A new analytical model for whole-leaf potential electron transport rate

A new analytical model for the response of whole‐leaf potential electron transport rate (J) to light is presented. The model treats incident irradiance at the upper and lower leaf surfaces independently, describes transdermal profiles of light absorption and electron transport capacity explicitly, and calculates J by integrating the minimum of light‐ and capacity‐limited rates among paradermal chlorophyll layers. The capacity profile is assumed to be a weighted average of two opposed exponential profiles, each of which corresponds to the profile of light‐limited rate when only one surface is illuminated; the weights may take on any values, provided they sum to unity, so the model can describe leaves with a wide range of ‘preferred’ illumination regimes. By treating irradiance at either surface independently and assuming the capacity profile is fixed on short time scales, the model predicts observed effects of leaf inversion on light‐response curves and their apparent convexity. By assuming the capacity profile can adapt on developmental time scales, the model can predict the observed dependence of inversion effects on the growth lighting regime. It is suggested that the new model, which is mathematically compact and formally similar to the standard non‐rectangular hyperbola model for J, be used in place of the standard model in studies in which the effects of leaf angle or diffuse light fraction on gas exchange are of interest.     

Partitioning changes in photosynthetic rate into contributions from different variables

Changes in net CO₂ assimilation rate (A) are often partitioned into contributions from changes in different variables using an approach that is based on an expression from calculus: namely the definition of the exact differential of A, which states that an infinitesimal change in A (dA) is equal to the sum of infinitesimal changes in each of the underlying variables, each multiplied by the partial derivative of A with respect to the variable. Finite changes in A can thus be partitioned by integrating this sum across a finite interval. The most widely used method of estimating that integral is a coarse discrete approximation that uses partial derivatives of the natural logarithm of A rather than A itself. This yields biased and ambiguous estimates of partitioned changes in A. We present an alternative partitioning approach based on direct numerical integration of dA. The new approach does not require any partial derivatives to be computed, and it can be applied under any conditions to estimate the contributions from changes in any photosynthetic variable. We demonstrate this approach using field measurements of both seasonal and diurnal changes in assimilation rate, and we provide a spreadsheet implementing the new approach.     

Patterns in north Queensland mangrove vegetation

This note suggests an additional interpretation of analyses of north Queensland tidal forest vegetation recently presented by Bunt & Williams (1980a). They separated 30 species associations defined by various combinations of 11 defining species, and showed that these associations do not form a single invariant zonal sequence, as implied previously by Macnae (1966). Their results do indicate, however, that individual mangrove species are characteristically associated with different sections of the overall tidal range. This does not contradict their conclusions but rather places a different emphasis on their results.     

Transplants along the vegetation gradient on central Australian sandridges

To assess the importance of static catenary factors in controlling the floristic gradient on central Australian sandridges, plant species characteristic of particular topographic zones were transplanted to zones outside their normal topographic range. Both upper-slope species transplanted downslope, and lower-slope species transplanted upslope suffered higher mortality than control plants transplanted within the same topographic zone.     

Evidence against primary microclimatic control of the dune-swale floristic gradient on central Australian sandridges

There are distinct and consistent soil and vegetation gradients between the dune-crests and swales of the central Australian sandridges. If there is a corresponding dune-swale microclimatic gradient, it is assumed to be controlled by topography. In general, soil characteristics and topography are closely correlated, but where they diverge, vegetation follows soil rather than topography. Hence if any duneswale microclimatic gradient exists, it is not a significant factor in controlling the dune-swale floristic gradient.     

Soils and vegetation of central Australian sandridges II. Sandridge vegetation in the Uluru National Park Area,Northern Territory,Australia

Belt transects taken over the main sandridges in Uluru National Park, Northern Territory, show a consistent fioristic zonation from swale to dunecrest. On the larger ridges five or six zones are distinguishable and the crest assemblage is largely disjunct; on the lower dunes the pattern is truncated. The Uluru dunefields are representative of the Northern Territory and central Western Australia, though the floristic assemblage differs regionally.     

Phylogeography and ecological niche modelling implicate coastal refugia and trans‐alpine dispersal of a New Zealand fungus beetle

The Last Glacial Maximum (LGM) severely restricted forest ecosystems on New Zealand’s South Island, but the extent of LGM distribution for forest species is still poorly understood. We used mitochondrial DNA phylogeography (COI) and ecological niche modelling (ENM) to identify LGM refugia for the mycophagous beetle Agyrtodes labralis (Leiodidae), a forest edge species widely distributed in the South Island. Both the phylogenetic analyses and the ENM indicate that A. labralis refuged in Kaikoura, Nelson, and along much of the South Island’s west coast. Phylogeography of this species indicates that recolonization of the largely deforested east and southeast South Island occurred in a west–east direction, with populations moving through the Southern Alps, and that the northern refugia participated little in interglacial population expansion. This contradicts published studies of other New Zealand species, in which recolonization occurs in a north–south fashion from many of the same refugia.     

A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard (Anolis carolinensis) populations

We measured available and actual habitat use, morphology, escape behaviour and clinging ability in a large sample ( N  = 242) of green anoles, Anolis carolinensis , in a habitat consisting primarily of segregated dense clumps of broad leaves, Aspidistra elatior (Tulane University campus, LA) to compare against similar data collected previously from a more typical habitat c. 30 km away, consisting of continuous strands of bushes and trees (Good Hope Field, St. Charles Parish, LA). At Tulane the anoles perched primarily on the broad, smooth leaves of broad leaves, whereas in Good Hope Field (GHF) they predominantly perched on branches and tree trunks. The two populations differed significantly in morphology. In Tulane, the anoles tended to have shorter distal hindlimb elements, longer forelimb elements, and were more 'slender' than those at GHF. A comparison of escape behaviour showed population and sex differences. In both populations, females had significantly longer approach distances (i.e. were more 'wary') than males. These distances were, in addition, significantly longer at GHF than at Tulane for both sexes; this may be due to the potentially higher diversity and abundance of predators at GHF, although habituation to humans may also play a role. Anoles at Tulane had significantly larger toepads and higher clinging abilities than those at GHF. The enhanced clinging abilities of anoles at Tulane may have arisen due to their propensity to use smooth leaves as their primary substrate. Overall, our data reveal substantial ecological, behavioural, morphological, and functional differences among populations, some of which may be adaptive.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 223–234.