Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.      

Mycotoxins of Alternaria alternata produced on ceiling tiles

The production of mycotoxins by Alternaria alternata in cellulosic ceiling tiles was examined with thin-layer chromatography and high-performance liquid chromatography procedures. Alternariol and alternariol monomethyl ether were found in ceiling tile extracts, whereas extracts of control rice cultures of all three isolates produced these mycotoxins plus altenuene and altertoxin I. Extensive fungal growth and mycotoxin production occurred in the ceiling tiles at relative humidities of 84–89% and 97%. Received 28 May 1997/ Accepted in revised form 06 October 1997     

Sympatric cryptic species in New Zealand Onychophora

Allozyme electrophoresis was used to examine genetic diversity within live-bearing Peripatopsid Onychophora from the North Island of New Zealand. Specimens of two previously described morpho-species that differ in leg number (Peripatoides suteri and P. novaezealandiae) were found to be genetically diverse. P. suteri showed little intraspecific genetic variation but were very distinct from specimens assignable to P. novaezealandiae. Within P. novaezealandiae five genetically differentiated species were identified although none showed any consistent morphological differentiation, thus P. novaezealandiae (Hutton) is a species complex. All of these species occur in sympatry or parapatry (in one instance) with other cryptic species of the P. novaezealandiae group or with P. suteri. Four new species are described on the basis of this genetic evidence, they are P. morgani, P. aurorbis, P. kawekaensis and P. sympatrica. Other genotypes encountered indicate further cryptic species remain unrecognized. Among the North Island species, P. suteri and P. aurorbis sp. nov. are both more closely related to undescribed species from the South Island than to others examined from the North Island. P. sympatrica sp. nov. exists in sympatry with at least three other species in different parts of its range. The complexity of relationships and distributions probably arose through the interaction of low vagility in peripatus and the active geophysical history of the region. How these cryptic species persist in sympatry is not known but may be linked to differences in ecology not evident in their morphology, and/or may indicate recent dispersal from allopatry.     

Water Flow in Wheat Seedlings after Small Water Deficits

Cultures of Scenedesmus obliquus when grown heterotrophically for 10 or 30 days without addition of fresh medium showed 85 and 98% loss of their photosynthetic capacity respectively. This loss in photosynthetic capacity was accompanied by an increase in quantum requirement. No major changes in the pigment amounts or types were detected which would explain the decay in photosynthetic capacity. Partial reactions mediated by photosystem II or I showed a more or less constant decay over a period of 30 days. Photosystem II reactions appeared less stable than those of photosystem I, decaying by 95% as compared with 70%, over this time period. The results of comparative studies on aged cells for their potential of cytochrome f photooxidation, fluorescence kinetics, 520 nm absorbance change and the variable influence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone on the photosynthetic capacity of such cells, suggest that it is the inherent ability of the cells to photooxidize plastohydroquinone which is affected primarily. In addition, secondary changes were noted in the activity of reactions on the water-splitting side of photosystem II and in the P700 — plastocyanin — cytochrome f complex.     

Phylogenetic topology and timing of New Zealand olive shells are consistent with punctuated equilibrium

The olive shells of the genus Amalda comprises readily recognized species of marine neogastropod mollusks found around the world. The New Zealand Amalda fauna has particular notoriety as providing one of the best demonstrations of evolutionary morphological stasis, a prerequisite for punctuated equilibrium theory. An excellent fossil record includes representation of three extant endemic Amalda species used to explore patterns of form change. However, the phylogenetic relationship of the New Zealand Amalda species and the timing of their lineage splitting have not been studied, even though these would provide valuable evidence to test predictions of punctuated equilibrium. Here, we use entire mitogenome and long nuclear rRNA gene cassette data from 11 Amalda species, selected from New Zealand and around the world in light of high rates of endemicity among extant and fossil Amalda. Our inferred phylogenies do not refute the hypothesis that New Zealand Amalda are a natural monophyletic group and therefore an appropriate example of morphological stasis. Furthermore, estimates of the timing of cladogenesis from the molecular data for the New Zealand group are compatible with the fossil record for extant species and consistent with expectations of punctuated equilibrium.     

海洋浮游藻类细胞质膜氧化还原活性与细胞外CA活性的关系

海洋浮游藻类除通过吸收和释放分子与离子来改变其环境的化学成分外,还可通过细胞外表面一些酶的作用引起质膜外化学物质变化。在这方面,海洋浮游藻类一个主要的细胞外表面酶-碳酸酐酶(CA),在经胰蛋白酶处理从细胞质膜上释放出来后,仍保留其催化活性。当细胞外表面CA(简称细胞外CA)具活性时,可催化质膜外HCO_3~-与CO_2的相互转化,为Rubisco(磷酸核酮糖羧化酶)提供一稳定的CO_2流量环境,以维持正常的光合作用。     

Hello New Zealand

Islands of the Pacific Ocean have long fascinated evolutionists. Oceanic islands, generally the products of volcanic activity, provide natural experiments as biological populations are well delimited and the age of islands can be determined using radiometric dating. 'Continental islands', including New Caledonia and New Zealand, provide equally valuable opportunities for evolutionary study. For students of New Zealand biogeography, the peculiar composition of the biota coupled with a limited interpretation of geology has resulted in the widespread acceptance that the flora and fauna is primarily ancient and of vicariant Gondwanan origin. There is increasing evidence from molecular data that much of this biodiversity is the product of evolution following relatively recent colonization. Such data have prompted biologists to consider geological information on New Zealand in more detail. At the heart of the issue is the question of whether modern New Zealand has a terrestrial link through time with the continent Zealandia that split from Gondwanaland some 80 Ma. Zealandia, which includes New Caledonia, Lord Howe Island and several of the subantarctic islands, is now largely submerged, and New Zealand's present terrestrial existence is the product of tectonic activity initiated around 26 Ma. We argue that for the purposes of biogeographical interpretation, New Zealand can be treated as an oceanic island.     

Trans‐equatorial range of a land bird lineage (Aves: Rallidae) from tropical forests to subantarctic grasslands

Despite the capacity for dispersal, range size varies considerably among birds species. Many species have restricted geographic spread, whilst others routinely travel long distances to reach preferred habitat. These alternatives are well expressed amongst the rails (Rallidae) and a varying tendency for movement results in overlapping distribution patterns. Here, we examine the situation of a particular lineage, the Lewinia rails (L. mirifica, L. pectoralis and L. muelleri) that inhabit a very wide spatial and ecological range. Lewinia occurs from the Philippines, north of the equator in Oceania, to Australia and the subantarctic Auckland Islands far to the south. Allopatric distribution and differences in plumage colour result in their treatment as distinct species but our mitochondrial molecular analysis (cyt b and CR) reveals genetic distances of less than < 1%. The genetic and phylogeographical structure in the Lewinia lineage includes shared nuclear sequence alleles and this is consistent with a callibrated multigene phylogeny suggesting trans‐hemispheric dispersal since the middle Pleistocene. Despite this recent history, available morphometric data indicates that the subantarctic population has relatively small wings for its mass, and this implies adaptation away from flight. Lewinia provides a nice example of the way dispersal and adaptation intersect over short time frames to generate diversity.     

Spatial size dimorphism in New Zealand's last endemic raptor,the Kārearea Falco novaeseelandiae,coincides with a narrow sea strait

Although New Zealand's avifauna includes many unusual birds, species‐level diversity within lineages is typically low. There are, however, several instances where different allied forms are recognized in each of the two main islands. Among them is the Kārearea Falco novaeseelandiae, which is the only surviving endemic raptor species in New Zealand. Recent analysis confirms it to be a distinct lineage in the global radiation of this genus and most closely related to the Aplomado Falcon Falco femoralis of South America. We examined body size metrics and neutral genetic markers in Kārearea sampled across New Zealand to assess subspecific variation within the species. We found strong evidence using linear modelling and Bayesian clustering for two distinct sizes within Kārearea, in addition to the recognized sexual dimorphism. The boundary between the size clusters coincides closely with the Cook Strait, a narrow seaway between the two largest islands. However, analysis of mitochondrial sequence data and nuclear microsatellites showed no compelling partitioning at neutral loci. These data suggest adaptive change along a stepped environmental cline. Lineage splitting in Kārearea has either yet to become apparent in the distribution of neutral genetic variation and/or regional adaptation is proceeding despite gene flow.     

Little or no gene flow despite F1 hybrids at two interspecific contact zones

Hybridization can create the selective force that promotes assortative mating but hybridization can also select for increased hybrid fitness. Gene flow resulting from hybridization can increase genetic diversity but also reduce distinctiveness. Thus the formation of hybrids has important implications for long‐term species coexistence. This study compares the interaction between the tree wētā Hemideina thoracica and its two neighboring species; H. crassidens and H. trewicki. We examined the ratio of parent and hybrid forms in natural areas of sympatry. Individuals with intermediate phenotype were confirmed as first generation hybrids using nine independent genetic markers. Evidence of gene flow from successful hybridization was sought from the distribution of morphological and genetic characters. Both species pairs appear to be largely retaining their own identity where they live in sympatry, each with a distinct karyotype. Hemideina thoracica and H. trewicki are probably reproductively isolated, with sterile F₁ hybrids. This species pair shows evidence of niche differences with adult size and timing of maturity differing where Hemideina thoracica is sympatric with H. trewicki. In contrast, evidence of a low level of introgression was detected in phenotypes and genotypes where H. thoracica and H. crassidens are sympatric. We found no evidence of size divergence although color traits in combination with hind tibia spines reliably distinguish the two species. This species pair show a bimodal hybrid zone in the absence of assortative mating and possible sexual exclusion by H. thoracica males in the formation of F₁ hybrids.