Dependence of bryophyte species on young, mature and old growth wet eucalypt forest

Maintenance of old growth forest has been argued to be important for the future of many bryophyte species, but there has been no empirical test of this proposition. Bryophytes constitute much of the plant biodiversity in Tasmanian tall open-forests dominated by Eucalyptus regnans and Eucalyptus obliqua. These forests have a low level of protection in their old growth stage. We ask whether if there is a concentration of bryophyte species in particular forest age classes and assess its significance for biological conservation. The bryophyte species at 99 forest sites were recorded and related to young, mature and old growth age classes using ANOVA. Only two bryophyte taxa were confined, with statistical confidence, to one of these classes. Succession in bryophyte assemblages takes the relay floristics form, with a few highly frequent species in the young forest, most of which do not persist in later stages, a large number of species establishing in middle-aged forests, some dying out with their short-lived hosts by the time of the old growth forest stage, and liverworts becoming more prominent with age. Species concentrated in the old growth phase of these eucalypt forests have all been recorded from secure reserves in this and other vegetation types. If present patterns of land use continue, and no extensive wild fires occur in the reserved old growth forest, almost all bryophyte species of E. regnans and E. obliqua mixed forest are likely to survive. This may not be the case in other regions of the world, where reservation may be poorer than in Tasmania.     

Does the response of bird assemblages to fire mosaic properties vary among spatial scales and foraging guilds?

Context

An increasing number of studies have investigated the impact of environmental heterogeneity on faunal assemblages when measured at multiple spatial scales. Few studies, however, have considered how the effects of heterogeneity on fauna vary with the spatial scale at which the response variable is characterised.

Objectives

We investigated the relationship between landscape properties in a region characterised by diverse fire mosaics, and the structure and composition of avian assemblages measured at both the site- (1 ha) and landscape-scale (100 ha).

Methods

We surveyed birds and calculated spatial landscape properties in sub-tropical woodlands of central Queensland, Australia.

Results

Environmental heterogeneity, as measured by topographic complexity, was consistently important for bird species richness and composition. However, the explanatory power of topographic complexity varied depending on the spatial scale and the component of diversity under investigation. We found different correlates of richness within particular foraging guilds depending on the scale at which richness was measured. Extent of long-unburnt habitat (>10 years since fire) was the most important variable for the landscape-scale richness of frugivores, insectivores and canopy feeders, whereas environmental heterogeneity in the surrounding landscape was more important for site-scale richness of these foraging guilds.

Conclusions

The response of species richness to landscape characteristics varies among scales, and among components of diversity. Thus, depending on the scale at which a biodiversity conservation goal is conceptualised—maximising richness at a site, or across a landscape—different landscape management approaches may be preferred.

     

Report from the conference, ‘identifying obstacles to applying big data in agriculture’

Precision Agriculture - Data-centric technology has not undergone widespread adoption in production agriculture but could address global needs for food security and farm profitability. Participants...     

Unique clones of the pitch canker fungus, <Emphasis Type="Italic">Fusarium circinatum,</Emphasis> associated with a new disease outbreak in South Africa

Pitch canker of pines is caused by the fungus Fusarium circinatum. In South Africa, this pathogen has mostly been a nursery problem. From 2005, however, outbreaks of pitch canker have been reported from established Pinus radiata and P. greggii in the Western and Eastern Cape Provinces. Most recently, pitch canker-like symptoms were observed on 10-year-old P. greggii trees in a plantation in the midlands of the KwaZulu-Natal (KZN) Province. The aim of this study was to: (i) identify the causal agent of the observed symptoms, (ii) determine the genetic diversity, and (iii) the mode of reproduction of this fungal population. Furthermore, the aggressiveness of isolates from these trees was compared with that of isolates obtained previously from P. patula in South Africa. Isolates from the P. greggii trees in KZN were confirmed as F. circinatum based on both morphology and DNA sequence analyses. Microsatellite marker analyses revealed the presence of five genotypes of F. circinatum, not previously reported from other plantations in South Africa, with one of these genotypes being dominant. These genotypes were all pathogenic to P. patula and P. elliottii. No evidence of sexual reproduction was detected in the KZN population of the fungus. This was consistent with the fact that isolates from P. greggii were all of the MAT-2 mating type, in contrast to previously collected isolates from across South Africa that included both mating types. The results suggest that the outbreak of pitch canker on P. greggii in KZN represents a separate introduction of F. circinatum into the region with important implications for managing the disease.     

Radiographic anatomy and barium sulfate contrast study of the gastrointestinal tract of eastern box turtles (Terrapene carolina carolina)

Gastrointestinal disorders are an important cause of morbidity in box turtles (Terrapene carolina Carolina), however published information is currently lacking on the normal radiographic anatomy, transit, and emptying times of the gastrointestinal tract. A total of 15 healthy box turtles were recruited for this prospective, anatomic, reference interval study. Three‐view radiographic series (vertical beam dorsoventral, horizontal beam latero‐lateral, and horizontal beam rostrocaudal views) were acquired prior to contrast administration, and following contrast administration at 0, 20, 40, 60, and 90 min, 2, 4, 8, 12, and 24 h post administration, and every 24 h thereafter until all contrast was eliminated (15 mL/kg barium sulfate diluted to 30% weight per volume was administered via orogastric gavage). Vertical beam dorsoventral and horizontal beam latero‐lateral views were of excellent quality to identify gastrointestinal structures. The horizontal beam rostrocaudal view immediately postcontrast administration provided gastric and pyloric identification but had lesser diagnostic use at later time points due to anatomical superimposition. The gastrointestinal tract was composed of a tubular stomach, a pyloric sphincter near midline, a duodenum with a cranial flexure in the right cranial coelomic cavity, small intestines within the right coelom, a small cecal bulb, and a transverse and descending colon. Contrast media entered the large intestine by 24 h in all turtles, and a pyloro‐colic indentation was noted at the proximal descending colon. The large intestinal emptying was highly variable due to the interindividual variability of contrast sequestration within the cecal bulb. Findings from the current study serve as a reference on the gastrointestinal anatomy, transit, and emptying times in healthy eastern box turtles; and introduce a novel, horizontal beam, rostrocaudal view for gastrointestinal contrast studies in chelonians.     

A Survey of Infectious Diseases and Parasites of Penaeid Shrimp from the Gulf of Mexico

A histopathological survey of wild and cultured shrimp from the Gulf of Mexico was carried out to determine the prevalence and severity of infectious diseases and parasites, affecting four species of penaeid shrimp (Litopenaeus setiferus, Farfantepenaeus aztecus, F. duorarum, and L. vannamei). Around 60 shrimp were obtained from each of 10 sampling stations during different months in 1999 and 2000. One station was a shrimp culture farm from Tamaulipas State, and nine were wild stations from Tamaulipas (five), Veracruz (one), and Campeche (three) States. Thirty shrimp from each station were used for histological analysis. The remaining shrimp were frozen and kept at ?20 C to carry out PCR techniques to determine the presence of white spot syndrome virus (WSSV). Some in situ hybridization analyses were applied to ascertain cases of WSS viral disease. Fresh analysis was carried out in shrimp from only one station for parasite identification. The histopathological survey performed on 688 shrimp showed no evidence of viral diseases. Two shrimp from one station were histologically diagnosed as having presumptive WSSV. Tissues from the same shrimp were processed for in situ hybridization and another 20 samples from the same station were processed to run PCR techniques. In each case, the results were negative. The same PCR procedure was applied to the rest of the frozen samples and none of them showed the presence of the WSSV. No important bacterial infections were observed in any of the wild or cultured shrimp analyzed. Fresh analysis demonstrated the presence of the cestode Prochristianella hispida and the gregarines Cephalolobus penaeus and Nematopsis penaeus. Histological analysis showed that the abundance of P. hispida varied from 7 to 90%, and G1 to G4 grades of severity were observed, with G1 being the most common. Gregarines were commonly observed in the histological slides, with a prevalence varying from 3 to 56% and G1 severity in most cases. Haplosporidan infection was observed in one sample of F. duorarum, which is the first report of this parasite in this host. Two invasive epibionts, the filamentous bacteria Leucothrix sp. and the ciliate Ascophrys sp., were found in four sampled stations. The study showed that in ten stations sampled from 1999 to 2000 in the Gulf of Mexico, shrimp populations had no serious infectious diseases.     

A XERORADIOGRAPHIC STUDY OF OSTEOCHONDROSIS IN THE METACARPOPHALANGEAL REGION OF TWO FOALS

Using xeroradiographic techniques, both metacarpophalangeal regions of six quarter horse foals were radiographed at 1 day of age and at 2-week intervals until they were 6 weeks old, and then at 4-week intervals until they were 12 months old. Lateromedial and dorsopalmar xeroradiographs of each metacarpophalangeal region were made per examination; dorsomedial-palmarolateral projections of the left metacarpophalangeal joint of foal 6 were also made. The foals were weighed and measured at the withers immediately prior to each examination. Representative xeroradiographs were selected to demonstrate progression of the osteochondrosis (OCH) lesions in two of these foals. Radiographic evidence of osteochondrosis in the metacarpophalangeal region was first detected at 10 weeks and followed through 12 months of age. In one foal the lesions were bilaterally symmetric and involved the dorsoproximal aspect of the sagittal ridge of metacarpal 3; in the other, the left medial proximal sesamoid bone was affected. One of the sagittal ridge lesions progressed to osteochondritis dissecans by 26 weeks; the other sagittal ridge lesion and that of the sesamoid bone healed spontaneously, but residual radiographic evidence of the disease persisted throughout the study in both foals.