The role of seed depth,litter, and fire in the seedling establishment of amphicarpic peanutgrass (Amphicarpum purshii)

Summary Amphicarpum purshii is an annual grass which mostly grows in disturbed areas of the New Jersey Pine Barrens, USA. It is amphicarpic, producing spikelets (and seeds) both above and below the soil surface. Previous research has shown that subterranean seed production ensures reproduction in the event of a major disturbance such as fire and results in rapid post-burn colonization of these sandy habitats. The effects of fire, litter, and seed depth were further examined by planting subterranean seeds at four depths in 16 litter-covered flats buried at ground level and comparing plants arising from burned flats with those in undisturbed litter-covered flats. At 0 and 1 cm depth, rates of seedling emergence were lowest in burned flats. Surface-sown seeds produced seedlings more likely to desiccate. Sowing depth had a greater influence on most measured characters than burning treatments. The mean depth of subterranean seed placement by Amphicarpum is 3.5 cm and this coincides with the seed depth from which plants showed the greatest height growth, shoot biomass, and reproductive output. In a second experiment, subterranean seeds on the bare soil surface in clay pots were more likely to lose viability and less likely to germinate than seeds protected by litter or burial in soil. In addition to providing protection from fire, placement of seeds below ground in the sandy habitat of peanutgrass provides conditions more suitable for seed survival and subsequent seedling establishment.     

In the shadow of a megalopolis,a new Flexamia from a threatened grass species in the New Jersey Pine Barrens (Hemiptera,Cicadellidae, Deltocephalinae,Paralimnini)

A previously unknown species of the North American leafhopper genus Flexamia, Flexamia whitcombi sp. n., is described from pinebarren smokegrass (Muhlenbergia torreyana (Schult.) Hitchc.), a state-listed threatened grass in the New Jersey Pine Barrens. The serrata species group, to which it belongs, is redefined and a key to the species of the group is provided. This is the first reported insect association with Muhlenbergia torreyana.     

Photosynthetically elevated pH in acid waters with high nutrient content and its significance for the zooplankton community

The pH of undisturbed surface waters in the New Jersey Pine Barrens is very acidic (pH 3.5–4.5). Surface waters disturbed by residential and agricultural development typically exhibit significantly elevated pH. Detailed analyses of a disturbed and undisturbed pond showed that the elevated pH of the disturbed pond was primarily the result of enhanced primary productivity. At night and during the winter, when productivity was reduced, the pH dropped to levels more characteristic of the undisturbed pond. The phenomenon of fluctuating pH had significant implications for the zooplankton in the disturbed pond. Though nutrients were significantly greater in the disturbed pond, zooplankton species composition and general abundance patterns were nearly identical in the two ponds. Thus, in these and other poorly buffered waters, it is hypothesized that the lowest pH values were the ones effectively regulating the zooplankton community.     

Identifying Environmental Conditions to Promote Species Coexistence: An Example with the Native Barrens Topminnow and Invasive Western Mosquitofish

Coexistence of a native and invasive species may be possible at certain conditions along an environmental gradient where the individual responses of each species are maximally apart. Water temperature may differentially affect the growth of a native cool-water species like the Barrens topminnow, Fundulus julisia, and an originally warm-water adapted western mosquitofish, Gambusia affinis, who is a recent invader in Barrens Plateau region of middle Tennessee. We measured the specific growth rate (SGR) of the two species separately in laboratory aquaria at 10, 15, 20 and 25 °C, representing a range of temperatures that occur in topminnow habitats throughout the year. Both species grew faster with increasing temperature and SGRs were highest at 25 °C. The interspecific difference in SGR was maximized at 15 °C. At this temperature, mean growth rate of topminnows was 0.78% per day, more than twice that of mosquitofish (0.38% per day). These results suggest that cool springhead habitats with a near-constant thermal environment of 15 °C throughout the year may provide a growth advantage to the Barrens topminnow over the mosquitofish. Other environmental, density-dependent, or behavioral factors not examined here may act along with temperature to mediate the coexistence of the topminnow and mosquitofish.     

Multivariate discrimination among cryptic species of the mite genus Chaetodactylus (Acari: Chaetodactylidae) associated with bees of the genus Lithurgus (Hymenoptera: Megachilidae) in North America

Twenty-seven morphological characters from 111 heteromorphic deutonymphs of the mite genus Chaetodactylus Rondani (Acari: Chaetodactylidae) were analyzed. The mites were collected from four species of bees of the genus Lithurgus Berthold (Hymenoptera: Megachilidae) in continental North America. Principal component and canonical variates analyses on Darroch and Mosimann shape and size-and-shape variables revealed the presence of three cryptic species. Chaetodactylus gibbosi sp. n. (Florida) is geographically isolated from C. lithurgi sp. n. distributed in Texas, New Mexico, Arizona, Colorado, and Idaho. Sympatric C. lithurgi and C. abditus sp. n. (USA: Arizona, Mexico: Socorro Is.) are seasonally isolated in Arizona. Chaetodactylus gibbosi is associated with a single bee species, Lithurgus gibbosus Smith in Florida. The host range of C. lithurgi includes bees flying predominantly in the spring: L. apicalis Cresson, L. littoralis Cockerell, and western L. gibbosus. Chaetodactylus abditus sp. n. is associated with L. planifrons Friese and L. echinocacti Cockerell, flying predominantly in the fall in Arizona. No distinct groups separated by geographic locality or size were detected in any species. A six-variable model developed by the canonical variates analysis and estimated using jackknife resampling and external validation (n=100) is capable of classifying the three species with 100% accuracy. Factors that influenced speciation of cryptic species of Chaetodactylus associated with Lithurgus are discussed. Based on morphological and geographical data and data on mite associates, the western and eastern populations of the bee L. gibbosus are distinct. Therefore, the taxonomic status of L. gibbosus s. lat. should be reevaluated.     

VARIABILITY AMONG DANTHONIA SERICEA (GRAMINEAE) POPULATIONS IN RESPONSES TO SUBSTRATE MOISTURE LEVELS

Populations of Danthonia sericea from the New Jersey Pine Barrens were investigated as to possible ecological differentiation in moisture tolerances at germination, seedling, and mature plant stages. Field studies had indicated that populations with pubescent lemmas and leaf sheaths are restricted to well-drained sandy upland sites and that relatively glabrous populations are found in open bogs or low wet areas bordering rivers or ponds. Greenhouse studies of responses of clonal and seed materials to saturated, moist, and dry moisture levels showed significant differences among populations in germination, growth, and survival. Reciprocal transplants at upland and bog sites provided a field evaluation (1969–1974) of the survival and performance of the morphological variants in each other's habitat under competitive conditions. Restriction to respective habitats was found to be primarily intolerance of wet site factors for the pubescent plants coupled with an inability of glabrous plants to successfully compete in upland sites.     

A relative growth index of hybridization in sunfishes (genus Lepomis, Centrarchidae)

Sunfish specimens (genus Lepomis) collected from Pinehurst Lake, Ontario, Canada, were identified as bluegill (L. macrochirus), pumpkinseed (L. gibbosus) and their hybrids. Hybridization was studied on the basis of the constants of cross-sectional allometry as, to the best of our knowledge, no attempt has ever been made to study hybridization quantitatively from the relative growth aspect. Two sets of data---one on the pair Y¹/X (head length/standard length) and the other on the pair Y²/X (body depth/standard length)--- were analysed, with the following objectives: (i)A statistical method of analysing hybrid index based on cross-sectional allometry was first presented and then Y¹/X-data analysed by this method, and (ii)data Y²/X were analysed to show that in some particular situations analysis for hybridization by methods other than the hybrid index appraoch may be more appropriate. Results of the analyses were discussed.     

STRUCTURE AND DYNAMICS OF HARDWOOD SWAMPS IN THE NEW JERSEY PINE BARRENS: CONTRASTING PATTERNS IN TREES AND SHRUBS

The biomass, density, age structure, and dominance patterns of the tree and shrub populations in hardwood swamps of the New Jersey Pine Barrens are described and contrasted with each other. The total biomass of individual swamps ranges from 92,000 kg/ha to 194,000 kg/ha, depending on the age of the stand. These biomass values are similar to those reported for southern hardwood swamps. The Pine Barrens swamps are distinguished by very large populations of ericaceous and other shrubs, which range up to 13% of the total above-ground biomass. The tree populations, composed principally of Acer rubrum, Nyssa sylvatica and Magnolia virginiana, are even-aged; Acer is strongly dominating, with a minimum of 73% of the biomass, and species richness is associated with the availability of different microhabitats. The shrub populations, by contrast, are all-aged, with the dominance patterns among the species and the stand biomasses varying with the degree of flooding of the stand. Differences in size and growth rate among the shrub species parallel their evident response to the flooding gradient. The shrub stratum has lower species richness than the comparable southern swamps and floodplains, but ranges up to higher biomass values.     

QUANTITATIVE VARIATION OF LIFE HISTORY TRAITS IN AMPHICARPIC PEANUTGRASS (AMPHICARPUM PURSHII) AND ITS EVOLUTIONARY SIGNIFICANCE

Peanutgrass, Amphicarpum purshii, is a predominantly selling annual that exhibits an amphicarpic reproductive strategy, producing spikelets (and seeds) both above and below the soil surface. Both aerial and subterranean spikelets are self-fertile, but only the aerial spikelets are chasmogamous and capable of cross-pollination. This species mostly grows in disturbed areas of the New Jersey Pine Barrens. To examine life history variation, 60 quantitative characters were measured on twelve families raised from seeds collected from the aerial panicles of twelve parents grown in the greenhouse. Only 19 (= 31.7%) of the traits showed significant between-family phenotypic variation, and the mean percentage of the total variation due to family was 14.9 (N = 60 characters). Percentage biomass allocation and vegetative characters showed the highest narrow-sense heritabilities. Traits directly relevant to fitness such as subterranean seed set and seed weight of both seed types showed the least genetic variation. This low variation could reflect genetic fixation and/or developmental canalization of those fitness components important to survival in disturbed, early-successional habitats.     

Impact of nutrient enrichment and alkalinization on periphyton communities in the New Jersey Pine Barrens

The impact of residential and agricultural development on stream periphyton communities in the New Jersey Pine Barrens was examined by comparison with communities in undeveloped areas. Watershed disturbance resulted in stream water primarily characterized by greatly elevated pH levels and nitrate concentrations. A total of 53 periphyton species were encountered in bimonthly samples over a one year period in the three disturbed and three undisturbed study streams. Species richness was significantly greater in the disturbed streams based on three criteria: the average number of species per stream on each sampling occasion (disturbed = 6.3; undisturbed = 4.9), the average number of species per stream for the entire year (disturbed = 19.3; undisturbed = 16.0), and the total number of species found in streams within a type (disturbed = 40; undisturbed = 31). Species composition also changed significantly as the result of disturbance. There appeared to be replacement of species characteristic of undisturbed Pine Barrens streams with species peripheral to the region. The expected effects of both elevated pH and nitrate were consistent with these results.     

Factors affecting the occurrence and distribution of entomopathogenic fungi in natural and cultivated soils

Factors affecting the occurrence and distribution of entomopathogenic fungi in 244 soil samples collected from natural and cultivated areas in Spain were studied using an integrated approach based on univariate and multivariate analyses. Entomopathogenic fungi were isolated from 175 of the 244 (71.7 %) soil samples, with only two species found, Beauveria bassiana and Metarhizium anisopliae. Of the 244 soil samples, 104 yielded B. bassiana (42.6 %), 18 yielded M. anisopliae (7.3 %), and 53 soil samples (21.7 %) harboured both fungi. Log-linear models indicated no significant effect of habitat on the occurrence of B. bassiana, but a strong association between M. anisopliae and soils from cultivated habitats, particularly field crops. Also, irrespective of habitat type, B. bassiana predominated over M. anisopliae in soils with a higher clay content, higher pH, and lower organic matter content. Logistic regression analyses showed that pH and clay content were predictive variables for the occurrence of B. bassiana, whereas organic matter content was the predictive variable for M. anisopliae. Also, latitude and longitude predicted the occurrence of these same species, but in opposite directions. Altitude was found to be predictive for the occurrence of B. bassiana. Using principal component analysis, four factors (1 to 4) accounted for 86 % of the total variance; 32.8, 22.9, 19.6 and 10.4 % of the cumulative variance explained, respectively. Factor 1 was associated with high positive weights for soil clay and silt content and high negative weights for soil sand content. Factor 2 was associated with high positive weights for soil organic matter content and high negative weights for soil pH. Factor 3 was associated with high positive weights for latitude and longitude of the sampled localities and factor 4, had high positive weights only for the altitude. Bi-plot displays representing soil samples were developed for different factor combinations and indicated that, irrespective of geographical location, absence of both fungal species was determined by alkaline sandy soils with low organic matter content, whereas heaviness of soil texture, acidity and increasing organic matter content led to progressively higher percentages of samples harbouring entomopathogenic fungi. These results could aid decision-making as to whether or not a particular cultivated or natural soil is suitable for using entomopathogenic fungi as a pest control measure and for selecting the fungal species best suited to a particular soil.     

Patterns in shallow subtidal marine assemblages along the coast of New South Wales

Shallow subtidal areas of rocky reefs in central and southern New South Wales may best be described as a mosaic of habitats, the distributions of which are seemingly related to depth, wave exposure and a number of biological processes, particularly herbivory. The Fringe habitat is generally found only in the most shallow waters. Forests of the laminarian alga Ecklonia radiata are often found at intermediate depths. In deeper, or more sheltered water, sponges, ascidians and red algae are more abundant and the abundances of sea urchins and other invertebrate grazers decline. Overlying this broad-brush pattern are patches of crustose coralline algae (the Barrens habitat), the distributions of which are not clearly related to depth. Invertebrate herbivores, and sea urchins in particular, are abundant in the Barrens habitat. The Barrens habitat was most represented at the more southern locations. At the two most northern locations, reefs were shorter in length and dominated by ascidians (Pyura species).     

Mollusk collecting and environmental change during the Prehistoric Period in the Mariana Islands

Archaeological research in the Mariana Islands has revealed changes in mollusk collecting during the Prehistoric Period (approximately 1500 BC to AD 1521). The earliest people at Tumon Bay, Guam and Chalan Piao, Saipan collected mostly bivalves, especially the arc clam Anadara antiquata. After several hundred years, they no longer collected A. antiquata, but collected smaller bivalves instead. By AD 1000, they collected mostly gastropods, primarily the coral reef species Strombus gibberulus gibbosus. One possible explanation is that the people preferred the large arc clam but overharvested it until they were forced to eat the smaller bivalves and then the snails. However, recent evidence in the form of mangrove wood and mangrove pollen supports another explanation, one of non-anthropogenic environmental change. In this case, the relative sea-level decline, which took place in the Marianas within the last 4,000 years, caused the demise of mangrove habitats and of the arc clam at Tumon Bay, Guam and Chalan Piao, Saipan. As mangrove habitats were diminished by sea-level decline, collecting effort shifted to coral reefs, and S. gibberulus gibbosus was harvested throughout the remainder of the Prehistoric Period and into the Historic Period. Southern Guam is the only area in the Marianas in which A. antiquata increased in abundance during the Prehistoric Period. The same types of evidence, mangrove wood and mangrove pollen, indicate that, in contrast to the situation at Tumon Bay and Chalan Piao, mangroves increased in abundance in southern Guam.     

INFLUENCE OF ENVIRONMENT AND POPULATION ORIGIN ON SURVIVORSHIP AND REPRODUCTION IN RECIPROCAL TRANSPLANTS OF AMPHICARPIC PEANUTGRASS (AMPHICARPUM PURSHII)

Reciprocal transplants of both seeds and seedlings were utilized to determine whether populations of the annual grass Amphicarpum purshii have become locally adapted to specific habitats due to the consistent production of cleistogamous subterranean seeds from year to year. The hypothesis was that subterranean seeds placed in the same habitat as the parents will produce seedlings of greater vigor and adults of higher reproductive capacity than plants from seeds transplanted to a different habitat far removed from the parents. For both seed and seedling transplant experiments involving three sites in the Pine Barrens of New Jersey, the effects of site on shoot dry weight and production of aerial spikelets, subterranean spikelets, and seeds were generally much more significant than the effects of population origin. With one exception, there was no tendency for seedlings (or plants from seeds) replanted into their home sites to outperform alien seedlings (or plants from seeds) transplanted into these same sites. The overriding importance of environmental factors (relative to genetic differences among populations) in determining the phenotypic expression of life history characters, and selection occurring during succession at a site may retard the evolution of genetic adaptation to local habitat conditions in this species.     

Impact of insect defoliation on forest carbon balance as assessed with a canopy assimilation model

Disturbances such as fire, hurricanes, and herbivory often result in the net release of CO₂ from forests to the atmosphere, but the magnitude of carbon (C) loss is poorly quantified and difficult to predict. Here, we investigate the carbon balance of an oak/pine forest in the New Jersey Pine Barrens using the Canopy Conductance Constrained Carbon Assimilation (4C‐A) model. The 4C‐A model utilizes whole‐tree sap‐flux and leaf‐level photosynthetic gas exchange measurements at distinct canopy levels to estimate canopy assimilation. After model parameterization, sensitivity analyses, and evaluation against eddy flux measurements made in 2006, the model was used to predict C assimilation for an undisturbed year in 2005, and in 2007 when the stand was completely defoliated for 2–3 weeks during an infestation of gypsy moths (Lymantria dispar L.). Following defoliation, only 50% of the foliage reemerged in a second flush. In 2007, canopy net assimilation (A_nC), as modeled with the 4C‐A, was reduced to approximately 75% of A_nC in 2006 (940 vs. 1240 g C m^?2 a^?1). Overall, net primary production (NPP) in 2007 was approximately 240 g C m^?2 a^?1 (vs. 250 g C m^?2 a^?1 in 2006), with 60% of NPP allocated to foliage production, a short‐term carbon pool. Woody biomass accumulation, a long‐term carbon pool, was reduced by 20% compared with the previous year (72 vs. 57 g C m^?2 a^?1 in 2006 and 2007, respectively). The overall impact of the defoliation spanned 21% of upland forests (320 km²) in the New Jersey Pine Barrens, representing a significant amount of overall C not being taken up from the atmosphere by the forest, thus not accumulated in the biosphere.     

First record of the brown lanternshark,Etmopterus unicolor, from the waters around New Zealand, and comparison with the southern lanternshark,E. granulosus

Specimens of the brown lanternshark,Etmopterus unicolor, reported here for the first time from the waters around New Zealand, were caught on bottom longlines. This study compares morphometeric and meristic characters of New Zealand and Japanese specimens ofE. unicolor and New Zealand specimens of the southern lanternshark,E. granulosus. E. unicolor andE. granulosus are clearly distinguishable by the height of the first dorsal fin, number of spiral valves, number of vertebrae, and shape of the dermal denticles and teeth.     

On the habitats,distribution and life-cycles of the Western European species of the genus Helochares Mulsant (Coleoptera: Hydrophilidae)

Adult water beetles were collected from 841 localities in the Netherlands. The distribution maps of the three species of the genus Helochares (Coleoptera; Hydrophilidae) in the Netherlands are given. They are based on specimens from museum collections and this investigation. H. lividus occurs all over the Netherlands, except for the north-east. This northern limit of its European distribution area coincides with the 8.5°C isotherm for the mean year temperature. H. obscurus is limited in its distribution to clay and peat-bog, but in the sandy coastal dune area H. obscurus replaces H. punctatus. H. punctatus is limited in its distribution to soils consisting of peat-moor or sand, but it is absent from the coastal dune area.Co-existence of H. lividus with either H. obscurus or H. punctatus occurs regularly. Co-existence of H. obscurus and H. punctatus has been observed only once, these species exclude each other by different ecological requirements. H. lividus and H. obscurus show two optima in abundance during the year which corresponds with a univoltine life-cycle. H. punctatus shows no clear maximum in abundance. However, on the basis of the presence of females carrying egg-cases and the presence of teneral adults a univoltine life-cycle for all three Helochares spp. can be deduced. A small proportion of the beetles hibernates either as larva or as pupa and emerges in spring.The distribution of Helochares spp. has been related to some environmental variables using the Index of Representation. H. lividus has a clear preference for waters with a high pH, high conductivity and high chlorinity with a luxurious vegetation of floating leaved and submerged plants on mineral soils. Occasionally running waters or waters with a low current velocity are preferred. Preferred habitats are regulated lowland streams, clay- and sand-ditches, and clay- and sand-canals. H. obscurus has a clear preference for stagnant waters with a high pH, high conductivity and high chlorinity (but the optimum is lower than for H. lividus) with a luxurious vegetation of floating leaved and submerged plants. Preferred habitats are clay- and sand-ditches. H. punctatus has a very clear preference for waters with a low pH, low conductivity and low chlorinity. With respect to vegetation and type of current the species shows no significant preferences or aversions. Preferred habitats are moorland pools, peat-canals and peat-cuttings.     

Predator Generalization Decreases the Effect of Introduced Predators in the San Marcos Salamander,Eurycea nana

The introduction of novel predators into an environment can have detrimental consequences on prey species, especially if these species lack the ability to recognize these predators. One such species that may be negatively affected by introduced predators is the federally threatened San Marcos salamander (Eurycea nana). Previous research found that predator‐naïve (captive‐hatched) salamanders showed decreased activity in response to the chemical cues of both a native fish predator (Micropterus salmoides) and an introduced fish predator (Lepomis auritus), but not to a non‐predatory fish (Gambusia geiseri). We tested the hypothesis that E. nana recognized the introduced Lepomis (and other non‐native Lepomis) because they share chemical cues with other native congeneric Lepomis predators in the San Marcos River. We examined the antipredator response of predator‐naïve E. nana to chemical cues from (1) a sympatric native sunfish (Lepomis cyanellus; Perciformes: Centrarchidae); (2) a sympatric introduced sunfish (L. auritus); (3) an allopatric sunfish (Lepomis gibbosus); (4) a sympatric non‐native, non‐centrarchid cichlid (Herichthys cyanoguttatum; Perciformes: Cichlidae); and (5) a blank water control to determine whether individuals make generalizations about novel predators within a genus and across a family. Exposure to chemical cues from all fish predator treatments caused a reduction in salamander activity (antipredator response). Additionally, there were no differences in the antipredator responses to each predatory fish treatment. The similar responses to all sunfish treatments indicate that E. nana shows predator generalization in response to novel predators that are similar to recognized predators. Additionally, the antipredator response to H. cyanoguttatum indicates that predator generalization can occur among perciform families.     

Ethology and ecology of cichlid fishes of the genus Etroplus in Sri Lanka: preliminary findings

Synopsis The Asian cichlid fishes, Etroplus maculatus (Bloch) and E. suratensis (Bloch) were observed in their natural habitat. Ecological and behavioral interactions of these species have not been previously reported. E. suratensis benefits from being cleaned by E. maculatus; it is doubtful the ingestion of parasites and fungi is of much direct benefit to E. maculatus. The advantage to E. maculatus is more likely the survival and reproductive success of adult E. suratensis which in turn provide eggs and eleutheroembryos for the egg-young predatory habit of E. maculatus. Predation is lessened by age-specific crypticity of E. suratensis. E. maculatus displays a unique behavior during its parental cycle where both parents actively defend their young until they are nearly sexually mature and almost the size of the parents. Adult E. suratensis engage in altruistic multiple parental care where several adults care for a single brood that presumably were spawned by only two of the adults. Such behavior has not been reported previously for fish.     

Interactions between fish and salamander larvae

Summary Two species of salamander larvae (Ambystoma talpoideum and A. maculatum) were reared separately in the presence and absence of a fish (Lepomis macrochirus) in artificial ponds to measure the effects of a predator on the growth, survival, diet, and activity of larvae. The presence of L. macrochirus reduced body sizes of larvae by 18% in A. talpoideum and by 16% in A. maculatum. L. macrochirus apparently preyed on the smallest individuals. Survival in the presence of L. macrochirus decreased by 61% in A. talpoideum and by 97% in A. maculatum compared with larvae reared alone. Species identity did not significantly effect body size or survival, but an interaction effect suggested that A. maculatum was more severely affected by predators than was A. talpodeum. Activity of larvae in the water column was dramatically reduced in the presence of L. macrochirus, when larvae were restricted to the leaf litter of the benthic zone. There was overlap in the diets of fish and salamander larvae. Larvae reared in the presence of fish, however, consumed different taxa of prey as well as reduced number of prey compared to larvae reared alone. A. talpoideum larvae were more nocturnal than diurnal in the absence of fish, whereas A. maculatum larvae were equally active day and night. This experiment suggests that predator-prey relationships can change with shifts in species attributes and potentially confound apparent costs of predator avoidance with competition. Measuring the long-term dynamics of the cost-benefit relationship will help elucidate how prey balance the demands of their life history with the demands of predators.