The Nene Branta sandvicensis Recovery Initiative: research against extinction

Since 1960, about 2150 Hawaiian Geese or Nene Branta sandvicensis were reintroduced in Hawaii to supplement the remaining wild population of about 30 birds. These geese were released mostly in high mountain sanctuaries. These sites became unsuitable during prolonged drought and the few surviving birds were those which had moved away from the release sites. The geese that survived had moved to, or were released near, agricultural pasture land. About 600 Nene are currently living in the wild; numbers are declining on the island of Hawaii, stable on Maui and increasing on Kauai. Management priorities include enhancement of grasslands, predator control and maximizing genetic diversity. To enable the species to recover, management will probably have to be large scale, intensive and prolonged. Further released captive-bred or translocated Nene should have access to enhanced habitats after predators have been controlled.     

Priority effects among young‐of‐the‐year fish: reduced growth of bluegill sunfish (Lepomis macrochirus) caused by yellow perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age‐0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age‐0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age‐0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (<4 mg wet weight L^?1), predation by age‐0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. <1.0 mg wet weight L^?1). The exception was 2005 when age‐0 yellow perch were absent. 3. Growth of age‐0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (>4 mg wet weight L^?1) compared with the other years (<0.2 mg wet weight L^?1). 4. We conclude that age‐0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age‐0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age‐0 yellow perch when competing with age‐0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age‐0 yellow perch densities.     

Food plant and herbivore host species affect the outcome of intrinsic competition among parasitoid larvae

1. In nature, several parasitoid species often exploit the same stages of a common herbivore host species and are able to coexist despite competitive interactions amongst them. Less is known about the direct effects of resource quality on intrinsic interactions between immature parasitoid stages. The present study is based on the hypothesis that variation in the quality or type of plant resources on which the parasitoids indirectly develop may be complementary and thus facilitate niche segregation favouring different parasitoids in intrinsic competition under different dietary regimes. 2. The present study investigated whether two herbivore species, the cabbage butterflies Pieris brassicae and Pieris rapae (Pieridae), and the quality of two important food plants, Brassica oleracea and Brassica nigra (Brassicaceae), affect the outcome of intrinsic competition between their primary larval endoparasitoids, the gregarious Cotesia glomerata (Braconidae) and the solitary Hyposoter ebeninus (Ichneumonidae). 3. Hyposoter ebeninus is generally an intrinsically superior competitor over C. glomerata. However, C. glomerata survived more antagonistic encounters with H. ebeninus when both developed in P. brassicae rather than in P. rapae caterpillars, and while its host was feeding on B. nigra rather than B. oleracea. Moreover, H. ebeninus benefitted from competition by its higher survival in multiparasitised hosts. 4. These results show that both plant and herbivore species mediate the battleground on which competitive interactions between parasitoids are played out and may affect the outcomes of these interactions in ways that enable parasitoids to segregate their niches. This in turn may promote coexistence among parasitoid species that are associated with the same herbivore host.     

The Effect of Vitamin A on Cellular Differentiation and Mucous Glycoprotein Synthesis in Long-Term Rat Tracheal Organ Cultures

Rat tracheal explants maintained as organ cultures exhibited a normal mucociliary epithelium for at least 46 days in the presence of retinyl acetate. In the absence of vitamin A the explant epithelium became quiescent or underwent a metaplastic change to a keratinizing squamous epithelium. This process was accelerated if explants were derived from vitamin A-deficient animals. Autoradiographic examination showed that [³H]glucosamine label accumulated in various cell types in the explant, but especially in the epithelium. It was found that the explants secreted mucous glycoproteins into the medium and that the production and biochemical characteristics of a specific mucin fraction were dependent upon the vitamin A status of the explant.