EFFECTIVE POPULATION SIZE AND GENETIC DRIFT IN TRISTYLOUS EICHHORNIA PANICULATA (PONTEDERIACEAE)

Populations of the tristylous, annual Eichhornia paniculata are markedly differentiated with respect to frequency of mating types. This variation is associated with evolutionary changes in mating system, from predominant outcrossing to high self-fertilization. To assess the potential influence of genetic drift acting on this variation, we estimated effective population size in 10 populations from northeastern Brazil using genetic and demographic methods. Effective size (N_e) was inferred from temporal changes in allele frequency at two to eight isozyme loci and also calculated using five demographic variables: 1) the number of flowering individuals (N); 2) temporal fluctuations in N; 3) variance in flower number; 4) frequency of mating types; and 5) selfing rate. Average N_e based on isozyme data was 15.8, range 3.4–70.6, and represented a fraction (mean N_e/N = 0.106) of the census number of individuals (mean N = 762.8; range: 30.5–5,040). Temporal variation in N and variance in flower number each reduced N_e to about a half of N whereas mating type frequencies and selfing rate caused only small reductions in N_e relative to N. All estimates of N_e based on demographic variables were considerably larger than those obtained from genetic data. The two kinds of estimates were in general agreement, however, when all demographic variables were combined into a single measure. Monte Carlo simulations indicated that effective size must be fewer than about 40 for drift to overcome the frequency-dependent selection that maintains the polymorphism for mating type. Applying the average N_e/N value to 167 populations censused in northeastern Brazil indicated that 72% had effective sizes below this number. This suggests that genetic drift is likely to play a dominant role in natural populations of E. paniculata.     

Elevated extracellular matrix production and degradation upon bone morphogenetic protein-2 (BMP-2) stimulation point toward a role for BMP-2 in cartilage repair and remodeling

Bone morphogenetic protein-2 (BMP-2) has been proposed as a tool for cartilage repair and as a stimulant of chondrogenesis. In healthy cartilage, BMP-2 is hardly present, whereas it is highly expressed during osteoarthritis. To assess its function in cartilage, BMP-2 was overexpressed in healthy murine knee joints and the effects on proteoglycan (PG) synthesis and degradation were evaluated. Moreover, the contribution of BMP in repairing damage induced by interleukin-1 (IL-1) was investigated. Ad-BMP-2 was injected intra-articularly into murine knee joints, which were isolated 3, 7, and 21 days after injection for histology, immunohistochemistry, and autoradiography. In addition, patellar and tibial cartilage was isolated for RNA isolation or measurement of PG synthesis by means of ³⁵SO₄ ^2- incorporation. To investigate the role for BMP-2 in cartilage repair, cartilage damage was induced by intra-articular injection of IL-1. After 2 days, Ad-BMP-2, Ad-BMP-2 + Ad-gremlin, Ad-gremlin, or a control virus was injected. Whole knee joints were isolated for histology at day 4 or patellae were isolated to measure ³⁵SO₄ ^2- incorporation. BMP-2 stimulated PG synthesis in patellar cartilage on all days and in tibial cartilage on day 21. Aggrecan mRNA expression had increased on all days in patellar cartilage, with the highest increase on day 7. Collagen type II expression showed a similar expression pattern. In tibial cartilage, collagen type II and aggrecan mRNA expression had increased on days 7 and 21. BMP-2 overexpression also induced increased aggrecan degradation in cartilage. VDIPEN staining (indicating matrix metalloproteinase activity) was elevated on day 3 in tibial cartilage and on days 3 and 7 in patellar cartilage, but no longer was by day 21. Increased NITEGE staining (indicating aggrecanase activity) was found on days 7 and 21. In IL-1-damaged patellar cartilage, BMP-2 boosted PG synthesis. Blocking of BMP activity resulted in a decreased PG synthesis compared with IL-1 alone. This decreased PG synthesis was associated with PG depletion in the cartilage. These data show that BMP-2 boosts matrix turnover in intact and IL-damaged cartilage. Moreover, BMP contributes to the intrinsic repair capacity of damaged cartilage. Increased matrix turnover might be functional in replacing matrix molecules in the repair of a damaged cartilage matrix.     

Interspecific seed discounting and the fertility cost of hybridization in an endangered species

Hybrid fertilizations can have negative demographic effects on taxa by usurping ovules that would otherwise give rise to nonhybrid offspring. The consequent reduction in conspecific matings may be exaggerated in rare taxa and constitutes a fertility cost that has rarely been quantified. Here, the effect of interspecific mating was estimated on the fecundity of locally rare red mulberry (Morus rubra), which hybridizes with introduced white mulberry (Morus alba) and red yen white hybrids. First, the asymmetry in pollen production among red, white and hybrid mulberry in two sympatric populations was quantified. The fertility cost of hybridization was then assessed experimentally by estimating seed production and rates of interspecific mating in red mulberry trees from plots where white and hybrid mulberry trees were selectively removed. On average, the percentage of mulberry pollen per plot produced by red mulberry (8%) was significantly lower than the mean for white and hybrid mulberry combined (92%). Experimentally removing white and hybrid mulberry increased the siring fertility of red mulberry by 14% but produced no change in seed set. Results indicate that seeds of red mulberry, ordinarily sired by conspecific pollen, are being discounted through fertilization of ovules by heterospecific pollen, which may contribute to local decline of red mulberry.     

Quantitative study on the inferior vena cava between the renal vein and diaphragm

50 dissections of the human inferior V. cava have been performed in order to measure its right renal vein - diaphragm, retrohepatic, and suprahepatic segments. We conclude that some individual parameters as skin type, age, height, weight did not influence the magnitude of the studied segments. The average measurements of the different parameters proposed for the inferior V. cava are: 1. The distances between the right renal vein and the diaphragm and between the right renal vein and the right atrium are 113.94 mm and 135.16 mm, respectively; 2. the length of the retrohepatic portion of the inferior V. cava and the suprahepatic one were 78.34 mm and 19.34 mm respectively; 3. the valve of the inferior V. cava is present in 46% of the observations; its length and width averages are 31 mm and 10.22 mm, respectively.     

Local texture convergence: a new approach to seeking assembly rules

Much of community-ecology theory describes (or even assumes) constraints on the coexistence of species. These constraints are often described using functional characters as an index to the niche of the species. The hypothesis/assumption is that those species which are too similar in functional characters, and hence in niche, cannot coexist. However, this body of theory is rarely tested. We attempted a test by making a prediction of texture convergence that follows logically from the theory, yet is simple enough to test – one based on similarity of ecological assembly between the patches of a community. We used replicate quadrats within twelve herbaceous communities. Eleven characters were measured, that were intended to reflect the functional above-ground niche of the species. We examined each character in turn, to test for ecological convergence to a similar mean within each community, with species either weighted equally (i.e. using species presence) or weighted by their biomass. Convergence with species weighted by their biomass was seen in chlorophyll content, indicating a significant tendency for each patch in a community to comprise a rather constant mixture of species types in terms of their different chlorophyll contents. In terms of species presence, texture divergence occurred in leafiness (LAR), specific leaf area (SLA) and leaf inclination, i.e. there was more variation between quadrats within a site than expected at random. However, significant results were sparse: the bulk of evidence is for no significant departure from a null model, i.e. no support for a widespread body of ecological theory.     

Genetic diversity in captive and wild Matschie's tree kangaroo (Dendrolagus matschiei) from Huon Peninsula,Papua New Guinea,based on mtDNA control region sequences

The Association of Zoos and Aquariums (AZA) Matschie's tree kangaroo (Dendrolagus matschiei) population is at a critical point for assessing long-term viability. This population, established from 19 genetically uncharacterized D. matschiei, has endured a founder effect because only four individuals contributed the majority of offspring. The highly variable mitochondrial DNA (mtDNA) control region was sequenced for five of the female-founders by examining extant representatives of their maternal lineage and compared with wild (n=13) and captive (n=18) D. matschiei from Papua New Guinea (PNG). AZA female-founder D. matschiei control region haplotype diversity was low, compared with captive D. matschiei held in PNG. AZA D. matschiei have only two control region haplotypes because four out of five AZA female-founder D. matschiei had an identical sequence. Both AZA haplotypes were identified among the 17 wild and captive D. matschiei haplotypes from PNG. Genomic DNA extracted from wild D. matschiei fecal samples was a reliable source of mtDNA that could be used for a larger scale study. We recommend a nuclear DNA genetic analysis to more fully characterize AZA D. matschiei genetic diversity and to assist their Species Survival Plan^®. An improved understanding of D. matschiei genetics will contribute substantially to the conservation of these unique animals both in captivity and the wild. Zoo Biol 28:183–196, 2009. © 2008 Wiley-Liss, Inc.     

Long distance dispersal in the assembly of floras: A review of progress and prospects in North America

Here, we review progress and prospects to explicitly test for long distance dispersal biogeographic events. Long distance dispersal represents a “jump” across some kind of barrier, such as a topographic feature or a zone of unsuitable climate and may include repeated jumps, or stepping‐stone dispersals. Long distance dispersals were considered integral for explaining the organization of biodiversity at large and small scales by early biogeographers, such as Darwin and Wallace. Darwin, Wallace, and others envisioned that long distance dispersals were predictable events because the vectors for dispersal, such as animals, winds, and currents, behaved in non‐random ways. However, these early biogeographers found that dispersal was hard to observe, and, later, with the advent of the theory of Continental Drift, vicariance became regarded as a better scientific explanation for the arrangement of biodiversity, because it represented a falsifiable hypothesis. Thus, long distance dispersal was reduced to a nuisance parameter in biogeography; a random possibility that could never fully be ruled out in a scenario in which evidence supported vicariance. Today, there is strong interest to more fully integrate long distance dispersal into understanding the assembly and organization of biodiversity on earth. In this review, we discuss progress and prospects for explicitly testing long distance dispersal hypotheses including through uses of molecular, morphological, paleontological, and informatics methods. We focus on hypothesis testing of long distance dispersals involved in the assembly of the flora of North America, which is a robust preliminary study system on account of its extant and extinct biodiversity being well‐catalogued.