Effects of fire frequency on oak litter decomposition and nitrogen dynamics

Rapid speciation within some plant families has been attributed to the evolution of floral spurs and to the effect of spur length on plant reproductive success. The flowers of Impatiens capensis (jewelweed) possess a long, curved spur in which nectar is produced and stored. Spur length and curvature varies among plants within one population. Here I document that spur shape is variable in natural populations, variation within plants is less than variation among plants, and spur shape is correlated with components of female and male reproductive success. The apparent natural selection is weakly directional in 1 of 2 years, with greatest seed production and pollen removal occurring in flowers with the greatest spur curvature. Bee pollinator visit length is longest at flowers with highly curved spurs, and they leave less nectar in these spurs than in flowers with straighter spurs. Spur angle evolution may be limited, at least in part, by opposing selection by nectar-robbers who prefer to visit flowers with greater spur curvature. Other factors that might contribute to the maintenance of spur angle variation are temporal variation in the strength of selection and potential genetic correlations of spur shape with other traits under selection.     

An examination of nectar production in 34 species of Dendrobium indicates that deceptive pollination in the orchids is not popular

Nectar, the most common floral reward, is generally used to determine whether an orchid species involves deceptive pollination. Estimates of the deceptive pollination systems with nectarless flowers have ranged from one quarter to one third of the nearly 30 000 species of orchids. These estimates, however, are biased towards temperate-zone, usually terrestrial, orchids. Here we investigated nectar production and property in 34 epiphytic orchid species of the Southeast Asian genus Dendrobium. Twenty-one species were observed producing nectar. The amount and sugar concentration (in bagged flowers) of 12 species varied from 0.45 to 2.78 μL and from 8.1% to 31.1%. The nectar was sucrose-dominant, typical of bee-pollinated flowers. Reconstruction of phylogenetic relationship indicated that transition of nectar secretion occurred in the genus. Spur length was positively correlated with flower size but species with relatively long spurs tended to produce small volume of nectar. Nectar production was strikingly variable among and within individuals in some species, suggesting that a vital measurement of bagged and fresh flowers is needed. Given that the quantitative measurement of nectar or floral reward in orchid species remains scarce, an estimate of deceptive pollination systems awaits further survey in diverse genera.     

Does the Platanthera dilatata (Orchidaceae) complex contain cryptic species or continuously variable populations?

Floral phenotypic traits are expected to reflect evolutionary changes and are used as a reliable basis for species delimitation. However, when traits overlap among populations of newly emerging species, this confounds identification of evolutionarily distinct lineages and reduces taxonomic stability. In this study, we quantified variation in ten floral traits and plastid DNA sequences across 26 populations of Platanthera dilatata (Orchidaceae) in North America to determine geographic structure among populations and to evaluate support for three varieties recognized in the current taxonomy. k-means clustering analysis, in the absence of a priori designation of groups, indicated two morphologically distinct groups. Spur length was the most distinctive character between groups. The group containing larger flowers with longer spurs corresponds to the var. leucostachys and most samples in this group are from western North America. The vars. albiflora and dilatata could not be distinguished within the second group, which exhibited flowers with short to intermediate spurs and include samples from eastern and western North America. Morphological variation in P. dilatata may reflect pollinator-mediated selection, particularly in spur length, which is known to vary in association with pollinators across Platanthera. Significant genetic divergence was observed between the two groups (F _ST = 0.15; P ≤ 0.001), but we did not find corresponding phylogenetic structure, which may reflect recent divergence and retention of ancestral polymorphisms. Based on these results, we suggest preserving the current intraspecific taxonomy until further studies determine the origin of floral variation and the extent of gene flow between morphologically divergent populations.     

The relationship between cell division and elongation during development of the nectar-yielding petal spur in Centranthus ruber (Valerianaceae)

Background and Aims Floral spurs are hollow, tubular outgrowths that typically conceal nectar. By their involvement in specialized pollinator interactions, spurs have ecological and evolutionary significance, often leading to speciation. Despite their importance and diversity in shape and size among angiosperm taxa, detailed investigations of the mechanism of spur development have been conducted only recently.Methods Initiation and growth of the nectar-yielding petal spur of Centranthus ruber ‘Snowcloud’ was investigated throughout seven stages, based on bud size and developmental events. The determination of the frequency of cell division, quantified for the first time in spurs, was conducted by confocal microscopy following 4'',6-diamidino-2-phenylindole (DAPI) staining of mitotic figures. Moreover, using scanning electron microscospy of the outer petal spur surface unobstructed by trichomes, morphometry of epidermal cells was determined throughout development in order to understand the ontogeny of this elongate, hollow tube.Key Results Spur growth from the corolla base initially included diffuse cell divisions identified among epidermal cells as the spur progressed through its early stages. However, cell divisions clearly diminished before a petal spur attained 30 % of its final length of 4·5 mm. Thereafter until anthesis, elongation of individual cells was primarily responsible for the spur’s own extension. Consequently, a prolonged period of anisotropy, wherein epidermal cells elongated almost uniformly in all regions along the petal spur’s longitudinal axis, contributed principally to the spur’s mature length.Conclusions This research demonstrates that anisotropic growth of epidermal cells – in the same orientation as spur elongation – chiefly explains petal spur extension in C. ruber. Representing the inaugural investigation of the cellular basis for spur ontogeny within the Euasterids II clade, this study complements the patterns in Aquilegia species (order Ranunculales, Eudicots) and Linaria vulgaris (order Lamiales, Euasterids I), thereby suggesting the existence of a common underlying mechanism for petal spur ontogeny in disparate dicot lineages.     

Size-related habitat use and schooling behavior in two species of surgeonfish (Acanthurus bahianus and A. coeruleus) on a fringing reef in Barbados, West Indies

Surgeonfish (Acanthuridae) are prominent, herbivorous members of coral reef communities that occur as dispersed individuals and small, loose groups ('non-schooling fish') or as members of large, highly aggregated, mixed-species schools ('schooling fish'). We examined the relationships among fish size, habitat use and schooling in two species of surgeonfish on a fringing reef in Barbados, West Indies. Both ocean surgeonfish, Acanthurus bahianus, and blue tangs, A. coeruleus, appeared to show ontogenetic habitat shifts. The density of juvenile ocean surgeonfish was highest in the back reef (inshore), lower on the reef crest (intermediate) and lowest in the spurs and grooves (offshore) zone, but schooling adults were most abundant in the spurs and grooves zone. In a multiple regression considering the effects of depth, algal cover, rugosity and distance from shore, the density of non-schooling ocean surgeonfish was positively associated with percent algal cover on the substratum and negatively with distance from shore. Newly settled blue tangs occurred only in the reef crest and spurs and grooves zones, but larger juveniles were more common in the back reef, while adults were more evenly distributed across zones. The density of non-schooling blue tang was positively associated with rugosity, distance from shore, and percent algal cover. In both species, schooling occurred primarily in adults; small juveniles never participated in the large, dense schools. The proportion of adults that were schooling increased from the back reef to the reef crest to the spurs and grooves zone. These results are consistent with the hypothesis that schooling permits adult surgeonfish access to higher quality food in the territories of damselfish (Pomacentridae) that predominate on the reef crest and spurs.     

Are spurred cyathia a key innovation? Molecular systematics and trait evolution in the slipper spurges (Pedilanthus clade: Euphorbia, Euphorbiaceae)

The study of traits that play a key role in promoting diversification is central to evolutionary biology. Floral nectar spurs are among the few plant traits that correlate with an enhanced rate of diversification, supporting the claim that they are key innovations. Slight changes in spur morphology could confer some degree of premating isolation, explaining why clades with spurs tend to include more species than their spurless close relatives. We explored whether the cyathial nectar spur of the Pedilanthus clade (Euphorbia) may also function as a key innovation. We estimated the phylogeny of the Pedilanthus clade using one plastid (matK) and three nuclear regions (ITS and two G3pdh loci) and used our results and a Yule model of diversification to test the hypothesis that the cyathial spur correlates with an increased diversification rate. We found a lack of statistical support for the key innovation hypothesis unless specific assumptions regarding the phylogeny apply. However, the young age (hence small size) of the group may limit our ability to detect a significant increase in diversification rate. Additionally, our results confirm previous species designations, indicate higher homoplasy in cyathial than in vegetative features, and suggest a possible Central American origin of the group.     

Towards a diagnostic view of Hyalomma (Hyalomma) aegyptium (Acari,Ixodidae)

The diagnostic characters of larval, nymphal and adult Hyalomma aegyptium (L., 1758) based on specimens from the territory of most part of the area are given. In the diagnoses of immature stages, was used the characters, which were formerly tested by the author for diagnostics of other Hyalomma species occurring in the former USSR. Commonly used characters and those which were revealed by the author as useful for the majority of Euhyalomma Filippova, 1984 and Hyalommina Schulze, 1919 species, have been used in the diagnoses of male and female. Differential diagnosis of Hyalomma aegyptium. Female: genital orifice as wide arch with straight posterior margin (fig. 2, 5); vestibular part of vagina funnel-like, greatly swollen (fig. 2, 5); setae of alloscutum stick-like, tapering in apical one (figs 2, 3, 4); second segment of palps with proximal narrowing (figs 3, 1, 2); spurs of coxae I widely separated, triangular, wide, subequal in size (fig. 3, 5). Male: any grooves of conscutum absent, except short and pit-like cervical ones (fig. 4); punctation sparce and impressive (fig. 4); adenal shields short and wide, without inner branch, posterior part widened, anteromedian margin straight (fig. 5, 4); spurs of coxae I widely separated, triangular, wide, subequal in size (fig. 6, 5). Nymph: posteromedian setae of alloscutum stick-like and, as a rule, with indented apices (fig. 7, 2); spurs of coxae I large, median spur as equilateral triangle and shorter than lateral one (fig. 7, 8); spurs of coxae II-IV well developed, with acute apices (fig. 7, 8). Larva: posterior part of scutum (behind the eyes) heavy elongated, its apex straight, postero-lateral incisions weakly developed (fig. 8, 1); spurs of coxae I as equilateral triangle in shape and with rounded apices, spurs of coxae II-III very large (fig. 8, 5).     

Patterns of fluctuating asymmetry in sexual ornaments predict female choice

Extravagant secondary sexual characters are assumed to have arisen and be maintained by sexual selection. While traits like horns, antlers and spurs can be ascribed to intrasexual competition, other traits such as extravagant feather ornaments, displays and pheromones have to be ascribed to mate choice. A number of studies have tested whether females exert selection on the size of male ornaments, but only some of these have recorded female preferences for the most extravagantly ornamented males. Here I demonstrate that female choice can be directly predicted from the relationship between the degree of fluctuating asymmetry and the size of a secondary sexual character. Fluctuating asymmetry is an epigenetic measure of the ability of individuals to cope with stress, and it occurs when an individual is unable to undergo identical development of an otherwise bilaterally symmetric trait on both sides of its body. There is a negative relationship between the degree of fluctuating asymmetry and the absolute size of an ornament in those bird species with a female preference for the largest male sex trait, while there is a flat or U-shaped relationship among species without a female preference. These results suggest that females prefer exaggerated secondary sexual characters if they reliably demonstrate the ability of males to cope with genetic and environmental stress. Some species may demonstrate a flat or U-shaped relationship between the degree of fluctuating asymmetry and the absolute size of an ornament because (i) the genetic variance in viability signalled by the secondary sex trait has been depleted; (ii) the secondary sex trait is not particularly costly and therefore does not demonstrate condition dependence; or because (iii) the sex traits can be considered arbitrary traits rather than characters reflecting good genes.     

Biology of a "babysitting" symbiosis in brittle stars: analysis of the interactions between Ophiomastix venosa and Ophiocoma scolopendrina

Abstract. "Babysitting" symbioses between brittle star species involve juveniles of one species and adults of another. During this phenomenon, reported from many localities in the Indo-Pacific Ocean, juveniles are attached to the disk or lie in the bursa of the adults. The symbiosis between members of Ophiomastix venosa and their host, Ophiocoma scolopendrina , was investigated on the Great Barrier Reef of Toliara (Madagascar) during a 14-month period. The population of O. scolopendrina only occurs on rocky spurs that frequently emerge at low tide, while the population of O. venosa lies in adjacent surge channels that are always immersed. Only juveniles of O. venosa associated with adults of O. scolopendrina may occur on the rocky spurs. Analyses conducted on the populations of the two species showed that (1) the symbiosis is facultative and that symbiotic juveniles migrate into the channels when they reach a disc diameter of 6 mm, and (2) recruitment in the channels occurs in April. Host choice experiments, Y-tube experiments, and experiments assessing the resistance of the ophiuroids to air-drying were conducted in the laboratory. The experiments clearly demonstrated that (1) symbiotic juveniles of O. venosa specifically recognize adults of O. scolopendrina , while free juveniles of the same size do not, and (2) juveniles of O. venosa would not survive air-drying conditions similar to those observed on the spurs at low tides if they were not in symbiosis with adults of O. scolopendrina .     

Floral specialization for different pollinators and divergent use of the same pollinator among co‐occurring Impatiens species (Balsaminaceae) from Southeast Asia

Floral variation among closely related species is thought to often reflect differences in pollination systems. Flowers of the large genus Impatiens are characterized by extensive variation in colour, shape and size and in anther and stigma positioning, but studies of their pollination ecology are scarce and most lack a comparative context. Consequently, the function of floral diversity in Impatiens remains enigmatic. This study documents floral variation and pollination of seven co‐occurring Impatiens spp. in the Southeast Asian diversity hotspot. To assess whether floral trait variation reflects specialization for different pollination systems, we tested whether species depend on pollinators for reproduction, identified animals that visit flowers, determined whether these visitors play a role in pollination and quantified and compared key floral traits, including floral dimensions and nectar characteristics. Experimental exclusion of insects decreased fruit and seed set significantly for all species except I. muscicola, which also received almost no visits from animals. Most species received visits from several animals, including bees, birds, butterflies and hawkmoths, only a subset of which were effective pollinators. Impatiens psittacina, I. kerriae, I. racemosa and I. daraneenae were pollinated by bees, primarily Bombus haemorrhoidalis. Impatiens chiangdaoensis and I. santisukii had bimodal pollination systems which combined bee and lepidopteran pollination. Floral traits differed significantly among species with different pollination systems. Autogamous flowers were small and spurless, and did not produce nectar; bee‐pollinated flowers had short spurs and large floral chambers with a wide entrance; and bimodally bee‐ and lepidopteran‐pollinated species had long spurs and a small floral chamber with a narrow entrance. Nectar‐producing species with different pollination systems did not differ in nectar volume and sugar concentration. Despite the high frequency of bee pollination in co‐occurring species, individuals with a morphology suggestive of hybrid origin were rare. Variation in floral architecture, including various forms of corolla asymmetry, facilitates distinct, species‐specific pollen‐placement on visiting bees. Our results show that floral morphological diversity among Impatiens spp. is associated with both differences in functional pollinator groups and divergent use of the same pollinator. Non‐homologous mechanisms of floral asymmetry are consistent with repeated independent evolution, suggesting that competitive interactions among species with the same pollination system have been an important driver of floral variation among Impatiens spp.     

Mating system correlates of tarsal spurs in the Phasianidae

Two methods for the analysis of cross-species data are used to investigate whether tarsal spur length or number are correlated with mating system in three phasianid subfamilies. One method, the phylogenetic regression. suggests that polygamous species have relatively longer and fewer spurs than monogamous species. hut this relationship is not found when a matched-pairwise comparison is used. These ambiguous results suggest that at the moment it is not possible to conclude either way whether spurs are under any selective pressure related to mating system, and that previously published conclusions are not supported.     

Description of three new species of Ixodes Latreille, 1795 (Acari: Ixodidae), parasites of tenrecs (Afrotheria: Tenrecidae) on Madagascar

Ixodes soarimalalae n. sp., Ixodes uilenbergi n. sp. and Ixodes uncus n. sp. (Acari: Ixodidae), are described based on females ex various species of tenrecs (Afrosoricida: Tenrecidae) from Madagascar. Females of all of these new species are similar to those of other species of the subgenus Afrixodes Morel, 1966 known from Madagascar, from which they can be distinguished and from one other by the size of scutum, size of scutal setae, shape of alloscutal setae, shape of genital aperture, development of genital apron, size of auriculae, size of anterior angle of basis capituli, size of palpi, dental formula on hypostome and size and development of spurs on coxa I.

     

Physicochemical and immunological properties of myosin light chains from the ordinary muscle of marine teleost fishes

1. Myosin light chains (A1, A2 and DTNB light chain) were isolated from the ordinary muscle of six marine fishes and the physicochemical and immunological properties were examined. 2. All the isolated light chains were rich in aspartic and glutamic acids, alanine and lysine, but poor in histidine and tyrosine. The contents of alanine, proline and lysine were generally higher in A1 than in A2. Between closely related species such as skipjack and bonito, the amino acid profiles of corresponding light chains were very similar to each other. 3. Structural similarity and difference of A1 light chain were further demonstrated immunologically using anti-A1 antiserum. Precipitation lines were fused with each other among closely related species, whereas strong spurs were observed among phylogenetically distinct species.     

Hawkmoth pollination of aerangoid orchids in Kenya, with special reference to nectar sugar concentration gradients in the floral spurs

The African orchid flora has a high proportion of species with long-spurred white flowers. Few data exist to test the prediction that this floral syndrome pattern reflects an important role for hawkmoth pollination in the evolution and ecology of these orchids. The pollination biology of five aerangoid orchid species (Rangaeris amaniensis, Aerangis brachycarpa, A. confusa, A. thomsonii, and A. kotschyana) was investigated in Kenya. Four of these have long spurs (>10 cm) and were pollinated by Agrius convolvuli and Coelonia fulvinotata. Aerangis confusa, which has relatively short spurs (ca. 4 cm), was pollinated by the short-tongued hawkmoths Hippotion celerio and Daphnis nerii. Nectar frequently filled the entire spur in some of the study species, even at anthesis. Sugar concentration of the nectar of four species was found to vary from ca. 1% at the mouth of the spur to 20% at the tip. Gradients were expressed more strongly in species with long, straight spurs. Species with spirally twisted spurs showed both steep and shallow nectar gradients. These gradients, previously unknown in plants, may function as a "sugar trail," enticing long-tongued hawkmoths to probe deeply into spurs without incurring the cost of filling an entire spur with concentrated nectar. In addition, the most concentrated nectar is kept out of reach of short-tongued pollinators.     

Comparison of stochastic and deterministic methods for modeling spur kinetics

Stochastic and deterministic kinetic methods have been used to model the temporal evolution of spatially nonhomogeneous clusters of reactants resulting from the dissociation of one to six water molecules into either H3O+, OH, and e-aq, or H atoms and OH radicals. When the ionic fragmentation initially producing H3O+, OH, and e-aq is considered, the stochastic and deterministic methods predict similar time dependences for the decay of the reactive species; however, the two methods suggest very different product yields. For a two-dissociation spur, the deterministic treatment overestimates both the H2 and the H2O2 yields by about 70%. The error decreases to less than 15% for a spur with six water dissociations. For a distribution of spurs representing a high-energy electron track, the differences in the predicted yields of reactants are less than 6% at 0.1 microseconds, but the stochastic and deterministic predictions for the yields of H2 and H2O2 differ by about 50%. The kinetics of spurs produced by the fragmentation of water to H atom and OH radical shows discrepancies in both the reactant and the product yields. The size of the discrepancy decreases as the number of H/OH pairs increases, and the predictions of the two techniques are almost the same for clusters of six water dissociations.     

Hyalomma (Hyalommina) arabica: nymphal and larval identity and spiny mouse hosts in Saudi Arabia (Acarina: Ixodoidea: Ixodidae)

Nymphal and larval Hyalomma (Hyalommina) arabica Pegram, Hoogstraal, and Wassef, 1982, described herein, closely resemble those of Hyalomma (Hyalommina) rhipicephaloides Neumann, differing chiefly in body size (both stages), nymphal basis capituli and scutal proportional dimensions, and distinctness of larval coxal spurs. Females of these species are also structurally similar but males differ in major critical characters. Nymphs and larvae of both species parasitize the spiny mouse (Acomys spp.), but immatures of the third African- Arabian species of this subgenus, Hyalomma (Hyalommina) punt Hoogstraal, Kaiser, and Pedersen, are unknown. Hyalomma (Hyalommina) arabica occurs in valleys and hills of western Saudi Arabia and western Yemen; H. (H.) rhipicephaloides in the Red Sea and Dead Sea areas; and H. (H.) punt in northeastern Somalia and eastern Ethiopia. The ibex (Capra ibex nubiana Cuvier) is probably the original host of adult H. (H.) arabica and H. (H.) rhipicephaloides; the related domestic goat is an important host of adults of the 3 species, which also parasitize domestic sheep. Gazelles are recorded hosts of adults of H. (H.) rhipicephaloides and H. (H.) punt and the latter is also recorded from goats, sheep, camels and cattle.     

Stamen development in the Ericaceae. I. Anther wall, microsporogenesis, inversion, and appendages

Development of the introrse, tetrasporangiate, and normally dorsifixed and poricidal stamens has been studied at the gross morphological and cellular level in ten species of Ericaceae. Microsporogenesis, followed in four species, is normal, with cytokinesis simultaneous, forming tetrahedral tetrads. The tricolp(or)ate pollen is shed as permanent tetrads with each segment two-celled except in Enkianthus in which pollen grains are three-celled monads. Anther-wall development is similar in all four species initially, but no regular pattern of wall development could be recognized thereafter. The tapetum, of parietal origin, is binucleate, glandular, and mainly uniseriate. Viscin threads occur with the tetrads in the three rhododendroid species. A well-developed endothecium appears only in Enkianthus.Soon after stamen initiation, anthers of nine species invert at the eventual filament-anther junction to become introrse; in Enkianthus inversion occurs close to anthesis. Microsporogenesis starts during early inversion; greater cell elongation on the abaxial side of the young anther completes inversion by the late sporogenous-tissue stage. In Erica and, to a lesser extent Calluna, inversion results from greater abaxial than adaxial increase in cell number and length just above the filament-anther junction. The single vascular strand reflects the degree of inversion. Stamens of six species are appendaged; three have only awns, two only spurs, while one has both. Appendages arise from residual meristems after inversion is completed (or almost so) in all except Enkianthus. Awns develop at what will be the apex at maturity of each anther half. Their length and orientation vary among species. Only in Vaccinium do the awns become hollow (tubules). Spurs, varying in length, shape, and size, arise on the abaxial side from the filament, connective, or thecae.     

Pollination and resource limitation as interacting constraints on almond fruit set

• Pollination and resource availability are factors determining reproductive success of plants, and in agriculture these factors influence yield of fruit‐bearing crops. Our understanding of the importance of crop pollination is fast improving, but less is known about how the interaction between pollination and resources constrains fruit production.
• We conducted an experiment with almond trees (Prunus dulcis) to examine how the number of flowers, light availability and competition for resources affected nut (fruit) production on individual spurs (fruit‐bearing structures) exposed to open‐pollination or hand‐pollination.
• We found a positive relationship between flower number and nut number on spurs with up to four flowers, but no further benefit after four flowers, suggesting a resource threshold expressed by individual spurs. Spurs with few flowers increased the conversion rate of flowers to nuts when supplemented with hand‐pollination, but spurs with more flowers were more likely to achieve the threshold number of nuts even under open‐pollination. Our experiment included a further treatment involving spraying whole trees with pollen. This treatment reduced nut production by spurs with many flowers and high light availability, suggesting competition is experienced by well‐resourced spurs when resources need to be shared among developing nuts across the whole tree.
• Our study supports the hypothesis that excess flower production in fruit trees increases the potential for fruit production when pollinator and resource availability is variable (bet‐hedging). Spurs with more flowers typically produce more nuts (within a limited range), but only if both resources and pollen supply increase with flower number. For almond growers, a focus on maintaining high flower numbers, especially in high light regions of the canopy, is the foundation for high levels of production. Strategies to lift flower number and light are complicated by trade‐offs inherent in tree architecture and orchard design. However, fruit set would be lifted above that achieved by current practice by an increase in the pollination rate of flowers.