Christopher P. Bloch

Invertebrates, ecosystem services and climate change

The sustainability of ecosystem services depends on a firm understanding of both how organisms provide these services to humans and how these organisms will be altered with a changing climate. Unquestionably a dominant feature of most ecosystems, invertebrates affect many ecosystem services and are also highly responsive to climate change. However, there is still a basic lack of understanding of the direct and indirect paths by which invertebrates influence ecosystem services, as well as how climate change will affect those ecosystem services by altering invertebrate populations. This indicates a lack of communication and collaboration among scientists researching ecosystem services and climate change effects on invertebrates, and land managers and researchers from other disciplines, which becomes obvious when systematically reviewing the literature relevant to invertebrates, ecosystem services, and climate change. To address this issue, we review how invertebrates respond to climate change. We then review how invertebrates both positively and negatively influence ecosystem services. Lastly, we provide some critical future directions for research needs, and suggest ways in which managers, scientists and other researchers may collaborate to tackle the complex issue of sustaining invertebrate‐mediated services under a changing climate.

Cross-Scale Responses of Biodiversity to Hurricane and Anthropogenic Disturbance in a Tropical Forest

A bstractIn studies of biodiversity, considerations of scale—the spatial or temporal domain to which data provide inference—are important because of the non-arithmetic manner in which species richness increases with area (and total abundance) and because fine-scale mechanisms (for example, recruitment, growth, and mortality of species) can interact with broad scale patterns (for example, habitat patch configuration) to influence dynamics in space and time. The key to understanding these dynamics is to consider patterns of environmental heterogeneity, including patterns produced by natural and anthropogenic disturbance. We studied how spatial variation in three aspects of biodiversity of terrestrial gastropods (species richness, species diversity, and nestedness) on the 16-ha Luquillo Forest Dynamics Plot (LFDP) in a tropical forest of Puerto Rico was affected by disturbance caused by Hurricanes Hugo and Georges, as well as by patterns of historic land use. Hurricane-induced changes in spatial organization of species richness differed from those for species diversity. The gamma components of species richness changed after the hurricanes and were significantly different between Hurricanes Hugo and Georges. Alpha and two beta components of species richness, one related to turnover among sites within areas of similar land use and one related to variation among areas of different land use, varied randomly over time after both hurricanes. In contrast, gamma components of species diversity decreased in indistinguishable manners after both hurricanes, whereas the rates of change in the alpha component of species diversity differed between hurricanes. Beta components of diversity related to turnover among sites declined after both hurricanes in a consistent fashion. Those related to turnover among areas with different historic land uses varied stochastically. The immediate effect of hurricanes was to reduce nestedness of gastropod assemblages. Thereafter, nestedness increased during post-hurricane secondary succession, and did so in the same way, regardless of patterns of historic land use. The rates of change in degree of nestedness during secondary succession were different after each hurricane as a result of differences in the severity and extent of the hurricane-induced damage. Our analyses quantified temporal changes in the spatial organization of biodiversity of gastropod assemblages during forest recovery from hurricane-induced damage in areas that had experienced different patterns of historic human land use, and documented the dependence of biodiversity on spatial scale. We hypothesize that cross-scale interactions, likely those between the local demographics of species at the fine scale and the landscape configuration of patches at the broad scale, play a dominant role in affecting critical transfer processes, such as dispersal, and its interrelationship with aspects of biodiversity. Cross-scale interactions have significant implications for the conservation of biodiversity, as the greatest threats to biodiversity arise from habitat modification and fragmentation associated with disturbance arising from human activities.

Context-dependence of long-term responses of terrestrial gastropod populations to large-scale disturbance

Large-scale natural disturbances, such as hurricanes, can have profound effects on animal populations. Nonetheless, generalizations about the effects of disturbance are elusive, and few studies consider long-term responses of a single population or community to multiple large-scale disturbance events. In the last 20 y, two major hurricanes (Hugo and Georges) have struck the island of Puerto Rico. Long-term population trends of 17 species of terrestrial gastropod were evaluated to determine whether gastropods respond to hurricane disturbances in a consistent fashion. Some species increased, some decreased, and some exhibited no simple trend in density or spatial variability following disturbance. In addition, some species responded differently to the two hurricanes with respect to population density, absolute spatial variability, or relative spatial variability. Population responses probably hinge on trade-offs between sensitivity to microclimatic changes and resource availability resulting from the relocation of biomass from the canopy to the forest floor. The historical context within which a hurricane occurs may be as important, or more so, than the intensity of the storm, per se.

Long-term dynamics of tropical walking sticks in response to multiple large-scale and intense disturbances

Understanding the effects of disturbance and secondary succession on spatio-temporal patterns in the abundance of species is stymied by a lack of long-term demographic data, especially in response to infrequent and high intensity disturbances, such as hurricanes. Moreover, resistance and resilience to hurricane-induced disturbance may be mediated by legacies of previous land use, although such interactive effects are poorly understood, especially in tropical environments. We address these central issues in disturbance ecology by analyzing an extensive dataset, spanning the impacts of Hurricanes Hugo and Georges, on the abundance of a Neotropical walking stick, Lamponius portoricensis, in tabonuco rainforest of Puerto Rico during the wet and dry seasons from 1991 to 2007. By synthesizing data from two proximate sites in tabonuco forest, we show that resistance to Hurricane Hugo (97% reduction in abundance) was much less than resistance to Hurricane Georges (21% reduction in abundance). Based on a powerful statistical approach (generalized linear mixed-effects models with Poisson error terms), we documented that the temporal trajectories of abundance during secondary succession (i.e., patterns of resilience) differed between hurricanes and among historical land use categories, but that the effects of hurricanes and land use histories were independent of each other. These complex results likely arise because of differences in the intensities of the two hurricanes with respect to microclimatic effects (temperature and moisture) in the forest understory, as well as to time-lags in the response of L. portoricensis to changes in the abundance and distribution of preferred food plants (Piper) in post-hurricane environments.

Selective serotonin reuptake inhibitor (SSRI) toxicosis in cats: 33 cases (2004–2010)

OBJECTIVE To evaluate a population of cats with selective-serotonin reuptake inhibitor (SSRI) toxicosis and characterize the population affected, list products ingested, the clinical signs observed, treatments performed, length of hospitalization, patient outcome, and overall prognosis. DESIGN Retrospective study from 2004 to 2010. SETTING Referral veterinary center. ANIMALS Thirty-three witnessed cat SSRI ingestions. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS The medical records of cats with a witnessed SSRI ingestion identified by review of an animal poison control center electronic database were evaluated. The most common SSRIs ingested were venlafaxine (Effexor; 12/33; 36%), fluoxetine (Prozac; 12/33; 36%), citalopram (Celexa; 6/33; 18%), and escitalopram (Lexapro; 3/33; 9%). Overall, 24% of cats (8/33) became symptomatic, while 76% (25/33) remained asymptomatic. Of the symptomatic cats, sedation was the most common clinical sign (6/8; 75%), followed by gastrointestinal signs (4/8; 50%), central nervous system stimulation (1/8; 13%), cardiovascular signs (1/8; 13%), and hyperthermia (1/8; 13%). Veterinary care was sought in 20 cats (20/33; 61%). Sixteen cats (16/20; 80%) were hospitalized, while 4 cats (4/20; 20%) were treated as outpatients. Treatment for hospitalized patients included administration of IV fluid therapy (14/16; 88%), activated charcoal (12/16; 75%), anti-arrhythmic agents (7/16; 44%), methocarbamol (6/16; 38%), cyproheptadine (6/16; 38%), anti-emetics (5/16; 31%), and sedation (5/16; 31%). Diagnostics included blood work (7/16; 44%), blood pressure measurement (3/16; 19%), and electrocardiogram monitoring (2/16; 13%). Mean hospitalization time for all cases of SSRI ingestion was 14.6 ± 7.8 hours (n = 16). All symptomatic cats in this study (8/8; 100%) had resolution of clinical signs and survived to discharge. CONCLUSIONS The prognosis for SSRI ingestion in this population of cats was excellent. Decontamination and supportive care for at least 12-24 hours can be considered in cats with SSRI ingestion, particularly venlafaxine to monitor resolution of clinical signs.

Population Dynamics of Oryzomys palustris and Microtus pennsylvanicus in Virginia Tidal Marshes

Abstract Oryzomys palustris (marsh rice rat) and Microtus pennsylvanicus (meadow vole) cohabit coastal marshes in the mid-Atlantic US. Both were live-trapped for 23 months at two tidal marsh sites in Virginia to assess their demography near the margins of their distributions. In the presence of dense vegetation, population dynamics of the two species were seasonal and positively correlated, with densities declining through the winter. At the more sparsely vegetated site, densities of both species were lower, and densities of M. pennsylvanicus were negatively correlated with those of O. palustris. Patterns of reproduction differed between the species. O. palustris was reproductively most active in summer and least so in winter, whereas female M. pennsylvanicus decreased reproductive activity during summer.

Density compensation suggests interspecific competition is weak among terrestrial snails in tabonuco forest of Puerto Rico

Abstract. In the Luquillo Experimental Forest (LEF) of Puerto Rico, composition of terrestrial gastropod assemblages exhibits little temporal variation, even in response to intense hurricanes. One might therefore expect snail assemblages to be equilibrial and structured by interspecific interactions such as competition. If competition is strong and persistent throughout an assemblage, then it should manifest as density compensation (a negative correlation in population density between competitors) and be most pronounced for species pairs that are morphologically similar, as they should compete most strongly for resources. We assessed the degree to which terrestrial snails in the LEF exhibit density compensation, from both spatial and temporal perspectives. In general, density compensation was weak, especially from a spatial perspective. Moreover, the degree of density compensation was not significantly associated with dissimilarity in body size or shell shape. These results suggest that external factors such as predation or disturbance probably maintain population densities at low enough levels that the effects of interspecific competition do not become intense or persistent enough to mold patterns of assemblage structure for terrestrial snails.

Comparison of a new hydro-surgical technique to traditional methods for the preparation of full-thickness skin grafts from canine cadaveric skin and report of a single clinical case

OBJECTIVE To compare the hydro-surgical technique to traditional techniques for removal of subcutaneous tissue in the preparation of full-thickness skin grafts. STUDY DESIGN Ex vivo experimental study and a single clinical case report. SAMPLE POPULATION Four canine cadavers and a single clinical case. METHODS Four sections of skin were harvested from the lateral flank of recently euthanatized dogs. Traditional preparation methods used included both a blade or scissors technique, each of which were compared to the hydro-surgical technique individually. Preparation methods were compared based on length of time for removal of the subcutaneous tissue from the graft, histologic grading, and measurable thickness as compared to an untreated sample. RESULTS The hydro-surgical technique had the shortest skin graft preparation time as compared to traditional techniques (p = 0.002). There was no significant difference in the histological grading or measurable subcutaneous thickness between skin specimens. CLINICAL SIGNIFICANCE The hydro-surgical technique provides a rapid, effective debridement of subcutaneous tissue in the preparation of full-thickness skin grafts. There were not any significant changes in histological grade and subcutaneous tissue remaining among all treatment types. Additionally the hydro-surgical technique was successfully used to prepare a full-thickness meshed free skin graft in the reconstruction of a traumatic medial tarsal wound in a dog.

Effects of urbanization on the population structure of freshwater turtles across the United States: Urbanization Effects on Turtles

Landscape-scale alterations that accompany urbanization may negatively affect the population structure of wildlife species such as freshwater turtles. Changes to nesting sites and higher mortality rates due to vehicular collisions and increased predator populations may particularly affect immature turtles and mature female turtles. We hypothesized that the proportions of adult female and immature turtles in a population will negatively correlate with landscape urbanization. As a collaborative effort of the Ecological Research as Education Network (EREN), we sampled freshwater turtle populations in 11 states across the central and eastern United States. Contrary to expectations, we found a significant positive relationship between proportions of mature female painted turtles (Chrysemys picta) and urbanization. We did not detect a relationship between urbanization and proportions of immature turtles. Urbanization may alter the thermal environment of nesting sites such that more females are produced as urbanization increases. Our approach of creating a collaborative network of scientists and students at undergraduate institutions proved valuable in terms of testing our hypothesis over a large spatial scale while also allowing students to gain hands-on experience in conservation science.

Long-Term Effects of an Invasive Shore Crab on Cape Cod, Massachusetts

Abstract — Invasive species can cause dramatic changes in the structure of intertidal communities. In some systems, however, abundance or impacts of invaders may peak 10–20 years after invasion and decline thereafter. Hemigrapsus sanguineus (Asian Shore Crab) has been established at Sandwich, MA, on the north side of Cape Cod, since the mid-1990s. This study documented population dynamics of the Asian Shore Crab and 3 species of prey or competitors (Carcinus maenas [Green Crab], Mytilus edulis [Blue Mussel], and Littorina littorea [Common Periwinkle]) over 10 years. An additional goal of the study was to determine whether population growth of the Asian Shore Crab has slowed since its initial establishment. Density of the Asian Shore Crab increased over time, with no evidence of a density-dependent decrease in per capita growth rates. Concurrently, density of the Green Crab and the Blue Mussel declined, but there was no significant temporal trend in density of the Common Periwinkle. If observations at Sandwich are representative of sites north of Cape Cod, populations of the Asian Shore Crab are growing rapidly, and dramatic changes in community structure may be widespread.