Cisco (Coregonus artedi (sensu lato) Lesueur, 1818) forms matching in appearance to Blackfin Cisco from the Laurentian Great Lakes occur in four lakes in Algonquin Park, Ontario, Canada, a historical drainage of glacial Lake Algonquin (precursor of lakes Michigan and Huron). Their occurrence may represent colonization from glacial Lake Algonquin drainage patterns 13 000 calibrated years BP or independent evolution within each lake. Gill-raker numbers, temperature at capture depth during lake stratification, and hurdle models of habitat distribution are summarized. Blackfin (nigripinnis-like) in the four lakes had higher gill-raker numbers than artedi-like cisco captured in nearby lakes or within the same lake. Two lakes have a bimodal gill-raker distribution that indicate co-occurrence of two forms. Blackfin occupied the hypolimnion with a peak depth distribution at 20–25 m. Maximum depth for blackfin was 35–40 m. The presence of the opossum shrimp (Mysis diluviana Audzijonyte and Väinölä, 2005) appears necessary for the occurrence of cisco diversity in lakes but not sufficient in all cases. The presence of two forms of cisco in at least two lakes points to the possibility of the colonization hypothesis or the ecological speciation hypothesis as accounting for this phenomenon. Genetic analysis is needed to determine which of these hypotheses best accounts for the occurrence of blackfin in Algonquin Park.

The diversity of Laurentian Great Lakes ciscoes (Coregonus artedi, sensu lato) arose via repeated local adaptive divergence including deepwater ciscoes that are now extirpated or threatened. The nigripinnis form, or Blackfin Cisco, is extirpated from the Great Lakes and remains only in Lake Nipigon. Putative nigripinnis populations were recently discovered in sympatry with artedi in a historical drainage system of glacial Lake Algonquin, the precursor of lakes Michigan and Huron. Given the apparent convergence on Great Lakes form, we labeled this form blackfin. Here, we test the hypothesis that nigripinnis may have colonized this area from the Great Lakes as a distinct lineage. It would then represent a relict occurrence of the historical diversity of Great Lakes ciscoes. Alternatively, blackfin could have evolved in situ in several lakes. We captured more than 600 individuals in the benthic or pelagic habitat in 14 lakes in or near Algonquin Provincial Park (Ontario, Canada). Fish were compared based on habitat, morphology, and genetic variation at 6,676 SNPs. Contrary to our expectations, both cisco and blackfin belonged to an Atlantic lineage that colonized the area from the east, not from the Great Lakes. Sympatric cisco and blackfin were closely related while fish from different lakes were genetically differentiated, strongly suggesting the repeated in situ origin of each form. Across lakes, there was a continuum of ecological, morphological, and genetic differentiation that could be associated with alternative resources and lake characteristics. This study uncovers a new component of cisco diversity in inland lakes of Canada that evolved independently from ciscoes of the Laurentian Great lakes. The diversity of cisco revealed in this study and across their Canadian range presents a challenge for designating conservation units at the intraspecific level within the framework of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

While resource quality and predator-derived chemical cues can each have profound effects on zooplankton populations and their function in ecosystems, the strength and direction of their interactive effects remain unclear. We conducted laboratory experiments to evaluate how stoichiometric food quality (i.e., algal carbon [C] : phosphorus [P] ratios) affects responses of the zooplankter, Daphnia pulicaria, to predator-derived chemical cues. We compared growth rates, body P content, metabolic rates, life-history shifts, and survival of differentially P-nourished Daphnia in the presence and absence of chemical cues derived from fish predators. We found effects of predator cues and/or stoichiometric food quality on all measured traits of Daphnia. Exposure to fish cues led to reduced growth and increased metabolic rates but had little effect on the body %P content of Daphnia. Elevated algal C : P ratios reduced growth and body %P and increased mass-specific respiration rates. While most of the effects of predator cues and algal C : P ratios of Daphnia were non-interactive, reduced survival and relatedly reduced population growth rates that resulted from P-poor food were amplified in the presence of predator-derived cues. Our results demonstrate that stoichiometric food quality interacts with antipredator responses of Daphnia, but these effects are largely trait dependent and appear connected to animal life-history evolution. Given the ubiquity of predators and P-poor food in lake ecosystems, our results highlight the importance of the interactive responses of animals to predator cues and poor nutrition.

We conducted field experiments in the nearshore area of two urban lakes (Lake Washington and Lake Sammamish) in western Washington to test the attractive quality of artificial nighttime lighting to subyearling salmonids Oncorhynchus spp. In both lakes, experimental trials were conducted along a uniform 156‐m shoreline section twice a month (one night with lights and one control night without lights) from March to May to correspond with peak nearshore rearing of subyearling salmonids. We examined the effects of three light intensities on nearshore fish abundance: (1) no light, (2) dim light (maximum, 5.0 lx), and (3) bright light (maximum, 50.0 lx). These were compared with abundances from control nights without light treatments. Beach seining was used to determine fish abundance. For each month, the total number of subyearling salmonids (Chinook Salmon O. tshawytscha, Coho Salmon O. kisutch, and Sockeye Salmon O. nerka combined) was greater on the lighted nights (all treatments combined) than it was on the control nights. In both lakes, the most subyearling salmonids were collected in the bright‐light treatments, an intermediate amount in the dim‐light treatments, and few in the no‐light treatments. In some instances, subyearling salmonid abundances in the bright‐light treatments were more than 10 times greater than in the no‐light treatments. The effect of nighttime artificial lighting was generally more pronounced in March than in April or May. The results support our hypothesis that subyearling salmonids exhibit nocturnal phototaxic behavior when exposed to elevated nighttime lighting. A major concern of artificial nighttime lighting for subyearling salmonids is the potential for an increased predation risk, and we believe the prudent management goal would be to minimize artificial nighttime lighting. Received October 23, 2016; accepted March 7, 2017 Published online May 26, 2017

Multiple invasive species may interact, influencing one another and generating synergistic effects on food webs and ecosystem processes. We investigated the interaction between two non‐native species widespread in the western USA: common carp (Cyprinus carpio) and Russian olive (Elaeagnus angustifolia), an invasive riparian tree associated with di‐nitrogen fixation. Deep Creek, Idaho, was an International Biological Program site in the early 1970s; at that time, carp were rare and Russian olive was absent. Subsequently, Russian olive was introduced and established a dense stand, increasing allochthonous inputs and nitrogen‐rich benthic organic matter. Since 1971, carp density has increased ~4× (an increase our bioenergetic analysis suggests could not have been sustained in the absence of Russian olive). Carp gut contents in 2013–2014 revealed, on average, ~40% olives, and, similarly, stable isotope analyses revealed ~58% of carp tissues were derived from olives. A small‐scale, short‐term experimental exclusion of these subsidized carp caused ~3× increases in macrophytes and chlorophyll‐a, suggesting they may limit algae and macrophyte biomass. Moreover, carp that consumed olives excreted more nitrogen (~2× more ammonium, ~2× more total dissolved nitrogen, and ~3× more total nitrogen) compared to those that had not, which may amplify recycling and export from streams invaded by both species. This scenario is characteristic of an “invasional meltdown,” with attendant changes in food webs and ecosystem processes.

Understanding factors that influence resource pulses is an important aspect of ecosystem ecology. We quantified below‐ to aboveground energy and nutrient fluxes during the 2015 periodical cicada emergence from forest habitats in a tallgrass prairie matrix and compared results to our prior studies of the 1998 emergence in the same watershed. We estimated 35.2 million cicadas emerged across 159 ha in 2015, almost 2× more than the 19.6 million across 98 ha in 1998. The 2015 emergence resulted in below‐ to aboveground fluxes of 9.4 metric tons of ash‐free dry mass and 1.12 metric tons of N, both ~2× greater than 1998. This corresponds to 59 kg C/ha and 7 kg N/ha in and adjacent to forested areas in 2015. Increased emergence in 2015 was a result of spatial expansion of cicadas, not higher densities. Periodical cicadas are expanding with forest habitats in this region. Cicadas expand into and oviposit in ~40% of available forest habitat during each emergence. Accordingly, we predict the 2032 emergence will span ~245 ha. Our study demonstrates how human alterations to a landscape, in this case forest expansion linked to fire suppression and reduced grazing, can alter the magnitude and extent of a resource pulse.

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