Giant cuticular pores in Eidothea zoexylocarya (Proteaceae) leaves

Ubiquitous, large diameter pores have not previously been adequately demonstrated to occur in leaf cuticles. Here we show conclusively that such structures occur in Eidothea zoexylocarya, a rainforest tree species of Proteaceae restricted to the Australian Wet Tropics. The pores are abundant, large-diameter apertures (～1 μm), that extend perpendicularly most of the way through the cuticle from the inside. They occur on both sides of the leaf, but are absent from the cuticle associated with stomatal complexes on the abaxial side. No such pores were found in any other species, including the only other species of Eidothea, E. hardeniana from New South Wales, and other species that have previously been purported to possess cuticular pores. To determine whether these pores made the cuticles more leaky to water vapor, we measured astomatous cuticular conductances to water vapor for E. zoexylocarya and seven other Proteaceae species of the Wet Tropics. Cuticular conductance for E. zoexylocarya was relatively low, indicating that the prominent pores do not increase conductance. The function of the pores is currently obscure, but the presence of both pores and an adaxial hypodermis in E. zoexylocarya but not E. hardeniana suggests evolution in response to greater environmental stresses in the tropics.     

Meristic variation in Potamogeton flowers

Flowers of Potamogeton normally have a completely tetramerous plan. Deviations from this norm occur quite commonly in the uppermost flowers of the inflorescence; these variations have been reported before and usually involve a reduction in number of parts. Cases have now been found where the gynoecium of all or many flowers differs from the normal tetracarpellate arrangement; some species regularly have fewer and others more than four carpels. The developmental bases of meristic variation have been explored and quantitative studies of gynoecia and developing gynoecia have been undertaken. The data are used to evaluate the control and correlation of floral development in Potamogeton in general, and in particular the relationship between the gynoecium and the rest of the flower. The developing flower passes through two successive phases of organ initiation: one in which the perianth and stamen primordia arise, and one in which the gynoecial primordia arise. There seems to be little developmental relationship between the two phases except phyllotactic continuity. During the perianth/stamen phase each stamen primordium arises directly above a perianth member, and the presence of a perianth member seems to be a prerequisite for initiation of the stamen. The perianth/stamen phase seems to be rather stable so that normally four perianth/stamen associations are initiated, except in flowers at the tip of the inflorescence. In the gynoecial phase the number of carpel primordia initiated seems to depend on the relative size of carpel primordia and floral apex, and on whether or not the floral apex continues to grow while initiating carpel primordia.     

Biological variation between two Brazilian geographical isolates of Echinostoma paraensei

The biological behaviour and morphometric data from two allopatric isolates of Echinostoma paraensei (Rio Bonito - RB and Sumidouro - SU) collected from naturally infected Nectomys squamipes from two secluded Atlantic Forest fragments were studied. Mice that had been experimentally infected with ten encysted metacercariae of each isolate were monitored weekly in two trials to analyse worm burden and the kinetics of worm distribution along the intestine. The total number of uterine eggs, wet weights and measurements of the worms and body, acetabulum, testes and ovaries were also analysed. The RB isolate showed a higher worm burden, 7.7+/-0.8, and a longer life span, 16 weeks, compared to a worm burden of 5.8+/-1.1 and life span of 9 weeks for the SU isolate. Worms of the RB isolate were clustered in the duodenum and in the bile duct while the SU isolate worms were dispersed along the small intestine of infected mice. Both isolates developed similarly as regards morphometric data and wet weight, although the total number of uterine eggs was greater in RB. The degree of intraspecific variation observed in the worm distribution along the intestine, worm burden and life span raises questions regarding the use of these criteria for species differentiation. These findings suggest that variation in biological parameters found between the E. paraensei isolates could result from geographical isolation and, in particular, the environmental conditions of transmission. Further studies on E. paraensei polulations from different forest fragments will contribute towards an understanding of the speciation of this parasite.     

Qualitative geographical variation in interspecific interactions

We explore geographical variation in the density relationship between potential competitor forest bird groups, resident Parus spp. and migrant Fringilla spp., across Europe using published bird census results. In addition, we summarized results from three experimental studies from northern Europe on their density associations. Based on anticipated changes in the relative intensity of positive and competitive interactions we predicted a unimodal density association between Parus and Fringilla : at low and intermediate densities the two groups are positively associated (positive interaction), whereas high densities promote interspecific competition. In central Europe where densities are high, densities were unimodally related to each other. In northern and southern Europe linear and positive associations appeared. Experimental studies provided consistent support for positive interspecific interactions in the north. The results suggest that species interactions may indeed vary in relation to the density of potential competitor and switch from positive to negative along environmental gradients.     

Fluctuating asymmetry in leaves and flowers of sympatric species in a tropical montane environment

Fluctuating asymmetry (FA) represents small, random variations in traits, presumably with bilateral symmetry, and is widely used as a tool to measure developmental instability in plants and animals. Because FA is a quick, simple and reliable measure, it has been frequently used for monitoring levels of environmental stress. This study investigated whether FA can be used as a predictor of individual developmental instability for four sympatric Melastomataceae species. To achieve that aim, 20 individuals of Trembleya laniflora, T. parviflora, Lavoisiera campos‐portoana and Tibouchina heteromalla were marked in southeastern Brazil and monitored before and during the flowering season. The FA index was calculated as the mean of the difference in the width or length between the left and right sides measured for each leaf or flower. All studied species exhibited asymmetry in the leaves and flowers, but the leaves of L. campos‐portoana and the petal width of T. heteromalla exhibited directional asymmetry, also an indicator of developmental instability. The highest level of leaf asymmetry was found in T. heteromalla and on flowers of L. campos‐portoana. None of the studied species exhibited a significant relationship between the FA level of the leaves and flowers on an individual basis, indicating that environmental and/or genetic sources of stress might act differently on different plant traits. For the studied species, measurements of FA can be suggested as useful tools to biomonitor levels of stress experienced by both leaves and flowers within the Melastomataceae family.     

Coevolution between slave-making ants and their hosts: host specificity and geographical variation

We explored the impact of a slave-making ant, Protomognathus americanus, on two of its hosts, Leptothorax longispinosus and L. ambiguus. We showed that, on average, slave-maker colonies conduct raids on 2.7 L. longispinosus and 1.4 L. ambiguus nests in a single year. The more common host, L. longispinosus, survives raiding and colony-founding events in a third of the cases, but the less common host rarely survives attacks from the slave-makers. We compare our results, collected in Vermont, to a study conducted in New York where the slave-maker pressure is much stronger. Our results suggest that in Vermont the slave-maker has a sparing strategy when raiding L. longispinosus, but not when raiding L. ambiguus. Thus coevolution between slave-making ants and their hosts shows host specificity and geographical variation.     

Early-Middle Pleistocene leaves of extinct and extant Proteaceae from western Tasmania, Australia

Fossil leaves of six species of Proteaceae which are no longer native to Tasmania occur in Early Pleistocene sediments at Regatta Point, western Tasmania, Australia. These species probably became extinct during the Early or Middle Pleistocene as the direct or indirect result of glacial/interglacial cycles. Only one extinct species of Proteaceae is known from younger sediments. Leaves of another four species which can be confidently assigned to extant Tasmanian species, and from an extant genus also occur in these sediments. Another extant species occurs in Early Pleistocene sediments at the Huskisson/Marionoak Divide, western Tasmania, and another extant species occurs in Early-Middle Pleistocene sediments at Regatta Point. These fossils imply that the number of species and of genera of Proteaceae in western Tasmania has not increased since the Early Pleistocene, and may have declined. More species of Banksia and Telopea and at least as many species of Orites occurred in Early Pleistocene western Tasmania than now occur in that region. The presence of extant species in the Early Pleistocene suggests that the turnover time of many proteaceous species is of the order of millions of years. Two new species, Telopea strahanensis and Orites truncata , are proposed.     

Density-dependent and geographical variation in bird immune response

Latitudinal gradients in parasitism are common, causing differences in the intensity of parasite-mediated natural selection. Such differences in selection pressures should affect optimal investment in anti-parasite defense, because defense levels should increase in response to increased intensity of parasite-induced selection. Likewise, latitudinal differences in population density may affect immune responses either by selecting for higher levels or defense, or by suppressing resources needed for mounting efficient immune responses. We tested these predictions in a study of T-cell mediated immune response in altricial bird species in subtropical Spain and temperate Denmark. There were highly consistent levels of T-cell mediated response between nestlings and adults in the two areas, with nestlings having stronger responses than adults. In addition, there were highly consistent levels of immune response in nestlings and adults between the two areas, with responses being consistently stronger in Denmark than in Spain, particularly in adults. Population density was much higher in Denmark than in Spain. We found evidence of density-dependent immune response in nestlings and adults, as shown by differences in T-cell response between study areas being positively related to differences in density. Given that the relationship between density and immune response was positive, we can reject the hypothesis that higher population densities suppressed immune response. Therefore, our results support the hypothesis that birds in areas with higher density allocate more resources to immune response, particularly in adults, suggesting that density-dependent effects of parasitism have selected for allocation strategies that minimize the risk of parasitism.     

Structural and ultrastructural differences between field,micropropagated and acclimated leaves and stems of two Leucospermum cultivars (Proteaceae)

The anatomy of field, in vitro and acclimatized shoots (leaves and stems) of two cultivars of Leucospermum (L. cordifolium ‘Flame Spike’ and L. ‘Tango’) was compared using light, scanning and transmission electron microscopy. Field plants showed several scleromorphic anatomical structures related to excess solar radiation such as: cuticle thickness, subepidermal collenchyma and sclerenchyma. Furthermore, a large quantity of phenolic deposits present in the cell lumen of various tissues is also a scleromorphic feature. The special conditions during in vitro culture result in plantlets with abnormal morphology and anatomy. These disorders are associated with the gaseous environment in the culture vessels, low irradiance in the incubation chamber and the addition of sucrose, nutrients and growth regulators to the culture medium. After transfer from in vitro to ex vitro conditions, substantial changes in leaf and stem anatomy were observed, above all in cuticle thickness, epidermal characteristics (stomatal and trichome index, and stomatal and pore size), differentiation of leaf mesophyll, chloroplast structure, and amount and localization of phenolic deposits. These changes allowed the plants to adapt to the new environmental conditions. The study of anatomical features of in vitro shoots facilitated adapting the acclimation protocol to predict which plantlet would survive the critical acclimation stage.

     

Genetic variation in Banksia saxicola (Proteaceae), a rare Australian plant with a markedly disjunct distribution

 Banksia saxicola A.S. George (Proteaceae) is a rare Australian endemic, found in only two locations in Victoria that are separated by approximately 500 kms: the Grampians and Wilson's Promontory National Parks. The organisation of genetic variation between and within populations at the two locations was assessed using the Amplified Fragment Length Polymorphism (AFLP) technique. Two populations were sampled in the Grampians National Park and one population was sampled at Wilson's Promontory. The three populations were genetically divergent from each other, in particular the Grampians and Wilson's Promontory populations, and this relates to the ancient geographic isolation of these two regions. The Wilson's Promontory population had lower genetic diversity than either Grampians populations, consistent with its smaller population size. The findings are important for strategies to conserve B. saxicola. Received October 3, 2000 Accepted January 3, 2001     

Associations between physical isolation and geographical variation within three species of Neotropical birds

We studied effects of physical isolation on geographical variation in mtDNA RFLP polymorphisms and a suite of morphological characters within three species of neotropical forest birds; the crimson-backed tanager Ramphocelus dimidiatus, the blue-gray tanager Thraupis episcopus, and the streaked saltator Saltator albicollis. Variation among populations within continuous habitat on the Isthmus of Panama was compared with that among island populations isolated for about 10000 years. Putative barriers to dispersal were influential, but apparent isolation effects varied by species, geographical scale, and whether molecular or morphological traits were being assessed. We found no geographical structuring among the contiguous, mainland sampling sites. Migration rates among the islands appeared sufficient to maintain homogeneity in mtDNA haplotype frequencies. In contrast, variation in external morphology among islands was significant within two of three species. For all species, we found significant variation in genetic and morphological traits between the island (collectively) and mainland populations. Interspecific variation in the effects of isolation was likely related to differential vagility. These data generally corroborate other studies reporting relatively great geographical structuring within tropical birds over short distances. Behaviourally based traits - low vagility and high ‘sensitivity’ to geographical barriers - may underlie extensive diversification within neotropical forest birds, but more extensive ecological and phylogeographic information are needed on a diverse sample of species.     

花色素苷生物合成及花色的调控

近年来,花色研究工作备受关注。对于园艺学来说,要培育出自然界中原本没有的新颖花色,很有必要弄清控制花色形成的各种因素。随着分子生物学技术的迅速发展,对花色形成机制的研究已经深入到分子水平,本文主要介绍了花色素的合成与转运、液泡pH值、辅助色素和金属离子对花色的调控。     

Functional decoupling between flowers and leaves in the Ameroglossum pernambucense complex can facilitate local adaptation across a pollinator and climatic heterogeneous landscape

Decoupling between floral and leaf traits is expected in plants with specialized pollination systems to assure a precise flower–pollinator fit, irrespective of leaf variation associated with environmental heterogeneity (functional modularity). Nonetheless, developmental interactions among floral traits also decouple flowers from leaves regardless of selection pressures (developmental modularity). We tested functional modularity in the hummingbird‐pollinated flowers of the Ameroglossum pernambucense complex while controlling for developmental modularity. Using two functional traits responsible for flower–pollinator fit [floral tube length (TL) and anther–nectary distance (AN)], one floral trait not linked to pollination [sepal length (SL), control for developmental modularity] and one leaf trait [leaf length (LL)], we found evidence of flower functional modularity. Covariation between TL and AN was ca. two‐fold higher than the covariation of either of these traits with sepal and leaf lengths, and variations in TL and AN, important for a precise flower–pollinator fit, were smaller than SL and LL variations. Furthermore, we show that previously reported among‐population variation of flowers associated with local pollinator phenotypes was independent from SL and LL variations. These results suggest that TL and AN are functionally linked to fit pollinators and sufficiently decoupled from developmentally related floral traits (SL) and vegetative traits (LL). These results support previous evidences of population differentiation due to local adaptation in the A. pernambucense complex and shed light on the role of flower–leaf decoupling for local adaptation in species distributed across biotic and abiotic heterogeneous landscapes.     

Tongue-rolling phenotypes and geographical variation in the United Kingdom

The distribution of tongue-rolling phenotypes in a sample (n = 477) of undergraduate students of the University College of Swansea (U.K.) was studied. The birthplaces of these students were also recorded. England was divided into six areas, and Wales was left as an area on its own. The data suggest that those students who come from north-east are more non-rollers, which may be due to mixture with Scandinavians.