941 resultados para Bufo marinus Queensland Geographical distribution


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Issued by the Society under an earlier name: Geographical Society of Australasia.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Issued also as House doc. 416, 61st Cong., 2d sess.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Photocopy of: 1977 ed. Princeton, N.J. : Mathtech.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Inferring the spatial expansion dynamics of invading species from molecular data is notoriously difficult due to the complexity of the processes involved. For these demographic scenarios, genetic data obtained from highly variable markers may be profitably combined with specific sampling schemes and information from other sources using a Bayesian approach. The geographic range of the introduced toad Bufo marinus is still expanding in eastern and northern Australia, in each case from isolates established around 1960. A large amount of demographic and historical information is available on both expansion areas. In each area, samples were collected along a transect representing populations of different ages and genotyped at 10 microsatellite loci. Five demographic models of expansion, differing in the dispersal pattern for migrants and founders and in the number of founders, were considered. Because the demographic history is complex, we used an approximate Bayesian method, based on a rejection-regression algorithm. to formally test the relative likelihoods of the five models of expansion and to infer demographic parameters. A stepwise migration-foundation model with founder events was statistically better supported than other four models in both expansion areas. Posterior distributions supported different dynamics of expansion in the studied areas. Populations in the eastern expansion area have a lower stable effective population size and have been founded by a smaller number of individuals than those in the northern expansion area. Once demographically stabilized, populations exchange a substantial number of effective migrants per generation in both expansion areas, and such exchanges are larger in northern than in eastern Australia. The effective number of migrants appears to be considerably lower than that of founders in both expansion areas. We found our inferences to be relatively robust to various assumptions on marker. demographic, and historical features. The method presented here is the only robust, model-based method available so far, which allows inferring complex population dynamics over a short time scale. It also provides the basis for investigating the interplay between population dynamics, drift, and selection in invasive species.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The cane toad (Bufo marinus) was used as a model to study male anuran reproductive endocrinology and to develop a protocol for non-invasive sperm recovery. Circulating testosterone concentrations in 6-hourly samples did not vary significantly (P < 0.05) over a 24 h period although there was a tendency (P = 0.06) for testosterone to be elevated at 19:00 h relative to other times of the day, which may be related to the nocturnal activity pattern of this species. Testosterone secretion after intraperitoneal (IP) injection of either a GnRH agonist (5 mu g IP) or hCG (1000 IU) was also examined. While the GnRH agonist did not produce a significant increase above basal plasma testosterone (0.29, 95% C.I. of 0.05-1.10 ng/ml), injection of hCG resulted in an increase (P < 0.01) of plasma testosterone with peak concentrations at approximately 120 min (4.17, 95% C.I. of 2.69-7.44 ng/ml) after injection. Non-invasive pharmaceutical sperm recovery was attempted following IP injection of graded doses of GnRH agonist, hCG or FSH. Urine was collected at 3, 6 and 12 h after treatment to assess sperm quality and quantity. The optimal protocol for sperm recovery in cane toads was injection of either 1000 or 2000 IU hCG; there was no significant difference in the quality of the spermic urine samples obtained using either dose of hCG or with respect to collection time. The findings indicated that hCG can be used to assess testicular steroidogenic status and also to induce sperm recovery in the cane toad. The hCG protocols developed in this study will have application in studies on the reproductive biology of rare and endangered male anurans. (c) 2005 Elsevier B.V. All rights reserved.