Population dynamics of the Late Devonian conodont Alternognathus calibrated in days

Abstract

Alternognathus is a cavusgnathid conodont believed to be a relative and possible ancestor of the Siphonodella lineage, which is of crucial importance to the biostratigraphy of the Devonian–Carboniferous transition, as well as the Early Carboniferous Clydagnathus, with the most completely known soft tissue anatomy among conodonts. Specimens of Alternognathus from the Kowala quarry in central Poland have their basal cavities lacking any mineralised basal body tissue, exposing rhythmic growth increments of probably daily nature. This enables calibration of ontogeny and population dynamics of Alternognathus in absolute time units and to estimate the correspondence between data derived from isolated oral apparatus elements and the animal body size. The peak of mortality, probably resulting from predation, occurred at 18–28 days of the Alternognathus oral apparatus element secretion and the inferred whole animal length of about 1.6–2.9 cm. Based on analogy with present-day fish, the actual beginning of individual life presumably preceded the initiation of the mineral tissue secretion for about 8 days. This makes the dominant life cycle close to the lunar month length and suggests analogy to cyclic mortality of modern tropical organisms due to full moon light influence on their daily vertical migration.     

Light Response of Seedlings of a Central African Timber Tree Species,Lophira alata (Ochnaceae), and the Definition of Light Requirements

Light is of primary importance in structuring tropical tree communities. Light exposure at seedling and adult stages has been used to characterize the ecological profile of tropical trees, with many implications in forest management and restoration ecology. Most shade‐tolerance classification systems have been proposed based on empirical observations in a specific area and thus result in contradictions among categories assigned to a given species. In this study, we aimed to quantify the light requirements for seedling growth of a Central African timber tree, Lophira alata (Ochnaceae), taking into account effects of population origin. In two controlled experiments: a light response experiment and a comparative population experiment, conducted in southwestern Cameroon, using seeds collected from four populations (three from Cameroon and one from Gabon), we examined the quantitative responses to irradiance of seedlings. After 2 years, mortality was very low (<3%), even in extremely low irradiance. Growth and biomass allocation patterns varied in response to light, with intermediate irradiance (24–43%) providing optimal conditions. Light response differed between populations. The Boumba population in the northeastern edge of the species' distribution exhibited the highest light requirements, suggesting a local adaptation. As a result of positive growth at low irradiance and maximum growth at intermediate irradiance, we concluded that L. alata exhibits characteristics of both non‐pioneer and pioneer species. Implications of our results to propose an objective way to assign the light requirement for tropical tree species are discussed.     

Lineamenti agronomici e selvicolturali della Lucania

Abstract

Agro-sylvicultural aspects of Lucania. In the Basilicata Region one can find many types of natural habitats from the mediterranean « macchia » to the rocky peaks of Monte Pollino. Natural environmental factors greatly condition land utilization and sub-spontaneous plant formations such as forests, opens scrubs, and grazing lands, occupy 49% of the productive land (53% in the Province of Potenza alone): this is a high figure as compared to the one for the whole of southern Italy (37.5%). Forested land is 18% of the total and also this value is higher than the corresponding one for the whole of southern Italy (14.4%). Cereals are the main crops: the economy of Basilicata is therefore mainly based on pastoral-cereals growing activities.

The regional flora is very interesting including as it does several relict and endemic species. The most precious jewel for nature lovers is the over 6000 feet high, richly forested, massif of Pollino where one can find some of the few Italian stands of Pinus leucodermis, and, among the animals, the extremely rare Gypaëtns barbatus, besides what is probably the only Italian autoctonous roe-deer population.

The conservation of so many naturalistic riches does not necessarily clash with the regional economic development.     

Rhodothyrsus, a new genus of Euphorbiaceae from tropical South America

The new genusRhodothyrsus is proposed, based on the AmazonianSenefeldera macrophylla Ducke but also containing another newly described species,Rhodothyrsus hirsutus from northwestern Venezuela. The genus is a member of the tribe Hippomaneae of the Euphorbiaceae and apparently related toSenefeldera, but its closest relationships are still obscure, because the phylogeny of the tribe is poorly known and most of the significant characters ofRhodothyrsus are probably autapomorphies or symplesiomorphies. The restriction to tropical lowland rain forests is rare within the Hippomaneae, and several floral characters, pointing to a specialized pollination possibly by butterflies, are unique in the tribe.     

Morphological variability of black bullhead Ameiurus melas in four non‐native European populations

External morphology in black bullhead Ameiurus melas, a fish species considered to have high invasive potential, was studied in its four non‐native European populations (British, French, Italian and Slovak). The aim of this study was to examine this species' variability in external morphology, including ontogenetic context, and to evaluate its invasive potential. Specimens from all non‐native populations reached smaller body size compared to individuals from native populations. Juvenile A. melas were found to have a relatively uniform body shape regardless of the population's origin, whereas adults developed different phenotypes depending upon location. Specimens from the U.K., Slovak and French populations appeared to be rather similar to each other, whereas the Italian population showed the most distant phenotype. This probably results from the different thermal regime in the Italian habitat. Ameiurus melas from non‐native European populations examined in this study showed some potential to alter the body shape both within and between populations. The phenotypic plasticity of A. melas, however, was not found to be as significant as in other invasive fish species. The results suggest that morphological variability itself is not necessarily essential for invasive success. The invasiveness of A. melas is therefore probably favoured by variations in its life‐history traits and reproduction variables, together with some behavioural traits (e.g. voracious feeding and parental care) rather than by phenotypic plasticity expressed in external morphology.     

A tropical epiphytic orchid uses a low‐light interception strategy in a spatially heterogeneous light environment

Light is considered a non‐limiting factor for vascular epiphytes. Nevertheless, an epiphyte's access to light may be limited by phorophyte shading and the spatio‐temporal environmental patchiness characteristic of epiphytic habitats. We assessed the extent to which potential light interception in Rodriguezia granadensis, an epiphytic orchid, is determined by individual factors (plant size traits and leaf traits), or environmental heterogeneity (light patchiness) within the crown of the phorophyte, or both. We studied 104 adult plants growing on Psidium guajava trees in two habitats with contrasting canopy cover: a dry tropical forest edge, and isolated trees in a pasture. We recorded the number of leaves and the leaf area, the leaf position angles, and the potential exposure of the leaf surface to direct irradiance (silhouette area of the leaf blade), and the potential irradiance incident on each plant. We found the epiphytes experience a highly heterogeneous light environment in the crowns of P. guajava. Nonetheless, R. granadensis plants displayed a common light interception strategy typical of low‐light environments, resembling terrestrial, forest understory plants. Potential exposure of the total leaf surface to direct irradiance correlated positively with plant size and within‐plant variation in leaf orientation. In many‐leaved individuals, within‐plant variation in leaf angles produced complementary leaf positions that enhanced potential light interception. This light interception strategy suggests that, in contrast to current wisdom, enhancing light capture is important for vascular epiphytes in canopies with high spatio‐temporal heterogeneity in light environments.     

Somatic embryogenesis and plant regeneration of tropical maize genotypes

In Latin America and sub-Saharan Africa, tropical maize (Zea mays L.) is a major crop for human consumption. To cope with the increasing population and changing environment, there is a need for improving tropical maize germplasm. As part of a biotechnological approach, efficient in vitro regeneration of two tropical maize inbred lines (CML216 and CML244) was established. A number of parameters were optimized, such as age of the immature embryos, plant media and growth regulator concentration. After 6 weeks of culture, somatic embryos that had already reached the coleoptilar stage produced shoots after light induction and developed into fertile plants after acclimation in the soil. The callus induction frequencies and somatic embryo-derived plantlet formation were higher when cultured with the Linsmaier and Skoog medium than those with the Chu’s N6 basal medium. Regeneration of tropical maize shoots depended on the 2,4-dichlorophenoxyacetic acid (2,4-D) concentration at the callus initiation stage from immature embryos. The recalcitrance of the tropical maize inbred line TL26 to in vitro regeneration was overcome in a single-cross hybrid with the CML216 and CML244 genotypes. Remarkably, tropical maize somatic embryos were formed at the abaxial side of the scutellum facing the medium, probably from the axis of the immature embryos, as shown by histological sections. Upon co-cultivation, agrobacteria transiently expressed their intronless β-glucuronidase-encoding gene at the embryogenic tissue, but not with an intron-containing gene, suggesting that virulence genes are induced in Agrobacterium, but that subsequent steps in the T-DNA transfer are inhibited.     

The relationship between temperature,competition and the potential for colonization of a subtropical pond by Daphnia magna

The role that temperature plays in excluding large daphnid species from subtropical and tropical ponds, and competitive relationships between Daphnia laevis and Daphnia magna, are explored. D. magna, a large temperate species is probably not excluded from subtropical or tropical systems by elevated temperatures. However, D. magna was a poorer competitor, under a restricted set of laboratory conditions, than D. laevis, the only pond dwelling daphnid in subtropical Florida. Competition is proposed as one mechanism that may limit the number of daphnid species in subtropical and tropical ponds and lakes. Reduced environmental fluctuations in subtropical and tropical systems (compared with temperate systems) may allow zooplankton populations to reach an environmental carrying capacity where competition limits the number of similar, coexisting species in a habitat.     

The genus Gymnospermium (Berberidaceae) in Italy: identity and relationships of the populations at the western limit of the genus range

Abstract

Gymnospermium is a small genus of 7–12 taxa subject to diverging taxonomic treatments and distributed from east China to the Balkans. The recent discovery of Gymnospermium in the S-Apennines posed questions about origin and identity. Accordingly, we performed a systematic investigation by means of morphological, karyological and molecular tools. All populations were diploid with 2n = 14 as for the Balkan G. scipetarum (incl. G. maloi), and also morphology suggested a close affinity to the latter. However, the Italian populations differed from typical G. scipetarum by the lower stamen:petal length and style:carpel length. By including all European and most Asian taxa in a phylogenetic analysis, we shed new light into the species-level relationships in this genus. In the combined ITS-trnL-F phylogeny, two major clades were retrieved. One included the central Asian and eastern European taxa plus the Greek endemic G. peloponnesiacum sister to G. odessanum, and one the Balkan and Apennine populations. Such findings further corroborated that the Apennine plant belong to G. scipetarum. The native status of the Italian population is supported by exclusive SNPs in both ITS1 and trnL-F sequences. Along with morphological evidence, this allows to refer it to the new subspecies G. scipetarum subsp. eddae.     

Nothotalisia, a new genus of Picramniaceae from tropical America

A new genus of Picramniaceae from tropical America, Nothotalisia, is described. Of the three species in the genus, N. piranii and N. cancellata, are new to science. The third, N. peruviana, was originally described as Talisia peruviana in the Sapindaceae. The genus and all three species are described, illustrated, and distinguished by means of a key.     

Three new species of Lysipomia (Lobeliaceae) endemic to the páramos of southern Ecuador

Three species of Lysipomia, L. caespitosa, L. cylindrocarpa, and L. speciosa, from a tropical alpine ecosystem called páramo, are described, illustrated, and compared to related species. Notes on morphology, especially floral presentation, and general ecology are given where possible. A published key to the species in Ecuador is revised to include the three new species plus L. multiflora McVaugh, a species previously known only from northern Peru.     

Taxonomic revision of the Koeleria splendens C. Presl group (Poaceae) in Italy based on morphological characters

Abstract

The Italian populations of Koeleria splendens C. Presl, critical group of the Mediterranean flora, are examined from the taxonomic and nomenclatural viewpoints. On the basis of literature data, herbarium investigations and field surveys, many morphologically well-differentiated taxa have been recognized. This group is widespread in the Italian peninsula and Sicily, where it is represented by the following units: K. splendens C. Presl, with four subspecies [subsp. splendens, subsp. grandiflora (Bertol. ex Schultes) Domin, subsp. brutia Brullo, Gangale & Uzunov, and subsp. ophiolitica subsp. nova], K. lucana sp. nova, K. subcaudata (Ascherson & Graebner) Ujhelyi, K. australis Kerner, K. callieri (Domin) Ujhelyi, and K. insubrica sp. nova. As concerns their distribution, both K. splendens and K. lucana are endemic to the Italian territory, while the other species occur also in some eastern Mediterranean countries. The taxonomic position of K. lobata, recently treated by some authors as a synonym of K. splendens, is also examined. A phylogenetic analysis was performed using morphological characters. Finally, a detailed iconography of the main morphological features and an analytical key of the Italian taxa (K. lobata included) are given.     

LEAF DISPLAY,CANOPY STRUCTURE,AND LIGHT INTERCEPTION OF TWO UNDERSTORY PALM SPECIES

The implications of leaf size, leaf display, and crown size for whole-plant light interception were investigated in Geonoma cuneata and Asterogyne martiana, two understory palm species native to Central American rain forests. Adults of A. martiana had longer leaves, more leaves per plant, and greater total leaf area than G. cuneata adults. Geometric measurements within whole crowns were used to calculate light interception efficiency, a leaf-based measure of the proportion of total incident light that is intercepted by a crown. Light interception efficiency was higher in adult G. cuneata than in adult A. martiana; seedlings of the two species did not differ significantly in light interception efficiency. Decreased efficiency of adult A. martiana crowns was largely due to an increased proportion of pendent leaves. Compared to G. cuneata, adults of A. martiana had greater light interception capacity (the product of light interception efficiency and total leaf area), but they also had higher biomass costs of light interception. Lower biomass costs of light interception in adult G. cuneata enable this species to exploit successfully the most deeply shaded microsites in the rain forest understory.     

Defensive strategies in planktonic coelenterates

Some planktonic coelenterates respond to potentially harmful stimulation by protective involution, others by escape behaviour. Examples of protective involution are seen in the ‘crumpling’ behaviour of various hydrome‐dusae (Sarsia, Euphysa) and of siphonophores such as Hippopodius. Involution may be accompanied by striking visual displays e.g. light emission in Euphysa, light emission and blanching in Hippopodius. These displays probably serve to startle or blind interlopers. In Hippopodius, light emission in the dark would have the same effect as blanching in the light, an example of behavioural self‐mimicry.

Animals employing escape locomotion include the ctenophore Euplokamis, the siphonophore Nanomia and the rhopalonematid medusa Aglantha. All of these forms have evolved giant axons that facilitate escape by reducing response time. The central nervous circuitry underlying locomotion in Aglantha is reviewed.

In a few cases (e.g. Aglantha and possibly Nanomia), the responses described can be seen as defensive against predators, but in the majority of cases, the responses probably serve primarily to reduce the risk of damage due to accidental contact with other organisms.     

Synopsis of the tribe Bocageeae (Annonaceae), with revisions of Cardiopetalum,Froesiodendron, Trigynaea,Bocagea, and Hornschuchia

The tribal name Bocageeae Endlicher is reestablished and the tribe is circumscribed on the basis of solitary internodal ebracteate pedicels that are articulated at the base, and pollen shed in polyads of eight or more grains. Septate anther locules, large pollen size, and seed appendages are prevalent in the tribe. Intectate pollen with free-standing columellae, rare in Annonaceae, occurs not only in the genusTrigynaea but also in some species ofBocagea andHornschuchia. As defined here, the Bocageeae include seven neotropical genera:Cymbopetalum, Porcelia, Bocagea, Cardiopetalum, Froesiodendron, Hornschuchia, andTrigynaea. The latter five genera are revised and the treatments include ten new species:Cardiopetalum plicatum, Froesiodendron urceocalyx, Hornschuchia lianarum, H. santosii, H. leptandra, Trigynaea cinnamomea, T. lanceipetala, T. triplinervis, T. lagaropoda, andT. axilliflora, all from tropical South America. A new combination,Froesiodendron longicuspe, changes the rank of that taxon from subspecies to species.Cardiopetalum surinamense is removed fromFroesiodendron and reassigned toCardiopetalum on the basis of its connate petals, dehiscent monocarps, and seeds with bilobed arils. A cladogram provides an explicit hypothesis of intergeneric relationships in the tribe. The new combinationOnychopetalum periquino, based onTrigynaea periquino, is made.     

Patterns and origin of intraspecific functional variability in a tropical alpine species along an altitudinal gradient

Background : Intraspecific functional variability (IFV) along altitudinal gradients is a powerful proxy to infer the responses of plants to abrupt environmental changes. We envisage that IFV shows distinctive patterns in tropical and extratropical alpine regions.

Aims : To characterise the patterns and explore the origin of IFV in a tropical alpine species in a context of upward range extension.

Methods : We examined variations in a series of plant functional traits in Lasiocephalus ovatus, inside and outside a nurse plant along a 600 m altitudinal gradient in the Ecuadorian Andes, and we studied its genetic variability.

Results : More conservative traits were developed at higher elevation, in contrast to extratropical alpine plants, which commonly develop opportunistic traits in response to late snowmelt close to their upper altitudinal limit. The presence of nurse cushions did not alter this trend. Increasing genetic distance along the gradient suggested that IFV might be partly genetically induced.

Conclusions : Our data combined with existing literature in tropical alpine environments lead the way to a stimulating scientific challenge: determining if patterns of plant altitudinal distribution in tropical alpine areas in response to climate change are predictable from patterns described in extratropical alpine areas.     

Photosynthetically active radiation and carbon gain drives the southern orientation of Myrtillocactus geometrizans fruits

• The equatorial orientation of reproductive structures is known in some columnar cacti from extratropical deserts. It has been hypothesised that photosynthetically active radiation (PAR) interception is the main reason for this orientation, because of its key effect on nocturnal CO₂ uptake. However, there are no studies addressing both the effect of PAR and its consequence, carbon gain, on fruit orientation. Accordingly, we tested whether PAR and carbon gain could explain the southern fruit orientation of Myrtillocactus geometrizans, an inter‐tropical columnar cactus.
• We studied three populations of M. geometrizans in Mexico. For each population, azimuth of fruits, total daily PAR, nocturnal acid accumulation (NAA) and fruit production were measured. The relationships between rib orientation and number of fruits, as well as total daily PAR, were evaluated using periodic regressions. The effect of total daily PAR and NAA on number of fruits was assessed using generalised linear models.
• During spring, mean fruit orientation had a south azimuth for three populations. Likewise, rib orientation had a significant effect on fruit production, with the south‐facing ribs having the maximum number of fruits. Total daily PAR was highest in the south‐facing ribs, at least for those in the northern and central populations. Furthermore, during spring, there was a significant positive effect of total daily PAR and NAA on fruit production.
• Our results provide strong evidence that the higher carbon gain in equatorial ribs, through a highest interception of PAR, would be the responsible factor for equatorial orientation of fruits in an inter‐tropical columnar cactus.

     

Status,mortality, and movements of grey teal (Anas gibberifrons) in New Zealand

Grey teal (Anas gibberifrons gracilis Buller, 1869) are widely distributed in New Zealand, the greatest concentrations occurring in the South Auckland, Waikato, Hawke's Bay, and Otago districts. Their preferred habitat is shallow freshwater lakes, lagoons, and swamps with extensive marginal cover. The New Zealand population is estimated to be less than 20 000. Grey teal disperse widely in all directions, in some instances for long distances. The composition of flocks changes continually, and pair‐bonds are apparently retained from season to season. There is an almost complete turnover of the population every 4 years. The survival of juveniles in the post‐fledging period is higher for heavier than for light‐weight young. Mortality from hunting is probably additional to the mortality from other causes.     

LEAF DEVELOPMENT AND CROWN GEOMETRY OF TWO IRIARTEOID PALMS

We examined changes in pinnately compound leaf morphology and crown geometry that occur during height growth of the iriarteoid palms Socratea exorrhiza and Iriartea deltoidea in tropical wet forest of Costa Rica. Although light availability increased with height, the number of leaves per plant was relatively constant. Total leaf area, however, was much larger in taller individuals. Increases in linear dimensions of leaves (length and width) was responsible for less than half of this greater surface area. More important was the transition from a basically dorsiventral display of leaflets in small individuals to a more radial display in taller plants. Production of leaflets in more than one plane resulted in leaves whose surface area was more than twice the horizontally projected area and whose lateral light interception was greatly enhanced. S. exorrhiza, a faster-growing and more light-demanding species, undergoes this transformation in leaf morphology at heights between 3 and 6 m; whereas in the slower-growing and more shade-tolerant I. deltoidea this occurs at heights between 10 and 20 m. Pinnate leaves, with dense radial packing of leaflets along the rachis, are functionally comparable to branches of dicotyledonous trees and may have been important for the evolution of arborescence in palms.     

Light capture efficiency decreases with increasing tree age and size in the southern hemisphere gymnosperm Agathis australis

We investigated leaf and shoot architecture in relation to growth irradiance (Q_int) in young and mature trees of a New Zealand native gymnosperm Agathis australis (D. Don) Lindl. to determine tree size-dependent and age-dependent controls on light interception efficiency. A binomial 3-D turbid medium model was constructed to distinguish between differences in shoot light interception efficiency due to variations in leaf area density, angular distribution and leaf aggregation. Because of the positive effect of light on leaf dry mass per area (M_A), nitrogen content per area (N_A) increased with increasing irradiance in both young and mature trees. At a common irradiance, N_A, M_A and the components of M_A, density and thickness, were larger in mature trees, indicating a greater accumulation of photosynthetic biomass per unit area, but also a larger fraction of support biomass in older trees. In both young and mature trees, shoot inclination angle relative to horizontal, and leaf number per unit stem length decreased, and silhouette to total leaf area ratio (S_S) increased with decreasing irradiance, demonstrating more efficient light harvesting in low light. The shoots of young trees were more horizontal and less densely leafed with a larger S_S than those of mature trees, signifying greater light interception efficiency in young plants. Superior light harvesting in young trees resulted from more planar leaf arrangement and less clumped foliage. These results suggest that the age-dependent and/or size-dependent decreases in stand productivity may partly result from reduced light interception efficiency in larger mature relative to smaller and younger plants.