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Plants commonly host multiple microbial symbionts that regulate productivity and other ecosystem processes, yet multi-symbiont interactions within hosts are rarely examined. We evaluated how the presence of aboveground Epichloë fungal endophytes (E , symbiotic, and E−, endophyte experimentally removed) altered belowground colonization by arbuscular mycorrhizal fungi (AMF) in three grass species in a common environment. We sampled from E and E− populations of woodland bluegrass (Poa sylvestris A. Gray), grove bluegrass (Poa alsodes A. Gray), and tall fescue (Schedonorus arundinaceus Schreb.) in long-term experimental plots in woodlands near Nashville, Indiana. Endophyte symbiosis aboveground increased AMF colonization of roots in both Poa species, although this effect was only significant for hyphal colonization in P. sylvestris. Endophyte symbiosis did not significantly alter AMF colonization in S. arundinaceus, in contrast to prior findings for this species. Our results illustrate the effects of Epichloë sp. on AMF cosymbionts are not easily generalizable across plant-endophyte symbiota, even those that co- occur in the same ecosystem.
Understanding the reproductive ecology of stream fishes is critical for their conservation. Nest association is a common reproductive interaction among minnows (Cyprinidae) in which individuals of ‘associate' species spawn in nests of host species. Nest association behavior is nearly obligate for ‘strong' associates, while it is facultative for other species. Facultative associates may begin spawning before host nesting begins and then visit host nests either to continue spawning or to feed. This is particularly evident for Central Stoneroller Campostoma anomalum, which frequently visits nests of host Bluehead Chub Nocomis leptocephalus but also spawns separately. We monitored the reproductive condition (gonadosomatic index, GSI) of minnows at longitudinally-positioned sites in a central Appalachian stream throughout the spring and summer of 2013. We also conducted daily visual nesting surveys to document chub spawning behavior and reproductive interactions that occurred on their nests. We used nonmetric multidimensional scaling (NMDS) to compare weekly GSI patterns of reproductive groups and hypothesized stoneroller GSI would be more similar to facultative associates than chubs. We also used piecewise regression to identify temporal thresholds in GSI (indicating the onset of spawning) in relation to the visually-confirmed onset of chub spawning. NMDS results suggest clear differences in reproductive condition between chubs/strong associates and stoneroller/weak associates. The onset of chub spawning was contained within the GSI thresholds estimate of strong associates but not of other groups. Stonerollers began spawning several weeks before chubs but were documented to be excavating pits on each nest. Paired together, the GSI and behavioral observations suggest stoneroller does not require chub nests for spawning and may exploit nests as a trophic resource if no eggs are contributed. Moreover, these results demonstrate the close reproductive link between some symbiotic species and their hosts that is required for successful reproduction.
The distribution of the Illinois state-threatened Banded Killifish Fundulus diaphanus has remained largely unchanged in Illinois from 1880 to 2000, being restricted mainly to the northeastern corner of the state. One population identified as Western Banded Killifish F. d. menona has remained stable in the glacial lakes region along the southeastern Wisconsin–northeastern Illinois border. Starting in 2001 a second population began to spread and become more common along the Lake Michigan shoreline. From there the population expanded through the Chicago Area Waterway System into the Des Plaines River and eventually the Illinois River. Historical museum specimens from this region are identified as F. d. menona, but recent specimens are identified as hybrids between F. d. menona and Eastern Banded Killifish F. d. diaphanus. Subsequently, a third population appeared in the Mississippi River near the mouth of the Rock River in 2009 and has spread from there. These individuals are also identified as F. d. menona. The rapid expansion of Banded Killifish from Lake Michigan to the Illinois River appears to be an invasion of the Eastern subspecies F. d. diaphanus and the subsequent hybridization with the native Western subspecies. It is unknown where the Banded Killifish in the Mississippi River originated, possibly from populations 160 kilometers upstream or human introductions. As the Illinois River and Mississippi River populations continue to expand their ranges, their ecological impacts are unknown at this time.
Exotic species introduced through the pet trade pose an ecological and economic threat to the Great Lakes region. Trachemys scripta elegans, the red-eared slider turtle, is a globally invasive species already present in the Great Lakes basin whose distribution and potential for spread is poorly known. We assembled a detailed dataset on T. s. elegans occurrence and establishment in the region and created a niche model to assess the potential for the spread of this species under current climate conditions and future scenarios. We found T. s. elegans occurs throughout the Great Lakes basin and suitable area will likely increase from 26% to 39–50% of the entire basin by 2050, with Lake Erie at greatest risk with ∼95% of its total area suitable for T. s. elegans by 2050. These findings highlight the need for further research to assess impacts of T. s. elegans on native species and proactive efforts to prevent its further spread.
Beaver (Castor canadensis) can help to restore wetlands and mitigate the effects of climate change on hydrological regimes in some areas. Therefore, ongoing resource management efforts seek to promote the presence and persistence of beaver populations. The long-term success of such endeavors requires an understanding of what conditions are conducive to sustaining beaver populations, often in landscapes with degraded forest resources. Available information about beaver habitat suitability is largely based on short-term studies in stream habitats that do not consider aquatic plant suitability, even though aquatic plants may comprise over half of beavers' annual diets. In the present study, we assess whether the availability of woody plants, conditions conducive to the availability of aquatic vascular plants (macrophytes), and/or other features of basin morphology are associated with the persistence and density of beaver occupancy in 23 lakes over a 50-y period. We incorporate field-based study that includes all species of macrophytes, to extend previous work that focused specifically on water lily species (Nymphaea spp., Nuphar spp.). Lake perimeter (a function of sinuosity and surface area) and total macrophyte cover were associated with the persistence and density of beaver occupancy in lakes. Each factor independently explained ∼70% (R2adj) of the variation in the persistence of beaver occupancy. Percent cover of floating-leaved macrophytes was a leading predictor of beaver colony density in lakes, independently explaining 72% (R2adj) of the variation. Brasenia schreberi appeared particularly valuable to sustaining beaver in smaller lakes. Several lakes with abundant Brasenia supported high colony densities and long-term colony occupancy. Where feasible, beaver restoration efforts may increase the probability of success by facilitating beaver access to lakes that host key rhizomatous macrophyte species.
Determining the factors that constrain the distribution of a species may have important management and conservation implications. We quantified space use and cover selection of kit foxes (Vulpes macrotis) at the northern periphery of their distribution in southeastern Oregon from 2014 to 2015. We used locations from GPS‐collared foxes to estimate seasonal utilization distributions (UD) with the biased random bridge approach. We also estimated seasonal intensity distributions (ID) to identify areas with increased residence time per visit and recursion distributions (RD) to identify areas that are frequently visited. Mean 95% UD area for all foxes was 37.41 km2 during breeding and gestation, 21.44 km2 during pup-rearing, and 20.11 km2 during dispersal. Male UD area differed among seasons, where UDs during breeding and gestation (x̄ = 37.68 km2) were larger than during dispersal (x̄ = 18.70 km2) but not during pup-rearing (x̄ = 21.44 km2). Our seasonal 95% UD area estimates are among the highest reported for kit foxes, suggesting peripheral areas may not meet ecological requirements as well as core areas. Second-order selection ratios revealed foxes selected desert scrub and sparsely vegetated cover across all seasons at the population level. Within 30% IDs, mean third-order selection ratios showed selection of sparse vegetation with seasonal selection of desert scrub cover. Within 30% RDs mean selection ratios showed selection of sparse vegetation and nonnative grasslands throughout the year. At all levels there was individual variation in patterns and strength of selection. We contend a heterogeneous landscape with sparsely vegetated and desert scrub cover (i.e., intensive foraging areas and den sites) mixed with grasslands (i.e., rapid foraging areas) provides suitable habitat for kit foxes. Identifying patterns of resource use and selection of this species at their distributional periphery will improve conservation strategies for the kit fox in Oregon and other portions of their range.
Mammalian carnivores have adapted to successfully occupy a wide range of environments spanning tropical to polar ecosystems. Some species, however, have evolved in ways that constrain their ability to thrive in extreme environmental conditions. For example many members of the Family Mustelidae are vulnerable to extreme temperatures resulting from their tubular body shape. The American mink (Neovison vison) likely faces these temperature constraints, being a smaller-bodied mustelid that ranges over a large portion of North America. Mink are largely understudied in its native range with knowledge being particularly sparse with respect to winter ecology. During 2011–2012 we conducted winter telemetry on seven adult mink and used resource selection function models to assess habitat selection patterns while considering spatial extent and gender. We found that at a larger extent, the animals' use of habitat was strongly linked to riparian features, whereas this effect was less noticeable at a finer scale. The larger males selected more lakeshore habitat, whereas the smaller females generally were near smaller streams with both selecting for beaver modified habitat. While we recognize the limited sample size in our study, we speculate that this spatial separation could be linked to higher energetic costs for females to forage aquatically in winter because of their smaller body size. This may make females more sensitive to competition from other forest carnivores (e.g. American marten) as well as impacts from resource development activities.
An essential component of management efforts to control invasive species is the estimate of life history parameters, such as reproductive rate and litter size. Wild pigs (Sus scrofa), one of the most invasive terrestrial mammals worldwide, have recently become established on the Canadian prairies. We estimated life history traits in a population of wild pigs in Saskatchewan, Canada, at the current northern limit of their North American distribution. The average pregnant wild pig weighed 73.8 kg (46 – 130 kg; n = 7). Fifty-four percent of females ≥46 kg were pregnant in Feb., with an average of 5.6 fetuses per pregnant female (range 4 – 7; n = 7). Although small sample sizes precluded statistical significance, we found that larger females in better body condition tended to have more fetuses and that the sex ratio of fetuses tended to be female-biased. Based on the cohort that we sampled in Feb., we predicted parturition would occur between Feb. and May; this range of parturition dates may have been wider had we sampled wild pigs at other times of the year. We show that the number of fetuses of wild pigs in Saskatchewan is similar to other areas, suggesting that population growth and spread could be just as rapid. Our estimates represent the first empirical life history measures of wild pigs in Canada and are an essential step in developing science-based eradication plans for this highly invasive species.
The northern long-eared myotis (Myotis septentrionalis) occurs across much of eastern North America and is listed as federally threatened in the United States due to pervasive population declines. Limited data are available about roosting behaviors for this imperiled species. We report on night-roosting behaviors for the northern long-eared myotis under a bridge in northwestern Nebraska. Grooming, short visits, and feeding were the most frequently observed behaviors. Grooming, inactivity, and nursing had the longest durations, albeit all averaged <15 min per event. We also documented movement and urination infrequently. Prey manipulation associated with feeding was a frequent behavior and consisted of individuals facing upward or downward, culling wings, elytra, and legs of large prey items. When facing upward wing and tail membranes formed a cup against the abutment wall that likely limited loss of prey. Individuals used the bridge throughout the night but roosted most frequently at 4 and 8 h after sunset (00:15 and 04:15 h, respectively), with early morning activity dominated by feeding/prey manipulation. Our study showed night roosts were used frequently for many reasons, especially for grooming and consumption of large prey. Our observations represent the first description of night-roosting behaviors for the northern long-eared myotis.
American martens (Martes americana) warrant concern in Wisconsin, U.S.A., for multiple reasons, including being the state's only endangered mammal and a clan animal of the Ojibwe tribes. American martens were once present throughout much of the state but were extirpated in the early 20th century through habitat loss and unregulated trapping. In the 1950s two reintroductions of martens to Stockton Island of the Apostle Islands archipelago were considered failures, with the last confirmed sighting in the archipelago in 1969. In the decades since the Stockton Island reintroduction efforts, anecdotal reports of martens have surfaced throughout the archipelago. In 2014–2016 we deployed 91 camera traps on 13 of the 21 Apostle Islands to survey the archipelago's extant carnivore species. We detected American martens at 28 of 87 functioning camera trap sites on 5 of 13 monitored islands and documented the existence of American martens in APIS in Wisconsin for the first time in over 50 y. We suggest continued research to evaluate the status of the APIS population and its potential origins to guide future conservation efforts.
In May 2016 conjoined white-tailed deer (Odocoileus virginianus) fawns were found deceased in southeastern Minnesota. The bodies of the fawns were joined ventrally and laterally with two separate necks and heads. This is the first case described of conjoined two-headed white-tailed deer brought to full-term gestation and delivered.