New Zealand's pteridophyte flora—Plants of ancient lineage but recent arrival?

A hypothesis is presented that most pteridophytes arrived in New Zealand relatively recently, by long-distance dispersal. The flora comprises 194 native species, of which 89 (46%) are endemic and 105 (54%) are widespread. Of the latter, 90% are shared with temperate Australasia, 53% with tropical regions, 14% with temperate southern Africa and 13% with the circum-Antarctic islands and South America. New Zealand has undergone such dramatic changes in location, land area, and topography since initial separation from Gondwana 85 Ma that it seems improbable that the 95 species shared with temperate Australasia could have remained conspecific throughout that time. Modern fossil and molecular evidence strongly suggest that many families of ferns had not even evolved prior to separation, and palynological evidence from New Zealand indicates that 78% of pteridophyte genera first appeared there only after separation from Gondwana. Present-day distributions in New Zealand suggest that ferns have greater dispersal potential than flowering plants, and that pteridophyte distributions are more heavily influenced by temperature, rainfall, and geothermal activity than by geological history. Most endemic pteridophyte species have a predominantly southern distribution pattern and are characteristic of cool, lowland to montane forest. Pteridophytes in the northern part of New Zealand show a lower level of endemism than elsewhere and tend to be widespread species that have arrived from temperate Australasian and tropical regions. There is also evidence that at least some pteridophytes have migrated from New Zealand to Australia. It is suggested that the hypothesis of long-distance dispersal of pteridophytes across the Tasman Sea could be tested by molecular techniques.     

幕阜山脉石松类和蕨类植物多样性及生物地理学特征

通过资料收集及野外调查, 得出幕阜山脉地区共有石松类和蕨类植物26科72属261种, 具有一定的东西过渡性, 为鳞毛蕨-铁角蕨植物区系, 最大属为鳞毛蕨属(Dryopteris) (29种)。其中, 庐山的物种丰富度较高(224种), 以铁角蕨属(Asplenium)为主; 幕阜山的物种密度较大(2.09种/km ²), 以卷柏属(Selaginella)为主; 九宫山以瓦韦属(Lepisorus)为主; 三者共通种有95种, 新特有现象较丰富。该区属种分化限制明显, 表现在单种科、属及寡种科、属占总科数的60%及总属数的80%。从区系成分看, 该区科、属以热带成分为主, 科和属的热带性成分与温带性成分比值(R/T值)分别为2.6和2.3。与同纬度带山地石松类和蕨类植物属的R/T值比较, 中亚热带与北亚热带交界带的蕨类植物属的R/T值在2.18-2.36之间; 种的R/T值为0.2, 为热带成分的5倍, 表现出明显的温带性质, 是罗霄山脉植物区系温带成分的重要组成部分。该区石松类和蕨类植物区系与华东、华南植物区系联系比较紧密, 表现出华东与华南两区系成分的交汇。     

Contrasting Predictors of Fern versus Angiosperm Decomposition in a Common Garden

We evaluated differences in the rates and correlates of decomposition among 32 fern and angiosperm litter types collected in Hawai'i. Leptosporangiate ferns were separated into groups based on phylogeny: 'polypod' ferns, a monophyletic clade of ferns that diversified in the Cretaceous, and all other ('non-polypod') ferns that diversified earlier. We measured initial litter chemistry (nutrients and carbon chemistry), and mass loss and nitrogen (N), phosphorus (P), and calcium (Ca) of litter tissue during a 1-yr incubation in a common garden. Nutrient concentrations and carbon (C) chemistry differed significantly among litter types, and litter turnover ( k -values) ranged from 0.29 to 8.31. Decomposition rates were more closely correlated with nutrient concentration than is typically observed. Lignin:N was the best predictor of decomposition across all litter types combined; however, among plant groups different predictors of decomposition were important. Nitrogen and P concentrations best predicted fern decomposition, whereas C chemistry, particularly lignin concentration, was more important for angiosperm (monocot and dicot) decomposition. Among native plants, non-polypod ferns decomposed significantly more slowly than both polypod ferns and angiosperms. Contrary to our hypothesis, fern litter did not decompose more slowly than angiosperm litter overall. Nutrient dynamics in litter were affected by initial litter concentration more than phylogeny; low-nutrient litter immobilized more nutrients than high-nutrient litter. Systematic differences in rates of decomposition, and the importance of nutrients in predicting fern decomposition, imply that changes in species composition within ferns and between ferns and angiosperms could influence the functioning of ecosystems where ferns are important forest components.     

Evolution of DNA amounts across land plants (embryophyta)

BACKGROUND AND AIMS: DNA C-values in land plants (comprising bryophytes, lycophytes, monilophytes, gymnosperms and angiosperms) vary approximately 1000-fold from approx. 0.11 to 127.4 pg. To understand the evolutionary significance of this huge variation it is essential to evaluate the phylogenetic component. Recent increases in C-value data (e.g. Plant DNA C-values database; release 2.0, January 2003; http://www.rbgkew.org.uk/cval/homepage.html) together with improved consensus of relationships between and within land plant groups makes such an analysis timely. METHODS: Insights into the distribution of C-values in each group of land plants were gained by superimposing available C-value data (4119 angiosperms, 181 gymnosperms, 63 monilophytes, 4 lycophytes and 171 bryophytes) onto phylogenetic trees. To enable ancestral C-values to be reconstructed for clades within land plants, character-state mapping with parsimony and MacClade was also applied. KEY RESULTS AND CONCLUSIONS: Different land plant groups are characterized by different C-value profiles, distribution of C-values and ancestral C-values. For example, the large ( approximately 1000-fold) range yet strongly skewed distribution of C-values in angiosperms contrasts with the very narrow 12-fold range in bryophytes. Further, character-state mapping showed that the ancestral genome sizes of both angiosperms and bryophytes were reconstructed as very small (i.e. < or =1.4 pg) whereas gymnosperms and most branches of monilophytes were reconstructed with intermediate C-values (i.e. >3.5, <14.0 pg). More in-depth analyses provided evidence for several independent increases and decreases in C-values; for example, decreases in Gnetaceae (Gymnosperms) and heterosperous water ferns (monilophytes); increases in Santalales and some monocots (both angiosperms), Pinaceae, Sciadopityaceae and Cephalotaxaceae (Gymnosperms) and possibly in the Psilotaceae + Ophioglossaceae clade (monilophytes). Thus, in agreement with several focused studies within angiosperm families and genera showing that C-values may both increase and decrease, it is apparent that this dynamic pattern of genome size evolution is repeated on a broad scale across land plants.     

Ant protection of the nectaried fern Polypodium plebeium in central Mexico

Nectaries on fronds of Polypodium spp. have been studied previously only in cultivated specimens. We conducted field observations in middle-elevation forests in Mexico and found five ant species associated with nectaries of Polypodium plebeium and P. lepidotrichum. To investigate whether nectaries promote protection against herbivores, we performed ant-exclusion experiments with nectary-bearing ferns (P. plebeium) and other ferns without nectaries (Polypodium plesiosorum, P. furfuraceum, and Phlebodium pseudoaureum). When ants were excluded from the developing fronds of Polypodium plebeium, damage from foliage-feeding sawfly and lepidopteran caterpillars was significantly greater than in control fronds. Ferns without nectaries did not show a difference in damage between ant-excluded and control fronds. Our results demonstrate that fern nectaries can support ant defense of the plant body as do the extrafloral nectaries of many angiosperms.     

Biological invasion on an oceanic island mountain: Do alien plant species have wider ecological ranges than native species?

Abstract. Spatial distribution patterns of alien plant species were compared with those of native species on a windward slope of Mt. Haleakala (3055 m). Oceanic islands are considered susceptible to biological invasion, and this study numerically tested this circumstantial evidence with the following questions: Are all habitats equally susceptible; and, do successful invaders have wider realized niches than natives? The mountain slope consists of three distinct altitudinal bioclimatic zones (hot moist lowland, wet montane cloud, and cool arid high-altitude zones). Ordination indicated that alien species' ranges and population expansions were clustered in the lowland and high-altitude zones. The lowland zone had been subjected to natural canopy dieback, and the high-altitude zone to grazing by domestic and feral ungulates. By contrast, the montane cloud forest was relatively intact in terms of number and cover of native species. Thus, susceptibility to alien invasion clearly differed among zones, and the primary causes seemed to be the obvious disturbance factors. The mean ecological range along the altitude-rainfall gradient was significantly (P < 0.05) greater for native than for alien species in most life-form groups. The reasons for the greater number of climate generalists among the natives vs. the range-restricted aliens appear to be related to: (1) the pre-alien condition with a depauperate flora which allowed for ‘ecological release’ of successful native colonizers, and (2) the climatic pre-adaptation of alien invaders which restricts them from penetrating over a broader spectrum of climatic zones in a floristic matrix subjected to increasing interspecific competition.     

Riqueza y Distribución Ecológica de Especies de Pteridofitas en la Zona del Río Yavarí-Mirín, Amazonía Peruana

We studied the ecological distribution of pteridophytes (ferns and fern allies) along eight 8-km transects covering 12.7 ha in Peruvian Amazonia. Subunits of 200 m² of the transects have previously been classified into four different forest types, and here we document and quantify the floristic differences among these forest types. Pteridophytes have been suggested as an indicator group to classify rain forest habitats, but this requires that the ecological preferences of the species are well documented and consistent across geographic regions. Here we analyzed in detail the distribution and diversity patterns of 130 species across the four rain forest types. Relative species abundance and species diversity were similar among some of the forest types and differed among others, but the species composition differed markedly. Our results largely confirmed the earlier interpretation of the edaphic preferences of the pteridophyte species in western Amazonia. This supports the proposition that deterministic processes have an important role in influencing the floristic composition of Amazonian forests.     

云南纳板河保护区蕨类植物区系地理研究

通过多次野外调查及资料整理,对纳板河流域国家级自然保护区蕨类植物的区系组成、地理成分、区系联系、性质及起源等方面进行了分析研究。结果显示:(1)纳板河保护区共有蕨类植物43科90属239种,优势科为水龙骨科、金星蕨科、凤尾蕨科、蹄盖蕨科、三叉蕨科,优势属为凤尾蕨属、鳞盖蕨属、毛蕨属、石韦属。(2)纳板河保护区蕨类植物区系具有明显的热带向亚热带过渡的性质,当属热带亚洲蕨类植物区系,但在一定程度上受到中国-喜马拉雅蕨类植物区系的影响。(3)纳板河保护区在地理亲缘关系上与云南大围山最为密切,与海南岛、哀牢山保护区的关系次之,与苍山、轿子雪山及雕林山保护区的联系较为疏远。