Lake Erie Island Research Articles

Quantification of cormorant litter and nutrient deposition to Great Lakes island ecosystems

Ornithogenic nutrients derived from waterbirds such as the double-crested cormorant (Phalacrocorax auritus, Lesson) have been linked to habitat change within nesting colonies. For the islands of Lake Erie, where increasing cormorant populations and subsequent habitat change have spurred management activity, estimates of the quantity and chemical characteristics of avian-derived contributions are lacking. To evaluate the quantity and chemical characteristics of ornithogenic litterfall beneath a double-crested cormorant colony on a western Lake Erie island we investigated the mass of material and nutrient composition (PO43−, NO3− and NH4+) reaching the forest floor under three nest densities (Low: 1–96 nestsha−1; Medium: 97–255 nestsha−1 and High: >255 nestsha−1). As expected, litterfall (total mass) input differed among nest densities with the most substantial input (225.05g/m2week−1) measured under High nest density conditions. Nutrient concentrations also showed increases with nest density to a point, where mean PO43− and NH4+ concentrations showed no differences between Medium and High nest density sites. As well, NO3− concentrations were highest under Medium density, with no differences in this nutrient observed between Low and High density. Collectively, litterfall nutrient composition was similar to those linked to habitat changes in other waterbird colonies. Similarities in the concentrations of several nutrients between Medium and High nest density categories suggest that management actions aimed at reducing allochthonous nutrient contributions should try to sustain nest density at or below 96 nestsha−1.

Double-Crested Cormorant (Phalacrocorax auritus) Nesting Effects on Understory Composition and Diversity on Island Ecosystems in Lake Erie

The context for this study is the management concerns over the severity and extent of the impact of cormorants on island flora in the recent past on Lake Erie islands. Accordingly, this study sought to quantify the nesting colonies' influence on coarse woody litter and how nest densities and litter depth may influence the herbaceous layer, the seed bank composition and viability across the extent of three Lake Erie islands. The data for this study were collected from 2004 to 2008 on East Sister Island and Middle Island using two main strategies. First, herbaceous layer surveys, cormorant nest counts, soil seed bank cores, and litter depth measurements were executed using a plotless-point quarter method to test island-wide impacts from nesting activities (data were also collected on a third island, West Sister Island as a reference for the other two islands). Secondly, a sub-sample of the entire plot set was examined in particularly high nesting density areas for two islands (Middle Island and East Sister Island). Kruskal-Wallis tests indicated that there are subtle changes in the herbaceous diversity (total, native and exotic) and seed bank composition across the islands. The sub sample set of the plots demonstrated that Phalacrocorax auritus nest density does influence litter depth, herbaceous species abundance and diversity. Cormorant nesting pressures are restricted to areas of high nesting pressures and competition. However, there remains a risk to the interior herbaceous layer of the island if the effects of nesting pressures at the edges advance inward from this perimeter.

Unisexual salamanders (genus Ambystoma) present a new reproductive mode for eukaryotes

To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal bisexual reproduction. Parthenogenesis, gynogenesis, and hybridogenesis are the modes that have generally been ascribed to various unisexuals. Unisexual Ambystoma are abundant around the Great Lakes region of North America, and have variously been described as having all 3 reproductive modes. Diploid and polyploid unisexuals have nuclear genomes that combine the haploid genomes of 2 to 4 distinct sexual species, but the mtDNA is unlike any of those 4 species and is similar to another species, Ambystoma barbouri. To obtain better resolution of the reproductive mode used by unisexual Ambystoma and to explore the relationship of A. barbouri to the unisexuals, we sequenced the mitochondrial control and highly variable intergenic spacer region of 48 ambystomatids, which included 28 unisexuals, representatives of the 4 sexual species and A. barbouri. The unisexuals have similar sequences over most of their range, and form a close sister group to A. barbouri, with an estimated time of divergence of 2.4-3.9 million years ago. Individuals from the Lake Erie Islands (Kelleys, Pelee, North Bass) have a haplotype that demonstrates an isolation event. We examined highly variable microsatellite loci, and found that the genetic makeup of the unisexuals is highly variable and that unisexual individuals share microsatellite alleles with sexual individuals within populations. Although many progeny from the same female had the same genotype for 5 microsatellite DNA loci, there was no indication that any particular genome is consistently inherited in a clonal fashion in a population. The reproductive mode used by unisexual Ambystoma appears to be unique; we suggest kleptogenesis as a new unisexual reproductive mode that is used by these salamanders.

The origin of the western Lake Erie grooves, Ohio: implications for reconstructing the subglacial hydrology of the Great Lakes sector of the Laurentide Ice Sheet

Streamlined grooves and s-forms cover the western Lake Erie Islands, Ohio, as well as the channels between the islands, and the adjacent mainland. Although previous interpretations advocate direct glacial ice erosion, we offer the alternative interpretation that forms were eroded by meltwater, specifically by plucking, sediment abrasion, and cavitation in high velocity, sediment-laden flows. We base our arguments on detailed descriptions and interpretations of the Glacial Grooves State Memorial site (GGSM) on Kelleys Island. The site consists of a linear furrow that is adorned by s-forms in its base and on its walls. These include linear forms, cavettos, sichelwannen, comma forms, multi-troughed forms, and plunging forms. All s-form sites provide a snapshot of the last phase of erosion after evolution of the local landscape through multiple generations of s-form formation. As s-forms are found on topographic highs and lows, we believe they represent a regional flow that overtopped the majority of the islands. Flow was initially as a sheet that quickly collapsed into channelized flow that was diverged around the islands. We also believe that this flow had a major impact on the Laurentide Ice Sheet in this region, resulting in rapid glacial advance and extremely low ice-sheet profiles.

COLOR‐PATTERN VARIATION IN LAKE ERIE WATER SNAKES: THE ROLE OF GENE FLOW

In an effort to clarify the evolutionary processes influencing color-pattern variation in Lake Erie island water snake (Nerodia sipedon) populations, rates of gene flow among island and mainland populations were estimated from patterns of allozymic variation detected using electrophoresis. Rates of gene flow were high with Nm, the number of migrants per generation, averaging 25.5 among island sites, 9.2 between the Ontario mainland and the islands, and 3.6 between the Ohio mainland and the islands. Based on estimates of current population size from mark-recapture work and of past population size extrapolated from the extent of shoreline habitat, values of m between island and mainland populations ranged from 0.0008-0.01. Synthesis of estimates of the rate of gene flow with information on inheritance of color pattern, the strength of natural selection, and population history supports the hypothesis that color-pattern variation in island populations results from a balance between gene flow and natural selection. However, depending on the mode of inheritance of color pattern, stochastic processes such as drift may have been important in the initial stages of differentiation between island and mainland populations.

COLOR-PATTERN VARIATION IN LAKE ERIE WATER SNAKES: PREDICTION AND MEASUREMENT OF NATURAL SELECTION

A classic example of natural selection, that of color-pattern variation in Lake Erie island populations of water snakes, was reexamined to overcome shortcomings resulting from classification of snakes into discrete color-pattern categories and use of cross-sectional data. Four continuously varying color-pattern components (DB, the number of dorsal blotches; LB, the number of lateral blotches; ROWS, the height of lateral blotches measured in scale rows; and VEXT, the extent of ventral pigmentation) were analyzed. Patterns of natural selection were predicted from the relationship between color-pattern scores and independent measures of relative crypsis. Tests for natural selection were carried out using longitudinal data on neonate to juvenile-aged snakes and cross-sectional data on juvenile to adult-aged snakes. As predicted, the form of selection differed between younger and older age classes of snakes: selection resulted in a reduction in DB and LB among neonate and juvenile snakes but had little influence on color-pattern components in older snakes. The correspondence between observed patterns of natural selection and predictions based on the relationship between color-pattern scores and relative crypsis supports the hypothesis that differential predation by visual predators on younger age classes of snakes is the mechanism of selection. Gene flow from mainland populations or the initial lack of an allele necessary for reduced pattern may explain why selection has not resulted in greater differentiation between island and mainland populations.

Color pattern variation in Lake Erie water snakes: inheritance

The hypothesis that color pattern variation in Lake Erie island water snake (Nerodia sipedon) populations results from the opposing effects of natural selection and gene flow requires that this variation have a genetic basis. To determine whether color pattern variation is genetically based, data on the color pattern of wild-caught females and their captive-born offspring were used to estimate heritability of and correlations among four color pattern components. These data, and the results of two laboratory crosses, were also used to test for major locus influences on color pattern. Heritabilities of color pattern components estimated from sib analysis were significantly greater than zero for all four color pattern components, ranging from 0.34 to 0.79. Phenotypic and genetic correlations among color pattern components were positive, ranging from 0.24 to 0.55 (phenotypic correlations) and from 0.40 to 0.82 (genetic correlations). However, inheritance of color pattern was not strictly quantitative. Rather, a major locus appeared to influence color pattern, with alleles at this locus possibly determining whether snakes had regular (mainland-like) or reduced color patterns. Allele frequencies at this locus may have influenced the rate at which island and mainland water snake populations initially differentiated from each other, and may explain the lack of reduced-pattern morphs under similar selective regimes elsewhere.

Alternate pathways of succession on the Lake Erie Islands

In order to determine the effect of prior land use on secondary succession, woody plant species abundances were determined on the Lake Erie Islands in 21 sites 20–90 yr post-abandonment: 11 former vineyards, 8 former orchards, and 2 former quarries. Detrended Correspondence Analysis ordination was used to compare the relative abundances of woody plants in the 21 successional sites to each other and to 5 mature upland forests and 3 mature lowland forests. Vineyards 20–45 yr post-abandonment had closed canopies 2–4 m tall and were dominated by the same mix of species dominating mature forests at similar elevations. Abandoned orchards 20–45 yr post-abandonment supported species common in mature forest floras as well as many shade-intolerant, pioneer tree and shrub species not found in mature stands. These differences in successional patterns seem to be related to differences in the suite of colonization sites presented upon abandonment, with orchards being dominated by open, bare ground, and vineyards by shaded ground receiving ca. 20% of full sunlight. Newly abandoned vineyards had appreciable ‘advanced regeneration’ of saplings of shade-tolerant species 3–7 yr old growing among the grapes. While former quarries remained open, marginal habitats with sparse, open canopies dominated by species typical of rocky cliff edges, the community structure of former vineyards and orchards converged toward each other and toward the composition of mature forests at similar elevations. Thus patterns of secondary succession varied with prior land use and were determined by the suite of colonization sites available at the time of abandonment.

Forest Composition on the Lake Erie Islands

The Lake Erie Island archipelago includes 22 islands which are distinct from the neighboring Canadian and American shores in climate, topography, surface geology and soils. The forest communities of these islands were analyzed for species composition, relationships to environmental factors and similarity to mainland forests. When analyzed by reciprocal averaging ordination, forest stands split into two tight clusters. Upland forests, dominated by Acer saccharum and Celtis occidentalis, occurred where bedrock level> lake level. Lowland forests occurred on sites where bedrock level 65 km2. Dolomites and limestones of Silurian and Devonian age form the bedrock of the region (Core, 1948; Hamilton and Forsyth, 1972). The soils of the upland, exposed areas of the islands are shallow, generally less than 40 cm in depth, have many bedrock outcrops, and are low in available water (Redmond et al., 1971; Musgrave and Derringer, 1981). Most of these upland soils are currently classified as Castalia, very stony, silt loams (Musgrave and Derringer, 1981). Lowland areas and areas not exposed to direct lake action a-re covered by deeper soils (up to 175 cm) formed on limy glacial till (Redmond et al., 1971; Musgrave and Derringer, 1981). The climate of the Lake Erie Islands is temperate, humid-continental (Cooper and Herdendorf, 1977). It differs in several respects, however, from the neighboring Ohio, Michigan and Ontario shores. Due to the buffering effect of the lake, the average frostfree period is 205 days, 27% longer than Tiffin, Ohio, 50 km to the S (Verber, 1955). Significantly less precipitation falls on the islands than on the mainland. Annual

Regional hydrogeochemical patterns in ground water of Northwestern Ohio and their relation to Mississippi valley—type mineral occurrences

A cluster of minor Mississippi Valley-type deposits occurs in northwestern Ohio. The district, which forms a northeasterly trending belt that cuts across the Findlay Arch, extends from the Indiana border to the Lake Erie Islands. The minerals of the deposits — chiefly celestite, fluorite and sphalerite with lesser amounts of barite and galena — show variation in both geographic and stratigraphic distribution. Dolomites of Middle Silurian to Middle Devonian age, which are the host rocks, also form an important aquifer system. The deposits are of interest because they might be indicators of economic mineralization at depth. Through a reconnaissance study, one-hundred ground-water samples from shallow wells (less than 50 m deep) were collected across an area of approximately 19 000 km 2. Recharge takes place in the southern part of the area while ground-water flow is northward towards Lake Erie. The majority of the samples are high in sulfate with the source being evaporites within the carbonate sequence. The remainder of the water samples are rich in bicarbonate. Trend surface maps for the major constituents indicate that the ground-water chemistry for the region is established chiefly by the lithology and the flow system. Trend surface maps for F −, Sr and Ba reflect the geographic distribution of the minerals in the deposits. Correlations are weakened, however, due to the influence of geochemical barriers such as SO 4 2− on Ba and Sr, and Ca on F −. The map for Pb follows the trends of the major constituents instead of the mineralization. In a detailed study across northwestern Sandusky County, which lies near the center of the district, 46 samples were collected in an area of 78 km 2. Trend surface maps for Ca, Mg, SO 4 2− and total dissolved solids reflect the chemistry of the bedrock and display concentrations that increase along the local flow path. Maps for F −, Sr and Ba correlate with mineralization in the vicinity, the first of these displaying a local trend and the last two correlating with regional trends.

On the Origin of the Field Plants of the Northeastern United States

Old fields have dominated studies of terrestrial plant succession in the eastern United States. In spite of the tremendous amount of work on old field succession, fundamental questions remain. One such question is the subject of the present paper: In the primeval landscape, where were the plants that are abundant today in old fields? The question holds interest not only for interpretation of the northeastern landscape but also for understanding of the habitats in which field plants evolved. The plants of fallow agricultural fields are widely assumed to be early successional species, i.e., plants adapted to move from one temporary opening to another, but did they really evolve as successional plants? Many of the plants that grow in abandoned fields today are not native to North America and were thus not part of the landscape prior to European settlement. Bard (1952) reported that between one fifth and one third of the plant species in old fields in New Jersey were alien to North America. It is of the remaining two thirds (roughly 100 species) that we can ask, Where was a sun-loving field flora growing in a landscape that was heavily forested? According to Braun (1950, p. 7), "When the first settlers colonized the Atlantic seaboard ... they found an endless expanse of forest broken only by swamps and bogs, by cliffs or river bluffs too steep for forest, by windfalls and burns, by small grassy openings such as the serpentine barrens of the northern Piedmont, and by the prairie patches and 'barrens' of the interior.' Four hypotheses can be suggested to account for the location of native field plants in the presettlement landscape. (1) They evolved on agricultural land abandoned by Indians far back in time. (2) Native field plants migrated eastward from prairies and savannas at the western margin of the deciduous forest with the onset of extensive clearing for settlement and agriculture and with the development of continuous east-west corridors of open field habitat along railroads and canals. (3) Native field plants were true pioneer or early successional species that colonized temporary forest openings caused by wind, fire, and other kinds of

Color Pattern Variation in Crotalus lepidus lepidus (Viperidae) in Southwestern Texas

Geographic isolation and adaptation have combined to produce two different popula- tions of Crotalus 1. lepidus in southwestern Texas. Statistically significant differences in background color-matching are the result of adaptation to dominant substrate colors that differ sharply between ranges of the two populations. Uniformly dark primary blotches in combination with pink and buff ground colors characterize the Davis Mountains-Big Bend population which is confined mainly to the darkly weathered volcanic rocks of the Davis Mountains and Big Bend region. The Stockton-Edwards Plateau population occurs on the more lightly weathered limestones of the Stockton and western Edwards plateaus, and displays ground colors of various shades of gray combined with a pronounced anterior fading of the primary blotches. Snakes of the Davis Mountains-Big Bend population have a significantly higher mean number of primary blotches than those of the Stockton-Edwards Plateau population. Stretches of desert flatland serve as effective barriers, limiting gene flow and enabling populations to respond separately to selection pressure applied by need for concealment from predators and/or prey. Background color-matching is a frequently observed adaptation of animals to their environment. However, among the many species of snakes that display this trait, documentation of adaptation involving color or color pattern is rare. Dunn (1942) noted the paucity of work on natural selection in snake populations and remarked on the value of these reptiles for such studies. Camin and Ehrlich (1958) and Ehrlich and Camin (1960) effectively demonstrated color pattern selection in Lake Erie island populations of Natrix sipedon. They observed statistically significant differences between pattern types of young and adult members of a population. From young adult to adult, those with banded patterns were being eliminated in favor of the unbanded. They interpreted this to be a response to selection pressure applied by avian predators such as gulls, herons, and raptors because, to the human eye, banded snakes were highly conspicuous, whereas the unbanded were well camouflaged. Similar results were obtained by Beatson (1976) from a population of N. s. sipedon in Kansas. These conclusions are in agreement with the widely held view that most background-color matching in animals has developed as a result of natural selection by predators that rely on vision for prey detection (Portmann, 1959). Among rattlesnakes, few species or subspecies exhibit background color- matching better than the Mottled Rock Rattlesnake, Crotalus lepidus lepidus (Kennicott), of southwestern Texas, south-central New Mexico, and the Sierra Madre Oriental in Mexico. The basic color pattern consists of a series of well defined primary dorsal blotches, which become transverse bands posteriorly. Primary blotches alternate with a series of one to three less distinct secondary blotches. The primaries and secondaries vary in contrast but produce the effect of a mottled, banded snake (Fig. 1). This pattern in combination with various ground colors blends in exceptionally well with the substrate upon which the snake is found. The degree of stippling on individual scales also contributes significantly to the overall camouflage effect. THE SOUTHWESTERN NATURALIST 27(3):263-272

Natural Selection in Water Snakes (Natrix sipedon L.) on Islands in Lake Erie

Although in recent years laboratory selection has become a commonplace, natural selection operating in wild populations has been quite difficult to document. Much of the published work has been inconclusive (see summary in Robson and Richards, 1936, for early work) or open to controversy (e.g., Lamotte, Cain and Sheppard, and Sedlmair on Cepaeca). The present study analyzes all available data on color pattern variation in the water snakes of the Lake Erie islands. These data appear to illustrate a situation in which migration and strong selection pressure combine to give a relatively clear-cut picture of differential elimination of color pattern types from a population. The uniform medium-gray color of the majority of adult water snakes inhabiting the islands in the western part of Lake Erie (as opposed to the normal dark banded type) was first noted by Morse (1904). In 1937 Conant and Clay described the island population as a separate subspecies Natrix sipedon insularum, differing from typical sipedon primarily in the large percentage of unbanded or weakly banded individuals. In 1954 Camin, Triplehorn and Walter compared the frequencies of various pattern types in wild-caught juveniles with those of the adult population and found a statistically significant decrease in the proportion of banded individuals from the juvenile to the adult population. In the present paper these previous data are reanalyzed and integrated with additional data, principally on frequencies of pattern types in

Photosynthesis and Growth Rates of Two Diatom Communities in Western Lake Erie

During 1949 a year-round study weas made of the photosynthetic activity exhibited by phytoplankton communities inhabiting the waters of the western Lake Erie island region. One conclusion from that study (Verduin 1951b) was that the different species which have become adapted to a particular aquatic habitat show remarkable similarity in photosynthetic rates. In the spring months of 1950 an Asterionella-Cyclotella community was observed in the. waters around Pelee Island and at the same time a Stephanodiscus community was found about 20 mi. east of Pelee Island. The presence of these distinctly different communities afforded. an excellent opportunity to study them simultaneously, using samples collected from each community on the same dates. Their photosynthetic rates, growth rates, and related characteristics are described and discussed below.

A New Flora of the Lake Erie Islands, by Earl L. Core [Review

A New Flora of the Lake Erie Islands, by Earl L. Core [Review

A Population of Lake Erie Island Water Snakes

A Population of Lake Erie Island Water Snakes

Nesting of the Herring Gull and Some Other Birds on Lake Erie Islands

Nesting of the Herring Gull and Some Other Birds on Lake Erie Islands