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The Guadalupe Bass, Micropterus treculii is endemic to the Hill Country region of central Texas, US, and its entire native distribution is within Texas, including portions of the Brazos, Colorado, Guadalupe, and San Antonio River basins. Currently, the genetic integrity of Guadalupe Bass populations are threatened by hybridization with introduced, nonnative Smallmouth Bass, M. dolomieu. Species-isolating mechanisms (or lack thereof) are not well understood for these two species. To identify potential mechanisms influencing hybridization in Guadalupe Bass populations, our objectives were to characterize: (1) spawning season and duration, (2) nesting habitat, (3) courtship behaviors (including color pattern changes), and (4) parental care pattern. The reproductive ecology (spawning season, nest sites) and behavior (courtship, parental care) of Guadalupe Bass were found to be similar to what has been reported in Smallmouth Bass, possibly contributing to continued potential for hybridization. Guadalupe and Smallmouth Bass share 12 reproductive behaviors and similar color patterns during courting and spawning interactions. This study is the first to report an individual male Guadalupe Bass simultaneously courting and spawning with two to four females in one nest, suggesting the need for further investigation of links between hybridization potential, sex ratio and population structure in Guadalupe Bass. We recommend investigation of female mate choice and sexual competition comparing Guadalupe Bass and Smallmouth Bass. Additionally, future conservation efforts should focus on nesting habitat in existing pure strain Guadalupe Bass populations.
Conservation of lotic fishes requires consideration of complex patterns among a changing mosaic of fish assemblage structure at multiple spatial scales. Studies have demonstrated the influence of localized competition and predation among stream fishes, but researchers have been largely unable to determine to what extent interspecific interactions act to control fish assemblage structure. Recent declines to geographic range and abundance of Plains Topminnow (Fundulus sciadicus (Cope)) have been anecdotally attributed to altered fish assemblages and potential competitive or predatory associations; however, important species interactions have yet to be identified. Variation among fish assemblage structure at 473 locations known to historically support Plains Topminnow was described in Nebraska to demonstrate the role of assemblage dynamics in regulating species occurrence. Nonrandom patterns of fish assemblage composition in terms of Plains Topminnow persistence were apparent statewide, and multiple relationships were recognized as regionally influential (e.g., Niobrara River: Largemouth Bass Micropterus salmoides (Lacépède)). Strong correlations were described relating Plains Topminnow extirpation to nonnative species establishment (Common Carp Cyprinus carpio (Linnaeus), Western Mosquitofish Gambusia affinis (Baird and Girard)), and several potential predatory (Esocidae, Channel Catfish Ictalurus punctatus (Rafinesque)) or competitive interactions (Western Mosquitofish, Bluegill Lepomis macrochirus (Rafinesque), Sand Shiner Notropis stramineus (Cope), Red Shiner Cyprinella lutrensis (Baird and Girard)) were identified. Positive relationships are attributed to similar reliance of particular abiotic conditions (Emerald Shiner Notropis atherinoides (Rafinesque)) or habitat types (Gasterosteidae, Green Sunfish Lepomis cyanellus (Rafinesque), Iowa Darter Etheostoma exile (Winn)). Other identified species will require research to elucidate potential biotic interactions with Plains Topminnow. Resultant models are hypothesized to reflect biotic processes, and thereby provide analytical insight into the long-term influence of fish assemblage structure on a rare species. Identified relationships provide preliminary recognition of potentially important interspecific interactions involving an unfamiliar species from which further hypotheses can be evaluated to ascertain casual relationships.
Silver Shiners (Notropis photogenis) were monitored with underwater videography, captured and measured, and their habitat was characterized from 38 locations in an urbanized fragment of the Grand River, Ontario, from 2006 to 2015. Cobble was the most frequently used substrate type (44.6% of observations) in heterogeneous transitional habitat near backwater pools and areas adjacent to deep runs. Population size structure and qualitative growth patterns suggested rapid growth during the first 2 y after hatching (n = 439). The largest fish captured was 143 mm total length, which is a new Canadian record and tied the world record from Tennessee. Spawning was not directly observed, but gamete evidence suggested it took place from early to mid-June when the water temperature was approximately 24 C. Underwater video monitoring revealed schools of Silver Shiners migrating upstream during late afternoon and evening in October/November presumably to overwintering areas. Silver Shiners were located near known sources of groundwater seepage in 92% of observations. This association requires further investigation to determine if groundwater represents critical habitat that facilitates persistence of Silver Shiner populations in urbanized rivers with notoriously poor water quality.
The Illinois River historically provided high-quality habitat for a variety of migratory birds but sedimentation, management for commercial navigation, and increasing hydrologic variability have contributed to reductions in aquatic vegetation and naturally occurring foods for waterfowl. Cover of aquatic vegetation within the Illinois River Valley (IRV) declined during the 1950s, and it has not recovered in its historical range. The Dresden and Starved Rock reaches of the Illinois River, unlike other reaches in the IRV, still retain aquatic macrophytes in the main channel and connected backwater wetlands. To determine energetic carrying capacity of seeds and tubers for waterfowl in the upper Illinois River, we collected benthic core samples from random locations throughout the Dresden and Starved Rock reaches in falls 2013–2014. All sampling locations (i.e., main channel and connected backwater wetlands) had low mean density of seeds and tubers (<175 kg/ha) and duck energy days (DED; <1200 DED/ha) relative to other managed wetlands and backwater wetlands in the region. Greatest seed density occurred in the Dresden reach in 2014 (109.0 ± 85.7 kg/ha; n = 30) and 2013 (44.4 ± 10.7 kg/ha; n = 28), followed by the Starved Rock reach in 2014 (13.7 ± 35.7 kg/ha; n = 30). Within the Dresden reach, seed and tuber densities in the Des Plaines River were similar (95.8 ± 64.2 kg/ha; n = 40) to those in the Kankakee River (37.7 ± 14.0; n = 18), despite commercial barge traffic and channel maintenance in the former. However, seed and tuber densities from throughout the upper Illinois River were likely near or below levels required for ducks to forage profitably and value as foraging habitat for dabbling ducks seeking seeds and tubers may be limited. Conservation planners should prioritize restoration and enhancement of disconnected waterfowl management areas with water management capabilities to maximize growth of aquatic vegetation for quality waterfowl habitat in the Illinois River and other Midwestern river systems.
As the trend towards urbanization continues, natural areas near dense human populations can be impacted by development, and increased recreational use of these natural areas may increase disturbance of wildlife. Many waterbirds use areas that are generally subject to elevated levels of human disturbance and some species consequently are often considered highly susceptible to disturbance. In 2013 and 2014 we assessed the effects of human recreational disturbance on Green Herons (Butorides virescens) through the use of focal observations at sites of varying disturbance. We collected behavioral data (n = 154 observations) along the headwaters of the San Marcos River located in Central Texas. We built 15 linear regression models to assess the potential influence of human disturbance as well as potential influence of habitat differences between study sites on each of five response variables (four foraging behaviors plus foraging efficiency). Using Akaike's Information Criterion model selection, we found that differences in foraging habitat provided the best explanation for the observed variation in four of the five response variables measured. Our results suggest Green Heron foraging behavior was influenced more by habitat than human disturbance events; however, foraging efficiency was the highest in least disturbed site. It is possible these birds have become habituated to disturbance (i.e., more tolerant of human presence) and perhaps now only modify their foraging technique in order to maximize their foraging efficiency to suit a specific location. These findings are noteworthy because it is important to distinguish cases where human disturbance impacts a species from cases where human disturbance has less of an effect.
Oak savanna, once widespread across central North America, has functionally vanished from most of its range due to land conversion or fire suppression and subsequent afforestation. Savanna-associated bird species have exhibited population declines as a result. One of the few areas containing remnant oak savanna is the vast Cross Timbers ecoregion of the south-central Unites States. Previous research in the Midwest showed some bird species exhibited higher rates of nest success (i.e., lower predation of eggs and nestlings) in restored savannas than in closed-canopy forests. Our objective was to quantify patterns of avian nest success across a gradient from open-canopy oak savanna to closed-canopy forest in the Cross Timbers ecoregion of southeastern Kansas. Daily nest survival rates for four common bird species—mourning dove (Zenaida macroura), yellow-billed cuckoo (Coccyzus americanus), brown thrasher (Toxostoma rufum), and northern mockingbird (Mimus polyglottos)—were modeled against covariates of woodland structure along the habitat gradient. Tree density and canopy cover had no significant effects on daily nest survival rate, but daily survival rates of brown thrasher and northern mockingbird nests showed positive trends with increasing shrub density. We expect restoration of oak savanna habitat would have little effect on nest survival of some common bird species in the naturally heterogeneous Cross Timbers ecoregion.
In Ohio Euro-American settlement in the late 18th and early 19th centuries subjected forests to large scale disturbances, including widespread clearance. In the subsequent two centuries, some of this land has reforested. To describe changes in forest composition since settlement, we used archival maps of U.S. Public Land Survey records to characterize forest composition just before large scale Euro-American settlement in 27 Ohio counties. We then compared this with modern composition patterns from the U.S. Forest Service's Forest Inventory Analysis. Presettlement forests displayed strong spatial structure and regional differentiation. Counties in northwest Ohio were dominated by beech (Fagus grandifolia; mean relative abundance: 26.9%), whereas southeast Ohio counties were dominated by oaks (Quercus spp.; 50.1%). Modern forests, however, had weaker spatial structure and were dominated by oak species in both regions (24.0% and 22.4%, respectively). Overall, we found a decrease in previously dominant species and homogenization across the state. Partial Mantel tests indicated modern forest composition is more closely correlated with modern land use variation than environmental variables, suggesting that forest composition now is driven primarily by land use. Understanding factors influencing forest composition can inform projections of forest response to modern global change, including climate change and land use conversions.
Recently, the range of the woodland deer mouse (Peromyscus maniculatus gracilis) in Michigan's Lower Peninsula (LP) has contracted simultaneously with the increasing abundance of the white-footed mouse (Peromyscus leucopus). The known LP range of P. m. gracilis has shrunk to two areas, one in Cheboygan/Otsego Counties and another in Alpena County. We used a Geographic Information System habitat analysis to predict where P. m. gracilis could be found between those areas and trapped at selected locations. P. leucopus was present at every location, but the known range of P. m. gracilis had expanded only slightly, and remains as two separate fragments. We analyzed 11 microsatellite loci for all P. m. gracilis to investigate the genetic structure of their remaining LP populations. Genetic diversity was high, FST values were low, and there was no evidence of recent bottlenecks, indicating that LP populations of P. m. gracilis once had extensive gene flow across the entire region. However, trapping data, assignment tests, and the distribution of private alleles show that the Alpena population is genetically distinct. We suggest the discordance between analyses could be a sensitive indicator of a population beginning to be affected by isolation, allowing genetic effects of range contractions to be detected in small mammal populations before they become seriously endangered.
We explored the diversity of small mammal communities in highway roadsides and medians. We captured small mammals along 15 km of Interstate Highway 70 in Illinois U.S.A. using Sherman traps (2866 trap nights), and evaluated the animals perceived risk of predation using the Giving Up Density (GUD) technique, in both the medians and roadsides. Small mammals in roadsides are potentially exposed to more mammalian and avian predators from the surrounding landscape. Therefore, we expected small mammals in roadsides would perceive a greater risk of predation (as indicated by GUDs) than small mammals in medians. Median trays were three times more likely to be foraged, yet we found no difference in the GUDs between medians and roadsides, indicating that small mammals in these two habitat types may be equally fearful of predators. We captured seven species of small mammals, which is comparable to species richness in nearby nature preserves. Density of mammals in the median was double that found in the roadsides. Community structure (relative number of individuals of each species) differed between roadsides and medians. Differences in species density and composition are likely due to greater connectivity of the roadsides to the surrounding landscape. Ultimately, roadsides, and especially medians, along highways need to be given more consideration as potentially high quality habitat for small mammals.
Although studies often focus on the direct effects of invasive species on native taxa, invasive species may also alter interactions among native species. For example Solenopsis invicta, the red imported fire ant, may directly alter native seed survival by consuming seeds, but also indirectly alter seed survival, by altering the abundance and/or behavior of native granivores. We tested the effects of invasive S. invicta on rodent and arthropod granivory by quantifying seed removal from seed depots that differed in granivore access (arthropods and rodents or arthropods only) and distance from an S. invicta mound (0.1 m or 4.0 m). We hypothesized the effect of S. invicta on native granivores would be stronger at depots located near (0.1 m) a mound than at depots located 4.0 m from a mound. Use of two different seed species (Rubus cuneifolius and Prunus serotina) allowed us to evaluate the consequences of S. invicta for small-seeded plant species consumed by both arthropods and rodents (R. cuneifolius) as well as for large-seeded species that can only be consumed by rodents (P. serotina). We found overall removal of P. serotina was low, regardless of seed depot location or exclosure type. Near S. invicta mounds, the removal of R. cuneifolius was also low, with no difference between depots that allowed or excluded rodents. In contrast, removal of R. cuneifolius by arthropods 4.0 m from a mound was nearly twice that of removal next to a mound but only when rodents were excluded. Our results indicate S. invicta may create hotspots of granivory by native arthropods in the areas between S. invicta mounds, but these effects may not extend to large-seeded plants that are consumed by rodents. By influencing seed survival as a function of plant species and proximity to a mound, nonnative S. invicta generates heterogeneity in native seed survival, which may affect plant community composition.
Populations of invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis), collectively known as “Asian carp,” are growing rapidly in Illinois and may make up a large fraction of available prey for river otters (Lontra canadensis) in larger waterbodies. Our goals were to assess the frequency of Asian carp in otter diets and compare the frequency of occurrence of prey groups (fish, crayfish, and amphibians) in otter diets between land cover types and seasons. We searched for Asian carp otoliths and pharyngeal teeth, as well as parts of other fishes, crayfish, and amphibians in 155 otter scats collected from 43 stream sites in central and southern Illinois during January−April 2013 and 2014. Consistent with previous studies, fish and crayfish were primary prey items for otters, followed by amphibians. The proportion of crayfish increased from January−February to March−April, but the occurrence of the other prey types remained similar between those periods. Land cover type did not influence frequency of occurrence of prey types. Asian carp pharyngeal teeth and otoliths occurred in four (2.6%) scat samples, two from sites where Asian carp were not previously confirmed to be present. This is the first direct confirmation of Asian carp in the diet of wild river otters. Otoliths and pharyngeal teeth provided effective structures for identifying fish species in otter diet.
Population studies are widely used in conservation and management efforts, but acquiring necessary data sets can be difficult. Convenience sampling or camera monitoring may result in biased outcomes, while explicit approaches such as genetic analysis may be impractical due to cost and time. Traditional mark recapture methods are frequently intrusive and pose risk to both animals and handlers that could lead to mortality. These factors highlight the need for a simple, inexpensive, and non-invasive approach to assess species density. One possible technique which addresses these issues is track plate footprinting. We collected raccoon (Procyon lotor) footprints and examined the ability to distinguish individuals by their metacarpal pads from a 225 ha reserve. The probability of identity (PID) for back right feet ranged from 5.72 × 10−9 – 6.71 × 10−12 and from 3.34 × 10−8 – 3.55 × 10−10 for the back left feet, indicating that it was unlikely any two raccoons shared the same papillae pattern. The minimum number of raccoons known to be alive was estimated to be 12–17 individuals depending upon the foot and scale of resolution used, with estimates from program the Capture ranging from 34–38 raccoons. Our results show that track plate footprint can be used to unambiguously identify individual raccoons, may be useful in mark-recapture studies, and is likely to be applicable to other species with large pads.