Effects of habitat fragmentation on Zostera marina seed distribution

Habitat fragmentation is a process which can alter the spatial configuration and reduce the overall area of a habitat. This generally results in a degradation of habitat functioning. Fragmentation of seagrass (Zostera marina) beds has become increasingly common, and it may threaten the valuable ecosystem services they provide. Sexual reproduction through flowering and seed dispersal could contribute to the species' potential resiliency by reducing its vulnerability to fragmentation. We investigated whether the proportion and density of flowering Z. marina shoots, and subsequently the density and distribution of seeds, differed between fragmented and continuous beds. Our results revealed that while flowering effort did not differ between the two bed types, seed density was significantly reduced in fragmented versus continuous beds. Further, seed distributions were altered in fragmented beds when compared to continuous beds, both within and directly outside the bed's boundaries. Seagrass patch size positively influenced seed density, with lower seed densities in small patches. Fragmented beds consistently contained fewer seeds per-unit-area than continuous beds, regardless of bed seagrass area and flowering effort. Collectively, these results emphasize the vulnerability of Z. marina to habitat fragmentation by demonstrating a negative effect on seed density and an impact on seed distribution, which likely reduces the potential advantages of sexual reproduction for bed growth and resiliency to perturbations

Prevalence of the alternative lengthening of telomeres telomere maintenance mechanism in human cancer subtypes

Approximately 10% to 15% of human cancers lack detectable telomerase activity, and a subset of these maintain telomere lengths by the telomerase-independent telomere maintenance mechanism termed alternative lengthening of telomeres (ALT). The ALT phenotype, relatively common in subtypes of sarcomas and astrocytomas, has rarely been reported in epithelial malignancies. However, the prevalence of ALT has not been thoroughly assessed across all cancer types. We therefore comprehensively surveyed the ALT phenotype in a broad range of human cancers. In total, two independent sets comprising 6110 primary tumors from 94 different cancer subtypes, 541 benign neoplasms, and 264 normal tissue samples were assessed by combined telomere-specific fluorescence in situ hybridization and immunofluorescence labeling for PML protein. Overall, ALT was observed in 3.73% (228/6110) of all tumor specimens, but was not observed in benign neoplasms or normal tissues. This is the first report of ALT in carcinomas arising from the bladder, cervix, endometrium, esophagus, gallbladder, kidney, liver, and lung. Additionally, this is the first report of ALT in medulloblastomas, oligodendrogliomas, meningiomas, schwannomas, and pediatric glioblastoma multiformes. Previous studies have shown associations between ALT status and prognosis in some tumor types; thus, further studies are warranted to assess the potential prognostic significance and unique biology of ALT-positive tumors. These findings may have therapeutic consequences, because ALT-positive cancers are predicted to be resistant to anti-telomerase therapies