We update the distribution of two slug species Arion fuscus M & uuml;ller, 1774 and A. subfuscus Draparnaud, 1805 in the Upper Great Lakes Region of the United States using molecular identification methods. These slugs are invasive in North America, and they are cryptic in terms of their morphological identification. Arion fuscus has not previously been reported in the literature in the Upper Great Lakes area, and A. subfuscus has previously been reported as abundant in this region. However, all previous distribution studies were determined using visual identification tools, which can result in misidentification between cryptic species. To reassess the distributions of these species, we used a mitochondrial ribosomal subunit 16S PCR amplification coupled with either DNA sequencing or a restriction enzyme digest assay to distinguish slug specimens that were morphologically consistent with both A. fuscus and A. subfuscus. We additionally identified any other slug species that were found along with the A. fuscus complex specimens, either through morphological characteristics or DNA sequencing. We collected slugs in 11 locations around Lake Superior, Lake Michigan, and Lake Huron using beer-baited pitfall traps from May to September 2022 and at one location from October to December 2023. We collected slugs in Marquette, Michigan, biweekly, a total of eight times, throughout the summer of 2022 to monitor change in slug activity over time. We found A. fuscus at nine of the 11 sampling locations and A. subfuscus at one location. Arion fuscus was found early in the spring before other slug species were active, and into late fall and early winter on days above freezing. The paucity of records of A. subfuscus and ubiquity of A. fuscus suggests that previous reports of A. subfuscus based on visual identification were potentially incorrect and suggests that molecular confirmation or dissections of reproductive anatomy are critical for accurate understanding of species distributions.

The benthic communities in the surf zone of the Laurentian Great Lakes were historically diverse assemblages with typically lotic taxa. Conditions were suitable for these lotic taxa due to wave activity and strong, nearshore currents. Due to anthropogenic stressors, including the introduction of Dreissena mussels, surf zone communities have been all but decimated in the lower Great Lakes. Remaining communities persist along the shorelines of Lake Superior, where they are influenced by lake conditions and tributary inputs. Despite their ecological importance, the relationship between these Great Lakes surf zone communities, nearby tributary communities, and the confluence (i.e., tributary mouth) communities has remained largely unexplored. This study compared the composition and succession of Lake Superior communities at three sites: tributary, confluence, and surf zone. Hester-Dendy multiplate samplers (n = 7 per site) were deployed for similar to 28-day periods over the course of the ice-free season (May through October) to assess community composition. Although diversity was similar between sites, community composition was distinct between the sites across all sample periods. Overall, compositional shifts were greater along the shoreline community, followed by confluence and tributary communities. The magnitude of compositional shifts, as well as diversity and composition, varied across the sample periods. These results suggest these communities are distinct, exhibiting compositional shifts that appear to correspond with production peaks at each site. As warmer temperatures and intensified storms affect Lake Superior in the coming decades, it is important that further research explore the ecology of tributary, confluence, and surf zone communities to better preserve these fascinating communities.

We studied the life history, diet, and trophic ecology of Hydropsyche alternans in four rocky sites located along the south-central coast of Lake Superior. The H. alternans life history and broad trophic niche space were similar to those of its riverine relatives. Quantitative sampling over the course of one ice-free season revealed that most individuals lived univoltine life histories that featured early to mid-summer mating, and oviposition and rapid growth and development through summer into fall. Most individuals overwintered as ultimate or penultimate larval instars. Pupation followed ice-out in the spring. Gut content sampling and δ13C and δ15N stable isotope analyses indicated that the typical larval diet is a mix of benthic, pelagic, and terrestrial food resources, including diatoms, small arthropods, sloughed periphyton, and in one site, fugal hyphae apparently of foredune origin. As a suspension-feeding omnivore that relies on waves and currents to deliver food to its nets, H. alternans larvae form energetic links between coastal, nearshore, and offshore food webs. These connections have been lost throughout the lower Laurentian Great Lakes as a consequence of the invasion and spread of Dreissena mussels.

Neotropical savannas exhibit unique patterns of diversity of plant and animal life that are poorly understood. Effective conservation of these often imperiled ecosystems requires a basic understanding of species occurrence as well as the site-specific factors that influence plant community composition. This study focuses on the savanna flora of the island of Utila, Bay Islands, Honduras. Compositional trends were assessed across multiple environmental gradients including surface hydrology, microtopography, nutrient levels and pH using Braun-Blanquet cover abundance in a stratified systematic sampling design. Non-metric multidimensional scaling and non-parametric multiplicative regression were applied to identify community types and to model species’ responses to environmental gradients. We separated habitats into three basic types: sedge meadow, Blechnum - Cladium parkland and woody hammock. Compositional gradients along ordination axes were highly correlated with depth of the water table, pH and conductivity. Disturbance history, especially time since fire, was also linked to an indirect gradient. Some species – notably Acoelorrhaphe wrightii and Chrysobalanus icaco – are generalists, and their distributions may reflect past disturbance. Microtopography was critical in determining distribution for a suite of species that occurred only on mound formations in areas subject to prolonged inundation during the rainy season. Disturbance, particularly by hurricanes and fire, may promote within-habitat diversity; for example, the exposed lignotubers and rhizomes of trees killed by saline inundation provide habitat for less flood-tolerant species in wet areas, while burned clones of A. wrightii and surrounding peat areas permit colonization by many herbaceous species. Pair-wise floristic comparisons between Utila and eight other neotropical savannas revealed fewer than half of the 40 savanna species found on Utila were present in any other site. Two species of Cyperaceae, Fuirena scirpoidea and Rhynchospora tracyi , are new records for Honduras.

The vital roles that sponges play in marine habitats are well-known. However, sponges inhabiting freshwaters have been largely ignored despite having widespread distributions and often high local abundances. We used natural abundance stable isotope signatures of carbon and nitrogen (δ 13C and δ 15N) to infer the primary food source of the cosmopolitan freshwater sponge Spongilla lacustris. Our results suggest that S. lacustris feed largely on pelagic resources and may therefore link pelagic and benthic food webs. A facultative association between S. lacustris and endosymbiotic green algae caused S. lacustris to have significantly depleted carbon and nitrogen signatures that may reflect carbon and nitrogen exchange between sponges and their symbiotic algae. Isotopic data from specialist sponge consumers demonstrated that sponges hosting zoochlorellae were the major component of the diet of the spongillafly Climacia areolaris and the sponge-eating caddisfly Ceraclea resurgens suggesting that the symbiosis between freshwater sponges and algae is important to sponge predator trophic ecology. Our results help define the role of sponges in freshwater ecosystems and shed new light on the evolution and ecological consequences of a complex tri-trophic symbiosis involving freshwater sponges, zoochlorellae, and spongivorous insects.

The parasitic relationship between a black fly, Simulium annulus, and the common loon (Gavia immer) has been considered one of the most exclusive relationships between any host species and a black fly species. To test the host specificity of this blood-feeding insect, we made a series of bird decoy presentations to black flies on loon-inhabited lakes in northern Wisconsin, U.S.A. To examine the importance of chemical and visual cues for black fly detection of and attraction to hosts, we made decoy presentations with and without chemical cues. Flies attracted to the decoys were collected, identified to species, and quantified. Results showed that S. annulus had a strong preference for common loon visual and chemical cues, although visual cues from Canada geese (Branta canadensis) and mallards (Anas platyrynchos) did attract some flies in significantly smaller numbers.

Age-specific mortality rates of men are higher than those of women, and men have shorter average life spans than women. This has been interpreted as evidence of sexual dimorphism in rates of senescence. However, because mortality can be caused by numerous factors in addition to senescence, higher mortality rates do not necessarily indicate more rapid senescence. In this paper, we (1) emphasize the necessity of decoupling mortality and senescence when considering sexual dimorphism in senescence, (2) present a theoretical framework for the hypothesis that selection affects senescence in human males and females differently due to different life history characteristics, (3) consider phenotypic evidence from the literature that human males show a later onset of senescence than human females, despite exhibiting higher mortality rates, and (4) discuss the potential roles of mutation accumulation and antagonistic pleiotropy in the evolution of sexual dimorphism in senescence.

Measurements of groundwater–surface water exchange at three wetland stream sites were related to patterns in benthic productivity as part of the US Geological Survey's Northern Temperate Lakes–Water, Energy and Biogeochemical Budgets (NTL–WEBB) project. The three sites included one high groundwater discharge (HGD) site, one weak groundwater discharge (WGD) site, and one groundwater recharge (GR) site. Large upward vertical gradients at the HGD site were associated with smallest variation in head below the stream and fewest gradient reversals between the stream and the groundwater beneath the stream, and the stream and the adjacent streambank. The WGD site had the highest number of gradient reversals reflecting the average condition being closest to zero vertical gradient. The duration of groundwater discharge events was related to the amount of discharge, where the HGD site had the longest strong-gradient durations for both horizontal and vertical groundwater flow. Strong groundwater discharge also controlled transient temperature and chemical hyporheic conditions by limiting the infiltration of surface water. Groundwater–surface water interactions were related to highly significant patterns in benthic invertebrate abundance, taxonomic richness, and periphyton respiration. The HGD site abundance was 35% greater than in the WGD site and 53% greater than the GR site; richness and periphyton respiration were also significantly greater (p≤0.001, 31 and 44%, respectively) in the HGD site than in the GR site. The WGD site had greater abundance (27%), richness (19%) and periphyton respiration (39%) than the GR site. This work suggests groundwater–surface water interactions can strongly influence benthic productivity, thus emphasizing the importance of quantitative hydrology for management of wetland-stream ecosystems in the northern temperate regions.

Stable carbon and nitrogen isotope ratio analyses were used to characterize the primary energy sources and trophic positions of 16 common Lake Superior wave zone invertebrate species. Isotope data from six tributary species that were taxonomically and ecologically matched with common wave zone species revealed broad energetic separation between these similarly structured benthic food webs. Previously published stable isotope data for Lake Superior wetland and pelagic food webs were used to assess the relative importance of inter-habitat energy flow within the Lake Superior ecosystem. The results of these comparisons indicate that the Lake Superior wave zone is energetically distinct from its tributaries, wetlands, and to a lesser extent from its vast pelagic realm. This information and approach should prove useful in future studies on the bioenergetics of inter-zonal migrants and other species that forage in multiple habitats within the lake and also in revealing energetic connections among terrestrial, riverine, littoral, and pelagic food webs in the coastal ecosystems of Lake Superior.