Latitudinal diversity gradients in bryophytes and woody plants: Roles of temperature and water availability

It remains unclear whether the latitudinal diversity gradients of micro- and macro-organisms are driven by the same macro-environmental variables. We used the newly completed species catalog and distribution information of bryophytes in China to explore their spatial species richness patterns, and to investigate the underlying roles of energy availability, climatic seasonality, and environmental heterogeneity in shaping these patterns. We then compared these patterns to those found for woody plants. We found that, unlike woody plants, mosses and liverworts showed only weakly negative latitudinal trends in species richness. The spatial patterns of liverwort richness and moss richness were overwhelmingly explained by contemporary environmental variables, although explained variation was lower than that for woody plants. Similar to woody plants, energy and climatic seasonality hypotheses dominate as explanatory variables but show high redundancy in shaping the distribution of bryophytes. Water variables, that is, the annual availability, intra-annual variability and spatial heterogeneity in precipitation, played a predominant role in explaining spatial variation of species richness of bryophytes, especially for liverworts, whereas woody plant richness was affected most by temperature variables. We suggest that further research on spatial patterns of bryophytes should incorporate the knowledge on their ecophysiology and evolution.     

BryForTrait – A life‐history trait database of forest bryophytes

In ecological research, plant functional trait analyses are widely applied to understand to what extent the inter‐specific variation in trait attributes has an adaptive value or to predict ecosystem processes and changes. Compared to vascular plants, trait studies using bryophytes are scarce, which is likely due to missing trait information for bryophyte species. With the BryForTrait database, we want to reduce this deficit. Our database represents a compilation of autecological information and morphological and regenerative trait data on different stages of the life cycle of bryophytes occurring in forest ecosystems. The database contains information for 35 traits and 721 Central European bryophyte species; in total more than 23,000 trait values. The BryForTrait database will enable future trait studies, providing new insights into bryophyte‐dominated ecosystems.     

The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.     

A comparison of altitudinal species richness patterns of bryophytes with other plant groups in Nepal, Central Himalaya

Aim To explore species richness patterns in liverworts and mosses along a central Himalayan altitudinal gradient in Nepal (100–5500 m a.s.l.) and to compare these patterns with patterns observed for ferns and flowering plants. We also evaluate the potential importance of Rapoport’s elevational rule in explaining the observed richness patterns for liverworts and mosses. Location Nepal, Central Himalaya. Methods We used published data on the altitudinal ranges of over 840 Nepalese mosses and liverworts to interpolate presence between maximum and minimum recorded elevations, thereby giving estimates of species richness for 100‐m altitudinal bands. These were compared with previously published patterns for ferns and flowering plants, derived in the same way. Rapoport’s elevational rule was assessed by correlation analyses and the statistical significance of the observed correlations was evaluated by Monte Carlo simulations. Results There are strong correlations between richness of the four groups of plants. A humped, unimodal relationship between species richness and altitude was observed for both liverworts and mosses, with maximum richness at 2800 m and 2500 m, respectively. These peaks contrast with the richness peak of ferns at 1900 m and of vascular plants, which have a plateau in species richness between 1500 and 2500 m. Endemic liverworts have their maximum richness at 3300 m, whereas non‐endemic liverworts show their maximum richness at 2700 m. The proportion of endemic species is highest at about 4250 m. There is no support from Nepalese mosses for Rapoport’s elevational rule. Despite a high correlation between altitude and elevational range for Nepalese liverworts, results from null simulation models suggest that no clear conclusions can be made about whether liverworts support Rapoport’s elevational rule. Main conclusions Different demands for climatic variables such as available energy and water may be the main reason for the differences between the observed patterns for the four plant groups. The mid‐domain effect may explain part of the observed pattern in moss and liverwort richness but it probably only works as a modifier of the main underlying relationship between climate and species richness.     

Tree species composition and diversity in Miombo woodlands between co‐managed and government‐managed regimes,Malawi

Comparative information on the composition and diversity in tree species associations in Miombo woodland is limited. This study assessed how tree species associations across forest reserves of Miombo woodland in Malawi varied in composition and diversity concerning site factors and resource use disturbances under co‐management versus government management. Eighty nested circular plots, randomly selected in ArcGIS, were sampled to record stem diameter at breast height (DBH) of tree species: 0.04 ha for stems 5–29.9 cm DBH and 0.16 ha for stems ≥30 cm DBH. The recorded 109 tree species grouped into communities and 14 sub‐communities, using stem counts by species in TWINSPAN analysis. Sub‐divisions to level 5 showed eigenvalues ≥0.3, symbolising the stability of sub‐divisions. North/South sub‐divisions related to site factors; historical/current resource use influenced differences at levels 3–5. Species importance differed, indicating few important species in each sub‐community. Brachystegia and Julbernardia species showed importance across sub‐communities while Uapaca sansibarica in government management. Disturbances stimulated high species diversity. Recommendations include the need for a policy review towards group‐felling mature stands to stimulate regeneration and selective thinning of suppressed stems in stand development stages to maintain species diversity, productive recovery, diverse resource use value, and monitoring of harvesting impacts.     

No evidence for consistent long‐term growth stimulation of 13 tropical tree species: results from tree‐ring analysis

The important role of tropical forests in the global carbon cycle makes it imperative to assess changes in their carbon dynamics for accurate projections of future climate–vegetation feedbacks. Forest monitoring studies conducted over the past decades have found evidence for both increasing and decreasing growth rates of tropical forest trees. The limited duration of these studies restrained analyses to decadal scales, and it is still unclear whether growth changes occurred over longer time scales, as would be expected if CO₂‐fertilization stimulated tree growth. Furthermore, studies have so far dealt with changes in biomass gain at forest‐stand level, but insights into species‐specific growth changes – that ultimately determine community‐level responses – are lacking. Here, we analyse species‐specific growth changes on a centennial scale, using growth data from tree‐ring analysis for 13 tree species (~1300 trees), from three sites distributed across the tropics. We used an established (regional curve standardization) and a new (size‐class isolation) growth‐trend detection method and explicitly assessed the influence of biases on the trend detection. In addition, we assessed whether aggregated trends were present within and across study sites. We found evidence for decreasing growth rates over time for 8–10 species, whereas increases were noted for two species and one showed no trend. Additionally, we found evidence for weak aggregated growth decreases at the site in Thailand and when analysing all sites simultaneously. The observed growth reductions suggest deteriorating growth conditions, perhaps due to warming. However, other causes cannot be excluded, such as recovery from large‐scale disturbances or changing forest dynamics. Our findings contrast growth patterns that would be expected if elevated CO₂ would stimulate tree growth. These results suggest that commonly assumed growth increases of tropical forests may not occur, which could lead to erroneous predictions of carbon dynamics of tropical forest under climate change.     

Phylogenetic diversity,trait diversity and niches: species assembly of ferns along a tropical elevational gradient

Aim To analyse the structure of pteridophyte assemblages, based on phylogenetic relatedness and trait properties, along an elevational gradient. Ecological theory predicts that co‐occurring species may be: randomly selected from a regional pool; ecologically sorted so that they are functionally different hence resulting in reduced competition (overdispersion); or functionally similar as an adaptation to specific ecological conditions (clustering). Location Braulio Carrillo National Park and Cerro de la Muerte, Costa Rica, Central America. Methods We used an empirical dataset of the quantitative pattern of species occurrences and individual numbers of ferns within 156 plots along a tropical elevational gradient to test whether directed ecological sorting might cause deviations in patterns of trait and phylogenetic diversity. Mean pairwise distances of species based on phylogenetic and trait properties were compared with two different sets of null assemblages, one maintaining species frequency distributions (constrained) and one not (unconstrained). Results Applying different null models resulted in varying degrees of overdispersion and clustering, but overall patterns of deviation from random expectations remained the same. Contrary to theoretical predictions, phylogenetic and trait diversity were relatively independent from one another. Phylogenetic diversity showed no patterns along the elevational gradient, whereas trait diversity showed significant trends for epiphytes. Main conclusions Under stressful environmental conditions (drought at low elevations and frost at high elevations), epiphytic fern assemblages tended to be clustered with respect to trait characteristics, which suggests environmental filtering. Conversely, under less extreme environmental conditions (middle of the transect), the sorting was biased towards high differentiation (overdispersion), presumably because of interspecific competition and trait shifts among closely related species (character displacement).     

Continental‐scale tree‐ring‐based projection of Douglas‐fir growth: Testing the limits of space‐for‐time substitution

A central challenge in global change research is the projection of the future behavior of a system based upon past observations. Tree‐ring data have been used increasingly over the last decade to project tree growth and forest ecosystem vulnerability under future climate conditions. But how can the response of tree growth to past climate variation predict the future, when the future does not look like the past? Space‐for‐time substitution (SFTS) is one way to overcome the problem of extrapolation: the response at a given location in a warmer future is assumed to follow the response at a warmer location today. Here we evaluated an SFTS approach to projecting future growth of Douglas‐fir (Pseudotsuga menziesii), a species that occupies an exceptionally large environmental space in North America. We fit a hierarchical mixed‐effects model to capture ring‐width variability in response to spatial and temporal variation in climate. We found opposing gradients for productivity and climate sensitivity with highest growth rates and weakest response to interannual climate variation in the mesic coastal part of Douglas‐fir's range; narrower rings and stronger climate sensitivity occurred across the semi‐arid interior. Ring‐width response to spatial versus temporal temperature variation was opposite in sign, suggesting that spatial variation in productivity, caused by local adaptation and other slow processes, cannot be used to anticipate changes in productivity caused by rapid climate change. We thus substituted only climate sensitivities when projecting future tree growth. Growth declines were projected across much of Douglas‐fir's distribution, with largest relative decreases in the semiarid U.S. Interior West and smallest in the mesic Pacific Northwest. We further highlight the strengths of mixed‐effects modeling for reviving a conceptual cornerstone of dendroecology, Cook's 1987 aggregate growth model, and the great potential to use tree‐ring networks and results as a calibration target for next‐generation vegetation models.     

Building the Coleoptera tree‐of‐life for >8000 species: composition of public DNA data and fit with Linnaean classification

The species representation of public databases is growing rapidly and permits increasingly detailed phylogenetic inferences. We present a supermatrix based on all gene sequences of Coleoptera available in Genbank for two nuclear (18S and 28S rRNA) and two mitochondrial (rrnL and cox1) genes. After filtering for unique species names and the addition of ?2000 unpublished sequences for cox1 and 18S rRNA, the resulting data matrix included 8441 species‐level terminals and 6600 aligned nucleotide positions. The concatenated matrix represents the equivalent of 2.17% of the 390 000 described species of Coleoptera and includes 152 beetle families. The remaining 29 families constitute small lineages with ?250 known species in total. Taxonomic coverage remains low for several major lineages, including Buprestidae (0.16% of described species), Staphylinidae (1.03%), Tenebrionidae (0.90%) and Cerambycidae (0.58%). The current taxon sampling was strongly biased towards the Northern Hemisphere. Phylogenetic trees obtained from the supermatrix were in very good agreement with the Linnaean classification, in particular at the family level, but lower for the subfamily and lowest for the genus level. The topology supports the basal split of Derodontidae and Scirtoidea from the remaining Polyphaga, and the broad paraphyly of Cucujoidea. The data extraction pipeline and detailed tree provide a framework for placement of any new sequences, including environmental samples, into a DNA‐based classification system of Coleoptera.     

重庆市不同年龄综合公园绿化乔木树种多样性和组成的比较研究

该研究通过对重庆市不同时期(解放前、直辖前、直辖后)建造的15个综合公园的绿化乔木树种进行调查,分析了公园年龄对绿化乔木多样性和组成的影响以及公园之间的同质化情况。结果表明:(1)共调查到乔木59种,隶属于28科48属。其中,乡土树种占81.36%,外来树种占18.64%。(2)不同年龄公园乔木物种丰富度之间虽无显著差异,但解放后和直辖后公园乔木多度明显高于解放前;不同年龄公园外来树种的比例无显著差异;黄葛树、雅榕、复羽叶栾树在公园中的应用呈减少趋势,而日本晚樱、荷花玉兰、木犀、黄兰在绿化中的应用却呈增加趋势。(3)不同年龄公园之间同质化程度较低,解放前公园植物群落间Jaccard相似性指数明显高于其他两个阶段,且公园之间的Jaccard相似性指数与公园年龄差距无显著相关关系。综上结果发现,我国历史因素、园林文化和近代城市绿化相关规定可能是外来物种使用的限制因子,并可能导致了小尺度植物群落同质化程度偏低的现象。     

A critical comparison between two classical and a kit‐based method for mitochondria isolation

Numerous protocols for isolation of mitochondria are available. Here, three methods for the isolation of intact mitochondria from mouse liver tissues are compared with regard to yield, purity and activity. Mitochondria were isolated by sucrose density gradient ultracentrifugation, free‐flow electrophoresis or a commercially available kit‐based method. Our analyses show that the sophisticated (and most expensive) free‐flow electrophoresis method enables isolation of intact mitochondria with an enrichment of approximately 70%. Using the classical density centrifugation method is very laborious and time‐consuming, but delivers about 57% intact mitochondria. Using standard laboratory equipment in a quick and simple procedure, the kit provides approximately 50% intact mitochondria, suitable for most standard investigations.     

Production of recombinant HIV‐1 nef protein using different expression host systems: A techno‐economical comparison

Three popular expression host systems Escherichia coli, Pichia pastoris and Drosophila S2 were analyzed techno‐economically using HIV‐1 Nef protein as the model product. On scale of 100 mg protein, the labor costs corresponded to 52–83% of the manufacturing costs. When analyzing the cost impact of the different phases (strain/cell line construction, bioreactor production, and primary purification), we found that with the microbial host systems the strain construction phase was most significant generating 56% (E. coli) and 72% (P. pastoris) of the manufacturing costs, whereas with the Drosophila S2 system the cell line construction and bioreactor production phases were equally significant (46 and 47% of the total costs, respectively). With different titers and production goal of 100 mg of Nef protein, the costs of P. pastoris and Drosophila S2 systems were about two and four times higher than the respective costs of the E. coli system. When equal titers and bioreactor working volumes (10 L) were assumed for all three systems, the manufacturing costs of the bioreactor production of the P. pastoris and Drosophila S2 systems were about two and 2.5 times higher than the respective costs of the E. coli system. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Photosynthesis and water‐use efficiency: A comparison between invasive (exotic) and non‐invasive (native) species

Abstract Invasive species have been hypothesized to out‐compete natives though either a Jack‐of‐all‐trades strategy, where they are able to utilize resources effectively in unfavourable environments, a master‐of‐some, where resource utilization is greater than its competitors in favourable environments, or a combination of the two (Jack‐and‐master). We examined the invasive strategy of Berberis darwinii in New Zealand compared with four co‐occurring native species by examining germination, seedling survival, photosynthetic characteristics and water‐use efficiency of adult plants, in sun and shade environments. Berberis darwinii seeds germinated more in shady sites than the other natives, but survival was low. In contrast, while germination of B. darwinii was the same as the native species in sunny sites, seedling survival after 18 months was nearly twice that of the all native species. The maximum photosynthetic rate of B. darwinii was nearly double that of all native species in the sun, but was similar among all species in the shade. Other photosynthetic traits (quantum yield and stomatal conductance) did not generally differ between B. darwinii and the native species, regardless of light environment. Berberis darwinii had more positive values of δ¹³C than the four native species, suggesting that it gains more carbon per unit water transpired than the competing native species. These results suggest that the invasion success of B. darwinii may be partially explained by combination of a Jack‐of‐all‐trades scenario of widespread germination with a master‐of‐some scenario through its ability to photosynthesize at higher rates in the sun and, hence, gain a rapid height and biomass advantage over native species in favourable environments.     

Cataclysta lemnata Linnaeus, 1758 (Lepidoptera: Crambidae) expanded its host range feeding on invasive aquatic ferns,species of Azolla Lamarck, 1783 (Hydropteridales: Azollaceae): fitness factors and costs

Cataclysta lemnata Linnaeus, 1758 is a semi-aquatic moth that feeds on Lemnaceae and few of other aquatic plants. In recent years, this moth has been seen feeding on Azolla Lamarck, 1783 Lamarck, J.B. (1783), Encyclopedie methodique: botanique, 1, Paris: Panckouche. 752 pp. [Google Scholar] in Iran in high numbers. The effect of the host plant on preference and performance of the moth was assessed under laboratory conditions. Despite the high survival rate of the young larvae, due to high mortality of the late instars and pupa on Lemna Linnaeus, 1753, the total survival rate on Azolla was higher. Feeding on Azolla increased the development time by almost a week and reduced fertility to half. However, by consuming more food, regulating the egg laying dynamic, and increasing emergence period, the moth retrieved most of the losses and adapted to feed on Azolla. A week before pupation, feeding activity increased between 2 and 8 times in all treatments and on Azolla, the larvae growth rate was slightly higher.