Assembly rules operate only in equilibrium communities: Is it true?

Very little is known of how disturbance affects community assembly rules. We examine this in three disturbance states in each of two ski areas on southern New Zealand mountains. Theory suggests that a community will become progressively more spatially organized during recovery from disturbance. Firstly, different patches of the community should become more similar through time, but this was seen in only one of the two areas and even then only examining species presence/absence. Secondly, it has been suggested that spatial autocorrelation will be stronger in less‐disturbed conditions, that is, there will be a stronger pattern of more distant patches being more dissimilar in species composition. This was generally borne out. However, the method indicated more point randomness in less‐disturbed sites. Assembly rules might be seen in species abundances. Previous work has found maximum evenness of abundances in later successional communities, but the pattern here was the opposite: high evenness in the most disturbed communities. The literature suggests that in undisturbed communities the distribution of species abundances (relative abundance distribution) will be general lognormal, and we further argue that the identity of the species across occupying rank positions in that distribution should be more consistent (rank consistency). Both predictions were borne out in one area, but neither in the other. Many workers suggest that niche‐based assembly rules will be stronger in undisturbed communities. However, there was only weak evidence of constancy in species richness. Local species assemblages tended to contain a relatively constant representation from different morphological/taxonomic guilds (guild proportionality) and this was significant in some tests, but contrary to theory this effect occurred mainly in the most disturbed sites. It is concluded that there is only limited truth in the frequent assumption that community structure is stronger in undisturbed, equilibrium communities.     

Vocal Signature in Wild Infant Chimpanzees

A large array of communication signals supports the fission/fusion social organization in chimpanzees, and among them the acoustic channel plays a large part because of their forest habitat. Adult vocalizations convey social and ecological information to their recipients allowing them to obtain cues about an ongoing event from calls only. In contrast to adult vocalizations, information encoded in infant calls had been hardly investigated. Studies mainly focused on vocal development. The present article aims at assessing the acoustic cues that support individual identity coding in infant chimpanzees. By analyzing recordings performed in the wild from seven 3‐year‐old infant chimpanzees, we showed that their calls support a well‐defined individual vocal signature relying on spectral cues. To assess the reliability of the signature across the calls of an individual, we defined two subsets of recordings on the basis of the characteristics of the frequency modulation (whimpers and screams) and showed that both call types present a reliable vocal signature. Early vocal signature may allow the mother and other individuals in the group to identify the infant caller when visual contact is broken. Chimpanzee mothers may have developed abilities to cope with changing vocal signatures while their infant, still vulnerable, gains in independence in close habitat. Am. J. Primatol. 75:324‐332, 2013. © 2012 Wiley Periodicals, Inc.     

Mandipropamid targets the cellulose synthase-like PiCesA3 to inhibit cell wall biosynthesis in the oomycete plant pathogen, Phytophthora infestans

Oomycete plant pathogens cause a wide variety of economically and environmentally important plant diseases. Mandipropamid (MPD) is a carboxylic acid amide (CAA) effective against downy mildews, such as Plasmopara viticola on grapes and potato late blight caused by Phytophthora infestans . Historically, the identification of the mode of action of oomycete-specific control agents has been problematic. Here, we describe how a combination of biochemical and genetic techniques has been utilized to identify the molecular target of MPD in P. infestans . Phytophthora infestans germinating cysts treated with MPD produced swelling symptoms typical of cell wall synthesis inhibitors, and these effects were reversible after washing with H₂O. Uptake studies with ¹⁴C-labelled MPD showed that this oomycete control agent acts on the cell wall and does not enter the cell. Furthermore, ¹⁴C glucose incorporation into cellulose was perturbed in the presence of MPD which, taken together, suggests that the inhibition of cellulose synthesis is the primary effect of MPD. Laboratory mutants, insensitive to MPD, were raised by ethyl methane sulphonate (EMS) mutagenesis, and gene sequence analysis of cellulose synthase genes in these mutants revealed two point mutations in the PiCesA3 gene, known to be involved in cellulose synthesis. Both mutations in the PiCesA3 gene result in a change to the same amino acid (glycine-1105) in the protein. The transformation and expression of a mutated PiCesA3 allele was carried out in a sensitive wild-type isolate to demonstrate that the mutations in PiCesA3 were responsible for the MPD insensitivity phenotype.     

TROPHIC ROLES OF CO-OCCURRING SPECIES OF DRUPA (GASTROPODA: MURICIDAE) AT ENEWETAK ATOLL

Diets in nature differed significantly among three species ofthe gastropod genus Drupa (Muricidae: Thaidinae) on a windward,seaward reef platform at Enewetak Atoll, Marshall Islands. Nereidand eunicid polychaetes and vermetid gastropods were the mostimportant prey organisms. D. morum ate mainly Perinereis, Ceratonereisand eunicids; D. ricinus ate mainly Ceratonereis in protectedsites and Dendropoma near the exposed outer reef edge. Sizeof Drupa was correlated with that of vermetid but not polychaeteprey. The results are compared with data from studies of otherpredators on the same prey species at Enewetak, and with J.D. Taylor's data on the diets of Drupa species elsewhere inthe Indo-Pacific region. ^*Present address: Department of Zoology, University of California,Berkeley, California 94720. (Received 4 February 1989; accepted 6 March 1989)     

A New Method for the Isolation of Etioplasts with Intact Envelopes

Electron micrographs are presented to demonstrate a new methodfor the isolation of etioplasts with intact envelopes developedafter comparing the known methods of isolation including thoseusing zonal centrifugation. This new method employs a columnof Sephadex G-50 (coarse) as one of the separation stages.     

Developmental Changes of Etioplasts in Isolated Suspensions and in situ

A simple model and procedure for assessing the ultrastructuraldevelopment and the degree of desynchronization of a populationof etioplasts is used to illustrate the effect of an improvedmedium for the incubation of suspensions of etioplasts. Themethod also enables an assessment of ultrastructural developmenttaking place in these plastids to be compared with that takingplace within intact tissue over a similar period of time. Forthe first 1–2 h of incubation, the degree of developmentalmost parallels that taking place in vivo; thereafter, developmentwithin suspensions of plastids is slowed down. Similar inversechanges are recorded with respect to the degree of desynchronizationof the plastid populations. Inhibitors are used to identifycritical stages of chloroplast development and the nature ofextra-chloroplastic involvement in the development of plastids,which is evident from these combined experiments, is discussed.