Robert D. Stevenson

The Thermal Dependence of Locomotion, Tongue Flicking, Digestion, and Oxygen Consumption in the Wandering Garter Snake

The body temperature (Tb) of garter snakes (Thamnophis elegans) can vary considerably in the course of a day (e.g., 4-33 C), and information on how Tb affects physiological and behavioral processes is required to evaluate the significance of that variation. We measured crawling speed, swimming speed, tongue-flicking rate, digestive rate, and oxygen consumption at Tbs of 5-35 C in snakes collected in eastern Washington and acclimated to September field photoperiod and temperature cycles. All functions were strongly dependent on Tb. The maximum speed of crawling (X̄ = 0.74 m s−1) occurred at Tb = 34.5 C; that of swimming (X̄ = 0.69 m s−1) occurred at Tb = 28.5. At < 30 C, the snakes crawled more slowly than they swam, but the reverse was true at higher Tb. At Tb = 30 C, the snakes moved their tongues up and down at a maximum rate of 22 Hz. Digestion rate increased sharply above 20 C, to a maximum of 0.45 mice/day within the Tb range of 25-35 C. All snakes regurgitated their meal at 10 C. The Q10 values for mass-specific oxygen consumption over the 5-15, 15-25, and 25-35 C Tb ranges were 2.4, 1.3, and 5.0, respectively. Among the performances studied, swimming speed was the least sensitive, and digestion rate the most sensitive, to Tb. FieldTb data indicate that all functions would be near maximum levels during the day but would be significantly reduced at night. We conclude that no single Tb is best for the ecological tasks of prey capture, predator avoidance, and energy conservation.

Condition indices for conservation: new uses for evolving tools

Biologists have developed a wide range of morphological, biochemical and physiological metrics to assess the health and, in particular, the energetic status of individual animals. These metrics originated to quantify aspects of human health, but have also proven useful to address questions in life history, ecology and resource management of game and commercial animals. We review the application of condition indices (CI) for conservation studies and focus on measures that quantify fat reserves, known to be critical for energetically challenging activities such as migration, reproduction and survival during periods of scarcity. Standard methods score fat content, or rely on a ratio of body mass rationalized by some measure of size, usually a linear dimension such as wing length or total body length. Higher numerical values of these indices are interpreted to mean an animal has greater energy reserves. Such CIs can provide predictive information about habitat quality and reproductive output, which in turn can help managers with conservation assessments and policies. We review the issues about the methods and metrics of measurement and describe the linkage of CIs to measures of body shape. Debates in the literature about the best statistical methods to use in computing and comparing CIs remain unresolved. Next, we comment on the diversity of methods used to measure body composition and the diversity of physiological models that compute body composition and CIs. The underlying physiological regulatory systems that govern the allocation of energy and nutrients among compartments and processes within the body are poorly understood, especially for field situations, and await basic data from additional laboratory studies and advanced measurement systems including telemetry. For now, standard physiological CIs can provide supporting evidence and mechanistic linkages for population studies that have traditionally been the focus of conservation biology. Physiologists can provide guidance for the field application of conditions indices with validation studies and development of new instruments.

Wavelength Discrimination and the Role of Ultraviolet Vision in the Feeding Behavior of Hawkmoths1

Nocturnal Sphingidae (hawkmoths or sphinx moths) are important pollinators in tropical forests. Hawkmoth flowers are typically white to the human eye. As the retinas of hawkmoths contain ultraviolet-sensitive photoreceptors, flower patterns reflecting ultraviolet wavelengths (that are not visible to humans) might be significant to sphingid feeding behavior. The flowers of ten hawkmoth-pollinated species were examined with an ultraviolet sensitive video system in Monteverde, Costa Rica. All were found to lack ultraviolet reflectance. A common hawkmoth species, Manduca sexta, whose range extends to Costa Rica was then used in laboratory free choice experiments to determine which wavelengths elicited proboscis extension, probing and drinking of sugar water. When offered a choice between artificial flowers or backlighted filters, Manduca strongly preferred to feed at those reflecting or transmitting only wavelengths longer than 400 nm, avoiding those that also included ultraviolet wavelengths. That is, feeding behavior was best elicited by stimuli that mimicked the reflectance of typical hawkmoth flowers. Feeding behavior must be primarily activated by either the green- or violet-sensitive mechanisms (or both) of the hawkmoth visual system, while concurrent activation of the ultraviolet-sensitive mechanism interferes with it.

Honeybee flight metabolic rate: does it depend upon air temperature?

SUMMARY Differing conclusions have been reached as to how or whether varying heat production has a thermoregulatory function in flying honeybees Apis mellifera. We investigated the effects of air temperature on flight metabolic rate, water loss, wingbeat frequency, body segment temperatures and behavior of honeybees flying in transparent containment outdoors. For periods of voluntary, uninterrupted, self-sustaining flight, metabolic rate was independent of air temperature between 19 and 37°C. Thorax temperatures (Tth) were very stable, with a slope of thorax temperature on air temperature of 0.18. Evaporative heat loss increased from 51 mW g-1 at 25°C to 158 mW g-1 at 37°C and appeared to account for head and abdomen temperature excess falling sharply over the same air temperature range. As air temperature increased from 19 to 37°C, wingbeat frequency showed a slight but significant increase, and metabolic expenditure per wingbeat showed a corresponding slight but significant decrease. Bees spent an average of 52% of the measurement period in flight, with 19 of 78 bees sustaining uninterrupted voluntary flight for periods of> 1 min. The fraction of time spent flying declined as air temperature increased. As the fraction of time spent flying decreased, the slope of metabolic rate on air temperature became more steeply negative, and was significant for bees flying less than 80% of the time. In a separate experiment, there was a significant inverse relationship of metabolic rate and air temperature for bees requiring frequent or constant agitation to remain airborne, but no dependence for bees that flew with little or no agitation; bees were less likely to require agitation during outdoor than indoor measurements. A recent hypothesis explaining differences between studies in the slope of flight metabolic rate on air temperature in terms of differences in metabolic capacity and thorax temperature is supported for honeybees in voluntary flight, but not under agitation.

Electronic Field Guides and User Communities in the Eco-informatics Revolution

The recognition that taxonomy is central to the conservation of biodiversity has reestablished the critical role of taxonomy in biology. However, many of the tools taxonomists produce for the identification and characterization of species, e.g., dichotomous keys, have been difficult to use and largely ignored by the general public in favor of field guides, which are essentially browsable picture guides. We review the role of field guides in species identification and discuss the application of a host of digital technologies to produce user-friendly tools for identification that are likely to greatly enhance species identification in the field by nonspecialists. We suggest that wider adoption of the citizen science model and the use of electronic field guides will enhance public understanding and participation in biodiversity monitoring.

EcoPhysiology and Conservation: The Contribution of Endocrinology and Immunology– Introduction to the Symposium

*Department of Biology, University of Massachusetts Boston, Boston, Massachusetts 02125-3393 †Department of Biology, Appalachian State University, 572 Rivers Street, Boone, North Carolina 28608 ‡Environmental Stewardship Concepts, Inc. Affiliate Associate Professor, Virginia Commonwealth University, Center for Environmental Studies, 1000 West Cary Street, P.O. Box 843050, Richmond, Virginia 23284-3050 §Department of Zoology, University of Washington, Box 351800, Seattle, Washington 98195-1800

Next-Generation Field Guides

To conserve species, we must first identify them. Field researchers, land managers, educators, and citizen scientists need up-to-date and accessible tools to identify organisms, organize data, and share observations. Emerging technologies complement traditional, book-form field guides by providing users with a wealth of multimedia data. We review technical innovations of next-generation field guides, including Web-based and stand-alone applications, interactive multiple-access keys, visual-recognition software adapted to identify organisms, species checklists that can be customized to particular sites, online communities in which people share species observations, and the use of crowdsourced data to refine machine-based identification algorithms. Next-generation field guides are user friendly; permit quality control and the revision of data; are scalable to accommodate burgeoning data; protect content and privacy while allowing broad public access; and are adaptable to ever-changing platforms and browsers. These tools have great potential to engage new audiences while fostering rigorous science and an appreciation for nature.

Ecophysiology and conservation: The contribution of energetics--introduction to the symposium.

Animal physiologists have begun making contributions to conservation biology based on their knowledge of endocrinology, immunology, and sensory biology. Contributions to this symposium use the perspective of energy and mass balance to examine questions about habitat usage, activity times, competition, foraging, reproduction, and body condition. Physiological constraints or requirements sculpt the behavioral and life history choices of individuals and provide mechanistic linkages with population processes and conservation policies.

Comparison of Macroinvertebrate Diversity and Community Structure among Perennial and Non-Perennial Headwater Streams

Abstract The relationships between stream flow regime and macroinvertebrate diversity, community structure, and functional feeding groups (FFG) were examined to determine if the biodiversity and macroinvertebrate fauna of non-perennial streams are significantly different from those of perennial streams. The study was conducted in northeastern Massachusetts at headwater stream sites of varying flow permanence (perennial, intermittent, and ephemeral). ANOVA confirmed no significant difference in Shannon-Wiener diversity (H′) between stream types, demonstrating that non-perennial streams maintain diverse and even macroinvertebrate communities. Whereas taxa richness was equal among intermittent and perennial sites, ephemeral richness was lower due to their significantly lower riffle richness. Qualitatively, two non-perennial sites were higher in grand total H′ diversity and taxa richness than perennial sites. Community structure was also related to flow regime, as hierarchical cluster analysis (HCA) based on taxa presence produced three distinct groups consistent with stream type, and FFG analysis provided further evidence of distinct communities, with a transition in FFGs from perennial to ephemeral sites. This study concludes that non-perennial streams are biologically diverse and maintain distinct benthic communities and therefore contribute to stream biodiversity and river ecosystems.

Natural history, distribution, and management of Lepidium latifolium (Brassicaceae) in New England

Abstract Lepidium latifolium (perennial pepperweed) is an herbaceous perennial, native to Europe and western Asia, that is now well established at many locations in Massachusetts and Connecticut. This species is considered a major invasive species in the western United States and appears likely to become invasive in the east if left unchecked. We showed that the distribution is greater than previously documented in New England and that populations appear to be expanding. Individuals of the species can produce thousands of seeds and we found that these seeds are tolerant to many days of inundation by salt water so that dispersal by tidal and river currents is likely. In addition, populations can expand at least 2 m/yr from growth by rhizomes, and densities exceeded 50 shoots/m2 in some areas. We identified 17 species of plants that are likely impacted by the expanding populations and 23 families of arthropods associated with L. latifolium in some of these areas. In wetland habitats, repeated pulling of shoots to remove much of the rhizome was effective at stabilizing or eradicating whole, well-defined populations. This treatment was most effective if continued for two or more growing seasons.