The genus Perkinsiana (Polychaeta, Sabellidae) from Antarctica, with descriptions of the new species P. milae and P. borsibrunoi

Perkinsiana antarctica (Kinberg, 1867) and P. littoralis (Hartman, 1967) are redescribed from holo- and topotypes. Two new species, P. milae and P. borsibrunoi , are described from the Ross Sea (Antarctica) and compared with other species of the genus. Records of P. antarctica are numerous, but re-examination indicates that many of these represent misidentifications: the species may have a distribution limited to subantarctic areas.     

Coexistence between two fruit fly species is supported by the different strength of intra‐ and interspecific competition

1. Unravelling the strength and modes of interspecific interactions between resident and introduced species is necessary in order to understand the basis of their coexistence or the displacement of the former by the latter. In Argentina, the indigenous Tephritidae fly Anastrepha fraterculus overlaps its distribution and host fruit with the introduced species Ceratitis capitata. 2. This study focused on the relative strength of intra‐ and interspecific competition during the larval stage as a potential factor supporting coexistence. Classical competition experiments (addition and substitution) were conducted between larvae of the two species reared in artificial larval diet. The study evaluated whether a temporal separation between oviposition events affects the outcome of the competition. 3. When both species started to consume the resource at the same time, A. fraterculus experienced a negative effect in larval survival, pupal weight and duration of larval stage, while for C. capitata, pupal weight decreased. When A. fraterculus started feeding 1 day earlier than C. capitata, the negative effects became milder, and when the temporal separation increased, these effects were reversed. Substitution experiments showed an increase in pupal weight when larvae had to share the resource with heterospecific larvae, and showed negative effects suffered for both species when they shared the resource with conspecific individuals. 4. These results suggest that intraspecific competition is stronger than interspecific competition, and a differential oviposition preference could generate an asynchrony of these species in nature. Such mechanisms could favour coexistence between A. fraterculus and C. capitata in an environment previously occupied only by the former.     

The Zambezi River in Moçambique

SUMMARY. Surveys of the physico-chemical status of the River Zambezi in Moçambique were conducted between April 1973 and May 1974, to characterize the river prior to the closure of the Cabora Bassa Dam and to provide baseline data from which future changes in the river ecosystem can be followed. The temperature of the river water increases by about 3°C from Lake Kariba to the sea, and with an average pH of 7.8 the water is slightly more alkaline than Kariba Dam water. The river is well oxygenated with no sign of hydrogen sulphide. Transparency is generally very low and changes are mainly determined by the floods of local tributaries. The overall average total alkalinity is 55 mg 1^?1 CaCO₃, with no regular seasonal variation, average concentrations of chloride and sulphate are respectively, 5.4 mg 1^?1 Cl^? and 5.3 mg 1^?1 SO^2-₄. They increase under both the influence of the ionically rich Shire River and the sea; the latter due to vertical mixing. Total hardness and calcium hardness behave in a similar way, while conductivity and silica concentrations increase slightly until the Zambezi—Shire confluence, at which point, conductivity increases by 25% to an average peak value of 153 μS cm^?1, and silica decreases by 15% to a minimum average value of 15.5 mg 1^?1 SiO₂. Ammonia and nitrate concentrations show a clear seasonal variation, with respectively, minimum dry season and maximum wet season average values of about 0.05 mg 1^?1 and 0.3 mg 1^?1. The overall average concentration of nitrite is 0.004 mg 1^?1. Orthophosphate in the river is mostly affected by Lake Kariba, though other sources are also of some importance. Maximum average concentrations of about 0.4 mg 1^?1 PO^3-₄ were recorded during the dry season after the overturn of Lake Kariba. The concentration of dissolved metals is mainly determined by the outflow of Kariba and by the Shire River, with only K and Mg apparently affected by the outflow from Lake Kafue. It is concluded that the water quality of the Middle Zambezi is mainly determined by the Kariba Dam, with the Kafue Dam playing a minor role. At the time of the pre-impoundment survey, the main impact on water quality of the Lower Zambezi came from the Shire River. With the addition of yet another large reservoir on the Zambezi, in the form of Cabora Bassa, together with the appreciable effect of tributary rivers on the lake, and the likely increased impact of the Shire River on the now more regulated river, the quality of the Lower Zambezi is expected to alter considerably, with concomitant ecological changes.     

Phylogeny and feeding trait evolution of the mega‐diverse Gelechioidea (Lepidoptera: Obtectomera): new insight from 19 nuclear genes

The Gelechioidea (>18 000 species), one of the largest superfamilies of Lepidoptera, are a major element of terrestrial ecosystems and include important pests and biological model species. Despite much recent progress, our understanding of the classification, phylogeny and evolution of Gelechioidea remains limited. Building on recent molecular studies of this superfamily and a recently revised family/subfamily classification, we provide an independent estimate of among‐family relationships, with little overlap in gene sample. We analysed up to five nuclear genes, totalling 6633 bp, for each of 77 gelechioids, plus up to 14 additional genes, for a total of 14 826 bp, in 45 of those taxa and all 19 outgroup taxa. Our maximum‐likelihood (ML) analyses, like those of previous authors, strongly support monophyly for most multiply‐sampled families and subfamilies, but very weakly support most relationships above the family level. Our tree looks superficially divergent from that of the most recent molecular study of gelechioids, but when the previous tree is re‐rooted to accord maximally with ours, the two phylogenies agree entirely on the deepest‐level divergences in Gelechioidea, and strongly though incompletely on among‐family relationships within the major groups. This concordance between independent studies is evidence that the groupings (or at least the unrooted branching order) are probably accurate, despite the low bootstrap values. After re‐rooting, both trees divide the families into three monophyletic groups: a ‘Gelechiid Assemblage,’ consisting of Gelechiidae and Cosmopterigidae; a ‘Scythridid Assemblage,’ consisting of Stathmopodidae, Scythrididae, Blastobasidae, Elachistidae, Momphidae, Coleophoridae and Batrachedridae; and a ‘Depressariid Assemblage,’ consisting of Autostichidae, Xyloryctidae, Lecithoceridae, Oecophoridae, Depressariidae and Lypusidae. Within the largest family, Gelechiidae, our results strongly support the pairing of Anomologinae with Gelechiinae, in accordance with a recent study of this family. Relationships among the other subfamilies, however, conflict moderately to strongly between studies, leaving the intrafamily phylogeny unsettled. Within the ‘Scythridid Assemblage,’ both trees support an ‘SSB clade’ consisting of Blastobasidae + (Scythrididae + Stathmopodidae), strongly resolved only in our results. Coleophoridae + Batrachedridae is supported, albeit weakly, in both trees, and only Momphidae differ in position between studies. Within the ‘Depressariid Assemblage,’ both trees support an ‘AXLO’ clade consisting of Autostichidae, Xyloryctidae, Lecithoceridae and Oecophoridae. The monophyly of this clade and relationships therein are supported weakly in previous results but strongly in ours. The recently re‐defined family Depressariidae is paraphyletic in our tree, but the evidence against depressariid monophyly is very weak. There is moderate support for a core group of Depressariidae consisting, among the seven subfamilies we sampled, of Depressariinae, Aeolanthinae and Hypertrophinae. We show that gelechioids have a higher total number and percentage of species that are saprophagous as larvae than any other apoditrysian superfamily, that saprophagy is concentrated primarily in the ‘AXLO clade,’ and that the ancestral gelechioid condition was probably feeding on live plants. Among the living‐plant feeders, concealed external feeding was probably the ancestral state. The multiple origins of internal feeding of various kinds, including leaf mining (otherwise almost unknown in Apoditrysia), are restricted mostly to the Scythridid and Gelechiid Assemblages. The traits that predispose or permit lineages to adopt these unusual life histories are worthy of study.     

Construction of a Normalized cDNA Library for the Trypanosoma cruzi Genome Project

Sequencing of the Trypanosoma cruzi genome is underway. Expressed sequence tags, obtained from cDNA libraries, facilitate mapping and gene discovery. The efficiency of large-scale generation of such tags is increased when using normalized cDNA libraries, where the frequency of individual clones is brought within a narrow range. Repetitive sequencing of abundant clones is therefore minimized. We constructed a normalized cDNA library from epimastigotes of clone CL Brener, and the efficiency of normalization of representative clones was assessed and shown to be adequate. The normalized cDNA library has been distributed to several groups and large-scale sequencing is currently in progress.     

Host refuges and spatial patterns of parasitism in an endophytic host–parasitoid system

Abstract. 1. Larvae of Tephritis conura Loew (Diptera: Tephritidae) live gregariously in flower heads of Cirsium heterophyllum (L.) Hill (Cardueae). They are attacked by the endoparasitic wasps Eurytoma sp. near tibialis Boheman (Hymenoptera: Eurytomidae) and Pteromalus caudiger (Graham) (Hymenoptera: Pteromalidae).
2. The responses of the parasitoids to different host patch sizes were investigated from the analysis of field samples. At the host population level, overall probabilities of parasitism were independent of host numbers per flower head or showed a tendency to inverse density-dependence for both parasitoid species.
3. Measurements of ovipositor length in Eurytoma and P.caudiger indicated that parts of the flower head constitute a structural refuge from parasitism.
4. The accessibility of hosts in a flower head was found to differ markedly, depending on larval locations and flower head characters. In spite of this high variability, similar average percentages of larvae were accessible to the parasitoids in each patch size class.
5. High variability of oviposition success in laboratory experiments can be explained by random locations of hosts in the flower heads.