The distribution of stream-dwelling triclads (Platyhelminthes) in North Wales

This paper presents information collected during a survey of stream-dwelling triclads in two CO ntrasted areas of North Wales. The first study area was located in Caernarvon-shire on the mainland of North Wales and included a mountainous region rising to over 1000 m with abundant cold springs. In contrast, the study area on the nearby island of Anglesey was characterized by relatively warm, slow-flowing streams passing through gently undulating land which did not rise above 153 m. The object of the survey was to collect background data so that suitable streams could be chosen for more intensive studies on factors determining the distribution and abundance of stream-dwelling triclads. Distribution maps for the commonly occurring species were prepared and observations on the relationship between stream source-type and triclad fauna were obtained. The possible role of interspecific competition was of particular interest in this study and the results of this second phase of the work will be presented in a later paper.     

The fossil record of Eucommia (Eucommiaceae) in North America

Reproductive and vegetative remains of Eucommia from 25 localities in the United States, Canada, and Mexico document the wide distribution of this genus in North America during the Cenozoic. Autofluorescent elastic latex filaments bearing capitate termini are preserved in nearly all of the remains and provide conclusive evidence of their affinity to Eucommia. Four species of Eucommia are recognized on the basis of the characteristic samaras: E. eocenica from middle Eocene strata of the Mississippi Embayment in Missouri, Tennessee and Mississippi; E. montana from early Eocene to early Oligocene localities in British Columbia, Washington, Oregon, Utah, Colorado, and Montana; E. constans from Neogene rocks in central Mexico; and E. jeffersonensis n. sp. from the latest Eocene or earliest Oligocene John Day Formation of Oregon. Atypical specimens of E. montana and E. eocenica are the first records of two-seeded fruits for the genus. Eucommia leaves from Eocene localities in British Columbia and Mississippi are the first records of Eucommia foliage in North America whose identifications are confirmed by the presence of capitate latex strands. These leaves and a specimen from Oregon are referred to E. rolandii n. sp. Fruit evolution in Eucommia may have involved increases in samara size and symmetry, and reduction in seed number from two to one, perhaps as adaptations for wind dispersal. All fossil Eucommia samaras from North America are smaller and less symmetrical than those of the living species, E. ulmoides. Preliminary flight tests of E. ulmoides samaras and of models of the fossils suggest that E. ulmoides fruits are aerodynamically better suited for wind dispersal than the fossils.     

The occurrence of nitro-toxins in North American astragalus (Fabaceae)

Leaves from herbarium specimens of 505 species and varieties of North AmericanAstragalus were examined for the presence of organic nitro-toxins. The relative concentration of these nitro compounds was determined for the 263 nitro-containing species and varieties. Chemotaxonomic relationships existed among many species so that the presence, molecular configuration, and concentration of the nitro-toxins in the species examined could be used to predict the occurrence of these toxins in other taxa. Geographic differences were also noted for varieties of one species,A. robbinsii (Oakes) A. Gray.     

The North East Water polynya (Greenland Sea)

Physical observations of the North East Water (NEW) polynya, located near the north-eastern corner of Greenland, are presented. Data were collected in June 1991 by RV Polarstern. An idea is put forward to explain how the NEW is generated. A northward coastal current interacts with a persistent shelf ice barrier under which water can flow but that retains ice floes and therefore protects the NEW area from ice advection. Since in summer, the combination of currents, barrier and air-sea heat balance gives rise to a polynya. The distribution of upper water column vertical stability in the NEW is also influenced by its generation process. Surface melt water is retained by the shelf ice barrier, causing neutral vertical stability in its lee. Sea ice melting and land runoff then act as two distinct sources of vertical stability enabling the development of plankton blooms, especially in the northern part of the NEW.     

Bergmann's rule and the mammal fauna of northern North America

The observation that "on the whole…  larger species live farther north and the smaller ones farther south" was first published by Carl Bergmann in 1847. However, why animal body mass might show such spatial variation, and indeed whether it is a general feature of animal assemblages, is currently unclear. We discuss reasons for this uncertainty, and use our conclusions to direct an analysis of Bergmann's rule in the mammals in northern North America, in the communities of species occupying areas that were covered by ice at the last glacial maximum. First, we test for the existence of Bergmann's rule in this assemblage, and investigate whether small- and large-bodied species show different spatial patterns of body size variation. We then attempt to explain the spatial variation in terms of environmental variation, and evaluate the adequacy of our analyses to account for the spatial pattern using the residuals arising from our environmental models. Finally, we use the results of these models to test predictions of different hypotheses proposed to account for Bergmann's rule. Bergmann's rule is strongly supported. Both small- and large-bodied species exhibit the rule. Our environmental models account for most of the spatial variation in mean, minimum and maximum body mass in this assemblage. Our results falsify predictions of hypotheses relating to migration ability and random colonisation and diversification, but support predictions of hypotheses relating to both heat conservation and starvation resistance.     

The native subspecies of Juncus effusus (Juncaceae) in western North America

Juncus effusus s. str. has two native representatives on the coast of western North America. A new combination is provided forJuncus effusus subsp.pacificus, ranging from California to British Columbia.Juncus effusus subsp.austrocalifornicus is newly described from southernmost California, Arizona, and Baja California, México. It differs from subsp.pacificus by its pale sheaths, with less thickened and less overlapping margins, and its disjunct distribution. A key is provided for the subspecies ofJ. effusus in North America.     

The reproductive biology of Stellaria longipes Goldie (Caryophyllaceae) in North America

Stellaria longipes is a very variable species of circumpolar distribution and wide ecological amplitude. Individuals are herbaceous, perennial, and facultative outbreeders. Gynodioecy is very common. We studied the microsporogenesis and embryo development in both male sterile and male fertile genotypes. Male sterile plants are vigorous and set more seed than the bisexual genotypes.     

The distribution of entomophilic nematodes (Heterorhabditidae and Steinernematidae) in North Carolina

Over 500 samples of soil from cropland, vineyards, orchards, pasture, and forest habitats throughout North Carolina were tested for the presence of steinernematid and heterorhabditid nematodes by baiting with Galleria mellonella larvae. Nematodes were isolated from 13 of 14 locations and from each habitat. Heterorhabditids (Heterohabditis heliothidis) were most commonly found (13 locations) with Steinernema (= Neoaplectana) glaseri, S. feltiae (= Neoaplectana carpocapsae), and an undescribed Steinernema species being found at one or two locations. The primary form of the bacterial symbiont of S. glaseri was isolated for the first time.     

Juncus planifolius (Juncaceae) in North America

Juncusplanifolius is reported for the first time from North America. Bibliographic notes on this species and its synonymy are given. Its distribution, dispersal and relationships within the genus are discussed.     

Simuliidae (Diptera) of Sabah (British North Borneo)

This paper is based on collections made in Sabah by John Smart and on an examination of named material (types) in the British Museum (Natural History), London.
Segregates discussed comprise:(1) six new species, (2) five named species from the area, described by the late F. W. Edwards (1933).