Comparative genet survival after fire in woody Mediterranean species

Summary Using data from three fires in northeastern Spain, we tested a condition necessary to support the idea that fire has been a factor in the evolution of the resprouting habit: populations of all resprouting species within a community should show high levels of genet survival after fires and show a low coefficient of variation. Species with high mean survival values were:Quercus ilex L.,Phillyrea latifolia L., andViburnum tinus L., with 88, 86 and 83% survival respectively; these groups had resprouts emerging from rootcrowns. Then followedArbutus unedo L. (75%),Pistacia lentiscus L. (73%),Erica arborea L. (77%),Erica multiflora L. (57%) andJuniperus oxycedrus L. (55%). This last group had resprouts from lignotubers or burls. These two groups also differed in the variability around the mean: the first showed a lower coefficient of variation, 6–12, and the second ranged from 19 to 26. Slope exposure had no significant influence on the process of resprouting, but soil depth did, with precipitation as a covariate. In the shallow soil category, the difference in genet survival between southern and northern exposures was 14% (71% vs. 57%); while the difference in the deep soil category was low, 5% (87% vs. 82%). There was no significant interaction. The component of variance for soils was larger than that for species-specific effects; substantial overlap of the within-species variance indicated that species responded as if they were a single hypothetical population, in which most of the variation in chances of survival was due to the soil conditions. The possession of the resprouting habit did not ensure a high performance. Hence, we find weak support for fire as a factor in the evolution of the resprouting habit.     

Effect of methabenzthiazuron on growth and nitrogenase activity in Vicia faba

The effects of the herbicide methabenzthiazuron (175 and 220 g ha^-1) on vegetative and reproductive growth, nodulation and nitrogenase activity of Vicia faba were studied in the field under Mediterranean conditions. Nitrogenase activity of excised nodules was estimated using the acetylene reduction assay four times during the developmental period. Leaf area index, dry weight and nitrogen content of the different parts of the plants were measured. Methabenzthiazuron-treated plants showed an increase in nodulation, nitrogenase activity and vegetative growth at early pod fill. Methabenzthiazuron also caused an increase in leaf N content and fruits. These were transient effects found during early and mid pot fill. Nevertheless, plants treated with these sublethal doses of herbicide improved seed production and nitrogen content of seeds at harvest time. The stimulatory effect of methabenzthiazuron on N₂ fixation and vegetative growth seems not be related with the transient stimulatory effect on photosynthetic capacity, also caused by the herbicide, since the stimulatory effect on N₂ fixation was apparent during pod fill, when photosynthetic capacity declined and was not modified by methabenzthiazuron.     

Comparative water relations of four Mediterranean oak species

The water relations and responses of two evergreen (Quercus ilex L. and Q. suber L.) and two deciduous (S. afares Pomel. and Q. faginea Will.) Quercus species were studied under experimental conditions. Two-year old seedlings grown in 30 l. pots were subjected to a drying period during which stomatal conductance, pre-dawn potential and minimum foliar potential were measured.The results shows that, for all species, the daily course of stomatal conductance agrees with the patterns proposed by Hinckley et al. (1978 & 1983). Concurrent with the species responses to short-term variation in water availability, it was found that pre-dawn leaf water potential controlled the maximum daily leaf conductance. There was a strong correlation between pre-dawn leaf potential and maximum daily conductance as described by the reciprocal function g_{srmax for}=(-0.47+2.61._p)^-1 the evergreen oaks and g_{srmax for}=(-1.94+7.39._p)^-1 for the deciduous species. These differences between the two groups may partialy explain their geograhic distributions, and suggest general questions concerning the mechanisms which optimize water-use efficiency in Mediterranean oak species.     

The effect of trophic/contaminant interactions on chironomid community structure and succession (Diptera: Chironomidae)

The effects of contaminants and organic pollution on the chironomid communities of two basins in Lac St. Louis, a river-lake on the St. Lawrence River above Montreal, Quebec, were assessed and compared using lake classification theory techniques and morphological deformity indices based on the ligulae and antennae ofProcladius, the dominant surviving component of the south-shore communities. Contaminants from the industrial complex around Beauharnois, Quebec, have seriously degraded communities along the south-shore gradient while the introduction of untreated domestic wastes from Laprairie, Quebec, has seriously affected the communities of the Laprairie basin. The interaction between trophic and contaminant effects constitutes a classic example of the setback or deflection in the trajectory of ecological succession in biological communities hypothesized by ODUM (1981, 1985).     

Dynamics of distribution in animal communities: Theory and analysis

Theoretical and analytical problems of the dynamics of distribution and abundance in animal communities were examined. In many communities, species with low abundance and of limited spatial occurrence (i.e., rare species) typically form a conspicuous peak when a frequency distribution of the number of species is constructed with respect to the proportion of sites occupied within an area of distribution. Models of distribution dynamics, including a new model proposed here, were compared with a range of animal community data using a new procedure to assess single- and bi-modal patterns in frequency distributions of spatial occurrence. Data reveal that single-modality with an excess of rare species occurs more frequently than bimodality. Even when bimodality is detected, the mode representing wide-spread species is in the majority of cases smaller than that for rare species. Thus, a new model in which the rate of local extinctions is assumed to be negatively related to patch occupancy (or population abundance) is in better agreement with observed data than earlier models. Some problems of analysis, in particular model assumptions and testing, are discussed.     

Mass rearingCeratitis capitata: reuse of the finisher larval diet

The standard finisher larval diet used at Seibersdorf for rearing the Mediterranean fruit fly,Ceratitis capitata (Wiedemann), was reused following autoclave heat-treatment to kill larvae or pupae remaining from its first use. Only when the spent diet was mixed with water (about 40% of final diet, w/w) to reconstitute fresh-diet texture, and combined with fresh starter, a similar, but still inferior in respect to larval duration and pupal recovery and size, to the fresh finisher diet production of flies was achieved. Enrichment of the autoclaved spent finisher with small quantities of nutrients gave inconclusive results. Although spent-diet pupae were significantly smaller than fresh-diet control pupae, their adults survived significantly longer than control adults.

---

Zur massenaufzucht vonCeratitis capitata: die wiesderverwendung der endkomponente der larvendiät

Zusammenfassung Die in Seibersdorf zur Aufzucht der Mittelmeerfruchtfliege,Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), verwendete Standardendkomponente der Larvendiät konnte nach Abtötung der von der Erstverwendung verbliebenen Larven oder Puppen mittels Autoklavensterilisation wiederverwendet werden. Eine zur frischen Kontrolldiät vergleichbare, jedoch bezüglich der Länge des Larvenstadiums, der Entwicklung der Puppen nach dem Schlüpfen sowie der Größe der Puppen noch immer schlechtere Fliegenproduktion wurde erreicht, wenn die wiederverwendete, autoklavierte Diät mit Wasser (ca. 40% der Enddiät, w/w) zwecks Rekonstitution zur frischen Diättexture gemischt und mit frischem Starter kombiniert wurde. Eine Anreicherung der wiederverwendeten Diätendkomponente mit geringen Mengen von Nährstoffen ergab keine schlüssigen Resultate. Obwohl Puppen der wiederverwendeten Diät signifikant kleiner als Puppen der Frischdiät-Kontrolle waren, überlebten deren Erwachsene signifikant länger als die Erwachsenen der Kontrolle.

     

Ornithochory and plant succession in mediterranean abandoned orchards

Data on the occurrence of species with fleshy diaspores and on breeding birds were collected in three abandoned orchards, resp. 8, 11 and 24 years after abandonment. Most of the 41 phanerophytes and vines with fleshy diaspores are also found in the borders of the orchards, the more so if the number of years since abandonment increases. Most species have small seeds and red or black coloured diaspores, most of which ripen in autumn. The frequent species show a characteristic distribution pattern in relation to the distance of the fruit trees: high densities near the trunk and uniform decrease with distance. This is explained by the behaviour of frugivorous birds. No correlation was found between distribution patterns and soil conditions. Age structure of colonizing species shows a distribution conforming an inversed J curve in the more recently abandoned orchard. The main conclusions are:

1. Pioncor trees are attractive for frugivorous birds and may act as nuclei. This supports the facilitation model.
2. The distribution of diaspores by birds helps to homogenize the species distribution on the regional level but at the site level individual differences in nucleation cause a heterogeneity.

     

Brachiopod community paleoecology, paleobiogeography, and depositional topography of the Devonian Onondaga Limestone and correlative strata in eastern North America

The Emsian? through early Eifelian Onondaga Limestone of the Appalachian Basin was deposited in a topographic basin and on the carbonate platform which surrounded the basin on the west, north, and northeast. Onondaga strata thin from the platform into the basin. Two sedimentary cycles are present in the sub-Tioga Onondaga of eastern North America. The Edgecliff-Amherstburg represents an interval of transgression, in which epeiric seas spread over much of eastern North America. During the Nedrow-Lucas regression, the interior of the carbonate platform became restricted, resulting in the deposition of evaporites. The Moorehouse-Anderdon transgression continued through the deposition of the Tioga Bentonite, followed by the pre-Speeds-Dundee regression from the craton. Early Eifelian Appalachian Basin Onondaga brachiopod communities, arranged from nearshore to offshore, include the Atrypid-Megakozlowskiella, Atrypid-Levenea, Chonetid, Atlanticocoelia, Ambocoeliid, and Truncalosia Communities. The Onondaga-age Eastern Americas Realm is divided into the Appohimchi Province in the Appalachian Basin and the Michigan Basin-Hudson Bay Lowland Province in the Midwest. The provincial assignment of the James Bay region of Ontario is uncertain; the Eastern Townships of Quebec are near the boundaries both of the two provinces of the Eastern Americas Realm, and of the Eastern Americas Realm and the Old World Realm, the latter realm being probably in the Canadian Maritime Provinces.     

Factors influencing the distributional abundance of two trophic guilds of Peruvian cricetid rodents

The distributional abundance of 13 species of southern Peruvian rodents is significantly correlated with altitude and patterns of vegetation but vegetation is a better predictor than altitude. Coincidental reversals in the altitudinal trends of both vegetation and rodents demonstrate that rodents are responding to vegetation patterns. Abundance and diversity of rodents are greatest around 4000 m elevation which coincides with the region of greatest vegetational abundance and seasonally heavy rainfall.
The rodent communities consist of two separate feeding guilds, omnivores and insectivores and these guilds show distinctly different distributional patterns. Insectivorous species are strongly associated with the zone of seasonally heavy rainfall (4000 m) whereas omnivorous rodents are relatively abundant over a broader spectrum of elevations and habitats. In a previous study of these same communities, we showed a correspondence between rodent morphology and their diets. This study reveals a correspondence between distributional abundance of the various species and their diets. We conclude that the distributional abundance of southern Peruvian rodents is related to the physiological constraints imposed by altitude (climate) and the distributional abundance of food resources.