NATURE OF THE PLANT COMMUNITY. VI. TEXAS GRASSLAND COMMUNITIES UNDER TRANSPLANTED CONDITIONS

Mc Millan , Calvin . (U. Texas, Austin.) Nature of the plant community. VI. Texas grassland communities under transplanted conditions. Amer. Jour. Bot. 48(9): 778–785. Illus. 1961.—Clones of 7 grass taxa, Bouteloua gracilis (H. B. K.) Lag., B. eriopoda (Torr.) Torr., B. curtipendula (Michx.) Torr., Panicum virgatum L., the Andropogon scoparius Michx. complex, the Andropogon gerardi Vitman-hallii Hack. complex, and Sorghastrum nutans (L.) Nash, were transplanted from throughout their distribution in Texas and studied in an experimental garden at Austin. Restricted to western Texas and Panhandle areas, Bouteloua gracilis and B. eriopoda contained similar early-flowering clones throughout their distribution. Less restricted to western sites, B. curtipendula contained later-flowering types from eastern and central areas. In the 4 remaining, widespread taxa, early-flowering potential characterized clones from western sites. These 4 widespread taxa contain the latest-flowering clones from the coast of southern Texas. Clones of Stipa leucotricha Trin. and Rupr. from a broad area in Texas lacked a flowering gradient. Grassland communities of western Texas and the Panhandle, attuned to short growing seasons and low rainfall, were composed of opportunists, the Bouteloua species, and early-flowering variants within the widespread species. Communities of central Texas in habitats of highly unpredictable moisture pattern and a relatively long growing season contained later-flowering variants. Coastal communities attuned to a long growing season contained the latest-flowering variants.     

Densities of the arundo wasp,Tetramesa romana (Hymenoptera: Eurytomidae) across its native range in Mediterranean Europe and introduced ranges in North America and Africa

Tetramesa romana is a biological control agent of the giant reed, Arundo donax (Poaceae: Arundinoideae), which is an invasive weed in the riparian habitats of the Rio Grande Basin of Texas, the southwestern U.S.A. and northern Mexico. Field evaluations were conducted in the native range of T. romana in Mediterranean Europe and in the introduced ranges of Texas, California, and South Africa to compare densities of the wasp. Population densities and percentage parasitism levels for the 2017 year are compared to meteorological variables (average temperature, precipitation, and heat units). In the introduced ranges of Texas (intentional) and South Africa (adventive) T. romana population densities were 39 and 10-fold higher than in the native range, respectively. Percentage parasitism of T. romana in Texas and in the native range of Thessaloniki, Greece were 2.0% and 34.3%, respectively. Annual heat unit accumulation was 1.3–2.7-fold higher at Texas sites than at other introduced or native sites, and heat units were positively associated with exit hole counts at introduced sites. Annual precipitation was 2-fold higher at Texas and South African sites than in California and the native range sites. Favourable weather conditions and reduced parasitism in Texas along the Rio Grande, as compared to the native range, allows T. romana to reach higher population levels and cause considerable damage to A. donax.     

Initial Genetic Analysis of Xylella fastidiosa in Texas

Xylella fastidiosa is the causative agent of Pierce’s Disease of grape. No published record of X. fastidiosa genetics in Texas exists despite growing financial risk to the U.S. grape industry, a Texas population of the glassy-winged sharpshooter insect vector (Homalodisca vitripennis) now spreading in California, and evidence that the bacterium is ubiquitous to southern states. Using sequences of conserved gyrB and mopB genes, we have established at least two strains in Texas, grape strain and ragweed strain, corresponding genetically with subsp. piercei and multiplex, respectively. The grape strain in Texas is found in Vitis vinifera varieties, hybrid vines, and wild Vitis near vineyards, whereas the ragweed strain in Texas is found in annuals, shrubs, and trees near vineyards or other areas. RFLP and QRT PCR techniques were used to differentiate grape and ragweed strains with greater efficiency than sequencing and are practical for screening numerous X. fastidiosa isolates for clade identity.     

SURVIVAL PATTERNS IN FOUR PRAIRIE GRASSES TRANSPLANTED TO CENTRAL TEXAS

Transplanted clones of four widespread prairie grasses, Andropogon scoparius, A. gerardii, Panicum virgatum, and Sorghastrum nutans, that had survived in cultivation 1958-1962 in central Texas were studied without cultivation 1963-67 to determine survival patterns. In all four species, clones from northern and eastern sites in the United States were eliminated. Survival of A. scoparius was restricted to plants originating in central and southern Texas and in northern Mexico. Surviving clones of A. gerardii, P. virgatum, and S. nutans were chiefly of Texas origin but included other clones mostly from the south central United States. Population samples of the four species from a central Texas grassland community showed greatest survival in a multi-ramet comparison of clones originating from North Dakota to Mexico City and in a multi-clone comparison from six sites in Texas and one in New Mexico. While the superior adaptation to the local habitat by the local populations might have been expected, this study documented the survival potential of organisms in the local ecosystem.     

Ecological studies of the nemertean fauna in an estuarine system of the northwestern Gulf of Mexico

The distribution and abundance of nemerteans in the brackish-water lakes of Sea Rim State Park, Texas, near the Louisiana border, were studied and compared with other macrobenthos during one year. Six of 93 macrobenthic species collected were nemerteans (0.9% of the total number of specimens). Only one species of nemertean, Carinoma sp., was consistently present. This species is the most ubiquitous and, probably, the most abundant nemertean in the estuarine systems of the Texas coast. Carinoma sp. was collected at Sea Rim from a salinity range of 0–21 ppt and at other Texas estuaries from 2–26 ppt. Preliminary experiments with Carinoma sp. as predator and as prey indicated that it feeds on polychaete worms and in turn is fed upon by white (Penaeus setiferus) and brown (P. aztecus) shrimp.     

ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. I. MORPHOLOGICAL VARIATION WITHIN TRANSPLANTED COMMUNITY FRACTIONS

Ecological variation within transplanted community fractions, containing Andropogon scoparius Michx., A. gerardi Vitman, Panicum virgatum L. and Sorghastrum nutans (L.) Nash, included broad behavioral and morphological differentiation. In Austin, Texas, during 1958–1962, southern community fractions that contained early spring activity, late flowering and late fall dormancy included taller plants than early-flowering, northern community fractions. The tallest populations in all 4 species originated in Texas. In P. virgatum, size of leaves and panicles showed north-south trends similar to culm height values. Leaf pubescence and leaf glaucousness in all 4 species showed geographic patterning that was not correlated with north-south maturity gradients. Greatest pubescence was on clones in community fractions from pine woods in the Southeast. Glaucousness was concentrated in community fractions from central Texas northward to Nebraska.     

MORPHOLOGICAL AND PHYSIOLOGICAL DIFFERENTIATION OF PHORADENDRON POPULATIONS IN TEXAS

Investigation of the morphology and physiology of the mistletoe, Phoradendron tomentosum subsp. tomentosum, in Texas reveals that the subspecies is differentiated into at least two ecological races, one in north central Texas, the other in south central Texas. The races differ in leaf length/width ratio, fruit diameter, seed set, spike internode length, freeze tolerance, and flavonoid patterns. Clines occur in leaf length/width ratio and fruit diameter between the races, and these characteristics are negatively correlated. The northern race generally exhibits greater freeze tolerance than the southern race. Field observations, herbarium specimens, and a collection of fresh specimens from northeastern Mexico indicate that a third race in the subspecies may exist there. Racial variation within the subspecies appears to permit it to occupy a diversity of habitats. Morphological and physiological patterns within the two Texas races suggest that introgressive hybridization has occurred between them, allowing for the occupation of intermediate habitats.     

Second generation experimental hybridizations in theEchinocereus ×lloydii complex (Cactaceae), and further documentation of dioecy inE. coccineus

Artificial second generation and backcross hybrids involvingEchinocereus dasyacanthus (Texas rainbow cactus),E. coccineus (a species of claret-cup cactus), andE. ×lloydii (Lloyd's hedgehog cactus) were examined for morphological and reproductive characteristics. The hybrids grew from seed to flower in about four years, and they exhibited high fertility as measured by pollen stainability, crossability, and fruit-set. A rare breeding system inCactaceae, dioecy, was further examined inE. coccineus, using field and controlled pollination tests. Functional dioecy was documented forE. coccineus in Trans-Pecos Texas. All results suggested thatE. ×lloydii in eastern Pecos County, Texas, is a complex and dynamic population probably comprising first and later generation hybrids, including backcross hybrids. The experimental hybridizations also tended to support the occurrence of introgression into both putative parental species.     

New records of aquatic Oligochaeta from Texas,with observations on their ecological characteristics

Twenty-six species of aquatic oligochaetes are reported from Texas, including 18 Naididae, seven Tubificidae, and one Glossoscolecidae. Illustrations are provided for ten species recorded for the first time from the state: Chaetogaster cristallinus, Nais elinguis, Nais pardalis, Pristina acuminata, Pristina sima, Stylaria lacustris, Aulodrilus limnobius, Ilyodrilus templetoni, Limnodrilus claparedianus, and Sparganophilus tamesis. Species accounts include presently known distributions in Texas and ecological and morphological characteristics.     

Host plant trichomes and the advantage of being big: progeny size variation of the pipevine swallowtail

1. Plants possess numerous traits that confer resistance against insect herbivores, and herbivores, in turn, can evolve traits to ameliorate the effectiveness of these traits. The pipevine swallowtail, Battus philenor, is an extreme specialist on plants in the genus Aristolochia. The only host plant available to the California population of B. philenor is A. californica. Aristolochia californica is distinct from most other B. philenor host plants in that it is pubescent. 2. The progeny of B. philenor are larger in California compared with populations examined in Texas. Size differences persist throughout larval development. 3. Regardless of maternal host plant, population differences in progeny size persist, and crosses between California (large progeny) and Texas (small progeny) B. philenor populations resulted in offspring producing intermediate sized progeny, indicating a heritable component to progeny size variation. 4. California neonate caterpillars more easily overcame the trichomes of A. californica compared with Texas neonates. When trichomes were removed from A. californica, time to feeding establishment was reduced for caterpillars from both populations. Texas caterpillars established feeding sites on A. californica with trichomes removed, in the same time required to establish feeding on their non‐pubescent host plant, A. erecta. 5. This study shows that plant trichomes might impose selection pressure on progeny size.     

Four new species of <Emphasis Type="Italic">Aulonastus</Emphasis> Kethley, 1970 (Acari: Syringophilidae) from North American passerines

Four new species belonging to Aulonastus Kethley, 1970 (Acari: Prostigmata: Syringophilidae), which are found inside the quills of body feathers of North American passerines (Aves: Passeriformes), are described and figured: A. emberizicus n. sp. from Ammodramus savanarum (Gmelin) (Emberizidae) (type-host) in Texas, Zonotrichia atricapilla (Gmelin) (Emberizidae) in California and Passerculus sandwichensis (Gmelin) (Emberizidae) in Texas; A. euphagus n. sp. from Euphagus cyanocephalus (Wagler) (Icteridae) in California; A. pirangus n. sp. from Piranga ludoviciana (Wilson) (Cardinalidae) in California; and A. sturnellus n. sp. from Sturnella magna (Linnaeus) (Icteridae) in Texas. A key to females of the known species of Aulonastus is presented.     

Comparative morphology and reproductive compatibility between populations ofEuseius mesembrinus (Acari: Phytoseiidae) from Florida and Texas

Field specimens ofEuseius mesembrinus (Dean) from Florida and Texas were found to be morphologically similar regardless of differences in the lengths of dorsal shield setae or the St IV macroseta. Populations from both states were reproductively compatible. Taxonomic characters ofE. mesembrinus were illustrated using both light and scanning electron microscopy. Lengths of dorsal shield setae and the macroseta on the tarsus of leg IV of field-collected specimens from Florida and Texas, laboratory cultures, and their crosses (F1) showed inconsistent variance. Multivariate analysis of variance and canonical discriminate analysis revealed that the source of variance can be attributed to ecological factors. The results suggest that the two populations are the same species and support the possibility that the Florida population originated from Texas.Florida Agricultural Experiment Station Journal Series No. R-00380.     

Impacts of weather on northern bobwhite sex ratios,body mass,and annual production in South Texas

A landscape-scale assessment of how bobwhite productivity varies in relation to weather does not exist for northern bobwhite (Colinus virginianus). We collected age and sex ratio and body mass data from hunter-harvested bobwhites in 16 counties of South Texas (n = 72,797 bobwhites) during 2001–2009 hunting seasons. We evaluated annual bobwhite production (juvenile:adult age ratios) as a function of cumulative April–August rainfall using National Oceanic and Atmospheric Administration (NOAA) weather station data from Falfurrias and Hebbronville, Texas. We observed minimal among-year change in percent males harvested (51.0–54.5% male) and mean mass (156–160 g) of bobwhites across South Texas. We found no relationship between percent male or body mass and weather. We documented a positive, linear relationship between cumulative April–August rainfall and bobwhite age ratios (r² = 0.94); we also documented a negative, linear relationship between summer (Jun–Aug) mean maximum daily temperature and bobwhite age ratios (r² = 0.38). Our results suggest that rainfall is a landscape-scale indicator of annual bobwhite production in South Texas and can thus be used to manage annual expectations of quail hunters prior to the hunting season. © The Wildlife Society, 2012     

PHOTOPERIOD IN XANTHIUM POPULATIONS FROM TEXAS AND MEXICO

Photoperiodic responses of Xanthium strumarium L. originating between 19° N in Mexico and 34° N in Texas varied among seedlings grown from seed under controlled conditions. The critical night lengths form a gradient from 9.5 hr in northern Texas to 10.75 hr in southern Texas and northeastern Mexico. Populations with critical night lengths of 9.5 and 9.75 hr showed a longer interval to flower bud formation under cooler temperatures (24 C day/15 C night) than under warmer temperatures (30 C day/24 C night). Three of four populations with a 10.75-hr critical night length showed a shorter interval under the cooler temperature regime. Although the Texas populations demonstrate a strong correlation of photoperiodic response with latitude, the Mexico populations show diverse photoperiodic timing from approximately the same latitude. The study emphasizes that a combination of critical night length and ripeness-to-flower (maturity) response forms the basis for reproductive adaptation in different climatic regimes in Texas and Mexico.     

COMPARATIVE PHYSIOLOGY AND BIOCHEMISTRY AND TAXONOMIC ASSIGNMENT OF THE CHLORELLA (CHLOROPHYCEAE) STRAINS OF THE CULTURE COLLECTION OF THE UNIVERSITY OF TEXAS AT AUSTIN1

The species of the genus Chlorella exhibit considerable biochemical and physiological differences. Therefore, it is important to select for and utilize in research or biotechnology correctly identified strains of the species having the most favorable properties for the respective project. We examined the Chlorella strains of the University of Texas collection at Austin, Texas, according to species-specific chemotaxonomic characters and assigned 58 strains to 10 well-established species (only 17 of these strains were correctly named before).     

THE ROLE OF POPULATIONAL DIFFERENTIATION IN EXPERIMENTAL INFECTION OF PROSOPIS BY PHORADENDRON

Experimental infection of Prosopis species with the mistletoe Phoradendron tomeniosum subsp. tomentosum in a uniform garden demonstrated that differences in infection success between species, populations, and individuals can be caused by genetically-based differences in both hosts and parasites. Prosopis glandulosa var. glandulosa was least resistant to infection; P. laevigata was more resistant; and P. torreyana was most resistant. A population of P. glandulosa var. glandulosa grown from seeds collected in the lower Rio Grande valley was significantly more resistant to infection than three populations of the same variety from central and northern Texas. The higher resistance of the Rio Grande valley population appears to be due to introgression with P. laevigata. The experimental population of Phoradendron tomentosum subsp. tomentosum from northeastern Mexico and the population of the same subspecies from southern Texas had greater infectivity than did those from central and northern Texas, corresponding to the greater resistance of the southern Prosopis populations.     

EVIDENCE FOR A MOSAIC HYBRID ZONE IN THE GRASS SHRIMP PALAEMONETES KADIAKENSIS (PALAEMONIDAE) AS REVEALED BY MULTIPLE GENETIC MARKERS

Molecular techniques provide powerful tools for studying the geographic structure of hybrid zones and the dynamics of gene exchange between incipient species. We examined allozyme variation at five loci (PGM, GPI, MDH-1, MDH-2, and LDH) for 27 populations of Palaemonetes kadiakensis from the central, coastal, and eastern regions of Texas. Central Texas populations of P. kadiakensis exhibited highly significant linkage disequilibrium and departures from Hardy-Weinberg genotype proportions. In populations with linkage disequilibrium, allelic differences at GPI defined two types of P. kadiakensis, designated A and B. Both types existed in central Texas with little or no evidence of interbreeding, whereas the populations from all other localities showed complete introgression of type B alleles into the type A gene pool. We also examined ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) variation in a subset of populations, chosen to cover a range of geographic locations and levels of linkage disequilibrium. Two groups of mtDNA haplotypes and two restriction fragment patterns for the rDNA corresponded to allozyme type A and B individuals in populations exhibiting linkage disequilibrium. In populations with ongoing hybridization, all hybrid animals (N= 15) exhibited type A mtDNA. Exhibition of type A mtDNA indicated that type A females had mated successfully with type B males, but type B females had not mated successfully with type A males. Genotype distributions suggest reduced reproduction by hybrid offspring in central Texas populations. These patterns are consistent with a mosaic model of hybrid zone dynamics.     

Inactivation of acetylcholinesterase by various fluorophores

The inhibition of recombinant mouse acetylcholinesterase (rMAChE) and electric eel acetylcholinesterase (EEAChE) by seven, structurally different chromophore-based (dansyl, pyrene, dabsyl, diethylamino- and methoxycoumarin, Lissamine rhodamine B, and Texas Red) propargyl carboxamides or sulfonamides was studied. Diethylaminocoumarin, Lissamine, and Texas Red amides inhibited rMAChE with IC₅₀ values of 1.00 μM, 0.05 μM, and 0.70 μM, respectively. Lissamine and Texas Red amides inhibited EEAChE with IC₅₀ values of 3.57 and 10.4 μM, respectively. The other chromophore amides did not inhibit either AChE. The surprising inhibitory potency of Lissamine was examined in further detail against EEAChE and revealed a mixed-type inhibition with K_i?=?11.7 μM (competitive) and K_i′?=?24.9 μM (noncompetitive), suggesting that Lissamine binds to free enzyme and enzyme–substrate complex.     

Opalinidae (Sarcomastigophora) in North American Amphibia. GenusProtoopalina Metcalf, 1918

During 1992, 83 specimens of North American Amphibia from Algonquin Park and Kingston, Ontario, Canada, and from El Paso County, Texas USA, comprising 14 species in seven families, were checked for opalinids in the cloaca.Protoopalina allisteri n. sp. is described from oneGastrophryne carolinensis (Microhylidae) from Arkansas andP. mitotica was found in one of fourScaphiopus multiplicatus (Pelobatidae) from Texas. The North American species ofProtoopalina are reviewed.Zelleriella ovoidea (Metcalf, 1923) is proposed as a new combination forP. ovoidea.