Elasmobranchs from the Lower Triassic Sulphur Mountain Formation near Wapiti Lake (BC, Canada)

Hybodontoid and nonhybodontoid sharks are described from the Lower Triassic Vega‐Phroso Siltstone Member of Sulphur Mountain Formation on the basis of newly discovered material. The age of the classic fossil site ‘Wapiti Lake’ in the Canadian Rocky Mountains is discussed on the basis of new field data and one conodont found in association. Preliminary results suggest that these elasmobranch remains are between early Smithian and Spathian in age. Apart from the enigmatic genus Listracanthus and previously reported edestoids, the shark fauna consists of at least one hybodont, at least two questionable hybodontoid genera and an elasmobranch of enigmatic affinities, represented by peculiar denticles only and described as ‘genus A’incertae sedis. The presence of the only previously reported hybodont genus, cf. Palaeobates, is erroneous. The largest specimen represents the most complete Early Mesozoic shark known. The heterodonty of its dentition, fin spine morphology and the short, robust body shape imply it represents a member of a new family of shark, Wapitiodidae fam. nov. , and is described here as Wapitiodus aplopagus gen. et sp. nov. The unique dental morphology shows affinities to Polyacrodus but clearly differs in the complete lack of side cusps. Wapitiodus gen. nov. possesses a primitive fin spine structure. The tooth crowns are entirely blunt in the distal (posterior) tooth files, and are acuminate‐unicuspid in several anterior files. Tooth morphology, the shape of the basal cartilages, the proximal insertion of the fin spines and the pectoral fin structure are interpreted as diagnostic characters for this new genus, and possibly for the Wapitiodidae fam. nov. The majority of observed characters appear to be primitive and are reminiscent of Palaeozoic sharks, however, and these features include dorsal fin spine morphology and gross skull anatomy. A second species, provisionally placed in the same genus, is described as Wapitiodus homalorhizo sp. nov. Wapitiodus homalorhizo sp. nov. can be distinguished from W. aplopagus gen. et sp. nov. by the proportions of the fin spines, tooth morphology and possibly the body shape. Several isolated teeth and other fragmentary material are referred to either Wapitiodus gen. nov. sp. indet. or to ?Polyacrodus sp. (Polyacrodontidae gen. et sp. indet.). A third genus of elasmobranch (incertae sedis) is described as ‘Genus A’ and is recognized by its peculiar scales. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149 , 309–337.     

Contributions to the Cytotaxonomy of the Commelinaceae. Gibasis linearis and its allies

Species of the Gibasis linearis alliance collected in Mexico in 1976 are shown to have a chromosome constitution of x = 6, but x = 5 has also been found in some populations of G. rhodantha and G. speciosa. These two basic numbers are associated with distinctive karyotypes, 2M + 4A and 3M + 2A respectively, which show a Robertsonian relationship with each other. The existence of 2n = 22 in G. speciosa , combining both basic numbers at the amphidiploid level provides evidence of pairing between metacentrics and acrocentrics in such a way as to substantiate the view that fusion or fission of chromosomes is responsible for the modification of basic number. This survey provides a basis for other studies which will determine the chromosome relationships of the species irrespective of chromosome number in this family.     

Inferring origins of migrating insects using isoscapes: a case study using the true armyworm,Mythimna unipuncta,in North America

1. Many important insect pests undertake seasonal migrations at continental scales in response to changes in resource quality and availability. The frequency and timing of these events could be influenced by the impact of climate change on the suitability of the different sites exploited throughout the year, yet, in many cases, little is known about the origin of seasonal populations, as tracking insect movements is extremely challenging due to their small body size. 2. The use of stable isotope measurements in insect tissues combined with the development of tissue‐specific ‘isoscapes’ of modelled geographic isotope patterns presents a potentially valuable but rarely used approach for obtaining such information on important pest species. In this paper it is illustrated how stable hydrogen isotope analyses (δ²H) in wing chitin of the true armyworm (Mythimna (Psuedaletia) unipuncta Haworth), a seasonal migrant, clearly delineated between 2016 spring immigrants and later locally produced moths in southern Ontario, Canada. 3. It is shown that adult moths captured in early fall in Texas were immigrants from farther north, the first direct confirmation of a southward return migration of this species. Stable carbon isotope (δ¹³C) measurements indicated that spring immigrants in Ontario and autumn immigrants in Texas were from exclusively C3 biomes. Stable nitrogen isotope (δ¹⁵N) measurements also provided information on the probability of individuals coming from agriculturally intensive (i.e. higher δ¹⁵N) sites. Finally, several recommendations are provided regarding future research that could improve the Bayesian assignment models and thus improve assignment accuracy.     

Comparison of gas use efficiency and treatment uniformity in a forest ecosystem exposed to elevated [CO2] using pure and prediluted free-air CO2 enrichment technology

A direct comparison of treatment uniformity and CO₂ use of pure and prediluted free-air CO₂ enrichment (FACE) systems was conducted in a forest ecosystem. A vertical release pure CO₂ fumigation system was superimposed on an existing prediluted CO₂ fumigation system and operated on alternate days. The FACE system using prediluted CO₂ fumigation technology exhibited less temporal and spatial variability than the pure CO₂ fumigation system. The pure CO₂ fumigation system tended to over-fumigate the upwind portions of the plot and used 25% more CO₂ than the prediluted CO₂ fumigation system. The increased CO₂ use by the pure CO₂ system was exacerbated at low wind speeds. It is not clear if this phenomenon will also be observed in plots with smaller diameters and low-stature vegetation.     

Testing a facilitation model for ecosystem restoration: Does tree planting restore ground layer species in a grassy woodland?

Planning for the restoration of degraded ecosystems has a strong basis in facilitation successional theory, which, as applied in restoration practice, states that planting of structurally dominant tree species will assist the entry of other native species into a restored community. In Australia, tree planting has been widely applied in restoration of grassy woodland ecosystems. Trees have been postulated to reduce the cover and diversity of weed species, thus facilitating recolonization of native woodland species (indirect facilitation). The expected outcomes of this process include reduced species richness and abundance of exotic plant species and increased species richness and abundance/dominance of natives in areas beneath tree canopies, with these trends strengthening with time. To assess whether this was occurring, we carried out a comparative analysis of species assemblages found underneath and outside of planted tree canopies in sites replanted with juvenile canopy tree species 3–5 or 8–10 years previously. We sampled revegetated stands of Cumberland Plain Woodland, an endangered ecological community in Western Sydney, Australia. We found that neither the number nor abundance of native ground layer species beneath canopies increased as a result of trees being planted at sites of both ages. Where seed is limited, we predicted an increase in abundance of existing native species under planted tree canopies. On this point, the results were mixed and showed some natives with an increased abundance while others decreased. Exotic species richness showed the reverse of the expected pattern, being greater under tree canopies. These findings lend no support to the theory of indirect facilitation. We conclude that simple facilitation models may be inadequate to support planning of grassy woodland restoration and that those models incorporating successional time lags and restoration barriers are likely to be more informative about the development of communities initiated by tree planting.     

Phylogeography of the North American red fox: vicariance in Pleistocene forest refugia

Fossil, archaeological, and morphometric data suggest that indigenous red foxes in North America were derived from vicariance in two disjunct refugia during the last glaciation: one in Beringia and one in the contiguous USA. To test this hypothesis, we conducted a phylogeographical analysis of the North American red fox within its presettlement range. We sequenced portions of the mitochondrial cytochrome b (354 bp) gene and D-loop (342 bp) from 220 historical red fox specimens. Phylogenetic analysis of the cytochrome b gene produced two clades that diverged c . 400 000 years before present ( bp ): a Holarctic and a Nearctic clade. D-loop analyses of the Nearctic clade indicated three distinct subclades (≥ 99% Bayesian posterior probability); two that were more recently derived (rho estimate c . 20 000 bp ) and were restricted to the southwestern mountains and the eastern portion of North America, and one that was older (rho estimate c . 45 000 bp ) and more widespread in North America. Populations that migrated north from the southern refugium following deglaciation were derived from the colonization of North America during or prior to the Illinoian glaciation (300 000–130 000 bp ), whereas populations that migrated south from the northern refugium represent a more recent colonization event during the Wisconsin glaciation (100 000–10 000 bp ). Our findings indicate that Nearctic clade red foxes are phylogenetically distinct from their Holarctic counterparts, and reflect long-term isolation in two disjunct forest refugia during the Pleistocene. The montane lineage, which includes endangered populations, may be ecologically and evolutionarily distinct.     

The genetic structure of swarms and the timing of their production in the queen cycles of neotropical wasps

Kin selection theory has received some of its strongest support from analyses of within-colony conflicts between workers and queens in social insects. One of these conflicts involves the timing of queen production. In neotropical wasps, new queens are only produced by colonies with just one queen while males are produced by colonies with more queens, a pattern favoured by worker interests. We now show that new colonies, or swarms, have few queens and variable within-colony relatednesses which means that their production is not tied to new queen production. The queens in these swarms are seldom the mothers of the workers in the swarm. Therefore, either colonies producing swarms have very many queens, or queens joining daughter swarms are reproductive losers on the original colonies. As new colony production is not linked to queen production, it can occur at the ecologically optimum time, i.e. the rainy season. This disassociation between queen production and new colony production allows worker interests in sex ratios to prevail without hampering new colony production at the most favourable season, an uncoupling that may contribute to the ecological success of the Epiponini.