STUDIES IN THE QUERCUS UNDULATA COMPLEX. IV. THE CONTRIBUTION OF QUERCUS HAVARDII

Scrub oak populations in the semidesert area of northeastern Arizona and southeastern Utah are ordinarily identified in regional manuals as Quercus undulata. They are very similar, both morphologically and ecologically, to Q. havardii of the Staked Plain of the Texas Panhandle and southeastern New Mexico. They differ, however, in a number of inconspicuous characters. Population sample analyses indicate that most of these differences are suggestive of Q. gambelii, and the deviant populations are thus interpreted as having been derived from ancestral Q. havardii through introgression by Q. gambelii. Two differences are not in accord with this interpretation; these are regarded as possible cases of transgressive segregation. Considering the evolution of these hybridized populations, it is speculated that the ancestral Q. havardii occurred to the south and west of the present range of this species during the Kansan period of the Pleistocene. During subsequent northward dispersal, it became split in two. The eastern portion ultimately came to occupy the present range of the species in the Staked Plain; the western portion—lying to the west of a north-south mountain barrier in central New Mexico—became introgressed by Q. gambelii (and locally by Q. turbinella), resulting in the present populations of Arizona and Utah.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX. II. THE CONTRIBUTION OF QUERCUS TURBINELLA

Tucker , J. M. (U. California, Davis), W. P. Cottam , and R. Drobnick . Studies in the Quercus undulata complex. II. The contribution of Quercus turbinella. Amer. Jour. Bot. 48(4): 329–339. Illus. 1961.—Quercus undulata has been interpreted as a hybrid complex involving Q. gambelii and several other species, including Q. turbinella (Tucker, 1961). In the present paper, the total distribution of the hybrids between Q. gambelii and Q. turbinella is given. Lacking direct genetic evidence, proof of hybridity is sought in a demonstration of the morphological intermediacy of these putative hybrids. Population samples of both parental species, other samples containing hybrids, and numerous individual hybrids, are analyzed on the basis of 6 differences between the parental species. The data obtained, presented in the form of pictorialized scatter diagrams, clearly show the general intermediacy of the hybrids. Of the various binomials that have been applied to forms in the Q. undulata complex, Quercus pauciloba Rydb. applies to this hybrid. The appropriate change in status (Quercus × pauciloba Rydb.) is made.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX I. A PRELIMINARY STATEMENT

Tucker , John M. (U. California, Davis.) Studies in the Quercus undulata complex. I. A preliminary statement. Amer. Jour. Bot. 48(3): 202–208. Illus. 1961.—The taxonomic history of Quercus undulata, a highly variable, problematic complex of the Southwest, is discussed. Conservatively treated as a single species, it comprises a wide range of forms which at one extreme approach Q. gambelii morphologically, and, at the other, Q. grisea, Q. turbinella, and other species. The postulate was made that Q. undulata had arisen through hybridization between these very different oaks. Field observations and preliminary study of numerous population samples confirm this postulate. (Detailed morphological analyses are in progress.) Seven species have apparently been involved—Q. gambelii (the “common denominator” of the complex) has hybridized in different parts of its range with one or another of the following: Q. arizonica, Q. turbinella, Q. havardii, Q. muehlenbergii, Q. mohriana, and Q. grisea. The latter 6 species are discussed individually, and the extent to which each contributes to the complex, and the area in which this occurs, are indicated.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX. III. THE CONTRIBUTION OF Q. ARIZONICA

Tucker, J. M. (U. California, Davis.) Studies in the Quercus undulata complex. III. The contribution of Q. arizonica . Amer. Jour. Bot. 50(7): 699–708. Illus. 1903.—Of the 7 oak species involved in the Quercus undulata complex, Q. arizonica contributes the least of all. The latter has hybridized with Q. gambelii at a few widely separated localities (listed in Table 1) in central Arizona, and northern Sonora and Chihuahua, Mexico. The putative hybrids (identifiable as Quercus undulata) occur as isolated individuals with the parental species. The parents, although regionally sympatric, are usually ecologically isolated. They differ in a number of morphological characters, 6 of which were analyzed in detail. The resulting data, presented as pietorialized scatter diagrams, demonstrate that the putative hybrids are intermediate, in general. This is taken as evidence of their hybrid nature. Factors limiting hybridization in oaks are discussed. It is speculated that hybridization between Q. arizonica and Q. gambelii has occurred since the postglacial hypsithermal interval.     

HOW DISCRETE ARE OAK SPECIES? INSIGHTS FROM A HYBRID ZONE BETWEEN QUERCUS GRISEA AND QUERCUS GAMBELII

The white oaks Quercus gambelii and Q. grisea overlap in distribution in New Mexico and Arizona. Within the region of overlap, there are numerous instances of contact between the two taxa. In some areas of contact morphologically, intermediate trees are common, whereas in others, morphologically intermediate trees are rare or absent. We describe a set of RAPD markers that distinguish between the two species and use these markers to examine patterns of gene exchange in an area of contact in the San Mateo Mountains of New Mexico. The markers are highly coincident with morphology and confirm that hybridization between the two species takes place. Despite the occurrence of hybrids, both species remain distinct, even in areas of sympatry, and marker exchange appears to be limited.     

A NEW SPECIES OF BLACK OAK (QUERCUS,SUBG. ERYTHROBALANUS,FAGACEAE) FROM THE SIERRA MADRE OCCIDENTAL,MEXICO

Quercus mcvaughii is described as a new species of black oak (subgenus Erythrobalanus) from the Sierra Madre Occidental, in northern Durango and western Chihuahua, Mexico. It is most closely related to the more southern Q. crassifolia. Sessile or subsessile hairs, usually of different sizes, on the abaxial leaf surface distinguish Q. mcvaughii from Q. crassifolia, where hairs are similar in size and conspicuously stipitate. A key is provided for distinguishing similar species in the region. Intergradation of Q. mcvaughii with Q. crassifolia, Q. hypoleucoides, and Q. sideroxyla is reported.     

Characterization of the placoderm (Gnathostomata) assemblage from the tetrapod‐bearing locality of Strud (Belgium,upper Famennian)

The placoderm fauna of the late Famennian tetrapod‐bearing locality of Strud, Belgium, is studied on the basis of historical and newly collected material. It includes the previously described antiarch Grossilepis rikiki, the groenlandaspidid Turrisaspis strudensis sp. nov. and the actinolepidoideid Phyllolepis undulata. P. undulata is thoroughly described and joins the list of the valid Phyllolepis species confidently diagnosed. A morphometrical analysis performed on the centronuchal and anterior ventrolateral plates of the Phyllolepis material demonstrates that there is only one species of Phyllolepis in Belgium (thus, Phyllolepis konincki becomes a junior synonym of P. undulata), that P. rossimontina (Pennsylvania) is a synonym of P. undulata and that the unity of the genus Phyllolepis is strongly supported, although the characterization of several species within this genus is blurred. The strong resemblance between the faunal compositions in Strud and Red Hill (Pennsylvania, USA) suggests important faunal exchanges between these regions of the Euramerica landmass.     

Rodent acorn selection in a Mediterranean oak landscape

Quercus suber, Quercus ilex and Quercus coccifera (Cork, Holm and Kermes oaks, respectively) are common evergreen oak species that coexist in the landscapes of the western part of the Mediterranean basin. Rodents are the main acorn predators and thus one of the main factors for understanding recruitment patterns in oaks. In this paper we analyse to what extent mice prefer acorns from one oak species over another in three oak species studied using acorn removal experiments and video tape recordings. Twenty labelled acorns from each of the three Quercus species (60 acorns) were placed in 40 cm×40 cm quadrats on each plot. Because selection might vary as a result of the vegetation context, we performed the trials in the five main vegetation types within the study area (four replicates in each vegetation type) in order to control for habitat influences on rodent acorn preferences (a total of 20 plots). The removal of 1,200 acorns occurred within 68 days. Mice removed 98.7% of the acorns. Q. ilex acorns were preferred over Q. suber and Q. coccifera in all vegetation types except in pine forest, where no acorn preferences were detected. Acorn removal rates differed with vegetation type, correlating positively with shrub cover. The distance at which acorns were displaced by rodents (mean =4.6 m±5.1 SD) did not differ between acorn species, but varied among vegetation types. Bigger acorns of Q. coccifera were selected only after Q. ilex and Q. suber acorns were depleted, while no size selection was detected for the latter two species. Thus, we conclude that rodents show preference for some oak acorns and that landscape context contributes significantly to rodent activities and decisions.     

A three-trophic-level analysis of the effects of plant hybridization on a leaf-mining moth

We investigated relationships between host plant hybridization in the Quercus grisea x Q. gambelii species complex and the distribution and performance of a leaf-mining moth in the genus Phyllonorycter. In 2 years at two sites Phyllonorycter densities were lowest on Q. grisea and increased through the categories of hybrid host plants to Q. gambelii. Direct host plant effects on Phyllonorycter performance were consistent with Phyllonorycter distribution; unexplained mortality of larvae in the mines, which is often associated with direct plant effects, decreased from Q. grisea through the hybrids to Q. gambelii. Plant hybridization influenced parasitism of Phyllonorycter. Parasitism was density dependent, and across all densities was higher on Q. grisea and Q. gambelii than on hybrid host plants.     

THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES,RHODOPHYTA). I. CRYPTONEMIA KALLYMENIOIDES (HARVEY) KRAFT COMB. NOV. AND C. UNDULATA SONDER1

Several southern Australian red algae of the family Halymeniaceae (Cryptonemiales) are differentiated into hard, massive stalks and considerably softer laminar blades or phyllodes. The taxonomy, morphology and pit-connection ultrastructure of one such species, Cryptonemia kallymenioides (Harvey) Kraft comb. nov., are compared to C. undulata Sonder, which lacks massive stalks. In both species there is extensive periodic secondary cortication of the stalks, resulting in the formation of distinct “growth rings.” The blades of C. kallymenioides appear to be seasonal and its stalks perennial, while plants of C. undulata are apparently perennial but shorter lived than C. kallymenioides. As a result, stalks in the latter can reach 2–3 cm in diameter with up to 18 growth rings, compared to the 1–2 mm diameters and up to 6 rings within the stalks of C. undulata. Heavy secondary thickening of cortical cell walls occurs in both species and confers a “woody” texture to the stalks of C. kallymeniodes. Regardless of the large differences in average stalk diameters between the two species, the pit-connection ultrastructure from cortex to medulla shows much the same sequence of morphological modification. Pit-connections are standard red algal structures in the outer cortex, but become increasingly convoluted on the membrane-bound surfaces abutting cytoplasm and develop wider apertures and less dense cores with increasing distance from the stalk surface. In occasional medullary cells of C. kallymenioides, the cytoplasm disintegrates, leaving cell walls and pit-connections to play an apparently structural role which has not been reported in other red algae. It is suggested that the increase in aperture size and surface areas of pit-connections is compatible with their playing a role in the intercellular transport of solutes towards the inner cell layers which may, in C. kallymenioides, lie many millimeters distant.     

Mating-type Distribution and Fertility Status in Magnaporthe grisea Populations from Argentina

Isolates of Magnaporthe grisea causing gray leaf spot on rice were collected in Argentina and analyzed for mating distribution and fertility. One hundred and twenty-five isolates of M. grisea were collected from rice plants between 2000 and 2003. Each isolate was tested for mating type through a polymerase chain reaction based assay. All M. grisea isolates from Argentina belonged to a single mating type, MAT1.1. The fertility status of isolates was determined using controlled crosses in vitro, pairing each isolate with GUY11 and KA9 (MAT1.2 standard hermaphroditic testers). Production of perithecia was scarce among isolates of the blast pathogen since a low percentage of them (7.2%) developed perithecia with only one of the fertile tester (KA9); all crosses failed with the other tester strain. Asci and ascospores were not observed. The presence of only one mating type and the absence of female fertile isolates indicate that sexual reproduction is rare or absent in M. grisea populations associated with rice in Argentina.     

VARIATION IN THE NUTRIENT CONTENT OF LEAVES OF QUERCUS ALBA,QUERCUS COCCINEA,AND PINUS RIGIDA IN THE BROOKHAVEN FOREST FROM BUD-BREAK TO ABSCISSION

Leaves of Quercus coccinea, Q. alba, and Pinus rigida were collected at six dates during the growing season and analyzed for N, P, K, Ca, Mg, Fe, S, and Na. Leaf weights per unit of leaf area (or length) were determined for the same period. Quercus coccinea and Q. alba leaves increased in weight per unit area by about 30 % and 50 %, respectively. First-year pine leaves increased in weight per unit length by about 65 %. During the second year the weight of pine leaves changed little. Two broad patterns in the nutrient content of leaves were apparent when nutrient content was expressed on the basis of leaf area rather than leaf weight. N, P, and K concentrations increased to a peak in mid- or late summer and declined abruptly just prior to abscission. Concentrations of other elements tended to rise slowly throughout the life of the leaves in all three species. The differences among nutrients and among species support the hypothesis that differential partitioning of the nutrient pool occurs as a result of evolutionary adaptation. The changes in weight of leaves per unit area and in nutrient content during the growing season are important for studies of net primary production and in appraisals of the cycling of nutrients. Least distortion of nutrient relationships occurs when area or length of leaf is used as the basis for expression of nutrient content.     

NOTES ON THE NESTING OF THE WHITE-FRONTED SANDPLOVER,Charadrius marginatus,AT GAMTOOS RIVER MOUTH IN 1950

Young, H.G. 1999. Comparative study of the courtship displays of Meller's Duck Anus melleri, Yellowbilled Duck A. undulata and Northern Mallard A. platyrhynchos. Ostrich 70(2): 117–122

The little-known Meller's Duck Anas melleri is a monochromatic species endemic to Madagascar that has been linked to the Northern Mallard A. platyrhynchos, or the African Yellowbilled Duck A. undulata. This study compared group courtship between these species, and analysed the structure and duration of the main display components, the grunt-whistle, head-up-tail-up and down-up. Meller's Duck differed significantly from the other species, and lacked a down-up display. Meller's Duck shows some behavioural similarities to the African Black Duck A. sparsa.     

Guild structures of seed insects in relation to acorn development in two oak species

We investigated patterns of acorn growth in Quercus variabilis Blume and Quercus serrata Thunb., seasonal trends in emergence of seed insects found in the acorns, oviposition periods of the insects and falling periods of insect-infested acorns. In Q. variabilis, two insect guilds were associated with acorn development: (i) the immature acorn feeding (IAF) guild [Curculionidae sp., Poecilips cardamomi (Schaufuss), and Characoma ruficirra (Hampson)]; and (ii) the mature acorn feeding (MAF) guild [Curculio robustus (Roelofs), Curculio sikkimensis (Heller), and Cydia glandicolana (Danilevsky)]. In Q. serrata, there were three guilds: (i) the pistillate flower feeding (PFF) guild (cynipid wasp); (ii) the IAF guild [sap absorption by Mechoris ursulus (Roelofs)]; and (iii) the MAF guild (M. ursulus, C. sikkimensis, Cydia danilevskyi (Kuznetzov), C. glandicolana and Autostichidae sp.). The succession of guilds during acorn development may be a consequence of the use by different species of the limited food resource. The lack of a PFF guild in Q. variabilis that was found in our field site would have a positive effect on IAF guilds in utilizing the acorns.     

Hoarding behaviors of two wood mouse species: Different preference for acorns of two Fagaceae species

Two species of wood mouse, Apodemus argenteus and A. speciosus, were observed consuming and hoarding acorns of Quercus serrata and Castanopsis cuspidata. When each species of acorn was supplied individually, both species of mice used each species of acorn for eating and hoarding. When both species of acorn were supplied, A. argenteus consumed or hoarded only C. cuspidata, whereas A. speciosus tended to eat C. cuspidata acorns at the feeding site, and disperse or hoard Q. serrata acorns. Apodemus speciosus is unlikely to disperse C. cuspidata acorns (their utilization was biased towards consumption) when Q. serrata acorns are also available. Apodemus argenteus will make almost no contribution to the dispersal of Q. serrata when the two acorn species coexist.     

Not only size matters: Acorn selection by the European jay (Garrulus glandarius)

A strong selection for acorn characteristics is expected to have evolved in the mutualistic relationship between the European jay (Garrulus glandarius) and the oak (Quercus spp.). Bossema's pioneer work suggested that jays do not select acorns randomly, but rather they preferentially select some size and species. Preference for some seeds over others may have implications on plant community dynamics by conferring advantages (or disadvantages) on the selected (avoided) seed characteristics. In this paper we test to what extent jays select acorns by species and/or by size and the relation between these two traits in Mediterranean oak species. The experiments consist of a set of field tests in which acorns from four different coexisting Mediterranean oak species (Quercus ilex, Quercus faginea, Quercus suber, and Quercus coccifera) were placed in artificial feeders accessible to wild jays. The acorns were previously measured to control individual acorn characteristics. Using video-recording techniques, we followed jay activity and the fate of each acorn (sequence of acorn selection and method of transport). Q. ilex acorns were preferred over other acorns, and Q. coccifera acorns were avoided when other acorns were available. Preference for Q. faginea and Q. suber acorns was intermediate, that is, they were preferred over Q. coccifera acorns but not over Q. ilex acorns. Large acorns were also preferred although acorn species selection was stronger than size selection. Jays selected species and size both by visual means and by using acorn area as an indicator of size. Acorns wider than 17–19 mm were carried in the bill because of throat limitation. Our results confirm Bossema's study on temperate oaks and extend it to Mediterranean oak species, revealing implications on mixed oak forest dynamics.     

ULTRASTRUCTURE OF VEGETATIVE ORGANIZATION AND CELL DIVISION IN THE UNICELLULAR RED ALGA DIXONIELLA GRISEA GEN. NOV. (RHODOPHYTA) AND A CONSIDERATION OF THE GENUS RHODELLA1

This study suggests that the genus Rhodella be restricted to that set of features currently observed only in Rhodella maculata Evans and Rhodella violacea (Korn-mann) Wehrmeyer, that a new genus Dixoniella be established to accommodate the unicellular red alga, Rhodella grisea (Geitler) Fresnel, Billard, Hindák et Pekár-ková, and that Rhodella cyanea Billard et Fresnel be further studied for probable reclassification. These conclusions are based on ultrastructural comparisons of Dixoniella grisea with published information on the genus Rhodella. The presence of thylakoids in the pyrenoid, a peripheral encircling thylakoid in the chloroplast, a dictyosome/nuclear envelope association, and the lack of a specialized pyrenoid/nucleus association in D. grisea separate this alga from the genus Rhodella. Cell division in D. grisea is not demonstrably different from that in Rhodella, although the unusually well-defined material of the presumptive microtubule organizing center (MTOC) made it possible to follow the development and behavior of the MTOC to a greater degree than in previously studied red algal cells. The surprising amount of conformity in cell division characters between D. grisea and the genus Rhodella prompted a comparison of cell division characteristics in all red algal unicells studied to date. All unicells show a remarkable degree of similarity except for differences in interzonal spindle length, dissimilarities in size of the nucleus-associated organelle (NAO), and the unusual NAO of Porphyridium purpureum (Bory) Drew et Ross.     

Acorn crop size and pre-dispersal predation determine inter-specific differences in the recruitment of co-occurring oaks

The contribution of pre-dispersal seed predation to inter-specific differences in recruitment remains elusive. In species with no resistance mechanisms, differences in pre-dispersal predation may arise from differences in seed abundance (plant satiation) or in the ability of seeds to survive insect infestation (seed satiation). This study aimed to analyse the impact of pre-dispersal acorn predation by weevils in two co-occurring Mediterranean oaks (Quercus ilex and Quercus humilis) and to compare its relevance with other processes involved in recruitment. We monitored the patterns of acorn production and acorn infestation by weevils and we conducted experimental tests of acorn germination after weevil infestation, post-dispersal predation and seedling establishment in mixed forests. Monitoring and experimental data were integrated in a simulation model to test for the effects of pre-dispersal predation in recruitment. In both oaks pre-dispersal acorn infestation decreased with increasing acorn crop size (plant satiation). This benefited Q. ilex which exhibited stronger masting behaviour than Q. humilis, with almost a single and outstanding reproductive event in 6 years. Acorn infestation was more than twice as high in Q. humilis (47.0%) as in Q. ilex (20.0%) irrespective of the number of seeds produced by each species. Although germination of infested acorns (seed satiation) was higher in Q. humilis (60%) than in Q. ilex (21%), this could barely mitigate the higher infestation rate in the former species, to reduce seed loss. Conversely to pre-dispersal predation, no inter-specific differences were observed either in post-dispersal predation or seedling establishment. Our results indicate that pre-dispersal predation may contribute to differences in seed supply, and ultimately in recruitment, between co-existing oaks. Moreover, they suggest that seed satiation can barely offset differences in seed infestation rates. This serves as a warning against overemphasising seed satiation as a mechanism to overcome seed predation by insects. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Summer-drought constrains the phenology and growth of two coexisting Mediterranean oaks with contrasting leaf habit: implications for their persistence and reproduction

This study analyses how coexisting evergreen and deciduous oaks adjust their phenology to cope with the stressful Mediterranean summer conditions. We test the hypothesis that the vegetative and reproductive growth of the winter deciduous (Quercus faginea Lam.) is more affected by summer drought than that of the evergreen [Quercus ilex L. subsp. ballota (Desf.) Samp.]. First, we assessed the complete aboveground phenology of both species during two consecutive years. Shoot and litter production and bud, acorn and secondary growth were monitored monthly. Second, we identified several parameters affected by summer conditions: apical bud size, individual leaf area (LA), leaf mass per area (LMA) and acorn yield in both species, and leaf-fall in Q. faginea; and analysed their variation over 10 years. Q. ilex performed up to 25% of shoot growth and most leaf development during summer, whereas Q. faginea completed most of both phenophases during spring. Secondary growth was arrested in summer under drought conditions. Approximately, 30–40% of bud and 40–50% of acorn growth was undertaken during summer in both species. Summer drought related to differences in LA, LMA and leaf senescence, but not to acorn yield. Both species had similar year-to-year patterns of acorn production, though yields were always lower in Q. faginea. Bud size decreased severely in both species during extremely dry years. In Q. ilex, bud size tended to alternate between years of large and small buds, and these patterns were followed by opposite trends in stem length. In Q. faginea, bud size was more stable through time. Q. ilex was more phenologically active during summer than Q. faginea, indicating a higher tolerance to drought. Furthermore, bud and fruit growth (the only two phenophases that both species performed during summer) were more severely affected by summer drought in Q. faginea than in the evergreen. The differential effects of summer drought on key phenophases for the persistence (bud growth) and colonization ability (fruit production) of both species may have consequences for their coexistence.     

Early seedling growth of pine (Pinus densiflora) and oaks (Quercus serrata,Q. mongolica,Q. variabilis) in response to light intensity and soil moisture

In climatic chambers seed germination and seedling growth of Pinus densiflora Sieb. et Zucc., Quercus serrata Thunb., Quercus mongolica Fisch. ex Turcz. and Quercus variablilis Bl. were investigated as functions of light intensity and soil moisture. In Korea these tree species occur widely and form mixed forests with different distributions. Species clearly differed in the pattern of germination and early seedling growth between light and soil treatments. The germination of pine did not differ between the experimental treatments until the breaking of the primary buds. After that, light intensity was the deciding factor for further development. In the most moist treatment (approx. field capacity) growth of the pine seedlings was strongly inhibited. For the three oak species, differences between experimental treatments first occurred after complete formation of primary leaves. Seed development strongly correlated with the weight of the acorn. The large seeded Q. variabilis (acorns with mean weight of 4.7 g) developed faster and reached larger dimensions towards the end of the experiment than Q. mongolica (2.8 g per acorn) and Q. serrata (0.9 g per acorn). Regarding height and biomass growth, the oak species showed a higher shade tolerance than pine. The proleptic shoot growth was clearly influenced by the light intensity. Root formation was favoured by a high exposure to light. In case of the oak species reduction of soil moisture increased the length of primary roots and the number of secondary roots.