The Time Local Convex Hull method as a tool for assessing responses of fauna to habitat restoration: a case study using the perentie (Varanus giganteus : Reptilia : Varanidae)

Understanding the behavioural responses of animals to habitat change is vital to their conservation in landscapes undergoing restoration. Studies of animal responses to habitat restoration typically assess species presence/absence; however, such studies may be restricted in their ability to show whether restoration is facilitating the return of self-sustaining and functional fauna populations. We present a case study using VHF/GPS tracking of a young adult perentie (Varanus giganteus), to demonstrate the range of applications of the Time Local Convex Hull method of home-range construction in analysing the behavioural responses of fauna to habitat change and restoration. Presence/absence studies provide single point locations of an animal, and the Minimum Convex Polygon method provides an invariant estimate of habitat use across the whole home range. However, the Time Local Convex Hull method provides a useful method for assessing movement and behavioural responses of fauna to habitat change and restoration, and the specific habitat requirements for the long-term support of populations. The breadth and multidimensionality of data generated indicates strongly that understanding the complex interactions between animals and their environment is fundamental to their conservation in the face of ever-increasing rates of human-induced habitat change and degradation.

The history of South American tropical precipitation for the past 25,000 years

Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.

Delineation of an enhancerlike positive regulatory element in the interleukin-2 receptor alpha-chain gene

We have delineated a positive regulatory element in the interleukin-2 receptor alpha-chain gene (IL-2R alpha) between positions -299 and -243 that can potently activate a heterologous (herpesvirus thymidine kinase [tk]) promoter in phorbol myristate acetate (PMA)-induced Jurkat T cells and is functional when cloned in either orientation. This enhancerlike element contains a site (-268/-257) that can bind NF-kappa B; however, unlike the immunoglobulin kappa gene kappa B enhancer element, the IL-2R alpha kappa B-like site alone can only weakly activate a heterologous promoter. Adjacent 5' and 3' sequences also weakly activate the tk-CAT vector, but constructs combining the IL-2R alpha kappa B-like site plus adjacent 5' and 3' sequences potently activate gene expression. This combination of regions is essential for potent PMA-induced transcription from the tk promoter. Experiments using constructs in which IL-2R alpha upstream sequences are sequentially deleted suggested that there is a region 5' of position -299 which can suppress IL-2R alpha promoter and/or enhancer activity. Thus, it is possible that both positive and negative elements may be important in the regulation of IL-2R alpha gene transcription.

Functionally distinct NF-kappa B binding sites in the immunoglobulin kappa and IL-2 receptor alpha chain genes

The interleukin-2 receptor alpha (IL-2R alpha) chain gene contains a sequence similar to the immunoglobulin (Ig) kappa (kappa) enhancer NF-kappa B binding site. This site, which is bound by the nuclear protein, NF-kappa B, is critical for Ig kappa gene expression. The major T cell nuclear factor that binds to the IL-2R alpha site in vitro appears indistinguishable from NF-kappa B. NF-kappa B binds to IL-2R alpha and kappa sequences with similar affinities; however, only the kappa site potently activates transcription from heterologous promoters. Thus, high-affinity NF-kappa B binding in vitro cannot be equated with transcriptional activation in vivo. Mutation of the NF-kappa B binding site in the context of an IL-2 R alpha promoter construct markedly diminished promoter activity in human T cell lymphotropic virus type I (HTLV-I)-transformed MT-2 cells but not in phorbol myristate acetate-stimulated Jurkat T cells.

Comparison of the structure and cell cycle expression of mRNAs encoded by two histone H3-H4 loci in Saccharomyces cerevisiae

The haploid genome of Saccharomyces cerevisiae contains two nonallelic sets of histone H3 and H4 gene pairs, termed the copy I and copy II loci. The structures of the mRNA transcripts from each of these four genes were examined by nuclease protection and primer extension mapping. For each gene, several species of mRNAs were identified that differed in the lengths of their 5' and 3' untranslated regions. The cell cycle accumulation pattern of the H3 and H4 mRNAs was determined in cells from early-exponential-growth cultures fractionated by centrifugal elutriation. The RNA transcripts from all four genes were regulated with the cell division cycle, and transcripts from the nonallelic gene copies showed tight temporal coordination. Cell cycle regulation did not depend on selection of a particular histone mRNA transcript since the ratio of the multiple species from each gene remained the same across the division cycle. Quantitative measurements showed significant differences in the amounts of mRNA expressed from the two nonallelic gene sets. The mRNAs from the copy II H3 and H4 genes were five to seven times more abundant than the mRNAs from the copy I genes. There was no dosage compensation in the steady-state levels of mRNA when either set of genes was deleted. In particular, there was no increase in the amount of copy I H3 or H4 transcripts in cells in which the high-abundance copy II genes were deleted.

Regulation of the human interleukin-2 receptor alpha chain promoter: activation of a nonfunctional promoter by the transactivator gene of HTLV-I

We have characterized regulatory regions of the human IL-2 receptor alpha chain (IL2R alpha) promoter. 5' deletion constructs extending to -327 directed CAT expression in HTLV-I-infected T cells, which express IL2R alpha constitutively, and in Jurkat cells, which express IL2R alpha only after induction. Deletions to -267 and -265 were active only in HTLV-I-transformed T cells, but their activity in Jurkat cells was restored by cotransfection of a construct expressing the HTLV-I transactivator protein (tat-I). However, HTLV-I-infected human osteosarcoma cells do not express IL2R alpha-CAT constructs. Thus cell-type-specific factors are required for IL2R alpha expression, and direct or indirect interaction(s) between tat-I and a specific region of the IL2R alpha promoter may cause altered regulation. Tat-I also augments IL2-CAT expression under some conditions, suggesting possible autocrine or paracrine mechanisms for HTLV-I-induced leukemogenesis.