Myrmecophilic food body production in the understorey tree, Ryparosa kurrangii (Achariaceae), a rare Australian rainforest taxon

Plant food bodies are rarely observed in the field, because of continual harvesting, and are often first documented on isolated glasshouse plants. Little is known about the genus Ryparosa (Achariaceae), and the appearance of outgrowths on leaves and stems of glasshouse-raised R. kurrangii seedlings suggested that the species may produce food bodies. Detailed macroimaging and histological techniques were used to characterize chemomorphological variation in food body material gathered from glasshouse plants. Two distinct types of food body were observed. Multicellular pearl bodies derived from epidermal and mesophyll tissue were produced on young leaves and stems, and contained lipids and glycogen-like carbohydrates. A unique form of lipid-rich multicellular food body that 'opens' during development was found exclusively on mature plant tissue. A filament network was associated with food body lipid droplets. This is the first detailed documentation of food body production in an understorey genus adapted to low light conditions. We suggest that the distinctive spatial deployment of Ryparosa food rewards, and the ants attracted to them, may be invaluable for keeping long-lived leaves free from epiphyllous communities.     

Population genetics of Ryparosa kurrangii (Achariaceae), a rare lowland rainforest tree

Ryparosa kurrangii B.L. Webber (Achariaceae) is a rare lowland rainforest tree found in dense, discrete populations between the Daintree River and Cape Tribulation in Far North Queensland, Australia. It is one of many Australian rainforest trees thought to rely on the Southern Cassowary (Casuarius casuarius johnsonii) for long-distance seed dispersal. A survey of chloroplast non-coding DNA found no genetic variation at any of four non-coding chloroplast loci. Seedlings of three populations separated by a mountain range were then examined for amplified fragment length polymorphisms. High levels of genetic diversity were found within each population. Only two percent of the variation in this study was explained by separation due to the mountain range. This finding of high genetic diversity but minimal distinction between populations accords with general expectations for outcrossing, large-fruited, animal-dispersed trees. Either continuing or historical long-distance gene flow (mediated by cassowaries) could explain these results.     

Variability of Mn hyperaccumulation in the Australian rainforest tree Gossia bidwillii (Myrtaceae)

This study examines the heterogeneity of the Mn-hyperaccumulative trait in natural stands of the Australian rainforest tree species Gossia bidwillii (Myrtaceae). It is the only known Mn hyperaccumulator from Australia, and has an unusual spatial distribution of Mn in its leaves. G. bidwillii occurs naturally on a range of Mn-containing substrates including ultramafic soils. Leaf samples were collected from individual trees and four small stands, over a longitudinal range of ∼600 km. While no variation in the spatial distribution of foliar Mn was detected, considerable variation in Mn concentration was found. G. bidwillii was shown to accumulate Mn when growing on a variety of substrates, and dry weight (DW) foliar Mn concentrations of all trees sampled ranged between 2,740 and 27,470 μg g⁻¹. The majority of samples exceeded 10,000 μg g⁻¹, the threshold value for Mn hyperaccumulation. The overall frequency distribution of foliar Mn concentration was found to be bimodal, with a small outlier of extreme hyperaccumulators. Highest values were obtained from trees growing on a basaltic krasnozem clay, not ultramafic soil. Soil Mn concentrations were measured, and no relationship was found between foliar Mn concentrations and extractable Mn concentrations in host substrates. Some of the variation in the Mn-hyperaccumulative trait in G. bidwillii throughout its large natural distribution may reflect the unresolved taxonomy of this most widespread species in the genus Gossia. Ability to hyperaccumulate Mn may serve as an additional diagnostic tool for resolving this taxonomy.     

Cyanogenic glycosides from the rare Australian endemic rainforest tree Clerodendrum grayi (Lamiaceae)

The cyanogenic diglycoside lucumin ((R)-mandelonitrile-β-d-primeveroside) and monoglucoside prunasin ((R)-mandelonitrile-β-d-glucoside) were isolated from the foliage of the rare Australian rainforest tree species Clerodendrum grayi (Lamiaceae). This is the first reported isolation of the diglycoside lucumin from vegetative tissue (foliage), and the first reported co-occurrence of lucumin and prunasin. Furthermore, unusually, the diglycoside lucumin was the most abundant cyanogen accounting for approximately 60% of total cyanide in a leaf tissue.     

Isolation and characterization of eight polymorphic microsatellite loci in the rainforest canopy tree,Syzygium sayeri (Myrtaceae)

Eight polymorphic microsatellite loci were isolated from the rainforest canopy tree, Syzygium sayeri, in order to study parentage and subsequently pollen dispersal among individuals in wild populations. Screening of one natural population (n = 64) mapped in a 500 × 500 m area at Cape Tribulation, north Queensland, Australia, yielded two to 11 alleles per locus with observed levels of heterozygosity ranging from 0.07 to 0.70. One locus was significantly out of Hardy–Weinberg equilibrium after Bonferroni correction for multiple tests. These loci should provide a useful tool in further understanding the dispersal patterns of this species.     

Development of eight polymorphic microsatellites for an Australasian rainforest tree species,Cryptocarya mackinnoniana (Lauraceae)

We developed eight microsatellite markers for Cryptocarya mackinnoniana to study the spatial genetic structure and ecological correlates of parentage in secondary rainforests in Australia's Wet Tropics. The microsatellite loci were screened in 99 trees, and 623 seedlings < 0.24 m tall, at a site extending from primary rainforest into adjacent 50‐year‐old secondary rainforest. The eight loci were polymorphic, exhibiting between three and 11 alleles, and gene diversity (H_E) from 0.25 to 0.84. For the trees, no departures from Hardy–Weinberg equilibrium were detected, except at locus Cm03, which had an estimated null allele frequency of 0.0903. No locus combinations exhibited linkage disequilibrium.     

The seasonality of arboreal arthropods foraging within an Australian rainforest tree

Abstract.

• 1 The seasonality of arboreal arthropods foraging within the crown of the canopy tree Argyrodendron actinophyllum. Edlin (Sterculiaceae) was studied in a subtropical rain forest near Brisbane, Australia, during 2 years with interception traps and restricted canopy fogging.
• 2 Minimal air temperatures explained most of the seasonal variance in arthropod‘density activity'. However, the host phenology was important for several phytophagous groups. Rainfall, relative humidity and lunar phase influenced arthropod activity slightly.
• 3 Seasonal ranges were significantly different among arboreal guilds and were related to food resource availability in time, associated with both the host and the rainforest environment. Seasonal peaks of herbivores were more marked than in tropical rain forests, but less sharp than in temperate woodlands.'
• 4 Quantitative changes in arthropod density activity and abundance were important for most groups, with a marked trough during cool and dry months. The numerical contribution of most arthropod guilds to the arboreal community was not constant throughout the year.
• 5 Seasonal changes in the species composition of the arboreal community appeared not as a succession of well-defined subcommunities throughout the year, but as a continuum of species of extended seasonal ranges.
• 6 This subtropical insect-plant system presented several phenological features which were classified under tropical and temperate characteristics. This partition is open to discussion.

     

Chloroplast DNA variation in a rainforest tree (Aucoumea klaineana, burseraceae) in Gabon

One of the dominant savannah colonists in Gabon is Aucoumea klaineana or Okoumé (Burseraceae), an endemic species which belongs to a monotypic genus. Chloroplast DNA (cpDNA) variation was studied in this species by means of PCR amplification of 40 kb of cpDNA sequences, followed by restriction analysis of the resulting fragments. No insertion/deletion events were noted, and a single point mutation was found. The level of differentiation among the 19 populations studied was relatively low (GST = 0.54) compared to other plant species (mean of 0.76), in agreement with the pioneer status of the species. However, cpDNA diversity was geographically structured, with the less frequent haplotype occurring only in populations from southern Gabon. This distribution might suggest either that there were two ancient source populations of Okoumé, one in the north and the other in the south, from which the colonizing process of the savannah began after the last ice age, or alternatively that there was one polymorphic source in the south. The low level of cpDNA diversity could indicate that Okoumé populations in these refugia were quite small.     

Temporal and spatial variability in insect grazing of the canopies of five Australian rainforest tree species

Herbivory was measured monthly for 2 years on leaves of permanently marked replicate branches in the canopies of five Australian rainforest tree species. Variability in insect grazing activities was evident with respect to several factors:

• 1 leafage — young leaves were preferred over older leaf tissue:
• 2 height — leaves closer to ground level were more heavily grazed:
• 3 light — shade leaves were preferred to sun leaves:
• 4 time — grazing was intense during spring and summer months, and almost negligible during autumn and winter, but was cumulatively similar between the 2 years:
• 5 space — grazing was extremely variable on small spatial scales such as between individual leaves and branches, but similar where hundreds of leaves were pooled on larger scales between individual canopies and among geographically different sites:
• 6 tree abundance — grazing was heavier at sites where a tree species was common than where it was rare:
• 7 host tree species.

Long term observations resulted in higher but more accurate estimates of herbivory since it was possible to quantify losses of leaves totally eaten, an event not accounted for infield methods of discrete sampling whereby leaves are merely harvested and measured for area missing. Variability in herbivory is discussed in terms of plant-insect phenologies, plant defences, successional status of tree species, and insect behaviour.     

Species number, species abundance and body length of arboreal arthropods associated with an Australian rainforest tree

Abstract.

• 1 The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over-storey rainforest tree from Australia, Argyrodendron actinophyllum (Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2-year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.
• 2 The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log-series nor the log-normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.
• 3 The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three-dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.
• 4 Although several factors may complicate the interpretation of the three-dimensional plots, long-term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structure in rain forests.

     

Photosynthesis in an Australian rainforest tree,Argyrodendron peralatum,during the rapid development and relief of water deficits in the dry season

Summary Rates of apparent photosynthesis were measured in situ at five positions between the upper crown and a lower branch of a 34 m tall Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas tree, and on an understorey sapling of the same species growing in a northern Australian rainforest. At the end of the dry season, rapid reductions in photosynthetic rates occurred in the upper crown within three days after a rain event, but changes in the lower crown and the sapling were less marked. Complete recovery of photosynthesis followed a second rain event. At high photon flux densities, stomatal conductance to water vapour decreased in a curvilinear fashion as the vapour pressure difference between leaf and air increased. Apparent photosynthesis was linearly related to stomatal conductance on the first clear day after each rain event, but there was no relationship between these parameters at the end of a brief natural drying cycle. Under conditions of adequate water supply, stomatal conductances of both upper crown and understorey leaves increased linearly with increasing photon flux density up to about 300 mol m^-2 s^-1. During water deficits, stomatal conductances in leaves from the understorey increased much more rapidly at very low photon flux densities than did conductances in leaves from the upper canopy.     

Isolation of polymorphic microsatellite markers in the tree sparrow (Passer montanus)

To enable the study of the population genetics of the tree sparrow (Passer montanus), which is distributed in many islands of Japan, nine polymorphic microsatellite loci were isolated from 32 individuals. The number of alleles per locus ranged from 2 to 17, and observed heterozygosities ranged from 0.1250 to 0.9375. In eight of the nine loci, the heterozygosities were not significantly different from those expected from Hardy-Weinberg equilibrium. Cross-species amplification in the russet sparrow (P. rutilans) was successful with all primer sets, which were highly polymorphic, suggesting these markers are useful for the population genetics of genus Passer.     

C(4) photosynthesis in tree form euphorbia species from hawaiian rainforest sites

The ¹³C ¹²C isotope ratios and the leaf anatomy of 18 species and varieties of Euphorbia native to the Hawaian Islands indicated that all possess C₄ photosynthesis. These species range from small prostrate coastal strand shrubs to shrubs and trees in rainforest and bog habitats. The results show that C₄ photosynthesis occurs in plants from a much wider range of habitats and life-forms than has been previously reported.     

Measurement of tree diversity in the Nigerian rainforest

The diversity of trees 5 cm in diameter and above at breast height was studied at five sites within the Nigerian rainforest. The sites were Gambari, Oban, Omo, Owan and Sapoba forest reserves. Diversity was measured in terms of similarity and heterogeneity and explored at beta and gamma levels. Over 315 species were encountered during the study. In terms of species richness, there are 80, 226, 163, 137 and 159 species in Gambari, Oban, Omo, Owan and Sapoba, respectively. The occurrence of the species showed that, while 26 species are common to all the sites, 62, 17, 15, 8 and 6 species are restricted to Oban, Omo, Sapoba, Gambari and Owan, respectively. Ordination by detrended correspondence analysis indicated gradients along the first two axes. The first axis reflecting rainfall gradient which decreases from Oban through to Sapoba, Owan and Gambari. The second axis showed a separation of Omo, and Owan and Sapoba. This suggests a gradient of soil parent materials, the former site is on the basement complex while the latter is on the cretaceous rock. It is suggested that each forest should be managed based on its particular characteristics, such as species composition and abundance. Thus, forests with high species diversity but fewer numbers of individuals, such as in Oban, should be earmarked for conservation while species-rich forests with relatively more economic species, as in Sapoba and Omo, should be managed for sustained timber production. Floristically poor forest, such as those in Gambari and Owan, should be converted to plantations of fast growing species but with care taken to avoid exposing such sites to soil erosion.     

Genetic effects of rainforest fragmentation in an early successional tree (Elaeocarpus grandis)

Rainforests in Australia and around the world have been extensively cleared and degraded. It is essential to recognize the changes in population diversity and dynamics that follow habitat fragmentation if better conservation and management strategies are to be developed. This study is an investigation of the medium term (over 100 years) effects of rainforest fragmentation on a long-lived, early successional tree species within a habitat matrix that includes various types of fragmented and undisturbed sites. Five microsatellite loci were used to assess the level and distribution of genetic variation across the southern range of Elaeocarpus grandis (Elaeocarpaceae). In all, 21 sites were sampled to provide a direct comparison between fragmented and undisturbed populations. Overall levels of diversity (A=3.4, He=0.568, f=0.094) were higher than those of closely related endemic species, but lower than those recorded across other rainforest trees. No significant genetic structure was detected across this species, suggesting the existence of efficient dispersal and colonization mechanisms responsible for the maintenance of gene flow. Rainforest fragments, and in particular those within the extensively cleared Big Scrub, show a trend for increased inbreeding levels caused by a loss of heterozygosity within juvenile cohorts. However, the overall rate of genetic decline within fragmented rainforests appears to be more subtle in E. grandis than across other species. A combination of ecological attributes and evolutionary history is likely to have contributed to this outcome and need to be considered in future rainforest restoration projects.     

Isolation and characterization of polymorphic microsatellite loci from Aucoumea klaineana Pierre (Burseraceae), a tropical rainforest tree of Central Africa

Nineteen microsatellite loci were isolated using an enrichment protocol from Aucoumea klaineana Pierre (Okoumé, Burseraceae), a tropical rainforest tree of Central Africa. Polymorphism was investigated using 56 trees distributed throughout Gabon (four trees from 14 populations). All loci were polymorphic, with the number of alleles ranging from two to 15. High levels of variation were found among loci, and observed heterozygosity ranged from 0.05 to 0.77. These loci will be useful for the in‐depth analysis of population structure and phylogeographical variation throughout the distribution range of Okoumé.     

The arthropod community of an Australian rainforest tree: Abundance of component taxa,species richness and guild structure

Abstract The arthropod community within the crowns of Argyrodendron actmophyllum (Sterculiaceae) in a subtropical rainforest near Brisbane, Australia, was investigated during a 2 year study using interception traps and restricted canopy fogging. The total arthropod density was 34 individuals m^?2 of leaf area. Spiders, psyllids, thrips, psocids and chrysomelids were most abundant. The most diverse families included Curculionidae, Cicadellidae, Staphylin-idae, Cerambycidae, Theridiidae, and Chrysomelidae. The arboreal community of A. actinophyllum exhibited several features common to arthropod communities from temperate and tropical rainforest trees. Affinity with temperate trees was suggested by the relatively high densities of certain species, by high proportions (in terms of individuals) of sap-suckers and non-insect predators, and by a low proportion of ants. Affinity with tropical rainforest trees was expressed by high proportions of scavenging fauna, particularly wood-eaters and fungalfeeders.     

The dynamics of photosynthetic acclimation to changes in light quanlity and quality in three Australian rainforest tree species

Photosynthetic acclimation was studied in seedlings of three subtropical rainforest species representing early (Omalanthus populifolius), middle (Duboisia myoporoides) and late (Acmena ingens) successional stages in forest development. Changes in the photosynthetic characteristics of pre-existing leaves were observed following the transfer of plants between deep shade (1–5% of photosynthetically active radiation (PAR), selectively filtered to produce a red/far-red (R/FR) ratio of 0.1) and open glasshouse (60% PAR and a R/FR ratio of 1.1–1.2), and vice versa. The extent and rate of response of the photosynthetic characteristics of each species to changes in light environment were recorded in this simulation of gap formation and canopy closure/overtopping. The light regimes to which plants were exposed produced significant levels of acclimation in all the photosynthetic parameters examined. Following transfer from high to low light, the light-saturated rate of photosynthesis was maintained near pre-transfer levels for 7 days, after which it decreased to levels which closely approximated those in leaves which had developed in low light. The decrease in photosynthetic capacity was associated with lower apparent quantum yields and stomatal conductances. Dark respiration was the parameter most sensitive to changes in light environment, and responded significantly during the first 4–7 days after transfer. Acclimation of photosynthetic capacity to increases in irradiance was significant in two of the three species studied, but was clearly limited in comparison with that of new leaves produced in the high light conditions. This limitation was most pronounced in the early-successional-stage species, O. populifolius. It is likely that structural characteristics of the leaves, imposed at the time of leaf expansion, are largely responsible for the limitations in photosynthetic acclimation to increases in irradiance.     

An analysis of diet specialization in frugivorous Pteropus poliocephalus (Megachiroptera) in Australian subtropical rainforest

Abstract The Grey-headed flying fox Pteropus poliocephalus Temminck 1825 is the only mammalian frugivore to occupy substantial areas of the subtropical rainforests of eastern Australia. The composition of the P. poliocephalus diet and diet specialization in the species are therefore pertinent to studies of trophic structure, seed dispersal and evolutionary processes in these forests. During a three-year diet study, P. poliocephalus used fruits from 44 species of canopy and edge plants. Their taxonomically diverse diet was dominated by the Myrtaceae and Moraceae. Dietary specialization by P. poliocephalus was examined using two criteria: the influence of fruit morphology on diet choice and dietary overlap with sympatric avian frugivores. There was no evidence from either approach that they were specialist feeders. Initial analyses comparing the morphological characters of diet fruits with fruits available to P. poliocephalus during the study period showed a preference for white fruits, berries, syconia and fruits with multiple seeds, and avoidance of black fruits and drupes. However, these significant results were not sustained when the confounding effects of correlations between fruit morphology and other traits were considered. All, except the response to berries, could be attributed to either avoidance by P. poliocephalus of secondary compounds in the Lauraceae or selection for the beneficial phenology of Ficus. Dietary overlap with frugivorous birds was notably high and the fruit diet of P. poliocephalus formed a subset of the avian diet. Associations between fruit colour, size and protective mechanisms have been documented in other rainforest areas and have been proposed as indicators of coadaptive relationships between vertebrate frugivores and their diet plants. However, these associations were not apparent in the morphological characters of fleshy fruits from Australian subtropical rainforest trees. An explanatory hypothesis of primarily avian influence on fruit traits is presented.