Signals for Parent-Offspring Recognition: Strong Sib-Sib Call Similarity in Cliff Swallows but not Barn Swallows

We tested the prediction that the calls of sibling cliff swallow (Hirundo pyrrhonota) chicks are more similar than those of sibling barn swallow (Hirundo rustica) chicks. This prediction was derived from the hypothesis that the call of the colonial cliff swallow, but not the call of the noncolonial barn swallow, has been selected for signature function (i.e., for individual distinctiveness). In Study 1 we examined the calls of 22 cliff swallow sibling pairs and 23 barn swallow sibling pairs. The intraclass correlations for 4 of the 5 cliff swallow variables were significantly different from zero, and each of the 4 was approximately 0.5. Only one of the 4 barn swallow call variables was significantly different from zero. In a discriminant-function analysis of these data, cliff swallow chick calls were correctly identified as to sibship in 82 % of the cases, barn swallow chick calls in only 46 % of the cases. In Study 2 we cross-fostered eggs between cliff swallow nests to create foster sibships (all chicks in a nest were unrelated). We found no similarities among foster sib calls, and thus no evidence for call imitation of the calls of sibs or parents, suggesting that genetic differences are the main source of variance in cliff swallow chick calls.     

Recapture Heterogeneity in Cliff Swallows: Increased Exposure to Mist Nets Leads to Net Avoidance

Ecologists often use mark-recapture to estimate demographic variables such as abundance, growth rate, or survival for samples of wild animal populations. A common assumption underlying mark-recapture is that all animals have an equal probability of detection, and failure to meet or correct for this assumption–as when certain members of the population are either easier or more difficult to capture than other animals–can lead to biased and inaccurate demographic estimates. We built within-year and among-years Cormack-Jolly-Seber recaptures-only models to identify causes of capture heterogeneity for a population of colonially nesting cliff swallows (Petrochelidon pyrrhonota) caught using mist-netting as a part of a 20-year mark-recapture study in southwestern Nebraska, U.S.A. Daily detection of cliff swallows caught in stationary mist nets at their colony sites declined as the birds got older and as the frequency of netting at a site within a season increased. Experienced birds’ avoidance of the net could be countered by sudden disturbances that startled them into a net, such as when we dropped a net over the side of a bridge or flushed nesting cliff swallows into a stationary net positioned at a colony entrance. Our results support the widely held, but seldom tested, belief that birds learn to avoid stationary mist nets over time, but also show that modifications of traditional field methods can reduce this source of recapture heterogeneity.     

Restoring Native Perennial Grasses to Rural Roadsides in the Sacramento Valley of California: Establishment and Evaluation

Along rural roadsides of the Sacramento Valley of California, we seeded native and non-native perennial grasses to gauge their potential value in roadside vegetation management programs. In trial I (polycultures), three seeded complexes and a control (resident vegetation only) were tested. Each seeded plant complex included a different mix of perennial grasses seeded into each of several roadside topographic zones. The seeded levels of plant complex were: native perennial grasses 1 (8 species); native perennial grasses 2 (13 species); and non-native perennial grasses (3 species). In trial II, plots were seeded to monocultural plots of 15 accessions of native Californian and three cultivars of non-native perennial grasses. Plots in both trials were seeded during January 1992 and evaluated for three successive years.     

Fish Communities of the Sacramento River Basin: Implications for Conservation of Native Fishes in the Central Valley, California

The associations of resident fish communities with environmental variables and stream condition were evaluated at representative sites within the Sacramento River Basin, California between 1996 and 1998 using multivariate ordination techniques and by calculating six fish community metrics. In addition, the results of the current study were compared with recent studies in the San Joaquin River drainage to provide a wider perspective of the condition of resident fish communities in the Central Valley of California as a whole. Within the Sacramento drainage, species distributions were correlated with elevational and substrate size gradients; however, the elevation of a sampling site was correlated with a suite of water-quality and habitat variables that are indicative of land use effects on physio-chemical stream parameters. Four fish community metrics – percentage of native fish, percentage of intolerant fish, number of tolerant species, and percentage of fish with external anomalies – were responsive to environmental quality. Comparisons between the current study and recent studies in the San Joaquin River drainage suggested that differences in water-management practices may have significant effects on native species fish community structure. Additionally, the results of the current study suggest that index of biotic integrity-type indices can be developed for the Sacramento River Basin and possibly the entire Central Valley, California. The protection of native fish communities in the Central Valley and other arid environments continues to be a conflict between human needs for water resources and the requirements of aquatic ecosystems; preservation of these ecosystems will require innovative management strategies.     

Parasitism in bivalves from an Arctic ecosystem

In arctic ecosystems parasitism seems less conspicuous than in more diverse tropical ecosystems. However, several host-parasite relations may be a burden in Arctic ecosystems and modify energy-flow patterns. Four different localities of the shallow shelf off Godhavn, West Greenland, were studied with regard to biomass, production and life cycles of selected bivalve and polychaete species. The following important parasite-bivalve associations were found: the athecate hydroidMonobrachium parasitum onMacoma calcarea; the digenetic trematodeGymnophallus somateriae inHiatella byssifera; an unidentified species of turbellarian inHiatella byssifera; and the nemerteanMalacobdella grossa inMya truncata. In the bivalvesMytilus edulis, Serripes groenlandicus andCardium ciliatum only few parasites were detected. Parasitism seems to follow the general trend observed in Arctic ecosystems which exhibit low species diversities and high numbers of individuals.     

Avian Viral Pathogens in Swallows,Zimbabwe

We sampled 417 swallows in a wetland ecosystem of Zimbabwe in February 2010 and October 2011. RT-PCR tests revealed circulation of avian paramyxovirus type I, avian influenza and West Nile disease viruses in these populations. We discuss the relevance of these findings in relation to what is known on the epidemiology of these viruses in these hosts and in relation to the host ecology. We conclude with recommendations to focus more research on Passeriformes in disease ecology and in particular on the hirundinidae family.     

Parasitism proteins in nematode-plant interactions

The current battery of candidate parasitism proteins secreted by nematodes to modify plant tissues for parasitism includes cell-wall-modifying enzymes of potential prokaryotic origin, multiple regulators of host cell cycle and metabolism, proteins that can localize to the plant cell nucleus, potential suppressors of host defense, mimics of plant molecules, and a relatively large cadre of predicted novel nematode parasitism proteins. Phenotypic effects of expressing nematode parasitism proteins in transformed plant tissues, protein-protein interaction assays, and RNA-mediated interference (RNAi) analyses are currently providing exciting evidence of the biological role of candidate nematode secreted parasitism proteins and identifying potential novel means of developing transgenic resistance to nematodes in crops.     

Pre-historic cucurbits from the Valley of Oaxaca

About 180 specimens of cucurbits were recovered from the Guila Naquitz Cave in the Valley of Oaxaca, Mexico, from strata dated at 8750-7840 B.C. to 1500 A.D. by Carbon- 14 analyses. 4 Almost 60% of the cucurbit specimens were of wild species of Cucurbita. A single seed may be that of the perennial squash or fig- leaf gourd, C. ficifolia Bouch é. All other cultivated squash material was C. pepo L., the summer squash. Cucurbita pepo prefers cool, dry environmental conditions. This suggests that farmers utilized the cave on a seasonal basis, because cultivars of C. pepo mature later and store better than those of C. moschata Poir. or C. mixta Pang., which would normally be the species expected to be cultivated at this latitude. Specimens of bottle gourd, Lagenaria siceraria (Mol.) Standl., were comparatively rare and comprised only 10% of the total. The scarcity of bottle gourd remains suggests that these gourds were not important for containers and household, use even in preceramic levels, or that they simply did not break many of their vessels during the limited time they occupied the cave. A second possibility is that agriculture was carried out at higher and cooler elevations, which C. pepo prefers but which are unfavorable for Lagenaria. A few Apodanthera seeds were found at all levels.     

Trends in the Evolution of Insect Parasitism by Nematodes as Inferred from Fossil Evidence

Fossil evidence can reveal a wealth of information regarding entomogenous nematodes. Amber is an excellent medium for the preservation of such fossils because it protects delicate organisms like nematodes, often along with their insect hosts. Such fossils establish a baseline for the appearance and continuation of parasite lineages as well as parasite-host associations. Thus far, fossil records of insect parasites have been discovered in the following nematode groups: terrestrial and aquatic Mermithidae, Tetradonematidae, Iotonchidae, Diplogasteridae, Allantonematidae, Sphaerulariidae, and Rhabditidae. Records date from 15 to 130 million years, demonstrating that these associations have existed for a considerable length of time.     

Sibling Recognition in Bank Swallows (Riparia riparia)

Observations of the behavior of newly-fledged bank swallows suggest that sibling recognition may be a mechanism promoting location of the home burrow in their large, dense colonies and of cohesion of family groups following departure from the burrow. We tested for sibling recognition in the field by comparing the antiphonal response of sibling groups to the recorded calls of own vs. unrelated sibling groups. Birds responded more to the calls of their own groups. In a laboratory experiment we raised chicks in isolation from 8–10 to 20 days of age and exposed them to a call of an unrelated chick. When tested in a choice situation at 15–20 days, chicks approached the familiar call in preference to a different call which they had not previously heard. We suggest that sibling recognition is based on familiarity, i.e., that it requires a period in which the calls of siblings are learned.     

Determinants of Compatibility in Mollusc-Trematode Parasitism

The low prevalence of schistosome-infected snails in hyperendemichabitats, and the demonstrated ability of snails, in general,to recognize and eliminate a myriad of foreign substances and/orinfectious agents, lead to the postulate that host resistanceto larval trematodes must be considered the "rule," while susceptibility(compatibility) represents an exceptional occurrence. In thisreview, we discuss a variety of possible mechanisms by whichcompatibility between trematodes and their molluscan host mightbe attained. Included among these are parasite mimicry of snailhost molecules, prevention of opsonization, interference withhemocyte behavior or differential stimulation of hemocyte metabolicprocesses. Evidence that compatibility is the result of theability of larvae to resist toxic host molecules or to acquireprotective host components on their surface membranes is lacking.Clearly, there are multiple variables of both host and parasiteorigin which ultimately determine compatibility. Careful identificationand dissection of these variables will be required before weachieve a complete understanding of how compatible snail-trematodeassociations are established and maintained.