Peer Reviewed Publications Copyright (c) 2013 Grand Valley State University All rights reserved. http://scholarworks.gvsu.edu/biopeerpubs Recent documents in Peer Reviewed Publications en-us Fri, 25 Jan 2013 22:18:09 PST 3600 Environmental Variation, Fish Community Composition, and Brown Trout Survival in the Pigeon River, Ottawa County, Michigan http://scholarworks.gvsu.edu/biopeerpubs/34 http://scholarworks.gvsu.edu/biopeerpubs/34 Wed, 08 Feb 2012 05:45:45 PST The Pigeon River, a small coolwater stream in western Michigan, has a history of hydrologic, stream habitat, and water quality degradation that led to the loss of its trout population by the late 1980s. After regulatory and watershed management efforts to reduce point- and nonpoint source pollution in the 1990s, the Michigan Department of Natural Resources reinstituted brown trout (Salmo trutta) stocking in 2003. As part of these efforts, we monitored water quality in the Pigeon River each fall between 1996 and 2008, and conducted stream surveys in 2006 and 2007 to evaluate the fish community and outcome of trout stocking. Water quality tended to improve and stabilize through time, although point- and nonpoint source pollution still contributed to water quality problems. Hydrologic instability, caused by wetland drainage, agricultural land use, and irrigation withdrawals from the lower mainstream, created periods of environmental stress. As a result, the fish community of the Pigeon River was dominated by common tolerant warmwater species, typical of agricultural watersheds in southern Michigan. Nonetheless, brown trout surviving from initial stockings in 2003 and 2004 had attained lengths of between 18 and 24 inches by 2007, suggesting the thermal regime, water quality, stream habitat, and forage base of macroinvertebrates and small fish were suitable to maintain a stocked brown trout population. Continued efforts to improve water quality, protect instream habitat, reduce high stormflows, and maintain adequate summer baseflows are needed to fully restore environmental conditions for the native fish community and stocked brown trout in the Pigeon River.

]]> Neil W. MacDonald et al. Differential Gene Expression and Protein Abundance Evince Ontogenetic Bias toward Castes in a Primitively Eusocial Wasp http://scholarworks.gvsu.edu/biopeerpubs/33 http://scholarworks.gvsu.edu/biopeerpubs/33 Tue, 30 Nov 2010 07:17:50 PST Polistes paper wasps are models for understanding conditions that may have characterized the origin of worker and queen castes and, therefore, the origin of paper wasp sociality. Polistes is ‘‘primitively eusocial’’ by virtue of having contextdependent caste determination and no morphological differences between castes. Even so, Polistes colonies have a temporal pattern in which most female larvae reared by the foundress become workers, and most reared by workers become future-reproductive gynes. This pattern is hypothesized to reflect development onto two pathways, which may utilize mechanisms that regulate diapause in other insects. Using expressed sequence tags (ESTs) for Polistes metricus we selected candidate genes differentially expressed in other insects in three categories: 1) diapause vs. non-diapause phenotypes and/or worker vs. queen differentiation, 2) behavioral subcastes of worker honey bees, and 3) no a priori expectation of a role in worker/gyne development. We also used a non-targeted proteomics screen to test for peptide/ protein abundance differences that could reflect larval developmental divergence. We found that foundress-reared larvae (putative worker-destined) and worker-reared larvae (putative gyne-destined) differed in quantitative expression of sixteen genes, twelve of which were associated with caste and/or diapause in other insects, and they also differed in abundance of nine peptides/proteins. Some differentially-expressed genes are involved in diapause regulation in other insects, and other differentially-expressed genes and proteins are involved in the insulin signaling pathway, nutrient metabolism, and caste determination in highly social bees. Differential expression of a gene and a peptide encoding hexameric storage proteins is especially noteworthy. Although not conclusive, our results support hypotheses of 1) larval developmental pathway divergence that can lead to caste bias in adults and 2) nutritional differences as the foundation of the pathway divergence. Finally, the differential expression in Polistes larvae of genes and proteins also differentially expressed during queen vs. worker caste development in honey bees may indicate that regulatory mechanisms of caste outcomes share similarities between primitively eusocial and advanced eusocial Hymenoptera.

]]> James H. Hunt et al. Height, Weight, and Fertility Among Participants of the Third Harvard Groth Study http://scholarworks.gvsu.edu/biopeerpubs/32 http://scholarworks.gvsu.edu/biopeerpubs/32 Fri, 27 Aug 2010 12:13:33 PDT The relationship between weight, height, weigh/height2 and fertility is examined in 610 females and 621 males from a 1968 follow-up study of the Third Harvard Growth Study participants. These subjects were born between 1912 and 1918 in the USA. Their physical and mental growth were studies for up to 12 years while they attended public schools in Boston Massachusetts, area. Height is not significantly related to fertility in either females or males, but weight and weight/height2 is positively related to fertility in females (r = +.117 and + .100 respectively) and weight/height2 is positively related to fertility in males (r = + .09). Weight and weight/height2 at skeletal age 12 of 305 females are both negatively correlated with later fertility (r = - .102 and -.141 respectively). Thus girls who later had large families were not heavier than average, but in fact, were taller and slimmer. In these data it appears the differential reproduction for heaviness is not likely to have had genetic effects but is probably a secular trend. The fact that taller and slimmer girls later went on to have larger families may be significant for the consideration of sexual selection.

]]> Eugenie Scott et al. Long Term Mobidity and Mortality of Adolescent Obesity: A Follow-up of Third Harvard Growth Study Participants of 1922 to 1935 http://scholarworks.gvsu.edu/biopeerpubs/31 http://scholarworks.gvsu.edu/biopeerpubs/31 Fri, 27 Aug 2010 12:13:32 PDT Background. Overweight in adults is associated with increased morbidity and mortality. In contrast, the long-term effect of overweight in adolescence on morbidity and mortality is not known.

Methods. We studied the relation between overweight and morbidity and mortality in 508 lean or overweight adolescents 13 to 18 years old who participated in the Harvard Growth Study of 1922 to 1935. Overweight adolescents were defined as those with a body-mass index that on two occasions was greater than the 75th percentile in subjects of the same age and sex in a large national survey. Lean adolescents were defined as those with a body-mass index between the 25th and 50th percentiles. Subjects who were still alive were interviewed in 1988 to obtain information about their medical history, weight, functional capacity, and other risk factors. For those who had died, information on the cause of death was obtained from death certificates.

Results. Overweight in adolescent subjects was associated with an increased risk of mortality from all causes and disease-specific mortality among men. but not among women. The relative risks among men were 1.8 (95 percent confidence interval. 1.2 to 2.7; P = 0.004) for mortality from all causes and 2.3 (95 percent confidence interval, 1.4 to 4.1; P = 0.002) for mortality from coronary heart disease. The risk of morbidity from coronary heart disease and atherosclerosis was increased among men and women who had been overweight in adolescence. The risk of colorectal cancer and gout was increased among men and the risk of arthritis was increased among women who had been overweight in adolescence. Overweight in adolescence was a more powerful predictor of these risks than overweight in adulthood.

Conclusions. Overweight in adolescence predicted a broad range of adverse health effects that were independent of adult weight after 55 years of follow-up.

]]> Aviva Must Ph.D. et al. Recent Advances in the Climate Change Biology Literature: Describing the Whole Elephant http://scholarworks.gvsu.edu/biopeerpubs/30 http://scholarworks.gvsu.edu/biopeerpubs/30 Mon, 23 Aug 2010 11:53:07 PDT Climate change biology is seeing a wave of new contributions, which are reviewed herein. Contributions treat shifts in phenology and distribution, and both document past and forecast future effects. However, many of the current wave of contributions are observational and correlational, and few are experimental in nature, and too often a conceptual framework in which to contextualize the results is lacking. An additional gap is the lack of effective cross-linking among areas of research, for example, connection of sea-level rise and climate change implications for distributions of species, or evolutionary adaptation studies with distributional shift studies. Although numerous important contributions have emerged in recent years, synthesis of this phenomenon and its consequences has not yet been achieved.

]]> A. Townsend Peterson et al. Age at Menarche: Accuracy of Recall After Thirty-Nine Years http://scholarworks.gvsu.edu/biopeerpubs/29 http://scholarworks.gvsu.edu/biopeerpubs/29 Wed, 11 Aug 2010 07:16:36 PDT Among 143 women whose menarcheal age was documented during a longitudinal growth study, recall 39 years after the even gave the following results: menarche was recalled as 0.2 years after earlier than the actual date (p<0.05), the standard deviation of recalled age was 0.3 years larger (p<0.01), and the coefficient of correlation, r, between actual and recalled age was 0.60 +/- s.e. 0.05.

]]> Albert Damon et al. Diel Fish Habitat Selection in a Tributary Stream http://scholarworks.gvsu.edu/biopeerpubs/28 http://scholarworks.gvsu.edu/biopeerpubs/28 Thu, 27 May 2010 13:29:18 PDT This study investigated the location and diel habitat preferences (at 100 m reach scale) of fish in a small tributary stream in late spring, early summer. During the day, coho (Oncorhynchus kisutch) preferred areas with more cover (deeper, greater extent of undercut banks) vs. night when LWD was preferred (Pearson correlation and step-wise MLR). Chinook (O. tshawytscha) exhibited an opposite pattern, preferring LWD during the day vs. higher velocity at night. This suggests these two potadromous species may be partitioning resources. Pooling coho, chinook and rainbow trout (O. mykiss) indicated reaches with more LWD were selected at night (r2=0.86, p=0.005) vs. deeper reaches during the day (r2=0.62, p=0.04). Although not measured specifically, we believe LWD supports more macroinvertebrate production vs. the predominantly sandy substrate. Thus, a potential mechanism behind the observed patterns in reach selection may be the tradeoff between food resource abundance vs. predation risk. The majority of captured fish were juveniles supporting the premise first order tributaries can serve as important nursery habitats, especially if they exhibit stable flow and thermal regimes.

]]> Andria K. Salas et al. Preliminary Global Assessment of Terrestrial Biodiversity Consequences of Sea-level Rise Mediated by Climate Change http://scholarworks.gvsu.edu/biopeerpubs/27 http://scholarworks.gvsu.edu/biopeerpubs/27 Wed, 21 Apr 2010 13:00:36 PDT Considerable attention has focused on the climatic effects of global climate change on biodiversity, but few analyses and no broad assessments have evaluated effects of sea-level rise on biodiversity. Taking advantage of new maps of marine intrusion under scenarios of 1 and 6 m sea-level rise, we calculated areal losses for all terrestrial ecoregions globally, with areal losses for particular ecoregions ranging from nil to complete. Marine intrusion is a global phenomenon, but its effects are most prominent in Southeast Asia and nearby islands, eastern North America, northeastern South America, and western Alaska. Making assumptions regarding faunal responses to reduced distributional areas of species endemic to ecoregions, we estimated likely numbers of extinctions caused by sea-level rise, and found that marine-intrusion-caused extinctions of narrow endemics are likely to be most prominent in northeastern South America, although anticipated extinctions in smaller numbers are scattered worldwide. This assessment serves as a complement to recent estimates of losses owing to changing climatic conditions, considering a dimension of biodiversity consequences of climate change that has not previously been taken into account.

]]> Shaily Menon et al. Ecological Niche Modeling and Local Knowledge Predict New Populations of <em>Gymnocladus assamicus</em> a Critically Endangered Tree Species http://scholarworks.gvsu.edu/biopeerpubs/26 http://scholarworks.gvsu.edu/biopeerpubs/26 Wed, 21 Apr 2010 12:19:45 PDT Gymnocladus assamicus is a critically endangered tree species endemic to northeastern India. Local inhabitants traditionally used this species for a variety of purposes. However, rapid population declines led to the species being considered extinct, until fieldwork in 2004 to 2007 identified 14 discrete populations of 1 to 7 trees each. To overcome constraints on field surveys imposed by the region’s remoteness and rugged terrain, we targeted areas of further field inventories by estimating the potential distribution of the species. Ecological niche modeling enabled us to identify 26 sites which the model predicted to be highly suitable for the species’ occurrence. We conducted rapid field surveys at 14 of the most accessible of these predicted sites. New populations were discovered at 5 of the 14 surveyed sites. In the remaining 12 less accessible sites, we interviewed residents from nearby villages and obtained indirect evidence of populations at 5 additional sites, which remain to be confirmed by direct field observations. This study demonstrates the utility of niche modeling as a tool for locating new populations of rare and endangered species. Our results will enhance ongoing efforts towards in situ conservation of this endangered species.

]]> Shaily Menon et al. Temperature Effects on Kinetics of Microbial Respiration and Net Nitrogen and Sulfur Mineralization http://scholarworks.gvsu.edu/biopeerpubs/25 http://scholarworks.gvsu.edu/biopeerpubs/25 Fri, 23 Oct 2009 13:00:13 PDT Global climate change may impact the cycling of C, N, and S in forest ecosystems because increased soil temperatures could alter rates of microbially mediated processes. We studied the effects of temperature on microbial respiration and net N and S mineralization in surface soils from four northern hardwood forests in the Great Lakes region. Soil samples were incubated in the laboratory at five temperatures (5, 10, 15, 20, and 25°C) for 32 wk. Headspace gas was analyzed for CO2-C at 2-wk intervals, and soils were extracted to determine inorganic N and S. Cumulative respired C and mineralized N and S increased with temperature at all sites and were strongly related (r2 = 0.67 to 0.90, significant at P = 0.001) to an interaction between temperature and soil organic C. Production of respired C and mineralized N was closely fit by first-order kinetic models (r2 0.94, P = 0.001), whereas mineralized S was best described by zero-order kinetics. Contrary to common assumptions, rate constants estimated from the first-order models were not consistently related to temperature, but apparent pool sizes of C and N were highly temperature dependent. Temperature effects on microbial respiration could not be accurately predicted using temperature-adjusted rate constants combined with a constant pool size of labile C. Results suggest that rates of microbial respiration and the mineralization of N and S may be related to a temperature-dependent constraint on microbial access to substrate pools. Simulation models should rely on a thorough understanding of the biological basis underlying microbially mediated C, N, and S transformations in soil.

]]> Neil W. MacDonald et al. Growth and Survival of Jack Pine Exposed to Simulated Acid Rain as Seedlings http://scholarworks.gvsu.edu/biopeerpubs/24 http://scholarworks.gvsu.edu/biopeerpubs/24 Fri, 23 Oct 2009 12:47:38 PDT In a previous study, jack pine (Pinus banksiana Lambert) seedlings grown under pH 2.5 simulated rain had larger shoot/root ratios and altered nutrition compared with seedlings grown with pH 4.7 rain. The objective of this study was to determine if these differences in initial seedling characteristics produced long-term effects on survival or growth of outplanted seedlings. Significantly (P < 0.05) greater diameter increment (4.3 vs. 4.0 cm) between ages 6 and 10 of jack pine treated with pH 2.5 rain as seedlings was consistent with a carryover effect from the initial treatments. However, no differences between treatments in jack pine diameter, height, or survival persisted to age 14. Results support recent recommendations that extended measurement periods may be necessary to fully assess the long-term effects of pollutant increases or decreases on growth of immature trees.

]]> Neil W. MacDonald et al. Soil Warming and Carbon Loss from a Lake States Spodosol http://scholarworks.gvsu.edu/biopeerpubs/23 http://scholarworks.gvsu.edu/biopeerpubs/23 Fri, 23 Oct 2009 12:39:54 PDT Elevated soil temperatures may increase C loss from soils by accelerating microbial respiration and dissolved organic C leaching. We evaluated the effect of elevated soil temperatures on C losses from a forest Spodosol by incubating soil cores from surface (Oa + A + E) and subsurface (Bhs) horizons at two seasonal temperature regimes. One regime simulated the normal course of soil temperatures in northern lower Michigan, and the other simulated soil temperatures representing an amount of warming that might occur under some global warming theory calculations. We measured the amounts of CO2-C respired and dissolved organic C leached from the soil cores during a 33-wk period. Microbial respiration rates, after adjustment for variation in initial rates, were significantly increased by soil warming and were greater in surface than in subsurface horizons. Warming significantly increased cumulative C respired, with greater losses from surface soils ( 50 mg C g-1 C) as compared with subsurface soils ( 25 mg C g-1 C). Mean quantities of dissolved organic C leached, ranging from 2.3 to 3.2 mg C g-1 C, did not differ significantly by soil horizon or temperature regime. Increased microbial respiration in surface soil horizons was the process most responsive to soil warming in the Spodosol samples we examined. Whether this is a short-term effect that would disappear once pools of labile C are exhausted, or represents a long-term response to soil warming, remains uncertain.

]]> Neil W. MacDonald et al. Native warm-season grass establishment on spotted knapweed-infested gravel mine spoils http://scholarworks.gvsu.edu/biopeerpubs/22 http://scholarworks.gvsu.edu/biopeerpubs/22 Fri, 23 Oct 2009 12:08:43 PDT We studied the establishment of native warm-season grasses on gravel mine spoils infested by spotted knapweed (Centaurea maculosa), an exotic perennial that is difficult to control on droughty, infertile sites. We applied factorial combinations of sewage sludge (o and 11.9 Mg ha−1 [5.3 tons ac−1]) and herbicide (none; 2,4-D; and glyphosate) to evaluate their effects on native grass establishment and on competition between native grasses and spotted knapweed. While native grasses were successfully established with all treatment combinations, sludge application reduced their densities. Warm season grass biomass subsequently increased rapidly on both sludge and control plots. Both herbicide treatments reduced density and biomass of knapweed during the first two years of the study, but glyphosate and sludge interacted to produce increased knapweed biomass during the third year. For this reason, it may be desirable to delay application of sludge amendments until warm-season grasses are well established in herbicide-treated areas. The response of knapweed to improved soil fertility was dependent on the degree of grass competition, and where this remained high, knapweed dominance was suppressed. While warm-season grasses appeared to compete successfully with spotted knapweed, additional control measures may be required to maintain grass dominance on this and similar knapweed-infested sites.

]]> Neil W. MacDonald et al. Hydrologic Events and Water Quality in the Pigeon River, Ottawa County, Michigan http://scholarworks.gvsu.edu/biopeerpubs/21 http://scholarworks.gvsu.edu/biopeerpubs/21 Fri, 23 Oct 2009 11:44:46 PDT The Pigeon River drains a 16,765-ha agricultural watershed in western Ottawa County, Michigan and discharges into south-central Lake Michigan. Extensive areas of wetlands in the upper watershed were drained in the 1920s, causing significantly altered hydrology characteristics by flashy discharges during storms and periods of snowmelt. We studied stream chemistry and hydrology for a four-year period between September, 1996, and October, 2000, to determine water quality status, to estimate annual nutrient exports, and to evaluate the effects of different seasonal flow types. Results of our study confirmed that the upper reaches of the Pigeon River experience chronically degraded water quality, with contributions from both nonpoint and point sources. As a result, the watershed has high annual rates of nutrient export (approximately 10.8 kg ha-1 inorganic N and 0.25 kg ha-1 PO4-P). With the influx of groundwater, change in land use to forest, and development of natural stream channel characteristics in the lower mainstream, water quality at baseflow in this section of the Pigeon River improves to the point where coldwater fish populations should persist. Inputs of degraded water during high flows, however, produce periods of environmental stress and the fish population in the lower Pigeon includes only a low number of pollution-tolerant, warmwater species. Large summer storms are biologically stressful because of increased temperatures and reduced dissolved oxygen levels, while spring storms and snowmelt contribute substantially to total nutrient suspended solids exports. Efforts to improve water quality in this and similar agricultural watersheds need to emphasize major reductions in the nonpoint source inputs through substantial improvements in land and water management practices. Wetland restoration and implementation of other stormwater retention practices in such watersheds also are required to reverse the acute impacts of high stormwater discharges caused by past drainage and steam channelization.

]]> Neil W. MacDonald et al. Environmental Stress Effects on Vigor, Mortality, and Growth in Northern Hardwood Forests Along a Pollution-Climate Gradient http://scholarworks.gvsu.edu/biopeerpubs/20 http://scholarworks.gvsu.edu/biopeerpubs/20 Fri, 23 Oct 2009 11:44:45 PDT Concern exists over the effects of interacting environmental stresses on the ecological integrity of temperate forests. Coincidence of sensitivity to drought, increasing occurrence of defoliation, and elevated pollutant deposition has produced speculation that northern hardwood forests may be susceptible to the increased climatic stresses projected for the Great Lakes region. The objective of our study was to examine relationships among environmental stress factors, vigor, mortality, and growth in northern hardwood forests located along a pollution-climate gradient in the Great Lakes region. Between 1987 and 1993, we quantified climatic variables, pollutant deposition, insect defoliation, and tree vigor and growth at five sites along this gradient. Drought and defoliation occurred to varying degrees during the study period. Symptoms of chronic environmental stress, such as cankers and epicormic branching, were most pronounced at extreme ends of the gradient. Periodic diameter increments decreased for suppressed trees but increased for dominant trees from north to south, primarily related to climatic factors. Variation in annual diameter increments was strongly associated with moisture availability, with diameter growth being greatly reduced during episodic droughts at the more southerly sites. At one site that experienced both drought and defoliation in 1988, worsening crown condition, elevated mortality, and reduced growth were consistent with the effects of acute levels of environmental stress. While most northern hardwood forests in the Great Lakes region are currently healthy, our results provide additional evidence that these forests are sensitive to increased severity of environmental stress, and may experience alterations in mortality and growth if climate changes as some have predicted.

]]> Neil W. MacDonald et al. Access to Mutualistic Endosymbiotic Microbes: An Underappreciated Benefit of Group Living http://scholarworks.gvsu.edu/biopeerpubs/19 http://scholarworks.gvsu.edu/biopeerpubs/19 Tue, 08 Sep 2009 14:23:16 PDT "The original publication is available at www.springerlink.com"

A central question in behavioral ecology has been why animals live in groups. Previous theories about the evolution of sociality focused on the potential benefits of decreased risk of predation, increased foraging or feeding efficiency, and mutual aid in defending resources and/or rearing offspring. This paper argues that access to mutualistic endosymbiotic microbes is an underappreciated benefit of group living and sets out to reinvigorate Troyer’s hypothesis that the need to obtain cellulolytic microbes from conspecifics influenced the evolution of social behavior in herbivores and to extend it to nonherbivores. This extension is necessary because the benefits of endosymbionts are not limited to nutrition; endosymbionts also help protect their hosts from pathogens. When hosts must obtain endosymbionts from conspecifics, they are forced to interact. Thus, complex forms of sociality may be more likely to evolve when hosts must repeatedly obtain endosymbionts from conspecifics than when endosymbionts can be obtained either directly from the environment, are vertically transmitted, or when repeated inoculations are not necessary. Observations from a variety of taxa are consistent with the ideas that individuals benefit from group living by gaining access to endosymbionts and the complexity of social behavior is associated with the mode of acquisition of endosymbionts. Ways to test this theory include (a) experiments designed to examine the effects of endosymbionts on host fitness and how endosymbionts are obtained and (b) using phylogenetic analyses to examine endosymbiont-host coevolution with the goal of determining the relationship between the mode of endosymbiont acquisition and host sociality.

]]> Michael P. Lombardo On the Evolution of Sexually Transmitted Diseases in Birds http://scholarworks.gvsu.edu/biopeerpubs/18 http://scholarworks.gvsu.edu/biopeerpubs/18 Tue, 08 Sep 2009 14:04:51 PDT "The definitive version is available at www.blackwell-synergy.com".

Sexually transmitted diseases (STDs) in animals are caused by pathogens that are transmitted during copulation. Birds have played an important role in the development of STD-centered theories of mating behavior. However, it is not known whether STDs exist in wild bird populations. While the avian cloaca with its dual functions of gamete transfer and excretion seemingly predisposes birds for the evolution of STDs, the life history patterns of most birds (i.e., seasonal breeders with relatively brief annual periods of sexual activity) suggest otherwise. The importance of STDs as selective forces that shape host biology depends on whether host life history patterns provide the necessary conditions for the evolution and spread of virulent pathogens that rely on host copulation for dispersal. Infrequent dispersal opportunities for microbes that rely on host sexual contact for dispersal should favor the evolution of low pathogen virulence, persistent infection, and lengthened infectious periods. I examine the disease characteristics of documented STDs that are relevant to birds in order to evaluate the (1) importance of STDs as selective forces in birds and (2) ecological conditions in which avian STDs are likely to be discovered. I conclude that socially monogamous short-lived birds with short breeding cycles and altricial nestlings (e.g., temperate zone songbirds) are not likely to have coevolved with highly virulent STDs which would be important selective forces. However, virulent STDs may have evolved in birds with one or more of the following life history characteristics: long life spans, long breeding cycles, multiple matings, and precocial young because these conditions produce increased opportunities for pathogen transmission and can favor the evolution of virulence. These life history characteristics are found and exaggerated in the birds for which STDs have been documented, the domesticated fowl and waterfowl.

]]> Michael P. Lombardo Individual, Temporal, and Seasonal Variation in Sperm Concentration in Tree Swallows http://scholarworks.gvsu.edu/biopeerpubs/17 http://scholarworks.gvsu.edu/biopeerpubs/17 Tue, 08 Sep 2009 13:29:21 PDT We determined sperm concentrations in Tree Swallows (Tachycineta bicolor) by manually expressing semen samples from males during prelaying, egg-laying, incubation, and nestling periods. Sperm concentrations varied by orders of magnitude (0-109 sperm mL-1) among males. Sperm concentrations were highest during the incubation period and lowest during the prelaying period. None of the samples collected during the prelaying, egg-laying, and incubation periods were devoid of sperm. In contrast, 45% of samples collected during the nestling period lacked sperm. Sperm concentrations (1) did not vary over the course of the morning during prelaying, egg-laying, and incubation periods but significantly increased during the nestling period; (2) did not vary with the date that samples were collected during prelaying, egg-laying, and incubation but significantly decreased with date during the nestling period; and (3) did not vary with the number of fertile females at the study site during any part of the breeding season. We hypothesize that the variations in sperm concentration arose from a combination of factors including intrinsic differences among males, daily patterns of sperm depletion associated with copulation, and an end-of-season decline in sperm production. If males vary in sperm availability then female Tree Swallows may benefit from pursuing extra-pair copulations as fertility insurance.

]]> Michael P. Lombardo et al. Repeated Sampling Affects Tree Swallow Semen Characteristics http://scholarworks.gvsu.edu/biopeerpubs/16 http://scholarworks.gvsu.edu/biopeerpubs/16 Fri, 04 Sep 2009 09:03:52 PDT Male Tree Swallows (Tachycineta bicolor) face intense sperm competition because mated pairs copulate frequently, extra-pair copulations are common, and females store sperm. We examined the effects of repeated sampling on the characteristics of Tree Swallow semen by manually expressing semen from 15 males immediately after capture (T0) and then hourly for 4 h (T1-T4). The semen characteristics of individual males varied in response to repeated sampling. The total number of sperm cells we obtained from each male over the 4-h sampling period varied from 104-107. Semen samples lacking sperm increased from 6.7% of T0 samples to 26.7-33.3% of subsequent samples. Forty percent of males provided at least one semen sample that lacked sperm. There were no significant differences among hourly samples in semen volume, sperm concentration, or in the total number of sperm cells obtained from each male. However, there were significant differences among males in each of these variables. Semen volumes represented small proportions of cloacal protuberance volumes. We did not detect significant correlations between total semen volumes or total number of sperm cells obtained from males from T0-T4 and cloacal protuberance volumes. Total semen volume and number of sperm cells obtained from T0-T4 significantly increased with date. However, sperm concentration was not significantly correlated with date. We did not detect significant correlations between semen characteristics and male morphology. Individual variation in responses to repeated sampling has implications for the copulatory strategies of male and female Tree Swallows.

]]> Michael P. Lombardo et al. Left-sided Directional Bias of Cloacal Contacts During Tree Swallow Copulations http://scholarworks.gvsu.edu/biopeerpubs/15 http://scholarworks.gvsu.edu/biopeerpubs/15 Fri, 04 Sep 2009 08:44:08 PDT Most female birds have only a left ovary and associated oviduct with entry to the oviduct on the left side of the urodeum of the cloaca. We hypothesized that male cloacal contacts during copulation would occur from the left side of females because this would put sperm closer to the entrance of the oviduct. We observed that cloacal contacts from the left outnumbered those from the right by a margin of 3:1 during tree swallow, Tachycineta bicolor, copulations at nestboxes in western Michigan in 1999. The directional bias of cloacal contacts may have an adaptive function.

]]> Aaron D. Petersen et al.