship with the Sargassumfish,Histrio histrio.
A microscopic morphological feature (eosinophilic granulocytes, eG) was recently detected in the gonads of two species of economically important and broadly distributed, tropical Indo-Pacific eteline snappers, primarily in the ovaries of mature but reproductively inactive female Ruby SnapperEtelis carbunculus. Eosinophilic granulocytes have been known for more than a century to occur in diverse tissues (e.g., liver, kidney, gill, gonad) of a variety of freshwater and marine teleosts and have usually been recognized as bio-markers of immune response to environmental toxins or pathogens. Until now, they have been mostly overlooked as indicators of natural atresia in gonads and evidence of prior reproductive function in healthy fishes. The eG feature is herein suggested as a bio-marker of sexual maturity that might be useful when combined with an existing suite of largely qualitative markers of maturity in mature females that lack direct signs of maturity such as atretic yolked oocytes and post-ovulatory follicles. This marker may reduce the present uncertainty in distinguishing mature but inactively reproducing females from immature females in studies of fish and fisheries biology, specifically when estimating body size at sexual maturity.
We examined the testicular histology of 32 adult malePseudobranchus axanthuscollected at Rainey Slough (Glades County), Florida, during 1974–76. The process of spermatogenesis was evident throughout all regions of the testes and appeared to occur year-round. The testes contain numerous, spherical-to-oblong testicular lobules that vary greatly in size. Unlike all other salamanders, which exhibit cystic spermatogenesis along with a caudo-cephalic wave of maturing cell types (leading to spatial and temporal segregation of germ cells), spermatogenesis inP. axanthuslacks testicular cysts. Instead, the testicular lobules possess an assortment of different spermatogenic cell stages, all arising from primary spermatogonia through mitotic and meiotic divisions, thus creating a germ cell/Sertoli cell syncytium along the lobular epithelium. Secondary spermatocytes then detach from the lobular epithelium and from their accompanying Sertoli cells and undergo spermiogenesis within the lumen. We propose naming this new type of germ cell development non-cystic lobular spermatogenesis. Upon maturation, sperm travel from the lobular lumen into a longitudinal testicular canal via an intratesticular duct. The testicular canal conveys sperm to about 15 vasa efferentia, which then connect to genital renal capsules. Sperm move through the renal tubules and eventually reach the Wollfian duct. This duct transports sperm to the cloaca.
Many reptiles and amphibians are gaining recognition as harmful invaders, highlighted by well-known examples such as the Brown Tree Snake (Boiga irregularis), Cane Toad (Rhinella marina), American Bullfrog (Lithobates catesbeianus), and Burmese Python (Python molurus bivittatus). In 2003, an introduced population of Seal Salamanders (Desmognathus monticola) was found in Spavinaw Creek, within the Ozark Plateau of northwest Arkansas. Genetic evidence confirmed an introduction from northern Georgia. Very little is known about the status of this non-native population; thus, the objective of this study was to assess the current distribution and abundance of non-nativeD. monticolaalong Spavinaw Creek. We conducted repeated, low-intensity visual surveys along the 30 km extent of Spavinaw Creek in Arkansas and used a hierarchical Bayesian analysis to model the occupancy response ofD. monticolaand five native salamander species relative to river mile and habitat covariates. We also conducted a short-term closed capture-mark-recapture study to estimate abundance ofD. monticolaat the original collection site on Spavinaw Creek. We found a clear geographic pattern of distribution ofD. monticola, with individuals found throughout the upper 10 km of Spavinaw Creek headwaters, but no clear habitat associations. Estimated abundance ofD. monticolawas extremely high—14.5 individuals and 50 g wet biomass per m2. Our results reveal that introducedD. monticolaare much more widely distributed than previously recognized and occur at high densities, suggesting that this recent invader could negatively affect ecosystems of Spavinaw Creek and surrounding watersheds in the Ozark highlands.
Color polymorphism in animals often reflects discrete intraspecific variation in suites of traits linked with survival and reproductive success, as well as an ability to exploit diverse habitat types. Given those considerations, it has been hypothesized that color polymorphic species may be better able to withstand broad-scale environmental disturbances compared to monomorphic taxa. An assumption underlying this hypothesis is that morphs differ in their responses to the consequences of a disturbance. We test whether two color morphs of the Ornate Tree Lizard (Urosaurus ornatus) differ in their physiological responses to a likely outcome of a habitat disturbance, food limitation. We subjected blue and yellow morphU. ornatusto one of two feeding treatments (control [fed every other day] and food-limited [fed every five days]) and monitored their changes in body mass and stamina capacity for the next four weeks. We found that in general, food-limited males lost mass and had reduced stamina over time. Although yellow males had consistently greater stamina than blue males, the temporal patterns of change in stamina, as well as body mass, were not morph-specific. Our findings suggest that at least one aspect of a species' coping tactics, in terms of energy-allocation decisions, is similar for these twoU. ornatusmorphs. Despite this overlap, the consistently lower stamina capacity of blue males in this study, coupled with data from ongoing field work in our lab, suggest that this morph may nonetheless suffer greater long-term fitness costs than yellow males in disturbed environments.
The Redband Darter,Etheostoma luteovinctum, is a benthic headwater fish species found in the Caney Fork and Stones rivers (Cumberland River) and the Duck and Elk rivers (Tennessee River) of central Tennessee. Phylogenetic analyses of 2601 amplified fragment length polymorphisms (AFLPs) were used to assess the relationships among populations and identified two genetically distinct lineages of Redband Darter. One lineage is comprised of populations in the Duck R., Elk R., Middle Fork Stones R., West Fork Stones R., and Hickory Creek of the Caney Fork River, while the other lineage is confined to the remainder of the known localities in the Cumberland R. drainage. As clades were not restricted to drainage or system boundaries, patterns suggest system and drainage transfers. Additionally, morphological variation was examined among populations using standard meristic data and nuptial male color and pigmentation characteristics. Although some morphological traits varied between the two clades, members were not clearly diagnosable using morphology. Taxonomic recognition is not proposed for the two identified clades; however, each clade should be recognized as an evolutionarily significant unit and regarded as such in future conservation efforts. Furthermore, this study demonstrates the utility of AFLPs to assess genetic variation and phylogenetic relationships for species-level taxonomic or phylogeographic studies.
The effects of contemporary logging practices on headwater stream amphibians have received considerable study but with conflicting or ambiguous results. We posit that focusing inference on demographic rates of aquatic life stages may help refine understanding, as aquatic and terrestrial impacts may differ considerably. We investigated in-stream survival and movement of two stream-breeding amphibian species within a before-after timber harvest experiment in the Oregon Coast Range. We used recaptures of marked individuals and a joint probability model of survival, movement, and capture probability, to measure variation in these rates attributed to stream reach, stream gradient, pre- and post-harvest periods, and the timber harvest intensity. Downstream biased movement occurred in both species but was greater for Coastal Tailed Frog (Ascaphus truei) larvae than aquatic Coastal Giant Salamanders (Dicamptodon tenebrosus). ForD. tenebrosus, downstream biased movement occurred early in life, soon after an individual's first summer. Increasing timber harvest intensity reduced downstream movement bias and reduced survival ofD. tenebrosus, but neither of these effects were detected for larvae ofA. truei. Our findings provide insight into the demographic mechanisms underlying previous nuanced studies of amphibian responses to timber harvest based on biomass or counts of larvae.
We assessed the effects of short-term, naturally oscillating, climate variation on Crawfish Frogs (Lithobates areolatus), a long-lived member of the family Ranidae. Our data demonstrate 1) no relationship between drought conditions (high temperatures, low precipitation) and either breeding onset (phenological shifts) or breeding peaks; 2) no relationship between drought and adult survivorship (although there were trends; both females and males experienced their lowest survivorship estimates during the wettest years, a contrary finding related to crayfish burrow occupancy); 3) a strong relationship between drought and breeding duration; 4) a strong, inverse correlation between drought and body condition in both females and males; and as a result, 5) a relationship between drought and fecundity with potentially serious demographic consequences. If we assume that the mass of an individual egg remains constant under various climate conditions—i.e., that a reduction in egg mass equals a reduction in egg number not egg size—the effects of drought may be severe. Our estimated average difference of 2,647 eggs produced by individual females between wet and dry years translates into an estimated loss of 137 breeding adults recruited into this population following droughts, compared with wet year recruitment.
The River Redhorse (Moxostoma carinatum) is a large riverine catostomid that has experienced substantial declines across much of its historic range. Conservation of this species is hindered by a lack of knowledge about many aspects of its life history. In order to better understand the seasonal movements and habitat associations of this species, adult River Redhorse were captured from the Kankakee River, Illinois, implanted with radiotransmitters, and tracked throughout an annual cycle. Habitat data were recorded at all locations where radio-tagged River Redhorse were located. Eight of ten individuals displayed fidelity to a relatively short length of river (total range ≤ 8.7 km), whereas two individuals exhibited substantially greater movements (total range ≥ 23.1 km). Movement patterns of River Redhorse varied across seasons, with the largest ranges and highest displacements occurring during spring, and the smallest ranges and lowest movement rates occurring during summer. River Redhorse predominately occupied deep runs (>1.5 m) with moderate to swift currents (>0.4 m/s) over gravel, cobble, or boulder substrates. Habitat use differed among seasons, with River Redhorse occupying faster current velocities during winter and spring than during summer and fall, and using deeper water over smaller substrates in winter than during summer. Conservation of River Redhorse populations may depend on watershed-scale conservation practices to safeguard the mosaic of habitats the species associates with and maintaining viable pathways for movement among these habitats across seasons.
Anthropogenic disturbance has led to the loss of biodiversity, altering ecosystem processes and decreasing stability. Top predators have been disproportionately affected by this degradation. Functional complementarity via niche overlap is one mechanism by which ecosystem processes may be maintained in the absence of a top predator. Aquatic ecosystems have shown a decline in top predators such as salmonids, but few studies have addressed the functional complementarity of alternative predators. In beaver ponds in the western U.S., Western Tiger Salamanders (Ambystoma mavortium) often become the top aquatic predator in the absence of fish, yet no previous studies have explored their trophic ecology. We evaluated this knowledge gap and used criteria including population size structure, diet, and stable isotope analysis to investigate the functional complementarity of a degradation tolerant species, the Arizona Tiger Salamander (A. m. nebulosum),compared to the native but extirpated salmonid top predator, Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Field data for tiger salamanders and published accounts of various salmonid species suggested that, although both species are characterized by size-structured populations with ontogenetic shifts in a generalist diet, the trophic position ofA. m. nebulosumis lower than reported values for large salmonids. This lower trophic positioning suggests that salamanders are likely to be functionally complementary with only the smallest size classes of salmonids. These results support previous work suggesting that functional complementarity exists under a narrow range of environmental conditions, which may limit the degree to which degradation-tolerant species can maintain communities.
The genusAphyoditehas a complex taxonomic history. It was described as monotypic, and the only diagnosis provided was “anAphyocharaxwith a scaled caudal fin”. After the description, the genus was revised twice, but some morphological inconsistences remained, pending a proper morphological analysis. Currently,Aphyoditeis a member of Aphyoditeinae and can be distinguished from all the other representatives of this subfamily by having the first infraorbital with a conspicuous sensory canal not reaching the anterior edge of the bone. During the revision of the genus, two new species were found:Aphyodite apiaka, new species, from the Rio Madeira basin, that can be diagnosed from its congeners by the length of the first infraorbital sensorial canal, which is longer than half length of bone; andAphyodite tupebas, new species, from the Rio Solimões basin, that can be diagnosed from its congeners by the possession of only conical teeth in the premaxilla.
The regulation of body temperature (Tb) is important for energy acquisition in ectotherms but may be challenging and costly. We studied the thermal biology of a north temperate population of Midland Painted Turtles (Chrysemys picta marginata) in a small pond in central Michigan. Cycling of mean daily body temperature (Tb) began as early as March and continued through October. The thermoregulatory setpoint range was 25–31°C, and turtles largely maintained Tb near or within the Tset range throughout the day between May and September. Mean hourly Tb was slightly ( 0.5°C) higher on sunny days when compared to cloudy days. Turtles had relatively low investment in thermoregulation during the fall months potentially as an energy conservation measure prior to hibernation. Thermal exploitation values (Ex) indicated that our turtles spent as much, or more, time within the Tset range than individuals in other north temperate Painted Turtle populations and other reptile species studied to date, which was most likely due to the relatively high thermal quality of our aquatic environment. We did not find differences between males and females in terms of thermal exploitation, which suggests little or no differences in thermal energy needs that might be associated with potential energetic allocations to reproductive activities (e.g., ovarian development or mate location in males).
We studied a population of E. atkinsi in eastern Cuba and describe post-reproductive variables (clutch size, eggs, embryonic development, and hatchlings) along with gonadal ultrastructure using microscopic techniques (LM and TEM). We found that most eggs had an advanced stage of embryonic development, with embryos having elongated limbs, noticeable blood vessels, nubs of digits, and in some cases expanded toe discs. In all clutches, we observed adult males or females next to the oviposition sites, suggesting biparental care during embryonic development. Snout–vent length versus oviducal eggs were highly correlated, and CT-scan images of gravid females highlight the number and disposition of the oviducal eggs below the axial skeleton and pelvic girdle. Hatchling coloration was similar to adults, but we also observed highly polymorphic color variation. We describe spermatogonia, spermatocytes I–II, spermatids, and spermatozoa. The mature sperm has an elongated head and tail with an undulating membrane, a structure used in phylogenetic reconstructions. Cross-sectional undulating membrane consists of an axoneme with an associated juxtaxonemal fiber, an axial sheath, and an axial fiber. In the ovary, oogonia are located in a peripheral germinal nest, surrounded by follicle cells. During folliculogenesis, two stages of development were observed: pre-vitellogenesis and vitellogenesis. Our results indicate that E. atkinsi displays remarkable reproductive adaptations and can be used as a model for other endemic Cuban species.