Floristic notes from Crete

TURLAND, N. J., 1992. Floristic notes from Crete. Phytogeographical and ecological notes are given for 24 taxa of vascular plants occurring on the south Aegean island of Crete. These cover infrequent, localized and endemic species and include five new records: Daphne gnidioides, D.jasminea, Fraxinus ornus, Hemarthria altissima and Teline monspessulana. The occurrence of Orobanche lavandulacea and Ranunculus velutinus is confirmed. A second site is reported for the extremely rare endemic Convolvulus argyrothamnos and additional sites for a number of other localized endemics are provided.     

Independent colonization and extensive cryptic speciation of freshwater amphipods in the isolated groundwater springs of Australia's Great Artesian Basin

The groundwater-dependent springs of the Great Artesian Basin (GAB) in arid inland Australia represent a unique and threatened ecosystem. These incredibly isolated springs support a diverse array of endemic flora and fauna. One of the common faunal groups in the GAB springs is the freshwater amphipods of the family Chiltoniidae. The morphological conservatism and taxonomic uncertainty associated with these amphipods has ensured their true biodiversity, phylogeographical history and evolutionary affinities have remained unknown. We have used mitochondrial DNA and allozyme data to unravel a complicated history of isolation, extinction and dispersal among spring amphipod populations across the GAB. The results provide evidence for multiple independent colonizations in the GAB springs, particularly within the Lake Eyre group of springs. The inclusion of a group of Western Australian (WA) stygobitic amphipods from populations up to 1500 km away found surprising evidence for a shared evolutionary history between stygobitic and GAB spring amphipods. Approximate dating of the diversity found between major clades suggests the majority of lineages originated in the late Miocene, around the time of the aridification of inland Australia. The large number of independent lineages and the close connection between GAB spring and WA stygobitic amphipods suggest that a significantly rich amphipod fauna existed in the much wetter environment that once existed in inland Australia. The results also provide evidence for a gross underestimation of the species diversity within the springs, with 12 putative species identified, a conclusion with significant implications for the ongoing conservation of the GAB springs.     

Provision of nestboxes raises the breeding density of Great Tits Parus major equally in coniferous and deciduous woodland

Nestbox provision is a technique used to increase nest-site availability for secondary cavity-nesting birds. However, little is known about the demographic consequences of nestbox provision in different habitat types. To assess how nestbox provision affects the density of hole-nesting birds simultaneously in two contrasting habitats, we compared the breeding density of Great Tits along transects without nestboxes with that in transects where nestboxes were provided. Although the initial density of breeders was considerably higher in the deciduous habitat than in the coniferous habitat, provision of nestboxes increased density by a similar number of additional pairs in each habitat type. Thus, the provision of nestboxes in managed coniferous forests may be as effective in increasing the breeding opportunities of cavity nesters as in deciduous stands. Moreover, previous research showed that pairs in deciduous habitat with nestboxes have consistently lower breeding success than those in coniferous habitat with nestboxes. It is possible that the addition of nestboxes in the preferred habitat increased density to such an extent that density-dependent effects became apparent.     

Co-expression tools for plant biology: opportunities for hypothesis generation and caveats

Gene co‐expression analysis has emerged in the past 5 years as a powerful tool for gene function prediction. In essence, co‐expression analysis asks the question ‘what are the genes that are co‐expressed, that is, those that show similar expression profiles across many experiments, with my gene of interest?’. Genes that are highly co‐expressed may be involved in the biological process or processes of the query gene. This review describes the tools that are available for performing such analyses, how each of these perform, and also discusses statistical issues including how normalization of gene expression data can influence co‐expression results, calculation of co‐expression scores and P values, and the influence of data sets used for co‐expression analysis. Finally, examples from the literature will be presented, wherein co‐expression has been used to corroborate and discover various aspects of plant biology.     

Impact of insect defoliation on forest carbon balance as assessed with a canopy assimilation model

Disturbances such as fire, hurricanes, and herbivory often result in the net release of CO₂ from forests to the atmosphere, but the magnitude of carbon (C) loss is poorly quantified and difficult to predict. Here, we investigate the carbon balance of an oak/pine forest in the New Jersey Pine Barrens using the Canopy Conductance Constrained Carbon Assimilation (4C‐A) model. The 4C‐A model utilizes whole‐tree sap‐flux and leaf‐level photosynthetic gas exchange measurements at distinct canopy levels to estimate canopy assimilation. After model parameterization, sensitivity analyses, and evaluation against eddy flux measurements made in 2006, the model was used to predict C assimilation for an undisturbed year in 2005, and in 2007 when the stand was completely defoliated for 2–3 weeks during an infestation of gypsy moths (Lymantria dispar L.). Following defoliation, only 50% of the foliage reemerged in a second flush. In 2007, canopy net assimilation (A_nC), as modeled with the 4C‐A, was reduced to approximately 75% of A_nC in 2006 (940 vs. 1240 g C m^?2 a^?1). Overall, net primary production (NPP) in 2007 was approximately 240 g C m^?2 a^?1 (vs. 250 g C m^?2 a^?1 in 2006), with 60% of NPP allocated to foliage production, a short‐term carbon pool. Woody biomass accumulation, a long‐term carbon pool, was reduced by 20% compared with the previous year (72 vs. 57 g C m^?2 a^?1 in 2006 and 2007, respectively). The overall impact of the defoliation spanned 21% of upland forests (320 km²) in the New Jersey Pine Barrens, representing a significant amount of overall C not being taken up from the atmosphere by the forest, thus not accumulated in the biosphere.     

Evidence of drought-induced stress on biotic crust moss in the Mojave Desert

Widespread bleaching (chlorosis) of patches of the dominant desert moss Syntrichia caninervis was observed across the northern Mojave Desert in the winter of 2002–03 following an extended period of drought interrupted by small rain events. These rain events were more frequent during the warmer months just prior to the appearance of chlorosis. We hypothesized that the patches were experiencing physiological stress due to partial hydration/rapid dehydration cycling during the warmer months. Compared to unbleached (green) shoots, chlorotic shoots exhibited significantly reduced photochemical performance, photosynthetic pigments, regenerational potential, sex expression, and lower rates of growth and productivity. However, age-specific analyses revealed older leaves from chlorotic shoots did not show the typical decline in vigour, suggesting that stress may primarily affect younger tissues. It is concluded that this chlorosis phenomenon is indicative of physiological stress presently occurring in the Mojave Desert, and is likely due to exposure to a higher than normal frequency of light rain events (< 3.5 mm), which serve to partially hydrate moss patches that then rapidly desiccate .