Conclusions Drawn from the Malformity and Disease Session, Midwest Declining Amphibians Conference, 1998

While the general problem of amphibian declines is well known, no issue recently has engendered as much concern by the public as amphibian malformities (Ouellet et al. 1996, Tietge 1996, Gray 1998, Helgen et al. 1998a and 1998b, D. Johnson 1998, T. Johnson 1998, Meteyer and Converse 1998). As a result, Gary Casper, Chris Phillips and I decided to assemble this symposium. The session was open to anyone who wished to participate. Nineteen papers were presented (there was one cancellation) and a panel discussion followed. I will organize this summary of, and conclusions drawn from, our symposium into two sections: 1) the ecological importance and 2) proximal causes of the amphibian malformities that now command our attention

Richard Bovbjerg and The Iowa Lakeside Laboratory

In the spring of 1977, in Ames, a struggling biology major who had earlier shown some promise was ordered by his advisor: Go to Lakeside Lab and take Dick Bovbjerg\u27s Aquatic Ecology course. I did and it worked. I\u27ve parlayed that early potential into a career. And like so many others I return to Lakeside, the first time to take another course, then to do my Master\u27s research. More recently I come back to teach the Field Vertebrate Zoology course. Likewise, Dick has shifted from mentor to colleague, and we\u27ve co-authored a paper (Lannoo and Bovbjerg, 1985). Now, I am truly honored to be the special editor of this issue commemorating Dick\u27s 70th birthday and his retirement as the Director of the Iowa Lakeside Laboratory

AMPHIBIAN AND REPTILE COLONIZATION OF RECLAIMED COAL SPOIL GRASSLANDS

While habitat loss is a major driver of amphibian and reptile declines globally, a subset of post-industrial landscapes, reclaimed and restored, are creating habitat for these animals. In a previous work, we showed that amphibians and reptiles use reclaimed and restored grasslands. In the present work we quantify captures at drift-fence/pitfall trap arrays over two consecutive years and show that several species of amphibians are not only successfully reproducing but that juveniles are being recruited into the population. In particular, 15,844 amphibians and 334 reptiles representing 25 species (14 amphibians, 11 reptiles) were captured at drift fences in 2009 and 2010. Nine additional reptile species were found opportunistically while conducting other research activities at the study site. Out of a total of 8,064 metamorphosing juveniles we detected 126 malformations, a 1.6% rate. The major malformation types were limbs missing (amelia) or foreshortened (ectromely), eye discolorations, and digits foreshortened (ectrodactyly) or small (brachydactyly). Our data show that reclaimed, restored, and properly managed landscapes can support reproducing populations of amphibians and reptiles with low malformation rates, including species in decline across other portions of their range

AMPHIBIAN RESPONSE TO A LARGE-SCALE HABITAT RESTORATION IN THE PRAIRIE POTHOLE REGION

Over the next half-century, scientists anticipate that nearly one third of the currently recognized 7,450 amphibian species will become extinct. Many organizations have responded to the challenge of conserving amphibian biodiversity, some indirectly. Under the auspices of the Iowa Great Lakes Management Plan, the United States Fish and Wildlife Service, Department of Natural Resources, and their partners have been implementing habitat restoration efforts designed to protect water quality, provide recreational opportunities, and benefit wildlife at the regional level. With this program, over 130 wetlands have been created in the past 30 years on recently purchased public lands—one of the largest wetland restoration projects conducted in the Prairie Pothole Region of the Great Plains. While amphibians were not the main target of these restorations, we show that in response, 121 new breeding populations of native Northern Leopard Frogs (Lithobates pipiens; n = 80) and Eastern Tiger Salamanders (Ambystoma tigrinum; n = 41) have been established; in addition, we found 19 populations of non-native American Bullfrogs (L. catesbeianus). Using the program PRESENCE, we show that leopard frog occupancy was greatest in newer (<18 years old), intermediate-sized wetlands, and that tiger salamander occupancy was greatest in small wetlands without fish and larval bullfrogs. These data imply that because native amphibians responded positively to these newly established wetlands, habitat availability has likely been a factor in limiting population numbers. Further, these data suggest the presence of fishes and introduced bullfrogs interferes with the ability of tiger salamanders to colonize restored wetlands

Distribution, Dispersion, and Behavioral Ecology of the Land Snail Oxyloma retusa (Succineidae)

Oxyloma retusa is a land snail found only along moist margins of freshwater wetlands and lakes. This study quantifies the dispersal pattern of O. retusa along permanent and temporary wetlands and considers the environmental factors to which this snail responds. On a lake shore, snail density peaked in the second or third meter from the water\u27s edge but snails were present in decreasing numbers up to 7 meters inland. In field experiments, marked snails, initially distributed evenly along a shore transect, assumed a similar dispersion pattern within 72 hours. Two color morphs had overlapping but zonal dispersions, the amber morph farther inland than the dark. In drying ponds, snails followed the retreating shoreline. In reflooding of such ponds snails responded by crawling with the water\u27s leading edge or ascending emergent vegetation. It is clear that O. retusa actively selects a precise microhabitat. This habitat selection appears dependent on a combination of physical and biotic factors acting separately and in combination

The Tiger Salamander

Tiger salamanders are harmless members of the Class Amphibia which easily lend themselves to observation and experimentation. As the name amphibian implies, these salamanders have two life forms, an aquatic larval stage and a terrestrial adult stage. Both forms are common and widespread throughout Iowa, yet adults, being terrestrial and less seasonal, are encountered more frequently than the larvae

Time to Metamorphosis as a Function of Larval Size in a Population of Ambystoma tigrinum Salamanders Consisting of Cannibal and Typical Morph Phenotypes

Salamander larvae of the species Ambystoma tigrinum are dimorphic in northwestern Iowa. In addition to common typical morphs, there exist rare, specialized cannibal morphs, which are induced environmentally by crowding. Cannibal morph phenotypes are characterized morphologically by their large size, proportionately large heads and hypertrophied vomerine teeth, and behaviorally by facultative cannibalism. During metamorphosis amphibians are particularly sensitive to predation. To help understand why cannibal morphs are uncommon, we have raised cannibal and typical morphs in isolation and under crowded conditions to compare the timing and duration of metamorphosis between these morphs. Results show that larger larvae, most of which exhibit characteristics intermediate between cannibal and typical morphs, and three true cannibal morphs, do not exhibit a discrete time to metamorphosis; they are among the first, but not the first animals to metamorphose. Therefore cannibal morphs may be no more vulnerable to predation than typical morphs during this critical period, and we do not consider that our metamorphic bottleneck hypothesis is supported. Overall, crowded larvae metamorphosed an average of three to four days earlier than isolates and were an average of 6 mm smaller at metamorphosis

Landscape Associations of Frog and Toad Species in Iowa and Wisconsin, U.S.A.

Landscape habitat associations of frogs and toads in Iowa and Wisconsin were tested to determine whether they support or refute previous general habitat classifications. We examined which Midwestern species shared similar habitats to see if these associations were consistent across large geographic areas (states). Rana sylvatica (wood frog), Hyla versicolor (eastern gray treefrog), Pseudacris crucifer (spring peeper), and Acris crepitans (cricket frog) were identified as forest species, P. triseriata (chorus frog), H. chrysoscelis (Cope\u27s gray treefrog), R. pipiens (leopard frog), and Bufo americanus (American toad) as grassland species, and R. catesbeiana (bullfrog), R. clamitans (green frog), R. palustris (pickerel frog), and R. septentrionalis (mink frog) as lake or stream species. The best candidates to serve as bioindicators of habitat quality were the forest species R. sylvatica, H. versicolor, and P. crucifer, the grassland species R. pipiens and P. triseriata, and a cold water wetland species, R. palustris. Declines of P. crucifer, R. pipiens, and R. palustris populations in one or both states may reflect changes in habitat quality. Habitat and community associations of some species differed between states, indicating that these relationships may change across the range of a species. Acris crepitans may have shifted its habitat affinities from open habitats, recorded historically, to the more forested habitat associations we recorded. We suggest contaminants deserve more investigation regarding the abrupt and widespread declines of this species. Interspersion of different habitat types was positively associated with several species. A larger number of wetland patches may increase breeding opportunities and increase the probability of at least one site being suitable. We noted consistently negative associations between anuran species and urban development. Given the current trend of urban growth and increasing density of the human population, declines of amphibian populations are likely to continue

Sex-related differences in aging rate are associated with sex chromosome system in amphibians

Sex-related differences in mortality are widespread in the animal kingdom. Although studies have shown that sex determination systems might drive lifespan evolution, sex chromosome influence on aging rates have not been investigated so far, likely due to an apparent lack of demographic data from clades including both XY (with heterogametic males) and ZW (heterogametic females) systems. Taking advantage of a unique collection of capture-recapture datasets in amphibians, a vertebrate group where XY and ZW systems have repeatedly evolved over the past 200 million years, we examined whether sex heterogamy can predict sex differences in aging rates and lifespans. We showed that the strength and direction of sex differences in aging rates (and not lifespan) differ between XY and ZW systems. Sex-specific variation in aging rates was moderate within each system, but aging rates tended to be consistently higher in the heterogametic sex. This led to small but detectable effects of sex chromosome system on sex differences in aging rates in our models. Although preliminary, our results suggest that exposed recessive deleterious mutations on the X/Z chromosome (the "unguarded X/Z effect") or repeat-rich Y/W chromosome (the "toxic Y/W effect") could accelerate aging in the heterogametic sex in some vertebrate clades.Peer reviewe

Do Frogs Get Their Kicks on Route 66? Continental U.S. Transect Reveals Spatial and Temporal Patterns of Batrachochytrium dendrobatidis Infection

The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component—the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations