Ecology of an Improbable Association: The Pseudomyrmecine Plant‐ant Tetraponera tessmanni and the Myrmecophytic Liana Vitex thyrsiflora (Lamiaceae) in Cameroon1

In young individuals of the obligate myrmecophytic liana Vitex thyrsiflora, several species of ants and other arthropods compete for resources offered by the plant. In mature individuals, the only inhabitant is the ant species Tetraponera tessmanni, which is completely restricted to Vitex lianas as its sole host. Established colonies of this ant provide effective defense against herbivores. The association between V. thyrsiflora and T. tessmanni is unusual in two respects. First, the climbing life form is rare among myrmecophytes. Secondly, it is surprising that a pseudomyrmecine should be the obligate associate of a liana. Pseudomyrmecine plant‐ants often prune vegetation contacting their host plant. This behavior functions in part to protect against invasion of the host by ecologically dominant ants. In contrast, T. tessmanni does not prune and is associated with a plant whose success, and thus that of its resident ant colony, depends on contacts with many other plants. Several traits of V. thyrsiflora and T. tessmanni combine to make the colonization of host plants by potential competitors very difficult. These include behavioral and morphological filters restricting entrance into the plant and exploitation of the resources it can supply; plant anatomical organization that enables T. tessmanni workers to carry out all activities, except leaf patrolling, within a single, branched private nesting space within which all food resources offered by the plant are produced; and polygyny, permitting the colony to monopolize a large, rapidly growing and long‐lived territory.     

Increasing liana abundance and biomass in tropical forests: emerging patterns and putative mechanisms

Tropical forests are experiencing large-scale structural changes, the most apparent of which may be the increase in liana (woody vine) abundance and biomass. Lianas permeate most lowland tropical forests, where they can have a huge effect on tree diversity, recruitment, growth and survival, which, in turn, can alter tree community composition, carbon storage and carbon, nutrient and water fluxes. Consequently, increasing liana abundance and biomass have potentially profound ramifications for tropical forest composition and functioning. Currently, eight studies support the pattern of increasing liana abundance and biomass in American tropical and subtropical forests, whereas two studies, both from Africa, do not. The putative mechanisms to explain increasing lianas include increasing evapotranspirative demand, increasing forest disturbance and turnover, changes in land use and fragmentation and elevated atmospheric CO?. Each of these mechanisms probably contributes to the observed patterns of increasing liana abundance and biomass, and the mechanisms are likely to be interrelated and synergistic. To determine whether liana increases are occurring throughout the tropics and to determine the mechanisms responsible for the observed patterns, a widespread network of large-scale, long-term monitoring plots combined with observational and manipulative studies that more directly investigate the putative mechanisms are essential.     

Traits and ecological strategies of Australian tropical and temperate climbing plants

Aim Understanding large scale patterns in trait variation in climbing plants (lianas, vines, scramblers, twiners) is important for the development of a stronger theoretical understanding of climbing plant ecology and for more applied issues such as prediction of community assembly under changing climatic conditions. We compared values of five key functional traits for 388 species of climbing plant from tropical and temperate regions of Australia to quantify variation between these two biogeographic regions. Location Australia. Methods Data on dispersal mode, growth habit, leaf form, leaf size and seed mass were compiled from field measurements and published sources. Comparative analyses were performed in three ways: (1) across species where each species was treated as an independent data point, (2) using evolutionary divergence analyses for each trait, and (3) in multidimensional space using a matrix of similarities between species. Results Tropical climbing plants had 22‐fold greater seed mass and four times greater leaf size than did temperate species. Tropical climbers were more likely to be woody (63%) than were temperate species (40%). Surprisingly we found a similar proportion of animal‐dispersed seeds in the two regions, although we expected animal‐dispersed seeds to be more prevalent in the tropics. We also found similar proportions of simple‐ and compound‐leaved species between the two regions. All of our findings were consistent between cross‐species and phylogenetic analyses indicating that patterns in present‐day species are reflected in the evolutionary history of Australian climbers. Multivariate analyses suggested that there is a spectrum of variation among climbing plants, with tropical species having greater seed mass, leaf size and woody growth compared with temperate climbing plant species. Main conclusions Tropical and temperate climbers of Australia exhibit a mixture of similar and contrasting traits and ecological strategies. Understanding strategy variation along latitudinal gradients will be particularly informative for predicting ecosystem and community structure with climate change.     

The Growth Form of Croton pullei (Euphorbiaceae) - Functional Morphology and Biomechanics of a Neotropical Liana

Abstract: Croton pullei (Euphorbiaceae) is a woody climber of the lowland rainforest in French Guyana and Surinam. During ontogeny, a shift from a juvenile free-standing growth phase to an older supported growth phase is observed. The following biomechanical parameters were studied: structural Young's modulus, structural torsional modulus, flexural stiffness and bend to twist ratios. Changes in anatomical development were also analysed for different stages of development of C. pullei which differ significantly in their mechanical properties. Free-standing plants show a nearly constant structural Young's modulus and structural torsional modulus during ontogeny, with flexural stiffness increasing proportionally with the axial second moment of area. These patterns are typical for “semi-self-supporting plants". In contrast, supported plants show a significant decrease in structural Young's modulus in older stem parts, as well as a decrease in structural torsional modulus. Due to the decrease in structural Young's modulus, flexural stiffness does not increase proportionally with the axial second moment of area. These patterns are typical for non-self-supporting lianas. In all supported plants, a sudden transition occurs from early dense wood to a wood type with a much higher proportion of large diameter vessels. In contrast, only the dense wood type is present in all tested free-standing plants. The data are compared with results from other climbing species of the same study area and discussed with reference to observed features characterizing the growth form and life history of C. pullei.     

Midday depression of photosynthesis in <Emphasis Type="Italic">Enkleia malaccensis</Emphasis>, a woody climber in a tropical rainforest

We measured the diurnal changes in net photosynthetic rate (P _N) and stomatal conductance (g _s) of the leaves of a liana, Enkleia malaccensis Griff. (Thymelaeaceae), at the canopy level in the lowland tropical rainforest at Pasoh, Peninsular Malaysia. The measurements were made from a canopy walkway system, 30 m from the ground for 3 d in March 2003. P _N increased with increasing photosynthetically active radiation (PAR) before noon, though P _N was not enhanced by the strong radiation hit in the afternoon. Plotting g _s at saturating PAR (>0.5 mmol m⁻² s⁻¹) against the vapour pressure deficit (VPD) failed to reveal a significant correlation between VPD and g _s, and g _s became very low at VPD >2.5 kPa. The relationship between P _N and g _s was fitted on the same regression line irrespective of measuring day, indicating that this relationship was not influenced by either VPD or leaf temperature (T _L). Therefore, in the liana E. malaccensis, an increase in VPD leads to partial stomatal closure and, subsequently, reductions in P _N and the midday depression of P _N of this plant.     

The cost of being valuable: predictors of extinction risk in marine invertebrates exploited as luxury seafood

Extinction risk has been linked to biological and anthropogenic variables. Prediction of extinction risk in valuable fauna may not follow mainstream drivers when species are exploited for international markets. We use results from an International Union for Conservation of Nature Red List assessment of extinction risk in all 377 known species of sea cucumber within the order Aspidochirotida, many of which are exploited worldwide as luxury seafood for Asian markets. Extinction risk was primarily driven by high market value, compounded by accessibility and familiarity (well known) in the marketplace. Extinction risk in marine animals often relates closely to body size and small geographical range but our study shows a clear exception. Conservation must not lose sight of common species, especially those of high value. Greater human population density and poorer economies in the geographical ranges of endangered species illustrate that anthropogenic variables can also predict extinction risks in marine animals. Local-level regulatory measures must prevent opportunistic exploitation of high-value species. Trade agreements, for example CITES, may aid conservation but will depend on international technical support to low-income tropical countries. The high proportion of data deficient species also stresses a need for research on the ecology and population demographics of unglamorous invertebrates.     

滇南勐宋热带山地雨林木质藤本多样性研究

调查滇南勐宋山地雨林沟谷与坡地两种生境中木质藤本种的丰富度、径级分布、攀缘方式以及样地中被藤本缠绕的树木(dbh≥5cm)的数量和比率。结果表明:沟谷与坡地胸径≥1cm的木质藤本平均密度分别为95.7株/0.1hm2、57株/0.1hm2。调查样地内木质藤本共64种,隶属30个科。茎缠绕是最主要的攀缘方式,占总个体数的57%,卷须缠绕种所占比重最小,仅占3%;沟谷与坡地所调查树木被木质藤本缠绕的比例分别为43.7%和28.6%。与亚洲其它热带地区森林相比,勐宋地区藤本的多样性低,但是木质藤本的密度相当高,并且在一些样地中出现了大型木质藤本,这些可能与该地区森林的演替状态有关。     

In vitro propagation of Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae)

Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae), a West African liana producing naphthylisoquinoline alkaloids, was successfully raised from seeds in vitro. Clonal propagation was best achieved growing nodal stem segments on 1/5 Linsmaier and Skoog medium with full strength organics and supplemented with 0.02 μM thidiazuron, 4.44 μM 6-benzylaminopurine and 0.05 μM 1-naphthaleneacetic acid. Detached axillary shoots were grown on Anderson's Rhododendron medium devoid of phytohormones and rooted within one month when dipped in 4.92 μM indole-3-butyric acid. Rooted plants became acclimatized to nonsterile greenhouse conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

湖南黄桑国家级自然保护区野生藤本植物多样性和生态特征

采用野外实地调查、标本采集和室内查证相结合的方法,对湖南黄桑国家级自然保护区野生藤本植物多样性和生态特征进行了系统研究,为湖南黄桑野生藤本植物资源的保护与可持续利用提供依据。结果表明:（1）湖南黄桑自然保护区共有藤本植物45科113属250种,分别占该区种子植物科、属、种的21.13%、13.33%、12.32%,其中蕨类植物3科3属3种,被子植物42科110属247种;在被子植物中,双子叶藤本具有明显的优势,有37科105属223种,单子叶藤本处于次要地位,仅有5科5属24种。（2）该保护区的区系藤本植物中,含10个种以下的科和属分别占总科数、总属数的82.22%和97.35%,优势科主要有葡萄科、毛茛科、蝶形花科、蔷薇科、卫矛科、旋花科、薯蓣科、葫芦科等,优势属主要有铁线莲属、悬钩子属、猕猴桃属、葡萄属、菝葜属、薯蓣属等。（3）在观赏特性方面,该保护区的大部分藤本植物都具有2种以上的观赏特性,其中以观叶的最多,占总种数的92.80%,观茎的最少,仅占总种数的2.00%。（4）在攀援方式方面,该保护区的缠绕藤本植物具有优势,占总种数的46.40%,搭靠类、卷曲类和吸固类较少,分别占总种数的24.40%、18.00%和11.20%。（5）在生活型方面,以高位芽藤本植物为主导,占总种数的80.80%,一年生、地下芽和地上芽藤本植物较少,分别占总种数的10.80%、7.60%和0.80%。（6）在繁育系统方面,以两性花为主,单性花中雌雄异株种数多于雌雄同株,两性花、单性花和杂性花分别占70.40%、28.40%和1.20%。（7）湖南黄桑自然保护区的植物区系组成以热带分布类型为主,热带分布属共有72属,占总属数的63.72%。